Abstract

The adult human breast gland consists of a branched system of ducts and ductules essentially composed of an inner layer of luminal epithelial cells expressing keratins of simple epithelia and an outer layer of myoepithelial cells expressing keratins of stratified epithelia and a range of contractile filaments. With a view to understanding why some breast carcinomas appear as either basal-like, bimodal or stem cell-derived and others as strictly luminal epithelial-like, we set out to elucidate whether a hierarchy of epithelial differentiation could be demonstrated within the lineages of the human breast gland. For that purpose we have used primary cultures from reduction mammoplasties, immunomagnetic cell sorting and a set of markers for each of the major two lineages. Our initial observations on sorted primary cultures led to the conclusion that myoepithelial cells were lineage restricted in their differentiation repertoire while a subset of cells within the luminal epithelial lineage could convert to myoepithelial cells. Next, we included a three-dimensional reconstituted basement membrane assay in which luminal epithelial cells essentially formed spherical acinus-like structures while myoepithelial cells formed larger solid balls. In an effort to enrich for cells with a broader morphogenic potential we isolated and immortalized a cell type intermediate between luminal and myoepithelial cells, which could make relatively elaborate terminal duct-like structures and organize layers of both luminal-like and myoepithelial-like cells. Currently, we are expanding on our panel of cloned cell lines with normal cellular equivalents in situ as determined by immunochemical portraying. These cell lines are now being tested for their plasticity in culture to further approach a tentative hierarchical scheme for breast epithelial differentiation.

Highlights

  • The remarkable generation of scores of increasingly sophisticated mouse models of mammary cancer over the past two decades has provided tremendous insights into molecular derangements that can lead to cancer

  • We report that somatic mutations of p53 in mouse mammary epithelial cells lead to ERα-positive and ERαnegative tumors. p53 inactivation in pre-pubertal/pubertal mice, but not in adult mice, leads to the development of ERα-positive tumors, suggesting that developmental stages influence the availability of ERα-positive tumor origin cells

  • Genetic alterations commonly observed in human breast cancer including c-myc amplification and Her2/Neu/erbB2 activation were seen in these mouse tumors

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Summary

Mouse models of human breast cancer: evolution or convolution?

Transgenic Oncogenesis Group, Laboratory of Cell Regulation and Carcinogenesis, National Cancer Institute, Bethesda, Maryland, USA. The remarkable generation of scores of increasingly sophisticated mouse models of mammary cancer over the past two decades has provided tremendous insights into molecular derangements that can lead to cancer. The relationships of these models to human breast cancer, remain problematic. P53 inactivation in pre-pubertal/pubertal mice, but not in adult mice, leads to the development of ERα-positive tumors, suggesting that developmental stages influence the availability of ERα-positive tumor origin cells. These tumors have a high rate of metastasis that is independent of tumor latency. Since it is feasible to isolate ERα-positive epithelial cells from normal mammary glands and tumors, molecular mechanisms underlying ERα-positive and ERα-negative mammary carcinogenesis can be systematically addressed using this model

Mouse models for BRCA1-associated breast cancer
Genetic manipulation of the mammary gland by transplantation
The Mutant Mouse Regional Resource Center Program
11 Mammary pathology of the genetically engineered mouse
D Dugger
15 Role of animal models in oncology drug discovery
18 Clinical breast cancer and estrogen
19 Pregnancy levels of estrogen prevents breast cancer
21 The ErbB receptor tyrosine kinases and their roles in cancer
22 Predicting breast cancer behavior by microarray analysis
24 The comparative genetics and genomics of cancer: of mice and men
23 The molecular biology of mammary intraepithelial neoplasia outgrowths
28 Transgenic models are predictive: the herceptin and flavopiridol experience
31 Role of differentiation in carcinogenesis and cancer prevention
30 Genetically engineered mouse models of human breast cancer
34 Hormonal interactions during mammary gland development
35 Function of LEF1 in early mammary development
40 Imaging mouse models of breast cancer with positron emission tomography
42 Ultrasound imaging of tumor perfusion
D Medina
47 In situ to invasive carcinoma transition: escape or release
48 Regulation of human mammary stem cells
50 Stem cells in normal breast development and breast cancer
McKenzie
57 Genomic approaches to drug target discovery using mouse models
58 Target discovery in the postgenomic era
60 From gene expression patterns to antibody diagnostics
Findings
A Korman

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