title: Simultaneous modulation of COX-2, p300, Akt, and Apaf-1 signaling by melatonin to inhibit proliferation and induce apoptosis in breast cancer cells.
abstract: 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.
authors.affiliation: State Key Laboratory of Oncology in South China, Sun Yat-Sen University Cancer Center, Guangzhou, China.
authors.forename: Jingshu
authors.initials: J
authors.lastname: Wang
authors.forename: Xiangsheng
authors.initials: X
authors.lastname: Xiao
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Dingbo
authors.initials: D
authors.lastname: Shi
authors.forename: Wangbing
authors.initials: W
authors.lastname: Chen
authors.forename: Lingyi
authors.initials: L
authors.lastname: Fu
authors.forename: Liqun
authors.initials: L
authors.lastname: Liu
authors.forename: Fangyun
authors.initials: F
authors.lastname: Xie
authors.forename: Tiebang
authors.initials: T
authors.lastname: Kang
authors.forename: Wenlin
authors.initials: W
authors.lastname: Huang
authors.forename: Wuguo
authors.initials: W
authors.lastname: Deng
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053477:Apoptotic Protease-Activating Factor 1 / Q000096:biosynthesis* / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000096:biosynthesis* / Q000235:genetics; D015232:Dinoprostone / Q000096:biosynthesis; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D008550:Melatonin / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis* / Q000235:genetics; D050880:p300-CBP Transcription Factors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: C506592:APAF1 protein, human; D000975:Antioxidants; D053477:Apoptotic Protease-Activating Factor 1; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D050880:p300-CBP Transcription Factors; D051057:Proto-Oncogene Proteins c-akt; D020169:Caspases; D008550:Melatonin; D015232:Dinoprostone