Publications by authors named "Wolfgang Deppert"

58 Publications

Immunotherapy of WAP-T mice with early stage mammary gland tumors.

Oncotarget 2017 Sep 29;8(40):67790-67804. Epub 2017 Jun 29.

Heinrich-Pette-Institute, Leibniz-Institute for Experimental Virology, 20251 Hamburg, Germany.

The SV40 transgenic BALB/c mouse based WAP-T/WAP-T model for triple-negative breast cancer allows the analysis of parameters influencing immunotherapeutic approaches. Except for WAP-T tumors expressing the immune-dominant LCMV NP-epitope within SV40 T-antigen (T-Ag) which is not expressed by T-Ag of WAP-T tumors, the tumors are extremely similar. Comparative anti-PD1/PD-L1 immunotherapy of WAP-T and WAP-T mice supported the hypothesis that the immunogenicity of tumor antigen T-cell epitopes strongly influences the success of immune checkpoint blockade therapy, with highly immunogenic T-cell epitopes favoring rapid CTL exhaustion. Here we analyzed the immune response in NP8 mice during early times of tumor development. LCMV infection of lactating NP8 mice induced lifelong tumor protection by memory CTLs. Immunization with LCMV after involution and appearance of T-Ag expressing parity-induced tumor progenitor cells could not cure the mice, as memory CTLs became exhausted. However, immunization significantly prolonged the time of tumor outgrowth. Elimination of exhausted CTLs and of immunosuppressive cells by sub-lethal γ-irradiation, followed by adoptive transfer of NP-epitope specific CTLs into NP8 tumor mice with early lesions, completely prevented tumor outgrowth, when lymphocytes obtained after injection of weakly immunogenic NP8 tumor-derived cells into BALB/c mice were transferred. Transfer of lymphocytes obtained after infection of BALB/c mice with highly immunogenic LCMV into such mice delayed tumor outgrowth for a significant period, but could not prevent it. We conclude that eliminating exhausted CTLs and immune-suppressive cells followed by transfer or generation of low-avidity tumor antigen-specific CTLs might be a promising approach for curative tumor immunotherapy.
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http://dx.doi.org/10.18632/oncotarget.18850DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5620212PMC
September 2017

Cancer immunotherapy: weak beats strong.

Aging (Albany NY) 2016 11;8(11):2607-2608

Heinrich-Pette-Institute, Leibniz-Institute for Experimental Virology, 20251 Hamburg, Germany.

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http://dx.doi.org/10.18632/aging.101134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5191857PMC
November 2016

T-cell epitope strength in WAP-T mouse mammary carcinomas is an important determinant in PD1/PD-L1 immune checkpoint blockade therapy.

Oncotarget 2016 Oct;7(40):64543-64559

Heinrich-Pette-Institute, Leibniz-Institute for Experimental Virology, Hamburg, Germany.

Using the SV40 transgenic WAP-T/WAP-TNP mouse models for mammary carcinomas, we compared the response to immune checkpoint blockade therapy in tumor mice expressing either SV40 T-antigen containing the LCMV NP-epitope (T-AgNP in WAP-TNP mice), or the unmodified T-antigen (T-Ag in WAP-T mice). Specifically, we asked, whether the presence of the highly immunogenic NP-epitope in T-AgNP influences this response in comparison to the weakly immunogenic T-cell epitopes of T-Ag in WAP-T tumor mice. Treatment of WAP-TNP tumor mice with either anti-PD1 or anti-PD-L1 antibodies led to tumor regression, with anti-PD-L1 treatment being more effective. However, tumors had fully re-appeared after 21 days, indicating that CTL exhaustion had been rapidly re-established. Surprisingly, the same treatment applied to WAP-T tumor mice resulted in a significantly prolonged period of tumor regression. We provide evidence that in contrast to the weak antigenic stimuli exerted by T-cell epitopes of T-Ag, the strong antigenic stimulus of the NP-epitope in T-AgNP has a dual effect: (i) a rapid generation of active NP-specific CTLs, accompanied (ii) by accelerated CTL exhaustion. Our data support the hypothesis that the immunogenicity of tumor antigen T-cell epitopes strongly influences the success of immune checkpoint blockade therapy.
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http://dx.doi.org/10.18632/oncotarget.11620DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5323098PMC
October 2016

CEACAM1 controls the EMT switch in murine mammary carcinoma in vitro and in vivo.

Oncotarget 2016 Sep;7(39):63730-63746

Institute for Experimental Immunology and Hepatology, University Medical Center Hamburg-Eppendorf, D-20251 Hamburg, Germany.

We analyzed the molecular basis for carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1)-controlled inhibition of epithelial-mesenchymal transition (EMT) in a mouse model for mammary adenocarcinoma (WAP-T mice). We demonstrate that silencing of CEACAM1 in WAP-T tumor-derived G-2 cells induces epithelial-mesenchymal plasticity (EMP), as evidenced by typical changes of gene expression, morphology and increased invasion. In contrast, reintroduction of CEACAM1 into G-2 cells reversed up-regulation of genes imposing mesenchymal transition, as well as cellular invasion. We identified the Wnt-pathway as target for CEACAM1-mediated repression of EMT. Importantly, β-catenin phosphorylation status and transcriptional activity strongly depend on CEACAM1 expression: CEACAM1high G-2 cells displayed enhanced phosphorylation of β-catenin at S33/S37/T41 and decreased phosphorylation at Y86, thereby inhibiting canonical Wnt/β-catenin signaling. We identified Src-homology 2 domain-containing phosphatase 2 (SHP-2) as a critical binding partner of CEACAM1 that could modulate β-catenin Y86 phosphorylation. Hence, CEACAM1 serves as a scaffold that controls membrane proximal β-catenin signaling. In vivo, mammary tumors of WAP-T/CEACAM1null mice displayed increased nuclear translocation of β-catenin and a dramatically enhanced metastasis rate compared to WAP-T mice. Hence, CEACAM1 controls EMT in vitro and in vivo by site-specific regulation of β-catenin phosphorylation. Survival analyses of human mammary carcinoma patients corroborated these data, indicating that CEACAM1 is a prognostic marker for breast cancer survival.
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http://dx.doi.org/10.18632/oncotarget.11650DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5325399PMC
September 2016

An inducible transgenic mouse breast cancer model for the analysis of tumor antigen specific CD8+ T-cell responses.

Oncotarget 2015 Nov;6(36):38487-503

Heinrich-Pette-Institute, Leibniz-Institute for Experimental Virology, Hamburg, Germany.

In Simian virus 40 (SV40) transgenic BALB/c WAP-T mice tumor development and progression is driven by SV40 tumor antigens encoded by inducible transgenes. WAP-T mice constitute a well characterized mouse model for breast cancer with strong similarities to the corresponding human disease. BALB/c mice mount only a weak cellular immune response against SV40 T-antigen (T-Ag). For studying tumor antigen specific CD8+ T-cell responses against transgene expressing cells, we created WAP-TNP mice, in which the transgene additionally codes for the NP118-126-epitope contained within the nucleoprotein of lymphocytic choriomeningitis virus (LCMV), the immune-dominant T-cell epitope in BALB/c mice. We then investigated in WAP-TNP mice the immune responses against SV40 tumor antigens and the NP-epitope within the chimeric T-Ag/NP protein (T-AgNP). Analysis of the immune-reactivity against T-Ag in WAP-T and of T-AgNP in WAP-TNP mice revealed that, in contrast to wild type (wt) BALB/c mice, WAP-T and WAP-TNP mice were non-reactive against T-Ag. However, like wtBALB/c mice, WAP-T as well as WAP-TNP mice were highly reactive against the immune-dominant LCMV NP-epitope, thereby allowing the analysis of NP-epitope specific cellular immune responses in WAP-TNP mice. LCMV infection of WAP-TNP mice induced a strong, LCMV NP-epitope specific CD8+ T-cell response, which was able to specifically eliminate T-AgNP expressing mammary epithelial cells both prior to tumor formation (i.e. in cells of lactating mammary glands), as well as in invasive tumors. Elimination of tumor cells, however, was only transient, even after repeated LCMV infections. Further studies showed that already non-infected WAP-TNP tumor mice contained LCMV NP-epitope specific CD8+ T-cells, albeit with strongly reduced, though measurable activity. Functional impairment of these 'endogenous' NP-epitope specific T-cells seems to be caused by expression of the programmed death-1 protein (PD1), as anti-PD1 treatment of splenocytes from WAP-TNP tumor mice restored their activity. These characteristics are similar to those found in many tumor patients and render WAP-TNP mice a suitable model for analyzing parameters to overcome the blockade of immune checkpoints in tumor patients.
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http://dx.doi.org/10.18632/oncotarget.5750DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4770716PMC
November 2015

Epithelial-mesenchymal plasticity is a decisive feature for the metastatic outgrowth of disseminated WAP-T mouse mammary carcinoma cells.

BMC Cancer 2015 Mar 26;15:178. Epub 2015 Mar 26.

Institute for Tumor Biology, University Medical Center Hamburg-Eppendorf (UKE), D-20246, Hamburg, Germany.

Background: Experimental analysis of the metastatic cascade requires suitable model systems which allow tracing of disseminated tumor cells and the identification of factors leading to metastatic outgrowth in distant organs. Such models, especially models using immune-competent mice, are rather scarce. We here analyze tumor cell dissemination and metastasis in an immune-competent transplantable mouse mammary tumor model, based on the SV40 transgenic WAP-T mouse mammary carcinoma model.

Methods: We orthotopically transplanted into immune-competent WAP-T mice two tumor cell lines (H8N8, moderately metastatic, and G-2, non-metastatic), developed from primary WAP-T tumors. G-2 and H8N8 cells exhibit stem cell characteristics, form homeostatic, heterotypic tumor cell systems in vitro, and closely mimic endogenous primary tumors after orthotopic transplantation into syngeneic, immune-competent WAP-T mice. Tumor cell transgene-specific PCR allows monitoring of tumor cell dissemination into distinct organs, and immunohistochemistry for SV40 T-antigen tracing of single disseminated tumor cells (DTC).

Results: While only H8N8 cell-derived tumors developed metastases, tumors induced with both cell lines disseminated into a variety of organs with similar efficiency and similar organ distribution. H8N8 metastases arose only in lungs, indicating that organ-specific metastatic outgrowth depends on the ability of DTC to re-establish a tumor cell system rather than on invasion per se. Resection of small tumors (0.5 cm(3)) prevented metastasis of H8N8-derived tumors, most likely due to the rather short half-life of DTC, and thus to shorter exposure of the mice to DTC. In experimental metastasis by tail vein injection, G-2 and H8N8 cells both were able to form lung metastases with similar efficiency. However, after injection of sorted "mesenchymal" and "epithelial" G-2 cell subpopulations, only the "epithelial" subpopulation formed lung metastases.

Conclusions: We demonstrate the utility of our mouse model to analyze factors influencing tumor cell dissemination and metastasis. We suggest that the different metastatic capacity of G-2 and H8N8 cells is due to their different degrees of epithelial-mesenchymal plasticity (EMP), and thus the ability of the respective disseminated cells to revert from a "mesenchymal" to an "epithelial" differentiation state.
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http://dx.doi.org/10.1186/s12885-015-1165-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4381675PMC
March 2015

Lectin histochemistry of murine WAP-T mammary cancer reveals similar glycoconjugate changes to those in human breast cancer.

Anticancer Res 2014 Dec;34(12):7045-53

Institute of Anatomy and Experimental Morphology, University Cancer Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Background: The WAP-T mouse model is an established clinically relevant model of breast cancer. Lectins have been used to study malignant progression in clinical studies. We investigated lectin binding sites to test for the clinical relevance of this model.

Materials And Methods: Samples of the WAP-T mouse mammary tissues, from normal tissues to undifferentiated higher tumor grades were stained using an indirect technique with nine different lectins for intensity of lectin binding.

Results: HPA bound to the luminal epithelium in higher tumor grades in a similar pattern to that in human breast cancer. BSA-IB4 bound to luminal epithelium in hyperplasia and increased towards higher grades, comparable to previous clinical studies. PHA-L-binding to myoepithelium and luminal epithelium increased from hyperplasia to higher grades, comparable to findings in human breast cancer.

Conclusion: The results of our study support the hypothesis that lectin binding sites change similarly in WAP-T and human breast cancer, stressing the similarity of this model with the clinical setting.
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December 2014

Chemotherapy of WAP-T mouse mammary carcinomas aggravates tumor phenotype and enhances tumor cell dissemination.

Int J Cancer 2015 Jul 16;137(1):25-36. Epub 2014 Dec 16.

Department of Hematology and Medical Oncology, University Medical Center, 37075, Goettingen, Germany.

In this study, the effects of the standard chemotherapy, cyclophosphamide/adriamycin/5-fluorouracil (CAF) on tumor growth, dissemination and recurrence after orthotopic implantation of murine G-2 cells were analyzed in the syngeneic immunocompetent whey acidic protein-T mouse model (Wegwitz et al., PLoS One 2010; 5:e12103; Schulze-Garg et al., Oncogene 2000; 19:1028-37). Single-dose CAF treatment reduced tumor size significantly, but was not able to eradicate all tumor cells, as recurrent tumor growth was observed 4 weeks after CAF treatment. Nine days after CAF treatment, residual tumors showed features of regressive alterations and were composed of mesenchymal-like tumor cells, infiltrating immune cells and some tumor-associated fibroblasts with an intense deposition of collagen. Recurrent tumors were characterized by coagulative necrosis and less tumor cell differentiation compared with untreated tumors, suggesting a more aggressive tumor phenotype. In support, tumor cell dissemination was strongly enhanced in mice that had developed recurrent tumors in comparison with untreated controls, although only few disseminated tumor cells could be detected in various organs 9 days after CAF application. In vitro experiments revealed that CAF treatment of G-2 cells eliminates the vast majority of epithelial tumor cells, whereas tumor cells with a mesenchymal phenotype survive. These results together with the in vivo findings suggest that tumor cells that underwent epithelial-mesenchymal transition and/or exhibit stem-cell-like properties are difficult to eliminate using one round of CAF chemotherapy. The model system described here provides a valuable tool for the characterization of the effects of chemotherapeutic regimens on recurrent tumor growth and on tumor cell dissemination, thereby enabling the development and preclinical evaluation of novel therapeutic strategies to target mammary carcinomas.
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http://dx.doi.org/10.1002/ijc.29369DOI Listing
July 2015

Mutant p53 promotes epithelial-mesenchymal plasticity and enhances metastasis in mammary carcinomas of WAP-T mice.

Int J Cancer 2015 Mar 19;136(6):E521-33. Epub 2014 Sep 19.

Department for Tumor Biology, University Medical Center Hamburg-Eppendorf (UKE), D-20246, Hamburg, Germany; Department of Tumor Virology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, D-20251, Hamburg, Germany.

To study the postulated mutant p53 (mutp53) "gain of function" effects in mammary tumor development, progression and metastasis, we crossed SV40 transgenic WAP-T mice with mutant p53 transgenic WAP-mutp53 mice. Compared to tumors in monotransgenic WAP-T mice, tumors in bitransgenic WAP-T x WAP-mutp53 mice showed higher tumor grading, enhanced vascularization, and significantly increased metastasis. Bitransgenic tumors revealed a gene signature associated with the oncogenic epithelial-mesenchymal transition pathway (EMT gene signature). In cultures of WAP-T tumor-derived G-2 cancer cells, which are comprised of subpopulations displaying "mesenchymal" and "epithelial" phenotypes, this EMT gene signature was associated with the "mesenchymal" compartment. Furthermore, ectopic expression of mutp53 in G-2 cells sufficed to induce a strong EMT phenotype. In contrast to these in vitro effects, monotransgenic and bitransgenic tumors were phenotypically similar suggesting that in vivo the tumor cell phenotype might be under control of the tumor microenvironment. In support, orthotopic transplantation of G-2 cells as well as of G-2 cells expressing ectopic mutp53 into syngeneic mice resulted in tumors with a predominantly epithelial phenotype, closely similar to that of endogenous primary tumors. We conclude that induction of an EMT gene signature by mutp53 in bitransgenic tumors primarily promotes tumor cell plasticity, that is, the probability of tumor cells to undergo EMT processes under appropriate stimuli, thereby possibly increasing their potential to disseminate and metastasize.
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http://dx.doi.org/10.1002/ijc.29186DOI Listing
March 2015

Aberrant Proliferation of Differentiating Alveolar Cells Induces Hyperplasia in Resting Mammary Glands of SV40-TAg Transgenic Mice.

Front Oncol 2014 26;4:168. Epub 2014 Jun 26.

Heinrich Pette Institute, Leibniz Institute for Experimental Virology , Hamburg , Germany.

WAP-T1 transgenic mice express SV40-TAg under control of the whey acidic protein (WAP) promoter, which directs activity of this strong viral oncogene to luminal cells of the mammary gland. Resting uniparous WAP-T1 glands develop hyperplasia composed of TAg positive cells prior to appearance of advanced tumor stages. We show that cells in hyperplasia display markers of alveolar differentiation, suggesting that TAg targets differentiating cells of the alveolar compartment. The glands show significant expression of Elf5 and milk genes (Lalba, Csn2, and Wap). TAg expressing cells largely co-stain with antibodies to Elf5, lack the epithelial marker Sca1, and are hormone receptor negative. High expression levels of Elf5 but not of milk genes are also seen in resting glands of normal BALB/c mice. This indicates that expression of Elf5 in resting WAP-T1 glands is not specifically induced by TAg. CK6a positive luminal cells lack TAg. These cells co-express the markers prominin-1, CK6a, and Sca1, and are positive for hormone receptors. These hormone sensitive cells localize to ducts and seem not to be targeted by TAg. Despite reaching an advanced stage in alveolar differentiation, the cells in hyperplasia do not exit the cell cycle. Thus, expression of TAg in conjunction with regular morphogenetic processes of alveologenesis seem to provide the basis for a hormone independent, unscheduled proliferation of differentiating cells in resting glands of WAP-T1 transgenic mice, leading to the formation of hyperplastic lesions.
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http://dx.doi.org/10.3389/fonc.2014.00168DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4071642PMC
July 2014

Preferential binding of hot spot mutant p53 proteins to supercoiled DNA in vitro and in cells.

PLoS One 2013 26;8(3):e59567. Epub 2013 Mar 26.

Department of Biophysical Chemistry and Molecular Oncology, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic.

Hot spot mutant p53 (mutp53) proteins exert oncogenic gain-of-function activities. Binding of mutp53 to DNA is assumed to be involved in mutp53-mediated repression or activation of several mutp53 target genes. To investigate the importance of DNA topology on mutp53-DNA recognition in vitro and in cells, we analyzed the interaction of seven hot spot mutp53 proteins with topologically different DNA substrates (supercoiled, linear and relaxed) containing and/or lacking mutp53 binding sites (mutp53BS) using a variety of electrophoresis and immunoprecipitation based techniques. All seven hot spot mutp53 proteins (R175H, G245S, R248W, R249S, R273C, R273H and R282W) were found to have retained the ability of wild-type p53 to preferentially bind circular DNA at native negative superhelix density, while linear or relaxed circular DNA was a poor substrate. The preference of mutp53 proteins for supercoiled DNA (supercoil-selective binding) was further substantiated by competition experiments with linear DNA or relaxed DNA in vitro and ex vivo. Using chromatin immunoprecipitation, the preferential binding of mutp53 to a sc mutp53BS was detected also in cells. Furthermore, we have shown by luciferase reporter assay that the DNA topology influences p53 regulation of BAX and MSP/MST1 promoters. Possible modes of mutp53 binding to topologically constrained DNA substrates and their biological consequences are discussed.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0059567PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3608670PMC
September 2013

Transcription factors link mouse WAP-T mammary tumors with human breast cancer.

Int J Cancer 2013 Mar 13;132(6):1311-22. Epub 2012 Dec 13.

Department of Clinical Chemistry, Center for Diagnostic, University Medical Center Hamburg-Eppendorf, D-20246 Hamburg, Germany.

Mouse models are important tools to decipher the molecular mechanisms of mammary carcinogenesis and to mimic the respective human disease. Despite sharing common phenotypic and genetic features, the proper translation of murine models to human breast cancer remains a challenging task. In a previous study we showed that in the SV40 transgenic WAP-T mice an active Met-pathway and epithelial-mesenchymal characteristics distinguish low- and high-grade mammary carcinoma. To assign these murine tumors to corresponding human tumors we here incorporated the analysis of expression of transcription factor (TF) coding genes and show that thereby a more accurate interspecies translation can be achieved. We describe a novel cross-species translation procedure and demonstrate that expression of unsupervised selected TFs, such as ELF5, HOXA5 and TFCP2L1, can clearly distinguish between the human molecular breast cancer subtypes--or as, for example, expression of TFAP2B between yet unclassified subgroups. By integrating different levels of information like histology, gene set enrichment, expression of differentiation markers and TFs we conclude that tumors in WAP-T mice exhibit similarities to both, human basal-like and non-basal-like subtypes. We furthermore suggest that the low- and high-grade WAP-T tumor phenotypes might arise from distinct cells of tumor origin. Our results underscore the importance of TFs as common cross-species denominators in the regulatory networks underlying mammary carcinogenesis.
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http://dx.doi.org/10.1002/ijc.27941DOI Listing
March 2013

A novel niche for skin derived precursors in non-follicular skin.

J Dermatol Sci 2013 Feb 26;69(2):132-9. Epub 2012 Oct 26.

Beiersdorf AG, R&D, Skin Research Center, Unnastrasse 48, Hamburg 20245, Germany.

Background: Skin derived precursors (SKP) comprise a subset of specialized dermal cells that can be distinguished from fibroblast by their capacity for spheroidal growth. Recent investigations have shown that hair follicles constitute a niche for this cell type, but their localization and their definite function in non-follicular skin remains largely unknown.

Objective: To identify the dermal niche of non-follicular SKPs and to analyze whether functional aspects correlate with this localization.

Methods: SKPs were isolated from separate anatomical regions of human abdominal skin. Fluorescence activated cell sorting then was used to obtain a pure population of non-follicular SKPs. Functional characterization of these cells was performed applying differentiation and proliferation assays. Information on specific in vivo functions was derived from histological evaluation of quantity and localization patterns.

Results: Sphere forming capacity and differentiation assays show that SKPs reside in the papillary part of the dermis. Further delineation revealed that the dermal capillaries represent a niche for these cells which subsequently could be isolated by FACS utilizing a perivascular marker. Whereas functional properties described for follicular SKPs could also be detected in the perivascular SKP population, histological analyses additionally point to a cross-talk with epidermal stem cells and a reduction during chronological aging.

Conclusion: Our data show that SKPs isolated from non-follicular skin originate from a perivascular niche. Compared to their follicular counterparts, no functional differences could be observed upon cultivation, but ex vivo analyses also point to unique functions and a contribution to the phenotype of aged skin.
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http://dx.doi.org/10.1016/j.jdermsci.2012.10.007DOI Listing
February 2013

CEBP factors regulate telomerase reverse transcriptase promoter activity in whey acidic protein-T mice during mammary carcinogenesis.

Int J Cancer 2013 May 25;132(9):2032-43. Epub 2012 Oct 25.

Institute of Molecular Medicine and Max-Planck Research Group on Stem Cell Aging, Ulm, Germany.

Telomerase is activated in the majority of invasive breast cancers, but the time point of telomerase activation during mammary carcinogenesis is not clear. We have recently presented a transgenic mouse model to study human telomerase reverse transcriptase (TERT) gene expression in vivo (hTERTp-lacZ). In the present study, hTERTp-lacZxWAP-T bitransgenic mice were generated to analyze the mechanisms responsible for human and mouse TERT upregulation during tumor progression in vivo. We found that telomerase activity and TERT expression were consistently upregulated in SV40-induced invasive mammary tumors compared to normal and hyperplastic tissues and ductal carcinoma in situ (DCIS). Human and mouse TERT genes are regulated similarly in the breast tissue, involving the CEBP transcription factors. Loss of CEBP-α and induction of CEBP-β expression correlated well with the activation of TERT expression in mouse mammary tumors. Transfection of CEBP-α into human or murine cells resulted in TERT repression, whereas knockdown of CEBP-α in primary human mammary epithelial cells resulted in reactivation of endogenous TERT expression and telomerase activity. Conversely, ectopic expression of CEBP-β activated endogenous TERT gene expression. Moreover, ChIP and EMSA experiments revealed binding of CEBP-α and CEBP-β to human TERT-promoter. This is the first evidence indicating that CEBP-α and CEBP-β are involved in TERT gene regulation during carcinogenesis.
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http://dx.doi.org/10.1002/ijc.27880DOI Listing
May 2013

Recombinant p53 displays heterogeneity during isoelectric focusing.

Electrophoresis 2012 Sep;33(18):2818-27

Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany.

Human recombinant, baculovirus-expressed p53 protein focuses on 2D gels in multiple spots in the narrow pI range. Re-electrophoresis of the individual spots resulted in the appearance of multiple spots. The strings of spots were neither species specific, nor characteristic for baculovirus-expressed p53. Moreover, mutant p53 did not deviate from wild-type p53, indicating that this is an inherent property of p53. Okadaic acid treatment of insect cells, phosphate substitution reaction of purified p53, and individual analysis of all spots by mass spectrometry revealed that only a fraction of the recombinant p53 is phosphorylated. This finding excluded that the individual p53 spots in 2D gels reflect charge isomers generated by phosphorylation, but rather suggest that they are due to conformational flexibility of urea-denatured monomeric p53 molecules or deamidation of asparagine and glutamine residues. The latter possibility was confirmed by NanoLC-ESI MS/MS analysis. Our data provide a putative hint for a novel regulatory level for function and stability of p53, particularly the long-lived mutant p53 overexpressed in diverse tumor types.
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http://dx.doi.org/10.1002/elps.201200205DOI Listing
September 2012

Low-grade and high-grade mammary carcinomas in WAP-T transgenic mice are independent entities distinguished by Met expression.

Int J Cancer 2013 Mar 26;132(6):1300-10. Epub 2012 Sep 26.

Department of Clinical Chemistry/Central Laboratories, Center for Diagnostic, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Mammary carcinomas developing in SV40 transgenic WAP-T mice arise in two distinct histological phenotypes: as differentiated low-grade and undifferentiated high-grade tumors. We integrated different types of information such as histological grading, analysis of aCGH-based gene copy number and gene expression profiling to provide a comprehensive molecular description of mammary tumors in WAP-T mice. Applying a novel procedure for the correlation of gene copy number with gene expression on a global scale, we observed in tumor samples a global coherence between genotype and transcription. This coherence can be interpreted as a matched transcriptional regulation inherited from the cells of tumor origin and determined by the activity of cancer driver genes. Despite common recurrent genomic aberrations, e.g. gain of chr. 15 in most WAP-T tumors, loss of chr. 19 frequently occurs only in low-grade tumors. These tumors show features of "basal-like" epithelial differentiation, particularly expression of keratin 14. The high-grade tumors are clearly separated from the low-grade tumors by strong expression of the Met gene and by coexpression of epithelial (e.g. keratin 18) and mesenchymal (e.g. vimentin) markers. In high-grade tumors, the expression of the nonmutated Met protein is associated with Met-locus amplification and Met activity. The role of Met as a cancer driver gene is supported by the contribution of active Met signaling to motility and growth of mammary tumor-derived cells. Finally, we discuss the independent origin of low- and high-grade tumors from distinct cells of tumor origin, possibly luminal progenitors, distinguished by Met gene expression and Met signaling.
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http://dx.doi.org/10.1002/ijc.27783DOI Listing
March 2013

Mutant p53 is a transcriptional co-factor that binds to G-rich regulatory regions of active genes and generates transcriptional plasticity.

Cell Cycle 2012 Sep 21;11(17):3290-303. Epub 2012 Aug 21.

Heinrich-Pette Institute, Hamburg, Germany.

The molecular mechanisms underlying mutant p53 (mutp53) "gain-of-function" (GOF) are still insufficiently understood, but there is evidence that mutp53 is a transcriptional regulator that is recruited by specialized transcription factors. Here we analyzed the binding sites of mutp53 and the epigenetic status of mutp53-regulated genes that had been identified by global expression profiling upon depletion of endogenous mutp53 (R273H) expression in U251 glioblastoma cells. We found that mutp53 preferentially and autonomously binds to G/C-rich DNA around transcription start sites (TSS) of many genes characterized by active chromatin marks (H3K4me3) and frequently associated with transcription-competent RNA polymerase II. Mutp53-bound regions overlap predominantly with CpG islands and are enriched in G4-motifs that are prone to form G-quadruplex structures. In line, mutp53 binds and stabilizes a well-characterized G-quadruplex structure in vitro. Hence, we assume that binding of mutp53 to G/C-rich DNA regions associated with a large set of cancer-relevant genes is an initial step in their regulation by mutp53. Using GAS1 and HTR2A as model genes, we show that mutp53 affects several parameters of active transcription. Finally, we discuss a dual mode model of mutp53 GOF, which includes both stochastic and deterministic components.
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http://dx.doi.org/10.4161/cc.21646DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3466528PMC
September 2012

Chlormadinone acetate suppresses prostaglandin biosynthesis in human endometrial explants.

Fertil Steril 2012 Oct 4;98(4):1017-22. Epub 2012 Jul 4.

Department of Obstetrics and Gynecology, Clinic for Endocrinology and Reproductive Medicine, University of Freiburg, Freiburg, Germany.

Objective: To elucidate the mode of action of chlormadinone acetate (CMA) in reducing dysmenorrheic pain by studying the effects of CMA and dexamethasone (DEX) on messenger RNA (mRNA) abundance of cyclo-oxygenase-2 (COX-2), annexin-1 (ANXA1), glucocorticoid receptor (GR), progesterone receptor (PR), and concentrations of prostaglandin F(2α) (PGF(2α)) and leukotrienes B(4) (LTB(4)) and C(4) (LTC(4)) in human endometrial explants.

Design: Ex vivo study.

Setting: University hospital.

Patient(s): Fifteen premenopausal patients undergoing surgery for benign gynecologic disorders.

Intervention(s): Endometrial explants were obtained by aspiration curettage and stimulated ex vivo with interleukin-1β before exposure to CMA or DEX; mRNA levels were determined via reverse transcription-quantitative real-time polymerase chain reaction, and concentrations of arachidonic acid metabolites by enzyme immunoassays.

Main Outcome Measure(s): Messenger RNA levels of COX-2, ANXA1, PR, and GR; concentrations of PGF(2α), LTB(4), and LTC(4) in endometrial explants treated with CMA or DEX.

Result(s): In IL-1β-treated explants COX-2 mRNA and PGF(2α), concentrations were significantly down-regulated by CMA but not by DEX. Chlormadinone acetate did not affect mRNA abundance of ANXA1, PR, and GR.

Conclusion(s): Our data suggest that CMA is a suppressor of COX-2 expression. Comparison with DEX revealed that progestin-specific activity of CMA may mainly be responsible for suppression of prostaglandin biosynthesis in human endometrium.
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http://dx.doi.org/10.1016/j.fertnstert.2012.06.010DOI Listing
October 2012

Impaired CK1 delta activity attenuates SV40-induced cellular transformation in vitro and mouse mammary carcinogenesis in vivo.

PLoS One 2012 3;7(1):e29709. Epub 2012 Jan 3.

Department of General-, Visceral- and Transplantation Surgery, University of Ulm, Ulm, Germany.

Simian virus 40 (SV40) is a powerful tool to study cellular transformation in vitro, as well as tumor development and progression in vivo. Various cellular kinases, among them members of the CK1 family, play an important role in modulating the transforming activity of SV40, including the transforming activity of T-Ag, the major transforming protein of SV40, itself. Here we characterized the effects of mutant CK1δ variants with impaired kinase activity on SV40-induced cell transformation in vitro, and on SV40-induced mammary carcinogenesis in vivo in a transgenic/bi-transgenic mouse model. CK1δ mutants exhibited a reduced kinase activity compared to wtCK1δ in in vitro kinase assays. Molecular modeling studies suggested that mutation N172D, located within the substrate binding region, is mainly responsible for impaired mutCK1δ activity. When stably over-expressed in maximal transformed SV-52 cells, CK1δ mutants induced reversion to a minimal transformed phenotype by dominant-negative interference with endogenous wtCK1δ. To characterize the effects of CK1δ on SV40-induced mammary carcinogenesis, we generated transgenic mice expressing mutant CK1δ under the control of the whey acidic protein (WAP) gene promoter, and crossed them with SV40 transgenic WAP-T-antigen (WAP-T) mice. Both WAP-T mice as well as WAP-mutCK1δ/WAP-T bi-transgenic mice developed breast cancer. However, tumor incidence was lower and life span was significantly longer in WAP-mutCK1δ/WAP-T bi-transgenic animals. The reduced CK1δ activity did not affect early lesion formation during tumorigenesis, suggesting that impaired CK1δ activity reduces the probability for outgrowth of in situ carcinomas to invasive carcinomas. The different tumorigenic potential of SV40 in WAP-T and WAP-mutCK1δ/WAP-T tumors was also reflected by a significantly different expression of various genes known to be involved in tumor progression, specifically of those involved in wnt-signaling and DNA repair. Our data show that inactivating mutations in CK1δ impair SV40-induced cellular transformation in vitro and mouse mammary carcinogenesis in vivo.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0029709PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250488PMC
May 2012

Critical evaluation of human endometrial explants as an ex vivo model system: a molecular approach.

Mol Hum Reprod 2011 Apr 29;17(4):255-65. Epub 2010 Nov 29.

Department of Obstetrics and Gynecology (Endocrinology Laboratory), University Hospital Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany.

The human endometrium is unique among adult tissues. Its functions are modulated by numerous hormones and mediators. The aim of this study was to evaluate the suitability of human endometrial explants for studying functional effects of chemicals and drugs on gene expression biomarkers. Endometrial tissues were obtained by aspiration curettage and cultivated for up to 24 h. Relative mRNA concentrations were determined by reverse transcription quantitative real-time PCR. Viability was assessed by light microscopy, lactate dehydrogenase assay and scanning electron microscopy. It was acceptable after 6 h of culture but reduced after 24 h. Culture-induced alterations of mRNA levels were found for progesterone receptor, estrogen receptor(α), leukemia inhibitory factor and cyclooxygenase-2 in tissues from all cycle stages. The suitability of the model to detect chemical effects was demonstrated by the down-regulation of cyclooxygenase-2 mRNA by chlormadinone acetate in proliferative and secretory endometrium. The model is mainly restricted by interindividual variations and varying tissue quality. An advantage is the preservation of tissue composition. We conclude that human endometrial explants are a complex model due to limited viability, difficult standardization and intrinsic alterations during culture. Experiments with this model should be performed over a limited time period under strictly controlled conditions.
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http://dx.doi.org/10.1093/molehr/gaq095DOI Listing
April 2011

A rapid and optimization-free procedure allows the in vivo detection of subtle cell cycle and ploidy alterations in tissues by flow cytometry.

Cell Cycle 2010 Sep;9(17):3584-90

Children’s Medical Research Institute, Westmead, Australia.

Cell cycle alterations are fundamental to many physiological processes but their detection has proven difficult when cells are in the context of a tissue structure. Here we describe an easy, rapid and optimization-free procedure for obtaining high resolution cell cycle profiles from nearly all tissue types derived from mouse, human and sheep. Using a standardized and non-enzymatic procedure that is universally suitable for soft, solid and epithelial tissues alike, we reproducibly obtain cell cycle profiles of highest quality with half peak coefficients of variation below 2.0. We are able to reduce preparation-derived debris to almost zero and efficiently exclude doublets, but retain multinucleated cells and apoptotic subG1-fragments. Applying this technique, we determine DNA-indices as small as 1.09 in tumor samples containing large necrotic areas and follow ploidy changes within different sections of individual tumors. Moreover, we examine tissue-specific cell cycle arrest and apoptosis as an in vivo stress response caused by radiation of mice. This method significantly improves the quality of DNA content analysis in tissues and extends the spectrum of applications. It allows assessing changes in ploidy, cell cycle distribution and apoptosis/necrosis in vivo and should be instrumental in all research that involves experimental animal models and/or patient biopsies.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3047621PMC
http://dx.doi.org/10.4161/cc.9.17.12831DOI Listing
September 2010

A comprehensive analysis of microRNA expression during human keratinocyte differentiation in vitro and in vivo.

J Invest Dermatol 2011 Jan 9;131(1):20-9. Epub 2010 Sep 9.

Beiersdorf AG, R&D, Skin Research Center, Hamburg, Germany.

Here, we report a comprehensive investigation of changes in microRNA (miRNA) expression profiles on human keratinocyte (HK) differentiation in vitro and in vivo. We have monitored expression patterns of 377 miRNAs during calcium-induced differentiation of primary HKs, and have compared these patterns with miRNA expression profiles of epidermal stem cells, transient amplifying cells, and terminally differentiated HKs from human skin. Apart from the previously described miR-203, we found an additional nine miRNAs (miR-23b, miR-95, miR-210, miR-224, miR-26a, miR-200a, miR-27b, miR-328, and miR-376a) that are associated with HK differentiation in vitro and in vivo. In situ hybridization experiments confirmed miR-23b as a marker of HK differentiation in vivo. Additionally, gene ontology analysis and functional validation of predicted miRNA targets using 3'-untranslated region-luciferase assays suggest that multiple miRNAs that are upregulated on HK differentiation cooperate to regulate gene expression during skin development. Our results thus provide the basis for further analysis of miRNA functions during epidermal differentiation.
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http://dx.doi.org/10.1038/jid.2010.268DOI Listing
January 2011

Tumorigenic WAP-T mouse mammary carcinoma cells: a model for a self-reproducing homeostatic cancer cell system.

PLoS One 2010 Aug 11;5(8):e12103. Epub 2010 Aug 11.

Department of Tumor Virology, Heinrich-Pette-Institute for Experimental Virology and Immunology, Hamburg, Germany.

Background: In analogy to normal stem cell differentiation, the current cancer stem cell (CSC) model presumes a hierarchical organization and an irreversible differentiation in tumor tissue. Accordingly, CSCs should comprise only a small subset of the tumor cells, which feeds tumor growth. However, some recent findings raised doubts on the general applicability of the CSC model and asked for its refinement.

Methodology/principal Findings: In this study we analyzed the CSC properties of mammary carcinoma cells derived from transgenic (WAP-T) mice. We established a highly tumorigenic WAP-T cell line (G-2 cells) that displays stem-like traits. G-2 cells, as well as their clonal derivates, are closely related to primary tumors regarding histology and gene expression profiles, and reflect heterogeneity regarding their differentiation states. G-2 cultures comprise cell populations in distinct differentiation states identified by co-expression of cytoskeletal proteins (cytokeratins and vimentin), a combination of cell surface markers and a set of transcription factors. Cellular subsets sorted according to expression of CD24a, CD49f, CD61, Epcam, Sca1, and Thy1 cell surface proteins, or metabolic markers (e.g. ALDH activity) are competent to reconstitute the initial cellular composition. Repopulation efficiency greatly varies between individual subsets and is influenced by interactions with the respective complementary G-2 cellular subset. The balance between differentiation states is regulated in part by the transcription factor Sox10, as depletion of Sox10 led to up-regulation of Twist2 and increased the proportion of Thy1-expressing cells representing cells in a self-renewable, reversible, quasi-mesenchymal differentiation state.

Conclusions/significance: G-2 cells constitute a self-reproducing cancer cell system, maintained by bi- and unidirectional conversion of complementary cellular subsets. Our work contributes to the current controversial discussion on the existence and nature of CSC and provides a basis for the incorporation of alternative hypotheses into the CSC model.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0012103PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2920333PMC
August 2010

Metabolic sensing by p53: keeping the balance between life and death.

Proc Natl Acad Sci U S A 2010 Jul 20;107(30):13193-4. Epub 2010 Jul 20.

The Heinrich-Pette Institute for Experimental Virology and Immunology, D-20251 Hamburg, Germany.

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http://dx.doi.org/10.1073/pnas.1007945107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2922174PMC
July 2010

In situ localization of epidermal stem cells using a novel multi epitope ligand cartography approach.

Integr Biol (Camb) 2010 Jun 8;2(5-6):241-9. Epub 2010 Jun 8.

Beiersdorf AG, R&D, Skin Research Center, Unnastrasse 48, Hamburg, Germany.

Precise knowledge of the frequency and localization of epidermal stem cells within skin tissue would further our understanding of their role in maintaining skin homeostasis. As a novel approach we used the recently developed method of multi epitope ligand cartography, applying a set of described putative epidermal stem cell markers. Bioinformatic evaluation of the data led to the identification of several discrete basal keratinocyte populations, but none of them displayed the complete stem cell marker set. The distribution of the keratinocyte populations within the tissue was remarkably heterogeneous, but determination of distance relationships revealed a population of quiescent cells highly expressing p63 and the integrins alpha(6)/beta(1) that represent origins of a gradual differentiation lineage. This population comprises about 6% of all basal cells, shows a scattered distribution pattern and could also be found in keratinocyte holoclone colonies. The data suggest that this population identifies interfollicular epidermal stem cells.
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http://dx.doi.org/10.1039/b926147hDOI Listing
June 2010

Chloroquine activates the p53 pathway and induces apoptosis in human glioma cells.

Neuro Oncol 2010 Apr 27;12(4):389-400. Epub 2010 Jan 27.

The Translational Neurooncology Research Group, Department of Neurosurgery, Georg-August University Göttingen, Robert-Koch-Strasse 40, 37075 Göttingen, Germany.

Glioblastoma is the most common malignant brain tumor in adults. The currently available treatments offer only a palliative survival advantage and the need for effective treatments remains an urgent priority. Activation of the p53 growth suppression/apoptotic pathway is one of the promising strategies in targeting glioma cells. We show that the quinoline derivative chloroquine activates the p53 pathway and suppresses growth of glioma cells in vitro and in vivo in an orthotopic (U87MG) human glioblastoma mouse model. Induction of apoptosis is one of the mechanisms underlying the effects of chloroquine on suppressing glioma cell growth and viability. siRNA-mediated downregulation of p53 in wild-type but not mutant p53 glioblastoma cells substantially impaired chloroquine-induced apoptosis. In addition to its p53-activating effects, chloroquine may also inhibit glioma cell growth via p53-independent mechanisms. Our results clarify the mechanistic basis underlying the antineoplastic effect of chloroquine and reveal its therapeutic potential as an adjunct to glioma chemotherapy.
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http://dx.doi.org/10.1093/neuonc/nop046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2940600PMC
April 2010

Analysis of cell type-specific expression of CK1 epsilon in various tissues of young adult BALB/c Mice and in mammary tumors of SV40 T-Ag-transgenic mice.

J Histochem Cytochem 2010 Jan 15;58(1):1-15. Epub 2009 Sep 15.

Department of General, Visceral, and Transplantation Surgery, University of Ulm, Steinhövelstr. 9, 89075 Ulm, Germany.

Casein kinase 1 epsilon (CK1epsilon) is involved in various cellular processes, including cell growth, differentiation, and apoptosis, vesicle transport, and control of the circadian rhythm. Deregulation of CK1epsilon has been linked to neurodegenerative diseases and cancer. To better understand the cell type-specific functions of CK1epsilon, we determined its localization by immunhistochemistry in tissues of healthy, young adult BALB/c mice and in mammary tumors of SV40 T-antigen-transgenic mice. CK1epsilon expression was found to be highly regulated in normal tissues of endodermal, mesodermal, and ectodermal origin and in neoplastic tissue of mammary cancer. The data presented here give an overview of CK1epsilon reactivity in different organs under normal conditions and outline changes in its expression in mammary carcinomas. Our data suggest a cell/organ type-specific function of CK1epsilon and indicate that tumorigenic conversion of mammary glands in SV40 T-antigen-transgenic mice leads to downregulation of CK1epsilon. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.
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http://dx.doi.org/10.1369/jhc.2009.954628DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2796610PMC
January 2010

The p53 transcriptional synapse: activation on demand.

Nat Struct Mol Biol 2009 Sep;16(9):900-1

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http://dx.doi.org/10.1038/nsmb0909-900DOI Listing
September 2009

Wild-type p53 enhances efficiency of simian virus 40 large-T-antigen-induced cellular transformation.

J Virol 2009 Oct 22;83(19):10106-18. Epub 2009 Jul 22.

Heinrich-Pette-Institute for Experimental Virology and Immunology Martinistr. 52, D-20251 Hamburg, Germany.

Abortive infection of BALB/c mouse embryo fibroblasts differing in p53 gene status (p53(+/+) versus p53(-/)(-)) with simian virus 40 (SV40) revealed a quantitatively and qualitatively decreased transformation efficiency in p53(-/-) cells compared to p53(+/+) cells, suggesting a supportive effect of wild-type (wt) p53 in the SV40 transformation process. SV40 transformation efficiency also was low in immortalized p53(-/-) BALB/c 10-1 cells but could be restored to approximately the level in immortalized p53(+/+) BALB/c 3T3 cells by reconstituting wt p53, but not mutant p53 (mutp53), expression. Stable expression of large T antigen (LT) in p53(+/+) 3T3 cells resulted in full transformation, while LT expression in p53(-/-) 10-1 cells could not promote growth in suspension or in soft agar to a significant extent. The helper effect of wt p53 is mediated by its cooperation with LT and resides in the p53 N terminus, as an N-terminally truncated p53 (DeltaNp53) could not rescue the p53-null phenotype. The p53 N terminus serves as a scaffold for recruiting transcriptional regulators like p300/CBP and Mdm2 into the LT-p53 complex. Consequently, LT affected global and specific gene expression in p53(+/+) cells significantly more than in p53(-/-) cells. Our data suggest that recruitment of transcriptional regulators into the LT-p53 complex may help to modify cellular gene expression in response to the needs of cellular transformation.
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http://dx.doi.org/10.1128/JVI.00174-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2748005PMC
October 2009