Centipedegrass extract induces apoptosis through the activation of caspases and the downregulation of PI3K/AKT and MAPK phosphorylation in leukemia cells

Acute lymphoblastic leukemia (ALL), which involves the blood and bone marrow, is the most common type of cancer in children younger than 5 years of age. Previous studies have investigated the effects of centipedegrass extract (CGE), which is mainly composed of maysin and its derivatives, and have demonstrated that it has various biological activities, including antioxidant and anti-inflammatory activities, pancreatic lipase inhibitory activity, anti-adipogenic activity and insecticidal activity. To the best of our knowledge, this study is the first to investigate the anticancer effects of CGE in ALL cell lines and to elucidate the mechanisms underlying these effects. Cell viability was measured by thiazolyl blue tetrazolium blue (MTT) assay. Apoptosis, cell cycle progression and mitochondrial membrane potential (Delta Psi m) were determined by flow cytometry. The effects of CGE on the phosphatidylinositol 3-kinase (PI3K)/AKT pathway and mitogen-activated protein kinases (MAPKs) were assessed by immunoblotting. PI3K, MAPK and caspase inhibitors were used to further confirm the molecular mechanisms involved. Our results clearly demonstrated that the proliferation of the ALL cells was significantly inhibited by CGE in a dose-dependent manner. Apoptosis was accompanied by the induction of significant G1 cell cycle arrest. The resulting alteration of the Delta Psi m increased the activity of caspase-3/7. The induction of apoptosis was enhanced by the combined treatment of CGE with a PI3K inhibitor or an extracellular signal-regulated kinase (ERK) inhibitor, whereas the CGE-induced apoptosis was inhibited in the presence of caspase inhibitors, such as Z-VAD-FMK and Z-IETD-FMK. Furthermore, CGE inhibited PI3K activity by decreasing the levels of phosphorylated (p-)AKT, p-BAD, and Bcl-2 together with the levels of MAPKs, including p-ERK and p-JNK, but demonstrated no effects on p38 MAPK. Thus, our data suggest that CGE may be a novel natural compound with potential for use as an antitumor agent in ALL.