PF371 DNA METHYLTRANSFERASES GENE EXPRESSION LEVELS IN CHRONIC LYMPHOCYTIC LEUKEMIA ‐ IMPACT IN DEVELOPMENT, DIAGNOSIS AND PROGNOSIS

Abstract

Background:Chronic lymphocytic leukemia (CLL) is the most common leukemia among adults in the western world and is characterized by the accumulation in blood, bone marrow and secondary lymphoid organs of long‐lived resting clonal B lymphocytes with a very low proliferation index and/or that proliferate abnormally. The disease has a notable clinical course diversity, with different prognosis and distinct treatment needs. However, the exact etiology is still unknown. Since cancer cells have a global DNA hypomethylation and local hypermethylation, there are evidences that epigenetic modifications have an important role in CLL pathogenesis. DNA methyltransferases (DNMT), including DNMT1, DNMT3A and DNMT3B, are responsible for DNA methylation and changes in the expression of these enzymes were observed in other hematological malignancies.Aims:The aim of this study was to evaluate the expression levels of DNMT1, DNMT3A and DNMT3A genes in chronic lymphocytic leukemia patients and analyze its correlation with clinical and laboratory data, in order to identify potential biomarkers of diagnosis and/or prognosis.Methods:We evaluated the DNMTs in peripheral blood of 68 CLL patients and 23 controls (CTL). Informed consent was obtained in accordance with the Helsinki Declarations. qPCR was used to evaluate the gene expression levels of DNMT1, DNMT3A, DNMT3B and GUSB (endogenous control). Mann–Whitney U and Kruskal–Wallis tests were used to assess the statistical significance between groups. Receiver operating characteristic (ROC) curves analysis was performed to analyze variables accuracy as diagnostic biomarker. Survival analysis was performed by Kaplan Meier method. Patients were dichotomized according to the cut off points obtained from the ROC curves constructed to predict death. All statistical analysis were two sided and a p < 0.05 was considered statistically significant.Results:This study enrolled 68 CLL patients, 37 males and 31 females with a median age of 65 years (48–101), and 23 CTL, 8 males and 15 females with a median age of 72 years (58–88). According with Binet staging system 54 patients (89%) were low risk (A), 2 (3%) intermediate (B) and 5 (8%) high risk (C). Cytogenetic abnormalities usually associated with good prognosis were found in 28 patients (62%) and with bad prognosis in 17 patients (38%), including 12 with del(17p) (27%). We observe that CLL patients had a higher DNMT1 expression [median: 0691; interquartile range (IR): 0.990] and a significant lower DNMT3B gene expression levels [median: 0.023, IR: 0.040; p = 0.020] compared with controls [DNMT1 median: 0.603, IR: 0.995; DNMT3B median: 0.038; IR: 0.267] and in 12 patients (18%) no expression of DNMT3B was detected. On the other hand, DNMT3A expression levels are similar in patients and controls (CLL median: 0.281, IR: 0.283; CTL median: 0.283, IR: 0.268). Using ROC analysis, DNMT3B expression levels shown to be a possible diagnosis biomarker (AUC: 0.720; IC95%: 0.596–0,843; cut‐off<0.026; sensitivity: 63%; specificity: 78%; p = 0.002). The expression levels of DNMT1, DNMT3A and DNMT3B show no correlation with clinical and laboratory data, including Binet staging system or cytogenetic abnormalities. According to ROC analysis and Kaplan Meier curves, CLL patients with DNMT3B expression levels under 0.031 present a tendency for worse survival.Summary/Conclusion:This study suggests that DNMT3B expression levels may contribute to CLL development and may be potential new diagnostic and prognostic biomarkers.The work was supported by CIMAGO (Project 02/18) and FCT (SFRH/BD/51994/2012).