title: Calpain Genetic Disruption and HSP90 Inhibition Combine To Attenuate Mammary Tumorigenesis.
abstract: Calpain is an intracellular Ca(2+)-regulated protease system whose substrates include proteins involved in proliferation, survival, migration, invasion, and sensitivity to therapeutic drugs. Genetic disruption of calpain attenuated the tumorigenic potential of breast cancer cells and hypersensitized cells to 17AAG, an inhibitor of the molecular chaperone HSP90. Calpain-1 or -2 overexpression rendered cells resistant to 17AAG, whereas downregulation or inhibition of calpain-1/2 led to increased cell death in multiple breast cancer cell lines, including models of HER2(+) (SKBR3) and triple-negative basal-cell-like (MDA-MB-231) breast cancer. In an MDA-MB-231 orthotopic xenograft model, calpain knockdown or 17AAG treatment independently attenuated tumor growth and metastasis, while the combination was most effective. Calpain knockdown was associated with increased 17AAG-induced degradation of the HSP90 clients cyclin D1 and AKT and multidrug resistance protein 2, which correlated with increased expression of antimitogenic p27(KIP1) and proapoptotic BIM proteins. Like other therapeutics, 17AAG can be effluxed by specific ABC transporters. Calpain expression positively correlated with the expression of P glycoprotein in mouse embryonic fibroblasts. Importantly, we show that calpain affects ABC transporter function and efflux of clinically relevant doxorubicin. These observations provide a compelling rationale for exploring the combination of calpain inhibition with new or existing cancer therapeutics.
authors.affiliation: Division of Cancer Biology and Genetics, Queen's University, Kingston, ON, Canada Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada.
authors.forename: Stacy
authors.initials: S
authors.lastname: Grieve
authors.affiliation: Division of Cancer Biology and Genetics, Queen's University, Kingston, ON, Canada.
authors.forename: Yan
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Division of Cancer Biology and Genetics, Queen's University, Kingston, ON, Canada.
authors.forename: Christine
authors.initials: C
authors.lastname: Hall
authors.affiliation: Division of Cancer Biology and Genetics, Queen's University, Kingston, ON, Canada Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada.
authors.forename: Jing
authors.initials: J
authors.lastname: Hu
authors.affiliation: Division of Cancer Biology and Genetics, Queen's University, Kingston, ON, Canada Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada greerp@queensu.ca.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Greer
mesh_terms: D000818:Animals; D016227:Benzoquinones / Q000008:administration & dosage* / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics; D002154:Calpain / Q000235:genetics*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003131:Combined Modality Therapy; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques / Q000379:methods*; D006801:Humans; D047029:Lactams, Macrocyclic / Q000008:administration & dosage* / Q000494:pharmacology; D051379:Mice; D009362:Neoplasm Metastasis; D023041:Xenograft Model Antitumor Assays
chemical_list: D016227:Benzoquinones; D047029:Lactams, Macrocyclic; C112765:tanespimycin; D002154:Calpain; C484806:CAPN1 protein, human; C569870:CAPN2 protein, human