Under hypoxic conditions, the hypoxia-inducible factor (HIF-1α) pathway is activated to promote the release of vascular endothelial growth factor and platelet-derived growth factor, inducing endothelial cells from the original tumor blood vessels to proliferate, bud, and generate new tumor blood vessels, allowing tumors to invade and metastasize. The gene discussed is VEGFA; the disease is neoplasm.