Targeting TBC1D15 Reverses TMZ-resistance in Glioblastoma by Modulating Lysosomal Ca²⁺/TFEB/Cx43 Axis via Mitochondria-Lysosome Contact

Abstract Glioblastoma multiforme (GBM) is among the most malignant central nervous system tumors with a poor prognosis. Resistance to temozolomide (TMZ), the first-line chemotherapy drug, is the primary obstacle to treatment efficacy in GBM patients. Our study identified TBC1D15 as an oncogene in GBM and a potential therapeutic target for TMZ resistance. TBC1D15 is overexpressed in recurrent GBM (rGBM) and TMZ-resistant cells. Knockdown of TBC1D15 significantly sensitized TMZ-resistant cells to TMZ. Further investigation revealed that TBC1D15 knockdown prolonged mitochondria-lysosome contact (MLC), altered lysosomal Ca²⁺ kinetics, inhibited TFEB nuclear translocation, thereby downregulating Cx43 expression, ultimately reversing GBM resistance to TMZ. Additionally, through high-throughput compound library screening integrated with 3D protein structure analysis, we identified dutasteride, an FDA-approved drug, as a specific inhibitor of TBC1D15. Dutasteride increased GBM sensitivity to TMZ both in vitro and in vivo. The combination of dutasteride and TMZ represented a promising treatment strategy for GBM, offering a potential therapeutic approach to overcome TMZ resistance.