Melatonin inhibits aromatase promoter expression by regulating cyclooxygenases expression and activity in breast cancer cells

Abstract

BACKGROUND: Melatonin reduces the development of breast cancer interfering with oestrogen-signalling pathways, and also inhibits aromatase activity and expression. Our objective was to study the promoters through which melatonin modifies aromatase expression, evaluate the ability of melatonin to regulate cyclooxygenases and assess whether the effects of melatonin are related to its effects on intracellular cAMP, in MCF-7 cells. METHODS: Total aromatase mRNA, aromatase mRNA promoter regions and cyclooxygenases mRNA expression were determined by real-time RT -PCR. PGE 2 and cAMP were measured by kits. RESULTS: Melatonin downregulated the gene expression of the two major specific aromatase promoter regions, pII and pI.3, and also that of the aromatase promoter region pI.4. Melatonin 1 nM was able to counteract the stimulatory effect of tetradecanoyl phorbol acetate on PGE 2 production and inhibit COX-2 and COX-1 mRNA expression. Melatonin 1 nM elicited a parallel time-dependent decrease in both cyclic AMP formation and aromatase mRNA expression. CONCLUSIONS: This study shows that melatonin inhibits aromatase activity and expression by regulating the gene expression of specific aromatase promoter regions. A possible mechanism for these effects would be the regulation by melatonin of intracellular cAMP levels, mediated by an inhibition of cyclooxygenase activity and expression.

Melatonin suppresses aromatase expression and activity in breast cancer associated fibroblasts

“…In this study, we show that MLT actions on BAFs are not promoter-specific and suppress each of the three promoters expressed. This data correlates with what is observed in MCF-7 cells despite the subtle differences in modes of PII transcriptional activation by alternative transcription factors in the two different cell types [14,20]. Elevated levels of PI.4 in CAFs are due to elevated levels of class I cytokines and glucocorticoids within the tumor c Aromatase activity following PGE 2 (1 lM) stimulation alone or in combination with MLT (1 nM).…”

“…The secretion of PGE 2 by breast tumor epithelial cells is associated with the increased tumor PII-derived transcriptional activity in surrounding BAFs through both cAMP/PKA-and PKC-dependent signaling and the activation of a number of transcription factors [3]. As MLT is known to decrease intracellular concentrations of cAMP [14], we tested the ability of MLT to suppress PGE 2 PIIstimulation in BAFs. PGE 2 increased PII-derived CYP19A1 mRNA *3.5-fold compared to vehicle (Fig.…”

“…ER and PR immunoreactivity was evaluated according to Allred et al [29]. HER2 immunoreactivity was evaluated based on the CAP-ASCO guideline [30] PS proportional score, IS intensity score, TS total score cAMP levels and downstream targets in different cell types including MCF-7 cells [14]. While elevated PGE 2 in the microenvironment, driven by increases in COX-2 expression in tumor epithelial cells, acts on CAFs predominantly in a paracrine manner, up-regulation of COX-2 in the stroma may also serve as a mechanism of PGE 2 autocrine action to stimulate PII.…”

“…Physiological concentrations of MLT have been shown to reduce aromatase expression and activity in the ER-positive breast cancer derived cell line MCF-7 [13,14]. However, it is acknowledged that CAFs, not epithelial cells, are the abundant source of elevated CYP19A1 mRNA in postmenopausal breast cancer [15].…”

Night Shifts and Melatonin: Relevance to Age and Breast Cancer

“…Furthermore melatonin inhibits aromatase activity by regulating the gene expression of specifi c aromatase promoter regions (Martínez-Campa et al 2009 ). Indeed suppression of CYP19A1 mRNA gene transcription by melatonin results in a signifi cant decrease in cytochrome P450, family 19, subfamily A, polypeptide 1 (CYP19A1)-related aromatase activity.…”