Huarong Chen

as an oncogene in NAFLD-HCC and propose that repurposing SQLE inhibitors may be a promising approach for the prevention and treatment of NAFLD-HCC.

Background & AimsN6-Methyladenosine (m6A) is the most prevalent RNA modification and recognized as an important epitranscriptomic mechanism in colorectal cancer (CRC). We aimed to exploit whether and how tumor-intrinsic m6A modification driven by methyltransferase like 3 (METTL3) can dictate the immune landscape of CRC.MethodsMettl3 knockout mice, CD34+ humanized mice, and different syngeneic mice models were used. Immune cell composition and cytokine level were analyzed by flow cytometry and Cytokine 23-Plex immunoassay, respectively. M6A sequencing and RNA sequencing 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 cell (MDSC) infiltration.ResultsWe demonstrated that silencing of METTL3 in CRC cells reduced MDSC accumulation to sustain activation and proliferation of CD4+ and CD8+ T cells, and eventually suppressed CRC in ApcMin/+Mettl3+/− mice, CD34+ humanized mice, and syngeneic mice models. Mechanistically, METTL3 activated the m6A-BHLHE41-CXCL1 axis by analysis of m6A sequencing, RNA sequencing, and cytokine arrays. METTL3 promoted BHLHE41 expression in an m6A-dependent manner, which subsequently induced CXCL1 transcription to enhance MDSC migration in vitro. However, the effect was negligible on 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 the tumor-promoting effect of METTL3 in vivo. Importantly, targeting METTL3 by METTL3-single guide RNA or specific inhibitor potentiated the effect of anti–programmed cell death protein 1 (anti-PD1) treatment.ConclusionsOur study identifies METTL3 as a potential therapeutic target for CRC immunotherapy whose inhibition reverses immune suppression through the m6A-BHLHE41-CXCL1 axis. METTL3 inhibition plus anti-PD1 treatment shows promising antitumor efficacy against CRC. N6-Methyladenosine (m6A) is the most prevalent RNA modification and recognized as an important epitranscriptomic mechanism in colorectal cancer (CRC). We aimed to exploit whether and how tumor-intrinsic m6A modification driven by methyltransferase like 3 (METTL3) can dictate the immune landscape of CRC. Mettl3 knockout mice, CD34+ humanized mice, and different syngeneic mice models were used. Immune cell composition and cytokine level were analyzed by flow cytometry and Cytokine 23-Plex immunoassay, respectively. M6A sequencing and RNA sequencing 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 cell (MDSC) infiltration. We demonstrated that silencing of METTL3 in CRC cells reduced MDSC accumulation to sustain activation and proliferation of CD4+ and CD8+ T cells, and eventually suppressed CRC in ApcMin/+Mettl3+/− mice, CD34+ humanized mice, and syngeneic mice models. Mechanistically, METTL3 activated the m6A-BHLHE41-CXCL1 axis by analysis of m6A sequencing, RNA sequencing, and cytokine arrays. METTL3 promoted BHLHE41 expression in an m6A-dependent manner, which subsequently induced CXCL1 transcription to enhance MDSC migration in vitro. However, the effect was negligible on 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 the tumor-promoting effect of METTL3 in vivo. Importantly, targeting METTL3 by METTL3-single guide RNA or specific inhibitor potentiated the effect of anti–programmed cell death protein 1 (anti-PD1) treatment. Our study identifies METTL3 as a potential therapeutic target for CRC immunotherapy whose inhibition reverses immune suppression through the m6A-BHLHE41-CXCL1 axis. METTL3 inhibition plus anti-PD1 treatment shows promising antitumor efficacy against CRC.

Objective The role of N 6 -methyladenosine (m 6 A) in tumour immune microenvironment (TIME) remains understudied. Here, we elucidate function and mechanism of YTH N 6 -methyladenosine RNA binding protein 1 (YTHDF1) in colorectal cancer (CRC) TIME. Design Clinical significance of YTHDF1 was assessed in tissue microarrays (N=408) and TCGA (N=526) cohorts. YTHDF1 function was determined in syngeneic tumours, intestine-specific Ythdf1 knockin mice, and humanised mice. Single-cell RNA-seq (scRNA-seq) was employed to profile TIME. Methylated RNA immunoprecipitation sequencing (MeRIP-seq), RNA sequencing (RNA-seq) and ribosome sequencing (Ribo-seq) were used to identify YTHDF1 direct targets. Vesicle-like nanoparticles (VNPs)-encapsulated YTHDF1 -siRNA was used for YTHDF1 silencing in vivo. Results YTHDF1 expression negatively correlated with interferon-γ gene signature in TCGA-CRC. Concordantly, YTHDF1 protein negatively correlated with CD8 + T-cell infiltration in independent tissue microarrays cohorts, implying its role in TIME. Genetic depletion of Ythdf1 augmented antitumour immunity in CT26 (MSS-CRC) and MC38 (MSI-H-CRC) syngeneic tumours, while Ythdf1 knockin promoted an immunosuppressive TIME facilitating CRC in azoxymethane-dextran sulphate-sodium or Apc Min/+ models. scRNA-seq identified reduction of myeloid-derived suppressor cells (MDSCs), concomitant with increased cytotoxic T cells in Ythdf1 knockout tumours. Integrated MeRIP-seq, RNA-seq and Ribo-seq revealed p65/Rela as a YTHDF1 target. YTHDF1 promoted p65 translation to upregulate CXCL1, which increased MDSC migration via CXCL1-CXCR2 axis. Increased MSDCs in turn antagonised functional CD8 + T cells in TIME. Importantly, targeting YTHDF1 by CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) or VNPs-si YTHDF1 boosted anti-PD1 efficacy in MSI-H CRC, and overcame anti-PD1 resistance in MSS CRC. Conclusion YTHDF1 impairs antitumour immunity via an m 6 A-p65-CXCL1/CXCR2 axis to promote CRC and serves as a therapeutic target in immune checkpoint blockade therapy.