RESUMO
Aim To study the mechanism of action of the new derivative of podophyllotoxin(LN-13)in indu-cing the apoptosis of K562/A02 cells.Methods The MTT method was taken to detect the inhibition of LN-13 and VP-16 on K562/A02 proliferation and inhibi-tion rate and IC50 values were obtained 48 hours later. The K562/A02 cell morphological change induced by LN-13 were observed through Hochest33342 and PI staining after 48 hours later.Flow cytometry was taken to detect the apoptosis of K562/A02 cells induced by LN-13.The reverse transcription-polymerase chain re-action was taken to detect the Bcl-2,Bax,caspase-3 and mdr-1 mRNA expression.The expression of P-gp was detected by Western blot.Results The growth of K562 /A02 cells was obviously inhibited by LN-13 when IC50 value was 3.32 μmol · L-1 .LN-13 could obviously induced cell apoptosis observed by Ho-chest33342 and PI staining.Flow cytometry detection showed that LN-13(2,4,8 μmol·L-1 )could induce cell apoptosis and apoptosis ratio reached 15.0%, 48.0%,68.96%,respectively.The reverse transcrip-tion-polymerase chain reaction showed that LN-13 in-creased the Bax and Caspase-3 mRNA expression,and meanwhile the expression of mdr-1 mRNA decreased. Western blot showed that P-gp expression was de-creased as the LN-13 dose increased.The data were significantly different from those of control group.Con-clusion Podophyllotoxin derivative LN-13 can induce the apoptosis of K562 /A02 cells,which may be close-ly-related to regulating P-gp expression and apoptosis related gene mRNA expression.
RESUMO
DNA repair processes play a role in the development of drug resistance which represents a huge obstacle to leukemia chemotherapy.Histone H2AX phosphorylation (ser139) (γH2AX) occurs rapidly at the onset of DNA double strand break (DSB) and is critical to the regulation of DSB repair.If DNA repair is successful,cells exposed to anti-neoplastic drugs will keep entering the cycle and develop resistance to the drugs.In this study,we investigated whether γH2AX can be used as an indicator of tumor chemosensitivity and a potential target for enhancing chemotherapy.K562 and multi-drug resistant cell line K562/A02 were exposed to adriamycin (ADR) and γH2AX formed.Flow cytometry revealed that percentage of cells expressing γH2AX was increased in a dose-dependent manner and the percentage of K562/A02 cells was lower than that of K562 cells when treated with the same concentration of ADR.In order to test the potential of γH2AX to reverse drug resistance,K562/A02 cells were treated with PI3K inhibitor LY294002.It was found that LY249002 decreased ADR-induced γH2AX expression and increased the sensitivity of K562/A02 cells to ADR.Additionally,the single-cell gel electrophoresis assay and the Western blotting showed that LY249002 enhanced DSBs and decreased the expression of repair factor BRCAl.These results illustrate chemosensitivity can partly be measured by detecting γH2AX and drug resistance can be reversed by inhibiting γH2AX.