MON-265 Regulation of Estrogen Receptor ⍺ and Tumor Suppressor gene BRCA1 by Tulsi (Ocimum sanctum) in Breast Cancer

Abstract Disclosure: R.R. Yaldo: None. A. Zanib: None. J.J. Koujane: None. N. Prudhomme: None. S.E. Pfiffner: None. I. Iskendar: None. E. Lumaj: None. S. Dinda: None. Tulsi (Ocimum sanctum), also known as holy basil, is a medicinal plant utilized in Hinduism that is widely recognized for its therapeutic properties. It has recently received attention in the scientific community for its antioxidant, anti-inflammatory, and tumor-suppressive effects. In the U.S., breast cancer incidence has been steadily rising, particularly among women under the age 50, with an increase of 1.4% per year, according to the American Cancer Society. Despite significant advances in early detection and treatment, breast cancer continues to be the second leading cause of cancer-related deaths in women. Given these alarming statistics, there is a critical need to explore novel and complementary therapeutic options. This study examined the impact of Tulsi, alone and in combination with hormones and anti-hormones, on ERα and BRCA1 expression in T-47D and MCF-7 breast cancer cells by utilizing western blot analyses, cellular viability assays, confocal microscopy, apoptosis assay, and RT-qPCR analyses. To eliminate endogenous steroids and growth factors, cells were maintained for six days in a medium supplemented with 5% fetal bovine serum (FBS) that had been treated with dextran-coated charcoal (DCC). To investigate how different concentrations of the compound influence cellular responses, cells were exposed to Tulsi at doses between 200 µM and 500 µM for 24 hours. Western blot analysis showed alterations in ERα and BRCA1 expression across the tested concentration range. The optimal concentration was determined to be 300 µM, as it resulted in the most pronounced upregulation of protein expression, indicating the maximal effect on these proteins. In both cell lines, expression of ERα and BRCA1 decreased relative to the control in a concentration dependent manner. Cells were then treated with the optimal concentration of 300 µM Tulsi alone or in combination with hormones and antihormones. Combination treatment of Tulsi with anti-hormones ICI and BZA revealed a significant decrease of ERα and BRCA-1 expression in both cell lines. Image cytometric analysis with propidium iodide staining was performed to examine the effects that Tulsi has on cellular viability in T-47D and MCF-7 cells. Following treatment for 6 days with 300 µM Tulsi, both cell lines displayed significantly decreased proliferation compared to the control and estrogen, results were resistant to additional hormone and antihormone treatment combinations. Ongoing research includes confocal microscopy to examine steroid receptor localization and RT-qPCR analysis to analyze gene expression. Our findings provide critical insights into the biochemical pathways through which Tulsi modulates steroid receptor activity and tumor suppressor gene expression in breast cancer cells, highlighting its potential anticancer properties. Presentation: Monday, July 14, 2025