Morindone as a potential therapeutic compound targeting TP53 and KRAS mutations in colorectal cancer cells

There is an increasing demand for anticancer agent in treating colorectal cancer (CRC) with frequently mutated TP53 and KRAS genes. Phytochemical compounds are suitable as chemoprevention for CRC since dietary factor is a major risk factor. Anthraquinones from Morinda citrifolia L. were previously reported with various pharmacological properties. Various in vitro experiments were conducted to investigate the effects of two anthraquinones: damnacanthal and morindone on the cell proliferation, cell cycle, apoptosis, gene expression and protein expression in two CRC cells: HCT116 and HT29. Real-time monitoring of CRC cells showed that both anthraquinones exerted significant anti-proliferative effects in a dose- and time-dependent manner. Next, cell cycle analysis revealed an increase in the percentage of CRC cells in the G1 phase under anthraquinones treatment. Fluorescence microscopy also showed an increment of apoptotic cells under anthraquinones' treatment. siRNA transfection was conducted to evaluate the mediating effect of gene knockdown on mutated TP53 and KRAS in CRC cells. Before transfection, qRT-PCR analysis showed that only morindone downregulated the gene expression of mutated TP53 and KRAS and then further downregulated them after transfection. Both damnacanthal and morindone treatments further downregulated the expression of these two genes but upregulated at the protein expression level. Furthermore, gene knockdown also sensitised CRC cells to both damnacanthal and morindone treatments, resulting in lowered IC₅₀ values. The accumulation of cells at the G1 phase was reduced after gene knockdown but increased after damnacanthal and morindone treatments. In addition, gene knockdown has increased the number of apoptotic cells in both cell lines and further increment was observed after anthraquinone treatment. In conclusion, morindone could be a competitive therapeutic agent in CRC by exhibiting multiple mechanism of anti-cancer actions.