Expression of transmembrane carbonic anhydrase isoenzymes IX and XII in normal human pancreas and pancreatic tumours

Carbonic anhydrase (CA) IX and XII are transmembrane isoenzymes which are e xpressed in several epithelia and overexpressed in some carcinomas. They ha ve recently been linked to von Hippel-Lindau gene-mediated carcinogenesis i n that both isoenzymes are downregulated by the product of the wild-type vo n Hippel-Lindau tumour suppressor gene. This paper de scribes the localisat ion of CA IX and XII in the normal human pancreas and pancreatic tumours. B oth isoenzymes showed positive reaction in the basolateral plasma membrane of the normal acinar and ductal epithelia. The hyperplastic ductal epitheli um in tumour specimens generally showed an increased staining for CA IX. Of 29 malignant tumours of exocrine pancreas, 10 showed moderate or strong im munoreaction for CA IX. The signal for CA XII remained weak in most maligna nt lesions. The present results show that both CA IX and XII are unevenly e xpressed in the ductal and acinar compartments of the human pancreas. The e xpression of these isoenzymes in a relatively low number of malignant tumou r specimens suggests that they have a limited value in diagnostic evaluatio n of pancreatic carcinoma. However, the increased expression of CA IX in hy perplastic ductal epithelium may contribute to the pancreatic tumourigenesi s.