HGF and cancer: The additional possibility that multiple copies of HGF and MET genes might amplify through a chronology of autonomous circular DNA replication, double-minute chromosome formation and chromosomal integration, as described for other cancer-associated gene amplification events [39,40,41], prompted us to perform fluorescence in situ hybridization (FISH) to visualize HGF and MET genes in the parental and resistant cell lines (Figure 6C,D).