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Query: UMLS:C0598934 (tumor growth)
 58,965 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The tumor growth suppressor p21 has been shown to be induced by wild-type p53 (wt-p53) and to be a potent inhibitor of cyclin-dependent kinases and PCNA/DNA polymerase delta. Although wt-p53 is reported to be phosphorylated by several protein kinases, the function and significance of the phosphorylation of wt-p53 are not yet fully understood. Using OK-1035, a selective inhibitor of DNA-dependent protein kinase (DNA-PK), we demonstrated the importance of the phosphorylation of wt-p53 by DNA-PK in the DNA damage-mediated expression of the p21 gene. Treatment of HCT116, a human colon carcinoma cell line, with adriamycin induced the expression of wt-p53 and p21. By addition of OK-1035 to this culture, the induction of p21 protein was significantly decreased in a dose-dependent manner, whereas wt-p53 induction was not affected. Northern blot analysis revealed that suppression of p21 protein expression by OK-1035 resulted from reduction in the level of p21 mRNA. OK-1035 did not directly affect the binding ability of wt-p53 to its consensus DNA sequence. Our observations support the idea that wt-p53 induces the transcriptional activation of the p21 gene only after it is phosphorylated by DNA-PK.
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PMID:DNA-dependent protein kinase inhibitor (OK-1035) suppresses p21 expression in HCT116 cells containing wild-type p53 induced by adriamycin. 861 35

Prostaglandin A2 (PGA2) potently inhibits cell proliferation and suppresses tumor growth in vivo, but little is known regarding the molecular mechanisms mediating these effects. Here we demonstrate that treatment of breast carcinoma MCF-7 cells with PGA2 leads to G1 arrest associated with a dramatic decrease in the levels of cyclin D1 and cyclin-dependent kinase 4 (cdk4) and accompanied by an increase in the expression of p21. We further show that these effects occur independent of cellular p53 status. The decline in cyclin D and cdk4 protein levels is correlated with loss in cdk4 kinase activity, cdk2 activity is also significantly inhibited in PGA2-treated cells, an effect closely associated with the upregulation of p21. Immunoprecipitation experiments verified that p21 was indeed complexed with cdk2 in PGA2-treated cells. Additional experiments with synchronized MCF-7 cultures stimulated with serum revealed that treatment with PGA2 prevents the progression of cells from G1 to S. Accordingly, the kinase activity associated with cdk4, cyclin E, and cdk2 immunocomplexes, which normally increases following serum addition, was unchanged in PGA2-treated cells. Furthermore, the retinoblastoma protein (Rb), a substrate of cdk4 and cdk2 whose phosphorylation is necessary for cell cycle progression, remains underphosphorylated in PGA2-treated serum-stimulated cells. These findings indicate that PGA2 exerts its growth-inhibitory effects through modulation of the expression and/or activity of several key G1 regulatory proteins. Our results highlight the chemotherapeutic potential of PGA2, particularly for suppressing growth of tumors lacking p53 function.
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PMID:Inhibition of G1 cyclin-dependent kinase activity during growth arrest of human breast carcinoma cells by prostaglandin A2. 862 77

The clinical course of prostate cancer is highly variable and cannot satisfactorily be predicted by histological criteria alone. To study the prognostic significance of Bcl-2 and p53 overexpression in prostate cancer, 137 consecutive radical prostatectomy specimens were examined by immunohistochemistry. Both Bcl-2 and p53 were associated with malignant phenotype. Bcl-2 expression was more frequent in pT3 tumors (31% positive) than in pT2 tumors (5% positive, P = 0.001). p53 overexpression (found in 8%) was associated with high Gleason score (P = 0.03) and increased tumor growth fraction (Ki67 labeling index (LI); P = 0.017). Survival analysis showed that Bcl-2 expression (P = 0.03), high Ki67 LI (P = 0.018), high grade (P = 0.0037), advanced local stage (P = 0.0005), and positive lymph nodes (P = 0.026) were predictors of progression. The combined analysis of Ki67 LI and Bcl-2 allowed the distinction of three groups with different clinical outcome. Prognosis was best in Bcl-2-negative tumors with low Ki67 LI, worst in Bcl-2-positive tumors with high Ki67 LI, and intermediate in the remaining tumors (P = 0.03). These data suggest that altered expression of both Bcl-2 and p53 play a role in prostate cancer progression. Combined analysis of factors regulating both apoptosis and cell proliferation may be relevant in prostate cancer.
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PMID:Prognostic significance of Bcl-2 in clinically localized prostate cancer. 862 24

Treatment of a human breast cancer cell line (MDA-MB-435) in nude mice with a recombinant adenovirus containing the human interferon (IFN) consensus gene, IFN-con1 (ad5/IFN), resulted in tumor regression in 100% of the animals. Tumor regression occurred when virus was injected either within 24 hr of tumor cell implantation or with established tumors. However, regression of the tumor was also observed in controls in which either the wild-type virus or a recombinant virus containing the luciferase gene was used, although tumor growth was not completely suppressed. Tumor regression was accompanied by a decrease in p53 expression. Two other tumors, the human myelogenous leukemic cell line K562 and the hamster melanoma tumor RPMI 1846, also responded to treatment but only with ad5/IFN. In the case of K562 tumors, there was complete regression of the tumor, and tumors derived from RPMI 1846 showed partial regression. We propose that the complete regression of the breast cancer with the recombinant virus ad5/IFN was the result of two events: viral oncolysis in which tumor cells are being selectively lysed by the replication-competent virus and the enhanced effect of expression of the IFN-con1 gene. K562 and RPMI 1846 tumors regressed only as a result of IFN gene therapy. This was confirmed by in vitro analysis. Our results indicate that a combination of viral oncolysis with a virus of low pathogenicity, itself resistant to the effects of IFN and IFN gene therapy, might be a fruitful approach to the treatment of a variety of different tumors, in particular breast cancers.
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PMID:Treatment of a human breast cancer xenograft with an adenovirus vector containing an interferon gene results in rapid regression due to viral oncolysis and gene therapy. 863

Although soft tissue sarcoma has a high incidence of p53 mutations, it is not clear if such alterations facilitate tumor growth and metastasis. In this study, fresh autologous normal lymphocytes, normal muscle, primary and metastatic sarcoma tissues from a single synovial sarcoma patient were examined for p53-related alterations that potentially associated with sarcoma tumor development and metastasis. Normal tissues contain two wild-type p53 alleles. Primary sarcoma had one chromosome 17p p53 allelic deletion without apparent p53 mutation in the other allele. However, metastatic tumor had deletion of one p53 allele with an exon 5 codon 135 missense mutation in the other allele. This p53 gene point mutation in the metastasis was associated with the production of mutated p53 protein. A small clone of cells harboring the identical p53 gene point mutation was identified in the primary tumor using mutant allele specific PCR amplification, albeit at levels much less than in the metastatic sarcoma. This single patient example indicate that soft tissue sarcoma metastasis can develop from clonal expansion of primary tumor cells bearing p53 mutations.
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PMID:Soft tissue sarcoma metastasis from clonal expansion of p53 mutated tumor cells. 864 65

There is strong evidence to suggest that insulin and insulin-like growth factor (IGF)-I may be important for tumor growth. Both the insulin and IGF-I receptors (IGF-IR) are overexpressed in breast cancer, and antibody blockade of the IGF-IR inhibits the growth of some breast cancer cell lines. Furthermore, expression of an insulin receptor (IR) in a normal mammary epithelia] cell line causes insulin-dependent transformation. Functional inactivation of p53 is also very frequent in many tumors. In this paper, we investigated whether inactivation of p53 might be involved in the overexpression of the IR in malignancy, specifically breast cancer. We demonstrate a positive correlation between IR and IGF-IR levels and p53 overexpression in primary human breast malignancies. To examine possible mechanisms by which p53 may regulate IR gene expression, we show that p53 can repress the IR promoter and that a dominant-negative p53 (248Q) can de-repress the promoter in cells containing normal p53. The p53 effect was shown to be mediated by C/EBP and Sp1 transcription factors. We also documented that p53-null mice had elevated levels of Sp1, but not C/EBPalpha, and that insulin binding to liver extracts was increased compared to wild-type controls. These results suggest that p53 inactivation may lead to an up-regulation of genes, such as the IR, that are dependent on these transcription factors.
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PMID:Repression of the insulin receptor promoter by the tumor suppressor gene product p53: a possible mechanism for receptor overexpression in breast cancer. 866 14

Antitumor CTL responses were studied in a model tumor hearing a mutant human p53 gene. We found ineffective induction of antitumor CTL in mice bearing these tumors associated with measurable defects in the function of dendritic cells (DC) from these animals. In this study we investigate the mechanism of this defect in mature DC and find that functional DC can be generated by growth from the bone marrow of tumor-hearing animals. Tumor cell supernatants did not affect the function of mature DC obtained from the spleen of tumor-bearing animals, but significantly suppressed the ability to generate functional DC from the bone marrow of control mice in vitro. This suggests that tumor cells may release factors which block early stages of DC maturation from precursors. DC generated from the bone marrow of tumor-bearing mice showed normal potential to stimulate allogeneic T cells, to stimulate anti-mutant p53 peptide-specific cytotoxic T cells, and to induce anti-p53 CTL responses in vivo in control mice. Repeated immunization with peptide-pulsed DC generated from the bone marrow of control mice (every 4-5 days) blocked progression of established tumors. Immunization of mice with peptide-pulsed DC obtained from the spleen of tumor-bearing mice (4 weeks after tumor injection) did not affect the tumor growth, whereas immunization with peptide-pulsed DC generated from bone marrow of tumor-bearing mice resulted in significantly prolonged survival and delayed tumor growth. Tumor progression was associated with change of the balance Th1/Th2 cells in favor of the Th2-like cytokine profile, while effective immunization was associated with a shift to the Th1 phenotype. Thus, frequent immunization of mice with mutant p53 peptide-pulsed DC generated from stem cells of tumor-bearing hosts can induce effective antitumor CTL responses associated with production of Th1 cells and lead to significant antitumor effects.
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PMID:Dendritic cells in antitumor immune responses. II. Dendritic cells grown from bone marrow precursors, but not mature DC from tumor-bearing mice, are effective antigen carriers in the therapy of established tumors. 866 91

The BALB/c Meth A sarcoma carries a p53 missense mutation at codon 234, which occurs in a peptide, termed 234CM, capable of being presented to cytotoxic T lymphocytes (CTL) by H-2Kd molecules (Noguchi, Y., E.C. Richards, Y.-T. Chen, and L.J. Old. 1994. Proc. Natl. Acad. Sci. USA. 91:3171-3175). Immunization of BALB/c mice with bone marrow-derived dendritic cells (DC), generated in the presence of granulocyte macrophage colony-stimulating factor and interleukin 4, and prepulsed with the Meth A p53 mutant peptide, induced CTL that specifically recognized peptide-pulsed P815 cells, as well as Meth A cells naturally expressing this epitope. Immunization with this vaccine also protected naive mice from a subsequent tumor challenge, and it inhibited tumor growth in mice bearing day 7 subcutaneous Meth A tumors. We additionally determined that immunization of BALB/c mice with DC pulsed with the p53 peptide containing the wild-type residue at position 234, 234CW, induced peptide-specific CTL that reacted against several methylcholanthrene-induced BALB/c sarcomas, including CMS4 sarcoma, and rejection of CMS4 sarcoma in vaccination and therapy (day 7) protocols. These results support the efficacy of DC-based, p53-derived peptide vaccines for the immunotherapy of cancer. The translational potential of this strategy is enhanced by previous reports showing that DC can readily be generated from human peripheral blood lymphocytes.
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PMID:Therapy of murine tumors with p53 wild-type and mutant sequence peptide-based vaccines. 866 94

Alterations in apoptosis and associated mechanisms during mammary tumor progression were investigated in transgenic mice expressing the SV40 large T antigen (T(AG)) driven by the rat prostatic steroid-binding protein C3(1) 5'-flanking region. Apoptosis levels, assessed by in situ end labeling, were low in normal mammary epithelial cells, highest in atypical hyperplasias (preneoplastic lesions), and less pronounced in adenocarcinomas. Preneoplastic cells maintain the ability to undergo apoptosis as a mechanism of tumor growth suppression, but this critical control of apoptosis is lost as these lesions progress to carcinomas. These alterations in apoptosis occur during mammary tumor progression in mice containing wild-type p53+/+ genotype as well as in mice with the p53-/- genotype. Thus, apoptosis in this tumor model occurs through a p53-independent mechanism. Because other studies have demonstrated p53-dependent apoptosis in T(AG)-induced choroid plexus tumors of transgenic mice, we propose that the role of p53 in apoptosis may be tissue-specific. In addition, bcl-2 protein was not expressed in any mammary lesions. SV40 T(AG) expression, which correlated with the nuclear p53 protein at all stages of tumor progression, was low in normal mammary epithelial cells, moderately high in atypical hyperplasias, and strongly expressed in adenocarcinomas. No p53 mutations were found at any stage of mammary adenocarcinoma development, suggesting that tumor progression does not require a dominantly acting p53 mutation in this transgenic model. p2l(Waf1/Cip1), a cyclin-dependent kinase inhibitor, was expressed in normal mammary tissue but was not detected in the mammary carcinomas, despite high nuclear accumulation of wild-type p53 protein, suggesting functional loss of p53 due to binding of SV40 T(AG), to p53. These findings suggest that suppression of apoptosis during the transition from atypical hyperplasia to adenocarcinoma appears to be a critical event for mammary cancer development in C3(1)/T(AG) transgenic mice and occurs by p53- and bcl-2-independent pathways.
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PMID:p53-independent apoptosis during mammary tumor progression in C3(1)/SV40 large T antigen transgenic mice: suppression of apoptosis during the transition from preneoplasia to carcinoma. 867 54

In most cervical cancers, the function of p53 is down regulated. To explore the potential use of p53 in gene therapy for cervical cancer, we introduced wild-type p53 into cervical cancer cell lines via a recombinant adenoviral vector, Ad5CMV-p53, and analyzed its effects on cell and tumor growth. The transduction efficiencies of all cell lines were 100% at a multiplicity of infection of 100 or greater. The p53 protein was detected in Ad5CMV-p53-infected cells. Protein expression peaked at day 3 after infection and lasted 15 days. The Ad5CMV-p53-infected cells underwent apoptosis, and cell growth was greatly suppressed. The Ad5CMV-p53 treatment significantly reduced the volumes of established s.c. tumors in vivo. These results indicate that transfection of cervical cancer cells with the wild-type p53 gene via Ad5CMV-p53 is a potential novel approach to the therapy of cervical cancer.
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PMID:Adenovirus-mediated transfer of a wild-type p53 gene and induction of apoptosis in cervical cancer. 867 61


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