Forsythia suspensa extract has inhibitory effect on proliferation and apoptosis of A549 lung cancer cells

Abstract

Purpose: To investigate the effect of Forsythia suspensa extract (FSE) on apoptosis and proliferation in A549 human lung cancer cells. Methods: Inverted microscope was employed to observe morphological changes in A549 cells after exposure to FSE. Trypan blue staining of living cells was used to construct the cell growth curve after treatment with varying concentrations of FSE. The influence of FSE on cell proliferation, apoptosis and cell cycle was determined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, while protein expressions of key apoptosis-related enzymes were evaluated by immunocytochemical method. Results: FSE inhibited the growth of A549 lung cancer cells at a concentration range of 10 - 150 μg/mL. Flow cytometry results showed that FSE induced apoptosis in A549 cells. The proportion of cells in G0/G1-phase increased significantly (p < 0.01), while the proportion of cells in S- and G2/M-phase decreased correspondingly, indicating that the cells were in G0/G1-phase arrest. Cell cycle arrest and apoptosis-inducing effect gradually rose with increase in FSE concentration. With increasing concentrations of FSE, there was also significant increase in the expressions of caspase-3 (p < 0.05), caspase-8 (p < 0.01) and caspase-9 (p < 0.05), but significant decrease in Ki-67 (p < 0.01) and p21 ras protein (p < 0.01). Conclusion: FSE exerts significant inhibitory effect on the proliferation of A549 lung cancer cells. Therefore, the plant can potentially be developed for the treatment of lung cancer.