HGF and cancer: Three different types of A549 cancer cells have been used in their experiments, namely A549 (basal epithelial cells of a human alveolar adenocarcinoma), A549-HGF (A549 cells engineered to express hepatocyte growth factor (HGF) constitutively) and A549-HGF-M (a subgroup of the A549-HGF cells derived from a lung metastasis in a xenograft tumor).