FTO-mediated autophagy promotes progression of clear cell renal cell carcinoma via regulating SIK2 mRNA stability

The progression of clear cell renal cell carcinoma (ccRCC) remains a major challenge in clinical practice, and elucidation of the molecular drivers of malignancy progression is critical for the development of effective therapeutic targets. Recent studies have demonstrated that N(6)-methyladenosine (m(6)A) is the most abundant modification of eukaryotic mRNA and plays a key role in tumorigenesis and progression. However, the biological roles and underlying mechanisms of m(6)A-mediated autophagy in cancers especially in ccRCC remain poorly elucidated. m(6)A dot blot assay, m(6)A RNA methylation assay kit and immunofluorescence analysis were used to profile m(6)A levels in tissue samples and their correlation with autophagic flux. Expression patterns and clinical significance of fat mass and obesity-associated protein (FTO) were determined through bioinformatics analysis, real-time PCR, western blotting, immunohistochemistry. RNA-seq, MeRIP-seq, MeRIP-qRT-PCR, RIP-qRT-PCR, transmission electron microscopy, immunofluorescence analysis and luciferase reporter assay were used to investigate the underlying mechanism of the FTO-autophagy axis. The role of FTO and autophagy in ccRCC progression was evaluated both in vitro and in vivo. Here we found that m(6)A modification was suppressed and closely related to autophagic flux in ccRCC. Elevated FTO was inhibited by rapamycin, whereas silencing FTO enhanced autophagic flux and impaired ccRCC growth and metastasis. SIK2 was identified as a functional target of m(6)A-mediated autophagy, thereby prompting FTO to play a conserved and important role in inhibiting autophagy and promoting tumorigenesis through an m(6)A-IGF2BP2 dependent mechanism. Moreover, the small molecule inhibitor FB23-2 targeting FTO inhibited tumor growth and prolonged survival in the patient-derived xenograft (PDX) model mice, suggesting that FTO is a potential effective therapeutic target for ccRCC. Our findings uncovered the crucial role of FTO/autophagy/SIK2 axis in modulating the progression of ccRCC, suggesting that FTO may serve as a valuable prognostic biomarker and promising therapeutic target in ccRCC.