In order to study the role of cooperativity in HIF target selectivity, we determined the genome-wide pattern of HIF1 alpha binding sites in cervical carcinoma HeLa cells and compared our results to previously published HIF1 ChIP-chip experiments in hepatocellular carcinoma HepG2 cells [9], breast cancer MCF-7 cells [10] and U87 glioma cells [11], as detailed below. This evidence concerns the gene HIF1A and breast cancer.