Relationship Among Spontaneous Apoptosis Index, Apoptosis-related Proteins And Radiosensitivity Of Nasopharyngeal Carcinoma

Objective : To investigate the correlation among the levels of the spontaneous apoptosis index ( SAI) , the expression of P53 and bcl-2,the radiosensitivity of nasopharyngeal carcinoma . Methods : Thirty-eight patients with nasopharyngeal carcinoma who received irradiation therapy alone without distant metas-tasis were registered in this study. Specimens were obtained before irradiation. The apoptotic index ( AI) of each tissue specimen was evaluated by terminal deoxynucleotidy transferase mediated deoxyuridine triphophate nick-labling ( TUNEL ) assay and expressed as a percentage , Immunohisto-chemical evaluation for P53 and bcl-2, and the clinical response to radical radio-therapy in patients with nasopharyngeal carcinoma.( the clinical radiosensitivity of the tumor) was also performed. Results : (1).Expression of mtp53 and bcl-2 genes:the expre-ssion of mtp53 and bcl-2 genes were divided into four subgroups : -,+,++,+++.The cases of four subgroups of mtp53 expression were 17,14,7,0.The positive rate of mtp53 expression was 55%.The number of bcl-2 expression above four subgroups was 15,13,8,2, respectively .The positive rate of bcl-2 expression was 60.5%. There was a positive correlation between the expression of mtp53 and bcl-2 genes in nasopharyngeal carcinoma .(Rs =0.426,p<0.05). (2) The correlation between the expression of mtP53 and bcl-2 genes, and the spontaneous apoptosis index ( SAI): the mean AI of spontaneous apoptosis of each subgroup of mtp53 and bcl-2 expressions was 0.755%(-),0.566%(+), 0.196% (++),and 0.788%(-), 0.61%(+),0.30%(++),0.11%(+++), respectively . The SAI showed a negative correlation to the expression of P53 protein (Rs =-0. 658,p<0.05); There was an inverse correlation between SAI and the expression of bcl-2(Rs =-0.756,p<0.05);If the expression of mtp53 and bcl-2 genes were divided into three groups :the group of both mtp53 and bcl-2 positive expression, the group of both mtp53 and bcl-2 negative expression, the group of either mtp53 or bcl-2 positive expression,and the mean AI of spontaneous apoptosis of each group was 0.858%,0.365%, 0.659%. There was a significant difference among the three groups (p<0.01). (3) The correlation among the expression of mtP53 and bcl-2 genes, the spontaneous apoptosis index ( SAI), and the rate of nasopharyn-geal tumor regression: The rate of nasopharyngeal tumor regre-ssion showed a negative correlation to the expression of mtP53 gene (40Gy,Rs =-0.564; 70Gy,Rs =-0.526;P<0.05); There was an inverse correlation between the rate of nasopharyngeal tumor regression and the expression of bcl-2 gene(40Gy,Rs =-0.615;70Gy,Rs =-0.702;P<0.05); There was a significantly positive correlation between SAI and the rate of tumor regression.(40Gy,r =0.836;70Gy,r =0.909;P<0.01).When the radiation dose finished 40Gy and 70Gy, the rate of tumor regression of the three groups (the group of both mtp53 and bcl-2 positive expression, the both negative subgroup, the only one of positive expression) was79.94%,31.51%,60.34%,and 90.31%,45.1%,74.44%. Significant difference was statistically observed among the three groups (p<0.01). (4) Other clinic factors and the rate of tumor regre-ssion: sex,age and clinic stage all showed no significant corre-lation with tumor extinction. Conclusion : This study indicates that there is a close rela-tionship among SAI ,expression of p53 and bcl-2,and the short term clinical response in patients with nasopharyngeal carci-noma ; There was likely a synergic effect between p53 and bcl-2 gene. SAI , p53 and bcl-2 are three of the potential marks which could forecast the radiosensitivity of nasopharyngeal carcinoma. When SAI and expression of p53 and bcl-2 were considered simul-taneously , the association with the radiosensitivity was highly significant .