DOWN-REGULATION OF TRANSMEMBRANE CARBONIC-ANHYDRASES IN RENAL-CELL CARCINOMA CELL-LINES BY WILD-TYPE VON-HIPPEL-LINDAU TRANSGENES

To discover genes involved in von Hippel-Lindau (VHL)-mediated carcino genesis, we used renal cell carcinoma cell lines stably transfected wi th wild-type VHL-expressing transgenes, Large-scale RNA differential d isplay technology applied to these cell lines identified several diffe rentially expressed genes, including an alpha carbonic anhydrase gene, termed CA12. The deduced protein sequence was classified as a one-pas s transmembrane CA possessing an apparently intact catalytic domain in the extracellular CA module. Reintroduced wild-type VHL strongly inhi bited the overexpression of the CA12 gene in the parental renal cell c arcinoma cell lines. Similar results were obtained with CA9, encoding another transmembrane CA with an intact catalytic domain. Although bot h domains of the VHL protein contribute to regulation of CA12 expressi on, the elongin binding domain alone could effectively regulate CA9 ex pression. We mapped CA12 and CA9 loci to chromosome bands 15q22 and 17 q21,2 respectively, regions prone to amplification in some human cance rs. Additional experiments are needed to define the role of CA IX and CA XII enzymes in the regulation of pH in the extracellular microenvir onment and its potential impact on cancer cell growth.