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Query: UMLS:C0178874 (tumor progression)
 40,807 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tumorigenesis in mice of the rat insulin promoter [RIP]-simian virus 40 tumor antigen [SV40 Tag] transgenic lineages, RIP1-Tag2 and RIP1-Tag4, is a process initiated by expression of SV40 Tag in pancreatic beta cells, evolution of islet cell hyperplasia and insulinoma appearance. Analysis of major histocompatibility complex [MHC] class I gene expression during this process revealed a normal level of MHC class I molecules at the surface of pancreatic islet cells of RIP1-Tag4 mice, while hyperplastic islets from the same mice contained cells expressing a normal level and cells expressing a low level of MHC class I antigen. Insulinomas themselves expressed very low levels or no MHC class I gene product. Thus, down-regulation of MHC class I gene appears to accompany tumor progression of SV40 Tag-transformed beta islet cells. MHC class I antigen expression in a series of clonally derived cell lines of beta cell origin from different SV40 Tag-induced insulinomas ranged from quite low to undetectable, although expression was inducible by interferon-gamma. Nuclear run-on and transient transfection analyses indicated that expression of the MHC class I gene in these cells in controlled at the transcriptional level, and that the decreased expression is paralleled by reduced binding of transcription factors to the R1 element of the H-2 enhancer.
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PMID:Down-regulation of MHC class I antigen in insulinoma cells controlled by the R1 element of the H-2 enhancer. 813 22

Tolerance to tumor cell-expressed molecules and selection of cells that evade immune surveillance during tumor progression create effective barriers to immunotherapy. We investigated the cytotoxic T-lymphocyte response to simian virus 40 (SV40) tumor (T/t) antigen in two lineages of transgenic mice bearing the same rat insulin promoter-SV40 T/t antigen (RIP Tag) hybrid gene. RIP1-Tag2 mice, which express Tag as embryos, are tolerant to Tag, whereas RIP1-Tag4 mice, which express the transgene in pancreatic islet beta cells several weeks after birth and develop insulinomas, can be immunized to generate active Tag-specific cytotoxic T lymphocytes as determined by in vitro assays. Indeed, RIP1-Tag4 mice immunized with Tag by SV40 infection prior to the time of endogenous transgene expression also mount an effective in vivo cellular immune response to the Tag-expressing pancreatic beta cells, and Tag-induced tumor growth is significantly delayed (up to 1 year). However, after the transgene is expressed, RIP1-Tag4 mice are unable to mount a tumor-inhibiting response upon immunization, although Tag-specific cytotoxic T cells can still be demonstrated in vitro. Our data suggest that Tag-specific T cells are rendered unresponsive in vivo in RIP1-Tag4 mice and that the establishment of this unresponsiveness to Tag can be prevented by SV40 immunization only before the onset of the transgene expression. In the older, successfully immunized mouse, decreased immune surveillance and selection of cells with down-regulation of major histocompatibility complex class I expression most likely set the stage for insulinoma development.
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PMID:Timely immunization subverts the development of peripheral nonresponsiveness and suppresses tumor development in simian virus 40 tumor antigen-transgenic mice. 817 Oct 12

Invasion of the uterus by first trimester human placental extravillous trophoblast (EVT) cells depends on mechanisms shared by malignant cells. However, unlike tumor invasion, trophoblast invasion of the uterus is stringently controlled in situ by local molecules such as transforming growth factor (TGF)beta. Since EVT cells possess active invasion-associated genes but are nontumorigenic, our objective was to induce premalignant and then malignant phenotype into a normal EVT cell line in order to identify the molecular basis of tumor progression. Simian virus 40 large T antigen (SV40 Tag) was introduced into a normal human first trimester invasive EVT cell line, HTR8, established in our laboratory. Since the HTR8 line has a limited in vitro lifespan of 12-15 passages, SV40 Tag-transformed cells were selected on the basis of extended lifespan. A long-lived line, RSVT-2, was produced and an immortalized subclone, RSVT2/C, was further derived under a forced crisis regimen. We examined transformation-induced alterations in proliferative and invasive abilities, responses to the invasion and proliferation-regulating growth factor TGFbeta and changes in gene expression for invasion-associated enzymes or enzyme inhibitors. RSVT-2 and RSVT2/C cell lines were hyperproliferative and hyperinvasive when compared with the parental HTR8 cell line. They were also variably resistant to the anti-proliferative and anti-invasive signals from TGFbeta. Since both cell lines remained non-tumorigenic in nude mice, these properties indicate that they attained a premalignant phenotype. Both cell lines showed reduced expression of tissue inhibitor of metalloproteases (TIMP)-1, while TIMP-2 and plasminogen activator inhibitor (PAI)-I expression was was also reduced in RSVT2/C cells, thus contributing to their hyperinvasiveness. Their resistance to the anti-invasive action of TGFbeta was explained by the failure of TGFbeta to upregulate TIMPs and PAI-I, in contrast to the TGFbeta-induced upregulation noted in parental HTR8 cells.
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PMID:SV40 Tag transformation of the normal invasive trophoblast results in a premalignant phenotype. I. Mechanisms responsible for hyperinvasiveness and resistance to anti-invasive action of TGFbeta. 966 7

Poor gap junctional intercellular communication (GJIC) has been associated with uncontrolled cell growth and neoplasia. We have successfully propagated normal first trimester invasive extravillous trophoblast (EVT) cells, and have produced premalignant EVT lines after SV40 Tag transformation: RSVT-2 is an uncloned line that is long-lived; RSVT2/C is a clonal line that is immortal. Both are hyperproliferative, hyperinvasive and variably refractory to the anti-proliferative and anti-invasive effects of transforming growth factor beta (TGFbeta). Possible changes in gap junctions during the transition of normal invasive EVT cells to the premalignant stage were examined by comparing expression of connexin proteins (by immunolabeling for Cx26, Cx32, Cx40, Cx43), and mRNA (by Northern blot with cDNA probes for Cx26, Cx32, Cx43), and functional GJIC (by dye transfer using the preloading method) in normal parental EVT cells and their SV40 Tag transformants. Results from immunofluorescence and Northern blot analysis revealed that, of the panel of connexins examined, only Cx43 was variably expressed in these cell lines in vitro. Expression of Cx43 protein and mRNA was abundant in normal EVT cell line HTR8, reduced in long-lived RSVT-2 cells and undetectable in immortalized RSVT2/C cells. GJIC, as measured by dye transfer between donor and recipient cells, was also similarly reduced in recipient RSVT-2 cells, and drastically reduced in RSVT2/C cells, irrespective of whether the dye donor was of the same cell type (homocellular coupling) or HTR8 cells (heterocellular coupling). Treatment with TGFbeta reduced Cx43 mRNA expression as well as GJIC in normal EVT cells, but not in the SV40 Tag transformants. Our findings suggest that downregulation of connexins with the resultant impairment in GJIC is an early event in tumor progression, as observed in the premalignant SV40 Tag transformants.
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PMID:SV40 Tag transformation of the normal invasive trophoblast results in a premalignant phenotype. II. Changes in gap junctional intercellular communication. 966 8

We have previously documented that transgenic mice expressing SV40 Tag regulated by the rat prostatic steroid-binding protein C3(1) 5'-flanking region display multistage mammary tumorigenesis. To delineate genetic changes associated with mammary tumor progression, comparative genomic hybridization (CGH) was performed. CGH revealed a consistent gain of the telomeric region of chromosome 6. This region contains the Ki-ras proto-oncogene. Analyses of genomic DNA by Southern blot demonstrated up to 40-fold amplification of the Ki-ras gene. Ki-ras amplification was detected in 12, 46 and 68% of tumors from 4, 5 and 6 month old mice, respectively, whereas no amplifications were found in any preneoplastic mammary tissues. Tumors bearing Ki-ras gene amplification exhibited high levels of Ki-ras RNA and protein. The over-expressed Ki-Ras protein in these tumors appeared functionally active as indicated by the elevated MAP kinase activity. These data demonstrate that while Ki-ras amplification might not be an early event, there is a strong association between Ki-ras amplification and over-expression and mammary tumor progression in this model. This study also shows that CGH is a powerful and useful technique for identifying chromosomal copy number changes during tumor progression, and that this model may provide a predictable in vivo system for studying gene amplification.
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PMID:Amplification of Ki-ras and elevation of MAP kinase activity during mammary tumor progression in C3(1)/SV40 Tag transgenic mice. 981 72

We have previously demonstrated that amplification and overexpression of the Ki-ras gene is associated with mammary tumor progression in C3(1)/SV40Tag transgenic mice (Liu et al., 1998). To further evaluate the functional significance of the Ki-ras proto-oncogene in mammary cancer development, in vivo studies were conducted to examine the effect of Ki-ras gene dosage on tumor progression. The lack of one normal Ki-ras allele C3(1)/SV40Tag transgenic mice resulted in significantly delayed mammary intraepithelial neoplasia (MIN) formation as well as in a decreased number of mammary gland carcinomas. However, despite the retardation of tumor development by reduced Ki-ras gene dosage, overall survival was only modestly affected. This appears to be due to several factors including significant mammary tumor growth associated with Ki-ras gene amplification and over-expression that occurs during the advanced stage of oncogenesis in mice carrying either one or two normal Ki-ras alleles. The retardation of tumor progression due to the haploid loss of Ki-ras did not appear to be related to accelerated apoptosis, or a reduced rate of cell proliferation at the tumor stages examined. These data strongly suggest that the gene dosage of Ki-ras affects tumor promotion at an early stage of mammary tumor progression in this SV40 Tag-induced model of mammary oncogenesis.
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PMID:Haploid loss of Ki-ras delays mammary tumor progression in C3 (1)/SV40 Tag transgenic mice. 1136 Jan 88

Existing prostate cancer cell lines have been derived from late stages of human prostate cancer. In this paper, we present two cell lines generated from prostatic intraepithelial neoplasia (PIN), the precursor lesion for prostate adenocarcinoma. Pr-111 and Pr-117 were established from PIN lesions that developed in the C3(1)/Tag transgenic model of prostate cancer. Pr-111 and Pr-117 cells express simian virus 40 large T antigen (SV40 Tag) and are immortalized in culture, distinguishing them from normal prostate cells. The growth rates of these two cell lines are quite different; with Pr-111 cells growing much more slowly (doubling time approximately 40 hours) compared to Pr-117 cells (doubling time approximately 22 hours), and also show significantly different growth rates in different media. Both prostate cell lines express cytokeratin and androgen receptor (AR) with Pr-111 cells demonstrating androgen-dependent growth and Pr-117 cells exhibiting androgen-responsive growth characteristics. Athymic nude mice injected with Pr-111 cells either do not develop tumors or develop tumors after a long latency period of 14 weeks. Pr-117 cells, however, develop tumors by 3 to 6 weeks, suggesting that Pr-117 cells represent a later stage of tumor progression. These two novel cell lines will be useful for studying early stages of prostate tumor development and androgen responsiveness.
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PMID:Development of PIN and prostate adenocarcinoma cell lines: a model system for multistage tumor progression. 1189 66

Cancer therapies based on the inhibition of angiogenesis by endostatin have recently been developed. We demonstrate that a mutated form of human endostatin (P125A) can inhibit the angiogenic switch in the C3(1)/Tag mammary cancer model. P125A has a stronger growth-inhibitory effect on endothelial cell proliferation than wild-type endostatin. We characterize the angiogenic switch, which occurs during the transition from preinvasive lesions to invasive carcinoma in this model, and which is accompanied by a significant increase in total protein levels of vascular endothelial growth factor (VEGF) and an invasion of blood vessels. Expression of the VEGF(188) mRNA isoform, however, is suppressed in invasive carcinomas. The VEGF receptors fetal liver kinase-1 (Flk-1) and Fms-like tyrosine kinase-1 (Flt-1) become highly expressed in epithelial tumor and endothelial cells in the mammary carcinomas, suggesting a potential autocrine effect for VEGF on tumor cell growth. Angiopoietin-2 mRNA levels are also increased during tumor progression. CD-31 (platelet-endothelial cell adhesion molecule [PECAM]) staining revealed that blood vessels developed in tumors larger than 1 mm The administration of P125A human endostatin in C3(1)/Tag females resulted in a significant delay in tumor onset, decreased tumor multiplicity and tumor burden and prolonged survival of the animals. Endostatin treatment did not reduce the number of preinvasive lesions, proliferation rates or apoptotic index, compared with controls. However, mRNA levels of a variety of proangiogenic factors (VEGF, VEGF receptors Flk-1 and Flt-1, angiopoietin-2, Tie-1, cadherin-5 and PECAM) were significantly decreased in the endostatin-treated group compared with controls. These results demonstrate that P125A endostatin inhibits the angiogenic switch during mammary gland adenocarcinoma tumor progression in the C3(1)/Tag transgenic model.
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PMID:Inhibition of the mammary carcinoma angiogenic switch in C3(1)/SV40 transgenic mice by a mutated form of human endostatin. 1220 72

To identify molecular changes that occur during prostate tumor progression, we have characterized a series of prostate cancer cell lines isolated at different stages of tumorigenesis from C3(1)/Tag transgenic mice. Cell lines derived from low- and high-grade prostatic intraepithelial neoplasia, invasive carcinoma, and a lung metastasis exhibited significant differences in cell growth, tumorigenicity, invasiveness, and angiogenesis. cDNA microarray analysis of 8700 features revealed correlations between the tumorigenicity of the C3(1)/Tag-Pr cells and changes in the expression levels of genes regulating cell growth, angiogenesis, and invasion. Many changes observed in transcriptional regulation in this in vitro system are similar to those reported for human prostate cancer, as well as other types of human tumors. This analysis of expression patterns has also identified novel genes that may be involved in mechanisms of prostate oncogenesis or serve as potential biomarkers or therapeutic targets for prostate cancer. Examples include the L1-cell adhesion molecule, metastasis-associated gene (MTA-2), Rab-25, tumor-associated signal transducer-2 (Trop-2), and Selenoprotein-P, a gene that binds selenium and prevents oxidative stress. Many genes identified in the Pr-cell line model have been shown to be altered in human prostate cancer. The comprehensive microarray data provides a rational basis for using this model system for studies where alterations of specific genes or pathways are of particular interest. Quantitative real-time reverse transcription-PCR for Selenoprotein-P demonstrated a similar down-regulation of the transcript of this gene in a subset of human prostate tumors, mouse tumors, and prostate carcinoma cell lines. This work demonstrates that expression profiling in animal models may lead to the identification of novel genes involved in human prostate cancer biology.
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PMID:Alterations in gene expression profiles during prostate cancer progression: functional correlations to tumorigenicity and down-regulation of selenoprotein-P in mouse and human tumors. 1223 3

The Eph family of receptor tyrosine kinases and their ligands, known as ephrins, play a crucial role in vascular development during embryogenesis. The function of these molecules in adult angiogenesis has not been well characterized. Here, we report that blocking Eph A class receptor activation inhibits angiogenesis in two independent tumor types, the RIP-Tag transgenic model of angiogenesis-dependent pancreatic islet cell carcinoma and the 4T1 model of metastatic mammary adenocarcinoma. Ephrin-A1 ligand was expressed in both tumor and endothelial cells, and EphA2 receptor was localized primarily in tumor-associated vascular endothelial cells. Soluble EphA2-Fc or EphA3-Fc receptors inhibited tumor angiogenesis in cutaneous window assays, and tumor growth in vivo. EphA2-Fc or EphA3-Fc treatment resulted in decreased tumor vascular density, tumor volume, and cell proliferation, but increased cell apoptosis. However, EphA2-Fc had no direct effect on tumor cell growth or apoptosis in culture, yet inhibited migration of endothelial cells in response to tumor cells, suggesting that the soluble receptor inhibited blood vessel recruitment by the tumor. These data provide the first functional evidence for Eph A class receptor regulation of pathogenic angiogenesis induced by tumors and support the function of A class Eph receptors in tumor progression.
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PMID:Soluble Eph A receptors inhibit tumor angiogenesis and progression in vivo. 1237 Aug 23


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