Methanolic Extracts of Bitter Melon Inhibit Colon Cancer Stem Cells by Affecting Energy Homeostasis and Autophagy
Figure 5
Bitter melon extracts affect energy homeostasis of cancer cells by effecting cellular ATP though AMPK-mediated pathway. (a) ATP modulation by bitter melon extract in HT-29 and SW480 cells. Cells were treated with increasing concentration of AICAR (AMPK activator), BMW (100 μg/mL), or a combination of the two. AICAR treatment resulted in significant decrease in the ATP levels of the cells. A similar decrease was observed in the ATP levels upon BMW treatment. A more rapid decline was observed with the combination, at least in the initial time points. (b) Cell proliferation of BME treated cells was revived using exogenously added ATP. SW480 cells were treated with increasing concentration of Bitter melon extract (0–500 μg/mL) with the media containing various concentrations of ATP (0–500 μM). Exogenous ATP reversed the antiproliferative activity of BMW in a concentration dependent manner. (c) Western blot analysis for AMPK and its downstream regulators mTOR, and P70 S6Kinase. The two cells lines treated with increasing concentration of bitter melon whole fruit extract showed increased activation of AMPK, mTOR and P70 S6Kinase in a concentration dependent manner. (d) No additive effect in AMPK activation was observed by cotreatment with BMW and AICAR as compared to any one alone as measured via western blot. A significant additive effect observed in the activation of mTOR pathway by the combination suggesting BMW may activate mTOR by other pathways in addition to AMPK pathway.
