m6A RNA methylation-mediated upregulation of HLF promotes intrahepatic cholangiocarcinoma progression by regulating the FZD4/β-catenin signaling pathway

Hepatic leukemia factor (HLF) is aberrantly expressed in human malignancies. However, its role in regulating intrahepatic cholangiocarcinoma (ICC) remains unclear. This study aimed to define the role of HLF in ICC progression. Here, we showed that HLF expression is upregulated in ICC and predicts the poor prognosis in patients. Mechanistically, HLF activation in ICC is mediated by METTL3-dependent m6A methylation of the HLF mRNA. As per the results from the loss- or gain-of-function experiments, HLF promoted the self-renewal, tumorigenicity, proliferation and metastasis of ICC cells. RNA-seq and CUT&Tag analyses showed that frizzled-4 (FZD4) and forkhead box Q1 (FOXQ1) are target genes of HLF. Moreover, FOXQ1 transcriptionally activates METTL3 expression, forming a positive feedback loop, which subsequently activates WNT/β-catenin signaling and downstream tumor stemness. Furthermore, HLF expression was positively correlated with METTL3, IGF2BP3, FZD4 and FOXQ1 expression in ICC tissues in a large ICC cohort. The combined IHC panels exhibited a better prognostic value for patients with ICC than any of these components alone. In conclusions, these findings demonstrated that the METTL3/HLF/FOXQ1 regulatory circuit drove FZD4-mediated WNT/β-catenin activation in ICC progression, suggesting that targeting this axis could be novel therapeutic strategy for ICC.