HGF and colorectal carcinoma: Quantification of human HGF (h-HGF) protein secretion by ELISA illustrated that both parental and invasive CRC cell lines did not secrete physiologically detectable levels of h-HGF into the culture medium, indicating that overexpression and phosphorylation of c-MET in invasive cell lines is independent of autocrine-HGF secretion (Figure 1D).