F2RL1 and Familial prostate cancer: In addition, TMPRSS2 is abundantly expressed in the small intestine and in normal or carcinoid cells of the epithelial prostate and activates several substrates, including pro-hepatocyte growth factor/HGF, the protease-activated receptor-2/F2RL1, or matriptase/ST14, leading to disruption of the extracellular matrix and metastasis of prostate cancer cells [17].