Heterogeneity of mammary lesions represent molecular differences.
BACKGROUND
Human breast cancer is a heterogeneous disease, histopathologically, molecularly and phenotypically. The molecular basis of this heterogeneity is not well understood. We have used a mouse model of DCIS that consists of unique lines of mammary intraepithelial neoplasia (MIN) outgrowths, the premalignant lesion in the mouse that progress to invasive carcinoma, to understand the molecular changes that are characteristic to certain phenotypes. Each MIN-O line has distinguishable morphologies, metastatic potentials and estrogen dependencies.


METHODS
We utilized oligonucleotide expression arrays and high resolution array comparative genomic hybridization (aCGH) to investigate whole genome expression patterns and whole genome aberrations in both the MIN-O and tumor from four different MIN-O lines that each have different phenotypes. From the whole genome analysis at 35 kb resolution, we found that chromosome 1, 2, 10, and 11 were frequently associated with whole chromosome gains in the MIN-Os. In particular, two MIN-O lines had the majority of the chromosome gains. Although we did not find any whole chromosome loss, we identified 3 recurring chromosome losses (2F1-2, 3E4, 17E2) and two chromosome copy number gains on chromosome 11. These interstitial deletions and duplications were verified with a custom made array designed to interrogate the specific regions at approximately 550 bp resolution.


RESULTS
We demonstrated that expression and genomic changes are present in the early premalignant lesions and that these molecular profiles can be correlated to phenotype (metastasis and estrogen responsiveness). We also identified expression changes associated with genomic instability. Progression to invasive carcinoma was associated with few additional changes in gene expression and genomic organization. Therefore, in the MIN-O mice, early premalignant lesions have the major molecular and genetic changes required and these changes have important phenotypic significance. In contrast, the changes that occur in the transition to invasive carcinoma are subtle, with few consistent changes and no association with phenotype.


CONCLUSIONS
We propose that the early lesions carry the important genetic changes that reflect the major phenotypic information, while additional genetic changes that accumulate in the invasive carcinoma are less associated with the overall phenotype.
Namba
Ruria
R
Department of Pathology and Laboratory Medicine, School of Medicine, University of California at Davis, Sacramento, CA 95817, USA. rnamba@ucdavis.edu <rnamba@ucdavis.edu>
Maglione
Jeannie E
JE
Davis
Ryan R
RR
Baron
Colin A
CA
Liu
Stephenie
S
Carmack
Condie E
CE
Young
Lawrence J T
LJ
Borowsky
Alexander D
AD
Cardiff
Robert D
RD
Gregg
Jeffrey P
JP
D000818:Animals; D002278:Carcinoma in Situ / Q000378:metabolism / Q000473:pathology; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000235:genetics* / Q000473:pathology*; D045744:Cell Line, Tumor; D043171:Chromosomal Instability; D002869:Chromosome Aberrations; D033481:Chromosomes, Mammalian; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018740:Genetic Heterogeneity; D042341:Gonadal Hormones / Q000494:pharmacology; D008325:Mammary Neoplasms, Experimental / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D009362:Neoplasm Metastasis / Q000473:pathology; D009376:Neoplasms, Hormone-Dependent / Q000378:metabolism / Q000473:pathology; D009693:Nucleic Acid Hybridization / Q000379:methods; D020411:Oligonucleotide Array Sequence Analysis; D011230:Precancerous Conditions / Q000378:metabolism / Q000473:pathology
D042341:Gonadal Hormones