Preliminary Study Of The Expression Of Tumor-suppressing Gene XAF1 In Non-small Cell Lung Cancer

Objectives: The purpose of the study was to investigate the expression of tumor-suppressing gene XAF1 in non-small cell lung cancer, to explore the role of XAF1 in the occurrence and development of non-small cell lung cancer, and provide theoretical evidence for new targeted gene therapy of non-small cell lung cancer.Methods: 51 cases of human non-small cell lung cancer specimens (pathologically diagnosed as squamous cell carcinoma and adenocarcinoma) divided as cancer tissues,cancer adjacent tissues (less than 2cm away from the cancer tissue) and normal lung tissues(more than 5cm away from the cancer tissue)were collected. XAF1 mRNA expression levels were detected by RT-PCR in those specimens of 15 cases of lung cancer; XAF1 protein expression levels were detected in all the specimens by S-P immunohistochemical method. Human non-small lung cancer cell lines (A549,SK-MES-1) were transfected by recombinant Adenovirus Ad5/F35-XAF1 in vitro, XAF1 mRNA and protein expression levels were examined before and after transfection separately, and proliferation and apoptosis of lung cancer cells after transfection was observed by using MTT and Federation of Canadian Municipalities (FCM) method.Results:⑴There were no mRNA expression of XAF1,XIAP of lung cancer tissues in 3 cases by using RT-PCR, Among others the XAF1 mRNA expression in cancer tissues is lower than that in normal lung tissues (P<0.05), there is no significant difference between cancer adjacent ones and normal tissues(P>0.05). The mRNA expression intensity was downregulated from 0.73±0.16 to 0.48±0.14, the ratio was 34.25%,while the XIAP mRNA expression in cancer tissues was higher than that in normal lung tissues (P<0.05), The mRNA expression intensity is upregulated from 0.50±0.11 to 0.72±0.14, the ratio was 30.56%.⑵S-P immunohistochemical method'result is that there are 28 cases showing the positive expression in lung cancer tissues(28/51,54.9%),40 cases in cancer adjacent tissues(40/51,78.4%) and 44 cases in normal lung tissue expression (44/51,86.7%),XAF1 expression in cancer tissues is different from that in cancer adjacent tissues and normal lung tissues (P<0.05),there is no significant difference between normal lung tissues and cancer adjacent ones.⑶The XAF1 expression in cell line A549,SK-MES-1 is lower or absent. After transfection by Ad5/F35-XAF1, the XAF1 mRNA and protein expression is markedly increased in a dose-dependent form, specially in SK-MES-1.⑷MTT method shows that lung cancer cell growth and proliferation was inhibited after transfection by Ad5/F35-XAF1 in titer-dependent form; Flow cytometry results showed that after transfected with different titers of adenovirus, lung cancer cell apoptosis was gradually increased as the titers of Ad5/F35-XAF1 raised within the extent of lethal titer.Conclusion:⑴The results of this study show that the gene XAF1 expression is reduced or absent in human lung cancer tissue and cell lines, while XIAP gene higher in lung cancer tissues, XAF1 plays a important role in inducing apoptosis in the development of lung cancer.⑵Down-regulation of the tumor suppressor gene XAF1 in NSCLC tissues is related with tumer grade,pathological type,stage and lymphnode metastasis, XAF1 is expected to be a new useful tumor marker of lung cancer.⑶Recombinant adenovirus Ad/F35-XAF1 and control adenovirus Ad5/F35-EGFP can transiently transfected into lung cancer lines, XAF1 mRNA and protein expression in lung cancer cells is markedly enhanced, adenovirus is a good vector to be used in gene treatment of NSCLC. ⑷The result of this study shows that a stable recombinant adenovirus XAF1 vector can be transfected successfully into lung cancer cells, which can induce apoptosis and inhibit proliferation of lung cancer cell lines,probably via the activation of apoptotic pathways.XAF1 is expected to be an ideal targeted gene therapy for the effective treatment of lung cancer.