HCG18 Promotes Cell Proliferation and Stemness in Cholangiocarcinoma via the miR-194-5p/KRT18/MAPK Signaling.

Accumulating evidence has demonstrated that Keratin18 (KRT18) functions as a pivotal gene in the progression of various cancers. However, its role in cholangiocarcinoma (CCA) remains unexplored. Our study elucidated the biological functions and underlying mechanisms of KRT18 in CCA. Bioinformatic databases were used to identify potential miRNAs and lncRNAs. The cellular localization of KRT18 and lncRNA HCG18 was examined through subcellular fractionation. Expression levels of genes were assessed by qRT-PCR, while protein levels were measured via western blot. Cell viability was analyzed using CCK-8 assays. Colony formation and EdU assays assessed cell proliferation, and sphere formation assays evaluated stem cell properties. The interactions between HCG18, miR-194-5p, and KRT18 were explored through RNA immunoprecipitation, RNA pulldown, and luciferase reporter assays. A xenograft tumor model was conducted to evaluate the in vivo function. In CCA tissues and cell lines, KRT18 expression was elevated. Functionally, silencing KRT18 reduced cell proliferation and stemness and inhibited cell cycle. Mechanistically, miR-194-5p directly targeted KRT18. HCG18, which was upregulated in CCA, interacted with miR-194-5p. Overexpression of KRT18 negated the effects of HCG18 suppression on CCA cell proliferation and stemness. Activation of MAPK signaling reversed the antitumor effects of KRT18 downregulation on CCA in vitro. Moreover, HCG18 was found to activate MAPK signaling through the miR-194-5p/KRT18 pathway. The in vivo assay demonstrated that HCG18 knockdown inhibited tumor growth by the miR-194-5p/KRT18/MAPK axis. HCG18 can promote cell proliferation and stem cell characteristics in CCA through the miR-194-5p/KRT18/MAPK signaling.