PURPOSE: Colorectal cancer is one of the deadly malignancies and is one of the top three most common cancers and the third leading cause of cancer-related deaths. The main objective of the study was to investigate the anticancer effects of norwogonin - a naturally occurring plant flavone. We also examined its effects on programmed cell death, autophagy and cell cycle phase distribution. METHODS: Cell viability of colon cancer cells was evaluated by MTT assay while apoptotic studies were carried out by fluorescence microscopy using acridine orange (AO)/ethidium bromide (EB) and Comet assays. Transmission electron microscopy (TEM) was used to study formation of autophagosomes reminiscent of autophagy. Furthermore, western blot assay was used to study the effects of norwogonin on apoptosis-related protein expressions including Bax, Bcl-2 and autophagy-related proteins. Effects on cell cycle were evaluated by flow cytometry. RESULTS: The results showed that norwogonin causes substantial reduction in the viability of the human colorectal carcinoma cells in a dose-dependent manner, exhibiting an IC50 of 15.5 µM in cancer cells and IC50 of 90 µM in normal cell lines. The AO/EB staining assay showed that norwogonin suppresses the viability of cancer cells via induction of apoptotic cell death which was associated with increase in Bax and decrease in Bcl-2 levels. Comet assay results also confirmed that norwogonin induces apoptosis. Norwogonin also led to induction of autophagy along with triggering G2/M phase cell cycle arrest. CONCLUSIONS: In conclusion, the current study shows that norwogonin has a potential to inhibit in vitro colorectal cancer cells growth by triggering apoptosis, autophagy and cell cycle arrest and as such could be developed as a possible anticancer agent.
PURPOSE:Colorectal cancer is one of the deadly malignancies and is one of the top three most common cancers and the third leading cause of cancer-related deaths. The main objective of the study was to investigate the anticancer effects of norwogonin - a naturally occurring plant flavone. We also examined its effects on programmed cell death, autophagy and cell cycle phase distribution. METHODS: Cell viability of colon cancer cells was evaluated by MTT assay while apoptotic studies were carried out by fluorescence microscopy using acridine orange (AO)/ethidium bromide (EB) and Comet assays. Transmission electron microscopy (TEM) was used to study formation of autophagosomes reminiscent of autophagy. Furthermore, western blot assay was used to study the effects of norwogonin on apoptosis-related protein expressions including Bax, Bcl-2 and autophagy-related proteins. Effects on cell cycle were evaluated by flow cytometry. RESULTS: The results showed that norwogonin causes substantial reduction in the viability of the humancolorectal carcinoma cells in a dose-dependent manner, exhibiting an IC50 of 15.5 µM in cancer cells and IC50 of 90 µM in normal cell lines. The AO/EB staining assay showed that norwogonin suppresses the viability of cancer cells via induction of apoptotic cell death which was associated with increase in Bax and decrease in Bcl-2 levels. Comet assay results also confirmed that norwogonin induces apoptosis. Norwogonin also led to induction of autophagy along with triggering G2/M phase cell cycle arrest. CONCLUSIONS: In conclusion, the current study shows that norwogonin has a potential to inhibit in vitro colorectal cancer cells growth by triggering apoptosis, autophagy and cell cycle arrest and as such could be developed as a possible anticancer agent.