Mushroom Extracts Induce Human Colon Cancer Cell (COLO-205) Death by Triggering the Mitochondrial Apoptosis Pathway and Go/G1-Phase Cell Cycle Arrest

BACKGROUND: Functional foods are extensively studied for their cancer preventive effects. In the present study, we compared the anti-cancer activity of aqueous extracts of three species of mushrooms including: Pleurotus ostreatus (PAE), Auricularia polytricha (AAE) and Macrolepiota procera (MAE) on COLO-205 cells. METHODS: Various in vitro approaches were performed to investigate the most potential mushroom variety that possesses maximum cytotoxic, anti-proliferative and apoptosis inducing properties. MTT assay was used to assess cytotoxicity. IC50 values were obtained and further used to perform clonogenic survival, wound scratch and apoptosis assays. Gene expression studies of apoptosis and cell cycle related studies were performed by reverse transcriptase PCR, followed by estimation of DNA content by flow cytometric analysis. RESULTS: Our study showed that PAE acts as the most prominent inducer of cancer cell death as compared to other species. Therefore, we performed expression studies for apoptosis and cell cycle to understand the genes which are responsible for their profound activities. Expression studies illustrated increased levels of caspase-9 (1 to 2.1, P < 0.01), caspase-3 (1 to 1.7, P < 0.01) and Bax (1 to 1.4, P < 0.05) genes followed by decreased levels of Bcl-2 (1 to 0.44, P< 0.05) gene with PAE treatment and this was attributed to the activation of intrinsic pathway. Along with apoptosis, an arrest at Go/G1 phase was observed through flow cytometric analysis followed by increased expression of inhibitors of cyclin dependent kinases (CKIs), p16 (1 to 1.5, P < 0.05) and p21 (1 to 2.4, P < 0.01). CONCLUSION: This study exemplifies the effectiveness of PAE and may serve as a potential therapeutic agent.