The association of Jumonji domain-containing 6 (JMJD6) with the prognosis of various types of cancer has been demonstrated, except in intrahepatic cholangiocarci-noma (ICC). The present study aimed to clarify the impact of JMJD6 on ICC. The liver specimens of 51 patients who underwent surgery for ICC were analyzed for JMJD6 expression using immunohistochemistry staining. The relationship between clinicopathological factors and JMJD6 expression was investigated. The cellular activity was also evaluated in JMJD6 knocked down cells with Transwell migration assay and viability assay. In the immunohistochemistry staining of clinical samples, high expression of JMJD6 was seen in 32 of 51 samples. High expression was also associated with improved overall survival (OS) and recurrence-free survival (RFS) (P=0.0033 and 0.048, respectively). Further analyses revealed that higher JMJD6 expression was one of the improved independent prognostic factors of OS and RFS. Expression of JMJD6 was knocked down in commercial culture cell lines of ICC, and RNA and protein were extracted to analyze the downstream gene expression using RNA-sequencing and western blotting. JMJD6 knockdown was associated with higher programmed death-ligand 1 (PD-L1) expression in RNA-sequencing and western blotting. In addition, PD-L1 expression was higher in JMJD6 low expression clinical samples when measured using immunohistochemistry staining. In conclusion, high expression of JMJD6 was an independent favorable prognostic factor of ICC. JMJD6 may influence the prognosis of ICC through the regulation of PD-L1 expression.
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