Effects of radiation on apoptosis rate and expression of apoptosis-related genes in well-differentiated nasopharyngeal carcinoma cells

Abstract

Objective To investigate the effects of radiation on the apoptosis rate and expression of 7 apoptosis-related genes in well-differentiated human nasopharyngeal carcinoma cell line CNE-1.Methods CNE-1 cells were cultured in vitro.The apoptosis rates of CNE-1 cells under 0-,2-,4-,6-,and 8-Gy radiation were measured by flow cytometry.The mRNA expression levels of Bcl-2,Bcl-xl,Bcl-w,Bax,Bak,Bad,and Bid were measured by RT-PCR.The Pearson test was used for analyzing the correlation of mRNA expression with apoptosis rate and radiation dose and the correlation between apoptosis rate and survival fraction.Results The early apoptosis rate of CNE-1 cells increased gradually as the radiation dose ranged from 0 to 6 Gy,but decreased when the radiation dose was 8 Gy; the late apoptosis rate of CNE-1 cells increased as the radiation dose ranged from 0 to 8 Gy.The mRNA expression of Bax was upregulated as CNE-1 cells were irradiated,and it was positively correlated with the early/late apoptosis rate and radiation dose (P =0.000 for all comparisons).The mRNA expression of Bcl-xl was downregulated,and it was negatively correlated with the early/late apoptosis rate (P =0.005 and 0.039) ; but it showed no correlation with radiation dose (P =0.369).The mRNA expression of Bcl-2 was upregulated and reached the peak level when the radiation dose was 4 Gy,and then it fell as the radiation dose increased.The mRNA expression of Bcl-w,Bcl-2,Bad,and Bid were not correlated with the early/late apoptosis rate (P =0.058 -0.894).There was no correlation between the apoptosis rate and survival fraction in CNE-1 cells (P =0.064).Conclusions Bax and Bcl-xl have some correlation with apoptosis rate in CNE-1 cells,but no correlation between the apoptosis rate and survival fraction was observed. Key words: Cell line, nasopharyngeal carcinoma; Apoptosis; Bcl gene expression