HGF and prostate cancer: Stromal-derived factor-1 (SDF-1), epidermal growth factor (EGF), insulin-like growth factor (IGF), hepatocyte growth factor (HGF), Type I collagen, osteonectin and bone sialoprotein have been shown to act as chemoattractants for prostate cancer cells, predominantly causing them to gravitate towards the bone (Jacob et al., 1999[60]; Taichman et al., 2002[125]; Stewart et al., 2004[123]; Arya et al., 2006[15]).