Hepatitis B virus X protein promotes the progression and immune escape of hepatocellular carcinoma by activating KLF16-C12orf49-PD-L1 axis

Hepatocellular carcinoma (HCC) is a common and serious type of malignant tumor with an unfavorable prognosis, partly attributed to the prevalence of hepatitis B virus (HBV) infection. However, the molecular mechanism underlying HBV-HCC are not yet fully understood. Here, we found that Kruppel-like factor 16 (KLF16) was significantly upregulated in HBV-HCC and KLF16 knockdown suppressed the growth and metastasis of HBV-infected HCC cells. Hepatitis B virus X protein (HBx)-mediated N6-methyladenosine (m6A) modification of KLF16 mRNA promoted the binding of insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) and IGF2BP3, thereby enhancing the stability of KLF16 mRNA. Furthermore, KLF16 was found to promote the transcription of chromosome 12 open reading frame 49 (C12orf49), which in turn increased programmed death-ligand 1 (PD-L1) expression by competitively binding to speckle-type POZ protein (SPOP) and blocking SPOP-mediated ubiquitination and degradation of PD-L1. HBx contributed to immune escape in HBV-HCC through the KLF16-C12orf49-PD-L1 axis. Importantly, inhibiting KLF16 significantly improved the efficacy of anti-PD-L1 therapy in HBV-HCC. Collectively, our study reveals the newly identified HBx-KLF16-C12orf49-PD-L1 axis and its role in promoting growth and immune evasion in HBV-HCC, offering a promising target for clinical interventions in HBV-HCC treatment.