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.

Effects of Melatonin on Nervous System Aging: Neurogenesis and Neurodegeneration

“…The expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) is regulated by NF-kB and inhibited by melatonin (59). In addition to NF-kB suppression, the enzyme COX-2, which converts arachidonic acid to prostaglandin H2 in inflammation and tumorigenesis, is suppressed by melatonin (61). COX-2 is distributed in specific areas of the brain, including the hippocampus, and is involved in learning and memory (62).…”

“…The CBP/P300 complex recruits a number of transcriptional co-activators, such as NF-kB, CREB, and nuclear factor erythroid 2-related factor 2 (Nrf-2), for transcription (59). Melatonin suppresses P300 HAT activity (60) and thereby NF-kB acetylation and binding to the promoters of some inflammatory genes (61). The expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) is regulated by NF-kB and inhibited by melatonin (59).…”

Melatonin-Induced Oncostasis, Mechanisms and Clinical Relevance

“…Therefore, COX-2 inhibitors can be important anticancer agents and, additionally, act additively with chemotherapy. Again, the action of melatonin in repressing the expression of COX-2 may account for its oncostatic effects [36].…”

Perspectives of Melatonin Use in Clinical Oncology

“…Таким образом, МЛТ обладает большим количеством функций в организме. В последние годы наибольший интерес вызывает противоопухолевая активность этого биогенного амина, которая показана в опытах in vitro/in vivo [10][11][12][13][14]. МЛТ обладает способ-ностью потенцировать эффект цитостатиков и оказывает значительное влияние на иммунную систему [15,16].…”

“…МЛТ обладает способ-ностью потенцировать эффект цитостатиков и оказывает значительное влияние на иммунную систему [15,16]. Это достигается благодаря различным механизмам сдержи-вания опухолевого роста -активации и переориентации иммунного ответа в сторону Т-хелперов 1 типа и увели-чению продукции ряда цитокинов (IL-2, IFN-, интерлей-кина-6) [17,18], снижению экспрессии VEGF рецептора [19], активации апоптоза в опухолевых клетках [20][21][22][23], уменьшению активности теломеразы [24]. Прослежена корреляция между противоопухолевым действием МЛТ и уровнем экспрессии МТ 1 рецепторов в клетках опухо-ли [24].…”