Chromosomal Genomic DNA Changes In Premalignant Lesions And Carcinomas Of The Breast Associated With Centrosomal Defects

Objective To investigate the expression ofβ-tubulin in premalignant lesion and carcinoma of breast and the significance thereof,and to observe the relationship of its expression with breast cancer clinicopathological features.To investigate the spectrum of genetic changes at specific stages during the development and progression of breast cancer, as well as the relationship between chromosomal changes and centrosome defects. Simultaneously to evaluate the multi-step simple linear progression model for breast cancer,and further to explore the mechanism of breast tumorigenesis on the point of molecular genetics.Methods Immunohistochemistry was used to examine the expression ofβ-tubulin in 50 specimens of premalignant lesion of breast,50 specime ns of in situ ductal carcinoma of the breast(DCIS)and 50 specimens of invasive ductal carcinoma(IDC).30 specimens of normal breast tissues were selected as a control group.Genomic DNA copy number aberrations were analyzed by comparative genomic hybridization in 15 cases of atypical ductal hyperplasia(ADH),15 cases of DCIS and 15 cases of IDC.They were all selected randomly from the cases above with different level ofβ-tubulin expression.Results 1.Significant differences were found among 4 groups(χ~2=25.381,P＜0.05).Compared to the normal breast tissue,β-tubulin expression was higher in premalignant lesions(z=-1.992,P＜0.05),DCIS(z= -3.807,P＜0.05)and IDC(z=-4.161,P＜0.05),respectively.In addition,β-tubulin was expressed at a higher level in DCIS(z=-2.469,P＜0.05)and IDC(z=-3.120,P＜0.05)compared to the premalignant lesions of the breast.But a significant difference ofβ-tubulin expression was not observed between DCIS and IDC(z=-0.909,P＞0.05).2.We found a significant positive relationship ofβ-tubulin expression with axillary lymph node metastasis of IDC(r=0.285,P＜0.05),but no significant correlation with histological grading of IDC(P＞0.05)and nuclear grade of DCIS(P＞0.05).In addition,β-tubulin was expressed at a higher level in Peri-PM with ADH compared to ADH(z=-2.4691,P＜0.05)3.The average number of chromosome copy changes(range)in ADH,DCIS and IDC were 23.07(0-46),14.20(5-42),and 21.73(9-41)respectively.ADH cases showed slightly more chromosome aberrations than the other two groups,although there was not significantly statistical difference among them(P＞0.05).IDC had more losses than ADH and DCIS(P＜0.05)with a statistically significant difference between IDC and DCIS(P＜0.05),while gains among three groups did not differ(P＞0.05).4.We studied the spectrum of genetic changes on the specific stages of breast cancer progression,and found that there was considerable overlap in the pattern of genetic alterations among three groups,including known(gains of 1q,8q,17q,20q,Xq and losses of 8p,13q,16q,17p,22q)and several uncharacterized(gains of 2q,5p,10p,12q,16p,18q etc and losses of 11p13 -pter,11q,14q,Xp etc)regional copy number changes.ADH showed more frequent gain of 17q than that in IDC(P＜0.05),and IDC exhibited higher frequency loss of 22q than that in ADH(P＜0.05).5.The average number of chromosome gains(range) in three groups with different levels ofβ-tubulin expression were 4.36(0—7),8.06(0—28),and 16.78(0—42).The overall frequency of copy number changes was different among them(P＜0.05),and also there was significant difference between any two groups(P＜0.017),while losses among three groups did not differ(P＞0.05).In addition, significant differences of the total copy changes were found among three groups (P＜0.05)with a statistically significant difference between the highest and the lowest groups ofβ-tubulin expression(P＜0.017).Conclusions 1.Centrosome defects may contribute to the earliest stages of breast cancer development and promote tumor progression. 2.Peripheral papillomas(Peri-PM)with ADH may be precursor lesions of breast cancer.3.We observed chromosomal genomic DNA changes in different groups ofβ-tubulin expression,and following the degree ofβ-tubulin expression increased, the genomic changes characteristic displayed an elevating tendency(especially the nu mber of chromosome gains),which can promote breast cancer development and progression. 4.Several common genomic DNA copy number changes shared among ADH, DCIS and IDC make the linear relationship for these three lesions appear possible, but simultaneously the heterogeneity also showed clonal diversification and different pathways of breast cancer progression.