[Inhibitory effects of emodin on drug-resistant HL-60/ADR cell proliferation and its induction of apoptosis].
ABSTRACT The study was aimed to investigate the effects of emodin on the proliferation and apoptosis of adriamycin-resistant HL-60/ADR cells, and to explore the underlying mechanism. The cell viability and colony formation were detected by MTT assay and colony formation assay respectively. Apoptotic cells were tested by means of cell cycle analysis, mitochondrial transmembrane potential levels, caspase-3 activity detection, Annexin V FITC/PI staining and TUNEL labeling. RT-PCR was used to analyze the bcl-2 and c-myc mRNA expressions. The protein expressions of Bcl-2, c-Myc and caspase-3 precursor were determined by Western blot. The results showed that HL-60/ADR cell growth was significantly inhibited by emodin in dose and time dependent manners. Cell colony formation obviously decreased with IC50 5.79 micromol/L. G0/G1 phase cell population increased while G2/M phase cells decreased in 40 and 80 micromol/L groups compared with control group (p < 0.01), and no significant difference of cell cycle was observed in 20 micromol/L group (p > 0.05). The typical hypo-diploid peak (apoptotic peak) appeared in each dose group. The levels of mitochondrial transmembrane potential of HL-60/ADR cells decreased and caspase-3 activity increased when incubated with emodin for 12 and 24 hours respectively. Apoptosis occurred in a dose-dependent manner, and its earlier and later stages were identified by Annexin-V FITC/PI staining and TUNEL labeling methods respectively. The expressions of bcl-2, c-myc mRNA and Bcl-2, c-Myc, caspase-3 precursor protein were all down-regulated in a time-dependent manner after treatment with emodin at different times. It is concluded that emodin efficiently inhibits growth and induces apoptosis on HL-60/ADR cells, which may be related with the down-regulation of mitochondrial transmembrane potential and expressions of bcl-2 and c-myc, as well as up-regulation of caspase-3 activity.