Expressions Of Frat And β-catenin In Lung Cancer And Their Clinicopathological Correlations

IntroductionCell signaling is one of the advanced and activated subjects in the field of biomedicine research nowadays.Wnt-signal transduction composed of a lot of oncogene and anti-oncogene codogenic proteins is a pathway by which transfers growth stimulate signals.It plays important roles during embryonic development and is correlated with stem cell self-renewal and differentiation and leads to tumor formation when aberrantly activated.β-catenin is the key point molecule in both Wnt-signal transduction and E-cadherin/catenin.When it accumulates in the nucleus,β-catenin loses its function as a cell-adhesion molecule,which activates the Wnt signaling pathway and switches on transcription of target genes such as c-myc,cyclinD1 or c-jun et al,resulting in proliferation and metastasis of tumor cells.Frat proteins are positive regulator of Wnt-signal transduction.By binding to GSK3,Frat prevents the phosphorylation and concomitant degradation ofβ-catenin and allows the activation of downstream target genes byβ-catenin/TCF complexes.By means of tissue chip technique and immunohistochemical method,the cases of lung carcinoma were examed to detect the expression of Frat andβ-catenin.The aim of this study is to investigate the protein expression of Frat andβ-catenin and their clinicopathological correlations in lung cancer and the correlations between histology and differentiation in NSCLC. Materials and Methods1.MaterialsTissue chip with 52 cases of lung cancer and 12 cases of precancerous tissue was bought from Fanpu Biotechnology Limited Company of Guilin.Patient's mean age is 58.17 years(range 27-80 years),male:female ratio is 1.89:1(34:18);Histology separate criteria of WHO(2004)about lung tumor:18 cases of squamous cell carcinoma,25 cases of adenomcarcinoma,5 cases of small cell carcinoma,3 cases of adenosquamous carcinoma,1 cases of large cell carcinoma.In NSCLC:12 cases of well differentiated degree,18 cases of moderately differentiated degree,17 cases of poorly differentiated degree.According to lung carcinoma P-TNM staging standard of UICC in 1997:43 cases of stageⅠ,6 cases of stageⅡ,3 cases of stageⅢ,0 case of stageⅣ.Main reagents:polyclonal anti-Frat antibody;monoclonal anti-β-catenin antibody; SP reagent box;DAB reagent box.Main instruments:optical microscope,experiment wet box,incubator,refrigerator.2.MethodsMethod:The expression of Frat andβ-catenin was determined by SP immunohistochemical method in lung carcinoma.Statistic Analysis:SPSS 13.0 statistic software was applied.All data were analyzed with x~2 test and P＜0.05 was regarded as statistically significance.Results1.Expression ofβ-cateninThe abnormal cell expression rate ofβ-catenin in lung cancer was 71.15%.The abnormal cell expression rate ofβ-catenin in well,moderately and poorly differentiated NSCLCs were 41.67%(5/12),61.11%(11/18)and 100%(17/17).There was a significant difference(x~2=12.601,P=0.002).The abnormal cell expression rate ofβ-catenin is independence with patients'age(P=0.571),gender(P=0.603),tumor type(P=0.366)and TNM staging(P=0.280).In precancerous tissues,staining ofβ-catenin is on membrane,and seldom on ectopic expression.2.Expression of FratThe positive expression rate of Frat in lung cancer was 75%.The positive expression rate of Frat in well,moderately and poorly differentiated NSCLCs were 41.67%(5/12),83.33%(15/18)and 88.24%(15/17).There was a significant difference in Frat expression among well,moderately and poorly differentiated NSCLCs (x~2=9.229,P=0.01).The expression of Frat is positively correlated with the abnormal cell expression ofβ-catenin.But the positive expression rate of Frat is independence with patients'age(P=1.000),gender(P=0.736),tumor type(P=0.571)and TNM staging(P=0.541).In precancerous tissues,Frat seldom expressed.Discussionβ-catenin is the key point molecule of E-cadherin/catenin complex,which accommodates interallogenic cell myxoadnexal.Simultaneously,freeβ-catenin plays a role in Wnt-signal transduction.When it accumulates in the nucleus,β-catenin loses its function as a cell-adhesion molecule,which activates the Wnt signaling pathway and switches on transcription of target genes such as c-myc,cyclinD1 et al,resulting in proliferation and metastasis of tumor cells.There is a tremendous difference in the expression rate ofβ-catenin in various kinds of tumors.Perhaps it was because of the different of tumor type and assessment standard.Our study showed that the abnormal cell expression rate ofβ-catenin was 71.15%in lung cancer.The normal expression ofβ-catenin can be seen more easily in well differentiated NSCLCs than in moderately differentiated NSCLCs.We can see reduced staining ofβ-catenin on membrane with cytoplasmic or nucleus accumulation in poorly differentiated NSCLCs.The abnormal cell expression rate ofβ-catenin is independence with TNM staging,which is resemble with Xu Hongtao'research study of 100 cases of NSCLC.There are many causes of abnormal expression ofβ-catenin,except for genetic mutation,any abnormity in degradation ofβ-catenin can induce abnormal express and accumulation,so the abnormity of key proteins that GSK-3 and APC mediated degradation ofβ-catenin maybe is significance causes of abnormal expression ofβ-catenin.Frat is GSK3-binding protein.Wnt signaling through the Frizzled receptor and mediated by Dishevelled,acts to inhibitβ-catenin hyperphosphorylation by GSK3.Frat has been advocated as the missing link that bridged signaling from Dvl to GSK3.By binding to GSK3 Frat prevents the phosphorylation and concomitant degradation ofβ-catenin,leading to the accumulation of cytosolicβ-catenin and activation of TCF/LEF-1 transcription factors.The Fratl proto-oncogene was first identified as a gene contributing to tumor progression in T-cell lymphomas.The biological function of Frat remained elusive until its Xenopus homologue GBP was isolated as a GSK3-binding protein and was shown to be an essential component of the maternal Wnt-signaling pathway.Dajani Rana believes that Fratl which binds to Dishevelled,and to GSK3 in competition with Axin,thereby displacing it from the axin-APC complex and preventing its access toβ-catenin.Frat which binds to Dishevelled activated by Wnt signalling can bind with GSK3,and the interaction of Dvl-1 with Fratl was enhanced by CKIε.Jonathan thinks GSK3-binding protein Frat regulates the nuclear export of GSK3 and the role of Frat in mediating GSK3 nuclear export have important implications for the control of the substrate access of GSK3 in several signaling pathways.Saitoh had studied the express of proto-oncogene Fratl in human cancer.Fratl mRNA was almost ubiquitously expressed in human pancreatic cancer cell lines and gastric cancer cell line.Expression level of Fratl mRNA was relatively higher in esophageal cancer cell lines,a cervical cancer cell line and breast cancer cell lines,Our study discovered in lung cancer the positive expression rate of Frat was 75%.There was not a significant difference in Frat expression among lung cancer histology.In NSCLC,Frat expression was significantly higher in poorly differentiated tumors than in well or moderately differentiated tumors,and Frat expression was higher in moderately differentiated tumors than in well differentiated tumors.The difference has statistical significance(P=0.01).In this study,the expression of Frat is positively correlated with the abnormal cell expression ofβ-catenin,It showed that express of Frat had up-regulation effect on cell accumulation ofβ-catenin in NSCLC,and then promoted its switching on transcription of target genes,participating in tumor generation.These results have determinate significance for further understand of lung cancer's genesis and development.There was no difference in Frat expression among TNM stageⅠ,ⅡandⅢ.This result maybe was related with less cases adopted in stageⅡandⅢ.So this conclusion was not confirmed,and it needs further confirm by enlarging case numbers in future.Conclusion1.The abnormal cell expression ofβ-catenin is associated with pooly differentiated NSCLCs.2.The expression of Frat is positively correlated with the degree of tumor differentiation and the abnormal cell expression ofβ-catenin.