HGF and small cell lung carcinoma: Approximately 20 years ago, Rygaard et al. [57], evaluating a panel of 25 SCLC cell lines and xenografts, detected the expression of c-MET mRNA transcripts and c-MET protein in 88% of SCLC tumors; conversely, only two showed HGF mRNA levels and the co-expression of c-MET receptor/HGF was found in only one tumor.