Identification of an Annonaceous Acetogenin Mimetic, AA005, as an AMPK Activator and Autophagy Inducer in Colon Cancer Cells

Annonaceous acetogenins, a large family of naturally occurring polyketides isolated from various species of the plant genus Annonaceae, have been found to exhibit significant cytotoxicity against a variety of cancer cells. Previous studies showed that these compounds could act on the mitochondria complex-I and block the corresponding electron transport chain and terminate ATP production. However, more details of the mechanisms of action remain ambiguous. In this study we tested the effects of a set of mimetics of annonaceous acetogenin on some cancer cell lines, and report that among them AA005 exhibits the most potent antitumor activity. AA005 depletes ATP, activates AMP-activated protein kinase (AMPK) and inhibits mTOR complex 1 (mTORC1) signal pathway, leading to growth inhibition and autophagy of colon cancer cells. AMPK inhibitors compound C and inosine repress, while AMPK activator AICAR enhances, AA005-caused proliferation suppression and subsequent autophagy of colon cancer cells. AA005 enhances the ATP depletion and AMPK activation caused by 2-deoxyglucose, an inhibitor of mitochondrial respiration and glycolysis. AA005 also inhibits chemotherapeutic agent cisplatin-triggered up-regulation of mTOR and synergizes with this drug in suppression of proliferation and induction of apoptosis of colon cancer cells. These data indicate that AA005 is a new metabolic inhibitor which exhibits therapeutic potentials in colon cancer.