Fat mass and obesity-associated protein (FTO) is an enzyme that demethylates N6-methyladenosine (m⁶A), the most abundant RNA modifications in a cell. The upregulated expression of FTO promotes the progression of various types of cancer by modulating cell-intrinsic genes which relate to malignant potential. However, the impact of FTO on the expression of immune-checkpoint molecules in the tumor cells, which are important for immune escape, has not been well understood. We examined the relevance of FTO to programmed cell death-ligand 1 (PD-L1) expression in colon cancer cells. HCT-116 cells showed high expression of both FTO and PD-L1 proteins. The knockdown of FTO by small interfering RNA decreased mRNA and protein levels of PD-L1 in HCT-116 cells. To elucidate the underlying mechanism by which FTO regulates the expression of PD-L1, we depleted FTO in HCT-116 in the presence of IFN-γ, which is a major stimulus to upregulate PD-L1 expression. Depletion of FTO reduced PD-L1 expression in an IFN-γ signaling-independent manner. RNA immunoprecipitation assay revealed the m⁶A modification of the PD-L1 mRNA and the binding of FTO to the PD-L1 mRNA in HCT-116. Taken together, our results indicated that FTO could regulate PD-L1 expression in colon cancer cells and provides new insights into the regulation of PD-L1 expression by RNA modification.

脂肪量和肥胖相关蛋白 (FTO) 是一种酶，可将 N6-甲基腺苷 (m ⁶A)，细胞中最丰富的 RNA 修饰。FTO 的上调表达通过调节与恶性潜能相关的细胞内在基因来促进各种类型癌症的进展。然而，FTO 对肿瘤细胞中免疫检查点分子表达的影响，这对免疫逃逸很重要，尚未得到很好的理解。我们检查了 FTO 与结肠癌细胞中程序性细胞死亡配体 1 (PD-L1) 表达的相关性。HCT-116 细胞显示 FTO 和 PD-L1 蛋白的高表达。小干扰 RNA 对 FTO 的敲低降低了 HCT-116 细胞中 PD-L1 的 mRNA 和蛋白质水平。为了阐明 FTO 调节 PD-L1 表达的潜在机制，我们在存在 IFN-γ 的情况下耗尽了 HCT-116 中的 FTO，这是上调 PD-L1 表达的主要刺激因素。FTO 的消耗以与 IFN-γ 信号无关的方式降低了 PD-L1 的表达。RNA 免疫沉淀分析揭示了 m⁶ HCT-116 中PD-L1 mRNA 的修饰和 FTO 与PD-L1 mRNA的结合。总之，我们的结果表明 FTO 可以调节结肠癌细胞中 PD-L1 的表达，并为通过 RNA 修饰调节 PD-L1 表达提供了新的见解。