Abstract

Background: 6-thioguanine (6-TG) is one of the thiopurine drugs with successful use in oncology, especially for acute lymphoblastic leukemia (ALL). 6-TG is proposed to act as an epigenetic drug affecting DNA methylation. The aim of this study was to clarify the effect of 6-TG on the proliferation, viability and expression of genes coding for the enzymes DNA methyltransferase 3A and DNA methyltransferase 3B (DNMTs) as well as histone deacetylase 3 (HDAC3) in the human B cell-ALL cell line Nalm6. Materials and Methods: In this experimental study, Nalm6 cells and also normal peripheral blood mononuclear cells (PBMCs) were grown in RPMI 1640 medium containing 10% fetal bovine serum. They were then treated with 6-TG at their exponential growth phase. Cell viability was monitored using the Cell Counting Kit-8 assay with an enzyme-linked immunosorbent assay (ELISA) reader. The expressions of the above-mentioned 3 genes were quantified using real-time PCR. Results: 6-TG could inhibit the proliferation of Nalm6 cells and decrease their viability. In Nalm6 cells, as compared to normal PBMCs, 6-TG significantly decreased HDAC3 (p = 0.008) as well as DNMT3B (p = 0.003) gene expressions, but increased the expression of DNMT3A gene (p = 0.02) after normalization to GAPDH, as the housekeeping gene. Conclusion: These findings suggested that the altered expression of DNMT3A, DNMT3B and HDAC3 genes was responsible for at least part of the antitumoral properties of 6-TG, providing an insight into mechanism of its action as an epigenetic drug.