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Expression of carbonic anhydrase IX in breast is associated with malignant tissues and is related to overexpression of c-erbB2


  • According to the carbonic anhydrase nomenclature, human CA isoenzymes are written in capital roman letters and numbers, while their genes are written in italic letters and arabic numbers.


CA IX is a tumour-associated carbonic anhydrase with proposed roles in pH modulation and intercellular communication. Its distribution was examined in normal, benign and malignant breast tissues and compared with expression of breast tumour markers including oestrogen receptor, c-erbB2, c-erbB3 and CD44. Tissue specimens were analysed using immunohistochemistry and/or reverse transcriptase–polymerase chain reaction (RT-PCR). CA IX was detected by IHC in 12/26 (46%) malignant tissues, 4/36 (11%) benign lesions, but not in 10 normal breasts. Staining was mostly confined to plasma membranes of abnormal epithelial cells, but in five cases was found in adjacent stroma. Semi-quantitative RT-PCR detected CA9 mRNA in 25/39 (64%) malignant tumours, 11/33 (33%) benign lesions, but in none of three normal breasts. Comparative RT-PCR analysis of malignant tissues revealed a relationship between CA9 positivity and c-erbB2 overexpression (p=0.05). Moreover, CA9-positive specimens displayed a significantly higher median level of c-erbB2 than CA9-negative ones (p=0.02). No significant association was found with the other markers. The results of this study support the possible importance of CA IX for breast carcinogenesis and suggest its potential use as a breast tumour marker. Copyright © 2002 John Wiley & Sons, Ltd.

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