PRKD2 and cholangiocarcinoma: Interestingly, the top three PKs, PRKD1, PRKD2, and PRKD3, which belong to the protein kinase D (PKD) family of the calcium/calmodulin-dependent kinase (CAMK) group, showed a consistently strong effect on the proliferation inhibition of CCA cells (Figure 5C–E).