ABSTRACT Introduction: Immune checkpoints are regulators of the immune system response that allow self-tolerance. Molecules such as Programmed Cell Death Protein 1 (PD-1) and its Ligand (PD-L1) participate in the immune checkpoint by signaling co-inhibition of lymphocyte responses. In cancers, PD-L1 expression is associated with the immune evasion mechanism, which favors tumor growth. The use of anti-PD-1/PD-L1 drugs is already well described in solid tumors, but still not fully understood in hematologic malignancies. Myelodysplastic neoplasms (MDSs) are heterogeneous bone marrow disorders with an increased risk of progression to Acute Myeloid Leukemia (AML). The MDS affects hematopoietic stem cells and its pathogenesis is linked to genetic and epigenetic defects, in addition to immune dysregulation. The influence of the PD-L1 on the MDS remains unknown. Methods: In this study, we evaluated the mRNA expression of the PD-L1 in 53 patients with MDS, classified according to the WHO 2016 Classification. Results: Patients with dyserythropoiesis presented significantly higher PD-L1 expression than patients without dyserythropoiesis (p = 0.050). Patients classified as having MDS with an excess of blasts 2 (MDS-EB2) presented a significant upregulation in the mRNA expression of the PD-L1 compared to the MDS with an excess of blasts 1 (MDS-EB1) (p = 0.050). Furthermore, we detected three patients with very high levels of PD-L1 expression, being statistically classified as outliers. Conclusion: We suggested that the high expression of the PD-L1 is associated with a worse prognosis in the MDS and functional studies are necessary to evaluate the possible use of anti-PD-L1 therapies for high-risk MDS, such as the MDS-EBs. Introduction selftolerance. selftolerance self tolerance. tolerance self-tolerance PD1 PD (PD-1 PDL1 PDL L1 L (PD-L1 coinhibition co inhibition responses cancers PD-L mechanism growth antiPD1/PDL1 antiPD1PDL1 antiPDPDL anti 1/PD anti-PD-1/PD-L tumors malignancies MDSs (MDSs AML. AML . (AML) defects dysregulation unknown Methods study 5 201 Classification Results p 0.050. 0050 0.050 0 050 0.050) MDSEB2 MDSEB EB2 EB (MDS-EB2 MDSEB1 EB1 (MDS-EB1 Furthermore outliers Conclusion antiPDL1 antiPDL anti-PD-L highrisk MDSEBs. MDSEBs EBs. EBs MDS-EBs (PD- (PD-L antiPD1 antiPD antiPD1/PDL antiPD1PDL 1PD (AML 20 005 0.05 05 (MDS-EB (PD 00 0.0 0.

Abstract Nucleotide excision repair pathway (NER) is an essential mechanism for single-strand breaks (SSB) repair while xeroderma pigmentosum family (XPA to XPG) is the most important system to NER. Myelodysplastic syndrome (MDS) is a heterogeneous hematological cancer characterized by cytopenias and risk of acute myeloid leukemia (AML) transformation. MDS pathogenesis has been associated with problems of DNA repair system. This report aimed to evaluate NER polymorphisms (XPA rs1800975, XPC rs2228000, XPD rs1799793 and XPF rs1800067) in 269 MDS patients of different populations in Latin America (173 Brazilian and 96 Argentinean). Genotypes were identified in DNA samples by RT-qPCR using TaqMan SNP Genotyping Assay. Regarding rs1799793 polymorphism of XPD for Brazilian population, the heterozygous genotype AG presented a high odds ratio (OR) to have a normal karyotype (p= 0.012, OR=3.000) and the mutant homozygous genotype AA was associated to a high OR of AML transformation (p= 0.034, OR=7.4). In Argentine population, the homozygous mutant AA genotype of rs1800975 polymorphism of XPA was associated with an increased odd to have hemoglobin levels below 8g/dL (p= 0.013, OR=10.000) while for the rs1799793 polymorphism of XPD, the heterozygous AG genotype decreased OR to be classified as good (p< 0.001, OR=9.05 × 10−10), and intermediate (p< 0.001, OR=3.08 × 10−10), according to Revised-International Prognostic Scoring System. Regarding the rs1800067 polymorphisms of XPF, the homozygous mutant AA genotype showed a decreased OR to be classified as good (p< 0.001, OR=4.03 × 10−13) and intermediate (p< 0.001, OR=2.54 × 10−13). Our report reinforces the heterogeneity of MDS and demonstrates the importance of ethnic differences and regional influences in pathogenesis and prognosis of MDS. (NER singlestrand single strand SSB (SSB XPG (MDS (AML rs rs2228000 rs179979 26 173 (17 9 Argentinean. Argentinean . Argentinean) RTqPCR RT qPCR Assay population (OR p= p (p 0012 0 012 0.012 OR=3.000 OR3000 3 000 0034 034 0.034 OR=7.4. OR74 OR=7.4 7 4 OR=7.4) rs180097 8gdL gdL 8g dL g 0013 013 0.013 OR=10.000 OR10000 10 p< 0001 001 0.001 OR905 05 OR=9.0 10−10, 1010 10−10 , 10−10) OR308 08 OR=3.0 RevisedInternational Revised International System rs180006 OR403 03 OR=4.0 10−13 1013 13 OR254 2 54 OR=2.5 10−13. rs222800 rs17997 17 (1 01 0.01 OR=3.00 OR300 00 003 0.03 OR7 OR=7. rs18009 OR=10.00 OR1000 1 0.00 OR90 OR=9. 101 10−1 OR30 OR=3. rs18000 OR40 OR=4. OR25 5 OR=2. rs22280 rs1799 ( 0.0 OR=7 rs1800 OR=10.0 OR100 OR9 OR=9 10− OR3 OR=3 OR4 OR=4 OR2 OR=2 rs2228 rs179 0. OR= rs180 OR=10. OR10 rs222 rs17 rs18 OR=10 OR1 rs22 rs1 OR=1 rs2

Myelodysplastic syndromes (MDS) are a heterogeneous group of hematological malignancies characterized by dysplasias, ineffective hematopoiesis and risk of acute myeloid leukemia transformation. Approximately 90% of MDS patients present mutations in genes involved in various cell signaling pathways. Specialized DNA polymerases, such as POLN, POLI, POLK, POLQ, POLH, POLL and REV3L, insert a nucleotide opposite replication–blocking DNA lesions in an error-prone manner and, in this way, sometimes can actively promote the generation of mutation. For the best of our knowledge, has not been described the mutations of these genes in MDS. DNA target sequencing CDS regions of the REV3L gene was performed in a 58-year-old man diagnosed as High Risk Myelodysplastic Syndrome. The patient presented very low hemoglobin, increased number of blasts, karyotype:47,XY,+8[6]/47,XY,del(7)(q32),+8[7], no response to hypomethylating therapy (decitabine), all markers of poor prognosis. Target sequencing identified a mutation c.9253-6T>C REV3L (Substitution - intronic) with VAF (variant allele frequency) = 16% considered pathogenic according to Functional Analysis through. Hidden Markov Models (FATHMM). This is the first evidence of REV3L mutation in MDS and, of utmost importance, associated with poor prognosis.