HPV16 E6 promoting cervical cancer progression through down-regulation of miR-320a to increase TOP2A expression

BACKGROUND

Cervical cancer (CC) has become the fourth most common cancer worldwide and it is mainly caused by the infection of human papillomavirus (HPV), especially high-risk HPV16. Aberrant miRNA expression in CC is closely related to HPV16 infection, and the regulation of HPV16 E6 expression can affect a variety of miRNA expression. This study aims to exploring the miRNAs involved in E6 regulation in CC.

METHODS

Our study screened differentially expressed miRNAs in cervical cells of HPV16 infected and uninfected cervical cancer patients by analyzing the GSE81137 dataset of the gene expression omnibus database (GEO), and identified miR-320a that plays an anti-tumor role and is associated with good prognosis of cervical cancer. Explore the effect of HPV16 E6 on the expression of miR-320a in cervical cancer, and verify whether HPV16 E6 regulates the downstream target gene TOP2A expression through miR-320a, thereby affecting cervical cancer cell proliferation, apoptosis, migration, invasion, and EMT in vitro and in vivo.

RESULTS

The bioinformatic methods selected the miR-320a, which was differentially expressed in cervical cells from HPV16-infected patients compared to uninfected patients. We further demonstrated that miR-320a level was regulated by HPV16 E6, which promoted the CC cell proliferation, migration, invasion, and inhibited apoptosis. In addition, we predicted the downstream target genes of miR-320a and confirmed that TOP2A was one of its targeting proteins. Moreover, HPV16 E6 promoted the TOP2A expression in CC cells through down-regulating miR-320a, leading to promoting CC development.

CONCLUSIONS

We confirmed that HPV16 E6 promoted the TOP2A expression through down-regulation of miR-320a, thus promoting CC development, and the HPV16 E6/miR-320a/TOP2A axis may perform as a potential target for CC treatment.

In silico Analysis of Natural Inhibitors against HPV E6 Protein

BACKGROUND

Drug re-purposing is one of the cost-effective methods to establish novel therapeutics against many diseases. Established natural products are collected from databases and used to potentially screen them against HPV E6 protein, a critical viral protein.

OBJECTIVE

This study aims to design potential small molecule inhibitors against HPV E6 protein using structure-based approaches. Ten natural anti-cancerous compounds (Apigenin, Baicalein, Baicalin, Ponicidin, Oridonin, Lovastatin, Triterpenoid, Narirutin, Rosmarinic Acid, and Xanthone) were selected by review of the literature.

METHODS

These compounds were screened using Lipinski Rule of Five. Out of ten compounds, seven were found to satisfy Rule of five. Docking of these seven compounds was carried out using AutoDock software and corresponding Molecular Dynamics Simulations were performed by GROMACS.

RESULTS

Among the seven compounds docked with the E6 target protein, six compounds showed lesser binding energy than the reference compound, Luteolin. The three-dimensional structures of E6 protein and the corresponding ligand complexes were visualised and analysed using PyMOL whereas the two-dimensional images of protein-ligand interactions were obtained by LigPlot⁺ software to study the specific interactions. ADME analysis using SwissADME software revealed that all the compounds except Rosmarinic acid have good gastrointestinal absorption and solubility characteristics while Xanthone and Lovastatin showed blood brain barrier penetration properties. Considering the binding energy and ADME analysis, Apigenin and Ponicidin are found to be most suitable for de novo designing of potential inhibitors against the HPV16 E6 protein.

CONCLUSION

Further, synthesis and characterization of these potential HPV16 E6 inhibitors will be carried out and their functional evaluation using cell culture-based assays will be undertaken.

hnRNP K induces HPV16 oncogene expression and promotes cervical cancerization

PURPOSE

This study aims to explore the expression of hnRNP K in cervical carcinogenesis and to investigate the regulatory role of hnRNP K on HPV16 oncogene expression as well as biological changes in cervical cancer cells.

METHODS

In total 1042 subjects, including 573 with the normal cervix and 469 with different grades of cervical lesions were enrolled in this study to explore the association between hnRNP K and HPV16 oncogene expression in cervical carcinogenesis. Additionally, the Gene Omnibus (GEO) database was used to analyze hnRNP K mRNA expression in cervical cancerization. Meanwhile, the effects of hnRNP K on cell biological functions and HPV16 oncogene expression were investigated in Siha cells. Moreover, Function analyses were conducted using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) databases after ChIP-seq.

RESULTS

hnRNP K was highly expressed in cervical cancer and precancerous lesions, and positively correlated with HPV16 E6, but negatively correlated with HPV16 E2 and HPV16 E2/E6 ratio. hnRNP K induced cell proliferation, inhibited apoptosis and caused cell cycle arrest in the S phase, and particularly increased HPV16 E6 protein expression.

CONCLUSION

This study revealed that hnRNP K overexpression has important warning significance for the malignant transformation of cervical lesions, and could be used as a potential therapeutic target for inhibiting the carcinogenicity of HPV16 and prevention of cervical carcinogenesis.

Human Papillomavirus 16 E6 Suppresses Transporter Associated with Antigen-Processing Complex in Human Tongue Keratinocyte Cells by Activating Lymphotoxin Pathway

Simple Summary

There is still limited knowledge of the critical pathogenic processes by which HPV16 induces oral carcinogenesis. Therefore, we aimed to illuminate the oncogenic role of HPV16 in the context of oral squamous cell carcinomas (OSCCs). Using human tongue keratinocyte cells, we demonstrated that HPV16 E6 promotes LTα₁β₂ and LTβR expression, thus promoting the lymphotoxin signaling pathway and leading to suppression of the transporter associated with the antigen-processing complex (TAPs; TAP1 and TAP2). Additionally, in vitro, we also demonstrated regulation of the antigenic peptide-loaded machinery in HPV-infected OSCC tissues through analysis of the transcriptomic profiles of the head and neck squamous cell carcinoma (HNSCC) cohort from the TCGA database, which was validated using fresh biopsied specimens. Thus, our study enhances the proposed functional role of HPV16 E6-associated immune-evasive properties in oral epithelial cells, revealing a possible mechanism underlying the development of HPV-mediated OSCCs.

Abstract

Infection by high-risk human papillomaviruses (hrHPVs), including HPV type 16 (HPV16), is a major risk factor for oral squamous cell carcinomas (OSCCs). However, the pathogenic mechanism by which hrHPVs promote oral carcinogenesis remains to be elucidated. Here, we demonstrated that the suppression of a transporter associated with the antigen-processing complex (TAPs; TAP1 and TAP2), which is a key molecule in the transportation of viral antigenic peptides into MHC class-I cells, is affected by the E6 protein of HPV16. Mechanistically, HPV-mediated immune evasion is principally mediated via the signal-transduction network of a lymphotoxin (LT) pathway, in particular LTα₁β₂ and LTβR. Our analysis of transcriptomic data from an HNSCC cohort from the Cancer Genome Atlas (TCGA) indicated that expression of TAP genes, particularly TAP2, was downregulated in HPV-infected cases. We further demonstrated that LTα₁β₂ and LTβR were upregulated, which was negatively correlated with TAP1 and TAP2 expression in HPV-positive clinical OSCC samples. Taken together, our findings imply that HPV16 E6 regulates the machinery of the antigenic peptide-loading system and helps to clarify the role of oncogenic viruses in the context of oral carcinoma.

HPV16 E6 gene polymorphisms and the functions of the mutation site in cervical cancer among Uygur ethnic and Han nationality women in Xinjiang, China

BACKGROUND

To investigate the genotype distribution of human papillomavirus (HPV) in infected Uygur and Han women in Xinjiang, China; analyze the HPV16 E6 gene polymorphism site and relationship with the development of cervical cancer.

METHODS

The HPV16 E6 sequence was analyzed using the European standard prototype to perform an evolutionary tree. HPV16 E6-T295/T350, G295/G350, and T295/G350 GV230 vectors were stably transfected into cervical cancer C33A cells to analyze the cell proliferation, migration and invasion, apoptosis by CCK8 and clonogenic assays, transwell and cell scratch assays, FACS experiments.

RESULTS

The total HPV infection rate was 26.390% (760/2879), whereas the Uygur 22.87% (196/857) and the Han was 27.89% (564/2022) (P < 0.05). Among 110 mutations, 65 cases of E6 genes were mutated at nucleotide 350 (T350G) with the leucine changing to valine (L83V). Moreover, there were 7 cases of E6 gene mutated at nucleotide 295 (T295G) with aspartic changing to glutamic (D64E). When E6 vector(s) of mutations sites were transfected into C33A cells, they were found to promote cellular proliferation, migration, invasion, and inhibit apoptosis. T295/G350-E6 was significantly stronger than G295/G350 and T295/T350, G295/G350 was significantly stronger than T295/T350 (P < 0.05). The T295/G350 had the strongest effect on C33A cells and G295/G350 was significantly stronger than T295/T350 (P < 0.05).

CONCLUSIONS

The positive HPV infection rates differed between the Uygur and Han in Xinjiang, China, and the genotype distribution of infection was different. After transfecting C33A cells with different eukaryotic expression vectors, the T295/G350 mutation site promoted the proliferation, migration, and invasion of C33A cells to a greater extent than G295/G350; however, G295/G350 had a stronger effect than T295/T350.

Identification of a peptide that disrupts hADA3-E6 interaction with implications in HPV induced cancer therapy

AIM

High risk Human Papillomavirus (HPV) is an infectious pathogen implicated in a variety of cancers with poor clinical outcome. The mechanism of HPV induced cellular transformation and its intervention remains to be elucidated. Human ADA3 (hADA3), a cellular target of HPV16 E6, is an essential and conserved component of the ADA transcriptional coactivator complex. High risk HPV-E6 binds and functionally inactivates hADA3 to initiate oncogenesis. The aim of this study was to identify the interaction interface between hADA3 and HPV16E6 for designing inhibitory peptides that can potentially disrupt the hADA3-E6 interaction.

MATERIAL METHODS

The present investigation employed structure-based in silico tools supported by biochemical validation, in vivo interaction studies and analysis of posttranslational modifications.

KEY FINDINGS

First 3D-model of hADA3 was proposed and domains involved in the oncogenic interaction between hADA3 and HPV16E6 were delineated. Rationally designed peptide disrupted hADA3-E6 interaction and impeded malignant properties of cervical cancer cells.

SIGNIFICANCE

Intervention of hADA3-E6 interaction thus promises to be a potential strategy to combat HPV induced oncogenic conditions like cervical cancer. The investigation provides mechanistic insights into HPV pathogenesis and shows promise in developing novel therapeutics to treat HPV induced cancers.

Targeting Aberrant Expression of STAT3 and AP-1 Oncogenic Transcription Factors and HPV Oncoproteins in Cervical Cancer by Berberis aquifolium

Background: Present study examines phytochemical preparation that uses berberine's plant source B. aquifolium root for availability of similar anti-cervical cancer (CaCx) and anti-HPV activities to facilitate repurposing of the B. aquifolium based drug in the treatment of CaCx. Purpose: To evaluate therapeutic potential of different concentrations of ethanolic extract of B. aquifolium root mother tincture (BAMT) against HPV-positive (HPV16: SiHa, HPV18: HeLa) and HPV-negative (C33a) CaCx cell lines at molecular oncogenic level. Materials and Methods: BAMT was screened for anti-proliferative activity by MTT assay. Cell cycle progression was analyzed by flowcytometry. Then, the expression level of STAT3, AP-1, HPV E6 and E7 was detected by immunoblotting, whereas nuclear localization was observed by fluorescence microscopy. Phytochemicals reportedly available in BAMT were examined for their inhibitory action on HPV16 E6 by in silico molecular docking. Results: BAMT induced a dose-dependent decline in CaCx cell viability in all cell types tested. Flowcytometric evaluation of BAMT-treated cells showed a small but specific cell growth arrest in G1-phase. BAMT-treatment resulted in reduced protein expression of key transcription factors, STAT3 with a decline of its active form pSTAT3 (Y705); and components of AP-1 complex, JunB and c-Jun. Immunocytochemistry revealed that BAMT did not prevent the entry of remnant active transcription factor to the nucleus, but loss of overall transcription factor activity resulted in reduced availability of transcription factors in the cancer cells. These changes were accompanied by gradual loss of HPV E6 and E7 protein in BAMT-treated HPV-positive cells. Molecular docking of reported active phytochemicals in B. aquifolium root was performed, which indicated a potential interference of HPV16 E6's interaction with pivotal cellular targets p53, E6AP or both by constituent phytochemicals. Among these, berberine, palmatine and magnoflorine showed highest E6 inhibitory potential. Conclusion: Overall, BAMT showed multi-pronged therapeutic potential against HPV infection and cervical cancer and the study described the underlying molecular mechanism of its action.

HPV16 E6 Promotes the Progression of HPV Infection-Associated Cervical Cancer by Upregulating Glucose-6-Phosphate Dehydrogenase Expression

Cervical cancer, which is significantly associated with high-risk human papillomavirus (HPV) infection, currently ranks the fourth most common cancer among women worldwide. Previous literature reported that the elevated expression of G6PD was significantly correlated with the occurrence and deterioration of human cervical cancer, especially with the cervical cancer with HPV16 and HPV18 infection. In this study, we verified that G6PD expression has a strong positive correlation with HPV16 E6 levels in cervical cancer tissues and cells. In addition, regulating the expression of HPV16 E6 significantly affected the proliferation, apoptosis, migration, and invasion in the cervical cancer HeLa cells, as well as the transcript and protein levels of G6PD. The luciferase reporter assay and ChIP assay proved that HPV16 E6 stimulated the transcription of G6PD mRNA and subsequently enhanced the expression of G6PD through directly binding to the specific sites in the promoter of G6PD. Our findings reveal that HPV16 E6 is a novel regulatory factor of G6PD. Furthermore, by regulating the expression of G6PD, HPV16 E6 might promote the proliferation and migration potential, and inhibit apoptosis of cervical cancer cells, which ultimately contributed to the progression and metastasis of cervical cancer.

The Dimeric Form of HPV16 E6 Is Crucial to Drive YAP/TAZ Upregulation through the Targeting of hScrib

Simple Summary

Understanding the mechanisms of action of HPV oncoproteins is pivotal for the rationale development of anti-cancer drugs to treat HPV-related malignancies. The aim of the present study was to explore more in detail the mechanism of action of the HPV16 oncoprotein E6 that directly fosters the YAP/TAZ signaling pathway, a conserved cascade highly active in HPV-related cancers. We confirmed previous evidence about the importance of the PDZ-protein targeting in this process, highlighting here the importance of hScrib degradation, and discovered that the targeting of the Scribble module involves the dimeric form of HPV16 E6. The findings here presented extend our knowledge about the mechanism through which the oncoprotein E6 targets a PDZ-host factor to degradation in cancer cells.

Abstract

Human papillomavirus is the most common viral infectious agent responsible for cancer development in humans. High-risk strains are known to induce cancer through the expression of the viral oncogenes E6 and E7, yet we have only a partial understanding of the precise mechanisms of action of these viral proteins. Here we investigated the molecular mechanism through which the oncoprotein E6 alters the Hippo-YAP/TAZ pathway to trigger YAP/TAZ induction in cancer cells. By employing E6 overexpression systems combined with protein–protein interaction studies and loss-of-function approaches, we discovered that the E6-mediated targeting of hScrib, which supports YAP/TAZ upregulation, intimately requires E6 homodimerization. We show that the self-association of E6, previously reported only in vitro, takes place in the cytoplasm and, as a dimer, E6 targets the fraction of hScrib at the cell cortex for proteasomal degradation. Thus, E6 homodimerization emerges as an important event in the mechanism of E6-mediated hScrib targeting to sustain downstream YAP/TAZ upregulation, unraveling for the first time the key role of E6 homodimerization in the context of its transforming functions and thus paving the way for the possible development of E6 dimerization inhibitors.

Oncolytic adenoviral H101 synergizes with radiation in cervical cancer cells

BACKGROUND

A major challenge in cervical cancer radiotherapy is to tailor the radiation doses efficiently to both eliminate malignant cells and to reduce the side effects to normal tissue. Oncolytic adenoviral drug H101 is recently tested and approved for topical adjuvant treatment of several malignancies.

OBJECTIVE

This study is to evaluate the potential neoadjuvant radiotherapy benefits of H101 by testing the inhibitory function of H101 combined with radiation in different cervical cancer cells.

METHODS

Human cervical cancer cells C33a, SiHa, CaSki, and Hela were treated with varying concentrations of H101 alone or combined with radiation (2Gy or 4Gy). Cell viability and apoptosis were measured at indicated time intervals. HPV16 E6 and cellular p53 mRNA expression alteration were measured by qRT-PCR. RNA scope in-situ detect HPV E6 status. P53 protein alteration are detected by Western blot.

RESULTS

Cell viability and apoptosis show the combination of a high dose of H101 (MOI=1000, 10000) with radiation yielded a synergistic anti-cancer effect in all tested cervical cancer cell lines (P<0.05), with the greatest effect achieved in HPV negative C33a cells (P<0.05). Low HPV16 viral load SiHa cell was more sensitive to combination therapy than high HPV16 viral load CaSki cell (P<0.05). The combined treatment could reduce HPV16 E6 expression and increase cellular P53 level compared to radiation alone in SiHa and CaSki (P<0.05).

CONCLUSIONS

Oncolytic adenoviral H101 effectively enhances the antitumor efficacy of radiation in cervical cancer cells and may serve as a novel combination therapy for cervical cancer.

Multiple imputation and clinico-serological models to predict human papillomavirus status in oropharyngeal carcinoma: An alternative when tissue is unavailable

In cancer epidemiological studies, determination of human papillomavirus (HPV) in oropharyngeal squamous cell carcinoma (OPSCC) typically depends on the availability of tumor tissue testing, and/or tumor tissue access. Identifying alternative methods for estimating HPV status can improve the quality of such studies when tissue is unavailable. We developed multiple predictive models for tumor HPV status and prognosis by combining both clinico-epidemiological variables and either serological multiplex assays of HPV or multiple imputation of HPV status (HPV_mi ). Sensitivity, specificity and accuracy of these methods compared to either p16 immunostaining (p16 IHC) or survival were assessed. When compared to a reference of tumor tissue p16 IHC in 783 OPSCC patients, the clinic-HPV_sero model incorporating a composite of 20 HPV serological antibodies (HPV_sero ) and 4 clinical factors (c-index: 0.96) performed better than using HPV_sero (c-index: 0.92) or HPV_mi (c-index: 0.76) alone. However, the model that contained a single HPV16 E6 antibody combined with four clinical variables, performed extremely well (clinic-s1-16E6; c-index: 0.95). When defining HPV status by HPV_sero , s1-16E6, HPV_mi or through p16 IHC, each of these definitions demonstrated improved overall and disease-free survival in HPV-positive OPSCC patients, when compared to HPV-negative patients (adjusted hazard ratios between 0.25 and 0.63). Our study demonstrates that when blood samples are available, a model that utilizes a single s1-16E6 antibody combined with several clinical features has excellent test performance characteristics to estimate HPV status and prognosis. When neither blood nor tumor tissue is available, multiple imputation, calibrated on local population characteristics, remains a viable, but suboptimal option.

Efficacy of PD-1 blockade in cervical cancer is related to a CD8+FoxP3+CD25+ T-cell subset with operational effector functions despite high immune checkpoint levels

Background

Cervical cancer (CxCa) is mainly a locally invading disease that metastasizes to loco-regional lymph node basins before involving distant organs in more advanced stages. Local immune potentiation of tumor-draining lymph nodes (TDLN) may thus protect against tumor progression.

Methods

To identify therapeutic targets for local immune modulation, multi-parameter flow cytometric T-cell profiling of primary cervical tumors (PT) and TDLN (n = 37) was performed. The in-vitro effect of PD-1 blockade on T-cell reactivity to HPV16 E6 oncoproteins was determined in cultures of TDLN and PT single cell suspensions (n = 19). Also, intracellular cytokine staining (ICS) upon anti-CD3 stimulation was performed in metastatic TDLN (LN+) and PT (n = 7), as well as multiplexed immunofluorescence histochemistry staining (n = 8).

Results

Our data revealed elevated rates of activated regulatory T cells (aTregs) and of central or effector memory CD8⁺ T cells in metastatic TDLN (LN+) as compared to tumor-free TDLN (LN-), and equally high or even higher rates of these subsets in PT. Both memory subsets co-expressed multiple immune checkpoints. PD-1 blockade significantly enhanced detectable E6-specific T-cell responses in 4/5 HPV16+ LN+ and in 1/5 HPV16+ PT. Whereas aTreg rates were higher in anti-PD-1 non-responders, in responders elevated levels of CD8⁺FoxP3⁺CD25⁺ T cells were observed, which correlated with the efficacy of PD-1 blockade (P = 0.018). This subset was characterized by an early effector memory phenotype with particularly high levels of co-expressed PD-1, CTLA-4, TIM-3 and LAG-3 checkpoints, but, rather than exhausted, was shown upon polyclonal activation to produce higher levels of Granzyme-B and effector cytokines as compared to its CD8⁺FoxP3⁻ counterparts.

Conclusion

These observations support local PD-(L)1 blockade to interrupt loco-regional immune suppression in CxCa and control metastatic spread to TDLN. Furthermore, our data identify CD8⁺FoxP3⁺CD25⁺ T cells as therapeutic targets, which may also serve as predictive biomarker for PD-(L)1 checkpoint blockade.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0526-z) contains supplementary material, which is available to authorized users.

Cyclin-dependent kinase 9 promotes cervical cancer development via AKT2/p53 pathway

Aberrant activation of cyclin-dependent kinase 9 (CDK9) is widespread in human cancers. However, the underlying mechanisms of CDK9 activation and the therapeutic potential of CDK9 inhibition in cervical cancer remain largely unknown. Here, we report that CDK9 is gradually upregulated during cervical lesion progression and regulated by HPV16 E6. CDK9 levels are highly correlated with FIGO stage, pathological grade, deep-stromal invasion, tumor size, and lymph nodes metastasis. Knockdown of CDK9 by specific siRNA inhibits cervical cancer cell proliferation in vitro, as well as tumorigenesis in vivo. CDK9 inhibition causes a significant decreased AKT2 and increased p53 protein expression revealing novel CDK9-regulatory mechanisms. Overexpression of AKT2 rescued the suppressive effects caused by CDK9 knockdown, suggesting that AKT2 induction is essential for CDK9-induced transformation. Moreover, CDK9 expression was positively correlated with AKT2 and negatively correlated with p53 in cervical cancer tissues with HPV16 infection. Our findings demonstrate for the first time that CDK9 acts as a proto-oncogene in cervical cancer, modulating cell proliferation and apoptosis through AKT2/p53 pathway. Therefore, our data provide novel mechanistic insights into the role of CDK9 in cervical cancer development. © 2018 IUBMB Life, 71(3):347-356, 2019.

Analysis of human papillomavirus 16 E6/E7 and L1 in the bronchial brushing cells of patients with squamous cell carcinoma of the lungs

A type of high-risk human papillomavirus (HPV), HPV16 takes part in lung carcinogenesis. E6 and E7 are the major oncoproteins of high-risk HPV, and L1 is the major capsid protein. In this study, we detected their mRNA expressions and analyzed their relationship in the bronchial brushing cells of 211 patients with malignant lesions (squamous cell carcinoma of the lungs) and benign lesions (pneumonia and tuberculosis) by quantitative real-time PCR. HPV16 E6, E7, and L1 mRNA expressions in the malignant group were statistically higher than in benign group (P<0.05), and their mRNA expressions in the squamous cell carcinoma of the lung group were statistically higher than in pneumonia group (P<0.05). There was a negative correlation between L1 and E6 expression in the squamous cell carcinoma of the lungs group (Spearman correlation coefficient r=-0.498, P=0.000). An ROC curve shows that the combination of L1 and E6 is a significant predictor for the diagnosis of squamous cell carcinoma of the lungs (AUC: 0.878; Sensitivity: 96.00%; Specificity: 77.91%), which could make up for the deficiency of cytologic testing. The combined detection of HPV16 E6 and L1 mRNA expressions in bronchial brushing cells by quantitative real-time PCR has a great significance for the diagnosis of squamous cell carcinoma of the lungs, providing new therapeutic targets for the clinical treatment of squamous cell carcinoma of the lungs.

Human papillomavirus (HPV) 16 E6 oncoprotein targets the Toll-like receptor pathway

Cervical cancer is one of the leading causes of death in women worldwide and is etiologically linked to human papillomavirus (HPV) infection. Viral early proteins E6 and E7 manipulate cellular functions to promote the virus life cycle and are essential to the cellular transformation process. The innate immune system plays a pivotal role in the natural history of HPV infection. Among the various proteins that mediate the innate immune response, Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) and initiate the immune response. The objective of this study was to identify HPV E6 protein interaction partners in the TLR signalling pathway that may play a role in the immune response against HPV. Six TLR pathway proteins were shown to interact with HPV16 E6: myeloid differentiation primary response protein (MyD88), TIR domain-containing adapter molecule 1 (TRIF), interleukin-1 receptor-associated kinase-like (IRAK) 2, TNF receptor-associated factor (TRAF) 6, I-κB kinase beta (IKKβ) and I-κB kinase epsilon (IKKε). The interaction site of IKKε with E6 is located in the region containing the enzyme catalytic site, suggesting an influence of E6 on the activation of IKKε target proteins. HPV16 E6 potentiated the activation of NF-κB by various TLR pathway members. These results suggest that HPV16 has the ability to interfere with components of the immune response, contributing to HPV carcinogenesis.

C33-A cells transfected with E6*I or E6*II the short forms of HPV-16 E6, displayed opposite effects on cisplatin-induced apoptosis

The HPV-16 E6/E7 bicistronic immature transcript produces 4 mature RNAs: the unspliced HPV-16 E6/E7^pre-mRNA product and 3 alternatively spliced mRNAs. The 3 spliced mRNAs encode short forms of the E6 oncoprotein, namely E6*I, E6*II and E6^E7. In this study we showed that transfection of C-33A cells with monocistronic constructs of these cDNAs fused to GFP, produced different effects on apoptosis, after the treatment with cisplatin. Transfection of C-33A cells with the full-length E6-GFP oncoprotein resulted in a 50% decrease in cell death, while the transfection with the E6*I-GFP construct showed only a 25% of diminution of cell death, compared to the control cells. Transfection with the E6^E7-GFP or E7-GFP construct had no effect on the number of the apoptotic cells, compared with control cells. Conversely, transfection with the E6*II construct resulted in higher cell death than the control cells. Taken together, these results suggested that E6*I or E6*II, the short forms of HPV-16 E6, displayed opposite effects on cisplatin-induced apoptosis, when transfected in C-33A cells.

MG132 plus apoptosis antigen-1 (APO-1) antibody cooperate to restore p53 activity inducing autophagy and p53-dependent apoptosis in HPV16 E6-expressing keratinocytes

The E6 oncoprotein can interfere with the ability of infected cells to undergo programmed cell death through the proteolytic degradation of proapoptotic proteins such as p53, employing the proteasome pathway. Therefore, inactivation of the proteasome through MG132 should restore the activity of several proapoptotic proteins. We investigated whether in HPV16 E6-expressing keratinocytes (KE6 cells), the restoration of p53 levels mediated by MG132 and/or activation of the CD95 pathway through apoptosis antigen-1 (APO-1) antibody are responsible for the induction of apoptosis. We found that KE6 cells underwent apoptosis mainly after incubation for 24 h with MG132 alone or APO-1 plus MG132. Both treatments activated the extrinsic and intrinsic apoptosis pathways. Autophagy was also activated, principally by APO-1 plus MG132. Inhibition of E6-mediated p53 proteasomal degradation by MG132 resulted in the elevation of p53 protein levels and its phosphorylation in Ser46 and Ser20; the p53 protein was localized mainly at nucleus after treatment with MG132 or APO-1 plus MG132. In addition, induction of its transcriptional target genes such as p21, Bax and TP53INP was observed 3 and 6 h after treatment. Also, LC3 mRNA was induced after 3 and 6 h, which correlates with lipidation of LC3B protein and induction of autophagy. Finally, using pifithrin alpha we observed a decrease in apoptosis induced by MG132, and by APO-1 plus MG132, suggesting that restoration of APO-1 sensitivity occurs in part through an increase in both the levels and the activity of p53. The use of small molecules to inhibit the proteasome pathway might permit the activation of cell death, providing new opportunities for CC treatment.

MiR-187 overexpression inhibits cervical cancer progression by targeting HPV16 E6

Aberrantly expressed microRNAs contribute to the initiation and progression of human cancer. MiRNA-187 has been reported in nasopharyngeal, renal, pancreatic, prostate, and esophageal cancer, and acts as a tumor suppressor or oncogene. However, the underlying function of miRNA-187 in cervical cancer remains largely unexplored. In the present study, we demonstrated significantly miRNA-187 down-regulation in cervical cancer tissues and cell lines compared to their normal counterparts. Kaplan-Meier analysis revealed that decreased miRNA-187 was closely associated with shorter overall survival and relapse-free survival. Gain- and loss-of-function studies showed that miRNA-187 suppressed cervical cancer cell proliferation, migration, and invasion, and promoted cervical cancer cell apoptosis. Furthermore, luciferase reporter assay determined that human papillomavirus 16 E6 was a direct functional target of miRNA-187. Taken together, our findings indicate the essential role of miRNA-187 in suppressing cervical cancer progression and indicate a novel link between miRNA-187 and human papillomavirus 16 E6 in cervical cancer.

Human Papillomavirus (HPV) 16 E6 seropositivity is elevated in subjects with oral HPV16 infection

INTRODUCTION

Human Papillomavirus (HPV) 16 E6 serum antibodies are common in people with HPV-related oropharyngeal cancers (HPV-OPC), but not the general population. We explored HPV16 seroprevalence in people with and without oral HPV16 infection, the cause of HPV-OPC.

METHODS

Oral rinse samples were collected semiannually and tested for 36 types of HPV DNA by PCR. HPV16 E6 serum antibodies were tested at the visit of first oral HPV detection in participants with prevalent (n=54), or incident (n=39) oral HPV16 DNA; or at baseline in matched participants with no oral HPV16 DNA (n=155) using multiplex serology assay. Predictors of seropositivity were examined using logistic regression.

RESULTS

HPV16 E6 seropositivity (7.5% vs 0.7%; p=0.005) but not seropositivity to the other HPV16 antigens, was significantly more common in those with than without oral HPV16 infection. There were only 8 HPV16 E6 seropositive participants, but oral HPV16 DNA remained a strong predictor of E6 seropositivity after adjustment for other risk factors (aOR=14.6 95%CI, 1.7-122.5). Seroprevalence was similar in those with prevalent (7.4%; 4/54), and incident (7.7%; 3/39) oral HPV16 infection (p=1.00). E6 seroprevalence was associated with reduced oral HPV16 clearance, but was not statistically significant (HR=0.65 95% CI, 0.16-2.70). Seropositive participants were primarily male (87.5%), HIV-positive (75.0%; median CD4 cell-count of 840) and had oral HPV16 DNA (87.5%). History of an HPV-related cancer (0/8) or HPV-related anogenital dysplasia (1/8) was rare, and 4 participants had recent screening showing no anogenital dysplasia.

DISCUSSION

HPV16 E6 seropositivity was higher among people with than without oral HPV16 infection, despite no known anogenital disease in these participants.

Characterization of human papillomavirus antibodies in individuals with head and neck cancer

BACKGROUND

Human papillomavirus type 16 (HPV16) E6 antibodies are a promising biomarker of oropharyngeal cancer (OPC); however, seropositivity among non-OPC cases is not well characterized.

METHODS

Pre-treatment sera from 260 (38 OPC, 222 non-OPC) incident head and neck cancers diagnosed at the University of Pittsburgh between 2003 and 2006 were tested for HPV16 (L1,E1,E2,E4,E6,E7) and non-HPV16 E6 (HPV6,11,18,33) antibodies. Sensitivity and specificity of HPV16 E6 antibodies for HPV-driven tumors was evaluated among tumors with known HPV status (n=25).

RESULTS

63.2% of OPC versus 27.5% of non-OPC cases were HPV16 seropositive; HPV16 E6 seroprevalence was 60.5% and 6.3% respectively, odds ratio 22.8 (95% confidence interval [CI] 9.8-53.1). Sensitivity and specificity of HPV16 E6 antibodies for HPV-driven OPC was 100% [95% CI: 50-100%; n=6] and 100% [95% CI: 60-100%, n=4] compared to 0% (n=2) and 0% (n=13) for non-OPC cases.

CONCLUSIONS

HPV16 antibodies were significantly more common in OPC versus non-OPC cases, particularly HPV16 E6 antibodies.