Molecular mechanistic approach to reveal decitabine's effect on DNMT gene modulation and its inhibitory role in heavy metal-induced proliferation in urinary bladder cancer cell line

Heavy metals are pervasive environmental and occupational carcinogens known to induce uncontrolled cell proliferation. They influence a number of cellular processes, including proliferation, metabolism, apoptosis, and carcinogenesis. Among the several underlying mechanisms of carcinogenesis, metal-induced aberrant modulation of DNA methyltransferase (DNMT) activity may play crucial role. In this context, our study explored the proliferative and/or cytotoxic effects of heavy metals on the T24 urinary bladder cancer cell line. Additionally, we evaluated the effects of heavy metals and the chemotherapeutic agent decitabine on DNMT expression and activity. For investigative purposes, T24 cells were exposed to different heavy metals; namely, lead (Pb), chromium (Cr), cadmium (Cd), nickel (Ni), and arsenic (As) at concentrations ranging from 0.5 to 32 μM for 24, 48, and 72 h, as well as to decitabine (1 to 64 μM) for 72 h. Post-incubation, cell proliferation and migration increased, and mitochondrial membrane potential decreased significantly in the presence of heavy metals, especially Cr and Cd. Moreover, in the presence of Cr and Cd, expression of DNMT1 and DNMT3b genes enhanced significantly. Furthermore, decitabine treatment effectively inhibited Cd- and Cr-induced proliferation and downregulated expression of DNMT genes. In conclusion, heavy metals such as Cd and Cr may contribute to urinary bladder carcinogenesis through DNMT upregulation, while decitabine showedprotective effects by suppressing DNMT expression and inhibiting cell proliferation.