E-cadherin is required for metastasis in multiple models of breast cancer

Metastasis is the major driver of death in patients with cancer. Invasion of surrounding tissues and metastasis have been proposed to initiate following loss of the intercellular adhesion protein, E-cadherin(1,2), on the basis of inverse correlations between in vitro migration and E-cadherin levels(3). However, this hypothesis is inconsistent with the observation that most breast cancers are invasive ductal carcinomas and express E-cadherin in primary tumours and metastases(4). To resolve this discrepancy, we tested the genetic requirement for E-cadherin in metastasis using mouse and human models of both luminal and basal invasive ductal carcinomas. Here we show that E-cadherin promotes metastasis in diverse models of invasive ductal carcinomas. While loss of E-cadherin increased invasion, it also reduced cancer cell proliferation and survival, circulating tumour cell number, seeding of cancer cells in distant organs and metastasis outgrowth. Transcriptionally, loss of E-cadherin was associated with upregulation of genes involved in transforming growth factor-beta (TGF beta), reactive oxygen species and apoptosis signalling pathways. At the cellular level, disseminating E-cadherin-negative cells exhibited nuclear enrichment of SMAD2/3, oxidative stress and increased apoptosis. Colony formation of E-cadherin-negative cells was rescued by inhibition of TGF beta-receptor signalling, reactive oxygen accumulation or apoptosis. Our results reveal that E-cadherin acts as a survival factor in invasive ductal carcinomas during the detachment, systemic dissemination and seeding phases of metastasis by limiting reactive oxygen-mediated apoptosis. Identifying molecular strategies to inhibit E-cadherin-mediated survival in metastatic breast cancer cells may have potential as a therapeutic approach for breast cancer.