Human Ductal Carcinoma In Situ Research Articles

Mammary intraepithelial neoplasia outgrowths (MINO): MINO and human ductal carcinoma in situ

Mouse models of human mammary intraepithelial neoplasia have been described in a number of contexts. In general, descriptions of early stages of progression in genetically engineered mice that go on to develop invasive and even metastatic carcinomas are compared with human ductal carcinoma in situ (DCIS). In some instances, lesions with phenotypic similarity to human DCIS are compared, even without evidence of progression. The terminology for these processes in the mouse mammary gland requires precise definition. Otherwise, it is impossible to compare the variety of available models for study utility. Experimentally driven operational definitions are optimal. We have studied a series of transplantable mammary intraepithelial neoplasia outgrowths (MINOs) derived from the transgenic mouse mammary tumor virus promoter-driven polyoma virus middle T oncogene FVB mice. We have characterized their behavior experimentally and morphologically. Experimentally, these MINOs meet the most stringent criteria to be considered premalignant. They are capable of orthotopic growth in the gland cleared mammary fat pad, are without being capable of ectopic (subcutaneous) growth, and have a consistent transformation to the fully malignant behavior (capable of ectopic growth)–defined therefore as invasive carcinoma. Morphologically, there is a high degree of heterogeneity both within and between individual MINO lines. Nevertheless, all consistently transform to behaviorally and morphologically similar carcinomas. MINOs therefore compare closely with human DCIS. Human DCIS is similarly defined by its universal potential (if incompletely treated) to progress to invasive carcinoma, despite heterogeneity within a given breast or between individual patients. We extend the comparison using immunophenotypic analysis, and gene expression analysis. Overall, our goal is to better model human DCIS, in a reproducible and robust mouse model system suitable for interventional studies. By creating a serially transplantable series of MINOs we have removed much of the variability which would otherwise confound such study. Derivation of MINOs from a variety of genetically engineered mice backgrounds may provide additional critical reagents for the preclinical study of DCIS.

The molecular biology of mammary intraepithelial neoplasia outgrowths

Genetically engineered mice have been used extensively to model human breast cancer. Yet few have been developed and characterized to model the progression from hyperplasia to cancer. We have developed a transplantable model for mammary hyperplasia that progresses to invasive carcinoma, effectively mimicking human ductal carcinoma in situ (DCIS). As such, this provides a unique model for chemoprevention trials for high-risk premalignant breast lesions. These transplantable lines, also known as mammary intraepihelial neoplasia outgrowths (MIN-Os), were developed by our group and are derived from the mammary hyperplasia of mouse mammary tumor virus-polyomavirus middle T (mT) transgenic mice. The polyomavirus transgene provides an attractive model for human mammary carcinoma, as it is capable of transforming cells by triggering signal transduction pathways that have been implicated to be activated by erbB2, through interactions between its mT gene product and key cellular signaling proteins–such as c-Src, Shc, and phosphatidylinositol 3-kinase, which have all been implicated as important in human breast cancer. These transplanted lines are heterogeneous; however, within a line, through multiple generations, the MIN-Os show consistent growth rate, histopathology, and latency to tumor formation. The lines and the tumors that arise from them maintain their defining characteristics in 'tests by transplantation'. Histopathologically, the MIN-Os resemble human DCIS, and the resulting mammary invasive carcinoma resembles human invasive ductal carcinoma. With gene expression studies, we have found dysregulated genes and pathways that have been shown to be similarly altered in human DCIS, suggesting that our model is related to DCIS not only at a histopathological level, but also at a molecular level. These gene expression studies suggest the importance of stromal–epithelial interactions, the extracellular matrix proteoglycan-mediated regulation of cell proliferation signaling, actin cytoskeleton organization, and the insulin-like growth factors and their effectors in the transition from hyperplasia to transformed invasive carcinoma. We have begun using this human DCIS model for developing chemoprevention strategies for high-risk breast lesions. With in vitro assays, we have ranked inhibitors for effectiveness and inclusion in in vivo studies. We have demonstrated that inhibitors to phosphatidylinositol 3-kinase and related downstream mediators are effective in inhibiting growth. This mouse model provides an attractive platform that is amenable to interventional studies and chemoprevention preclinical trials, with easily measurable end-points for testing effectiveness of agents while providing tissue for correlative molecular studies.

Soy isoflavone genistein modulates cell cycle progression and induces apoptosis in HER-2/neu oncogene expressing human breast epithelial cells

In the multistep progressive pathogenesis of human breast cancer, comedo ductal carcinoma in situ (DCIS) represents a preinvasive precursor lesion for therapy resistant invasive cancer. Human tissue derived cell culture models exhibiting molecular similarities to clinical DCIS facilitate an important preclinical mechanistic approach for evaluation of preventive efficacy of natural and synthetic chemopreventive compounds. Natural phytochemicals present in fresh fruits, vegetables and grain products are likely to offer protection against cancer. The clinical efficacy of these natural phytochemicals, however, depends on extrapolation, and is therefore equivocal. The present study determined whether the natural soy isoflavone genistein (GEN) inhibited aberrant proliferation in 184-B5/HER cells (a model for human comedo DCIS) and identified possible mechanisms responsible for its efficacy. Human reduction mammoplasty derived HER-2/neu oncogene expressing preneoplastic 184-B5/HER cells represented the experimental system. Flow cytometry and cellular epifluorescence based assays were utilized to quantitate the alterations in cell cycle progression, cellular apoptosis, and in the status of cell cycle regulatory and apoptosis-associated gene product expression. The 184-B5/HER cells exhibited specific immunofluorescence to p185HER, p53, EGFR, but not to ERalpha, thus resembling comedo DCIS. Treatment of 184-B5/HER cells with GEN resulted in a dose-dependent decrease in the viable cell population, increase in the G0/G1:S + G2/M ratio and enhancement of sub G0/G1 (apoptotic population). Exposure to the maximum cytostatic 10 microM dose of GEN down-regulated HER-2/neu mediated signal transduction as evidenced by a 73.9% decrease (p=0.001) in p185HER specific, and a 89.8% decrease (p=0.001) in phosphotyrosine specific immunofluorescence. The increase in G0/G1:S + G2/M ratio in response to the treatment with 10 microM GEN was associated with a 85.5% decrease (p=0.001) in immunoreactivity to PCNA and a 128.6% increase (p=0.004) in immunoreactivity to the cyclin dependent kinase inhibitor p16INK4. The induction of apoptosis by GEN was associated with a 52.8% decrease (p=0.001) in the immunoreactivity to antiapoptotic Bcl-2 and with a 195.9% (p=0.001) increase in the immunoreactivity to proapoptotic Bax. Thus, preventive efficacy of GEN in HER-2/neu+/ER- 184-B5/HER cells may be due to its ability to down-regulate HER-2/neu mediated signal transduction, increase the expression of the cyclin dependent kinase inhibitor p16INK4, and induce Bcl-2 dependent apoptosis. These data provide evidence that GEN may be a potential chemopreventive lead compound for human comedo DCIS. The 184-B5/HER cells, may therefore, provide a high throughput mechanistic bioassay to identify new chemopreventive agents for human breast cancer.

Studies of epidermal growth factor receptor inhibition in breast cancer.

Until recently, there has been little knowledge on the growth control of oestrogen receptor (ER)-negative ductal carcinoma in situ (DCIS) and invasive breast cancer. The recent development of DCIS models, such as transgenic mice, cell-line xenograft models and, importantly, in vivo human DCIS xenograft models has facilitated the investigation and understanding of the control of growth of early pre-invasive breast lesions. Recent studies have shown that ER-negative DCIS, unlike ER-positive DCIS, is hormone independent and does not respond to anti-oestrogen treatment. Moreover, DCIS of the comedo type utilises type I tyrosine kinase growth factors, such as epidermal growth factor receptor (EGFR) and c-erbB-2, in receptor signalling for growth. New data underscore the importance of EGFR as the major modulating growth factor receptor in the control of proliferation in the breast. Pre-clinical studies performed on human DCIS xenografts in nude mice suggest a potential role for EGFR tyrosine kinase inhibitors (EGFR-TKIs). More specifically, ZD1839, a novel orally active and selective EGFR-TKI, has been shown to produce a response in DCIS through a decrease in epithelial proliferation. These findings have enhanced our knowledge of signal transduction pathways in cancer and indicate that tyrosine kinase blockade of EGFR has potential for the treatment and chemoprevention of DCIS. It is hoped that further advances in this area and evaluation of EGFR-TKIs in Phase II/III clinical trials will allow their therapeutic potential as anticancer agents to be appreciated.