HIF-1α activation occurs as a result of loss of vHL in certain forms of renal cell carcinoma, and HIF-1α controls VEGF and other angiogenic factors that are essential in support of tumor growth, which some considered potential risks of HIF-1 boosting therapy, however recent data indicates that activation of HIF-1 does not increase intestinal tumorigenesis [81]. This evidence concerns the gene HIF1A and hereditary clear cell renal cell carcinoma.