TET2 downregulation limits oxidative stress-induced cytotoxicity of high dose ascorbate in dabrafenib-resistant melanoma cells.

Aim: This study investigates the role of Ten-Eleven Translocation (TET) dioxygenases in melanoma-acquired resistance to BRAF inhibitors (BRAFi), focusing on their contributions to epigenetic remodeling and redox balance. Methods: Dabrafenib-resistant A375 and M14 melanoma cell lines were generated and analyzed for TET family expression. Transcriptomic data from independent RNA-seq datasets of BRAFi-resistant melanoma models were used for validation. Cells were treated with high-dose L-ascorbic acid (ASC), a cofactor enhancing TET activity, and assessed for 5-hydroxymethylcytosine (5hmC) levels, reactive oxygen species (ROS) production, and cytotoxicity. Antioxidant capacity and expression of GLUT1, a transporter for oxidized ASC, were evaluated. TET2 was silenced to determine its functional role in ASC-mediated effects. Results: BRAFi-resistant cells displayed reduced TET2 expression and altered levels of other TET family members, consistent with RNA-seq data. ASC treatment increased 5hmC levels and induced ROS-dependent cytotoxicity predominantly in parental cells, while resistant cells were less sensitive. Resistant cells exhibited enhanced antioxidant defenses and reduced GLUT1 expression. TET2 silencing diminished ASC-induced 5hmC accumulation, ROS production, and GLUT1 expression, indicating a central role for TET2 in mediating ASC cytotoxicity. Conclusion: These findings identify a TET2-dependent epigenetic-metabolic axis that regulates redox vulnerability in melanoma. The link between TET2 activity, GLUT1 expression, and ROS-mediated cytotoxicity highlights potential biomarkers and therapeutic targets to overcome resistance to BRAFi.