LukS-PV induces mitochondrial-mediated apoptosis and G0/G1 cell cycle arrest in human acute myeloid leukemia THP-1 cells

Abstract

The S component (LukS-PV) is one of the two components of Panton-Valentine leukocidin (PVL), which is a pore-forming cytotoxin secreted by Staphylococcus aureus, with the ability to lyse leukocytes. In this study, LukS-PV had the ability to induce apoptosis in the human acute myeloid leukemia (AML) cell line THP-1. Therefore, we investigated the mechanisms of LukS-PV-induced apoptosis in THP-1 cells. THP-1 cells treated with LukS-PV, resulted in a significant inhibition of proliferation in a dose- and time-dependent manner, and induced G0/G1 arrest associated with an inhibition of cell cycle arrest regulatory protein (cyclin D1) in a dose- and time-dependent manner, as measured by flow cytometry (FCM). After 12h exposure to LukS-PV (1.00 μM), annexin V-EGFP/propidium iodide (PI) FCM revealed that 19.5±3.6% of THP-1 cells were apoptotic, and terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) staining also revealed THP-1 cells were apoptotic. Chip analysis of 84 apoptosis-related genes demonstrated that 9 genes were up-regulated at least 2-fold and that 5 genes were down-regulated at least 2-fold in the treatment group when compared with levels in the control group. Western blotting reveled that the expression of caspase-8 increased significantly (approximately 4-fold). The levels of caspase-9, -3 and Bax increased significantly, and levels of Bcl-2 decreased rapidly with LukS-PV treatment. These data suggest that LukS-PV acts as an anti-leukemia agent and activates AML cell apoptosis via the mitochondrial pathway. Therefore, LukS-PV may be a multi-targeting drug candidate for the prevention and therapy of AML.

Keywords: 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium; AML; Apoptosis; CTCL; Cell cycle; Cyclin; FBS; FCM; GAPDH; LFA-1; LtxA; LukS-PV; MTS; Mitochondrial pathway; PBS; PI; PMNs; PVL; Panton-Valentine leukocidin; SCID; SD; Severe Combined Immunodeficiency; THP-1 cells; TUNEL; acute myeloid leukemia; cdks; cell cycle arrest regulatory protein; comparative CT; cutaneous T-cell lymphoma; cyclin-dependent kinases; ddCt; fetal bovine serum; flow cytometry; glyceraldehyde-3-phosphate dehydrogenase; leukotoxin; lymphocyte function-associated antigen-1; phosphate buffered saline; polymorphonuclear leukocytes; propidium iodide; standard deviation; terminal deoxynucleotidyl transferase-mediated nick end labeling.