Expression Of Caveolin-1 In Breast Carcinoma And Its Significance

INTRODUCTIONBreast carcinoma is one major malignant tumors that endanger women's healthand the leading cause of women's death. Thus elucidation its pathogenesis is of greatsignificance for a better diagnosis and treatment. Caveolae is the principle structure ofmembranes. Caveolin-1 is an important component of it. It expresses in many types ofmature differential cells(epithelium,fat cell,endothlium). Caveolin-1 has been shownto play a role in lipid metabolism,cell proliferation and regulating cell movement. Inthe past few years, it gives our attention to look sharp that this research, we appliedimmunohistochemistry to examine the expression of Caveolin-1 in human breastcarcinoma and normal breast tissue, as well as it relationship with clinical pathologicfactors.MATERIALS AND METHODS1. materialsTotal of 84 cases of breast invasive carcinoma, all from the department of thoracicsurgery of Liaoning Province Carcinoma Hospital, between the period of 1997-2000,were diagnosed by the department of pathology. The specimen fixed in 10%formaldehyde, was buried in paraffin. The group was consisted of female, whose ageranged 25-73, average 46. The were divided by its pathological type and stagingaccording to AJCC and UICC Staging criteria(1988). 11 cases were classified as stageⅠ,5 cases were classified as stageⅡ, 18 cases were classified as stageⅢ4 caseswere classified as stageⅣ. 13 cases were high differential, 28 cases middle differential and 43 cases low differential. 45 cases accompanied with lymph nodemetastases, and 39 cases do not. No patinent received chemotherapy or radioptherapy.Polyclonal anti-caveolin-1 was bought from Santa Cruz Company of America,monoclonal anti-CerB-2,ER,S-P kit and DAB were purchased from MaxinBiocompany.2. methodsFor immunostainy, streptavidin peroxidase complex (S-P) method was used.Thesections were dewaxed, and Caveolin-1(1:100) ER and CerbB-2 were all treated withhydrogen peroxide in methanol to quench the endogenous peroxidase activity, the colorwas developed with diaminobenzidine and the sections were counterstained theharmatoxylin. Negative control was carried out by replacing the primary with PBS3. evaluation of the specimensEach secion was read by two doctors of pathology, the positive secion wasdetermined by both of them. Five views were examined per slide, and 100 cell wereobserved per view. Caveoin-1 lies in the nucleus and (or) cytoplasm of thecell. CerbB-2 lies in cytoplasm of the cell, ER lies in the nucleus of the cell. Thepositive stained parts show brown. Normal epitheliums of mammary ductus wereselected as control. (1)according to positive cell percents, 0 fen, immunostaining werepresent in less than 25%. 1 fen, immunostaining were present more than 26% and lessthan 50%. 2 fen, immunostaining were present more than 51% and less than 75%. 3fen, immunostaining were present more than 76% and less than 100%. (2) Accodingto immunostaining intensity, 0 fen, no staining was present. 1 fen, immtmostainingwas weak. 2 fen, immunostaining was strong. Less than 2 fen was negative, Morethan 2 fen and less than 5 fen was positive.4. Statistics analysisAll the data were analyzed with SPSS for Windows 11.0. The relationshipbetween the expression of caveolin-1 and clinical pathology characters was analyzedwith Person chi-squared test. The cut-off for statiscal significance was defined as P＜0.05.ResultCaveolin-1 is membranous/cytoplasmic expression protein expressed in normalmammary ductal epithelium and vascular endothelium. The positive rate of Caveolinwas 45.2%(38/84) in 84 primary breast carcinoma. The positive rate was 66.7% in T1group, 41% in T2 group, 36.4% in T3 group, there was not a significant associationexcept between T1 and T2+T3(p＜0.05). Among the stageⅠ,Ⅱ,Ⅲ,Ⅳ, positiverate of Caveolin-1 were 81.8% (9/11),45.1% (23/51),33.3% (6/18),and25%(1/4) respectively, the difference was significant (p＜0.05). Thepositive rate of Caveolin-1 with lymph node metastases were 31.3%, 66.7 % withoutlymph node metastases. There was association between the two groups. Theexpression of Caveolin-1 has no relationship with differentiation,ER receptor,theexpress of CerbB-2 and age et.DiscussionThe generation, development and metastasis of tumor, related with many factors,is a complex multiple-phases process involved the mutation and activation ofoncogenes, the deletion or hypermethylation of tumor suppressor genes, theturbulence of modulating apoptosis mechanism et. Many studies show CAV-1 genelocus 7q31.1 that is deleted in a variety of human cancers, and it has been proposedthat tumor suppressor gene may lie within the region. It has been confirmed in humanbreast cancer tissue and MCF-7 cell lines. Others reports that Caveolin-1 has a role inregulating cell amplification and mitogenesis, the expression of it reduces when themammary and lung cells transform. Reverse inhabitation or expression of Caveolin-1 can enough induce cell transformation, but immit it to fibroblasts and breast cancercell lines can inverse its malignant feature.Caveolin-1 is considered to be a candidatetumor suppressor genes of twenty tumors.This study shows that Caveolin-1 is abundant in normal human mammary ductalepithelial cls and vascular endothelial cells, whereas its expression is significantly reduced in breast cancer cells, this result consistes with the reports of breast cancer,lung cancer,stomach cancer et. According to the reducing of the expression ofCaveolin-1, it is considered to be associated with the mutation of P132L and promotermathylation by molecular mechanism recently. Lee H et. founded that theCaveolin-1 gene mutated in up to 16% in human breast cancer and itscells. Engelman Ja et. found that the CPG region of Caveolin-1 gene fully methylatedand the expression of protein was down-regulated in human breast carcinomas cellslines (MCF-7,T-47D), however, in normal human epitheliums do not methylated,and protein is highly expressed. But Chen ST only found that 25% of CPG site ofCaveolin-1 appeared four types of methylation without mutation. A number of testsdemonstrate that the scoffiold domain of Caveolin-1 which can inhibit the activity ofprotein kinase can inhibit the activity of many signaling molecules related with cellproliferation,apoptosis,adheresion,movement as EGF-R,Raf,ProG,C-srctyrosine kinase,MEK-1 and ERK-2 et. and these molecules also arouse P42-44MAPKand its up-stream nuclear transcription factor Jun,Fos,CyclinD pathway. At the sametime, this study shows the expression of Caveolin-1 and tumor size has significantassociation between T1 and T2+T3,and the relationship is negative. So the expressionof Caveolin-1 decreasing inhabit its negative regulation. The excessive proliferationand abnormal apotosis of normal human mammary epithelium and carcinoma cellsmay finally result in the generation,development of tumor,and the work are carryingthrough.In vitro it show Caveolin-1 can inhabit the activity of CerbB-2 tyrosine kinase areceptor of epidermal growth factor (EGF) family, the abnormal expression ofCerbB-2 can also down-regulate Caveolin-1. In this study, The positive rate ofCaveolin-1(37.5%) attended by CerbB-2 expression is much lower than the negativerate (61%), but they have no statistical relationship, This may attribute to the smallcases of each team, because only 60% of the total cases have been examined. Recentstudies suggest Caveolin-1 contributes to the formation of E-Cadherin/β-Catenin enhance the juncture and communication of cells. Up-regulation of Caveolin-1 canreduce the movement of breast cancer and lung cancer cells. In addition, Fiucci et.find Caveolin-1 has negative relation with MMPs and VEGF. Our results show theexpression of Caveolin-1 is significantly lower in the cases with lymph node metastasisthan that of without lymph node metastasis, progressive down-regulation ofCaveolin-1 is correlated to breast carcinogenesis, it indicate that Caveolin-1 directly orindirectly increases the invade and metastasis of carcinoma cells by influence thedistributing ofβ-Catenin and/or the expression of MMPs,WEGF,CerbB-2. It isobvious that further discussion the relationship between Caveolin-1 and thesemetastasis related factors can strengthen us to understand the cause of invade andmetastasis of breast cancer.A number of published studies report that Caveolin-1 acts as tumor suppressorgene, but There are many debates about many types of tumor, even the sametumor. The expression of Caveolin-1 increases in hyalocyte and prostate cancer, andhas a positive relationship with lymph node metastasis and staging, This is contrary toOur results in breast cancer tissue, however, according to the relationship betweenthe expression of Caveolin-1 and ER,PgR, We and Chrn ST have the sameopinion, but Sagara Y argues against the results.As we all know, tumor size,lymph node metastasis,staging all independly affectsthe prognosis of breast cancer. Our study indicates the expression of Caveolin-1 hasclosely association with the three factors. So it is a hard task to quest for therelationship between Caveolin-1 and the prognosis of breast cancer.Conclusion1. Caveolin-1 showed abnormal expression in breast cancer, abnormal expression wasassociated with tumor size and lymph node metastasis, progressivedown-regulation of Caveolin-1 is correlated to breast carcinogenesis.2. The positive rate of Caveolin-1 has no relation with age,histological type, CerbB-2, and receptor status.