CXCL1 and neoplasm: At this point, hypoxia occurs and the angiogenic process is activated through the well-known hypoxia-inducible transcription factors (HIF) that induce the expression of several tumour-derived cytokines, such as vascular endothelial growth factors (VEGF) or fibroblast growth factors (FGF) [6] and some chemokines (GRO, CXCL9, and CXCL10) with their respective receptors (CXCR2 and CXCR3) [8, 13, 14].