Downregulation of ER60 Protease Inhibits Cellular Proliferation by Inducing G1/S Arrest in Breast Cancer Cells In Vitro

Abstract

ER60 protease, a 58-kDa molecular chaperone in the endoplasmic reticulum, is involved in glycoprotein synthesis. ER60 protease has been reported to be differentially expressed in various cancers including breast carcinoma. This study explored the relationship of ER60 protease with cell proliferation in breast cancer in vitro. ER60 protease expression was first determined in a panel of breast cell lines by real-time RT-PCR and Western blot analysis and found to be most abundantly expressed in T47D breast cancer cells. The ER60 protease gene was then successfully knocked down in T47D breast cancer cells using two different sequences of small-interfering RNA. The silencing efficiencies of siER-1 and siER-2 at 48-hr post-transfection were found to be >80% at the mRNA level with concomitant downregulation of the ER60 protease protein by >60% when compared with control T47D breast cancer cells. Downregulation of ER60 protease was also associated with inhibition of cell proliferation when assessed by the AlamarBlue assay. Cell cycle analysis performed on the siER-1- and siER-2-transfected cells, revealed an increase in G1 phase population and a decrease in the S and G2/M phase populations compared with control cells, implicating G1/S cell cycle arrest. It would appear that ER60 protease is involved in breast tumorigenesis and could therefore be a prospective target for cancer therapeutics. © 2012 Wiley Periodicals, Inc.