Expression analysis of epithelial cadherin and related proteins in IBH-6 and IBH-4 human breast cancer cell lines.

Epithelial cadherin (E-cadherin) is a 120 kDa cell-cell adhesion molecule involved in the establishment of epithelial adherens junctions. It is connected to the actin cytoskeleton by adaptor proteins such as beta-catenin. Loss of E-cadherin expression/function has been related to tumor progression and metastasis. Several molecules associated with down-regulation of E-cadherin have been described, within them neural cadherin, Twist and dysadherin. Human breast cancer cell lines IBH-6 and IBH-4 were developed from ductal primary tumors and show characteristic features of malignant epithelial cells. In this study expression of E-cadherin and related proteins in IBH-6 and IBH-4 cell lines was evaluated. In IBH-6 and IBH-4 cell extracts, only an 89 kDa E-cadherin form (Ecad89) was detected, which is truncated at the C-terminus and is present at low levels. Moreover, no accumulation of the 86 kDa E-cadherin ectodomain and of the 38 kDa CTF1 fragment was observed. IBH-6 and IBH-4 cells showed an intracellular scattered E-cadherin localization. beta-catenin accompanied E-cadherin localization, and actin stress fibers were identified in both cell types. E-cadherin mRNA levels were remarkably low in IBH-6 and IBH-4 cells. The E-cadherin mRNA and genomic sequence encoding exons 14-16 could not be amplified in either cell line. Neither the mRNA nor the protein of neural cadherin and dysadherin were detected. Up-regulation of Twist mRNA was found in both cell lines. In conclusion, IBH-6 and IBH-4 breast cancer cells show down-regulation of E-cadherin expression with aberrant protein localization, and up-regulation of Twist; these features can be related to their invasive/metastatic characteristics.