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Abstract Background Bladder cancer (BC) is a malignant tumor. Methyltransferase-like 7B (MEETL7B) is a methyltransferase and its role in BC has not yet been revealed. Method Stable METTL7B knockdown or overexpression were achieved by lentiviral transduction in SW780 and TCCSUP cell lines. Xenografts tumors were established via subcutaneous injection of stable transfectants in BALB/c mice. Results A database search indicated that METTL7B was elevated in BC and it was validated in BC cell lines. METTL7B silencing suppressed cell proliferation and tumorigenesis in vitro and in vivo. Besides, METTL7B knockdown induced cell cycle arrest in G1 phase with a reduction in cyclin D1(CCND1), CDK4, and CDK6 levels and an elevation in CDKN2D levels in cells. Considering that ferroptosis is emerging as a therapeutic target for cancer, and the possible relationship between METTL7B and antioxidant enzymes. We, here, examined that ectopic METTL7B expression abolished ferroptosis markers in cells raised by Erastin treatment, including the production of lipid ROS, the increased cellular iron and MDA content, the decreased gene expression of ACSL3, FANCD2, and FADS2, as well as the mitochondrial injury observed by electron microscopy. Mechanically, ectopic METTL7B expression promoted m6A modification on ACSL3 mRNA. Gain of functional experiment exhibited that METTL7B inhibited Erastin-induced ferroptosis via ACSL3. Overexpressed PLAGL2 is identified as a possible independent predictor in BC and bioinformatics predicted the potential binding sites between PLAGL2 and METTL7B promoter region. Dual luciferase and chromatin immunoprecipitation analysis provided evidence that PLAGL2 directly binds to METTL7B promoter region. Conclusions METTL7B is involved in BC development and progression. METTL7B may mediate m6A modification on ACSL3 mRNA to negatively regulate ferroptosis in BC cells, which provides a potential therapeutic target for BC via ferroptosis. Graphical Abstract

Purpose: This study aimed to investigate the effect of the N6-methyladenosine (m6A) dependent ferroptosis on cisplatininduced Sertoli cell injury. Materials and Methods: A cisplatin exposure mouse model was established by intraperitoneal injection of cisplatin in our study. TM4 cell lines was used for in vitro study. Ferroptosis was detected according to metabolomic analysis and a series of assays, including malondialdehyde, glutathione, and glutathione disulfide concentration detection, 2',7'-dichlorodihydrofluorescein diacetate and BODIPY 581/591 C11 probe detection, and transmission electron microscope imaging. Key ferroptosisrelated genes were identified via transcriptomic analysis, western blot and immunohistochemistry. The m6A modification was demonstrated via m6A RNA immunoprecipitation and luciferase reporter assays. Immune cell infiltration was detected by mass cytometry, and verified by flow cytometry and immunofluorescence. Results: Ferroptosis, but not other types of programmed cell death, is a significant phenomenon in cisplatin-induced testis damage and Sertoli cell loss. Ferroptosis induced by cisplatin in Sertoli cell/TM4 cell is GPX4 independent but is regulated by SLC7A11 and ALOX12. Both SLC7A11 and ALOX12 are regulated via m6A dependent manner by METTL3. Furthermore, overexpressed ALOX12-12HETE pathway may result in macrophage polarization and inflammatory response in cisplatin exposure testis. Conclusions: Cisplatin-induced Sertoli cell injury via ferroptosis and promoted ferroptosis in an m6A dependent manner. m6A modification of both SLC7A11 and ALOX12 mRNA could result in ferroptosis in our in vitro model. Further, overexpressed ALOX12 can cause more production of 12-HETE, which may be responsible for testis inflammation caused by cisplatin.