A Ca2+-ATPase Regulates E-Cadherin Biogenesis and Epithelial-Mesenchymal Transition in Breast Cancer Cells

Progression of benign tumors to invasive, metastatic cancer is accompanied by the epithelial to mesenchymal transition (EMT), characterized by loss of the cell-adhesion protein E-cadherin. Although silencing mutations and transcriptional repression of the E-cadherin gene have been widely studied, not much is known about post-translational regulation of E-cadherin in tumors. We show that E-cadherin is tightly co-expressed with the secretory pathway Ca2+-ATPase isoform 2, SPCA2 (ATP2C2), in breast tumors. Loss of SPCA2 impairs surface expression of E-cadherin and elicits mesenchymal gene expression through disruption of cell adhesion in tumorspheres and downstream Hippo-YAP signaling. Conversely, ectopic expression of SPCA2 in triple negative breast cancer (TNBC) elevates baseline Ca2+ and YAP phosphorylation, enhances post-translational expression of E-cadherin, and suppresses mesenchymal gene expression. Thus, loss of SPCA2 phenocopies loss of E-cadherin in the Hippo signaling pathway and EMT-MET transitions, consistent with a functional role for SPCA2 in E-cadherin biogenesis. Furthermore, we show that SPCA2 suppresses invasive phenotypes, including cell migration in vitro and tumor metastasis in vivo. Based on these findings, we propose that SPCA2 functions as a key regulator of EMT and may be a potential therapeutic target for treatment of metastatic cancer. Implications: Post-translational control of E-cadherin and the Hippo pathway by calcium signaling regulates epithelial mesenchymal transition in breast cancer cells.