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Skelin J, Tomaić V. Comparative Analysis of Alpha and Beta HPV E6 Oncoproteins: Insights into Functional Distinctions and Divergent Mechanisms of Pathogenesis. Viruses 2023; 15:2253. [PMID: 38005929 PMCID: PMC10674601 DOI: 10.3390/v15112253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 11/09/2023] [Accepted: 11/10/2023] [Indexed: 11/26/2023] Open
Abstract
Human papillomaviruses (HPVs) represent a diverse group of DNA viruses that infect epithelial cells of mucosal and cutaneous tissues, leading to a wide spectrum of clinical outcomes. Among various HPVs, alpha (α) and beta (β) types have garnered significant attention due to their associations with human health. α-HPVs are primarily linked to infections of the mucosa, with high-risk subtypes, such as HPV16 and HPV18, being the major etiological agents of cervical and oropharyngeal cancers. In contrast, β-HPVs are predominantly associated with cutaneous infections and are commonly found on healthy skin. However, certain β-types, notably HPV5 and HPV8, have been implicated in the development of non-melanoma skin cancers in immunocompromised individuals, highlighting their potential role in pathogenicity. In this review, we comprehensively analyze the similarities and differences between α- and β-HPV E6 oncoproteins, one of the major drivers of viral replication and cellular transformation, and how these impact viral fitness and the capacity to induce malignancy. In particular, we compare the mechanisms these oncoproteins use to modulate common cellular processes-apoptosis, DNA damage repair, cell differentiation, and the immune response-further shedding light on their shared and distinct features, which enable them to replicate at divergent locations of the human body and cause different types of cancer.
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Affiliation(s)
| | - Vjekoslav Tomaić
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia;
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2
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Emin K, Nuvit C, Serpil D, Enver B, Ataseven VS, Volkan Y, Fırat D, Hilmi N, Celal Sahin E, Ugur A, Mushap K, Ayfer Y. Molecular detection of Papillomavirus and immunohistochemical investigation of p53 gene expressions in bovine papillomas and fibropapillomas. Arch Microbiol 2022; 204:278. [DOI: 10.1007/s00203-022-02902-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 04/01/2022] [Accepted: 04/04/2022] [Indexed: 12/01/2022]
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3
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Farooq QUA, Shaukat Z, Zhou T, Aiman S, Gong W, Li C. Inferring Virus-Host relationship between HPV and its host Homo sapiens using protein interaction network. Sci Rep 2020; 10:8719. [PMID: 32457456 PMCID: PMC7251128 DOI: 10.1038/s41598-020-65837-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 05/11/2020] [Indexed: 12/14/2022] Open
Abstract
Human papilloma virus (HPV) is a serious threat to human life globally with over 100 genotypes including cancer causing high risk HPVs. Study on protein interaction maps of pathogens with their host is a recent trend in ‘omics’ era and has been practiced by researchers to find novel drug targets. In current study, we construct an integrated protein interaction map of HPV with its host human in Cytoscape and analyze it further by using various bioinformatics tools. We found out 2988 interactions between 12 HPV and 2061 human proteins among which we identified MYLK, CDK7, CDK1, CDK2, JAK1 and 6 other human proteins associated with multiple viral oncoproteins. The functional enrichment analysis of these top-notch key genes is performed using KEGG pathway and Gene Ontology analysis, which reveals that the gene set is enriched in cell cycle a crucial cellular process, and the second most important pathway in which the gene set is involved is viral carcinogenesis. Among the viral proteins, E7 has the highest number of associations in the network followed by E6, E2 and E5. We found out a group of genes which is not targeted by the existing drugs available for HPV infections. It can be concluded that the molecules found in this study could be potential targets and could be used by scientists in their drug design studies.
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Affiliation(s)
- Qurat Ul Ain Farooq
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Zeeshan Shaukat
- Faculty of Information Technology, Beijing University of Technology, Beijing, 100124, China
| | - Tong Zhou
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Sara Aiman
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Weikang Gong
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Chunhua Li
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China.
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Steels A, Vannevel L, Zwaenepoel O, Gettemans J. Nb-induced stabilisation of p53 in HPV-infected cells. Sci Rep 2019; 9:12680. [PMID: 31481667 PMCID: PMC6722090 DOI: 10.1038/s41598-019-49061-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 08/13/2019] [Indexed: 11/23/2022] Open
Abstract
Cervical cancer is caused by a persistent infection of the mucosal epithelia with high-risk human papilloma viruses (HPVs). The viral oncoprotein E6 is responsible for the inactivation of the tumour suppressor p53 and thus plays a crucial role in HPV-induced tumorigenesis. The viral E6 protein forms a trimeric complex with the endogenous E3 ubiquitine ligase E6AP and the DNA-binding domain (DBD) of p53, which results in the polyubiquitination and proteasomal degradation of p53. We have developed nanobodies (Nbs) against the DBD of p53, which substantially stabilise p53 in HeLa cells. The observed effect is specific for HPV-infected cells, since similar effects were not seen for U2OS cells. Despite the fact that the stabilised p53 was strongly nuclear enriched, its tumour suppressive functions were hampered. We argue that the absence of a tumour suppressive effect is caused by inhibition of p53 transactivation in both HPV-infected and HPV-negative cells. The inactivation of the transcriptional activity of p53 was associated with an increased cellular proliferation and viability of HeLa cells. In conclusion, we demonstrate that p53 DBD Nbs positively affect protein stability whilst adversely affecting protein function, attesting to their ability to modulate protein properties in a very subtle manner.
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Affiliation(s)
- Anneleen Steels
- Department of Biomolecular Medicine, Faculty of Medicine and Health Sciences, Campus Rommelaere, A. Baertsoenkaai 3, Ghent University, Ghent, Belgium
| | - Laura Vannevel
- Department of Biomolecular Medicine, Faculty of Medicine and Health Sciences, Campus Rommelaere, A. Baertsoenkaai 3, Ghent University, Ghent, Belgium
| | - Olivier Zwaenepoel
- Department of Biomolecular Medicine, Faculty of Medicine and Health Sciences, Campus Rommelaere, A. Baertsoenkaai 3, Ghent University, Ghent, Belgium
| | - Jan Gettemans
- Department of Biomolecular Medicine, Faculty of Medicine and Health Sciences, Campus Rommelaere, A. Baertsoenkaai 3, Ghent University, Ghent, Belgium.
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Mwapagha LM, Tiffin N, Parker MI. Delineation of the HPV11E6 and HPV18E6 Pathways in Initiating Cellular Transformation. Front Oncol 2017; 7:258. [PMID: 29164058 PMCID: PMC5672010 DOI: 10.3389/fonc.2017.00258] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 10/13/2017] [Indexed: 12/16/2022] Open
Abstract
Although high-risk human papillomaviruses (HPVs) are the major risk factors for cervical cancer they have been associated with several other cancers, such as head and neck and oral cancers. Since integration of low-risk HPV11 DNA has been demonstrated in esophageal tumor genomes, this study compared the effects of low-risk HPV11E6 and high-risk HPV18E6 on cellular gene expression. The HPV11E6 and HPV18E6 genes were cloned into an adenoviral vector and expressed in human keratinocytes (HaCaT) in order to investigate early events and to eliminate possible artifacts introduced by selective survival of fast growing cells in stable transfection experiments. HPV11E6 had very little effect on p21 and p53 gene expression, while HPV18E6 resulted in a marked reduction in both these proteins. Both HPV11E6 and HPV18E6 enabled growth of colonies in soft agar, but the level of colony formation was higher in HPV18E6 infected cells. DNA microarray analysis identified significantly differentially regulated genes involved in the cellular transformation signaling pathways. These findings suggest that HPV11E6 and HPV18E6 are important in initiating cellular transformation via deregulation of signaling pathways such as PI3K/AKT and pathways that are directly involved in DNA damage repair, cell survival, and cell proliferation. This study shows that the low-risk HPV11E6 may have similar effects as the high-risk HPV18E6 during the initial stages of infection, but at a much reduced level.
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Affiliation(s)
- Lamech M. Mwapagha
- Faculty of Health Sciences, Division of Medical Biochemistry and Structural Biology, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
- International Centre for Genetic Engineering and Biotechnology, Cape Town Component, Cape Town, South Africa
| | - Nicki Tiffin
- Centre for Infectious Disease Epidemiology and Research, School of Public Health and Family Medicine, University of Cape Town, Cape Town, South Africa
| | - M. Iqbal Parker
- Faculty of Health Sciences, Division of Medical Biochemistry and Structural Biology, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
- International Centre for Genetic Engineering and Biotechnology, Cape Town Component, Cape Town, South Africa
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Prevalence of type-specific oncogenic human papillomavirus infection assessed by HPV E6/E7 mRNA among women with high-grade cervical lesions. Int J Infect Dis 2015; 37:135-42. [DOI: 10.1016/j.ijid.2015.06.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 06/24/2015] [Accepted: 06/24/2015] [Indexed: 01/16/2023] Open
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Wang HY, Park S, Kim S, Lee D, Kim G, Kim Y, Park KH, Lee H. Use of hTERT and HPV E6/E7 mRNA RT-qPCR TaqMan assays in combination for diagnosing high-grade cervical lesions and malignant tumors. Am J Clin Pathol 2015; 143:344-51. [PMID: 25696792 DOI: 10.1309/ajcpf2xgz2xiqyqx] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
OBJECTIVES Human papillomavirus (HPV) is a major cause of cervical cancer, which is the second most common cancer in women. HPV E6 initiates degradation of cellular tumor suppressor protein p53, induces human telomerase reverse transcriptase (hTERT) activity, and then leads to progressive cervical carcinogenesis. METHODS In this study, the CervicGen HPV RT-qDX assay (Optipharm, Osong, Republic of Korea), which detects 16 HPV high-risk subtypes (HPV 16, 18, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68, and 69), and the CervicGen hTERT RT-qDX assay (Optipharm) were evaluated using 545 ThinPrep (Hologic, Bedford, MA) Papanicolaou samples. RESULTS The positivity for the HPV E6/E7 messenger RNA (mRNA) assay was 94.4%, 95.2%, 82.4%, 46.5%, 25.0%, and 1.1% in squamous cell carcinomas, high-grade squamous intraepithelial lesions (HSILs), atypical squamous cells--cannot exclude HSIL, low-grade squamous intraepithelial lesions, atypical squamous cells of undetermined significance, and normal cytology samples, respectively. Five cervical intraepithelial neoplasia grade 2+ samples were not detected by the HPV E6/E7 mRNA assay, but they exhibited positive signals in the hTERT mRNA assay. Notably, the hTERT mRNA expression level was increased in high-grade cervical lesions but was very low in all 288 normal samples. CONCLUSIONS These data suggest that the combination of HPV E6/E7 and hTERT mRNA expression levels could be used in a complementary manner in diagnosing high-grade cervical lesions and malignant tumors and might be useful as a predictive marker in monitoring low-grade cervical lesions.
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Affiliation(s)
- Hye-Young Wang
- M&D, Wonju Eco Environmental Technology Center, Wonju, Gangwon, Republic of Korea
| | - Sunyoung Park
- Department of Biomedical Laboratory Science, College of Health Sciences, Yonsei University, Wonju, Gangwon, Republic of Korea
| | - Sunghyun Kim
- Department of Biomedical Laboratory Science, College of Health Sciences, Yonsei University, Wonju, Gangwon, Republic of Korea
- Institute for Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea
| | - Dongsup Lee
- Department of Biomedical Laboratory Science, College of Health Sciences, Yonsei University, Wonju, Gangwon, Republic of Korea
- Department of Clinical Laboratory Science, Hyejeon College, Hongseong, Chungnam, Republic of Korea
| | - Geehyuk Kim
- Department of Biomedical Laboratory Science, College of Health Sciences, Yonsei University, Wonju, Gangwon, Republic of Korea
| | - Yeun Kim
- Department of Biomedical Laboratory Science, College of Health Sciences, Yonsei University, Wonju, Gangwon, Republic of Korea
| | - Kwang Hwa Park
- Department of Pathology, Yonsei University Wonju College of Medicine, Wonju, Gangwon, Republic of Korea
| | - Hyeyoung Lee
- Department of Biomedical Laboratory Science, College of Health Sciences, Yonsei University, Wonju, Gangwon, Republic of Korea
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8
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Burroni E, Bisanzi S, Sani C, Puliti D, Carozzi F. Codon 72 polymorphism of p53 and HPV type 16 E6 variants as risk factors for patients with squamous epithelial lesion of the uterine cervix. J Med Virol 2012; 85:83-90. [PMID: 23124863 DOI: 10.1002/jmv.23417] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2012] [Indexed: 11/09/2022]
Abstract
The Arg/Arg genotype versus Arg/Pro or Pro/Pro at codon 72 of the p53 gene in association with human papillomavirus (HPV) 16 E6 variants has been implicated as a risk marker in cervical neoplasia. However, research on this topic has produced controversial results. The association of p53 codon 72 polymorphism alone and in combination with specific HPV 16 E6 variants with risk of developing squamous intraepithelial cervical lesion has been investigated in low and high-grade squamous intraepithelial lesions and in HPV-negative controls from an Italian population. The data obtained showed statistically significant different distribution of p53 genotypes between healthy controls and precursor lesions, with the p53 arginine homozygous increased in high-grade squamous intraepithelial lesions. The T350G HPV 16 variant was the most frequent variant observed in the analyzed group of Italian women, showing a slight decreasing with the severity of the lesion. At the same time, the number of the prototype T350 slightly increased with the severity of the cytological lesions. In conclusion, p53 arginine homozygous was found to be increased in high-grade lesions, supporting the results of previous investigations indicating that HPV-positive patients with p53 Arg/Arg have an increased risk of developing pre-cancerous lesions. In addition, T350G HPV 16 variant was over-represented in p53 Arg homozygous women with cervical lesions. When p53 genotype and HPV 16 variants are considered together, no difference emerges between cases and controls so is not possible to assess that the oncogenic effect of HPV 16 T350G variant may be influenced by the p53 genotype.
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Affiliation(s)
- E Burroni
- Unit of Analytical and Biomolecular Cytology, ISPO, Florence, Italy.
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9
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Kim DH, Jarvis RM, Allwood JW, Batman G, Moore RE, Marsden-Edwards E, Hampson L, Hampson IN, Goodacre R. Raman chemical mapping reveals site of action of HIV protease inhibitors in HPV16 E6 expressing cervical carcinoma cells. Anal Bioanal Chem 2010; 398:3051-61. [PMID: 20957472 DOI: 10.1007/s00216-010-4283-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 09/28/2010] [Accepted: 09/29/2010] [Indexed: 01/12/2023]
Abstract
It has been shown that the HIV protease inhibitors indinavir and lopinavir may have activity against the human papilloma virus (HPV) type 16 inhibiting HPV E6-mediated proteasomal degradation of p53 in cultured cervical carcinoma cells. However, their mode and site of action is unknown. HPV-negative C33A cervical carcinoma cells and the same cells stably transfected with E6 (C33AE6) were exposed to indinavir and lopinavir at concentrations of 1 mM and 30 μM, respectively. The intracellular distribution of metabolites and metabolic changes induced by these treatments were investigated by Raman microspectroscopic imaging combined with the analysis of cell fractionation products by liquid chromatography-mass spectrometry (LC-MS). A uniform cellular distribution of proteins was found in drug-treated cells irrespective of cell type. Indinavir was observed to co-localise with nucleic acid in the nucleus, but only in E6 expressing cells. Principal components analysis (PCA) score maps generated on the full Raman hypercube and the corresponding PCA loadings plots revealed that the majority of metabolic variations influenced by the drug exposure within the cells were associated with changes in nucleic acids. Analysis of cell fractionation products by LC-MS confirmed that the level of indinavir in nuclear extracts was approximately eight-fold greater than in the cytoplasm. These data demonstrate that indinavir undergoes enhanced nuclear accumulation in E6-expressing cells, which suggests that this is the most likely site of action for this compound against HPV.
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Affiliation(s)
- Dong-Hyun Kim
- School of Chemistry, Manchester Interdisciplinary Biocentre, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK
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10
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Kim DH, Jarvis RM, Xu Y, Oliver AW, Allwood JW, Hampson L, Hampson IN, Goodacre R. Combining metabolic fingerprinting and footprinting to understand the phenotypic response of HPV16 E6 expressing cervical carcinoma cells exposed to the HIV anti-viral drug lopinavir. Analyst 2010; 135:1235-44. [PMID: 20390218 DOI: 10.1039/b923046g] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Recently, it has been reported that the anti-viral drug, lopinavir, which is currently used as a human immunodeficiency virus (HIV) protease inhibitor, could also inhibit E6-mediated proteasomal degradation of mutant p53 in E6-transfected C33A cells. In this study, C33A parent control cells and HPV16 E6-transfected cells were exposed to lopinavir at concentrations ranging from 0 to 30 microM. The phenotypic response was assessed by Fourier transform infrared (FT-IR) spectroscopy directly on cells (the metabolic fingerprint) and on the cell growth medium (the metabolic footprint). Multivariate analysis of the data using both principal components analysis (PCA) and canonical variates analysis (PC-CVA) showed trends in scores plots that were related to the concentration of the drug. Inspection of the PC-CVA loadings vector revealed that the effect was not due to the drug alone and that several IR spectral regions including proteins, nucleotides and carbohydrates contributed to the separation in PC-CVA space. Finally, partial least squares regression (PLSR) could be used to predict the concentration of the drug accurately from the metabolic fingerprints and footprints, indicating a dose related phenotypic response. This study shows that the combination of metabolic fingerprinting and footprinting with appropriate chemometric analysis is a valuable approach for studying cellular responses to anti-viral drugs.
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Affiliation(s)
- Dong-Hyun Kim
- School of Chemistry, Manchester Interdisciplinary Biocentre, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
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Shackelford J, Pagano JS. Role of the ubiquitin system and tumor viruses in AIDS-related cancer. BMC BIOCHEMISTRY 2007; 8 Suppl 1:S8. [PMID: 18047745 PMCID: PMC2106372 DOI: 10.1186/1471-2091-8-s1-s8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Tumor viruses are linked to approximately 20% of human malignancies worldwide. This review focuses on examples of human oncogenic viruses that manipulate the ubiquitin system in a subset of viral malignancies; those associated with AIDS. The viruses include Kaposi's sarcoma herpesvirus, Epstein-Barr virus and human papilloma virus, which are causally linked to Kaposi's sarcoma, certain B-cell lymphomas and cervical cancer, respectively. We discuss the molecular mechanisms by which these viruses subvert the ubiquitin system and potential viral targets for anti-cancer therapy from the perspective of this system. Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; ).
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Affiliation(s)
- Julia Shackelford
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7295, USA.
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12
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Martinez I, Wang J, Hobson KF, Ferris RL, Khan SA. Identification of differentially expressed genes in HPV-positive and HPV-negative oropharyngeal squamous cell carcinomas. Eur J Cancer 2006; 43:415-32. [PMID: 17079134 PMCID: PMC1847595 DOI: 10.1016/j.ejca.2006.09.001] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2006] [Revised: 07/28/2006] [Accepted: 09/07/2006] [Indexed: 01/18/2023]
Abstract
Human papillomaviruses (HPVs) have been implicated in the pathogenesis of a subset of squamous cell carcinoma of the head and neck (SCCHN). The goal of this study was to compare the cellular gene expression profiles of HPV-positive and HPV-negative oropharyngeal carcinomas with those of the normal oral epithelium. Using Affymetrix Human U133A GeneChip, our results showed that 397 genes were differentially expressed in HPV-positive SCCHN compared to the normal oral epithelium. The upregulated genes included those involved in cell cycle regulation (CDKN2A), cell differentiation (SFRP4) and DNA repair (RAD51AP1), while the downregulated genes included those involved in proteolysis (PRSS3). We also found 162 differentially expressed genes in HPV-negative SCCHN compared to the normal oral mucosa. The upregulated genes included those involved in cell proliferation (AKR1C3) and transcription regulation (SNAPC1), while downregulated genes included those involved in apoptosis (CLU) and RNA processing (RBM3). Our studies also identified a subgroup of 59 differentially expressed genes in HPV-positive SCCHN as compared to both HPV-negative SCCHN and normal oral tissues. Such upregulated genes included those involved in nuclear structure and meiosis (SYCP2), DNA repair (RFC5), and transcription regulation (ZNF238). Genes involved in proteolysis (KLK8) and signal transduction (CRABP2) were found to be downregulated in HPV-positive SCCHN. The results of GeneChip experiments were validated by quantitative real-time RT-PCR analysis of a few representative genes. Our results reveal specific gene expression patterns in HPV-positive and HPV-negative oropharyngeal squamous carcinomas that may serve as potential biomarkers for the development of SCCHN.
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Affiliation(s)
- Ivan Martinez
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15208, USA
| | - Jun Wang
- Departments of Otolaryngology and Immunology, University of Pittsburgh Medical Center and Cancer Institute, Pittsburgh, PA, USA
| | - Kenosha F. Hobson
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15208, USA
| | - Robert L. Ferris
- Departments of Otolaryngology and Immunology, University of Pittsburgh Medical Center and Cancer Institute, Pittsburgh, PA, USA
- UPCI Resea4rch pavilion, The Hillman Cancer Center, Pittsburgh, PA, USA
| | - Saleem A. Khan
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15208, USA
- *Corresponding author. Tel.: +1 412 648 9025; fax: 1 412 624 1401. E-mail address:
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Xu GW, Mymryk JS, Cairncross JG. Pharmaceutical-mediated inactivation of p53 sensitizes U87MG glioma cells to BCNU and temozolomide. Int J Cancer 2005; 116:187-92. [PMID: 15800902 DOI: 10.1002/ijc.21071] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Pifithrin-alpha (PFTalpha) is a small molecule inhibitor of p53. By reversibly blocking apoptosis in response to DNA damage, PFTalpha protects normal cells from lethal doses of gamma-radiation (Komarov et al., Science, 1999;285:1733-7). We examined the effect of PFTalpha on the chemosensitivity of a human cancer in which cell cycle arrest, not apoptosis, is the principle cellular consequence of p53 activation. This was of interest because E6 silencing of p53 sensitizes U87MG astrocytic glioma cells to BCNU and temozolomide (TMZ), cytotoxic drugs that are modestly helpful in the treatment of aggressive astrocytic gliomas. We observed that exposure of U87MG cells to PFTalpha before cytotoxic chemotherapy attenuated p53-mediated induction of p21WAF1 protein levels, sensitizing U87MG cells to BCNU and TMZ. Sensitization of U87MG cells was associated with G1 arrest, delayed entry into S-phase and decreased repair of DNA damage by BCNU. Our findings suggest that in addition to protecting normal cells from the toxic effects of radiation and chemotherapy, small molecule inhibitors of p53, like PFTalpha, might play a role in clinical oncology by sensitizing certain resistant cancers to cytotoxic chemotherapies.
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Affiliation(s)
- G Wei Xu
- Department of Oncology, University of Western Ontario, London, Ontario
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14
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Zhang B, Srirangam A, Potter DA, Roman A. HPV16 E5 protein disrupts the c-Cbl-EGFR interaction and EGFR ubiquitination in human foreskin keratinocytes. Oncogene 2005; 24:2585-8. [PMID: 15735736 PMCID: PMC2730517 DOI: 10.1038/sj.onc.1208453] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The E5 protein of human papillomavirus type 16 (HPV16) is a small hydrophobic protein, which localizes to the cell membrane, Golgi apparatus and endosomes. HPV16 E5 enhances the activation of the epidermal growth factor (EGFR). The activated EGFR is downregulated through the endocytic pathway, where E5 has been shown to inhibit endosomal acidification and trafficking. Ubiquitination of the activated EGFR plays a role in this downregulation. c-Cbl is a ubiquitin ligase that associates with the activated EGFR and targets it for degradation. Since E5 has been shown to form a complex with the EGFR, we tested the hypothesis that E5 affects the interaction of c-Cbl with the EGFR. We found a significant decrease of c-Cbl bound to the EGFR and of ubiquitinated EGFR in the presence of E5. E5 did not affect c-Cbl steady-state level, phosphorylation or translocation to the membrane. This novel result suggests that HPV16 E5 may, at least in part, upregulate EGFR-mediated signal transduction by inhibiting the interaction of c-Cbl with the EGFR, thereby decreasing c-Cbl-mediated degradation of the EGFR.
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Affiliation(s)
- Benyue Zhang
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA
- The Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN, USA
- Walther Cancer Institute, Indianapolis, IN, USA
| | - Anjaiah Srirangam
- Departments of Medicine and Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
- The Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN, USA
- Walther Cancer Institute, Indianapolis, IN, USA
| | - David A Potter
- Departments of Medicine and Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
- The Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN, USA
- Walther Cancer Institute, Indianapolis, IN, USA
| | - Ann Roman
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA
- The Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN, USA
- Walther Cancer Institute, Indianapolis, IN, USA
- Correspondence: A Roman, Department of Microbiology and Immunology, Indiana University School of Medicine, 635 Barnhill Drive, Medical Sciences Building, Room 420, Indianapolis, IN 46202-5120, USA; E-mail:
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15
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Singh A, Sharma H, Salhan S, Gupta SD, Bhatla N, Jain SK, Singh N. Evaluation of expression of apoptosis-related proteins and their correlation with HPV, telomerase activity, and apoptotic index in cervical cancer. Pathobiology 2005; 71:314-22. [PMID: 15627842 DOI: 10.1159/000081727] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2004] [Accepted: 06/04/2004] [Indexed: 01/05/2023] Open
Abstract
OBJECTIVE The aim of this study was to examine the expression of apoptosis-related proteins in cervical cancer, and investigate their correlation with the apoptotic index (AI), telomerase activity, human papilloma virus (HPV) infection and clinicopathological characteristics. METHODS Fifty cervical cancer samples and 20 normal cervical tissues were assessed for the protein expression of survivin, Bcl-2, Cox-2, p53 and p73 by immunohistochemistry. HPV DNA was detected by PCR, telomerase activity by PCR-ELISA, and AI by TUNEL assay. RESULTS 46/50 cervical tumors (92%) showed an increased telomerase activity as compared to 3/20 (15%) controls. 45/50 (90%) cervical tumors were positive for HPV, of which 30 were HPV-16 positive and 5 were HPV-18 positive. 24/50 (48%) tumors were positive for survivin, 14 (28%) for Bcl-2, 13 (26%) for Cox-2, 19/45 (42%) for p73, 10/45 (24%) for p53. Telomerase activity was highest in tumors with the poorest grade. A positive correlation was seen between survivin and Bcl-2, survivin and tumor stage, Bcl-2 and Cox-2, p73 and p53 and p73 and the AI. Despite the overexpression of various antiapoptotic proteins, no significant difference was observed in the AI between tumors and controls. CONCLUSIONS Since deregulation of the apoptotic pathway appears to occur in cervical cancer, some apoptosis-related proteins could be assessed as potential markers for progression/prognosis in cervical cancer. Additionally, newer proteins such as p73 may play a compensatory role for the nonfunctional proteins such as p53.
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Affiliation(s)
- A Singh
- Department of Biochemistry, All India Institute of Medical Sciences, New Delhi-110029, India
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16
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Farhadi M, Tahmasebi Z, Merat S, Kamangar F, Nasrollahzadeh D, Malekzadeh R. Human papillomavirus in squamous cell carcinoma of esophagus in a high-risk population. World J Gastroenterol 2005; 11:1200-3. [PMID: 15754405 PMCID: PMC4250714 DOI: 10.3748/wjg.v11.i8.1200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the relation of human papillomavirus (HPV) and esophageal squamous cell carcinoma (ESCC) in Iranian patients as compared to normal controls.
METHODS: Using MY09/MY11 consensus primers, we compared the prevalence of a HPV L1 gene in tumor tissues from 38 ESCC cases and biopsied tissues from 38 endoscopically normal Iranian individuals. We also compared the presence of HPV16 and HPV18 in the same samples using type-specific E6/E7 primers.
RESULTS: Fourteen (36.8%) of the 38 ESCC samples but only 5 (13.2%) of the 38 control samples were positive for the HPV L1 gene (P = 0.02). Five (13.2%) of the ESCC samples but none of the control samples were positive for the HPV16 E6/E7 gene (P = 0.05). Three (7.9%) of the ESCC samples and 5 (13.2%) of the control samples were positive for the HPV18 E6/E7 gene (P = 0.71).
CONCLUSION: Our data are consistent with HPV DNA studies conducted in other high-risk areas for ESCC. HPV should be considered as a potential factor contributing to the high incidence of ESCC in Iran and other high-incidence areas of the world.
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Affiliation(s)
- Mohammad Farhadi
- Digestive Disease Research Center, Shariati Hospital, North Kargar Avenue, Tehran 14114, Iran
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17
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Grm HS, Banks L. Hpv Proteins as Targets for Therapeutic Intervention. Antivir Ther 2004. [DOI: 10.1177/135965350400900518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Human papillomaviruses (HPV) are the aetiological agents of several types of anogenital tumours, particularly cervical carcinoma. Recent evidence also suggests a role for HPV in the development of squamous cell carcinomas of the skin, especially in immunocompromised individuals. HPV infection also produces a number of non-malignant, but nonetheless cosmetically unpleasant lesions. Therefore, any effective therapeutic treatment for HPV-induced diseases would be extremely beneficial both on humanitarian grounds as well as being economically very attractive. In this review, we will discuss the functions of the viral proteins that appear to be the most appropriate for the development of therapeutics aimed at the treatment of viral infection and virus-induced cancers.
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Affiliation(s)
| | - Lawrence Banks
- International Centre for Genetic Engineering and Biotechnology, Trieste, Italy
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18
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Wilson CM, Tobin S, Young RC. The exploding worldwide cancer burden: the impact of cancer on women. Int J Gynecol Cancer 2004; 14:1-11. [PMID: 14764024 DOI: 10.1111/j.1048-891x.2004.14178.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Although age-adjusted cancer death rates have started to decline in the United States and other developed nations - thanks in large part to widespread screening programs that detect cancers at early, treatable stages - cancer in developing countries is on the rise. Ironically, rising life expectancy in those nations along with the adoption of 'Western' lifestyles will leave many more people vulnerable to cancer. Unfortunately, the early detection tools and treatment technology that have helped control cancer in wealthier lands are often not readily available in many other countries. Much of this increased cancer burden will take the form of cancers that affect women - not only breast, cervical, and other gynecologic cancers but colorectal cancer, lung cancer, and other malignancies related to tobacco. Physicians specializing in cancer care for women need to be alert to every opportunity to improve cancer screening and prevention among the growing, aging populations of less-developed countries. Less precise but less costly and more widely available screening techniques may save thousands more lives than the most sophisticated technology because low-cost programs can be applied widely instead of being reserved for a fortunate few. In addition, education and prevention efforts directed toward tobacco use need to be put in place to help stem an epidemic of tobacco-related cancers that has largely peaked in developed countries but looms ominously in the future of developing nations.
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Affiliation(s)
- C M Wilson
- Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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19
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Oh ST, Longworth MS, Laimins LA. Roles of the E6 and E7 proteins in the life cycle of low-risk human papillomavirus type 11. J Virol 2004; 78:2620-6. [PMID: 14963169 PMCID: PMC369251 DOI: 10.1128/jvi.78.5.2620-2626.2004] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many important functions have been attributed to the high-risk human papillomavirus (HPV) E6 and E7 proteins, including binding and degradation of p53 as well as interacting with Rb proteins. In contrast, the physiological roles of the low-risk E6 and E7 proteins remain unclear. Previous studies demonstrated that the high-risk E6 and E7 proteins also play roles in the productive life cycle by facilitating the maintenance of viral episomes (J. T. Thomas, W. G. Hubert, M. N. Ruesch, and L. A. Laimins, Proc. Natl. Acad. Sci. USA 96:8449-8454, 1999). In order to determine whether low-risk E6 or E7 is similarly necessary for the stable maintenance of episomes, HPV type 11 (HPV-11) genomes that contained translation termination mutations in E6 or E7 were constructed. Upon transfection into normal human keratinocytes, genomes in which E6 function was abolished were unable to be maintained episomally. Transfection of genomes containing substitution mutations in amino acids conserved in high- and low-risk HPV types suggested that multiple protein domains are involved in this process. Examination of cells transfected with HPV-11 genomes in which E7 function was inhibited were found to exhibit a more complex phenotype. At the second passage following transfection, mutant genomes were maintained as episomes but at significantly reduced levels than in cells transfected with the wild-type HPV-11 genome. Upon further passage in culture, however, the episomal forms of these E7 mutant genomes quickly disappeared. These findings identify important new functions for the low-risk E6 and E7 proteins in the episomal maintenance of low-risk HPV-11 genomes and suggest that they may act in a manner similar to that observed for the high-risk proteins.
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Affiliation(s)
- Stephen T Oh
- Department of Microbiology-Immunology, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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20
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Ledwaba T, Dlamini Z, Naicker S, Bhoola K. Molecular genetics of human cervical cancer: role of papillomavirus and the apoptotic cascade. Biol Chem 2004; 385:671-82. [PMID: 15449703 DOI: 10.1515/bc.2004.083] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Cervical cancer is rated the second most common malignant tumour globally, and is aetiologically linked to human papillomavirus (HPV) infection. Here the cellular pathology under consideration of stem/progenitor cell carcinogenesis is reviewed. Of the three causative molecular mechanisms of cervical cancer, two are associated with HPV: firstly, the effect of the viral oncogenes, E6 and E7; and secondly, integration of the viral DNA into chromosomal regions of tumour phenotype. The third process involved is the repetitive loss of heterozygosity in some chromosomal regions. HPV can be classified into high- and low-risk types; the high-risk types encode two oncoproteins, E6 and E7, which interact with tumour suppressor proteins. The association results in the inactivation of tumour suppressor proteins and the abrogation of apoptosis. Apoptosis is referred to as programmed cell death, whereby a cell deliberately commits suicide, and thus regulates cell numbers during development and maintenance of cellular homeostasis. This review attempts to elucidate the role of apoptotic genes, and considers external factors that interact with HPV in the development and progression of cervical cancer. Therefore, an in-depth understanding of the apoptotic genes that control molecular mechanisms in cervical cancer are of critical importance. Useful targets for therapeutic strategies would be those that alter apoptotic pathways in a manner where the escape of HPV from surveillance by the host immune system is prevented. Such an approach directed at the apoptotic genes maybe useful in the treatment of cervical cancer.
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Affiliation(s)
- Thokozile Ledwaba
- School of Molecular and Cell Biology, Medical Faculty, University of the Witwatersrand, P/Bag 3, Johannesburg 2050, Republic of South Africa
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21
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Bradford CR, Zhu S, Ogawa H, Ogawa T, Ubell M, Narayan A, Johnson G, Wolf GT, Fisher SG, Carey TE. P53 mutation correlates with cisplatin sensitivity in head and neck squamous cell carcinoma lines. Head Neck 2003; 25:654-61. [PMID: 12884349 DOI: 10.1002/hed.10274] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND A critical factor for successful organ preservation treatment in head and neck cancer may be selecting tumors that respond to chemotherapy and radiation. Previous results in patients indicated that tumors that overexpressed p53 were more sensitive to chemotherapy than those that did not overexpress p53. METHODS To determine the relationship of p53 mutations to sensitivity to cisplatin in vitro, 23 head and neck squamous cell carcinoma (HNSCC) cell lines were analyzed for cisplatin sensitivity, p53 expression, and p53 mutation status. RESULTS Mutations of the p53 gene were identified in 13 of 23 of the cell lines tested. Mutation of the p53 gene was significantly associated with high levels of expression of the p53 protein. The average ID(50) (drug dose required to inhibit 50% of cell growth) for cell lines with mutant p53 was 6.8 microM, whereas the average ID(50) for cell lines with wild-type p53 was 13.7 microM. CONCLUSIONS These in vitro data support a role for mutation of the p53 tumor suppressor gene as a marker for response to cisplatin in HNSCC.
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Affiliation(s)
- Carol R Bradford
- Department of Otolaryngology-Head and Neck Surgery, 1904 Taubman Center, University of Michigan, Ann Arbor, Michigan 48109-0312, USA.
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22
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Taylor ER, Boner W, Dornan ES, Corr EM, Morgan IM. UVB irradiation reduces the half-life and transactivation potential of the human papillomavirus 16 E2 protein. Oncogene 2003; 22:4469-77. [PMID: 12881703 DOI: 10.1038/sj.onc.1206746] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Human papillomaviruses (HPV) are causative agents of human cancers including those of the cervix and also of the head and neck; HPV16 is the most commonly found type in these diseases. The viral E2 protein regulates transcription from the viral genome by interacting with DNA-binding sequences in the HPV transcriptional control region; it also regulates replication by interacting with and recruiting the HPV replication factor E1 to the viral origin. Therefore, E2 is essential for the viral life cycle. The E2 protein interacts with several proteins involved in the cellular response to DNA damage including p53, TopBP1, and PARP. We therefore set out to establish whether DNA-damaging agents can regulate E2 activity. Here we show that UVB irradiation downregulates transcriptional activity of both HPV16 and HPV8 E2, while hydroxyurea and etoposide do not. This downregulation of E2 activity is independent of p53 function as it occurs in p53 wild type and null cell types as well as in the presence of functional HPV16 E6 that degrades p53. Using stable cell lines expressing E2 we show that this downregulation of E2 function by UVB is due to a reduction of the E2 protein half-life. The identification of the pathway(s) through which UVB downregulates E2 transcriptional activity and protein levels will present a novel target for the treatment of HPV-related diseases.
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Affiliation(s)
- Ewan R Taylor
- Department of Veterinary Pathology, Institute of Comparative Medicine, University of Glasgow, Garscube Estate, Bearsden Road, Glasgow G61 1QH, Scotland, UK
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23
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Plug-Demaggio AW, McDougall JK. The human papillomavirus type 16 E6 oncogene induces premature mitotic chromosome segregation. Oncogene 2002; 21:7507-13. [PMID: 12386813 DOI: 10.1038/sj.onc.1205903] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2002] [Revised: 07/12/2002] [Accepted: 07/18/2002] [Indexed: 11/09/2022]
Abstract
Expression of the human papillomavirus type 16 E6 and E7 oncogenes initiates and maintains abnormal cell replication, by interacting with the p53 and retinoblastoma (Rb) gene products. Subsequent changes in host cell gene expression, as a consequence of genetic instability, can result in progression to invasive carcinoma. In addition to previously described effects of these viral oncogenes on centrosome synthesis, primarily associated with the expression of E7, the results described herein demonstrate that the E6 oncogene can induce premature chromosome segregation in human cells.
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Affiliation(s)
- Annemieke W Plug-Demaggio
- Department of Pathology, University of Washington, 1959 Pacific Street, N.E., Seattle, Washington, WA 98195-7407, USA
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24
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Havard L, Delvenne P, Fraré P, Boniver J, Giannini SL. Differential production of cytokines and activation of NF-kappaB in HPV-transformed keratinocytes. Virology 2002; 298:271-85. [PMID: 12127790 DOI: 10.1006/viro.2002.1468] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We have proposed that chronic infection of keratinocytes by HPV modifies the expression of potentially important cytokines by interfering with the NF-kappaB signal pathway. We evaluated the constitutive and IL-1beta-induced expression of GM-CSF and TNF-alpha and the expression/activity of NF-kappaB in HPV+ and HPV- cell lines. Despite the enhanced expression of the functional components of the NF-kappaB signaling pathway in HPV+ cell lines by a mechanism implicating the HPV oncoprotein E6, the constitutive activity of NF-kappaB and the expression of GM-CSF/TNF-alpha were significantly reduced relative to the HPV- cell line and normal keratinocytes. In contrast, we observed a superactivation of NF-kappaB activity after IL-1beta stimulation, a strong and transient induction of GM-CSF/TNF-alpha mRNA, but undetectable levels of secreted proteins in HPV+ cell lines. Our data demonstrate that E6 modulates the NF-kappaB signaling pathway and suggest that other HPV proteins also interfere with GM-CSF/TNF-alpha expression by transcriptional and/or posttranscriptional mechanisms.
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Affiliation(s)
- L Havard
- Department of Pathology, University Hospital of Liège, Liège, Belgium.
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25
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Abstract
The tumor suppressor protein, p53, is often referred to as the guardian of the genome. When p53 function is impaired, its ability to preserve genomic integrity is compromised. This may result in an increase in mutation on both a molecular and chromosomal level and contribute to the progression to a malignant phenotype. In order to study the effect of p53 function on the acquisition of mutation, in vitro and in vivo models have been developed in which both the frequency and mechanism of mutation can be analyzed. In human lymphoblastoid cells in which p53 function was impaired, both the spontaneous and induced mutant frequency increased at the autosomal thymidine kinase (TK) locus. The mutant frequency increased to a greater extent in cell lines in which p53 harbored a point mutation than in those lines in which a "null" mutation had been introduced by molecular targeting or by viral degradation indicating a possible "gain-of-function" associated with the mutant protein. Further, molecular analysis revealed that the loss of p53 function was associated with a greater tendency towards loss-of-heterozygosity (LOH) within the TK gene that was due to non-homologous recombination than that found in wild-type cells. Most data obtained from the in vivo models uses the LacI reporter gene that does not efficiently detect mutation that results in LOH. However, studies that have examined the effect of p53 status on mutation in the adenine phosphoribosyl transferase (APRT) gene in transgenic mice also suggest that loss of p53 function results in an increase in mutation resulting from non-homologous recombination. The results of these studies provide clear and convincing evidence that p53 plays a role in modulating the mutant frequency and the mechanism of mutation. In addition, the types of mutation that occur within the p53 gene are also of importance in determining the mutant frequency and the pathways leading to mutation.
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Affiliation(s)
- Suzanne M Morris
- Division of Genetic and Reproductive Toxicology, National Center for Toxicological Research, 3900 NCTR Road, Jefferson, AR 72079, USA.
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26
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Evans M, Borysiewicz LK, Evans AS, Rowe M, Jones M, Gileadi U, Cerundolo V, Man S. Antigen processing defects in cervical carcinomas limit the presentation of a CTL epitope from human papillomavirus 16 E6. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 167:5420-8. [PMID: 11673561 DOI: 10.4049/jimmunol.167.9.5420] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Human papillomavirus (HPV) infection, particularly type 16, is causally associated with the development of cervical cancer. The E6 and E7 proteins of HPV are constitutively expressed in cervical carcinoma cells making them attractive targets for CTL-based immunotherapy. However, few studies have addressed whether cervical carcinomas can process and present HPV E6/E7-derived Ags for recognition by CTL. We generated HLA-A*0201-restricted CTL clones against HPV16 E6(29-38) that recognized HPV16 E6 Ags transfected into B lymphoblastoid cells. These CTL were unable to recognize HLA-A*0201(+) HPV16 E6(+) cervical carcinoma cell lines even when the level of endogenous HPV16 E6 in these cells was increased by transfection. This defect in presentation of HPV16 E6(29-38) correlated with low level expression of HLA class I, proteasome subunits low molecular mass protein 2 and 7, and the transporter proteins TAP1 and TAP2 in the cervical carcinoma cell lines. The expression of all of these proteins could be up-regulated by IFN-gamma, but this was insufficient for CTL recognition unless the level of HPV16 E6 Ag was also increased by transfection. CTL recognition of the HPV16 E6(29-38) epitope in 721.174 B cells was dependent on TAP expression but independent of immunoproteasome expression. Collectively, these findings suggest that presentation of the HPV16 E6(29-38) epitope in cervical carcinoma cell lines is limited both by the level of TAP expression and by the low level or availability of the source HPV E6 oncoprotein. These observations place constraints on the use of this, and potentially other, HPV-derived CTL epitopes for the immunotherapy of cervical cancer.
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Affiliation(s)
- M Evans
- Department of Medicine, University of Wales College of Medicine, University Hospital of Wales, Heath Park, Cardiff, United Kingdom
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27
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Oh ST, Kyo S, Laimins LA. Telomerase activation by human papillomavirus type 16 E6 protein: induction of human telomerase reverse transcriptase expression through Myc and GC-rich Sp1 binding sites. J Virol 2001; 75:5559-66. [PMID: 11356963 PMCID: PMC114268 DOI: 10.1128/jvi.75.12.5559-5566.2001] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
High-risk human papillomaviruses (HPVs) immortalize keratinocytes by disrupting the retinoblastoma protein (Rb)/p16 pathway and activating telomerase. The E7 oncoprotein targets Rb, while the E6 oncoprotein induces telomerase activity in human keratinocytes. This study has examined the mechanism by which E6 activates telomerase. Expression of human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase, was found to be increased in keratinocytes stably expressing HPV type 16 E6, suggesting that E6 acts to increase hTERT transcription. hTERT expression and telomerase activity were activated to significantly higher levels in cells expressing both E6 and E7 than in cells expressing E6 alone. This indicates that E7 may augment E6-mediated activation of hTERT transcription. In transient-transfection assays using hTERT reporters, the induction of hTERT expression by E6 was found to be mediated by a 258-bp fragment of the hTERT promoter, proximal to the ATG initiation codon. Previous studies have demonstrated that overexpression of Myc can activate hTERT expression, suggesting that Myc may be a mediator of E6-mediated hTERT induction. However, in cells stably expressing E6, no strict correlation between the level of Myc and the activation of hTERT was found. Consistent with this observation, mutation of the two Myc binding sites in the hTERT promoter only modestly reduced responsiveness to E6 in transient reporter assays. This indicates that activation of Myc-dependent transcription is not essential for E6-mediated upregulation of hTERT expression. The hTERT promoter also contains five GC-rich elements that can bind Sp1. Mutation of these sites within the 258-bp fragment partially reduced hTERT induction by E6. However, when mutations in the Sp1 sites were combined with the mutated Myc binding sites, all activation by E6 was lost. This indicates that it is the combinatorial binding of factors to Myc and Sp1 cis elements that is responsible for hTERT induction by E6.
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Affiliation(s)
- S T Oh
- Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois 60611, USA
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28
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Parisien JP, Lau JF, Rodriguez JJ, Sullivan BM, Moscona A, Parks GD, Lamb RA, Horvath CM. The V protein of human parainfluenza virus 2 antagonizes type I interferon responses by destabilizing signal transducer and activator of transcription 2. Virology 2001; 283:230-9. [PMID: 11336548 DOI: 10.1006/viro.2001.0856] [Citation(s) in RCA: 196] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Type I interferon (IFN) induces antiviral responses through the activation of the ISGF3 transcription factor complex that contains the subunit proteins STAT1, STAT2, and p48/ISGF3 gamma/IRF9. The ability of some human paramyxoviruses to overcome IFN actions by specific proteolysis of STAT proteins has been examined. Infection of cells with type 2, but not type 1 or type 3 human parainfluenza virus (HPIV) leads to a loss of cellular STAT2 protein. Expression of a single HPIV2 protein derived from the V open reading frame blocks IFN-dependent transcriptional responses in the absence of other viral proteins. The loss of IFN response is due to V-protein-induced proteolytic degradation of STAT2. Expression of HPIV2 V causes the normally stable STAT2 protein to be rapidly degraded, and this proteolytic activity can be partially alleviated by proteasome inhibition. No V-protein-specific effects on STAT2 mRNA levels were observed. The results indicate that the V protein of HPIV2 is sufficient to recognize and target a specific cellular transcription factor for destruction by cellular machinery.
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Affiliation(s)
- J P Parisien
- Immunobiology Center, Mount Sinai School of Medicine, New York, New York 10029, USA
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29
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Stancheva I, Hensey C, Meehan RR. Loss of the maintenance methyltransferase, xDnmt1, induces apoptosis in Xenopus embryos. EMBO J 2001; 20:1963-73. [PMID: 11296229 PMCID: PMC125419 DOI: 10.1093/emboj/20.8.1963] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
DNA methylation is necessary for normal embryogenesis in animals. Here we show that loss of the maintenance methyltransferase, xDnmt1p, triggers an apoptotic response during Xenopus development, which accounts for the loss of specific cell populations in hypomethylated embryos. Hypomethylation-induced apoptosis is accompanied by a stabilization in xp53 protein levels after the mid-blastula transition. Ectopic expression of HPV-E6, which promotes xp53 degradation, prevents cell death, implying that the apoptotic signal is mediated by xp53. In addition, inhibition of caspase activation by overexpression of Bcl-2 results in the development of cellular masses that resemble embryonic blastomas. Embryonic tissue explant experiments suggest that hypomethylation alters the developmental potential of early embryo cells and that apoptosis is triggered by differentiation. Our results imply that loss of DNA methylation in differentiated somatic cells provides a signal via p53 that activates cell death pathways.
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Affiliation(s)
| | - Carmel Hensey
- Genes and Development Group, The University of Edinburgh, Department of Biomedical Sciences, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK and
Conway Institute of Biomolecular and Biomedical Research, Department of Pharmacology, University College Dublin, Belfield, Dublin 4, Ireland Corresponding author e-mail:
| | - Richard R. Meehan
- Genes and Development Group, The University of Edinburgh, Department of Biomedical Sciences, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK and
Conway Institute of Biomolecular and Biomedical Research, Department of Pharmacology, University College Dublin, Belfield, Dublin 4, Ireland Corresponding author e-mail:
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