Anticancer effects of amooranin in human colon carcinoma cell line in vitro and in nude mice xenografts

Amooranin (AMR), a natural triterpenoid drug isolated and characterized from Amoora rohituka stem bark, is cytotoxic to SW620 human colon carcinoma cell line with an IC50 value of 2.9 mu g/ml. This novel compound caused depolarization of mitochondrial membrane and decrease of membrane potential, indicating initial signal of apoptosis induction. The percentage of cells with decreased mitochondrial potential ranged from 7.4% at 1 mu g/ml to 60.5% at 100 mu g/ml AMR. Flow cytometric analysis of apoptosis using Annexin-V-FITC staining showed that the percentage of apoptotic cells ranged from 7.5% at 1 mu g/ml to 59.2% at 100 mu g/ml AMR. AMR-induced apoptosis was accompanied by redistribution of cytochrome c from mitochondria to cytosol as well as down regulation of Bcl-2 and Bcl-X-L proteins in a dose-dependent manner. SW620 human colon carcinoma xenograft mice treated with AMR showed significant reduction in tumor growth rates compared to saline- and doxorubicin-treated groups. The reduction in tumor growth rate was better in xenografts treated with 2 mg/kg AMR than 5 and 10 mg/kg treated mice. The analysis of global gene expression changes induced by AMR in xenograft tumors by microarray hybridization revealed that several genes involved in energy pathways, transport, apoptosis, immune response, nucleic acid metabolism, protein metabolism, cell growth and/or maintenance, signal transduction and cell communication, were affected by this natural cancer drug. These results suggest that the anticancer properties of AMR in SW620 human colon carcinoma cell line are mediated through its effects on functional genomics, targeting the apoptotic process. C 2006 Wiley-Liss, Inc.