Cadherins are cell-cell adhesion molecules. During tumor progression, their expression and/or function are frequently altered. E-cadherin down-regulation is often associated with tumor initiation and progression in breast cancer , whereas P-cadherin overexpression is associated with a worse patient survival  and with invasive breast cancer cells .
In this study, we aimed to understand if P-cadherin overexpression could interfere with E-cadherin invasion suppressor role in breast cancer.
Therefore, E- and P-cadherin expression was evaluated in a series of invasive breast carcinomas. P-cadherin overexpressing tumors often do not loose E-cadherin and tumors co-expressing both cadherins showed a more aggressive behavior and were related with the worst patient survival. Further, we performed in vitro studies by silencing both cadherins in BT-20 breast cancer cells. E- and P-cadherin co-expressing breast cancer cells showed increased cell invasion and migration capacities, when compared with the ones expressing only one cadherin. P-cadherin silencing led to increased levels of cell death, demonstrating it as a cancer cell survival signal. Also, microarrays of BT-20 cells, after E- and/or P-cadherin silencing, showed that the role of each cadherin alone is distinct from when these are co-expressed in the same cell, conferring different transcriptional programs.
We can conclude that E- and P-cadherin co-expression has an invasion promoter role in breast cancer cells and is a poor patient prognostic biomarker.
Paredes J, Albergaria A, Oliveira JT, Jerónimo C, Milanezi F, Schmitt FC: P-cadherin overexpression is an indicator of clinical outcome in invasive breast carcinomas and is associated with CDH3 promoter hypomethylation.
Paredes J, Stove C, Stove V, Milanezi F, Van Marck V, Derycke L, Mareel M, Bracke M, Schmitt F: P-cadherin is up-regulated by the antiestrogen ICI 182,780 and promotes invasion of human breast cancer cells.