CA9 has previously been reported to be induced by HIF-1α alone in all cell types (Grabmaier et al, 2004; Raval et al, 2005), whereas PHD3 had been demonstrated to be regulated by both HIF-1α and HIF-2α in non-RCC cells, but had not been studied in this way in RCC cells (Aprelikova et al, 2004). This evidence concerns the gene CA9 and renal cell carcinoma.