cirSIRT5 induces ferroptosis in bladder cancer by forming a ternary complex with SYVN1/PHGDH.

Bladder cancer (BC) represents a prevalent and formidable malignancy necessitating innovative diagnostic and therapeutic strategies. Circular RNAs (circRNAs) have emerged as crucial regulators in cancer biology. In this study, we comprehensively evaluated ferroptosis levels in BC cells utilizing techniques encompassing lipid peroxidation assessment, transmission electron microscopy, and malondialdehyde (MDA) measurement. Additionally, we probed into the mechanistic intricacies by which circRNAs govern BC, employing RNA pull-down, RNA immunoprecipitation (RIP), and immunoprecipitation (IP) assays. Our investigation unveiled circSIRT5, which displayed significant downregulation in BC. Notably, circSIRT5 emerged as a promising prognostic marker, with diminished expression correlating with unfavorable clinical outcomes. Functionally, circSIRT5 was identified as an inhibitor of BC progression both in vitro and in vivo. Mechanistically, circSIRT5 exerted its tumor-suppressive activities through the formation of a ternary complex involving circSIRT5, SYVN1, and PHGDH. This complex enhanced the ubiquitination and subsequent degradation of PHGDH, ultimately promoting ferroptosis in BC cells. This ferroptotic process contributed significantly to the inhibition of tumor growth and metastasis in BC. In addition, FUS was found to accelerate the biogenesis of circSIRT5 in BC. These findings provide valuable insights into the pivotal role of circSIRT5 in BC pathogenesis, underscoring its potential as a diagnostic biomarker and therapeutic target for this malignancy.