Asiatic Acid Promotes p21WAF1/CIP1 Protein Stability in HepG2 Human Hepatoma Cells

More than 60% of currently used anti-tumor drugs are natural origin or derived from natural compounds (Cragg et al., 2005). Plant-derived compounds are important source of these nature derived anti-tumor agents. Nearly 3000 plant species have been reported for the treatment of cancer (Altinbas et al., 2012; Boreddy et al., 2013). Some plant based anticancer agents have been allowed to enter the clinical trial, such as paclitaxel, vincristine, vinblastine, topotecan and irinotecan (Nobili et al., 2009). Asiatic acid, a pentacyclic triterpene found in the tropical medicinal plant Centella asiatica, has antioxidant, antiinflammatory and neuroprotective properties (Huang et al., 2012; Guo et al., 2013). Some studies have reported the anti-tumor effect of asiatic acid. For example, asiatic acid was reported to enhance apoptosis and cell cycle arrest by promoting the activity of extracellular signalregulated kinase and p38 mitogen-activated protein kinase pathways in human breast cancer cells (Hsu et al., 2005). By generation of ROS, asiatic acid could induce apoptosis in human melanoma cells (Park et al., 2005; Xu