Abstract 997: γ-Tocotrienol inhibition of metastatic phenotypic behavior is associated with a decrease in galectin-3 expression and distribution in the highly malignant mouse +SA & TS/A mammary tumor cells

Abstract

Abstract γ-Tocotrienol is a rare natural isoform of vitamin E that displays potent apoptotic and anti-metastatic activity against breast cancer. Galectin-3 is a protein that plays an important role in metastasis by binding to glycoconjugates on receptors and extracellular matrix proteins. Studies were conducted to investigate the effects of γ-tocotrienol on galectin-3 expression and morphology in highly malignant +SA, TS/A MDA-MB-231 tumor cells. Computer-aided molecular modeling studies compared anticancer agents, salirasib and γ-tocotrienol, with the active site of galectin-3 and β-lactose (a known ligand). Results showed that γ-tocotrienol displays similar galectin-3 amino acid interactions as β-lactose and salirasib. Protein docking show that salirasib (active binding -2.8) and γ- tocotrienol (active binding -2.87) had similar binding scores and binding moieties. Immunocytochemical fluorescent staining show that γ-tocotrienol treatment disrupted galectin-3 expression and distribution, and a corresponding reduction in +SA cellular migration similar to that induced by β-lactose. Western blot analysis shows that γ-tocotrienol treatment induces a downregulation of galectin-3 expression. Immunocytochemistry studies shows that galectin-3 is highly expressed in +SA and TS/A cells, and γ-tocotrienol greatly reduced galectin-3 expression and distribution Furthermore, galectin-3 was found to form extracellular structures on the outer membrane of +SA, TS/A, and MDA-MB-231 cells, and γ-tocotrienol greatly attenuated galectin-3 and fibronectin distribution. γ-Tocotrienol treatment decreased f-actin stress fibers distribution in all cell lines. Furthermore, treatment with 1.5 μM histamine significantly stimulated +SA mammary tumor cell migration, whereas combination treatment with 5 μM γ-tocotrienol completely blocked histamine-induced +SA cell migration. In TS/A cells, 6-15 μM tocotrienol induced a dose-responsive increase in doxorubicin staining inside the nucleus. In MDA-MB-231 cells, syncytial cells were associated with galectin-3 expression and this was suppressed by 5-15 μM γ-tocotrienol. In summary, these results demonstrate that γ-tocotrienol treatment inhibits extracellular galectin-3 expression and disrupts galectin-3 carbohydrate binding and activation of +SA, TS/A and MDA-MB-231 breast cancer cells. These findings also suggest that γ-tocotrienol may provide significant benefits in the prevention and/or treatment of metastatic breast cancer. This study was supported in part by funding from the Louisiana Cancer Foundation. Citation Format: Paul W. Sylvester, Jessie J. Grazier. γ-Tocotrienol inhibition of metastatic phenotypic behavior is associated with a decrease in galectin-3 expression and distribution in the highly malignant mouse +SA & TS/A mammary tumor cells [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 997.