The interaction between p53 and papillomaviruses

Borysiewicz

The Journal of Immunology

et al. 2001

101

114

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 E629–38 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 E629–38 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-γ, but this was insufficient for CTL recognition unless the level of HPV16 E6 Ag was also increased by transfection. CTL recognition of the HPV16 E629–38 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 E629–38 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.

Section: Discussionmentioning

confidence: 99%

“…Recently additional host cell proteins have been shown to bind to E6 (reviewed in Ref. 54). All of these factors could act to reduce the availability of E6 for degradation.…”

Section: Discussionmentioning

confidence: 99%

Antigen Processing Defects in Cervical Carcinomas Limit the Presentation of a CTL Epitope from Human Papillomavirus 16 E6

Borysiewicz

The Journal of Immunology

et al. 2001

101

114

European Journal of Cancer

“…Twenty micrograms of total RNA from each sample were used to generate double-stranded (ds) cDNA using the Superscript II Choice system (GIBCO-BRL, Rockville, MD). First-strand synthesis was carried out using a T7-(dT) 24 primer (Sigma-GenoSys, The Woodlands, TX) and Superscript II reverse transcriptase. This primer includes the promoter sequence for the T7 RNA polymerase.…”

Section: Crna Synthesis and Microarray Analysismentioning

confidence: 99%

Identification of differentially expressed genes in HPV-positive and HPV-negative oropharyngeal squamous cell carcinomas

Martínez

Wang

Hobson

et al. 2007

174

138

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 up-regulated genes included those involved in cell cycle regulation (CDKN2A), cell differentiation (SFRP4) and DNA repair (RAD51AP1), while the down-regulated genes included those involved in proteolysis (PRSS3). We also found 162 differentially expressed genes in HPVnegative SCCHN compared to the normal oral mucosa. The up-regulated 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 up-regulated 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 down-regulated 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. Novelty and impact of the paper: Using a 22,200 human transcript oligonucleotide microarray platform, we have examined the gene expression profiles in HPV-positive and HPV-negative oropharyngeal squamous cell carcinomas as compared to the normal oropharyngeal mucosa. Our study has identified several new genes whose expression is specifically associated with the presence of HPV-16 in the oropharyngeal squamous mucosa. Furthermore, we have identified several genes whose expression is altered in HPVnegative SCCHN as compared to the normal oral mucosa. Results of our study could contribute to the understanding of pathogenic mechanisms involved in the development of HPV-positive and HPV-negative oropharyngeal cancers and consequently in the identification of potential biomarkers associated with these two subtypes of squamous cell carcinomas.

“…The low-risk E7 proteins have also been shown to bind to Rb but with a 10-fold-lower affinity (15). One of the primary activities of the high-risk forms of E6 is to target p53 for degradation (32,43,53), which is mediated by complex formation with the cellular ubiquitin ligase E6-AP (19,20,28,41,42). Although degradation of p53 by E6 is specific to highrisk HPV types, some evidence suggests that low-risk forms of E6 may be able to bind to p53 with a low affinity (2,30,53).…”

mentioning

confidence: 99%

Roles of the E6 and E7 Proteins in the Life Cycle of Low-Risk Human Papillomavirus Type 11

Longworth

Laimins

2004

J Virol

Many important functions have been attributed to the high-risk human papillomavirus (HPV) E6 and E7proteins, 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.