IGF1 and neoplasm: Early studies suggested that the most important source of CAFs could come from the resident NFs (17), especially the spindle-like fibroblasts surrounding tumors (so-called peritumor fibroblasts), and not the fibroblasts far away from tumor sites, with distinct characteristics of highly expressed α-SMA, CD90, IGF-1 (8,23,24) that can promote tumor growth and invasion (7,14).