N⁶-Methyladenosine (m⁶A) is a important process regulating gene expression post-transcriptionally. Programmed death ligand 1 (PD-L1) is a major immune inhibitive checkpoint that facilitates immune evasion and is expressed in tumor cells. In this research we discovered that Wilms' tumor 1-associated protein (WTAP) degradation caused by ubiquitin-mediated cleavage in cancer cells (colorectal cancer, CRC) under hypoxia was inhibited by Pumilio homolog 1 (PUM1) directly bound to WTAP. WTAP enhanced PD-L1 expression in a way that was m⁶A-dependent. m⁶A “reader,” Insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) identified methylated PD-L1 transcripts and subsequently fixed its mRNA. Additionally, we found that T-cell proliferation and its cancer cell-killing effects were prevented by overexpression of WTAP in vitro and in vivo. Overexpression prevented T cells from proliferating and killing CRC by maintaining the expression of PD-L1. Further evidence supporting the WTAP–PD-L1 regulatory axis was found in human CRC and organoid tissues. Tumors with high WTAP levels appeared more responsive to anti-PD1 immunotherapy, when analyzing samples from patients undergoing treatment. Overall, our findings demonstrated a novel PD-L1 regulatory mechanism by WTAP-induced mRNA epigenetic regulation and the possible application of targeting WTAP as immunotherapy for tumor hypoxia.

中文翻译：

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WTAP 诱导的 PD-L1 N6-甲基腺苷在结直肠癌缺氧条件下阻断 T 细胞介导的抗肿瘤活性

N ⁶ -甲基腺苷(m ⁶ A)是转录后调节基因表达的重要过程。程序性死亡配体 1 (PD-L1) 是一种主要的免疫抑制检查点，可促进免疫逃避并在肿瘤细胞中表达。在这项研究中，我们发现，在缺氧条件下，癌细胞（结直肠癌，CRC）中泛素介导的裂解引起的 Wilms 肿瘤 1 相关蛋白（WTAP）降解受到直接与 WTAP 结合的 Pumilio 同源物 1（PUM1）的抑制。 WTAP 以 m ⁶ A 依赖性方式增强 PD-L1 表达。 m ⁶ “阅读器”胰岛素样生长因子 2 mRNA 结合蛋白 2 (IGF2BP2) 识别出甲基化的 PD-L1 转录物，并随后固定其 mRNA。此外，我们发现 WTAP 在体外和体内的过度表达可以阻止 T 细胞增殖及其癌细胞杀伤作用。过度表达通过维持 PD-L1 的表达来阻止 T 细胞增殖并杀死 CRC。在人类结直肠癌和类器官组织中发现了支持 WTAP-PD-L1 调节轴的进一步证据。在分析接受治疗的患者样本时，WTAP 水平高的肿瘤似乎对抗 PD1 免疫疗法更敏感。总体而言，我们的研究结果证明了 WTAP 诱导的 mRNA 表观遗传调控的新型 PD-L1 调控机制，以及靶向 WTAP 作为肿瘤缺氧免疫疗法的可能应用。