Trifolin induces apoptosis via extrinsic and intrinsic pathways in the NCI-H460 human non-small cell lung-cancer cell line.

Background: Trifolin (kaempferol-3-O-galactoside), which is a galactose-conjugated flavonol, exhibits antifungal and anticancer effects. However, the mechanisms underlying its anticancer activities have not yet been examined.

Purpose: In this study, the anticancer effects of trifolin were examined in human lung cancer cells.

Methods: Cytotoxicity was determined by evaluating cell viability. Apoptosis was analyzed through flow cytometry and western blotting analysis. Death receptors and inhibitors of apoptosis were evaluated through RT-PCR.

Results: Trifolin induced apoptosis in NCI-H460 human non-small cell lung cancer (NSCLC) cells by inhibiting the survival pathway and inducing the intrinsic and extrinsic apoptosis pathways. Trifolin decreased levels of Akt/p-Akt, whereas levels of expression of phosphatidylinositide 3-kinase (PI3K), cyclin D1, cyclin E, and cyclin A were not altered. Trifolin initiated cytochrome c release by inducing mitochondrial outer membrane permeabilization (MOMP). Trifolin increased Bcl-2-associated X protein (Bax) levels and decreased b-cell lymphoma 2 (Bcl-2) levels, while the levels of Bcl-xL were not altered. In addition, trifolin increased the levels of the death receptor involving the Fas/Fas ligand (FasL) and Fas-associated protein with the death domain (FADD), which consequently activated caspase-8, caspase-9, caspase-3, and the proteolytic cleavage of poly (ADP-ribose) polymerase (PARP).

Conclusion: These results suggested that trifolin induced apoptosis via death receptor-dependent and mitochondria-dependent pathways and that trifolin can be used as a therapeutic agent in human lung cancer.