Expression And Mutation Of Apoptosis-Related FADD Gene In Non-Small Cell Lung Cancer

ObjectiverTo study the expression and mutation of FADD(Fas-associated death domain) gene in Non-Small Cell Lung Cancer (NSCLC) and to investigate the spontaneous apoptotic cells in NSCLC, and to evaluate the possible effect and mechanism of FADD gene on the development of NSCLC.Methods: Immunohistochemistry (streptavidin peroxidase conjugated method,S-P method) and polymerase chain reaction and single-strand conformation polymorphism (PCR-SSCP) methods were respectively used to detect FADD gene exonl mutation and its protein expression in 62 samples of resected NSCLC and 13 samples of normal adjacent lung tissues. 30 cases of resected NSCLC were studied by in situ hybrization(ISH) technique for FADDmRNA expression. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick labeling (TUNEL) was employed to determined apoptotic cells in 62 cases of NSCLC.Results :1, Immunohistochemistry revealed that fifty cases (50/62,80.6%) of NSCLC were detected to express FADD protein .The positive rate in NSCLC was lower than that in normal adjacent lung tissues which showed 100% cases harbored FADD protein, but with no statistic significance(P>0.05). Most of NSCLC showed moderate to strong FADD protein expression(36/62), while most of normal adjacent lung tissues showed weak expression(l 1/13), the expression level in NSCLC was higher than that in normal smaples with statistic significance(P<0.05). The expression of FADD was closely correlated with NSCLC differentiation (rs=0.411, P<0.01). No relationship was found between FADD expression and other clinical features, such as age ,tumor histology,metastasis and clinical stage(P>0.05).2, ISH showed that in NSCLC, the positive rate of FADDmRNA was 80%(24/30), its concordant rate with corresponding FADD protein expression(25/30) was 90%, nosignificant difference between the expression of FADD as detected by the two different techniques(P>0.05).3, Altogether there were 4 cases of FADD gene mutation in 62 NSCLC by PCR-SSCP, while no mutation was found in all normal adjacent lung tissues. The analysis revealed that the mutation of FADD gene was positively correlated to the status of lymph node metastasis (rs=0.379, .PO.01), but no relationship was found between FADD expression and other clinical features(P>0.05).4:k Positive apoptotic cells could be observed in all cases of NSCLC with TUNEL method, the average AI was 1.63%?.04% .The apoptotic level in squmaous cell carcinoma was higher than that in adenocarcinoma(P<0.05). No relationship was found between apoptotic level and other clinical features, such as differentiation and clinical stage(p>0.05).5, The apoptosis indexes of the 4 cases which mutated are lower than the mean level, although the 4 cases of NSCLC showed protein expression. No mutation was found in 12 NSCLC which showed negative protein expression, there was no relationship between the loss of protein expression and gene mutation of FADD(P>0.05). More TUNEL positive cells were detected in those cases which showed moderate to strong FADD positive, as compared with negative or weak FADD positive cases, and the apoptosis was closely associated with FADD expression in NSCLC (rS=0.599VP<0.001).Conclusions: Our study found that FADD protein expression was closely correlated with the apoptotic level of cells in NSCLC which demonstrated the important pole of FADD in cell apoptotisis.The reseach also indicated that there existed the FADD gene mutations in Non-Small Cell Lung Cancer, and the alterations of the FADD gene might lead to the loss of its apoptotic function and contribute to the pathogenesis of some NSCLCs.