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Robert D Cardiff

Publications and source records attributed to Robert D Cardiff.

At least 55 records · Page 3Linked to original sources
PubMed2004

Molecular analysis of metastasis in a polyomavirus middle T mouse model: the role of osteopontin.

INTRODUCTION: In order to study metastatic disease, we employed the use of two related polyomavirus middle T transgenic mouse tumor transplant models of mammary carcinoma (termed Met and Db) that display significant differences in metastatic potential. METHODS: Through suppression subtractive hybridization coupled to the microarray, we found osteopontin (OPN) to be a highly expressed gene in the tumors of the metastatic mouse model, and a lowly expressed gene in the tumors of the lowly metastatic mouse model. We further analyzed the role of OPN in this model by examining sense and antisense constructs using in vitro and in vivo methods. RESULTS: With in vivo metastasis assays, the antisense Met cells showed no metastatic tumor formation to the lungs of recipient mice, while wild-type Met cells, with higher levels of OPN, showed significant amounts of metastasis. The Db cells showed a significantly reduced metastasis rate in the in vivo metastasis assay as compared with the Met cells. Db cells with enforced overexpression of OPN showed elevated levels of OPN but did not demonstrate an increase in the rate of metastasis compared with the wild-type Db cells. CONCLUSIONS: We conclude that OPN is an essential regulator of the metastatic phenotype seen in polyomavirus middle T-induced mammary tumors. Yet OPN expression alone is not sufficient to cause metastasis. These data suggest a link between metastasis and phosphatidylinositol-3-kinase-mediated transcriptional upregulation of OPN, but additional phosphatidylinositol-3-kinase-regulated genes may be essential in precipitating the metastasis phenotype in the polyomavirus middle T model.

Animals↗
PubMed2004

pRb inactivation in mammary cells reveals common mechanisms for tumor initiation and progression in divergent epithelia.

Retinoblastoma 1 (pRb) and the related pocket proteins, retinoblastoma-like 1 (p107) and retinoblastoma-like 2 (p130) (pRb(f), collectively), play a pivotal role in regulating eukaryotic cell cycle progression, apoptosis, and terminal differentiation. While aberrations in the pRb-signaling pathway are common in human cancers, the consequence of pRb(f) loss in the mammary gland has not been directly assayed in vivo. We reported previously that inactivating these critical cell cycle regulators in divergent cell types, either brain epithelium or astrocytes, abrogates the cell cycle restriction point, leading to increased cell proliferation and apoptosis, and predisposing to cancer. Here we report that mouse mammary epithelium is similar in its requirements for pRb(f) function; Rb(f) inactivation by T(121), a fragment of SV40 T antigen that binds to and inactivates pRb(f) proteins, increases proliferation and apoptosis. Mammary adenocarcinomas form within 16 mo. Most apoptosis is regulated by p53, which has no impact on proliferation, and heterozygosity for a p53 null allele significantly shortens tumor latency. Most tumors in p53 heterozygous mice undergo loss of the wild-type p53 allele. We show that the mechanism of p53 loss of heterozygosity is not simply the consequence of Chromosome 11 aneuploidy and further that chromosomal instability subsequent to p53 loss is minimal. The mechanisms for pRb and p53 tumor suppression in the epithelia of two distinct tissues, mammary gland and brain, are indistinguishable. Further, this study has produced a highly penetrant breast cancer model based on aberrations commonly observed in the human disease.

Brain Neoplasms↗
PubMed2004

Angiogenic acceleration of Neu induced mammary tumor progression and metastasis.

The Neu (ErbB2, HER2) member of the epidermal growth factor receptor family is implicated in many human breast cancers. We have tested the importance of increased angiogenic signaling in the NeuYD [mouse mammary tumor virus (MMTV)-Neu(ndl)-YD5] mammary tumor model. Transgenic mice expressing vascular endothelial growth factor (VEGF)(164) from the MMTV promoter were generated. These mice expressed VEGF(164) RNA and protein at 20- to 40-fold higher levels throughout mammary gland development but exhibited normal mammary gland development and function. However, in combination with the NeuYD oncogene, VEGF(164) expression resulted in increased vascularization of hyperplastic mammary epithelium and dramatic acceleration of tumor appearance from 111 to 51 days. Gene expression profiling also indicated that the VEGF-accelerated tumors were substantially more vascularized and less hypoxic. The preferential vascularization of early hyperplastic portions of mammary epithelia in NeuYD;MMTV-VEGF animals was associated with NeuYD RNA expression, disorganization of the tight junctions, and overlapping transgenic VEGF expression. NeuYD;MMTV-VEGF(164) bigenic, tumor-bearing animals resulted in an average of 10 tumor cell colonies/lung lodged within vascular spaces. No similar lung colonies were found in control NeuYD mice with similar tumor burdens. Overall, these results demonstrate the angiogenic restriction of early hyperplastic mammary lesions. They also reinforce in vivo the importance of activated Neu in causing disorganization of mammary luminal epithelial cell junctions and provide support for an invasion-independent mechanism of metastasis.

Animals↗
PubMed2004

Polyomavirus middle T-induced mammary intraepithelial neoplasia outgrowths: single origin, divergent evolution, and multiple outcomes.

The development of models to investigate the pathobiology of premalignant breast lesions is a critical prerequisite for development of breast cancer prevention and early intervention strategies. Using tissue transplantation techniques, we modified the widely used polyomavirus middle T (PyV-mT) transgenic mouse model of breast cancer to study the premalignant stages of tumorigenesis. Premalignant atypical lesions were isolated from PyV-mT transgenic mice and used to generate two sets of three mammary intraepithelial neoplasia (MIN) outgrowth lines. Investigation of these six unique lines, each of which fulfills the criteria for MIN, has provided new information regarding the biology of PyV-mT-induced neoplasia. Although expression of the PyV-mT transgene was the primary initiating event for all lines, they exhibited different tumor latencies, metastatic potentials, and morphologies. Six distinguishable morphologic patterns of differentiation were identified within the premalignant outgrowths that are likely to represent several tumorigenic pathways. Further, several tumor phenotypes developed from each line and the tumors developing from the six lines had different metastatic potentials. These observations are consistent with the hypothesis that distinct pathways of PyV-mT-initiated neoplastic progression lead to different outcomes with respect to latency and metastasis. The MIN outgrowth lines share several characteristics with precursors of human breast cancer including the observation that gene expression profiles of tumors are more similar to those of the MIN outgrowth line outgrowth from which they developed than to other tumors. These lines provide an opportunity to study the full range of events occurring secondary to PyV-mT expression in the mammary gland.

Animals↗
PubMed2004

Molecular characterization of the transition to malignancy in a genetically engineered mouse-based model of ductal carcinoma in situ.

A transplantable model of human ductal carcinoma in situ that progresses to invasive carcinoma was developed from a genetically engineered mouse (GEM). Additional lines were established using early mammary premalignant lesions from transgenic MMTV-PyV-mT mice. These lines were verified to be premalignant and transplanted repeatedly to establish stable and predictable properties. Here, we report the first in-depth molecular analysis of neoplastic progression occurring in one premalignant transplantable GEM-derived line. Oligonucleotide microarrays showed that many genes are differentially expressed between the quiescent and prelactating mammary gland and the premalignant GEM outgrowth. In contrast, a small but consistent group of genes was associated with the transformation from premalignancy to tumor. This suggests that the majority of gene expression changes occur during the premalignant transition from normal to premalignancy, whereas many fewer changes occur during the malignant transition from premalignancy to invasive carcinoma. The premalignant transition is associated with several cell cycle-related genes and the up-regulation of oncogenes is associated with various cancers (Ccnd11, Cdk4, Myb, and Ect2). The changes identified in the malignant transition included genes previously associated with human breast cancer progression. Misregulation of the insulin-like growth factor and transforming growth factor-beta signaling pathways and the stromal-epithelial interaction were implicated. Our results suggest that this transplantable GEM-based model recapitulates human ductal carcinoma in situ at both histologic and molecular levels. With consistent tumor latency and molecular profiles, this model provides an experimental platform that can be used to assess functional genomics and molecular pharmacology and to test promising chemoprevention strategies.

Animals↗
PubMed2004

Mice expressing SV40 T antigen directed by the intestinal trefoil factor promoter develop tumors resembling human small cell carcinoma of the colon.

The colonic epithelium contains three major types of mature cells, namely, absorptive, goblet, and enteroendocrine cells. These cells are maintained by a complex process of cell renewal involving progenitor and stem cells, and colon cancers develop when this process goes awry. Much is known about the genetic and epigenetic changes that occur in cancer; however, little is known as to the specific cell types involved in carcinogenesis. In this study, we expressed the SV40 Tag oncogene in the intestinal epithelium under the control of an intestinal trefoil factor (ITF) promoter. This caused tumor formation in the proximal colon with remarkable efficiency. ITFTag tumors were rapidly growing, multifocal, and invasive. ITFTag tumor cells express synaptophysin and contain dense core secretory granules, markers of neuroendocrine differentiation. The cell type involved in the early steps of ITFTag tumorigenesis was studied by examining partially transformed crypts that contained populations of both normal and dysplastic cells. The dysplastic cell population always expressed both Tag and synaptophysin. Cells expressing Tag alone were never observed; however, normal enteroendocrine cells expressing synaptophysin but not Tag were readily visualized. This suggests that ITFTag tumor cells originate from the enteroendocrine cell lineage following a transforming event that results in Tag expression. ITFTag tumors closely resemble human small cell carcinomas of the colon, suggesting the possibility that these tumors might be derived from the enteroendocrine cell lineage as well.

Animals↗
PubMed2003

Epidermal growth factor receptor-dependent activation of Gab1 is involved in ErbB-2-mediated mammary tumor progression.

Activation of the epidermal growth factor receptor (EGFR) family is thought to play an important role in mammary tumorigenesis and metastasis. The potent transforming activity of the EGFR family is due to their ability to heterodimerize with each other in response to a number of mitogenic ligands. The formation of EGFR and ErbB-2 heterodimers has been recently implicated as an important factor in the induction of sporadic human breast cancers. To directly assess whether the catalytic activity of EGFR is required for ErbB-2 induction of mammary tumors, we have interbred transgenic mice expressing ErbB-2 oncogene under the transcriptional control of the mouse mammary tumor virus (MMTV) promoter/enhancer to a naturally occurring mouse mutant carrying a catalytically impaired EGFR (waved-2 mice). Although the female transgenic mice possessing mutant EGFR developed mammary tumors, the tumors occurred only after a delayed latency period, and were fewer in number. The impaired tumor phenotype was further correlated with debilitated phosphorylation of the Gab1 multisubstrate adapter. These observations provide evidence that efficient ErbB-2-induced mammary tumor progression requires EGFR-dependent activation of Gab1.

Adaptor Proteins, Signal Transducing↗
PubMed2003

E mu-BRD2 transgenic mice develop B-cell lymphoma and leukemia.

Transgenic mice with lymphoid-restricted overexpression of the double bromodomain protein bromodomain-containing 2 (Brd2) develop splenic B-cell lymphoma and, upon transplantation, B-cell leukemia with leukemic infiltrates in liver and lung. Brd2 is a nuclear-localized transcription factor kinase that is most closely related to TATA box binding protein-associated factor, 250 kDa (TAF(II)250) and the Drosophila developmental protein female sterile homeotic. Constitutive expression of BRD2 in the lymphoid compartment increases cyclin A transcription, "priming" transgenic B cells for proliferation. Mice stochastically develop an aggressive B-cell lymphoma with the features of B-1 cells, including CD5 and surface IgM expression. The B-cell lymphoma is monoclonal for immunoglobulin gene rearrangement and is phenotypically stable. The lymphoblasts are very large and express a transcriptome that is similar to human non-Hodgkin lymphomas. Both a wild-type BRD2 transgene and a kinase-null point mutant drive lymphomagenesis; therefore we propose that, rather than kinase activity, Brd2-mediated recruitment of E2 promoter binding factors (E2Fs) and a specific histone acetyltransferase to the cyclin A promoter by both types of transgene is a mechanistic basis for neoplasia. This report is the first to describe a transgenic mouse model for constitutive expression of a protein with more than one bromodomain.

Animals↗
PubMed2003

Gene expression profiling of neu-induced mammary tumors from transgenic mice reveals genetic and morphological similarities to ErbB2-expressing human breast cancers.

Numerous studies have shown that the overexpression and amplification of ErbB2/Neu are observed in 20-30% of patients afflicted with breast cancer. Furthermore, it has also been observed that the elevated expression of ErbB2/Neu also correlates with poor prognosis and clinical outcome. Given the prevalence of this disease, we sought to create mouse models that mimic the human condition. In this study, we compared two mouse models expressing activated neu under the control of the endogenous and mouse mammary tumor virus promoters. Although histologically similar, the latency and metastatic potential of these tumors are remarkably different. Gene expression profiling of tumor RNA from the two Neu mouse models revealed distinctive and nonoverlapping patterns of gene expression. Consistent with noninvasive nature of the mammary tumors induced by expression of neu under the endogenous promoter, these tumors expressed a number of markers characteristic of a highly differentiated state. In addition to these differences, these analyses revealed that in contrast to the mouse mammary tumor virus-based Neu model, the endogenous promoter tumors expressed elevated levels of two genes (Grb7 and Cab1) that are closely linked to ErbB2 and often coamplified in noninvasive ductal carcinoma in situ. Furthermore, this analysis has revealed several transcription factors that may be involved in ErbB2-mediated tumorigenesis. Taken together, these results illustrate the similarity of the endogenously regulated Neu tumor model to the human disease.

Animals↗
PubMed2003

Mammary tumor latency is increased in mice lacking the inducible nitric oxide synthase.

Nitric oxide (NO) and its metabolites are implicated in carcinogenesis and metastasis. Both stimulatory and inhibitory effects of NO have been reported in relation to breast cancer and its role in the development of malignancies and metastasis remains uncertain. We have used the polyomavirus middle T antigen (PyV-mT) targeted to the mouse mammary gland and bred into an inducible NO synthase (iNOS)-deficient C57Bl/6 strain to examine a role for nitric oxide in modulating tumors that develop in the complex environment of the whole animal. The development of hyperplasias was delayed to the extent that the earliest palpable tumors arose 2-4 weeks later in PyV-mT/iNOS(-/-) mice compared with PyV-mT/iNOS(+/+) mice, identifying a role for iNOS in early events in mammary tumor formation. Tumors that did develop in PyV-mT/iNOS(-/-) mice were characteristically well differentiated and had a cribriform pattern. Other tumors were myoepithelial adenocarcinomas with uniform nuclear size. In contrast, mice capable of iNOS activity typically developed solid nodular adenocarcinomas with a high mitotic index and pleomorphic nuclei. No significant effect of iNOS deficiency was found on vascular density in hyperplasias or tumors by examining CD31-positive vessels. The infiltration of lesions by macrophages, cells capable of significant NO production, remained unchanged in PyV-mT/iNOS(-/-) mice. Metastatic potential was retained by PyV-mT-transformed epithelium in the absence of iNOS, indicating that NO production by iNOS is not essential for this process. These results indicate a role for iNOS in tumorigenesis, particularly in the regulation of early events.

Adenocarcinoma↗
PubMed2003

Nkx3.1; Pten mutant mice develop invasive prostate adenocarcinoma and lymph node metastases.

Recent studies have shown that several loss-of-function mouse models of prostate carcinogenesis can develop a spectrum of precancerous lesions that resemble human prostatic intraepithelial neoplasia (PIN). Here, we have investigated the malignant potential of the high-grade PIN lesions that form in Nkx3.1(+/-); Pten(+/-) compound mutant mice and demonstrate their neoplastic progression in a serial transplantation/tissue recombination assay. Furthermore, we find that a majority of Nkx3.1(+/-); Pten(+/-) mice greater than 1 year of age develop invasive adenocarcinoma, which is frequently accompanied by metastases to lymph nodes. Finally, we observe androgen independence of high-grade PIN lesions after androgen ablation of Nkx3.1(+/-); Pten(+/-) mice. We conclude that Nkx3.1(+/-); Pten(+/-) mice recapitulate key features of advanced prostate cancer and represent a useful model for investigating associated molecular mechanisms and for evaluating therapeutic approaches.

Adenocarcinoma↗
PubMed2003

Activation of beta-catenin in prostate epithelium induces hyperplasias and squamous transdifferentiation.

The Wnt/beta-catenin signaling pathway is critical for normal mammalian development, the specification of epidermal cells and neoplastic transformation of intestinal epithelium. However, precise molecular information regarding cell-specific responses to beta-catenin signaling has been limited. This question was addressed using a mouse model in which exon 3 of the beta-catenin gene was deleted in several cell types with loxP-mediated recombination utilizing a Cre transgene under control of the mouse mammary tumor virus-long terminal repeat (MMTV-LTR). The stabilization of beta-catenin in prostate epithelium resulted in hyperplasias and extensive transdifferentiation into epidermal-like structures, which expressed keratins 1 and 6, filaggrin, loricrin and involucrin. The cell-specific loss of NKCC1 protein and reduced nuclear Stat5a is further suggestive of a loss of prostate epithelial characteristics. In addition to the prostate, hyperplasias and squamous metaplasias were detected in epithelia of the epididymis, vas deferens, coagulating gland, preputial gland and salivary gland. However, and in contrast to a recent study, no lesions reminiscent of high-grade prostate intraepithelial neoplasia were detected. Since beta-catenin was activated in several cell types and impinged upon the viability of these mice, it was not possible to evaluate the cumulative effect over more than 3 months. To assess long-term consequences of beta-catenin activation, mutant and control prostate tissues were transplanted into the mammary fat pads of wild-type males. Notably, squamous metaplasias, intra-acinous hyperplasia and possible neoplastic transformation were observed after a total of 18 weeks of beta-catenin stimulation. This suggests that the transdifferentiation into squamous metaplasias is an early response of endoderm-derived cells to beta-catenin, and that the development of intra-acinous hyperplasias or neoplastic foci is a later event.

Adipose Tissue↗
PubMed2003

Transforming growth factor beta signaling impairs Neu-induced mammary tumorigenesis while promoting pulmonary metastasis.

The influence of transforming growth factor beta (TGF-beta) signaling on Neu-induced mammary tumorigenesis and metastasis was examined with transgenic mouse models. We generated mice expressing an activated TGF-beta type I receptor or dominant negative TGF-beta type II receptor under control of the mouse mammary tumor virus promoter. When crossed with mice expressing activated forms of the Neu receptor tyrosine kinase that selectively couple to the Grb2 or Shc signaling pathways the activated type I receptor increased the latency of mammary tumor formation but also enhanced the frequency of extravascular lung metastasis. Conversely, expression of the dominant negative type II receptor decreased the latency of Neu-induced mammary tumor formation while significantly reducing the incidence of extravascular lung metastases. These observations argue that TGF-beta can promote the formation of lung metastases while impairing Neu-induced tumor growth and suggest that extravasation of breast cancer cells from pulmonary vessels is a point of action of TGF-beta in the metastatic process.

Activin Receptors, Type I↗
PubMed2003

Impact of p53 loss on reversal and recurrence of conditional Wnt-induced tumorigenesis.

Aberrant activation of Wnt signaling is oncogenic and has been implicated in a variety of human cancers. We have developed a doxycycline-inducible Wnt1 transgenic mouse model to determine the dependence of established mammary adenocarcinomas on continued Wnt signaling. Using this model we show that targeted down-regulation of the Wnt pathway results in the rapid disappearance of essentially all Wnt-initiated invasive primary tumors as well as pulmonary metastases. Tumor regression does not require p53 and occurs even in highly aneuploid tumors. However, despite the dependence of primary mammary tumors and metastases on continued Wnt signaling and the dispensability of p53 for tumor regression, we find that a substantial fraction of tumors progress to a Wnt-independent state and that p53 suppresses this process. Specifically, loss of one p53 allele dramatically facilitates the progression of mammary tumors to a Wnt1-independent state both by impairing the regression of primary tumors following doxycycline withdrawal and by promoting the recurrence of fully regressed tumors in the absence of doxycycline. Thus, although p53 itself is dispensable for tumor regression, it nevertheless plays a critical role in the suppression of tumor recurrence. Our findings demonstrate that although even advanced stages of epithelial malignancy remain dependent upon continued Wnt signaling for maintenance and growth, loss of p53 facilitates tumor escape and the acquisition of oncogene independence.

Adenocarcinoma↗
PubMed2003

Id-1 is not expressed in the luminal epithelial cells of mammary glands.

BACKGROUND: The family of inhibitor of differentiation/DNA binding (Id) proteins is known to regulate development in several tissues. One member of this gene family, Id-1, has been implicated in mammary development and carcinogenesis. Mammary glands contain various cell types, among which the luminal epithelial cells are primarily targeted for proliferation, differentiation and carcinogenesis. Therefore, to assess the precise significance of Id-1 in mammary biology and carcinogenesis, we examined its cellular localization in vivo using immunohistochemistry. METHODS: Extracts of whole mammary glands from wild type and Id-1 null mutant mice, and tissue sections from paraffin-embedded mouse mammary glands from various developmental stages and normal human breast were subjected to immunoblot and immunohistochemical analyses, respectively. In both these procedures, an anti-Id-1 rabbit polyclonal antibody was used for detection of Id-1. RESULTS: In immunoblot analyses, using whole mammary gland extracts, Id-1 was detected. In immunohistochemical analyses, however, Id-1 was not detected in the luminal epithelial cells of mammary glands during any stage of development, but it was detected in vascular endothelial cells. CONCLUSION: Id-1 is not expressed in the luminal epithelial cells of mammary glands.

Animals↗
PubMed2003

PTEN tumor suppressor regulates p53 protein levels and activity through phosphatase-dependent and -independent mechanisms.

We show in this study that PTEN regulates p53 protein levels and transcriptional activity through both phosphatase-dependent and -independent mechanisms. The onset of tumor development in p53(+/-);Pten(+/-) mice is similar to p53(-/-) animals, and p53 protein levels are dramatically reduced in Pten(-/-) cells and tissues. Reintroducing wild-type or phosphatase-dead PTEN mutants leads to a significant increase in p53 stability. PTEN also physically associates with endogenous p53. Finally, PTEN regulates the transcriptional activity of p53 by modulating its DNA binding activity. This study provides a novel mechanism by which the loss of PTEN can functionally control "two" hits in the course of tumor development by concurrently modulating p53 activity.

Animals↗