Protective effects of melatonin against bisphenol A-mediated endometrial tumorigenesis: An experimental study targeting COX-2-dependent MMP-9 expression

Bisphenol A (BPA), a widespread environmental endocrine disruptor, contributes to the development of endometrial carcinogenesis by activating the cyclooxygenase-2 (COX-2)/matrix metalloproteinase-9 (MMP-9) axis. In this study, the protective effects of melatonin on BPA-induced protumorigenic alterations were evaluated in the human endometrial carcinoma cell line RL95-2.

RL95-2 cells were treated with BPA (10^-7 M) alone or in combination with varying concentrations of melatonin (10^-10 to 10^-4 M) for 24 h. An MTT assay was performed to assess cell viability. RT-PCR and Western blotting were performed to evaluate COX-2 and MMP-9 expression. Immunofluorescence and flow cytometry were performed to analyze protein localization and quantify the COX-2⁺/MMP-9⁺ cell population. Cells were treated with NS-398, a selective COX-2 inhibitor, to validate COX-2 dependency.

BPA significantly increased RL95-2 cell proliferation and upregulated COX-2 and MMP-9 expression. Melatonin cotreatment, particularly at 10^-6 M, suppressed BPA-induced proliferation and attenuated both COX-2 and MMP-9 expression at the gene and protein levels. Flow cytometry revealed that BPA significantly increased the proportion of COX-2⁺/MMP-9⁺ cells. Both melatonin and NS-398 reversed this effect. These findings highlight the capacity of melatonin to mitigate BPA-induced proliferation and invasiveness by suppressing COX-2-mediated MMP-9 expression.

Melatonin effectively mitigated BPA-induced proliferation and proinflammatory and proinvasive RL95-2 phenotypes by targeting the COX-2/MMP-9 signaling axis. These findings support the potential of melatonin as a physiologically safe therapeutic agent for preventing endometrial tumorigenesis induced by environmental endocrine disruptors, underscoring its anti-inflammatory relevance in reproductive oncology.