Calpain regulates sensitivity to trastuzumab and survival in HER2-positive breast cancer

• Published in: Oncogene Vol. 29; no. 9; pp. 1339 - 1350
• Main Authors: Kulkarni, S, Reddy, K B, Esteva, F J, Moore, H C F, Budd, G T, Tubbs, R R
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04-03-2010; Nature Publishing Group
• Subjects: AKT1 protein; Antibodies, Monoclonal - pharmacology; Antibodies, Monoclonal - therapeutic use; Antibodies, Monoclonal, Humanized; Apoptosis; Biological and medical sciences; Breast cancer; Breast Neoplasms - pathology; Calpain; Calpain - pharmacology; Catalysis; Cell Biology; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Chemotherapy; Cysteine proteinase; Drug Resistance, Neoplasm; Drug therapy; ErbB-2 protein; Female; Fibroblast growth factor 2; Fundamental and applied biological sciences. Psychology; Genetic aspects; Genetics; Gynecology. Andrology. Obstetrics; Human Genetics; Humans; Internal Medicine; Mammary gland diseases; Medical sciences; Medicine; Medicine & Public Health; Molecular and cellular biology; Mutation; Oncology; original-article; Physiological aspects; Protein Kinase Inhibitors - pharmacology; PTEN protein; Sensitivity and Specificity; Therapeutic targets; Trastuzumab; Tumors; United States; calpain; AKT1; HER2; resistance; survival; Antineoplastic agent; Breast disease; Enzyme; Cysteine endopeptidases; Calpain; Breast cancer; Malignant tumor; Carcinogenesis; Survival; Immunomodulator; Resistance; Mammary gland diseases; Peptidases; Regulation(control); Sensitivity; C-Onc gene; Hydrolases; Trastuzumab; Cancer
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/onc.2009.422

Resistance to anti-HER2 (human epithelial growth factor receptor 2) trastuzumab therapy occurs commonly in HER2-positive breast cancer and involves overactivation of HER2 and/or AKT1. Using the model of trastuzumab-sensitive or trastuzumab-resistant HER2-positive cells with wild-type PTEN, negative regulator of AKT1, we explore the involvement of cysteine protease calpain in mechanisms of trastuzumab resistance. Overexpression of calpain1 or activation of endogenous calpain during adhesion or trastuzumab treatment of trastuzumab-sensitive cells induces cleavage of cytoplasmic domains of HER2/phospho-HER2; cleavage occurs in HER2-positive tumors. Expression of the catalytically inactive mutant of calpain1 reduces the cleavage to enhance the activity of HER2, inactivates PTEN to enhance the activation of AKT1, induces desensitization to trastuzumab and promotes survival of trastuzumab-sensitive cells. In the model of trastuzumab resistance, constitutive overactivation of HER2 and AKT1 correlates with reduced activation of calpain. Moreover, inhibitors of the catalytic site of calpain reduce the increase in constitutive activity of AKT1 and survival of trastuzumab-resistant cells selectively. Together, by regulating the activation of HER2 and PTEN/AKT1, calpain regulates trastuzumab sensitivity and survival, and the deregulation of the activation of calpain promotes trastuzumab resistance. Trastuzumab-resistant cells activate AKT1 in a mechanism dependent on the residual calpain activity, inhibition of which restores trastuzumab sensitivity and rescues resistance. These data identify calpain as a new therapeutic target in HER2-positive breast cancer.