Over-expression of fibroblast activation protein alpha increases tumor growth in xenografts of ovarian cancer cells

Fibroblast activation protein alpha (FAP) is a 95-kDa serine protease of post-prolyl peptidase family on cell surface. FAP is widely expressed in tumor microenvironment. The wide spread association of FAP expression with cancer suggests that it has important functions in the disease. However, the nature of FAPs roles in cancer cell activity is not well-determined. It has been showed that FAP silencing in SKOV3 cells induces ovarian tumors but significantly reduces tumor growth in a xenograft mouse model. To further determine the role of FAP in epithelial ovarian cancer cells, SKOV3-FAP and HO8910-FAP cell lines, which over-expressed FAP stably, were constructed and then their biological behaviors were investigated. It was found that FAP promoted ovarian cancer cell proliferation, drug resistance, invasiveness, and migration in vitro. Immunochemistry assay showed that FAP significantly facilitated tumor growth in xenograft tumor tissues. These results suggested that FAP might directly promote tumor growth and invasiveness in ovarian cancer cells.