A natural flavonoid lawsonaringenin induces cell cycle arrest and apoptosis in HT-29 colorectal cancer cells by targeting multiple signalling pathways

Colorectal cancer is the third most common malignancy in the world having a high mortality rate. Flavonoids possess many biological activities including anti-cancer activity. lawsonaringenin (LSG) is a flavonoid isolated from leaves of Lawsonia alba Lam. The objective of this study was to demonstrate the anti-cancer potential of LSG in colorectal cancer for the first time. The HT-29 cells were treated with LSG or 5-fluoruracil, as a positive control, to determine its effect on cell cytotoxicity by a MTT cell proliferation assay, and cell cycle progression and apoptosis using flowcytometry. We also determined the mechanisms underlying LSG-mediated growth inhibition of HT-29 cells by by investigating the expression of key oncogenes and apoptosis genes using q-RT PCR and immunocytochemical analysis. The cell cytotoxicity data showed that the IC50 value of LSG was significantly less than the IC50 value of 5-FU (50 µM). The anti-proliferative effect of LSG was mediated by arresting cells in the S phase of the cell cycle which then led to the induction of apoptosis the q-RT PCR and immunocytochemical analysis showed that LSG reduced the expression of ß-catenin (non-phosphorylated) and its downstream signalling target c-Myc, whereas it increased the phosphorylation of ß-catenin. Furthermore, LSG also downregulated the expression of oncogene K-Ras and anti-apoptotic proteins, Bcl-2, and Bcl-xL. In conclusion, our data demonstrates that LSG exerted its anti-tumor activity by arresting the cell cycle in S phase, and by downregulating the expression of oncogenes including ß-catenin, c-Myc, K-Ras and anti-apoptosis proteins Bcl-2 and Bcl-xL. This study suggests a potential use of natural flavonoid, lawsonaringenin, to attenuate colorectal cancer growth; however, further pre-clinical/clinical studies are required to establish its role as a therapeutic agent.