Regulatory Mechanism on Anti-Glycolytic and Anti-Metastatic Activities Induced by Strobilanthes crispus in Breast Cancer, In Vitro
Siti Nur Hasyila Muhammad, Nur Arnida Mohd Safuwan, Nik Soriani Yaacob, Agustine Nengsih Fauzi
Abstract
An active fraction of S. crispus, F3, and its bioactive compounds (lutein, β-sitosterol, and stigmasterol) were reported to have anti-glycolytic activities in MDA-MB-231 cells. Since glycolysis can also regulate metastatic activities in cancer cells, this study investigated the mechanism underlying the anti-glycolytic and anti-metastatic activities induced by F3 and its bioactive compounds on MDA-MB-231 cells. The cells were treated with IC50 concentrations of F3, lutein, β-sitosterol, and stigmasterol. GLUT1 protein expression and localization were then observed using a fluorescence microscope. We found that F3, lutein, and β-sitosterol inhibit localization of GLUT1 to the cell membrane, which causes the decrease in glucose uptake. This is supported by a reduction in PKC activity, measured using a spectrophotometer, and increased TXNIP protein expression detected by Western blotting. Both TXNIP and PKC are involved in GLUT1 activation and localization. The expression of signaling proteins involved in the PI3K/AKT pathway was also measured using a flow cytometer. Results show that F3, lutein, β-sitosterol, and stigmasterol reduced the expression of AKT, pAKT, mTOR, and HIF1α in MDA-MB-231 cells. Transwell migration assay was used to measure migration of the MDA-MB-231 cells. A reduction in fibronectin protein expression was observed by fluorescence microscopy, after treatments with F3 and its bioactive compounds, leading to a reduction in the MDA-MB-231 cells’ migratory abilities. As a conclusion, F3 acts as a metabolic inhibitor by inhibiting metabolic rewiring in the promotion of cancer metastasis, potentially due to the presence of its bioactive compounds.