N6‐methyladenosine (m⁶A) is an abundant nucleotide modification in mRNA , known to regulate mRNA stability, splicing, and translation, but it is unclear whether it is also has a physiological role in the intratumoral microenvironment and cancer drug resistance. Here, we find that METTL 3, a primary m⁶A methyltransferase, is significantly down‐regulated in human sorafenib‐resistant hepatocellular carcinoma (HCC ). Depletion of METTL 3 under hypoxia promotes sorafenib resistance and expression of angiogenesis genes in cultured HCC cells and activates autophagy‐associated pathways. Mechanistically, we have identified FOXO 3 as a key downstream target of METTL 3, with m⁶A modification of the FOXO 3 mRNA 3′‐untranslated region increasing its stability through a YTHDF 1‐dependent mechanism. Analysis of clinical samples furthermore showed that METTL 3 and FOXO 3 levels are tightly correlated in HCC patients. In mouse xenograft models, METTL 3 depletion significantly enhances sorafenib resistance of HCC by abolishing the identified METTL 3‐mediated FOXO 3 mRNA stabilization, and overexpression of FOXO 3 restores m⁶A‐dependent sorafenib sensitivity. Collectively, our work reveals a critical function for METTL 3‐mediated m⁶A modification in the hypoxic tumor microenvironment and identifies FOXO 3 as an important target of m⁶A modification in the resistance of HCC to sorafenib therapy.

中文翻译：

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RNA m6 A 甲基化通过 FOXO3 介导的自噬调节肝癌中的索拉非尼耐药性。

N6-甲基腺苷 (m ⁶ A) 是 mRNA 中丰富的核苷酸修饰，已知可调节 mRNA 的稳定性、剪接和翻译，但尚不清楚它是否在肿瘤内微环境和癌症耐药性中也具有生理作用。在这里，我们发现 METTL 3，一种主要的 m ⁶ A 甲基转移酶，在人索拉非尼耐药肝细胞癌 (HCC) 中显着下调。缺氧条件下 METTL 3 的消耗促进索拉非尼耐药性和培养的 HCC 细胞中血管生成基因的表达，并激活自噬相关通路。从机制上讲，我们已将 FOXO 3 确定为 METTL 3 的关键下游目标，其中 m ⁶FOXO 3 mRNA 3' 非翻译区的修饰通过 YTHDF 1 依赖性机制增加其稳定性。临床样本分析进一步表明，METTL 3 和 FOXO 3 水平在 HCC 患者中密切相关。在小鼠异种移植模型中，METTL 3 耗竭通过消除已鉴定的 METTL 3 介导的 FOXO 3 mRNA 稳定性显着增强 HCC 的索拉非尼耐药性，并且 FOXO 3 的过表达恢复了 m ⁶ A 依赖性索拉非尼敏感性。总的来说，我们的工作揭示了 METTL 3 介导的 m ⁶ A 修饰在缺氧肿瘤微环境中的关键功能，并将 FOXO 3 确定为 m ⁶ A 修饰在 HCC 对索拉非尼治疗的耐药性中的重要靶点。