Simultaneous modulation of COX-2, p300, Akt, and Apaf-1 signaling by melatonin to inhibit proliferation and induce apoptosis in breast cancer cells

• Published in: Journal of pineal research 2012-08, Vol.53 (1), p.77-90
• Main Authors: Wang, Jingshu, Xiao, Xiangsheng, Zhang, Yun, Shi, Dingbo, Chen, Wangbing, Fu, Lingyi, Liu, Liqun, Xie, Fangyun, Kang, Tiebang, Huang, Wenlin, Deng, Wuguo
• Format: Article
• Language: English
• Subjects: Akt; Antioxidants - pharmacology; Apaf-1; Apoptosis - drug effects; Apoptotic Protease-Activating Factor 1 - biosynthesis; Apoptotic Protease-Activating Factor 1 - genetics; breast cancer; Breast Neoplasms - genetics; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Caspases - genetics; Caspases - metabolism; Cell Line, Tumor; Cell Proliferation - drug effects; COX-2; Cyclooxygenase 2 - biosynthesis; Cyclooxygenase 2 - genetics; Dinoprostone - biosynthesis; Female; Gene Expression Regulation, Neoplastic - drug effects; Humans; melatonin; Melatonin - pharmacology; p300; p300-CBP Transcription Factors - biosynthesis; p300-CBP Transcription Factors - genetics; Proto-Oncogene Proteins c-akt - biosynthesis; Proto-Oncogene Proteins c-akt - genetics
• ISSN: 0742-3098; 1600-079X
• DOI: 10.1111/j.1600-079X.2012.00973.x

:  Melatonin exhibits anti‐inflammatory and anticancer effects and could be a chemopreventive and chemotherapeutic agent against cancers, but the precise mechanisms involved remain largely unresolved. In this study, we evaluated the mechanism of action of melatonin in human MDA‐MB‐361 breast cancer cells. Melatonin at pharmacological concentrations (10−3 m) significantly suppressed cell proliferation and induced apoptosis in a dose‐dependent manner. The observed suppression of proliferation was accompanied by the melatonin‐mediated inhibition of COX‐2, p300, and NF‐κB signaling. Melatonin significantly inhibited COX‐2 expression and prostaglandin E(2) (PGE2) production, abrogated p300 histone acetyltransferase activity and p300‐mediated NF‐κB acetylation, thereby blocking NF‐κB binding and p300 recruitment to COX‐2 promoter. Pretreatment with a COX‐2‐ or p300‐selective inhibitor abrogated the melatonin‐induced inhibition of cell proliferation, whereas PGE2 treatment or COX‐2 transfection reversed the inhibition by melatonin. Moreover, melatonin markedly inhibited phosphorylation of PI3K, Akt, PRAS40, and GSK‐3 proteins, thereby inactivating the PI3K/Akt signaling pathway. Pretreatment with a PI3K‐ or an Akt‐selective inhibitor or an Akt‐specific siRNA blocked the melatonin‐mediated inhibition of cell proliferation. Conversely, gene delivery of a constitutively active Akt effectively reversed the inhibition by melatonin. Furthermore, melatonin induced Apaf‐1 expression, triggered cytochrome C release, and stimulated caspase‐3 and caspase‐9 activities and cleavage, leading to an activation of the Apaf‐1‐dependent apoptotic pathway. Pretreatment with an Apaf‐1‐specific siRNA effectively attenuated the melatonin‐induced apoptosis. These results therefore indicate that melatonin inhibits cell proliferation and induces apoptosis in MDA‐MB‐361 breast cancer cells in vitro by simultaneously suppressing the COX‐2/PGE2, p300/NF‐κB, and PI3K/Akt/signaling and activating the Apaf‐1/caspase‐dependent apoptotic pathway.