Caveolin-1 is down-regulated and inversely correlated with HER2 and EGFR expression status in invasive ductal carcinoma of the breast.

AIMS: To evaluate the caveolin-1 status of invasive ductal carcinoma and its correlation with other important parameters of breast carcinogenesis. Caveolin-1, the main structural protein of caveolae, is involved in the regulation of several intracellular signalling pathways and also functions as a tumour suppressor in breast carcinogenesis.

METHODS AND RESULTS: One hundred and thirty cases of invasive ductal carcinomas with matched normal breast tissue were evaluated immunohistochemically for caveolin-1 expression. Using a tissue microarray, caveolin-1 expression was also correlated with the expression of other antigens such as eostrogen receptor, progesterone receptor, epidermal growth factor receptor (EGFR), HER2, beta-catenin, E-cadherin, p53, Ki67 and with clinicopathological parameters. Immunohistochemical results showed strong expression of caveolin-1 in all normal breast epithelial cells, but a reduction of caveolin-1 expression in 56 cases (43.1%) of invasive ductal carcinoma. Furthermore, a statistically significant inverse correlation between caveolin-1 and EGFR and HER2 was noted (P < 0.001).

CONCLUSIONS: Our results indicate a reduction in caveolin-1 expression in invasive ductal carcinoma of the breast, which supports in vitro studies of its role as a tumour suppressor. Caveolin-1 also shows an inverse correlation with EGFR and HER2, which fits with its function as a negative regulator of signal transduction.