title: Cisplatin Induces Apoptosis Through the Endoplasmic Reticulum-mediated, Calpain 1 Pathway in Triple-negative Breast Cancer Cells.
abstract: Breast cancer is the most common cancer in women worldwide. Triple-negative breast cancer (TNBC) is an aggressive type that can be treated using platinum-based chemotherapy such as cisplatin (cis-diamminedichloroplatinum II). Although the calpain protein is essential in many cellular processes, including apoptosis, cell signaling, and proliferation, its role in cisplatin-induced apoptosis in TNBC cells is not fully understood. The present study assessed calpain 1-dependent, cisplatin-induced apoptosis in TNBC cells.
  
  
  
  MDA-MB231 cells were treated with different concentrations of cisplatin (0, 20, and 40 μM). The cisplatin deposit and its effect on endoplasmic reticulum and, subsequently, calcium release were detected using transmission electron microscopy and Von Koss staining, respectively. Calpain 1 messenger RNA, protein content, and apoptosis was measured using reverse transcriptase-polymerase chain reaction, Western blotting, and Hoechst stain, respectively. In addition, calpain modulation, by either activation or inhibition, and its effect on cisplatin-induced apoptosis were assessed.
  
  
  
  Our results showed that cisplatin induced endoplasmic reticulum stress, indicated by an increase in calcium staining and protein expression of glucose-regulated protein 78 and calmodulin, followed by cleavage of α-fodrin and caspase-12 and, eventually, apoptosis. Cyclopiazonic acid showed a similar effect and enhanced the sensitivity of these cells to cisplatin treatment. In contrast, calpain 1 inhibition by both specific small interfering RNA and exogenous inhibitor (calpeptin) attenuated cisplatin-induced apoptosis in these cells.
  
  
  
  Altogether, these findings suggest, for the first time, that calpain 1 activation by endoplasmic reticulum plays an essential role in sensitizing TNBC cells to cisplatin-induced apoptosis. This finding will allow exploration of new insights for the treatment of TNBC by overcoming its resistance to apoptosis.
authors.affiliation: Department of Allied Health Sciences, College of Medicine and Health Sciences, Sultan Qaboos University, Al Khoud, Sultanate of Oman. Electronic address: bahlani@squ.edu.om.
authors.forename: Shadia M
authors.initials: SM
authors.lastname: Al-Bahlani
authors.affiliation: Department of Pathology, College of Medicine and Health Sciences, Sultan Qaboos University, Al Khoud, Sultanate of Oman.
authors.forename: Khadija H
authors.initials: KH
authors.lastname: Al-Bulushi
authors.affiliation: Department of Pathology, College of Medicine and Health Sciences, Sultan Qaboos University, Al Khoud, Sultanate of Oman.
authors.forename: Zaina M
authors.initials: ZM
authors.lastname: Al-Alawi
authors.affiliation: Department of Pathology, College of Medicine and Health Sciences, Sultan Qaboos University, Al Khoud, Sultanate of Oman.
authors.forename: Nadia Y
authors.initials: NY
authors.lastname: Al-Abri
authors.affiliation: Department of Pathology, College of Medicine and Health Sciences, Sultan Qaboos University, Al Khoud, Sultanate of Oman.
authors.forename: Zuweina R
authors.initials: ZR
authors.lastname: Al-Hadidi
authors.affiliation: Department of Pathology, College of Medicine and Health Sciences, Sultan Qaboos University, Al Khoud, Sultanate of Oman.
authors.forename: Shaikha S
authors.initials: SS
authors.lastname: Al-Rawahi
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D015398:Signal Transduction / Q000187:drug effects*; D064726:Triple Negative Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D002154:Calpain; C484806:CAPN1 protein, human; D002945:Cisplatin; D002118:Calcium
keywords: Breast cancer; Calcium-dependent proteases; Electron microscope; Programmed cell death; Western blot