PPBP and cholangiocarcinoma: In vitro studies showed that CXCL7 and CXCR2 were highly expressed in CC cell lines HuCCT1, HuH28, QBC939, EGI-1, OZ and WITT, and overexpression or knockdown of CXCL7 promoted or inhibited proliferation and invasion of CC cells, respectively, suggesting that CXCL7 can act in an autocrine mode in tumors (Guo et al., 2017).