Effects of Rongthong (Garcinia hanburyi) resin on inhibition of cell proliferation, cell cycle, and apoptosis in colorectal cancer cells

Colorectal cancer (CRC) is one of the most common cancers globally. The current treatments have many limitations. The new compound with low toxicity is on demand. In this study, the potential of Garcinia hanburyi resin (GHR) as a candidate drug for CRC treatment was explored. First, the Gambogic acid (GA) content in GHR was analyzed using an HPLC method, and a result confirmed that GA is the major compound as 71.26% of the GHR. Next, the human CRC cell lines (SW480 and Caco-2) and normal colon cells (CCD841 CoN) were tested with GA and GHR for 48 and 72 hours. The cytotoxicity was investigated using a cell viability assay, and the half maximal inhibitory concentrations (IC50) of GA and GHR were calculated. The IC50 values of GA on SW480 and Caco-2 cell viability were 0.46 μM and 0.63 μM at 48 hours, and 0.38 μM and 0.57 μM at 72 hours. Meanwhile, IC50 of GHR on SW480 and Caco-2 were 0.55 μg/ml and 1.07 μg/ml at 48 hours, and 0.52 μg/ml and 0.91 μg/ml at 72 hours, respectively. Finally, the cell cycles after treatment of GHR for 48 and 72 hours were examined using a flow cytometer. An increase in the DNA fragmentation was demonstrated in a dose-dependent manner as reflected by the increase in the percentage of cells in the sub-G1 phase compared to the DMSO-treated cells. Furthermore, the alteration of apoptosis-related protein levels was observed; Bax was increased, but procaspase-3 and Bcl-2 were decreased in GR-treated cells. In conclusion, GHR contained GA as a major active compound. It inhibited CRC cell proliferation via the induction of apoptosis pathway while having low toxicity on normal colon cells. This finding showed that GHR could be an alternative agent for effective CRC treatment to improve the patients’ quality of life.