PT - JOURNAL ARTICLE AU - Cavalcante, Gabrielle Melo AU - Borges, Daniela Paula AU - de Oliveira, Roberta Taiane Germano AU - Furtado, Cristiana Libardi Miranda AU - Alves, Ana Paula Negreiros Nunes AU - Sousa, Alceu Machado AU - de Paula, Dayrine Silveira AU - Filho, Francisco Dário Rocha AU - Magalhães, Silvia Maria Meira AU - Ribeiro-Jr, Howard Lopes AU - Pinheiro, Ronald Feitosa TI - Tissue methylation and demethylation influence translesion synthesis DNA polymerases (TLS) contributing to the genesis of chromosomal abnormalities in myelodysplastic syndrome AID - 10.1136/jclinpath-2020-207131 DP - 2022 Feb 01 TA - Journal of Clinical Pathology PG - 85--93 VI - 75 IP - 2 4099 - http://jcp.bmj.com/content/75/2/85.short 4100 - http://jcp.bmj.com/content/75/2/85.full SO - J Clin Pathol2022 Feb 01; 75 AB - Aims DNA methylation has its distribution influenced by DNA demethylation processes with the catalytic conversion of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC). Myelodysplastic syndrome (MDS) has been associated with epigenetic dysregulation of genes related to DNA repair system, chronic immune response and cell cycle.Methods We evaluated the tissue DNA methylation/hydroxymethylation in bone marrow trephine biopsies of 73 patients with MDS, trying to correlate with the mRNA expression of 21 genes (POLH, POLL, REV3L, POLN, POLQ, POLI, POLK, IRF-1, IRF-2, IRF-3, IRF-4, IRF-5, IRF6, IRF-7, IRF-8,IRF-9, MAD2, CDC20, AURKA, AURKB and TPX2).Results The M-score (5mC) was significantly higher in patients with chromosomal abnormalities than patients with normal karyotype (95% CI –27.127779 to –2.368020; p=0.022). We observed a higher 5mC/5hmC ratio in patients classified as high-risk subtypes compared with low-risk subtypes (95% CI –72.922115 to –1.855662; p=0.040) as well as patients with hypercellular bone marrow compared with patients with normocellular/hypocellular bone marrow (95% CI –69.189259 to –0.511828; p=0.047) and with the presence of dyserythropoiesis (95% CI 17.077703 to 51.331388; p=0.001). DNA pols with translesion activity are significantly influenced by methylation. As 5mC immunoexpression increases, the expressions of POLH (r=−0.816; r2 =0.665; p=0.000), POLQ (r=−0.790; r2=0.624; p=0.001), PCNA (r=−0.635; r2=0.403; p=0.020), POLK (r=−0.633; r2=0.400; p=0.036 and REV1 (r=−0.578; r2=0.334; p=0.049) decrease.Conclusions Our results confirm that there is an imbalance in the DNA methylation in MDS, influencing the development of chromosomal abnormalities which may be associated with the low expression of DNA polymerases with translesion synthesis polymerases activity.All data relevant to the study are included in the article or uploaded as supplemental information.