Expression And Clinical Significance Of Cyclin G And Apoptosis-related Genes In Leukemia

[Objective]①To explore the expression and clinical significance of cyclin G in leukemia.②To investigate the effects of SU11248 on proliferation inhibition and apoptosis induction in human myeloid leukemia cell line HL-60 cells.③To study the change of cyclin G and apoptosis- related genes'protein and mRNA expressions.[Methods]①Reverse polymerase chain reaction (RT-PCR) was used to analyse the expression of cyclin G mRNA in 129 leukemia patients and 10 normal controls.②HL-60 cells were exposed to SU11248 at different doses. Proliferation inhibition was detected by MTT assay. The ability of SU11248 to induce apoptosis of HL-60 cells was examined by flow cytometry cycle analysis, Annexin-V/PI double staining analysis, DNA fragmentation. The expression of cyclin G was detected by RT-PCR and Western blot, and the expression of bcl-2, bax, caspases-3 and p27 by Western blot.[Results]①The expression of cyclin G in Acute leukemia (AL) and Chronic leukemia (CL) was significantly higher than that in normal control (t was10.59 and 3.88 respectively,P<0.05), but there was no difference between AL and CL(t=1.01,P>0.05). The cyclin G positive rate of newly diagnosed and relapsed cases in AL, acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL) was 71.3%, 66.7% and 85.7% respectively. It was higher than that of remission cases [χ2 was 10.36 (P<0.01), 5.36 (P<0.05)and 5.48(P<0.05) , respectively] and that of normal controls(χ2 was14.79, 11.50 and 14.7 respectively, P<0.01). There was no difference between older (>40) and younger (≤40) patients, between male and female patients and between patients with higher (>50%) and lower (≤50%) immature cells in the peripheral blood. However in AL and AML patients, cyclin G positive rate was higher in patients with WBC>50×109/L than those with WBC≤50×109/L. 53 newly diagnosed cases were found cyclin G positive. The remission rate of cases with high cyclin G expression was significantly lower than that with low cyclin G expression(51.7% vs 79.1%,χ2=4.13,P<0.05).②SU11248 remarkably inhibited the HL-60 cells proliferation, with the IC50 value of 2.0μg/ml. Concomitantly, apoptosis was induced in HL-60 cells, as measured by detection of DNA fragmentation, sub-G1 apoptotic peak, and staining with Annexin-V. These showed that SU11248 induced apoptosis in HL-60 cells in dose-dependent manners when the concentration of SU11248 ranged between 0.25μg/ml to 8.0μg/ml. Moreover, RT-PCR and/or Western-Blot showed that the expressions of bcl-2, cyclin G in HL-60 cells decreased after SU11248 treatment, but the expression of p27 and caspase-3 increased.[Conclusions]①The high expression of cyclin G in AL might take a certain role in the pathogenesis of leukemia and may be one of the factors with poor prognosis.②SU11248 could efficiently inhibit proliferation and induce apoptosis in HL-60 cells in which bcl-2, bax, caspase-3, p27, cyclin G may involve.③Cyclin G might promote leukemic cells proliferation and inhibit cell apoptosis and the modulation of bcl-2, bax, caspase-3, p27 get involved in these process.