Vassiliki Mpakou

Urinary bladder cancer is a common malignancy, being characterized by substantial patient mortality and management cost. Its high somatic-mutation frequency and molecular heterogeneity usually renders tumors refractory to the applied regimens. Hitherto, methotrexate-vinblastine-adriamycin-cisplatin and gemcitabine-cisplatin represent the backbone of systemic chemotherapy. However, despite the initial chemosensitivity, the majority of treated patients will eventually develop chemoresistance, which severely reduces their survival expectancy. Since chromatin regulation genes are more frequently mutated in muscle-invasive bladder cancer, as compared to other epithelial tumors, targeted therapies against chromatin aberrations in chemoresistant clones may prove beneficial for the disease. "Acetyl-chromatin" homeostasis is regulated by the opposing functions of histone acetyltransferases (HATs) and histone deacetylases (HDACs). The HDAC/SIRT (super-)family contains 18 members, which are divided in five classes, with each family member being differentially expressed in normal urinary bladder tissues. Since a strong association between irregular HDAC expression/activity and tumorigenesis has been previously demonstrated, we herein attempt to review the accumulated published evidences that implicate HDACs/SIRTs as critical regulators in urothelial bladder cancer. Moreover, the most extensively investigated HDAC inhibitors (HDACis) are also analyzed, and the respective clinical trials are also described. Interestingly, it seems that HDACis should be preferably used in drug-combination therapeutic schemes, including radiation.

Mir-17-5p and mir-20a, members of the mir-17-92 family, down-regulate E2F1, which is over-expressed in myelodysplastic syndromes (MDS). Moreover, let-7a down-regulates KRAS, which is aberrantly expressed in MDS. We evaluated the expression of the aforementioned microRNAs in CD34+ cells of 43 MDS patients using real-time PCR and their target proteins (E2F1, MYC, BCL2, CCND1, and KRAS) by Western blot. Mir-17-5p and mir-20a were under expressed in high risk MDS patients, compared to low risk MDS patients. Similarly, let-7a was under expressed in patients with intermediate or high-risk karyotype. Interestingly, there was an inverse correlation between microRNA and the expression levels of their targets. Importantly, mir-17-5p and mir-20a constitute favorable prognostic factors in MDS, since their expression was associated with increased overall survival of MDS patients.

The combination of JAK/STAT and HDAC inhibitors exerted beneficial effects in haematological malignancies, presenting promising therapeutic CTCL targets. We aim to investigate the efficacy of JAK1/2i ruxolitinib in combination with HDACi resminostat in CTCL in vitro.Non-toxic concentrations of ruxolitinib and/or resminostat were administered to MyLa (MF) and SeAx (SS) cells for 24h. Cytotoxicity, cell proliferation and apoptosis were estimated through MTT, BrdU/7AAD and Annexin V/PI assay. Multi-pathway analysis was performed to investigate the effect of JAK1/2i and/or HDACi on JAK/STAT, Akt/mTOR and MAPK signalling pathways.Both drugs and their combination were cytotoxic in MyLa (p<0.05) and in SeAx cell line (p<0.001), inhibited proliferation of MyLa (p<0.001) and SeAx (p<0.001) at 24h, compared to untreated cells. Moreover, combined drug treatment induced apoptosis after 24h (p<0.001) in MyLa, and SeAx (p<0.001). The combination of drugs had a strong synergistic effect with a CI<1. Importantly, the drugs' combination inhibited phosphorylation of STAT3 (p<0.001), Akt (p<0.05), ERK1/2 (p<0.001) and JNK (p<0.001) in MyLa, while it reduced activation of Akt (p<0.05) and JNK (p<0.001) in SeAx.The JAKi/HDACi combination exhibited substantial anti-tumor effects in CTCL cell lines, and may represent a promising novel therapeutic modality for CTCL patients.

In the present study, we describe the features of programmed cell death of the ovarian nurse cells occurring during vitellogenesis of the silkmoth Bombyx mori. At developmental stage 5, the nurse cells occupy one-half of the follicular volume and obtain a rather spherical shape, while the nurse cell nuclei appear large and elongated, forming impressive projections. At the following stage, stage 6, the nurse cells decrease in size and their shape becomes elliptic. The nuclei remain elongated, being also characterized by large lobes. The lobes of the ramified nurse cell nuclei seem to retain the nucleus in the center of the cell during the dumping of the nurse cell cytoplasm into the growing oocyte. At stage 7, membrane enclosed vacuoles can be easily detected into the nurse cells cytoplasm. Ultrastructural analysis and fluorescent microscopy using mono-dansyl-cadaverine staining of these vacuoles also reveal that they represent autolysosomes. Caspase activity is detected during stage 7, as it is demonstrated by using the Red-VAD-FMK staining reagent. At developmental stages 8 and 9, the nurse cells exhibit chromatin condensation, DNA fragmentation and caspase activity. Finally, during the following stage 10, the nuclear remnants are assembled into apoptotic vesicles, which, after being phagocytosed, are observed in the cytoplasm of adjacent follicle cells. We propose that apoptosis and autophagy operate synergistically during vitellogenesis of B. mori, in order to achieve an efficient and rapid clearance of the degenerated nurse cell cluster.

Accumulated data indicate a significant role of T cell dysfunction in the pathogenesis of chronic lymphocytic leukemia. In CLL, regulatory T cells are significantly higher and show lower apoptotic levels compared to healthy donors. We demonstrate that CLL derived CD4+CD25-CD127- and CD4+CD25lowCD127- subpopulations share a common immunophenotypic profile with conventional Tregs and are associated with advanced stage disease. We further provide evidence that the increased number of Tregs contributes indirectly to the proliferation of the CLL clone, by suppressing the proliferation of Teffs which in turn suppress CLL cells. These data are further supported by our observations that CLL derived Tregs appear rather incapable of inducing apoptosis of both normal B cells and CLL cells, in contrast to normal Tregs, suggesting an immunoediting effect of CLL cells on Tregs which negatively affects the functionality of the latter and contributes to the failure of Tregs in CLL to efficiently eliminate the abnormal clone.

Methylation of the human papillomavirus (HPV) DNA has been proposed as a novel biomarker. Here, we correlated the mean methylation level of 12 CpG sites within the L1 gene, to the histological grade of cervical precancer and cancer. We assessed whether HPV L1 gene methylation can predict the presence of high-grade disease at histology in women testing positive for HPV16 genotype.Pyrosequencing was used for DNA methylation quantification and 145 women were recruited.We found that the L1 HPV16 mean methylation (±SD) significantly increased with disease severity (cervical intraepithelial neoplasia [CIN] 3, 17.9% [±7.2] vs CIN2, 11.6% [±6.5], P < .001 or vs CIN1, 9.0% [±3.5], P < .001). Mean methylation was a good predictor of CIN3+ cases; the area under the curve was higher for sites 5611 in the prediction of CIN2+ and higher for position 7145 for CIN3+. The evaluation of different methylation thresholds for the prediction of CIN3+ showed that the optimal balance of sensitivity and specificity (75.7% and 77.5%, respectively) and positive and negative predictive values (74.7% and 78.5%, respectively) was achieved for a methylation of 14.0% with overall accuracy of 76.7%.Elevated methylation level is associated with increased disease severity and has good ability to discriminate HPV16-positive women that have high-grade disease or worse.

It is increasingly recognized that programmed cell death includes not only apoptosis and autophagy, but also other types of nonapoptotic cell death, such as paraptosis, which are all characterized by distinct morphological features. Our findings indicate that all three types of programmed cell death occur in the ovarian nurse cell cluster during late vitellogenesis (formation of the egg yolk) of Bombyx mori (Lepidoptera), whereas middle vitellogenesis is exclusively characterized by the presence of a nonapoptotic type of cell death, known as paraptosis. During middle vitellogenesis, nurse cells exhibit clearly cytoplasmic vacuolization, as revealed by ultrastructural examination performed through conventional light and transmission electron microscopy, while no signs of apoptotic or autophagic features are detectable. Moreover, nurse cells of developmental stages 7, 8 and 9 contain autophagic compartments, as well as apoptotic characteristics, such as condensed chromatin, fragmented DNA and activated caspases, as revealed by in vitro assays. We propose that paraptosis precedes both apoptosis and autophagy during vitellogenesis, since its initial activation is detectable during middle vitellogenesis, whereas no apoptotic nor autophagic features are observed. In contrast, at the late stages of Bombyx mori oogenesis, paraptosis, autophagy and apoptosis operate synergistically, resulting in a more efficient elimination of the degenerated nurse cells.

Programmed cell death (PCD) is an evolutionary conserved and genetically regulated form of cell death, in which the cell plays an active role in its own demise. It is widely recognized that PCD can be morphologically classified into three major types: type I, known as apoptosis, type II, called autophagy, and type III, specified as cytoplasmic cell death. So far, PCD has been morphologically analyzed in certain model insect species of the meroistic polytrophic ovary-type, but has never been examined before in insects carrying meroistic telotrophic ovaries. In the present study, we attempted to thoroughly describe the three different types (I, II and III) of PCD occurring during oogenesis in the meroistic telotrophic ovary of the Coleoptera species Adalia bipunctata, at different developmental ages of the adult female insects. We reveal that in the ladybird beetle A. bipunctata, the ovarian tropharia undergo age-dependent forms of apoptotic, autophagic and cytoplasmic (paraptotic-like) cell death, which seem to operate in a rather synergistic fashion, in accordance with previous observations in Diptera and Lepidoptera species. Furthermore, we herein demonstrate the occurrence of morphogenetically abnormal ovarioles in A. bipunctata female insects. These atretic ovarioles collapse and die through a PCD-mediated process that is characterized by the combined activation of all three types of PCD. Conclusively, the distinct cell death programs (I, II and III) specifically engaged during oogenesis of A. bipunctata provide strong evidence for the structural and functional conserved nature of PCD during insect evolution among meroistic telotrophic and meroistic polytrophic ovary-type insects.

Activating mutations of the c-kit gene are frequently found in CBF (core binding factor) leukemias. We evaluated the effect of tyrosine kinase inhibitor dasatinib in leukemic cell lines bearing or not c-kit mutations. Our data demonstrate that in the AML Kasumi-1 cell line, bearing the N822K c-kit mutation, dasatinib is a potent suppressor of c-kit and Src kinase activity and inhibits the phosphorylation of their downstream target AKT, possibly through the Src-mediated VEGF/VEGFR receptor type 2 pathway. Dasatinib also effectively blocks proliferation and induces apoptosis through caspase-3 activation in Kasumi-1 cells. These data further encourage the integration of dasatinib in the treatment of CBF AML with c-kit mutations in the context of clinical trials, which are eagerly anticipated.

Drosophila chorion represents a remarkable model system for the in vivo study of complex extracellular-matrix architectures. For its organization and structure, s38 protein is considered as a component of major importance, since it is synthesized and secreted during early choriogenesis. However, there is no evidence that proves its essential, or redundant, role in chorion biogenesis. Hence, we show that targeted downregulation of s38 protein, specifically in the ovarian follicle-cell compartment, via employment of an RNAi-mediated strategy, causes generation of diverse dysmorphic phenotypes, regarding eggshell's regionally and radially specialized structures. Downregulation of s38 protein severely impairs fly's fertility and is unable to be compensated by the s36 homologous family member, thus unveiling s38 protein's essential contribution to chorion's assembly and function. Altogether, s38 acts as a key skeletal protein being critically implicated in the patterning establishment of a highly structured tripartite endochorion. Furthermore, it seems that s38 loss may sensitize choriogenesis to stochastic variation in its coordination and timing.

Drosophila melanogaster ovary serves as an attractive model system for the investigation of the cell cycle, death, signaling, migration, differentiation, development and stemness. By employing the 3750/+ heterozygote fly strain that carries specific functions in the follicle cell compartment, and a reliable control in GAL4/UAS-based transgenic technology, we herein characterized the protein-expression profiling of D. melanogaster ovary by applying high-resolution proteomic tools and bioinformatics programs.Whole-cell total protein extracts derived from 3750/+ fly ovaries were prepared under highly denaturing conditions and after tryptic digestion, their cognate peptides were processed to liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) analysis in a high-resolution LTQ Orbitrap Elite instrument. Obtained protein data were analyzed through use of UniProt, DAVID, KEGG and PANTHER bioinformatics platforms.The 7,583 unique peptides identified show that fly ovary contains at least 2,103 single proteins, which are distributed to all egg chamber compartments, in cytoplasm, membrane and nucleus, compartmentalized into major cellular organelles, and categorized into critical macromolecular assemblies. Among the recognized specific functions, nucleic acid binding, hydrolase, oxidoreductase, transporter and vesicle-mediated trafficking activities were the most prevalent. Determinants implicated in cellular metabolism and gene expression are represented by ~41% and ~17% of the ovarian proteome, respectively. Surprisingly, several proteins were found engaged in aging, immune response and neurogenesis. All major signaling pathways were detected, while apoptotic and non-apoptotic cell death programs were also identified. Remarkably, proteins involved in tumor formation, neurodegenerative and inflammatory diseases were also recognized. The successful remodeling of the proteasome and nearly complete molecular reconstruction of the citrate cycle and fatty acid degradation pathways demonstrate the efficacy, accuracy and fidelity of our combined proteomics/bioinformatics approach.Global proteomic characterization of D. melanogaster ovary allows the discovery of novel regulators and pathways, and provides a systemic view of networks that govern ovarian pathophysiology and embryonic development in fly species as well in humans.

Drosophila chorion represents a model biological system for the in vivo study of gene activity, epithelial development, extracellular-matrix assembly and morphogenetic-patterning control. It is produced during the late stages of oogenesis by epithelial follicle cells and develops into a highly organized multi-layered structure that exhibits regional specialization and radial complexity. Among the six major proteins involved in chorion's formation, the s36 and s38 ones are synthesized first and regulated in a cell type-specific and developmental stage-dependent manner. In our study, an RNAi-mediated silencing of s36 chorionic-gene expression specifically in the follicle-cell compartment of Drosophila ovary unearths the essential, and far from redundant, role of s36 protein in patterning establishment of chorion's regional specialization and radial complexity. Without perturbing the developmental courses of follicle- and nurse-cell clusters, the absence of s36 not only promotes chorion's fragility but also induces severe structural irregularities on chorion's surface and entirely impairs fly's fertility. Moreover, we herein unveil a novel function of s36 chorionic protein in the regulation of number and morphogenetic integrity of dorsal appendages in follicles sporadically undergoing aged fly-dependent stress.

In the present study, we demonstrate the existence of two distinct apoptotic patterns in nurse cells during Ceratitis capitata oogenesis. One is developmentally regulated and normally occurs during stages 12 and 13, and the other is stage specific and is sporadically observed during stages 7 and 8. The pre-apoptotic manifestation of the first pattern begins at stage 11 and is characterized by the formation of actin bundles. Subsequently, at stages 12 and 13, the nurse cell nuclei exhibit condensed chromatin and contain fragmented DNA, as revealed by TUNEL assay. The apoptotic nurse cell remnants are phagocytosed by the neighboring follicle cells at the end of oogenesis during stages 13 and 14. In the second apoptotic pattern, which occurs sporadically during stages 7 and 8, the nurse cells degenerate and are phagocytosed by the follicular epithelium that contains apoptotic cell bodies. The data presented herein, compared to previous reported results in Drosophila melanogaster and Dacus oleae (Nezis et al., 2000, Nezis et al., 2001), strongly suggest that nurse cell apoptosis is a developmentally regulated and phylogenetically conserved mechanism in higher Dipteran. They also suggest that, the sporadic apoptotic pattern consists of a possible protective mechanism throughout oogenesis when damaged or abnormal egg chambers, are eliminated before they reach maturity.

Ubiquitin/proteasome-mediated degradation of eukaryotic proteins is critically implicated in a number of signalling pathways and cellular processes. To specifically impair proteasome activities, in vitro developing Drosophila melanogaster egg chambers were exposed to the MG132 or epoxomicin proteasome inhibitors, while a GAL4/UAS binary genetic system was employed to generate double transgenic flies overexpressing β2 and β6 conditional mutant proteasome subunits in a cell type-specific manner. MG132 and epoxomicin administration resulted in severe deregulation of in vitro developing egg chambers, which was tightly associated with precocious induction of nurse cell-specific apoptotic and autophagic death programmes, featured by actin cytoskeleton disorganization, nuclear chromatin condensation, DRICE caspase activation and autophagosome accumulation. In vivo targeted overexpression of β2 and β6 conditional mutants, specifically in the nurse cell compartment, led to a notable up-regulation of sporadic apoptosis potency during early and mid-oogenesis ‘checkpoints’, thus reasonably justifying the observed reduction in eclosion efficiency. Furthermore, in response to the intracellular abundance of β2 and β6 conditional mutant forms, specifically in numerous tissues of third instar larval stage, the developmental course was arrested, and lethal phenotypes were obtained at this particular embryonic period, with the double transgenic heterozygote embryos being unable to further proceed to complete maturation to adult flies. Our data demonstrate that physiological proteasome function is required to ensure normal oogenesis and embryogenesis in D. melanogaster, since targeted and cell type-dependent proteasome inactivation initiates developmentally deregulated apoptotic and autophagic mechanisms.

Proteasome-dependent and autophagy-mediated degradation of eukaryotic cellular proteins represent the two major proteostatic mechanisms that are critically implicated in a number of signaling pathways and cellular processes. Deregulation of functions engaged in protein elimination frequently leads to development of morbid states and diseases. In this context, and through the utilization of GAL4/UAS genetic tool, we herein examined the in vivo contribution of proteasome and autophagy systems in Drosophila eye and wing morphogenesis. By exploiting the ability of GAL4-ninaE. GMR and P{GawB}Bx(MS1096) genetic drivers to be strongly and preferentially expressed in the eye and wing discs, respectively, we proved that proteasomal integrity and ubiquitination proficiency essentially control fly's eye and wing development. Indeed, subunit- and regulator-specific patterns of severe organ dysmorphia were obtained after the RNAi-induced downregulation of critical proteasome components (Rpn1, Rpn2, α5, β5 and β6) or distinct protein-ubiquitin conjugators (UbcD6, but not UbcD1 and UbcD4). Proteasome deficient eyes presented with either rough phenotypes or strongly dysmorphic shapes, while transgenic mutant wings were severely folded and carried blistered structures together with loss of vein differentiation. Moreover, transgenic fly eyes overexpressing the UBP2-yeast deubiquitinase enzyme were characterized by an eyeless-like phenotype. Therefore, the proteasome/ubiquitin proteolytic activities are undoubtedly required for the normal course of eye and wing development. In contrast, the RNAi-mediated downregulation of critical Atg (1, 4, 7, 9 and 18) autophagic proteins revealed their non-essential, or redundant, functional roles in Drosophila eye and wing formation under physiological growth conditions, since their reduced expression levels could only marginally disturb wing's, but not eye's, morphogenetic organization and architecture. However, Atg9 proved indispensable for the maintenance of structural integrity of adult wings in aged flies. In toto, our findings clearly demonstrate the gene-specific fundamental contribution of proteasome, but not autophagy, in invertebrate eye and wing organ development.

Mycosis fungoides (MF) and its leukemic variant Sézary syndrome (SS) comprise the majority of CTCL, a heterogenous group of non-Hodgkins lymphomas involving the skin. The CTCL's resistance to chemotherapy and the lack of full understanding of their pathogenesis request further investigation. With the view of a more targeted therapy, we evaluated in vitro the effectiveness of bortezomib and methotrexate, as well as their combination in CTCL cell lines, regarding apoptosis induction. Our data are of clinical value and indicate that the bortezomib/methotrexate combinational therapy has an inferior impact on the apoptosis of CTCL compared to monotherapy, with bortezomib presenting as the most efficient treatment option for SS and methotrexate for MF. Using PCR arrays technology, we also investigated the alterations in the expression profile of genes related to DNA repair pathways in CTCL cell lines after treatment with bortezomib or methotrexate. We found that both agents, but mostly bortezomib, significantly deregulate a large number of genes in SS and MF cell lines, suggesting another pathway through which these agents could induce apoptosis in CTCL. Finally, we show that SS and MF respond differently to treatment, verifying their distinct nature and further emphasizing the need for discrete treatment approaches.

Abstract Drosophila brain has emerged as a powerful model system for the investigation of genes being related to neurological pathologies. To map the proteomic landscape of fly brain, in a high-resolution scale, we herein employed a nano liquid chromatography-tandem mass spectrometry technology, and high-content catalogues of 7,663 unique peptides and 2,335 single proteins were generated. Protein-data processing, through UniProt, DAVID, KEGG and PANTHER bioinformatics subroutines, led to fly brain-protein classification, according to sub-cellular topology, molecular function, implication in signaling and contribution to neuronal diseases. Given the importance of Ubiquitin Proteasome System (UPS) in neuropathologies and by using the almost completely reassembled UPS, we genetically targeted genes encoding components of the ubiquitination-dependent protein-degradation machinery. This analysis showed that driving RNAi toward proteasome components and regulators, using the GAL4-elav.L driver, resulted in changes to longevity and climbing-activity patterns during aging. Our proteomic map is expected to advance the existing knowledge regarding brain biology in animal species of major translational-research value and economical interest.

In the present study, the ability of the proteasome inhibitor bortezomib (BZ), an oxidative stress‑inducing agent, to sensitize acute myeloid leukemia (AML) cells to decitabine (Dacogen^®, DAC; a DNA methyltransferase inhibitor), in terms of cell viability and differentiation, was investigated. Kasumi‑1 AML (M2) cells were treated with low‑dose DAC (10, 50, 100, 200 or 400 nΜ), with or without BZ (10 nM). Apoptosis and the cell cycle were evaluated after 24 h of treatment through fluorescence‑assisted cell sorting (FACS) with Annexin V/propidium iodide and DAPI staining, respectively. The expression levels of CD193, CD11b, CD13, CD14, CD15, CD16 and CD117 surface differentiation markers were evaluated by FACS after 6 days of treatment. The results indicated significant alterations in cell death and cell cycle phases in Kasumi‑1 cells following DAC and BZ combination treatment compared to untreated cells and cells with single treatments. Low‑dose DAC/BZ combinations significantly enhanced apoptosis and decreased the population of live Kasumi‑1 cells, with 100 and 200 nM of DAC and 10 nM BZ appearing to have the most potent synergistic effect according to a combination index. Furthermore, cell cycle profiling revealed that DAC/BZ treatment synergistically led to G0/G1‑ and G2/M‑phase arrest. By contrast, DAC appeared to promote monocytic and granulocytic differentiation of Kasumi‑1 cells more effectively alone than in combination with BZ. BZ acted synergistically with low‑dose DAC <em>in vitro</em>, leading to enhanced apoptosis and G0/G1‑ and G2/M‑phase arrest in AML cells, hence prohibiting either DNA synthesis or mitosis. Although further <em>in vivo</em> investigation is necessary, these results provide a strong rationale for the implementation of a combination treatment with DAC and bortezomib in AML therapy, followed by DAC alone, which may achieve better clinical responses and possibly partially overcome the frequently encountered DAC resistance of patients with AML.

This paper presents data associated with the research article entitled "Targeted downregulation of s36 protein unearths its cardinal role in chorion biogenesis and architecture during Drosophila melanogaster oogenesis" [1]. Drosophila chorion is produced by epithelial follicle cells and one of its functional serving role is egg fertilization through the micropyle, a specialized narrow channel at the anterior tip of the egg [2]. Sperm entry during fertilization is necessary for the egg to complete meiosis [3]. D. melanogaster flies being characterized by severe downregulation of the s36 chorionic protein, specifically in the follicle-cell compartment of their ovary, appear with impaired fly fertility (Velentzas et al., 2016) [1]. In an effort to further investigate whether the observed infertility in the s36-targeted flies derives from a fertilization failure, such as the inability of sperm to pass through egg׳s micropyle, we mated females carrying s36-depleted ovaries with males expressing the GFP protein either in their sperm tails, or in both their sperm tails and sperm heads.

Abstract 5‐azacytidine (5‐AZA) is considered the standard of care for patients with high‐risk myelodysplastic syndromes (MDS) and patients with acute myeloid leukemia (AML) not candidate for intensive chemotherapy. However, even after an initial favorable response, almost all patients relapse, with the exact mechanisms underlying primary or secondary 5‐AZA resistance remaining largely unknown. Several reports have previously demonstrated the significance of hypoxia in the regulation of both physiological and malignant hematopoiesis. In MDS, high hypoxia inducible factor 1α (Hif‐1α) expression has been correlated with poor overall survival and disease progression, while its involvement in the disease's pathogenesis was recently reported. We herein investigated the possible association of the Hif‐1α signaling pathway with response to 5‐AZA therapy in MDS/AML patients. Our data demonstrated that 5‐AZA‐responders present with higher Hif‐1α mRNA and protein expression compared to 5‐AZA‐non‐responders/stable disease patients, before the initiation of therapy, while, interestingly, no significant differences in Hif‐1α mRNA expression at the 6‐month follow‐up were observed. Moreover, we found that 5‐AZA‐responders exhibited elevated mRNA levels of the Hif‐1α downstream targets lactate dehydrogenase a (LDHa) and BCL2 interacting protein 3 like (BNIP3L), a further indication of an overactivated Hif‐1a signaling pathway in these patients. Kaplan–Meier survival analysis revealed a significant correlation between high Hif‐1α mRNA expression and better survival rates, while logistic regression analysis showed that Hif‐1α mRNA expression is an independent predictor of response to 5‐AZA therapy. From the clinical point of view, apart from proposing Hif‐1α mRNA expression as a significant predictive factor for response to 5‐AZA, our data offer new perspectives on MDS combinational therapies, suggesting a potential synergistic activity of 5‐AZA and Hif‐1α inducers, such as propyl hydroxylases inhibitors (PHDi).

Abstract Introduction: T regulatory cells are immunosuppressive cells considered to play an important role in cancer biology and autoimmunity by suppressing host immune response and autoreactive lymphocytes respectively. Several studies reveal that Treg cells act by suppressing anti-tumor immune response, through the targeting of other immune cells, such as T cells, B cells and dendritic cells. Accumulated data indicate a significant role of T cell dysfunction in the pathogenesis of CLL. Aims: The scope of this study is the analysis of numerical and functional abnormalities of Tregs in B-CLL with the view to elucidate their role in the pathogenesis of the disease. Methods: Treg cells derived from 44 untreated B-CLL patients with a median age 62 and 17 healthy donors were analyzed by Flow cytometry, using the following antibodies: CD45Ro-FITC/CD45RA-PE/CD4-ECD/CD25-PC5/CD127-PC7, CD1a-FITC/CD137-PE/CD4-ECD/CD25-PC5/CD127-PC7, CD95-FITC/cyCD152-PE/CD4-ECD/CD25-PC5/CD127-PC7, beads/FoxP3-PE/CD4-ECD/CD25-PC5/CD127-PC7, Annexin V-FITC/CD4-ECD/CD25-PC5/CD127-PC7. For the functional analysis, peripheral blood was obtained from 20 patients with B-CLL. Mononuclear cells were isolated using Ficoll-Paque gradient centrifugation. CD4+ CD25+ (Treg cells), CD4+ CD25- (T effectοr cells, Teff), CD5+ CD19+ (B-CLL) and CD5- CD19+ (Normal B, NB) cells were separated using magnetic antibody cell sorting. To test the functionality of the assayed Tregs, the isolated cell populations were cultured in a 96-well plate (Tregs, Teff, B-CLL cells, NB cells, B-CLL cells: Tregs in 1:20 ratio, B-CLL cells: Teff in 1:20 ratio, NB cells: Tregs in 1:20 ratio, NB cells: Teff in 1:20 ratio) and their proliferative capacity was measured using the BrdU assay. To further analyze the functional role of Tregs, peripheral blood was obtained from 22 patients with CLL and 22 healthy donors. Mononuclear cells were isolated using Ficoll-Paque gradient centrifugation. CD4+ CD25+ CD127dim/- (Treg cells), CD5+ CD19+ (B-CLL) and CD5- CD19+ (Normal B, NB) cells were separated using magnetic antibody cell sorting and were co-cultured in a 96-well plate in a 1:10 ratio. The apoptosis of B cells was determined by the Annexin V/PI method. Results: FACS analysis of the Treg cells resulted at the following observations: The Treg absolute cell number (cells/μL), estimated either as the number of CD4+ CD25+ CD127- cells or as the number of CD4+ CD25+ FoxP3+ cells, was statistically significantly higher in patients' samples than in controls (CD127- 21.65 vs 7.35, p=0.001; FoxP3+ 20.42 vs 6.5, p= 0.001). Annexin V expression in Treg cells from BCLL patients was significantly lower compared to controls (3.626 vs 38.615, p=0.003). The functional analysis of Treg cells through BrdU assay indicated that CLL Tregs were able to suppress the proliferation of Teff cells (p=0.002) and that Teff cells were in turn able to significantly suppress the proliferation of B-CLL cells (p=0.05). Moreover, FACS analysis through Annexin V/PI method indicated that Treg CLL cells significantly decrease the apoptosis rate of NB cells after their co-culturing, compared to NB cells (p&lt;0,02). On the contrary, healthy donors derived Treg cells significantly increase the apoptosis of B-CLL cells after their co-culturing, compared to B-CLL cells (p&lt;0.025). Interestingly, no significant alterations were observed after culturing NB cells with Tregs from healthy donors and B-CLL cells with Treg CLL cells. Conclusions: In CLL patients, Treg cells are significantly higher and present with lower apoptotic levels compared to healthy donors. The functional analysis indicates that T effector cells suppress the proliferation of B-CLL cells and T effector cells are suppressed by Tregs indicating that the increased number of Tregs observed in CLL contributes indirectly to the proliferation of the CLL clone. These data are further supported by our observations that CLL derived Treg cells appear rather incapable of inducing apoptosis of both NB cells and B-CLL cells, in contrast to normal Tregs, suggesting an immunoediting effect of B-CLL cells on Tregs which negatively affects the functionality of the latter. Therefore, Treg cells in CLL do not efficiently eliminate the abnormal clone and play an important role in the pathogenesis of the disease. The molecular underlying mechanisms need to be further elucidated. Disclosures No relevant conflicts of interest to declare.

Abstract Introduction: Cutaneous T-cell lymphomas (CTCL) represent a heterogeneous group of extranodal non-Hodgkin lymphomas, derived from skin-homing mature T-cells. Mycosis fungoides (MF) and Sézary syndrome (SS) are the commonest types and together comprise 54% of all CTCL. MF evolves from patches to infiltrated plaques and eventually tumors. SS is a lymphoma-leukemia syndrome characterized by erythroderma and the presence of a malignant T-cell clone in the peripheral blood and the skin. At present, no curative treatment for CTCL is available. Therefore current CTCL research efforts are focused on elucidating the molecular mechanisms of the disease’s pathogenesis and on identifying new pharmacological targets. Several drugs have shown potentially significant activity either alone or in combination with conventional agents. Their effectiveness and their mechanisms of action comprise a current research challenge for the improvement of CTCL therapy. The aim of this study was to investigate the possible alterations in the gene expression profile (focusing on DNA Damage Signaling and DNA Repair pathways) and cell death in CTCL cell lines after treatment with two chemotherapeutic agents, Bortezomib and Methotrexate. Methods: Three CTCL cell lines were used. MyLa, (MF), SeAx and Hut-78 (both SS). Cells were cultured in RPMI 1640 and were treated with either Bortezomib (10nmol/L) or Methotrexate (10μM) for 24h. Apoptosis was determined by flow cytometry using the Annexin V/PI method. Gene expression profiling following PCR arrays analysis was performed after total RNA extraction and purification from untreated and drug-treated cells. All RNA samples’ amplification, labeling and hybridization to RT2 Profiler PCR Arrays (DNA Damage Signaling and DNA Repair PCR array) (QIAGEN) were performed according to the manufacturer’s instructions. All data were analyzed using the appropriate RT2 Profiler PCR Array data analysis tool. Results: Hut-78, Seax and Myla cells responded with statistically significant enhanced apoptosis when treated for 24h with bortezomib, compared to untreated cells, while Methotrexate led to a rather moderate increase of apoptosis in Hut-78 and Seax cells and did not affect the apoptosis of Myla cells. Microarrays analysis after bortezomib treatment revealed a great effect in the expression profile of genes involved in almost all DNA repair pathways tested, in all three cell lines, with Hut-78 being affected the most. Specifically, in all cell lines, there was a significant down-regulation of a large number of genes involved in the Double Strand Breaks DNA Repair mechanism, (i.e. BRCA1, BRCA2, RAD50, RAD51, RAD51C, XRCC2, XRCC3, XRCC4, XRCC5 and XRCC6) as well as of genes involved in the Mismatch Repair pathway (i.e. MLH1, MLH3, MSH2, MSH5, MSH6) and the Nucleotide Excision Repair mechanism (i.e. DDB2, LIG1 and RAD23A), compared to untreated cells. On the contrary, bortezomib had a small effect on Base Excision repair mechanism, mostly downregulating the expression of XRCC1 gene in Hut-78 and Myla cells. Methotrexate treatment also led to a significant down-regulation of genes involved in the DSB (RAD50, XRCC4, XRCC6), MMR (MSH4) and NER (CDK7, RAD23A) repair mechanisms in Hut-78 cells but had a rather much more moderate effect on the expression profile of Seax and Myla cells, where fewer genes were affected. Conclusions: Our data clearly demonstrate a differential effect of bortezomib and methotrexate in terms of apoptosis induction on CTCL cells with bortezomib inducing apoptosis of both MF and SS derived cell lines and methotrexate being rather inactive on SS derived cells. We showed that both drugs, but mostly bortezomib significantly down-regulate a large number of genes involved in the DSB, MMR and NER mechanisms, suggesting a possible mechanism, among probably others, for the enhanced sensitivity to apoptosis of SS and MF cell lines after treatment. Bortezomib’s significant effect could be easily understood, since it is a well known proteasome inhibitor and has been previously related to inhibition of NF-kB and accumulation of pro-apoptotic proteins, while it has also been reported that cancer cells are more sensitive to proteasome inhibition than normal cells. Although these results need to be further confirmed, they appear very encouraging for understanding the mechanisms of action of these drugs in CTCL with the view to ameliorate their use in clinical practice. Disclosures No relevant conflicts of interest to declare.

Abstract Introduction T regulatory cells are immunosuppressive cells, which are considered to play an important role in the regulation of immune response to cancer, by restraining autoreactive lymphocytes. Several studies, mostly in solid tumors, revealed that the number of Treg cells increases as the disease progresses and that Treg cells act by suppressing anti-tumor immune response, through the targeting of other immune cells, such as T cells, B cells and dendritic cells. Chronic lymphocytic leukemia (CLL) is a lymphoid malignancy, characterized by both, immunodeficiency and autoimmune disorders. Accumulated data indicate the role of T cells in the pathogenesis and development of CLL and reveal an increased number of Treg cells in CLL patients. The scope of this study is the analysis of the functional role of Tregs derived from the peripheral blood of CLL patients, mainly on B-CLL cells, and its correlation with well known prognostic factors. Methods Treg cells derived from mononuclear cells of 28 untreated B-cell CLL patients with a median age 62 (44-88) and 17 healthy donors were analyzed through Flow cytometry. Patients were classified according to Rai classification as Rai I:19, Rai II:4, Rai III:5 and according to Binet as Binet A: 24, Binet B:3 and Binet C:1. The following antibodies were used for the fluorescence-activated cell sorter (FACS) analysis: 1. CD45Ro-FITC/CD45RA-PE/CD4-ECD/CD25-PC5/CD127-PC7 2. CD1a-FITC/CD137-PE/CD4-ECD/CD25-PC5/CD127-PC7 3. CD95-FITC/cyCD152-PE/CD4-ECD/CD25-PC5/CD127-PC7 4. beads/FoxP3-PE/CD4-ECD/CD25-PC5/CD127-PC7 5. Annexin V-FITC/CD4-ECD/CD25-PC5/CD127-PC7 Moreover, peripheral blood was obtained from 15 patients with B-cell CLL. Mononuclear cells were isolated using Ficoll-Paque gradient centrifugation. CD4+CD25+ (Treg cells), CD4+CD25- (T effectοr cells, Teff), CD5+CD19+ (B-CLL) and CD5+CD19- (Normal B, NB) cells were separated using magnetic antibody cell sorting. To test the functionality of the assayed Tregs, the isolated cell populations were cultured in a 96-well plate (Tregs, Teff, B-CLL, NB cells, Tregs:Teff in a 4:1 ratio, B-cll:Tregs in 1:20 ratio, B-cll:Teff in 1:20 ratio, NB cells:Tregs in 1:20 ratio, NB cells:Teff in 1:20 ratio) and their proliferative capacity was measured using the BrdU assay. Results FACS analysis of the Treg cells resulted at the following observations: (1) The co-expression of the CD45RA-CD45RO markers was significantly higher in patients’ samples than in controls (p=0.047). (2) No significant differences were observed between patients and controls, regarding the expression of the CD1α marker, as well as the expression of CD95 and CD152 markers. (3) The Treg absolute cell number (cells/μL), estimated either as the number of CD4+ CD25+ CD127- cells or as the number of CD4+ CD25+ FoxP3+ cells, was statistically significantly higher in patients’ samples than in controls (CD127- p=0.047, FoxP3+ p= 0.036). (4) Annexin V expression in Treg cells from B- CLL patients was significantly lower compared to controls (p=0.027). Following the purification and culturing of T and B cells from B-cell CLL patients’ samples, functional analysis of the different cell populations was performed using the BrdU proliferation assay. We observed that Tregs were able to significantly suppress the proliferation of the Teff cells (p=0.002). After the co-culturing of NB cells (CD5+CD19-)and Tregs (CD4+CD25+) we found that NB cells seemed to significantly increase the proliferation of Treg cells, compared to the proliferation capacity of the Tregs when cultured alone (p=0.047). Moreover, we observed that Teff (CD4+CD25-) were able to significantly suppress the proliferation of B-CLL cells (CD5+CD19+), when co-cultured (B-CLL: Teff, 1:20 ratio) (p=0.05). Conclusions In B-cell CLL patients, Treg cells are significantly higher and present with lower apoptotic levels compared to healthy donors’ samples. The functional analysis of Treg cells indicates that they can effectively suppress the proliferation of T effector cells. Moreover, T effector cells seem to suppress the proliferation of B-CLL cells, while NB cells increase the proliferation of Treg cells. These observations could probably indicate that at the early stages of the disease, where NB cells are more aberrant, Treg cells’ activity is induced, leading to Teff cells’ suppression and therefore, to an indirect induction of B-CLL cells’ proliferation. Disclosures: No relevant conflicts of interest to declare.

Introduction : Acute myeloid leukemia (AML) is a heterogeneous clonal hematopoietic neoplasm characterized by maturation arrest in the myeloid lineage. The standard of care regimen of induction for AML patients is an anthracycline and cytarabine combination, followed by consolidation therapy. Nevertheless, relapse still remains a major hurdle for successful AML chemotherapy and alternative treatment strategies are much needed. Epigenome-modifying drugs, such as decitabine (D), a DNA methyltransferase inhibitor (DMTi), have shown promise as therapeutics for AML in low doses, while higher doses are associated with cellular differentiation and cytotoxicity. On the other hand, oxidative stress inducers have been strongly implicated in the targeting of LSCs, since increased oxidation is associated with reduced self-renewal, which in turn leads to either differentiation or death of haemopoietic cells. Nevertheless, the induction of oxidative stress alone is not sufficient for AML treatment. Aims: Since only approximately 50% of patients treated with DMTis show a hematological improvement (HI) or better, and few alternative treatments exist for patients who fail to respond, the aim of this study is to investigate the possible reversal of decitabine resistance phenotype in AML, in terms of apoptosis and cell cycle profiling, by the combination of decitabine with oxidative stress inducing agents, such as the proteasome inhibitor bortezomib (BZ). Methods : The AML Kasumi-1 cells, carrying the t(8;21) and the KIT mutation N822, were cultured in RPMI 1640, supplemented with 20% FBS, and incubated in 5% CO 2 at 37°C. Cells were treated with low-dose decitabine (10nΜ, 50nΜ, 100nM, 200nM and 400nΜ), with or without bortezomib (10nM) for 24h. Flow cytometry was used for apoptosis (Annexin V/PI staining) and cell cycle profiling (DAPI staining). One-way Anova and LSD/ Bonferroni methods were applied for the statistical analysis of the results. Results : Our data indicate significant alterations in cell death and cell cycle stages in Kasumi-1 cells following D and BZ combination treatment compared to the control (untreated cells) and single treatments. Apoptosis was statistically significantly increased compared to control (15,15%) after only 100nM and 400nM of single D treatment (27,2% and 28,25%, p=0.037 and p=0.026, respectively) and after D/BZ treatment for all D concentrations tested [31,5%, 33,4%, 54,65%, 47,1% and 55,55%, from lower to higher concentration, with p=0.008 and p=0.004 for 10nM and 50nM respectively, and p Conclusions : Our data indicate that the addition of bortezomib -a proteasome inhibitor which, among others, is capable of inducing oxidative stress- to low-dose decitabine significantly enhances apoptosis and decreases live cell population of Kasumi-1, with the combinations of 100nM and 200nM of D with BZ appearing as the most successful ones. Moreover, cell cycle profiling revealed that D/BZ treatment synergistically leads to G1 and G2 arrest, hence prohibiting cells to either synthesize DNA (S phase) or proceed to mitosis. Although these observations need to be further investigated at a molecular level, they appear very encouraging for better understanding the mechanisms underlying primary resistance to decitabine and offer new directions for a much needed, more successful epigenetic therapy in AML. Disclosures No relevant conflicts of interest to declare.

Background: Acute myeloid leukemia (AML) is a life-threatening malignant myeloid disorder with poor prognosis. Response to induction treatment determines long-term prognosis; however, mechanisms underlying response have not been thoroughly investigated. DNA damage and repair mechanisms influence not only the genetic predisposition to leukemia but are also very important for refractoriness to treatment. Aims: The aim of this study was to investigate the possible alterations in the gene expression profile of DNA damage signaling pathways in two leukemic cell lines following their exposure to chemotherapeutic agents, namely, idarubicin and cytarabine, and verify the findings in AML patient samples at diagnosis before the onset of chemotherapy. Methods: Cell lines Kasumi-1 with the t(8;21) and MV4-11 (biphenotypic B-myelomonocytic leukemia) were exposed either to idarubicin (0.1μΜ) for 6h or cytarabine (1μΜ) for 48h. Dead cells were eliminated from drug-treated cells using an appropriate commercial kit. Gene expression profiling through PCR arrays analysis (RT2 Profiler, Qiagen) was performed in triplicate after RNA extraction from untreated, chemotherapy-treated and live cells following chemotherapy exposure. Human DNA damage signaling pathway-related gene expression was evaluated and analyzed through the RT2 Profiler PCR Array data analysis tool. Moreover, mononuclear cells were isolated from bone marrow of lymphoma patients, used as controls, and from AML patients at diagnosis who subsequently received chemotherapy with the 7 + 3 regiment. Response to first-line chemotherapy was recorded. Total RNA was isolated (RNeasy plus Mini Kit, Qiagen) and quantified and cDNA was synthesized. Relative expression of genes of interest was quantified using SYBR® Green-based real-time RT-PCR (QuantiTect® Primer Assay, Qiagen). Statistics were performed using linear regression. Results: The following genes were over two-fold up-regulated in live cells from leukemic cell lines after treatment with either agent: PPP1R15A and CDKN1A in both cell lines, GADD45A and GADD45G in live MV4-11 cells and EXO1 in live Kasumi cells. These genes were selected for relative quantification; 25 control samples and 38 AML samples (28 responders and 10 non-responders to treatment) were evaluated. GADD45A in AML compared to controls was found 2-fold up-regulated in treatment responders (ns) and 9-fold up-regulated in non-responders [p=0.01]. In addition, GADD45A was overexpressed in non-responders compared to responders [p=0.02]. PPP1R15A in AML compared to controls was 12-fold up-regulated in responders [p=0.001] and 16-fold up-regulated in non-responders [p=0.001]. (Figure 1) Image:Summary/Conclusion: GADD45A controls the balance between apoptosis and autophagy via the p38 and JNK/MAPK pathways and PPP1R15A participates in growth arrest and apoptosis in response to DNA damage by attenuating the translational elongation of key transcription factors. Both genes are likely to play an important role in the pathogenesis of AML. Furthermore, GADD45A overexpression appears to be related with resistance to induction treatment, which may have significant prognostic and therapeutic implications.

Introduction: Acute Myeloid Leukemia (AML) is a life-threatening myeloid malignancy with poor prognosis. Response to induction treatment determines long-term prognosis; however, mechanisms underlying response have not been thoroughly investigated. DNA damage and repair mechanisms influence not only the genetic predisposition to leukemia but are also important for refractoriness to treatment. Aim: The aim of this study is to investigate the possible alterations in the gene expression profile of DNA damage signaling pathways in two leukemic cell lines following their exposure to chemotherapeutic agents, namely, idarubicin and cytarabine, and to verify the findings in AML patient samples at diagnosis before the onset of chemotherapy. Methods: Cell lines Kasumi-1 with the t(8;21) and MV4-11 (biphenotypic B-myelomonocytic leukemia) were exposed either to idarubicin (0.1μΜ) for 6h or cytarabine (1μΜ) for 48h. Dead cells were eliminated from drug-treated cells using an appropriate commercial kit. Gene expression profiling through PCR arrays analysis (RT2 Profiler, Qiagen) was performed in triplicate after RNA extraction from untreated, chemotherapy-treated and live (chemo resistant) cells following chemotherapy exposure. Human DNA damage signaling pathway-related gene expression and statistical analysis was performed through the RT2 Profiler PCR Array data analysis tool. Moreover, mononuclear cells were isolated from bone marrow of 11 lymphoma patients, used as controls, and from 64 AML patients at diagnosis who subsequently received chemotherapy with the 7+3 regimen. Response to first-line chemotherapy was recorded and patients were assigned in two groups: Responders (n=53 patients) and non-Responders (n=11 patients). Total RNA was isolated (RNeasy plus Mini Kit, Qiagen), quantified and cDNA was synthesized. Relative expression of genes of interest was quantified using SYBR® Greenbased real-time RT-PCR (QuantiTect® Primer Assay, Qiagen) based on the ddCt method (Housekeeping gene GADPH). All samples were obtained from patients after informed consent and treated in accordance with the Declaration of Helsinki. Statistical analysis was performed using R Statistical Software (version 4.2.1). Results: Five genes were found significantly [p < 0.05, Students t-test] up-regulated in live cells from either leukemic cell lines after treatment with both agents and had a FoldChange > 2. More specifically PPP1R15A, CDKN1A and GADD45G genes were up-regulated in both live cell lines, GADD45A in live MV4-11 cells and EXO1 in live Kasumi cells (Figure 1A). The aforementioned genes were selected and their expression levels were quantified in human bone marrow samples. CDKN1A and GADD45G were found down-regulated in Responders [p=0.032 and p=0.001 respectively; Welch t-test] while PPP1R15A was significantly up-regulated [over 8-fold change, p= 2.08E-09; Welch t-test] compared to controls. Likewise, GADD45G and PPP1R15A were also significantly down and up regulated respectively, in non-Responders [p=0.08 and p=1.51E-05, Welch t-test]. Interestingly, PPP1R15A presented a 1.7-fold overexpression trend in non-Responders compared to Responders [p=0.18, Welch t-test] (Figure 1B). Conclusion: The results of our study suggest a dysregulation of the DNA damage and repair pathways in AML. Upregulation of GADD45G is known to dramatically induce apoptosis, differentiation, and growth arrest while increasing sensitivity of AML cells to chemotherapeutic drugs (Guo, Dan et al., Blood 2021). CDKN1A is involved in p53/TP53 mediated inhibition of cellular proliferation in response to DNA damage. Both were down-regulated in AML patients and are likely to play an important role in the pathogenesis of AML. PPP1R15A participates in DNA damage response facilitating the recovery of cells from stress. The up-regulation of PPP1R15A both in live cells treated with Ara-C and Cytarabine, as well as the 1.7-fold overexpression trend in non-Responders compared to Responders, supports the notion that PPP1R15A could be associated with resistance to induction treatment, which may have significant prognostic and therapeutic implications. A greater sample of AML patients both responding and not responding to chemotherapy, would be essential to delineate the role of genes involved in DNA damage and repair pathways in resistance to induction treatment. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Background: AML is the most common malignant myeloid disorder in adults. Relapses are initiated by chemoresistant leukemic cells. DNA damage and repair mechanisms influence not only the genetic predisposition to leukemia but are also very important for refractoriness to treatment. Aims: The aim of this study was to investigate the possible alterations in the gene expression profile in DNA damage signaling pathways and apoptosis in two leukemic cell lines following their exposure to chemotherapeutic agents, idarubicin and cytarabine and to confirm the results in AML patients’ cells. Methods: Kasumi-1 and MV4-11 AML cells were treated with either idarubicin (0.1 μM) for 6 h or cytarabine (1 μM) for 48 h. Dead cells were eliminated after exposure to the drug using the appropriate commercial kit. Gene expression profiling through PCR arrays analysis (RT2Profiler, Qiagen) was performed after RNA extraction from untreated, drug-treated and chemoresistant (live) cells. Human DNA Damage Signaling pathway related genes’ expression was evaluated and analyzed through RT2Profiler PCR Array data analysis tool. Following our initial results, PPP1R15A gene's relative expression was evaluated by qRT-PCR analysis with QuantiTect Primer Assays kit (Qiagen) in 12 de novo AML patients before the onset of the 7 + 3 combination chemotherapy and 17 healthy donors using the 2^-ΔΔCt method. Results: PCR Array analysis after idarubicin treatment of Kasumi-1 cells revealed a significant up-regulation of genes involved in apoptosis (BBC3), cell cycle (CDKN1A, PPP1R15A), DNA damage and repair (PNP), and ATM/ATR signaling (RBBP8) while cytarabine treatment led to the up-regulation of genes involved mostly in the DSB repair pathway i.e. HUS1,MLH1,NBN,XRCC1,XRCC2). Interestingly, significant differences in their gene expression patterns were observed between cytarabine-treated Kasumi-1 cells and chemoresistant ones. HUS-1 gene (DSB) was up-regulated in cytarabine-treated cells and down-regulated in chemoresistant cells, while MLH1 and NBN genes presented the opposite pattern. Most importantly, PPP1R15A gene's expression in both cytarabine and idarubicin chemoresistant MV4-11 cells was significantly up-regulated compared to drug treated cells. PPP1R15A gene's relative expression was significantly up-regulated in AML patients’ cells compared to controls (median: 0.72 vs 1.72, p < 0.05) and in non-responding to chemotherapy AML patients compared to controls (median: 0.72 vs 1.21, p < 0.05). Summary/Conclusion: Our data suggest differences in the gene expression pattern between chemoresistant cells and drug-treated cells, indicating the significance of DNA damage and repair pathways involved in chemoresistance. Specifically, the up-regulation of PPP1R15A gene in chemoresistant MV4-11 cells after treatment with both agents is of great importance since this gene participates in cell cycle and its transcript levels are increased following stressful growth arrest and treatment with DNA-damaging agents. Considering that MV4-11 is an AML chemoresistant cell line, up-regulation of the expression of PPP1R15A gene which facilitates recovery of cells from stress is totally compatible. These findings were further verified by qRT-PCR demonstrating overexpression of PPP1R15A gene in AML chemoresistant patients indicating the involvement of this gene in chemoresistance mechanisms.

Introduction: Azacitidine (AZA) is a hypomethylating agent that at low doses acts by inhibiting DNA methyltranferase activity. AZA is approved and widely used for the treatment of MDS patients and patients with AML not candidate for intensive chemotherapy. Unfortunately, even after an initial response, almost all patients relapse and so far -with the exception of a few clinical parameters and genetic mutations weakly correlated with favorable AZA response- the exact mechanisms underlying primary AZA resistance remain largely unknown. On the other hand, over the last years accumulated data suggest that hypoxia, an important regulatory factor of both, physiological and malignant, hematopoiesis, is also involved in MDS pathogenesis (Hayashi et al., 2018), while high Hif-1α levels in MDS have been previously correlated with poor overall survival and disease progression (Tong et al., 2012). Moreover, our group recently investigated the association between Hif-1α and response to AZA therapy and found that AZA-responders present with higher Hif-1α mRNA expression compared to non-responders/stable disease patients, while logistic regression analysis showed that Hif-1α mRNA expression is an independent predictor of response to AZA therapy (unpublished data). Aims: The current study focused on investigating the mechanisms underlying the observed association of Hif-1α over-expression with response to AZA-therapy, by examining the methyltransferase activity and mitochondrial dysfunction due to inactivation of complex II, which is reported to lead to increased Hif-1α expression. Methods: A total of 54 patients with a median age of 76 (52-89) years, and 10, age matched, healthy donors participated in the study. According to WHO 2016, 41 patients were classified as MDS (10 as MDS-EB-1, 24 as MDS-EB-2 and 7 as MDS-MLD) and 13 as AML. All patients received AZA treatment at the dose of 75mg/m2 x7 days SC. BM-derived mononuclear cells were isolated before treatment using the Ficoll-paque method, followed by RNA extraction using TRIzol reagent, and cDNA preparation using Superscript II reverse transcriptase. Hypoxia-inducible factor 1-alpha (Hif-1α), succinate dehydrogenase complex subunit D (DSHd) and DNA methyltrasferase beta (DNMT3b) expression were estimated by real time PCR TaqMan gene expression assays, using the appropriate primers and probes. Relative gene expression was calculated by comparative threshold cycle (2-ΔΔCt) method and normalized based on β-actin expression. Non-parametric tests were used for the statistical analysis of the results. Results: Out of the 54 examined patients, 28 responded to azacitidine treatment (R), (including CR, PR and HI), 9 failed to respond (NR), and 17 achieved stable disease status 9 (SD). NR and SD patients were considered as one group (NR/SD) in all analyses. Using Rt-PCR we found that the 2-ΔΔCt ratio of Hif-1α/β-Actin median expression for control samples was 1.18 (95% CI: 0.617-1.687), for AZA-responders 1.59 (95% CI: 1.029-3.18), while for NR/SD patients 0.754 (95% CI: 0.640-0.840), with a statistical significance between R and NR/SD patients (Mann-Whitney test, p=0.003). Moreover, the 2-ΔΔCt ratio of SDHd/β-Actin median expression for control samples was 1.2 (95% CI: 0.360-1.954), for R patients 0.81 (95% CI: 0.294-1.401), and for NR/SD patients 0.73 (95% CI: 0.542-0.793). Finally, for DNMT3b, the 2-ΔΔCt median expression ratio in control samples was 0.75 (95% CI: 0.637-1.526), for R patients 2.188 (95% CI: 1.547-3.630), while for NR/SD patients 1.338 (95% CI: 0.824-2.250). Conclusions: Our data suggest that both AZA-R and NR/SD patients present with low levels of SDHd mRNA, compared to control, in line with previous reports in MDS. For AZA-responders, this could be related to the observed Hif-1α mRNA over-expression, since the SDH inactivation (decreased Complex II activity) is known to cause HIF stabilization (Frezza et al., 2011; Selak et al., 2005). Nevertheless, NR/SD patients also appear with decreased SDHd activity, despite the observed low Hif-1α expression. Therefore, in those patients, Hif-1α- related AZA-therapy response seems to be independent from mitochondrial dysfunction and possibly relies on other hypoxia regulatory mechanisms. Moreover, our data suggest that AZA-responders appear with an increased DNMT3b expression compared to both control and NR/SD patients, which could also explain their better response to therapy. Disclosures Symeonidis: Pfizer: Research Funding; Sanofi: Research Funding; Tekeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; MSD: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Pappa:Novartis: Honoraria, Research Funding, Speakers Bureau; Celgene / GenesisPharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Honoraria, Research Funding; Amgen: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

INTRODUCTION AML is the most common malignant myeloid disorder in adults. Relapses are initiated by chemoresistant leukemic cells. DNA damage and repair mechanisms influence not only the genetic predisposition to leukemia but are also very important for refractoriness to treatment. The aim of this study was to investigate the possible alterations in the gene expression profile in DNA damage signaling pathways in two leukemic cell lines following their exposure to chemotherapeutic agents and verify the findings in AML patients. METHODS Kasumi-1 and MV4-11 AML cells were treated with either idarubicin (0.1μΜ) for 6h or cytarabine (1μΜ) for 48h. Dead cells were eliminated from drug-treated cells using the appropriate commercial kit. Gene expression profiling through PCR arrays analysis (RT2Profiler, Qiagen) was performed after RNA extraction from untreated, drug-treated and chemoresistant (live) cells following their exposure to cytotoxic agents. Human DNA Damage Signaling pathway related genes' expression was evaluated and analyzed through RT2Profiler PCR Array data analysis tool. Following our initial results, two genes were selected for further analysis: PPP1R15A and HUS-1 genes' relative expression was evaluated by qRT-PCR analysis with QuantiTect Primer Assays kit (Qiagen) using the 2^-∆∆Ct method. The analysis included 28 de novo AML patients before the onset of the 7+3 combination chemotherapy and 16 healthy donors. Eighteen cases had normal karyotype including 7 with flt3 mutation, 1 case had inv(16) and 9 cases intermediate risk karyotype. Statistics were performed through One Way Anova analysis. RESULTS PCR Array analysis after idarubicin and cytarabine treatment of Kasumi-1 cells revealed a significant up-regulation of genes involved in apoptosis, cell cycle, DNA damage and repair, and ATM/ATR signaling. Significant differences in their gene expression patterns were observed between cytarabine-treated Kasumi-1 cells and chemoresistant ones. HUS-1 gene (DSB) was 3x fold up-regulated in cytarabine-treated cells and 0.7x fold down-regulated in chemoresistant cells compared to untreated cells. Cytarabine and idarubicin treatment of MV4-11 cells led to an up-regulation of genes involved in cell cycle, DNA damage repair, including DSB repair and NER mechanisms. Most importantly, PPP1R15A gene's expression in both cytarabine and idarubicin chemoresistant MV4-11 cells was significantly 4.2x and 2.7x fold up-regulated compared to drug treated cells. Following these results the expression level of genes PPP1R15A and HUS1 was examined in the bone marrow cells of AML patients in order to verify their association with chemoresistance. PPP1R15A gene's relative expression was significantly up-regulated in non-responding to induction chemotherapy AML patients compared to responding (median: 2.705 vs. 0.73, p&lt;0.05) and in non-responding to chemotherapy AML patients compared to controls (median: 2.705 vs. 0.577, p&lt;0.01). HUS1 gene's relative expression was remarkably down-regulated in AML patients compared to controls (median: 1.585 vs. 7.74, p&lt;0.001). This was also observed comparing responding and refractory to chemotherapy AML patients to controls (median: 1.09 vs. 7.74, p&lt;0.001 and 1.585 vs. 7.74, p&lt;0.05, respectively). CONCLUSIONS The up-regulation of PPP1R15A gene in chemoresistant MV4-11 cells after treatment with cytotoxic agents is justified since this gene participates in growth arrest and apoptosis in response to DNA damage, negative growth signals and protein malfolding by binding to protein phosphatase PP1, and attenuating the translational elongation of key transcription factors through dephoshorylation of eukaryotic initiation factor 2a(eIF2a). Most importantly the significant increased baseline expression of PPP1R15A in AML chemoresistant patients indicates its involvement in chemoresistance mechanisms and paves the way for targeted treatment. HUS1 gene's expression was remarkably depressed in de novo AML samples. This gene is required for the optimal ATM/ATR signaling response to DSBs and replication stress forming part of the RAD9A-RAD1-HUS1 (9-1-1) complex functioning as a damage sensor in checkpoint pathway. Therefore the described above reduced expression in AML samples indicates reduced ATM-ATR response to DSBs associated with genetic instability and offers new options for synthetic lethality treatment strategies Disclosures Symeonidis: Tekeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; MSD: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding. Pappa:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Research Funding; Novartis: Honoraria, Research Funding, Speakers Bureau; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Honoraria, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Research Funding; Celgene / GenesisPharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

5-azacytidine (5-AZA) is considered the standard of care for patients with high-risk myelodysplastic syndromes (MDS) and patients with acute myeloid leukemia (AML) not candidate for intensive chemotherapy. However, even after an initial favorable response, almost all patients relapse, with the exact mechanisms underlying primary or secondary 5-AZA resistance remaining largely unknown. Several reports have previously demonstrated the significance of hypoxia in the regulation of both physiological and malignant hematopoiesis. In MDS, high hypoxia inducible factor 1 alpha (Hif-1 alpha) expression has been correlated with poor overall survival and disease progression, while its involvement in the disease's pathogenesis was recently reported. We herein investigated the possible association of the Hif-1 alpha signaling pathway with response to 5-AZA therapy in MDS/AML patients. Our data demonstrated that 5-AZA-responders present with higher Hif-1 alpha mRNA and protein expression compared to 5-AZA-non-responders/stable disease patients, before the initiation of therapy, while, interestingly, no significant differences in Hif-1 alpha mRNA expression at the 6-month follow-up were observed. Moreover, we found that 5-AZA-responders exhibited elevated mRNA levels of the Hif-1 alpha downstream targets lactate dehydrogenase a (LDHa) and BCL2 interacting protein 3 like (BNIP3L), a further indication of an overactivated Hif-1a signaling pathway in these patients. Kaplan-Meier survival analysis revealed a significant correlation between high Hif-1 alpha mRNA expression and better survival rates, while logistic regression analysis showed that Hif-1 alpha mRNA expression is an independent predictor of response to 5-AZA therapy. From the clinical point of view, apart from proposing Hif-1 alpha mRNA expression as a significant predictive factor for response to 5-AZA, our data offer new perspectives on MDS combinational therapies, suggesting a potential synergistic activity of 5-AZA and Hif-1 alpha inducers, such as propyl hydroxylases inhibitors (PHDi).

The cover image depicts Anti-Hif-1a immunohistochemistry of BM biopsy sectionsfrom a 5-AZA-R patient, with high frequency of Hif-1α (+) cells, and is based on the Original Article Upregulated Hif-1α signaling pathway in high risk myelodysplastic syndrome and acute myeloid leukemia patients is associated with better response to 5-azacytidine - Data from the Hellenic MDS study group by Vassiliki Pappa et al., https://doi.org/10.1002/hon.2834.