SAT428 The Effects Of Diphenyl Phthalate (DP) On Estrogen Receptor Alpha (ERα;) And Tumor Suppressor Gene (BRCA-1) In Breast Cancer Cells

Disclosure: K. Whittaker: None. E. Hallman: None. A. Zanib: None. S. Pfiffner: None. R. Yaldo: None. S. Dinda: None. Phthalates are a group of compounds that have been linked to xenoestrogenic activity which can lead to the proliferation of breast cancer cells. Specifically, Diphenyl Phthalate (DP) is a compound found in cosmetics, toys, plastic containers, and medical equipment. Previous studies have linked phthalates as endocrine-disrupting compounds (EDC) which may have an effect on diseases such as breast cancer. Due to the endocrine-disrupting actions of phthalates, it is critical to further investigate DP’s potential impact on breast cancer cells. This study investigates the estrogen-like effects of DP, both alone and in combination with hormones and antihormones on T-47D and MCF-7 breast cancer cell lines. The breast cancer cells were cultured in a medium that contained 5% charcoal-stripped fetal bovine serum (FBS) to ensure depletion of any endogenous steroids or growth factors. The cells were treated with varying concentrations of DP (25-250uM) for 24 hours. Through western blot analysis, alterations in the expression of ERα; related to the varying concentrations of DP were observed. A concentration-dependent decrease of ERα; expression levels was observed in both cell lines when compared to the control. A concentration-dependent increase of BRCA1 was seen in both cells. The optimal concentration of DP was revealed to be 200uM in T-47D breast cancer cells as it exhibited the most estrogen-like effect. The optimal concentration (200uM) was then used alone and in combination with hormones and antihormones for further investigation of DP on T47-D cells. Treatment with DP, E(2) and the combination of DP and E(2) for 24 hours showed a significant down-regulation of ERα in T-47D cells when compared to the control. These effects were sensitive to the presence of ICI showing significant down-regulation of ERα (approximately 80%) in T-47D cells. Image cytometric analysis with propidium iodide staining was utilized to examine the effects of DP on cellular viability in T-47D cells. Cells were treated for 6 days with DP concentrations ranging from 25-250 µM, and all concentrations displayed an increase in cell proliferation compared to the control in T47D cells. DP alone and in combination with E(2) showed an increase in cell proliferation that was reversed when treated in combination with anti-hormones. RT-qPCR studies in T-47D cells revealed a transcriptional expression of ESR1 and BRCA-1 mRNA levels that correlate with the translational data from western blot analyses. Confocal microscopy, cell viability, and RT-qPCR analyses are in progress as well as evaluation on the effects of DP with hormones and antihormones on MCF-7 cells. Our studies offer an intriguing direction to explore the molecular mechanisms of DP as an EDC on the steroid receptors and tumor suppressor gene in breast cancer cells. Presentation: Saturday, June 17, 2023