Germanicol induces selective growth inhibitory effects in human colon HCT-116 and HT29 cancer cells through induction of apoptosis, cell cycle arrest and inhibition of cell migration

Purpose: The main aim of this research was to evaluate the anticancer and apoptotic effects of germanicol - a natural triterpene - in HCT-116 and HT29 human colon cancer cells and deciphering its mode of action by studying its effect on the cell cycle and cell migration. Methods: Cell cytotoxicity was evaluated by MTT assay, while cell death was assessed by LDH assay. Fluorescence microscopy, using DAPI and acridine orange/ethidium bromide (AO-ETBR), was carried out to evaluate the effect of germanicol on cellular morphology and apoptosis induction. Apoptosis quantification was performed by Annexin V-FITC assay, while cell cycle analysis was performed by flow cytometry using propidium iodide (PI). Results: The results revealed that germanicol showed selective, potent and dose-dependent cytotoxicity in HCT-116 and HT29 human colon cancer cells, while it showed lower cytotoxicity in normal colon cells (human colon fibroblast, CCD-18Co). LDH assay also showed that germanicol induced dose-dependent cell death in HCT-116 and HT29 cells. Fluorescence microscopy revealed that germanicol induced apoptosis via chromatin condensation and DNA damage in HCT-116 colon cancer cells. It also revealed that the percentage of cells with orange and red fluorescence increased when adding a germanicol dose, indicating apoptosis. Germanicol also inhibited cancer cell migration. Conclusion: The current findings reveal that germanicol exhibits selective antiproliferative activity against two human colon cancer cells. The normal cell line was less affected by the drug, as compared to the two cancer cell lines, indicating that germanicol will not target normal living cells. The antiproliferative effect was shown to be mediated through the induction of apoptosis and suppression of cell migration.