KLF16 promotes immune escape in hepatocellular carcinoma cells by upregulating PD-L1 expression via PRKDC

Background Programmed death ligand 1 (PD-L1)-driven immune escape is a crucial mechanism in the progression of hepatocellular carcinoma (HCC). Furthermore, Krüppel-like factor 16 (KLF16) may be a key molecule that regulates this process. Therefore, the role of KLF16 in PD-L1-driven immune escape in HCC was investigated. Methods Hepa1–6 cells were subcutaneously injected into the right dorsum of BALB/c mice and nude mice to establish tumor-bearing models. The abundance of CD8+ T cells in tumor tissues was detected by flow cytometry. RT‒qPCR, Western blotting, immunofluorescence, and immunohistochemistry were used to analyze the expression of key genes and proteins. Results KLF16 is significantly highly expressed in HCC tissues and is associated with enrichment of the T-cell receptor signaling pathway. Knockdown of KLF16 inhibited PD-L1 expression in Hepa1–6 cells, whereas overexpression of KLF16 promoted PD-L1 expression. KLF16 knockdown significantly suppressed tumor growth, and the inhibitory effect was markedly stronger in immunocompetent mice than in nude mice. Additionally, KLF16 knockdown increased CD8+ T-cell infiltration in tumor-bearing tissues, as well as the number of granzyme B (GzmB)- and interferon-γ (IFN-γ)-positive CD8+ T cells, and enhanced the antitumor efficacy of combined anti-PD-1 and anti-CTLA-4 therapy. Mechanistically, KLF16 did not directly regulate PD-L1 transcription. Instead, KLF16 bound to the promoter of PRKDC (the gene encoding the catalytic subunit of DNA-dependent protein kinase, DNA-PK) and activated PRKDC transcription. The resulting elevation of DNA-PK then may phosphorylate PD-L1, thereby enhancing PD-L1 protein stability. Conclusion KLF16 promotes PD-L1 expression by transcriptionally activating PRKDC, promoting immune escape in HCC. KLF16 knockdown enhances the efficacy of immune checkpoint inhibitors, suggesting that KLF16 is a potential target for HCC immunotherapy.