HGF and malignant mesothelioma: Many growth factors, such as insulin-like growth factor-1 (IGF-1) [16,59], hepatocyte growth factor (HGF) [44,60], basic fibroblast growth factor (b-FGF) [61], TNF-α [62], EGF [14,63], VEGF [14,64-68] and platelet-derived growth factor (PDGF) A and B [69], have been implicated in the development and progression of malignant mesothelioma.