Radiation-induced G2/M arrest and Apoptosis in acidic environment

초록

We have invesitigated the effect of p53 status on the radiation-induced G2/M arrest and apoptosis in neutral and acidic environment in RKO.C human colorectal tumor cells. The G2/M arrest after irradiation with 12 Gy in RC10.1 cells lacking p53 was markedly longer than that in RKO.C cells bearing wild-type p53. The radiation-induced G2/M arrest in pH 6.6 medium was much longer than in pH 7.5 medium regardless of p53 status. In RKO.C cells, the p53 level progressively increased peaking 4-8 h after irradiation and p21 level increaed 24 h after irradiation in pH 7.5 medium. Whereas p53 level increased later than 8h after irradiation and p21 level failed to increase in pH 6.6 medium. The radiation-induced apoptosis in RKO.C cells was suppressed or delayed in pH 6.6 medium relative to that in pH 7.5 medium. The relationship between the expression of p53 and p21 proteins, radiation-induced G2/M arrest, cyclin-dependent kinases responsibel for cell cycle progression and apoptosis are being investigated.