PCP4 and cholangiocarcinoma: The mean optical density of the expression of BUB1, BUB1B, PCP4 and VSNIL1 in the CCA and adjacent tissue samples showed that the protein levels of BUB1, BUB1B, and PCP4 in the CCA tissue were significantly increased, but the protein level of VSNL1 in the CCA tissue was significantly decreased (Figure 8).