Relationship Among Apoptosis And Apoptosis Associated Genes And Radiation Sensitivity In Well And Poor Differentiated Nasopharyngeal Carcinoma Cell Lines

Objective: To investigate the spontaneous apoptosis and radiation inducedapoptosis in the prediction of radiationsen-sitivity of nasopharyngeal Carcinoma cell andthe molecule biology foundation of the differential apoptosis rate and radiosensitivity.Methods:1) Radiosensitivity parameters of the well differentiated nasopharyngealCarcinoma cell lines(CNE-1) and poor differentiated nasopharyngeal Carcinoma celllines(CNE-2) were obtained by the colony forming assay and radiation dose-survivalcurve was done by single-hit multi-target model and linear quadratic model.2) Early andlate stage apoptosis were detected using an AnnexinV/FITC apoptosis kit by flowcytometry to compare the difference between CNE-1and CNE-2on2,4,6,8days,respectively, mRNA and protein expression level of apoptosis ralated genes（Bax, Bak,Bad, Bid, Bcl-2, Bcl-xl, Bcl-w）were detected by performing RT-PCR and Western blot.3)After2,4,6,8Gy radiation with linear accelerator, early and late stage apoptosis weremeasured by flow cytometry again, RT-PCR was used to detect mRNA expressions ofapoptosis ralated gene（sBax、Bak、Bad、Bid、Bcl-2、Bcl-xl、Bcl-w）respectively. Results:1) At each dose point, the survival Fraction (SF) of CNE-1was higher than those ofCNE-2，The parameters of Function mode showed: NCNE-1> NCNE-2, D0CNE-1> D0CNE-2,Dq CNE-1> Dq CNE-2，αCNE-1<αCNE-2，βCNE-1> βCNE-2，α/βCNE-1<α/βCNE-2，SF2CNE-1> SF2CNE-2.2) CNE-2exhibited higher early and late stage apoptosis rate compared withCNE-1when they on the same culture days(2,4,6,8d) and delivere the same radiationdoses(2,4,6,8Gy)(P<0.05).3) The mRNA and protein expression level of Bax, Bak, Bad,Bid, Bcl-2, Bcl-xl and Bcl-w were all detected significantly higher in CNE-2than inCNE-1(P<0.05).4) In CNE-1group, the mRNA expression of Bax was increased andpositively correlated with the dose of radiation, the mRNA expression of Bcl-xl was decreased and unrelated with the dose of radiation, the mRNA expression of Bcl-2washighest in4Gy and then falling down as the dose of radiation increased. In CNE-2group,the mRNA expression of Bak and Bax was increased and positively correlated with thedose of radiation, the mRNA expression of Bcl-w was decreased and negativelycorrelated with the dose of radiation, the mRNA expression of Bcl-xl was decreased andunrelated with the dose of radiation. Conclusion:1) CNE-2is more radiaosensitive thanCNE-1.2）The different Spontaneous apoptosis and Radiation induced apoptosis ishelpful to predict the radiosensitivity of tumor cells.3) The results suggest that thedifferential expression of radiation regulation genes are correlated with radiosensitivity ofNPC cells CNE-1and CNE-2.