非酒精性脂肪性肝病（NAFLD）是肝细胞癌（HCC）的新兴危险因素。然而，NAFLD-HCC的机制和靶向治疗仍然不明确。在这里，我们确认了N6-甲基腺苷（m6A）甲基转移酶METTL3促进NAFLD-HCC的作用。肝细胞特异性Mettl3敲入加剧了小鼠NAFLD-HCC的形成，而Mettl3敲除则产生相反的效果。单细胞RNA测序发现，METTL3通过减少肿瘤抗性机制相关基因粒内酶B（GZMB +）和干扰素γ阳性（IFN-γ +）CD8 + T细胞浸润，抑制了抗肿瘤免疫反应，从而促进了免疫逃逸。在机制上，METTL3介导甾体调节元件结合蛋白（SREBP）剪切活化蛋白（SCAP）mRNA的m6A修饰以促进其翻译，从而激活胆固醇生物合成。这导致胆固醇和胆固醇酯的增加分泌，从而损害了肿瘤微环境中的CD8 + T细胞功能。通过单导RNA、纳米颗粒小干扰RNA（siRNA）或药物抑制剂（STM2457）靶向METTL3与抗程序性细胞死亡蛋白1（PD-1）联合使用，可以协同增强细胞毒性CD8 + T细胞的活力，并介导肿瘤的退化。综上所述，METTL3是NAFLD-HCC的治疗靶点，尤其是与免疫检查点阻断（ICB）治疗相结合。版权所有 © 2023 作者。由 Elsevier Inc.出版。保留所有权利。

Non-alcoholic fatty liver disease (NAFLD) is an emerging risk factor of hepatocellular carcinoma (HCC). However, the mechanism and target therapy of NAFLD-HCC are still unclear. Here, we identify that the N6-methyladenosine (m6A) methyltransferase METTL3 promotes NAFLD-HCC. Hepatocyte-specific Mettl3 knockin exacerbated NAFLD-HCC formation, while Mettl3 knockout exerted the opposite effect in mice. Single-cell RNA sequencing revealed that METTL3 suppressed antitumor immune response by reducing granzyme B (GZMB+) and interferon gamma-positive (IFN-γ+) CD8+ T cell infiltration, thereby facilitating immune escape. Mechanistically, METTL3 mediates sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP) mRNA m6A to promote its translation, leading to the activation of cholesterol biosynthesis. This enhanced secretion of cholesterol and cholesteryl esters that impair CD8+ T cell function in the tumor microenvironment. Targeting METTL3 by single-guide RNA, nanoparticle small interfering RNA (siRNA), or pharmacological inhibitor (STM2457) in combination with anti-programmed cell death protein 1 (PD-1) synergized to reinvigorate cytotoxic CD8+ T cells and mediate tumor regression. Together, METTL3 is a therapeutic target in NAFLD-HCC, especially in conjunction with immune checkpoint blockade (ICB) therapy.Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.