PRKD2 and cholangiocarcinoma: Specifically, three PK members of the protein kinase D (PKD) family, PRKD1, PRKD2, and PRKD3, were experimentally validated as oncogenic roles in CCA with the small interfering RNAs (siRNAs) and a selective inhibitor, 1-naphthyl PP1 (1-NA-PP1).