Preliminary Study Of The Expression Of Tumor-suppressing Gene XAF1in The Cisplatin–resistance Lung Adenocarcinoma Cell Line

Objectives: The purpose of the study was to investigate the expressionof tumor-suppressing gene XAF1in the cisplatin-resistance lungadenocarcinoma cell line, to explore the role of XAF1in the occurrence anddevelopment of cisplatin-resistance in A549/DDP cell line, and providetheoretical evidence for new targeted gene therapy of cisplatin-resistance lungadenocarcinoma.Methods: In this study, cultured human non-small cell lung cancercisplatin-resistant cell lines A549/DDP and its parental line A549, MTTmethod for the test of cisplatin-resistance index in A549/DDP cell; usingsemi-quantitative reverse transcription-polymerase chain (RT-PCR), detectthe XAF1and XIAP mRNA expression levels in two kinds of cells above；A549/DDP cell lines were transfected by recombinant Adenovirus Ad5/F35-XAF1in vitro, the biological behavior of lung cancer cells after transfectionwas observed by using Federationof Canadian Municipalities (FCM) method,and the XAF1mRNA expression levels were examined after transfection bysemi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) detection of cells the expression of XAF1mRNA levels.Results: The IC50values of cisplatin in A549and A549/DDP cells were5.52±0.12μmol/L and34.96±0.74μmol/L, the resistance index of A549/DDPwas6.33. A549/DDP cells was identified as cisplatin-resistant NSCLC cellline.RT-PCR results show that the XAF1mRNA expression levels lowered inA549/DDP cells than in normal A549cells (P＜0.05), compared withcisplatinum for48h in A549cells (apoptotic cells), the XAF1mRNAexpression downregulated in normal A549cells (P＜0.05); The XIAP mRNAexpression in A549/DDP cells was higher than in the apoptotic cells (P＜0.01)and the A549cells (P＜0.05), and the XIAP mRNA expression in normalA549cells was higher than in apoptotic cells (P＜0.05). A549/DDP cellgrowth and proliferation was inhibited after transfection by Ad5/F35-XAF1intiter-dependent form; Flow cytometry results showed that, after transfectedwith different titers of adenovirus, lung cancer cell apoptosis was graduallyincreased as the titers of Ad5/F35-XAF1raised within the extent of lethal titer.After transfection by Ad5/F35-XAF1, the XAF1mRNA expression ismarkedly increased in a dose-dependent form (P＜0.05)。Conclusion：(1) The results of this study showed that the tumor suppressor geneXAF1in cisplatin-resistant lung adenocarcinoma cell line decreasedexpression or absence and the XIAP gene expression was significantly enhanced，XIAP as inhibitor of apoptosis gene has been affirmed，and theXAF1may play a role in the lung adenocarcinoma cisplatin resistanceprocess.(2) Recombinant adenovirus Ad/F35-XAF1and adenovirus Ad5/F35-EGFP in comparison can transiently transfected into cisplatin-resistant lungadenocarcinoma cell line，the XAF1mRNA expression compared with beforetransfect was significantly enhanced, showing that the recombinantadenovirus is a gene therapy for cisplatin-resistant lung adenocarcinoma.(3) The result of this study shows that a stable recombinant adenovirusXAF1vector can be transfected successfully into lung cancer cells, which caninduce apoptosis and inhibit proliferation of cisplatin-resistant lungadenocarcinoma cell lines，probably via the activation of apoptotic pathways.XAF1is expected to be an ideal targeted gene therapy for reversing thecisplatin-resistance in the lung adenocarcinoma.