E-cadherin promotor methylation and mutation are inversely related to motility capacity of breast cancer cells

Inactivation of the tumor suppressor E-cadherin is an important event during breast tumorigenesis, as its decreased expression is linked to aggressiveness and metastasis. However, the relationship between the different modes of E-cadherin inactivation (mutation versus promotor hypermethylation) and breast cancer cell behavior is incompletely understood. The high correlation between E-cadherin inactivation status and cell morphology in vitro suggests different biological roles for the two inactivation modes during breast tumorigenesis. Because E-cadherin has been linked to cell invasion and metastasis, and cell motility is a crucial prerequisite to form metastases, we here compared the cell motility capacities of breast cancer cell lines with known E-cadherin status. Using barrier migration assays and time-lapse microscopy, we analyzed the migratory capacity of nine well-characterized human breast cancer cell lines (MDA-MB-231, MCF-7, T47D, BT549, MPE600, CAMA-1, SUM159PT, SUM52PE, and SK-BR-3). This subset was chosen based on E-cadherin gene status (wild-type, mutated, and promotor hypermethylated): three cell lines of each group. In addition, cell proliferation assays were performed for all conditions, to dissect migratory from proliferative effects. In this study, we demonstrate an overt association between the mode of E-cadherin inactivation and cell migration. Promotor hypermethylated E-cadherin cell lines showed a higher migration capacity, while cell lines with mutated E-cadherin were less motile compared to wild-type E-cadherin cell lines. Migration induction by fibronectin and basic fibroblast growth factor did not alter the cell motility association differences. Cell proliferation assays showed that the associations found were not caused by proliferation differences. Inhibition and overexpression of E-cadherin as well as DNA demethylation confirmed the relationship between E-cadherin and breast cancer cell motility. Our results demonstrate an association between the mode of E-cadherin inactivation and migration of breast cancer cells, which justifies more detailed research on the role of E-cadherin inactivation in cell migration and metastasis.