Abstract 954: Combined treatment of γ-tocotrienol, and vitamin D3 synergistically inhibits breast cancer cell proliferation, migration, and epithelial-to-mesenchymal transition (EMT)

Abstract

Abstract Metastatic breast cancer is a leading cause of death of women in the United States. The metastatic process involves epithelial cells losing their cellular polarity, adhesion to the basement membrane, and acquiring migratory and invasive properties. Metastatic epithelial cells take on a mesenchymal phenotype, hence this process is termed epithelial-to-mesenchymal transition (EMT). EMT is characterized by a reduction in epithelial cell marker expression (E-cadherin, cytokeratin 8, and cytokeratin 18), and an increased expression of mesenchymal cell markers (N-cadherin, vimentin, and fibronectin). Previous studies have demonstrated that dietary intake of γ-tocotrienol and/or vitamin D3 may provide benefit in the preventing the growth and development of metastatic breast cancer. γ-Tocotrienol is a natural isoform of vitamin E that shows potent anticancer activity against a variety of cancer cell types at treatment doses that have little or no effect on normal cell growth or viability. Vitamin D3 has also been shown to display potent antiproliferative and antiangiogenic activity against human breast cancer cells, particularly triple negative breast cancers. Studies were conducted here to examine the effects of γ-tocotrienol and vitamin D3 given alone or in combination on MDA-MB-231 triple negative breast cancer (TNBC) cellular proliferation, migration, and epithelial to mesenchymal transition. Treatment with 10-16 µM γ-tocotrienol or 20-40 nM vitamin D3 induced a significant dose-responsive decrease in MDA-MB-231 growth after a 4-day culture period. Combined treatment with sub-effective doses of γ-tocotrienol (8 μM) and vitamin D3 (10 nM) induced a synergistically inhibition of MDA-MB-231 cell growth, as determined isobologram analysis. Studies using the matrigel invasion assay showed that similar combination treatment with subeffective doses of γ-tocotrienol and vitamin D3, significantly inhibited MDA-MB-231 motility. These effects appear to result from a reversal in EMT. Western blot analysis shows that combined treatment resulted in an increased expression of the epithelial cell markers E-cadherin, cytokeratins 8 and cytokeratins 18 and a corresponding reduction in mesenchymal cell markers N-cadherin and vimentin. Taken together, these findings indicate that combined treatment with subeffective doses of γ-tocotrienol and vitamin D3 synergistically inhibit TNBC MDA-MB-231 breast cancer cell growth, viability, motility, and induced a reversal of EMT. These findings strongly suggest that combined γ-tocotrienol and vitamin D3 treatment may provide significant benefits in the treatment of metastatic TNBC in women. This study was supported in part by funding from the Louisiana Cancer Foundation. Citation Format: Md. Rafi Anwar, Taylor A. Hurst, Paul W. Sylvester. Combined treatment of γ-tocotrienol, and vitamin D3 synergistically inhibits breast cancer cell proliferation, migration, and epithelial-to-mesenchymal transition (EMT) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 954.