Tanshinone IIA promotes METTL3/METTL14-mediated FDX1 m6A modification to induce cuproptosis in bladder cancer

Tanshinone IIA (Tan IIA), a pleiotropic bioactive natural compound, has a general anti-tumor effect, as well as in bladder cancer. However, little is known about its mechanism. This work attempts to explore the mechanism of Tan IIA promoting cuproptosis in bladder cancer cells and the effective targets. Copper concentration and total m6A quantification were determined using test kits. Cell viability was tested by CCK-8. Gene expression was evaluated by western blot or qRT-PCR. The m6A methylation level of FDX1 was detected by methylated RNA immunoprecipitation. FDX1 3'UTR activity was evaluated by luciferase activity assay. YTHDC1 binding to FDX1 was detected by RNA immunoprecipitation assay. Inhibition of tumor growth by Tan IIA was verified using a mouse xenograft tumor model. Tan IIA inhibits cell viability and induces the expression of FDX1 and lip-DLAT, key regulators of cuproptosis, in bladder cancer cells. The copper chelator tetrathiomolybdate weakens the inhibiting effect of Tan IIA on cell viability; while Tan IIA enhances the inhibiting effect of elesclomol-Cu on cell viability. FDX1 knockdown reverses Tan IIA-induced cuproptosis. Tan IIA increases FDX1 m6A modification, which is reversed by S-adenosylhomocysteine, an inhibitor of METTL3/METTL14, and this event mediates Tan IIA-induced cuproptosis of bladder cancer cells. The effectiveness of SAH in Tan IIA promoting cuproptosis and antitumor utility is demonstrated in a xenograft tumor model. Tan IIA exerts an anti-bladder cancer effect by promoting the cuproptosis of tumor cells, and the possible mechanism is to promote the expression of FDX1 by METTL3/METTL14-mediated the increasing FDX1 m6A modification.