Kynurenine promotes the immune escape of colorectal cancer cells via NAT10-mediated ac(4)C acetylation of PD-L1.

BACKGROUND: This study aimed to investigate the role of kynurenine in Colorectal Cancer (CRC) and the underlying mechanism. METHODS: Enzyme-linked immunosorbent assay was employed to assess the kynurenine concentration. Flow cytometry was utilized to analyze the percentages of CD3+CD4+ and CD3+CD8+ T-cells. Immunofluorescence was used to measure the expression of Programmed Death-Ligand 1 (PD-L1). RNA modification levels in CRC cells were analyzed using a dot blot assay. The interaction between NAT10 and PD-L1 was assessed via RNA immunoprecipitation, dual-luciferase reporter, and immunofluorescence assays. A xenograft tumor rat model was established. RESULTS: Results indicated that kynurenine suppressed T-cell activation and promoted immune escape. Besides, kynurenine promoted N-Acetyltransferase 10 (NAT10)-mediated N4-acetylcytidine (ac(4)C) modification. Moreover, NAT10 inhibition improved T-cell activation and suppressed immune escape. Mechanically, NAT10 is bound with the mRNA of PD-L1. Rescue experiments showed that PD-L1 inhibitor treatment reversed the suppressed T-cell activation and the promoted immune escape induced by NAT10 overexpression. In vivo, studies indicated that NAT10 deficiency reversed the promoted tumor growth induced by kynurenine treatment. CONCLUSION: In conclusion, kynurenine promoted the immune escape of CRC cells via NAT10-mediated ac(4)C acetylation of PD-L1.