Intra-arterial infusion chemotherapy utilizing cisplatin inhibits bladder cancer by decreasing the fibrocytic myeloid-derived suppressor cells in an m6A-dependent manner

Intra-arterial infusion chemotherapy (IAIC), using immunomodulatory cisplatin, is a novel treatment for bladder cancer (BC) that allows the delivery of specific drugs to the local malignant lesion. To explore the immunomodulatory effect of cisplatin during IAIC, we detected the proportion of immunosuppressed cells in BC tissue from eight BC patients, with the reduction of myeloid-derived suppressor cells (MDSCs), more specifically fibrocytic-MDSCs (f-MDSCs). Further, we demonstrated that cisplatin inhibits their proliferation and immunosuppressive activity. f-MDSCs promote tumor proliferation and metastasis in the BC immune environment. Then, we analyzed the genetic differences detected in samples before and after chemotherapy and found that granulocyte colony-stimulating factors (G-CSF) decreased after IAIC. Furthermore, G-CSF methylation decreased following treatment with cisplatin. Specifically, treatment with cisplatin decreased the methylase (METTL3) levels in BC cells, which is important for G-CSF production. Collectively, cisplatin decreased the number of f-MDSCs during IAIC, by blocking G-CSF methylation via targeting METTL3.