Esculetin, a natural coumarin compound, evokes Ca(2+) movement and activation of Ca(2+)-associated mitochondrial apoptotic pathways that involved cell cycle arrest in ZR-75-1 human breast cancer cells.
Esculetin (6,7-dihydroxycoumarin), a derivative of coumarin compound, is found in traditional medicinal herbs. It has been shown that esculetin triggers diverse cellular signal transduction pathways leading to regulation of physiology in different models. However, whether esculetin affects Ca(2+) homeostasis in breast cancer cells has not been explored. This study examined the underlying mechanism of cytotoxicity induced by esculetin and established the relationship between Ca(2+) signaling and cytotoxicity in human breast cancer cells. The results showed that esculetin induced concentration-dependent rises in the intracellular Ca(2+) concentration ([Ca(2+)]i) in ZR-75-1 (but not in MCF-7 and MDA-MB-231) human breast cancer cells. In ZR-75-1 cells, this Ca(2+) signal response was reduced by removing extracellular Ca(2+) and was inhibited by the store-operated Ca(2+) channel blocker 2-aminoethoxydiphenyl borate (2-APB). In Ca(2+)-free medium, pre-treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin (TG) abolished esculetin-induced [Ca(2+)]i rises. Conversely, incubation with esculetin abolished TG-induced [Ca(2+)]i rises. Esculetin induced cytotoxicity that involved apoptosis, as supported by the reduction of mitochondrial membrane potential and the release of cytochrome c and the proteolytic activation of caspase-9/caspase-3, which were partially reversed by pre-chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA-AM). Moreover, esculetin increased the percentage of cells in G2/M phase and regulated the expressions of p53, p21, CDK1, and cyclin B1. Together, in ZR-75-1 cells, esculetin induced [Ca(2+)]i rises by releasing Ca(2+) from the ER and causing Ca(2+) influx through 2-APB-sensitive store-operated Ca(2+) entry. Furthermore, esculetin activated Ca(2+)-associated mitochondrial apoptotic pathways that involved G2/M cell cycle arrest. Graphical abstract The summary of esculetin-evoked [Ca(2+)]i rises and -activated Ca(2+)-associated mitochondrial apoptotic pathways that involved cell cycle arrest. The natural coumarin derivative esculetin caused Ca(2+) influx via 2-APB-sensitive store-operated Ca(2+) entry and induced Ca(2+) release from the endoplasmic reticulum. Moreover, esculetin activated the mitochondrial pathway of apoptosis in a Ca(2+)-associated manner that involved G2/M arrest.
Department of Surgery, Kaohsiung Veterans General Hospital, Kaohsiung, 813, Taiwan, Republic of China.
Hong-Tai
HT
Chang
Department of Nursing, Division of Basic Medical Sciences, Chang Gung University of Science and Technology, Chia-Yi, 613, Taiwan.|Chronic Diseases and Health Promotion Research Center, Chang Gung University of Science and Technology, Chia-Yi, 613, Taiwan.
Chiang-Ting
CT
Chou
Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, 813, Taiwan.
You-Sheng
YS
Lin
Department of Pharmacy, Tajen University, Pingtung, 907, Taiwan.
Pochuen
P
Shieh
Department of Pharmacy, Tajen University, Pingtung, 907, Taiwan.
Daih-Huang
DH
Kuo
Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, 813, Taiwan.
Chung-Ren
CR
Jan
Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, 813, Taiwan. lianggoole67@gmail.com.
Wei-Zhe
WZ
Liang
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy; D002118:Calcium; D020013:Calcium Signaling; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D004354:Drug Screening Assays, Antitumor; D005260:Female; D059585:G1 Phase Cell Cycle Checkpoints; D006801:Humans; D020128:Inhibitory Concentration 50; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria; D014468:Umbelliferones / Q000494:pharmacology*
D000972:Antineoplastic Agents, Phytogenic; D018797:Cell Cycle Proteins; D014468:Umbelliferones; C007628:esculetin; D002118:Calcium
Ca2+; Cell cycle; Esculetin; Human breast cancer cells; Mitochondrial apoptotic pathway