Objective: To investigate the impact of NU7026 and Wortmannin, inhibitors of DNA-dependent protein kinase (DNA-PK), in HL60 cells apoptosis induced by 1, 4-benzoquinone (1, 4-BQ).
Methods: HL60 cells were divided into three groups according to the exposures: the poisoned groups which were treated with 0, 5, 10, 25 and 50 µmol/L 1, 4-BQ for 24 h, respectively, the NU7026 groups which were preincubated with 10 µmol/L NU7026 for 1h prior to the 24h treatment of 0, 5, 10, 25 and 50 µmol/L 1, 4-BQ and the Wortmannin groups which were preincubated with 25 µmol/L Wortmannin for 1h prior to the 24 h treatment of 0, 5, 10, 25 and 50 µmol/L 1, 4-BQ. Then we detected the apoptosis via flowcytometry Annexin V-FITC/PI and the DNA Ladder, respectively. We also tested the expressions of Bax mRNA with Real-Time PCR in HL60 cells which were exposed to 10 µmol/L NU7026 for 24 h, 25 µmol/L Wortmannin 24 h, 10 µmol/L 1, 4-BQ 24 h, 10 µmol/L NU7026 1h+10 µmol/L 1, 4-BQ 24 h and 25 µmol/L Wortmannin 1 h+10 µmol/L 1, 4-BQ 24 h, as well as null (control). We also examed the expressions of p53 in HL60 cells with Western blot.
Results: Annexin V-FITC/PI apoptosis tests suggested that apoptosis rates of NU7026+10 µmol/L 1, 4-BQ group and Wortmannin +10 µmol/L 1, 4-BQ were 17.6±1.19% and 15.2±1.22%, respectively. Both of results were higher than that of 10 µmol/L 1, 4-BQ group (6.3±1.04%); Apoptosis of NU7026+25 µmol/L 1, 4-BQ group was 46.2±3.55%, and Wortmannin +25 µmol/L 1, 4-BQ group 26.9±2.62%. Both of results were also higher than that of 25 µmol/L 1, 4-BQ group (14.1±1.54%); Apoptosis of NU7026+50 µmol/L 1, 4-BQ group (61.8±1.78%) was higher than that of 50 µmol/L 1, 4-BQ group (35.9±4.51%). The above results were all statistically significant (P < 0.05).
Results: of DNA-Ladder were basically consistent with those of Annexin V-FITC/PI apoptosis tests. In addition, both NU7026 and Wortmannin pretreatment elicited the higher expression of Bax mRNA in HL60 treated by 1, 4-benzoquinone with statistically significance (P < 0.05). However, p53 protein was not detected in HL60 cells as the western blot indicated.
Conclusion: Inhibitors of DNA-PK, NU7026 and Wortmannin, promote p53-independent apoptosis induced by 1, 4-benzoquinone in HL60 cells.