Targeting the RNA m6A reader YTHDF2 in tumor-associated macrophages shapes tumor immunity and immunotherapy

The presence of tumor-associated macrophages (TAMs) in the tumor microenvironment (TME) affects cancer progression and immunotherapy response. The RNA m6A methylation, an epigenetic modification, has recently been found to play a pivotal role in shaping the TME. However, the role and underlying mechanisms by which RNA m6A methylation regulates TAMs function and anti-tumor immunity remain elusive. Here we show that depletion of YTHDF2, a well-known m6A reader, in TAMs suppresses tumor growth and metastasis. Myeloid YTHDF2 deficiency reprograms TAMs to anti-tumorigenic type and increases their cross-presentation ability, thereby enhancing CD8+T cell-mediated anti-tumor immunity. Transcriptome-wide screening identifies YTHDF2 deficiency facilitates anti-tumorigenic TAMs reprogramming through targeting IFN-??STAT1 signaling. Selectively targeting YTHDF2 in TAMs using toll-like receptor 9 agonist - conjugated small interfering RNA against YTHDF2 effectively promotes anti-tumor immunity, restrains tumor growth, and enhances the efficacy of anti-PD-L1 therapy. Together, our findings suggest that YTHDF2 in TAMs might be a promising therapeutic target for cancer immunotherapy. Overall design: Total RNA was isolated by TRIzol reagent from fifty million M1-type BMDMs of WT and Ythdf2 cKO mice. m6A MeRIP sequencing was performed to detect the m6A modification alterations in two groups. YTHDF2 RNA immunoprecipitation sequencing was performed to map the target transcripts bound by YTHDF2 in M1-type BMDM.