High tumour cell proliferation involves increased oxygen consumption, leading to oxygen deficiency and hypoxia-modulated gene expression, including activation of vascular endothelial growth factor and CA9 gene transcription by Hif-1α (Forsythe et al, 1996; Jiang et al, 1997; Maxwell et al, 1997; Carmeliet et al, 1998). The gene discussed is CA9; the disease is neoplasm.