Nonadhesive functions of E-cadherin promote cancer cell survival and metastasis.

E-cadherin suppresses invasion and promotes metastasis in invasive ductal breast cancer, through suppression of reactive oxygen species (ROS). We sought to determine the cellular source of apoptosis-inducing ROS and to identify the domains of E-cadherin that are essential for cancer cell survival. Inhibition of mitochondria-derived ROS was sufficient to rescue cell death following E-cadherin deletion, in both 3D colony formation and in vivo metastasis assays. We next generated Cdh1 constructs by mutating amino acids or deleting domains, then tested their ability to rescue colony formation in E-cadherin-deleted cells. Surprisingly, E-cadherin constructs in which the extracellular domains were deleted, adhesion was compromised, or catenin interactions were blocked could rescue elevated mitochondrial ROS and 3D colony formation. Conversely, a construct lacking the cytoplasmic domain was unable to rescue ROS or cell death. Our findings reveal that E-cadherin's ability to regulate mitochondrial ROS, cancer cell survival, and metastatic outgrowth is separable from its role in intercellular adhesion.