Canine Papillomavirus 2 E6 Does Not Interfere With UVB-Induced Upregulation of p53 and p53-Regulated Genes
Ontology highlight
ABSTRACT:
SUBMITTER: Quinlan S
PROVIDER: S-EPMC7965962 | biostudies-literature | 2021 Jan
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:PURPOSE:Human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC) carries a distinct clinical behaviour. c-Met oncogene is an important driver for tumour progression and its relationship with HPV in OPSCC was explored in the present study. EXPERIMENTAL DESIGN:Knockdown of HPV oncogene E6 or p53 alone and in combination was performed to examine their effects on c-Met expression by Western blot and quantitative real-time polymerase chain reaction. The effects of c-Met inhibition on cell proliferation, migration, and colony formation were examined in HPV-positive head and neck squamous cell carcinoma (HNSCC) cells. Retrospectively collected OPSCC patient specimens (N = 78) were stained for c-Met by immunohistochemistry and the staining levels were correlated with HPV status and patient outcomes. RESULTS:E6 knockdown decreased c-Met protein and mRNA expression in HPV-positive HNSCC cells, which was partially abolished by the elimination of p53. Reducing c-Met decreased cell proliferation, migration, and colony formation in HPV-positive HNSCC cells. In OPSCC patient samples, high c-Met expression was associated with HPV-positive status (OR = 4.11, 95%CI: 1.16-14.55, P = 0.028) and tumour stage (OR = 0.27, 95%CI: 0.08-0.93, P = 0.039) by multivariable analysis. In T3/T4 stage patients, high c-Met expression was associated with HPV positivity and low p53 levels, supporting an axis of E6-p53-c-Met regulation. Furthermore, high c-Met expression was marginally associated with poor disease-free survival in HPV-positive patients. CONCLUSIONS:Our results suggest that c-Met may serve as a novel target for treating HPV-associated OPSCC. The data also demonstrate that HPV E6 upregulates c-Met expression partially through p53 downregulation.
| S-EPMC5002257 | biostudies-literature
Project description:The high-risk subtype human papillomaviruses (hrHPVs) infect and oncogenically transform basal epidermal stem cells associated with the development of squamous-cell epithelial cancers. The viral E6 oncoprotein destabilizes the p53 tumor suppressor, inhibits p53 K120-acetylation by the Tat-interacting protein of 60 kDa (TIP60, or Kat5), and prevents p53-dependent apoptosis. Intriguingly, the p53 gene is infrequently mutated in HPV + cervical cancer clinical isolates which suggests a possible paradoxical role for this gatekeeper in viral carcinogenesis. Here, we demonstrate that E6 activates the TP53-induced glycolysis and apoptosis regulator (TIGAR) and protects cells against oncogene-induced oxidative genotoxicity. The E6 oncoprotein induces a Warburg-like stress response and activates PI3K/PI5P4K/AKT-signaling that phosphorylates the TIGAR on serine residues and induces its hypoxia-independent mitochondrial targeting in hrHPV-transformed cells. Primary HPV + cervical cancer tissues contain high levels of TIGAR, p53, and c-Myc and our xenograft studies have further shown that lentiviral-siRNA-knockdown of TIGAR expression inhibits hrHPV-induced tumorigenesis in vivo. These findings suggest the modulation of p53 pro-survival signals and the antioxidant functions of TIGAR could have key ancillary roles during HPV carcinogenesis.
| S-EPMC10527176 | biostudies-literature
Project description:The genus beta human papillomaviruses (beta HPVs) cause cutaneous lesions and are thought to be involved in the initiation of some nonmelanoma skin cancers (NMSCs), particularly in patients with the genetic disorder epidermodysplasia verruciformis (EV). We have previously reported that at least two of the genus beta HPV E6 proteins bind to and/or increase the steady-state levels of p53 in squamous epithelial cells. This is in contrast to a well-characterized ability of the E6 proteins of cancer-associated HPVs of genus alpha HPV, which inactivate p53 by targeting its ubiquitin-mediated proteolysis. In this study, we have investigated the ability of genus beta E6 proteins from eight different HPV types to block the transactivation of p53 target genes following DNA damage. We find that the E6 proteins from diverse beta HPV species and types vary in their capacity to block the induction of MDM2, p21, and proapoptotic genes after genotoxic stress. We conclude that some genus beta HPV E6 proteins inhibit at least some p53 target genes, although perhaps not by the same mechanism or to the same degree as the high-risk genus alpha HPV E6 proteins.This study addresses the ability of various human papillomavirus E6 proteins to block the activation of p53-responsive cellular genes following DNA damage in human keratinocytes, the normal host cell for HPVs. The E6 proteins encoded by the high-risk, cancer-associated HPV types of genus alpha HPV have a well-established activity to target p53 degradation and thereby inhibit the response to DNA damage. In this study, we have investigated the ability of genus beta HPV E6 proteins from eight different HPV types to block the ability of p53 to transactivate downstream genes following DNA damage. We find that some, but not all, genus beta HPV E6 proteins can block the transactivation of some p53 target genes. This differential response to DNA damage furthers the understanding of cutaneous HPV biology and may help to explain the potential connection between some beta HPVs and cancer.
| S-EPMC4135955 | biostudies-literature
Project description:Cutaneous papillomaviruses can cause severe, persistent infections and skin cancer in immunodeficient patients, including people with X-linked severe combined immunodeficiency (XSCID). A similar phenotype is observed in a canine model of XSCID; these dogs acquire severe cutaneous papillomavirus infections that can progress to cancer in association with canine papillomavirus type 2 (CPV2). This canine model system provides a natural spontaneous animal model for investigation of papillomavirus infections in immunodeficient patients. Currently, it is unknown if CPV2 can subvert the innate immune system and interfere with its ability to express antiviral cytokines, which are critical in the host defense against viral pathogens. The aim of the current study was to determine if the oncogenes E6 and E7 from CPV2 interfere with expression of antiviral cytokines in keratinocytes, the target cells of papillomavirus infections. We determined that E6 but not E7 interferes with the constitutive expression of some antiviral cytokines, including interferon (IFN)-β and the IFN-stimulated gene IFIT1. Both E6 and E7 interfere with the transcriptional upregulation of the antiviral cytokines in response to stimulation with the dsDNA Poly(dA:dT). In contrast, while E6 also interferes with the transcriptional upregulation of antiviral cytokines in response to stimulation with the dsRNA Poly(I:C), E7 interferes with only a subset of these antiviral cytokines. Finally, we demonstrated that E7 but not E6 abrogates signaling through the type I IFN receptor. Taken together, CPV2 E6 and E7 both impact expression of antiviral cytokines in canine keratinocytes, albeit likely through different mechanisms.
| S-EPMC7354437 | biostudies-literature
Project description:High-risk human papillomavirus (HPV) infection is one of the first events in the process of carcinogenesis in cervical and head and neck cancers. The expression of the viral oncoproteins E6 and E7 are essential in this process by inactivating the tumor suppressor proteins p53 and Rb, respectively, in addition to their interactions with other host proteins. Non-coding RNAs, such as long non-coding RNAs (lncRNAs) have been found to be dysregulated in several cancers, suggesting an important role in tumorigenesis. In order to identify host lncRNAs affected by HPV infection, we expressed the high-risk HPV-16 E6 oncoprotein in primary human keratinocytes and measured the global lncRNA expression profile by high-throughput sequencing (RNA-seq). We found several host lncRNAs differentially expressed by E6 including GAS5, H19, and FAM83H-AS1. Interestingly, FAM83H-AS1 was found overexpressed in HPV-16 positive cervical cancer cell lines in an HPV-16 E6-dependent manner but independently of p53 regulation. Furthermore, FAM83H-AS1 was found to be regulated through the E6-p300 pathway. Knockdown of FAM83H-AS1 by siRNAs decreased cellular proliferation, migration and increased apoptosis. FAM83H-AS1 was also found to be altered in human cervical cancer tissues and high expression of this lncRNA was associated with worse overall survival, suggesting an important role in cervical carcinogenesis.
| S-EPMC6403315 | biostudies-literature
Project description:The hallmark of high-risk human papillomavirus (HR-HPV)-related carcinogenesis is E6 and E7 oncogene overexpression. The aim of this work was to characterize epithelial oral and cervical cancer cells that express HR-HPV E6 and E7 oncoproteins. Transcriptomic assay using DNA microarrays revealed that PIR gene expression was detected in oral cells in an HR-HPV E6/E7-dependent manner. In addition, PIR was overexpressed in HPV-positive SiHa and Ca Ski cells, whereas it was undetectable in HPV-negative C33A cells. The PIR expression was dependent on functional HR-HPV E6 and E7 oncoproteins even though the E7 oncoprotein had higher activity to induce PIR overexpression in comparison with E6. In addition, using an siRNA for PIR silencing in oral cells ectopically expressing HR-HPV E6/E7, there was a significant increase in E-cadherin transcripts and a decrease in Vimentin, Slug, Zeb and Snail transcripts, suggesting that HR-HPV-induced PIR overexpression is involved in epithelial-mesenchymal transition. Furthermore, migration of PIR-silenced cells was significantly decreased. Finally, using inhibitors of some specific pathways, it was found that EGFR/ERK and PI3 K/AKT signalling pathways are important for E7-mediated PIR overexpression. It can be concluded that PIR gene expression is highly dependent on the expression of HR-HPV oncoproteins and is important for EMT regulation.
| S-EPMC5717337 | biostudies-literature
Project description:The degradation of p53 is a hallmark of high-risk human papillomaviruses (HPVs) of the alpha genus and HPV-related carcinogenicity. The oncoprotein E6 forms a ternary complex with the E3 ubiquitin ligase E6-associated protein (E6AP) and tumor suppressor protein p53 targeting p53 for ubiquitination. The extent of p53 degradation by different E6 proteins varies greatly, even for the closely related HPV16 and HPV31. HPV16 E6 and HPV31 E6 display high sequence identity (∼67%). We report here, for the first time, the structure of HPV31 E6 bound to the LxxLL motif of E6AP. HPV16 E6 and HPV31 E6 are structurally very similar, in agreement with the high sequence conservation. Both E6 proteins bind E6AP and degrade p53. However, the binding affinities of 31 E6 to the LxxLL motif of E6AP and p53, respectively, are reduced 2-fold and 5.4-fold compared to 16 E6. The affinity of E6-E6AP-p53 ternary complex formation parallels the efficacy of the subsequent reaction, namely, degradation of p53. Therefore, closely related E6 proteins addressing the same cellular targets may still diverge in their binding efficiencies, possibly explaining their different phenotypic or pathological impacts.IMPORTANCE Variations of carcinogenicity of human papillomaviruses are related to variations of the E6 and E7 interactome. While different HPV species and genera are known to target distinct host proteins, the fine differences between E6 and E7 of closely related HPVs, supposed to target the same cellular protein pools, remain to be addressed. We compare the oncogenic E6 proteins of the closely related high-risk HPV31 and HPV16 with regard to their structure and their efficiency of ternary complex formation with their cellular targets p53 and E6AP, which results in p53 degradation. We solved the crystal structure of 31 E6 bound to the E6AP LxxLL motif. HPV16 E6 and 31 E6 structures are highly similar, but a few sequence variations lead to different protein contacts within the ternary complex and, as quantified here, an overall lower binding affinity of 31 E6 than 16 E6. These results align with the observed lower p53 degradation potential of 31 E6.
| S-EPMC7944444 | biostudies-literature
Project description:Using DNA microarray and clustering of expressed genes we have analyzed the mechanism of inhibition of wild-type p53-induced apoptosis by the cytokine interleukin 6 (IL-6) and the calcium mobilizer thapsigargin (TG). Clustering analysis of 1,786 genes, the expression level of which changed after activation of wild-type p53 in the absence or presence of IL-6 or TG, showed that these compounds did not cause a general inhibition of the ability of p53 to up-regulate or down-regulate gene expression. Expression of various p53 targets implicated as mediators of p53-induced apoptosis was also not affected by IL-6 or TG. These compounds thus can bypass the effect of wild-type p53 on gene expression and inhibit apoptosis. IL-6 and TG activated different p53-independent pathways of gene expression that include up-regulation of antiapoptotic genes. IL-6 and TG also activated different differentiation-associated genes. The ability of compounds such as cytokines and calcium mobilizers to inhibit p53-mediated apoptosis without generally inhibiting gene expression regulated by p53 can facilitate tumor development and tumor resistance to radiation and chemotherapy in cells that retain wild-type p53.
| S-EPMC164513 | biostudies-literature
Project description:UnlabelledSeveral recent studies have converged upon the innate immune DNA cytosine deaminase APOBEC3B (A3B) as a significant source of genomic uracil lesions and mutagenesis in multiple human cancers, including those of the breast, head/neck, cervix, bladder, lung, ovary, and other tissues. A3B is upregulated in these tumor types relative to normal tissues, but the mechanism is unclear. Because A3B also has antiviral activity in multiple systems and is a member of the broader innate immune response, we tested the hypothesis that human papillomavirus (HPV) infection causes A3B upregulation. We found that A3B mRNA expression and enzymatic activity were upregulated following transfection of a high-risk HPV genome and that this effect was abrogated by inactivation of E6. Transduction experiments showed that the E6 oncoprotein alone was sufficient to cause A3B upregulation, and a panel of high-risk E6 proteins triggered higher A3B levels than did a panel of low-risk or noncancer E6 proteins. Knockdown experiments in HPV-positive cell lines showed that endogenous E6 is required for A3B upregulation. Analyses of publicly available head/neck cancer data further support this relationship, as A3B levels are higher in HPV-positive cancers than in HPV-negative cancers. Taken together with the established role for high-risk E6 in functional inactivation of TP53 and published positive correlations in breast cancer between A3B upregulation and genetic inactivation of TP53, our studies suggest a model in which high-risk HPV E6, possibly through functional inactivation of TP53, causes derepression of A3B gene transcription. This would lead to a mutator phenotype that explains the observed cytosine mutation biases in HPV-positive head/neck and cervical cancers.ImportanceThe innate immune DNA cytosine deaminase APOBEC3B (A3B) accounts for a large proportion of somatic mutations in cervical and head/neck cancers, but nothing is known about the mechanism responsible for its upregulation in these tumor types. Almost all cervical carcinomas and large proportions of head/neck tumors are caused by human papillomavirus (HPV) infection. Here, we establish a mechanistic link between HPV infection and A3B upregulation. The E6 oncoprotein of high-risk, but not low-risk, HPV types triggers A3B upregulation, supporting a model in which TP53 inactivation causes a derepression of A3B gene transcription and elevated A3B enzyme levels. This virus-induced mutator phenotype provides a mechanistic explanation for A3B signature mutations observed in HPV-positive head/neck and cervical carcinomas and may also help to account for the preferential cancer predisposition caused by high-risk HPV isolates.
| S-EPMC4278539 | biostudies-literature
Project description:Binding of p53 to miR-34a promoter activates the expression of tumor-suppressive miR-34a. Oncogenic human papillomavirus (HPV) infection downregulates miR-34a expression through viral E6 degradation of p53. In our report, we found that miR-34a specifically targets p18Ink4c, a CDK4 and CDK6 inhibitor induced by E2F transactivation. HPV18(+) HeLa cells with ectopic miR-34a expression or by E6 siRNA knockdown-induced expression of endogenous miR-34a exhibited a substantial reduction of p18Ink4c in a dose-dependent manner, but had no effect on p16Ink4a, another member of CDK4/6 inhibitor family. In contrast, de novo infection by oncogenic HPVs of human keratinocyte-derived raft tissues increased p18Ink4c expression. Suppression of endogenous miR-34a in cell lines with a miR-34a inhibitor also increased p18Ink4c. We found that miR-34a suppresses the expression of p18Ink4c by binding to a specific seed match in the 5' UTR of p18Ink4c. Further investigation found remarkable increase of p18Ink4c in cervical precancer lesions and cervical cancer. Immunohistochemical staining of cervical tissue arrays showed increased expression of p18Ink4c in 68% of cervical cancer, 8.3% of chronic cervical inflammation and 4.8% of normal cervix. Although p18Ink4c inhibits cell proliferation in general and regulates E2F1 expression in HCT116 cells, it appears not to function as a tumor suppressor in cervical cancer cells lacking an intact G1 checkpoint because of viral E7 degradation of pRB. In summary, our study demonstrates an intimate connection among oncogenic HPV E6, p53, miR-34a and p18Ink4c and identifies p18Ink4c as a possible biomarker for cervical cancer.
| S-EPMC3086996 | biostudies-literature