FAP and cancer: Besides its expression in the tumor stroma, FAP expression is also upregulated in certain malignant tumor cells, such as glioblastoma (Busek et al., 2016), breast (Kelly et al., 1998), cervical (Jin et al., 2003), pancreatic (Shi et al., 2012), and colorectal (Iwasa et al., 2003) cancer cells.