Hepatitis B viral (HBV) persistent infection plays a significant role in hepatocellular carcinoma (HCC) tumorigenesis. Many studies have revealed the pivotal roles of N6-methyladenosine (m6A) in multiple cancers, while the regulatory mechanism in stemness maintenance of HBV persistent infection-related HCC remains elusive. Here, we demonstrated that the level of m6A modification was downregulated by HBV in HBV-positive HCC, through enhanced stability of ALKBH5 mRNA. More specifically, we also identified that ALKBH5 mRNA was functionally required for the stemness maintenance and self-renewal in the HBV-positive HCC, but dispensable in HBV-negative HCC. Mechanistically, ALKBH5 demethylated the m6A modification in the 3’UTR region of the oncogenic gene SNAI2 to prevent the recognition of YTHDF2 therewith stabilize SNAI2 transcripts, contributing to cancer stem cell traits in HBV-positive HCC. Moreover, the expression of SNAI2 reversed the suppression of stemness properties by knocking down ALKBH5. Additionally, ALKBH5/SNAI2 axis accelerates tumor immune evasion through activated ligand of immune checkpoint CD155. Our study unveiled that the ALKBH5 induces m6A demethylation of the SNAI2 as a key regulator in HBV-related HCC, and identifies the function of ALKBH5/SNAI2/YTHDF2 axis in promoting the stem-like cells phenotype and immune escape during HBV infection. Implications: HBV promotes hepatocellular carcinoma stemness maintenance through elevate m6A modification of SNAI2 in an ALKBH5-YTHDF2 dependent manner and increases the expression of the ligand of immune checkpoint CD155.

中文翻译：

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乙型肝炎病毒介导的 m6A 去甲基化增加肝细胞癌干性和免疫逃逸

乙型肝炎病毒（HBV）持续感染在肝细胞癌（HCC）肿瘤发生中起着重要作用。许多研究揭示了N6-甲基腺苷（m6A）在多种癌症中的关键作用，而HBV持续感染相关HCC干性维持的调节机制仍不清楚。在这里，我们证明，在 HBV 阳性 HCC 中，HBV 通过增强 ALKBH5 mRNA 的稳定性来下调 m6A 修饰水平。更具体地说，我们还发现 ALKBH5 mRNA 在 HBV 阳性 HCC 中是干性维持和自我更新所必需的，但在 HBV 阴性 HCC 中是可有可无的。从机制上讲，ALKBH5 使致癌基因 SNAI2 3'UTR 区域的 m6A 修饰去甲基化，以阻止 YTHDF2 的识别，从而稳定 SNAI2 转录本，从而有助于 HBV 阳性 HCC 中的癌症干细胞特征。此外，SNAI2 的表达通过敲低 ALKBH5 逆转了干性特性的抑制。此外，ALKBH5/SNAI2轴通过激活免疫检查点CD155的配体加速肿瘤免疫逃避。我们的研究揭示了 ALKBH5 诱导 SNAI2 的 m6A 去甲基化，作为 HBV 相关 HCC 的关键调节因子，并确定了 ALKBH5/SNAI2/YTHDF2 轴在 HBV 感染期间促进干细胞样细胞表型和免疫逃逸的功能。意义：HBV 通过 ALKBH5-YTHDF2 依赖性方式提高 SNAI2 的 m6A 修饰，并增加免疫检查点 CD155 配体的表达，从而促进肝细胞癌干性维持。