Overexpression of E-cadherin protein in metastatic breast cancer cells in bone

The aim of the present study was to evaluate E-cadherin, whose expression remains poorly understood in the intercellular adhesion of metastatic breast cancer cells in bone, the most prevalent site for metastatic growth.

An immunohistochemical staining method was used for the localization of E-cadherin protein in tissue biopsy specimens of normal breast (n = 9) and well- (n = 8), moderately (n = 8) or poorly (n = 14) differentiated invasive primary breast cancer and metastatic breast cancer in bone (n = 17). The expression patterns of E-cadherin were classified as homogeneous (most cells exhibiting positivity), heterogeneous (a few scattered patches of cells with positivity) or negative (cells with undetectable positivity).

Normal breast epithelial cells showed homogeneous overexpression of E-cadherin in all cases. A progressive and statistically significant reduction of E-cadherin expression was detected in the histologically well- to moderately to poorly differentiated breast cancer cells (p < 0.001). The clumps of invasive primary breast cancer cells in CD-31-positive blood vessels exhibited E-cadherin expression. Moreover, as compared to the poorly differentiated breast cancer cells, a significantly increased frequency of the metastatic breast cancer cells in bone exhibited homogeneous expression of E-cadherin in 15 out of 17 and heterogeneous expression in the remaining 2 cases (McNemar Exact p < 0.001). This is the first demonstration of membranous overexpression of E-cadherin on metastatic breast cancer cells in bone; the high frequency of its expression may have a role in the intercellular adhesion of metastatic cells in bone.