EPO and renal cell carcinoma: Under hypoxic conditions, or when the VHL gene is mutated or lost, HIFs accumulate, leading to increased expression of genes encoding vascular endothelial growth factor (VEGFA), platelet derived growth factor (PDGF), transforming growth factor-α (TGFα), erythropoietin (EPO), as well as receptors potentially important in RCC oncogenesis [4].