The m6A Reader YTHDF2 Promotes Bladder Cancer Progression by Suppressing RIG-I-Mediated Immune Response.

N6-Methyladenosine (m6A) is the most prevalent internal modification of mammalian mRNAs. Recent studies have shown that m6A methyltransferases METTL3 and METTL14 play important roles in urothelial bladder carcinoma (BLCA). To provide a more comprehensive understanding of the m6A regulatory landscape in bladder cancer, we investigated the role of YTHDF2, a crucial m6A reader, in BLCA. YTHDF2 was frequently upregulated at both the RNA and protein level in BLCA. Functionally, YTHDF2 promoted the proliferation and tumor growth of BLCA cells in vitro and in vivo, respectively. Integrative RNA sequencing and m6A sequencing analyses identified RIG-I as a downstream target of YTHDF2. Mechanistically, YTHDF2 bound to the coding sequence of DDX58 mRNA, which encodes RIG-I, and mediated its degradation in an m6A-dependent manner. Knockdown of RIG-I inhibited apoptosis and promoted the proliferation of BLCA cells. Depleting RIG-I was also able to reverse the effects of YTHDF2 deficiency. YTHDF2-deficient BLCA cells implanted orthotopically in recipient mice activated an innate immune response and promoted recruitment of CD8+ T lymphocytes into the tumor bed and the urothelium. Moreover, YTHDF2 deficiency enhanced the efficacy of Bacillus Calmette-Guérin immunotherapy treatment. This study reveals that YTHDF2 acts as an oncogene in BLCA. YTHDF2 inhibits RIG-I to facilitate immune evasion, supporting testing YTHDF2 inhibition in combination with immunotherapy. SIGNIFICANCE: YTHDF2 regulates RIG-I-mediated innate immune signaling to support bladder cancer progression, highlighting the functional importance of m6A modifications in bladder cancer and uncovering therapeutic opportunities to improve patient outcomes.