ICI 182,780 induces P-cadherin overexpression in breast cancer cells through chromatin remodelling at the promoter level: A role for C/EBPβ in CDH3 gene activation

CDH3/P-cadherin is a classical cadherin. Overexpression of which has been associated with proliferative lesions of high histological grade, decreased cell polarity and poor survival of patients with breast cancer. In vitro studies showed that it can be up-regulated by ICI 182,780, suggesting that the lack of ERα signalling is responsible for the aberrant P-cadherin overexpression and for its role in inducing breast cancer cell invasion and migration. However, the mechanism by which ER-signalling inhibition leads to P-cadherin expression is still unknown. The aim of this study was to explore the molecular mechanism linking the ERα-signalling and P-cadherin-regulated expression in breast cancer cell lines. This study showed that ICI 182,780 is able to increase CDH3 promoter activity, inducing high levels of the active chromatin mark H3 lysine 4 dimethylation. We also observed, for the first time, that the transcription factor C/EBPβ is able to up-regulate CDH3 promoter activity in breast cancer cells. Moreover, we showed that the expression of P-cadherin and C/EBPβ are highly associated in human breast carcinomas and linked with a worse prognosis of breast cancer patients. This study demonstrates the existence of an epigenetic regulation by which ICI 182,780 up-regulates P-cadherin expression in MCF-7/AZ breast cancer cells through chromatin remodelling at CDH3 promoter, bringing forward the growing evidence that ERα signalling-abrogation by anti-oestrogens is able to induce the expression of ERα-repressed genes which, in the appropriate cell biology context, may contribute to a breast cancer cell invasion phenotype.