RNA N⁶-Methyladenosine-Binding Protein YTHDFs Redundantly Attenuate Cancer Immunity by Downregulating IFN-γ Signaling...

Immunotherapy holds potential as a treatment for gastric cancer (GC), though immune checkpoint inhibitor (ICI) resistance remains an obstacle. One resistance mechanism involves defects in interferon-γ (IFN-γ) signaling, in which IFN-γ is linked to improved responsiveness to ICIs. Herein, the roles of RNA N⁶-methyladenosine (m6A) modifications in regulation of IFN-γ signaling and the responsiveness to ICIs are unveiled. The m6A-binding protein YTH N⁶-methyladenosine RNA-binding protein F1 (YTHDF1) is overexpressed in GC tissues, correlating with the suppression of cancer immunity and poorer survival rates. YTHDF1 overexpression impaired the responsiveness to IFN-γ in GC cells, and knockdown studies indicated the redundant effects of YTHDF2 and YTHDF3 with YTHDF1 in IFN-γ responsiveness. RNA immunoprecipitation sequencing revealed YTHDFs directly target interferon regulatory factor 1 (IRF1) mRNA, a master regulator of IFN-γ signaling, leading to reduced RNA stability and consequent downregulation of IFN-γ signaling. Furthermore, in mouse syngeneic tumor models, Ythdf1 depletion in cancer cells resulted in reduced tumor growth and increased tumor-infiltrating lymphocytes, which are attributed to the augmentation of IFN-γ signaling. Collectively, these findings highlight how YTHDFs modulate cancer immunity by influencing IFN-γ signaling through IRF1 regulation, suggesting their viability as therapeutic targets in cancer immunotherapy.