The Screening Of Proteins Associated With The Maligannat Transformation Of Bronchioloalveolar Adenocarcinoma

Background:Lung adenocarcinoma (ADC) is the most common histopathologic type, accounts for 30% of all lung caners and has an overall 5-year survival of 17%. The 2004 World Health Organization (WHO) classification recognized a particular subtype, bronchioloalveolar carcinoma (BAC), for its noninvasive features and excellent prognosis. BAC displays a growth of neoplastic cells along pre-existing alveolar structures (lepidic growth) without evidence of stromal, vascular, or pleural invasion. According to its histopathological features, it can be classified into three subtypes:mucinous, non-mucinous and a mixed variant. The most common subtype is non-mucinous BAC. An increasing number of researches show that ADC putatively involves progression from atypical adenomatous hyperplasia (AAH) through non-mucinous BAC to adenocarcinoma with BAC features (AWBF). According to the newest classification of adenocarcinoma, BAC is a kind of adenocarcinoma in situ (AIS) with excellent prognosis, but it has potential of malignant progression to invasive adenocarcinoma.In present opinion, lung carcinogenesis is a multistage process. Such progression from AAH to BAC is associated with progressive accumulation of genetic and molecular abnormalities, leading over time to invasive adenocarcinoma. However, genetic effect will be exhibited by changes of proteome. The protein is the executants of cell function. Hence, if we can further study the association between new 33 changes of gene functions and BAC malignant transformation, it will play an important role in revealing the carcinogenesis of BAC, designing new therapeutic drugs and evaluating the prognosis. In the present study, two-dimensional polyacrylamide gel electrophoresis (2-DE) combined with mass spectrometry was used to detect the differentially expressed proteins in BAC and AWBF and to verify the results of 2-DE, one protein was detected in cancer tissues by western-blotting and immunohistochemistry techniques.Two parts are included in this study:PART 1 Comparative proteomic analysis of BAC and AWBFObjective To find BAC malignant progression associated proteins by comparing the protein expression profiles between BAC and AWBF.Methods Total proteins extracted from BAC and AWBF tissues were separated by two-dimensional polyacrylamide gel electrophoresis (2-DE). High quality 2-DE profiles were obtained and analyzed by Imagemaste and PD-QUEST software to screen differentially expressed protein spots. Those spots were identified by mass spectrometry.Results 2-DE patterns of lung adenocarcinoma tissues with high resolution and reproducibility were obtained.37 significantly differentially expressed protein spots were screened, among which 21 protein spots were identified to be up-regulated and 17 down-regulated in AWBF compared with BAC.10 proteins were identified by mass spectrometry. The identified proteins included VDAC2 (voltage-dependent anion-selective channel protein 2),SerpinAl (serine protease inhibitor A1),MRE11 (meiotic recombination gene 11 homologA),Annexin2,PGK1 (phosphoglycerate kinase 1),PDIA3 (protein disulfide-isomerase A3) and so on.Conclusions The protein expression profiles of AWBF were similar to ones of BAC, which presented a difference of expression level without "all or none" changes.10 significantly differentially expressed proteins were screened and identified, which may correlate with malignant progression of BAC and provide new clues for the further study of mechanisms of lung adenocarcinoma.PART 2 Expression of MRE11 in BAC and invasive adenocarcinomaObjective To detect the expression of MRE11 protein in human BAC and invasive adenocarcinoma tissues.Methods 5 samples of BAC and 20 invasive adenocarcinoma tissues tissues were collected and proved to be lung adenocarcinoma by HE staining. The protein levels of MRE11 were detected and analyzed by western-blotting technique. The sites of MRE11 were detected by streptavidin peroxidase immunohistochemistry techniques.Results Compared with BAC tissues, the expression levels of MRE11 protein were significantly higher in invasive adenocarcinoma tissues. The average IHC staining scores of MRE11 in BAC was 3.8±1.9, significantly lower than that in invasive adenocarcinoma tissues (5.4±0.9) (p<0.05).Conclusions The expression of MRE11 were higher in invasive adenocarcinoma tissues than in BAC tissues. Therefore, MRE11 may be associated with the malignant transformation of BAC.