Abstract & Authors:展开
Background & Aims: N6-Methyladenosine (m6A) is the most prevalent RNA modification and recognized as an important epitranscriptomic mechanism in colorectal cancer (CRC). We aim to exploit whether and how tumor-intrinsic m6A modification drove by methyltransferase like 3 (METTL3) can dictate the immune landscape of CRC.
Methods: Mettl3 knockout mice, CD34+ humanized mice and different syngeneic mice models were employed. Immune cells composition and cytokines level were analyzed by flow cytometry and Cytokine 23-Plex immunoassay, respectively. M6A-seq and RNA-seq were performed to identify downstream targets and pathways of METTL3. Human CRC specimens (n=176) were used to evaluate correlation between METTL3 expression and myeloid-derived suppressor cells (MDSCs) infiltration.
Results: We demonstrated that silencing of METTL3 in CRC cells reduced MDSCs accumulation to sustain activation and proliferation of CD4+ and CD8+ T cell, and eventually suppressed CRC in ApcMin/+Mettl3+/- mice, CD34+ humanized mice and syngeneic mice models. Mechanistically, METTL3 activated m6A-BHLHE41-CXCL1 axis by analysis of m6A-seq, RNA-seq and cytokines arrays. METTL3 promoted BHLHE41 expression in m6A-dependent manner, which subsequently induced CXCL1 transcription to enhance MDSC migration in vitro. However, the effect was negligible upon BHLHE41 depletion, CXCL1 protein or CXCR2 inhibitor SB265610 administration, inferring that METTL3 promotes MDSC migration via BHLHE41-CXCL1/CXCR2. Consistently, depletion of MDSCs by anti-Gr1 antibody or SB265610 blocked tumor-promoting effect of METTL3 in vivo. Importantly, targeting METTL3 by METTL3-sgRNA or specific inhibitor potentiated the effect of anti-PD1 treatment.
Conclusions: Our study identifies METTL3 as a potential therapeutic target for CRC immunotherapy whose inhibition reverses immune suppression through m6A-BHLHE41-CXCL1 axis. METTL3 inhibition plus anti-PD-1 treatment show promising antitumor efficacy against CRC.
Huarong Chen,Yasi Pan,Qiming Zhou,Cong Liang,Chi Chun Wong,Yunfei Zhou,Dan Huang,Weixin Liu,Jianning Zhai,Hongyan Gou,Hao Su,Xiaoting Zhang,HongZhi Xu,Yifei Wang,Wei Kang,William Ka Kei Wu,Jun Yu