Previous work with non-RCC cells has indicated that although the large majority of hypoxia inducible genes are responsive to HIF-1α (Hu et al, 2003; Park et al, 2003; Sowter et al, 2003; Manalo et al, 2005; Wang et al, 2005), two distinct patterns of response are observed with some genes being exclusively responsive to HIF-1α and some responding to both HIF-1α and HIF-2α. This evidence concerns the gene HIF1A and renal cell carcinoma.