Recently, we extended the range of HIF-1 target genes by identifying the two tumour-associated transmembrane carbonic anhydrases (CA) CA9 (Opavsky et al, 1996; Ivanov et al, 1998) and CA12 (Ivanov et al, 1998; Tureci et al, 1998) as upregulated by hypoxia in a range of epithelial cancer cell lines (Wykoff et al, 2000). Here, CA9 is linked to neoplasm.