Carbonic anhydrase inhibitor suppresses invasion of renal cancer cells in vitro

Acidification of the extracellular milieu of malignant tumors is reported t o increase the invasive behavior of cancer cells. In normal tissues, produc tion of acid is catalyzed by carbonic anhydrases (CAs), some of which are k nown to be overexpressed in certain cancers. To investigate the functional role of CA activity in such cancer cells, we analyzed the effect of acetazo lamide, a potent CA inhibitor, on the invasive capacity of four renal carci noma cell lines (Caki-1, Caki-2, ACHN, and A-498). We found that 10 mu M ac etazolamide inhibited the relative invasion rate of these cell lines betwee n 18-74%. The Caki-2 and ACHN cell lines displayed the highest responsivene ss, and their responses clearly depended on the acetazolamide concentration in the culture medium. Immunocytochemical and Western blotting results ide ntified the presence of CA isoenzyme II in the cytoplasm of all four cell l ines and CA XII on the plasma membrane in three of four cell lines. Because acetazolamide alone reduced invasiveness of these cancer cells in vitro, w e conclude that the CAs overexpressed in these renal cancer cells contribut e to invasiveness, at least in vitro, and suggest that CA inhibitors may al so reduce invasiveness in other tumors that overexpress one or more CAs.