Human papillomavirus 16 E5 modulates the expression of host microRNAs

Human papilloma virus, DNA methylation and microRNA expression in cervical cancer (Review)

Cancer is a complex disease caused by genetic and epigenetic abnormalities that affect gene expression. The progression from precursor lesions to invasive cervical cancer is influenced by persistent human papilloma virus (HPV) infection, which induces changes in the host genome and epigenome. Epigenetic alterations, such as aberrant miRNA expression and changes in DNA methylation status, favor the expression of oncogenes and the silencing of tumor-suppressor genes. Given that some miRNA genes can be regulated through epigenetic mechanisms, it has been proposed that alterations in the methylation status of miRNA promoters could be the driving mechanism behind their aberrant expression in cervical cancer. For these reasons, we assessed the relationship among HPV infection, cellular DNA methylation and miRNA expression. We conclude that alterations in the methylation status of protein-coding genes and various miRNA genes are influenced by HPV infection, the viral genotype, the physical state of the viral DNA, and viral oncogenic risk. Furthermore, HPV induces deregulation of miRNA expression, particularly at loci near fragile sites. This deregulation occurs through the E6 and E7 proteins, which target miRNA transcription factors such as p53.

Heterogeneity of microRNAs expression in cervical cancer cells: over-expression of miR-196a

In recent years, the study of microRNAs associated with neoplastic processes has increased. Patterns of microRNA expression in different cell lines and different kinds of tumors have been identified; however, little is known about the alterations in regulatory pathways and genes involved in aberrant set of microRNAs. The identification of these altered microRNAs in several cervical cancer cells and potentially deregulated pathways involved constitute the principal goals of the present study. In the present work, the expression profiles of cellular microRNAs in Cervical Cancer tissues and cell lines were explored using microRNA microarray, Affymetrix. The most over-expressed was miR-196a, which was evaluated by real time PCR, and HOXC8 protein as potential target by immunohistochemistry assay. One hundred and twenty three human microRNAs differentially expressed in the cell tumor, 64 (52%) over-expressed and 59 (48%) under-expressed were observed. Among the microRNAs over-expressed, we focused on miR-196a; at present this microRNA is poorly studied in CC. The expression of this microRNA was evaluated by qRT-PCR, and HOXC8 by immunohistochemistry assay. There is not a specific microRNA expression profile in the CC cells, neither a microRNA related to HPV presence. Furthermore, the miR-196a was over-expressed, while an absence of HOXC8 expression was observed. We suggest that miR-196a could be played as oncomiR in CC.

HPV16 E5 and KGFR/FGFR2b interplay in differentiating epithelial cells

The E5 oncogenic protein of the human papillomavirus type 16 (HPV16 E5) cooperates in epithelial transformation perturbing the behaviour of differentiating suprabasal cells. Among the receptor tyrosine kinases deregulated by 16E5 expression, the key paracrine mediator of epithelial homeostasis keratinocyte growth factor receptor (KGFR/FGFR2b) is altered in its signaling and endocytic traffic in undifferentiated keratinocytes expressing 16E5 and it would represent a major target of the viral protein in differentiated cells. With the aim to specifically address the possible interplay of 16E5 with KGFR/FGFR2b in cells already committed to differentiation, we took advantage of an in vitro model for forced overexpression or depletion of KGFR in E5 expressing human keratinocytes under synchronous waves of differentiation. Quantitative RT-PCR, biochemical and immunofluorescence analysis showed that KGFR down-modulation is responsible for a E5-mediated decrease of the early differentiation marker K1 and that the receptor re-expression as well as triggering of its kinase activity and signaling are able to efficiently counteract the impairment of differentiation, providing a further demonstration of the tumor-suppressive role of KGFR in the new unexplored context of HPV16 E5-mediated carcinogenesis. In addition, KGFR induced a ligand-dependent decrease of p63 through a miR-203 independent mechanism and this effect was blocked by inhibition of the PI3K/Akt signaling, which is the main pathway involved in KGFR-dependent keratinocyte differentiation, suggesting that alterations of the KGFR/p63 crosstalk are responsible for the impairment of keratinocyte differentiation induced by 16E5 and that the opposite tumor-suppressive action of KGFR and oncogenic role of E5 might both involve p63.

MicroRNAs as biomarkers of cervical cancer development: a literature review on miR-125b and miR-34a

MicroRNAs are non-coding RNAs with important functions in several biological processes, such as, regulation of cell cycle, immune response, inflammation, and apoptosis. In fact, deregulation and abnormal expression of these molecules is associated with human pathologies including cancer and several have already emerged as potential prognostic biomarkers in different neoplasias. miR-34a is directly regulated by p53 and acts as tumor suppressor while miR-125b plays a significant role in immune response and apoptosis. In cervical carcinogenesis, HPV proteins seem to interact with both miR-34a and miR-125b changing its expression and promoting persistent infection and cervical cancer development. In this review we describe the potential role of miR-125b and miR-34a in cervical carcinogenesis, including interaction with HPV and mechanism of deregulation. Additionally, their clinical applications in cervical cancer as prognostic/predictive biomarkers are also briefly discussed.

Increased exosomal microRNA-21 and microRNA-146a levels in the cervicovaginal lavage specimens of patients with cervical cancer

Well-run screening programs for cervical cancer in the population at risk have been shown to result in a sharp decrease in the incidence and mortality of cervical cancer in a number of large populations. Expression patterns of a recently identified biomarker family, microRNA, appear to be characteristic of tumor type and developmental origin. Several tumors have been reported to actively release exosomes carrying microRNAs. The present study has determined the association of microRNAs with cervical cancer-derived exosomes. The cervical cancer-derived exosomes were enriched in the cervicovaginal lavages specimens and the abundance of exosomes and exosomal microRNAs was detected by electron microscopy, western blot analysis, RT-qPCR and microRNA target reporter vector. The microRNA-21 and microRNA-146a, which were up-regulated in cervical cancer patients, were associated with the high levels of cervical cancer-derived exosomes. In conclusion, we demonstrated the abundance of exosomes in the cervicovaginal lavage specimens of women with cervical cancer. Furthermore, our results indicated that abnormally high levels of microRNA-21 and microRNA-146a existed in the cervical cancer-derived exosomes and the two microRNAs were functional in 293T cells.

Molecular targets of HPV oncoproteins: potential biomarkers for cervical carcinogenesis

Cervical cancer is the second most common cancer among women worldwide and is responsible for 275,000 deaths each year. Persistent infection with high-risk human papillomavirus (HR-HPV) is an essential factor for the development of cervical cancer. Although the process is not fully understood, molecular mechanisms caused by HPV infection are necessary for its development and reveal a large number of potential biomarkers for diagnosis and prognosis. These molecules are host genes and/or proteins, and cellular microRNAs involved in cell cycle regulation that result from disturbed expression of HR-HPV E5, E6 and E7 oncoproteins. One of the current challenges in medicine is to discover potent biomarkers that can correctly diagnose cervical premalignant lesions and standardize clinical management. Currently, studies are showing that some of these molecules are potential biomarkers of cervical carcinogenesis, and it is possible to carry out a more accurate diagnosis and provide more appropriate follow-up treatment for women with cervical dysplasia. In this paper, we review recent research studies on cell cycle molecules deregulated by HPV infections, as well as their potential use for cervical cancer screening.

Deregulation of the miRNAs expression in cervical cancer: human papillomavirus implications

MicroRNAs (miRNAs) are a class of small non coding RNAs of 18-25 nucleotides in length. The temporal or short-lived expression of the miRNAs modulates gene expression post transcriptionally. Studies have revealed that miRNAs deregulation correlates and is involved with the initiation and progression of human tumors. Cervical cancer (CC) displays notably increased or decreased expression of a large number of cellular oncogenic or tumor suppressive miRNAs, respectively. However, understanding the potential role of miRNAs in CC is still limited. In CC, the high-risk human papillomaviruses (HR-HPVs) infection can affect the miRNAs expression through oncoprotein E6 and E7 that contribute to viral pathogenesis, although other viral proteins might also be involved. This deregulation in the miRNAs expression has an important role in the hallmarks of CC. Interestingly, the miRNA expression profile in CC can discriminate between normal and tumor tissue and the extraordinary stability of miRNAs makes it suitable to serve as diagnostic and prognostic biomarkers of cancer. In this review, we will summarize the role of the HR-HPVs in miRNA expression, the role of miRNAs in the hallmarks of CC, and the use of miRNAs as potential prognostic biomarkers in CC.

High expression of ezrin predicts poor prognosis in uterine cervical cancer

Background

Ezrin, a member of the ezrin/radixin/moesin (ERM) protein family, plays a pivotal role in tumor invasion and metastasis. This study is aimed to investigate the clinicopathological significance of upregulated ezrin protein expression in uterine cervical cancers.

Methods

Immunohistochemical staining of ezrin protein was performed on uterine cervical cancer specimens from 235 patients. For comparison, 239 cases of cervical intraepithelial neoplasia (CIN), 17 cases of cervical glandular intraepithelial neoplasia (CGIN) and 52 normal cervix samples were also included. qRT-PCR was performed on fresh tissues to detect ezrin mRNA expression levels. HPV infection statuses were genotyped by oligonucleotide microarray, and 10-year survival rates were calculated using the Kaplan-Meier method for 109 cervical cancer patients.

Results

Apical membranous distribution of ezrin protein was only observed in normal cervical glands, while perinuclear staining was only observed in cervical cancers. Strong cytoplasmic and diffuse localization of ezrin were frequently seen in the cervical cancers compared with the normal counterparts. Furthermore, this strongly positive ezrin expression was significantly higher in cervical cancers than in CIN, CGIN, and normal cervical epithelia. Ezrin overexpression was closely related with poor differentiation, late stage, and lymph node metastasis. Additionally, ezrin overexpression was associated with lower 10-year survival rate for patients with early stage cervical cancer, but not for patients with advanced stage.

Conclusions

Aberrant localization and overexpression of ezrin might be an independent effective biomarker for prognostic evaluation of cervical cancers.

The polymorphism in the let-7 targeted region of the Lin28 gene is associated with increased risk of type 2 diabetes mellitus

Genetic polymorphisms in the miRNAs pathway of the pathogenesis of disease might contribute to the risk of disease. However, it is unclear whether these polymorphisms about miRNAs are associated with the risk of type 2 diabetes mellitus (T2DM). We performed a case-control study to investigate two polymorphisms in the let-7/Lin28 pathway based on 588 T2DM patients and 588 age and sex matched controls. The results showed that the rs3811463 polymorphism was associated with increased risk of T2DM (odds ratio (OR)=1.47, 95% confidence inference (95%CI)=1.13-1.93, P=0.005), while the rs3811464 not (OR=1.04, 95%CI=0.79-1.36, P=0.78). For the rs3811463 polymorphism, the variant genotypes were associated with increased risk of disease in females; statistically differences were observed in the clinical features of age at diagnosis, hypertension and peripheral neuropathy for the variant and wild genotype of the rs3811463 in T2DM. In summary, the results indicated that the rs3811463 polymorphism in the let-7/Lin28 pathway could significantly increase the risk of T2DM.

Identification and validation of human papillomavirus encoded microRNAs

We report here identification and validation of the first papillomavirus encoded microRNAs expressed in human cervical lesions and cell lines. We established small RNA libraries from ten human papillomavirus associated cervical lesions including cancer and two human papillomavirus harboring cell lines. These libraries were sequenced using SOLiD 4 technology. We used the sequencing data to predict putative viral microRNAs and discovered nine putative papillomavirus encoded microRNAs. Validation was performed for five candidates, four of which were successfully validated by qPCR from cervical tissue samples and cell lines: two were encoded by HPV 16, one by HPV 38 and one by HPV 68. The expression of HPV 16 microRNAs was further confirmed by in situ hybridization, and colocalization with p16INK4A was established. Prediction of cellular target genes of HPV 16 encoded microRNAs suggests that they may play a role in cell cycle, immune functions, cell adhesion and migration, development, and cancer. Two putative viral target sites for the two validated HPV 16 miRNAs were mapped to the E5 gene, one in the E1 gene, two in the L1 gene and one in the LCR region. This is the first report to show that papillomaviruses encode their own microRNA species. Importantly, microRNAs were found in libraries established from human cervical disease and carcinoma cell lines, and their expression was confirmed in additional tissue samples. To our knowledge, this is also the first paper to use in situ hybridization to show the expression of a viral microRNA in human tissue.

Nip the HPV encoded evil in the cancer bud: HPV reshapes TRAILs and signaling landscapes

HPV encoded proteins can elicit ectopic protein–protein interactions that re-wire signaling pathways, in a mode that promotes malignancy. Moreover, accumulating data related to HPV is now providing compelling substantiation of a central role played by HPV in escaping immunosurveillance and impairment of apoptotic response. What emerges is an intricate network of Wnt, TGF, Notch signaling cascades that forms higher-order ligand–receptor complexes routing downstream signaling in HPV infected cells. These HPV infected cells are regulated both extracellularly by ligand receptor axis and intracellularly by HPV encoded proteins and impair TRAIL mediated apoptosis. We divide this review into different sections addressing how linear signaling pathways integrate to facilitate carcinogenesis and compounds that directly or indirectly reverse these aberrant interactions offer new possibilities for therapy in cancer. Although HPV encoded proteins mediated misrepresentation of pathways is difficult to target, improved drug-discovery platforms and new technologies have facilitated the discovery of agents that can target dysregulated pathways in HPV infected cervical cancer cells, thus setting the stage for preclinical models and clinical trials.

Towards incorporating epigenetic mechanisms into carcinogen identification and evaluation

Remarkable progress in the field of epigenetics has turned academic, medical and public attention to the potential applications of these new advances in medicine and various fields of biomedical research. The result is a broader appreciation of epigenetic phenomena in the a etiology of common human diseases, most notably cancer. These advances also represent an exciting opportunity to incorporate epigenetics and epigenomics into carcinogen identification and safety assessment. Current epigenetic studies, including major international sequencing projects, are expected to generate information for establishing the 'normal' epigenome of tissues and cell types as well as the physiological variability of the epigenome against which carcinogen exposure can be assessed. Recently, epigenetic events have emerged as key mechanisms in cancer development, and while our search of the Monograph Volume 100 revealed that epigenetics have played a modest role in evaluating human carcinogens by the International Agency for Research on Cancer (IARC) Monographs so far, epigenetic data might play a pivotal role in the future. Here, we review (i) the current status of incorporation of epigenetics in carcinogen evaluation in the IARC Monographs Programme, (ii) potential modes of action for epigenetic carcinogens, (iii) current in vivo and in vitro technologies to detect epigenetic carcinogens, (iv) genomic regions and epigenetic modifications and their biological consequences and (v) critical technological and biological issues in assessment of epigenetic carcinogens. We also discuss the issues related to opportunities and challenges in the application of epigenetic testing in carcinogen identification and evaluation. Although the application of epigenetic assays in carcinogen evaluation is still in its infancy, important data are being generated and valuable scientific resources are being established that should catalyse future applications of epigenetic testing.

miRNA expression profiling of inflammatory breast cancer identifies a 5-miRNA signature predictive of breast tumor aggressiveness

IBC (inflammatory breast cancer) is a rare but very aggressive form of breast cancer with a particular phenotype. The molecular mechanisms responsible for IBC remain largely unknown. In particular, genetic and epigenetic alterations specific to IBC remain to be identified. MicroRNAs, a class of small noncoding RNAs able to regulate gene expression, are deregulated in breast cancer and may therefore serve as tools for diagnosis and prediction. This study was designed to determine miRNA expression profiling (microRNAome) in IBC. Quantitative RT-PCR was used to determine expression levels of 804 miRNAs in a screening series of 12 IBC compared to 31 non-stage-matched non-IBC and 8 normal breast samples. The differentially expressed miRNAs were then validated in a series of 65 IBC and 95 non-IBC. From a set of 18 miRNAs of interest selected from the screening series, 13 were differentially expressed with statistical significance in the validation series of IBC compared to non-IBC. Among these, a 5-miRNA signature comprising miR-421, miR-486, miR-503, miR-720 and miR-1303 was shown to be predictive for IBC phenotype with an overall accuracy of 89%. Moreover, multivariate analysis showed that this signature was an independent predictor of poor Metastasis-Free Survival in non-IBC patients.

Human papillomaviruses modulate microRNA 145 expression to directly control genome amplification

Human papillomaviruses (HPVs) modulate expression of host microRNAs. Our deep-sequencing analysis of organotypic raft cultures identified microRNA 145 (miR-145) as a differentiation-dependent microRNA that has functionally active target sequences in the HPV-31 E1 and E2 open reading frames. Overexpression of miR-145 in HPV-positive cells resulted in reduced genome amplification and late gene expression, along with decreased levels of cellular transcription factor KLF-4. Our studies show that HPV modulates miR-145 expression to control its own life cycle.

A Decade of Global mRNA and miRNA Profiling of HPV-Positive Cell Lines and Clinical Specimens

For more than a decade, global gene expression profiling has been extensively used to elucidate the biology of human papillomaviruses (HPV) and their role in cervical- and head-and-neck cancers. Since 2008, the expression profiling of miRNAs has been reported in multiple HPV studies. Two major strategies have been employed in the gene and miRNA profiling studies: In the first approach, HPV positive tumors were compared to normal tissues or to HPV negative tumors. The second strategy relied on analysis of cell cultures transfected with single HPV oncogenes or with HPV genomes compared to untransfected cells considered as models for the development of premalignant and malignant transformations.In this review, we summarize what we have learned from a decade of global expression profiling studies. We performed comprehensive analysis of the overlap of the lists of differentially expressed genes and microRNAs, in both tissue samples and cell culture based studies. The review focuses mainly on HPV16, however reports from other HPV species are used as references. We discuss the low degree of consensus among different studies and the limitation of differential expression analysis as well as the fragmented miRNA-mRNA target correlation evidence. Furthermore, we propose an approach for future research to include more comprehensive miRNA-mRNA target correlation analysis and to apply systems biology/gene networks methodology.

Cell culture model predicts human disease: Altered expression of junction proteins and matrix metalloproteinases in cervical dysplasia

BACKGROUND

Cervical cancer is necessarily caused by human papillomaviruses, which encode three oncogenes manifesting their functions by interfering with a number of cellular proteins and pathways: the E5, E6, and E7 proteins. We have earlier found in our microarray studies that the E5 oncogene crucially affects the expression of cellular genes involved in adhesion and motility of epithelial cells.

METHODS

In order to biologically validate our previous experimental findings we performed immunohistochemical staining of a representative set of tissue samples from different grades of high-risk human papillomavirus associated cervical disease as well as normal squamous and columnar cervical epithelium. Three-dimensional collagen raft cultures established from E5-expressing and control epithelial cells were also examined. The expression of p16, matrix metalloproteinase (MMP) -7, MMP-16, cytokeratin (CK) 8/18, laminin, E-cadherin and beta-catenin was studied.

RESULTS

In agreement with our previous microarray studies, we found intense staining for E-cadherin and beta-catenin in adherens junctions even in high-grade cervical lesions. Staining for MMP-16 was increased in severe disease as well. No significant change in staining for MMP-7 and cytokeratin 8/18 along with the grade of cervical squamous epithelial disease was observed.

CONCLUSIONS

Here we have confirmed, using tissue material from human papillomavirus associated lesions, some of the cellular gene expression modifications that we earlier reported in an experimental system studying specifically the E5 oncogene of papillomaviruses. These findings were partially surprising in the context of cervical carcinogenesis and emphasize that the complexity of carcinogenesis is not yet fully understood. Microarray approaches provide a wide overwiev of gene expression in experimental settings, which may yield biologically valid biomarkers for disease diagnostics, prognosis, and follow-up.

The microRNA regulatory network in normal- and HTLV-1-transformed T cells

Recent efforts to understand the molecular networks governing normal T cell development and driving the neoplastic transformation of T cells have brought to light the involvement of microRNAs (miRNAs), a class of noncoding RNAs of approximately 22 nucleotides that regulate gene expression at the posttranscriptional level. In the present review, we compare the expression profiles of miRNAs in normal T cell development to that of transformed T cells using as a model adult T cell leukemia/lymphoma, an aggressive malignancy of mature CD4+ T cells that is caused by infection with human T cell leukemia virus type 1.

Virology and molecular pathogenesis of HPV (human papillomavirus)-associated oropharyngeal squamous cell carcinoma

The current literature fully supports HPV (human papillomavirus)-associated OPSCC (oropharyngeal squamous cell carcinoma) as a unique clinical entity. It affects an unambiguous patient population with defined risk factors, has a genetic expression pattern more similar to cervical squamous cell carcinoma than non-HPV-associated HNSCC (head and neck squamous cell carcinoma), and may warrant divergent clinical management compared with HNSCC associated with traditional risk factors. However, a detailed understanding of the molecular mechanisms driving these differences and the ability to exploit this knowledge to improve clinical management of OPSCC has not yet come to fruition. The present review summarizes the aetiology of HPV-positive (HPV+) OPSCC and provides a detailed overview of HPV virology and molecular pathogenesis relevant to infection of oropharyngeal tissues. Methods of detection and differential gene expression analyses are also summarized. Future research into mechanisms that mediate tropism of HPV to oropharyngeal tissues, improved detection strategies and the pathophysiological significance of altered gene and microRNA expression profiles is warranted.

Productive Lifecycle of Human Papillomaviruses that Depends Upon Squamous Epithelial Differentiation

Human papillomaviruses (HPVs) target the stratified epidermis, and can causes diseases ranging from benign condylomas to malignant tumors. Infections of HPVs in the genital tract are among the most common sexually transmitted diseases, and a major risk factor for cervical cancer. The virus targets epithelial cells in the basal layer of the epithelium, while progeny virions egress from terminally differentiated cells in the cornified layer, the surface layer of the epithelium. In infected basal cells, the virus maintains its genomic DNA at low-copy numbers, at which the viral productive lifecycle cannot proceed. Progression of the productive lifecycle requires differentiation of the host cell, indicating that there is tight crosstalk between viral replication and host differentiation programs. In this review, we discuss the regulation of the HPV lifecycle controlled by the differentiation program of the host cells.

Cellular transformation by human papillomaviruses: lessons learned by comparing high- and low-risk viruses

The oncogenic potential of papillomaviruses (PVs) has been appreciated since the 1930s yet the mechanisms of virally-mediated cellular transformation are still being revealed. Reasons for this include: a) the oncoproteins are multifunctional, b) there is an ever-growing list of cellular interacting proteins, c) more than one cellular protein may bind to a given region of the oncoprotein, and d) there is only limited information on the proteins encoded by the corresponding non-oncogenic PVs. The perspective of this review will be to contrast the activities of the viral E6 and E7 proteins encoded by the oncogenic human PVs (termed high-risk HPVs) to those encoded by their non-oncogenic counterparts (termed low-risk HPVs) in an attempt to sort out viral life cycle-related functions from oncogenic functions. The review will emphasize lessons learned from the cell culture studies of the HPVs causing mucosal/genital tract cancers.