IGF1 and neoplasm: HIF-1α is a core molecule that induces tumor angiogenesis and can directly regulate vascular endothelial growth factor (VEGF) expression at the gene level [30] or indirectly regulate the expression of angiogenic factors such as epidermal growth factor receptor (EGFR), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), and insulin-like growth factor (IGF) via cyclooxygenase 2 (COX2) to promote tumor angiogenesis [31].