The Inhibition Of A112 To HL-60 Cells And NB4 Cells

Objective:A112 is a tamibarotene dimethylaminoethyl ester which is considered as the candidate compound for treatment of acute promyelocytic leukemia (APL) and other types of leukemia. Our goal in this study was to evaluate its efficacy of anti-cancer activity, beginning by studying its inhibitory effects on human promyelocytic leukemia cells HL-60 and then comparing it to tamibarotene.Methods:In vitro assays, inhibition of HL-60 cell growth by A112 or tamibarotene was evaluated by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) method. Annexin-V/PI staining analysis was employed to evaluate HL-60 cell apoptosis exposure to A112 or tamibarotene. The levels of apoptotic proteins including caspase-3, caspase-9 and cleaved poly ADP-ribose polymerase (PARP) in HL-60 cells were then examined by Western blot assay. In vivo assays, the efficacy of A112 was evaluated in a HL-60 xenograft mice model after three weeks of tail vein daily administration.Tumor growth inhibition rates were defined as a percentage of the control tumor weight. HL-60 xenografts were then removed for terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining assay and Western blot analysis to estimate the expressions of caspase-3, caspase-9 and PARP as described in vitro assay.Key findings:A112 effectively inhibited HL-60 cell growth as estimated by the MTT assay. The inhibitory effect of A112 was greater than that of tamibarotene at the same concentrations. A112 significantly induced HL-60 cell apoptosis as measured by flow cytometry analysis of the annexin V-positive cells and in vivo by analysis of the TUN EL staining cells in HL-60 xenografts bearing in mice. The inhibitory effect of A112 was confirmed in mice in which A112 delayed the growth of HL-60 xenografts after three weeks tail vein administration. The inhibitory effect of A112 on HL-60 xenografts was stronger than that of tamibarotene. Further studies of the apoptotic proteins were measured by Western blot assay. A112 increased caspase-3, caspase-9 and PARP in HL-60 cells both in vitro and in vivo.Conclusion:These results suggest that A112 has a powerful inhibitory effect on the growth of leukemia cells and that the mechanism may relate to the induction of apoptosis.