Isoangustone A induces apoptosis in SW480 human colorectal adenocarcinoma cells by disrupting mitochondrial functions.

Licorice and its components have been reported to posses various anti-tumor activities, but its active ingredients and underlying mechanisms are not well understood yet. In the present study, a group of representative licorice-derived compounds that could be detected in rat plasma or urine were screened for anti-tumor activity. Among these compounds, isoangustone A (IAA) was found to promptly inhibit the viability of SW480 human colorectal adenocarcinoma cells in a time- and concentration-dependent manner. Further analyses indicate that IAA activated caspase-dependent pro-apoptotic signaling and induced significant apoptosis, while had little effect on cell cycle. IAA strongly inhibited Akt phosphorylation within 5 min; however, overexpression of constitutively activated Akt could not rescue IAA-mediated inhibition, indicating that inhibition of Akt was not involved in IAA-induced apoptosis. Further examinations show that IAA induced dissipation of mitochondria membrane potential and release of cytochrome C within 1h, accompanied by swelling of mitochondrial matrix and disrupting of mitochondrial outer membrane, and followed by decreasing of cellular ATP. The above results suggest that IAA induced apoptosis in colorectal cancer cells principally by inducing mitochondrial outer membrane permeabilization, and deserves further investigations as a novel anti-colorectal cancer agent.