Both episomal and integrated forms of human papillomavirus type 16 are involved in invasive cervical cancers

The Hallmarks of Cervical Cancer: Molecular Mechanisms Induced by Human Papillomavirus

Human papillomaviruses (HPVs) and, specifically, high-risk HPVs (HR-HPVs) are identified as necessary factors in the development of cancer of the lower genital tract, with CaCU standing out as the most prevalent tumor. This review summarizes ten mechanisms activated by HR-HPVs during cervical carcinogenesis, which are broadly associated with at least seven of the fourteen distinctive physiological capacities of cancer in the newly established model by Hanahan in 2022. These mechanisms involve infection by human papillomavirus, cellular tropism, genetic predisposition to uterine cervical cancer (CaCU), viral load, viral physical state, regulation of epigenetic mechanisms, loss of function of the E2 protein, deregulated expression of E6/E7 oncogenes, regulation of host cell protein function, and acquisition of the mesenchymal phenotype.

Papillomaviruses and cancer: commonalities and differences in HPV carcinogenesis at different sites of the body

Human papillomavirus (HPV) is associated with 5% of all cancers globally at a range of body sites, including cervix, anus, penis, vagina, vulva, and oropharynx. These cancers claim > 400,000 lives annually. The persistent infection of HPV and the function of viral oncogenes are the primary causes of HPV-related cancers. However, only some HPV-infected persons or infected lesions will progress to cancer, and the burden of HPV-associated cancer varies widely according to gender and the part of the body infected. The dissimilarity in infection rates at different sites can explain only a small part of the differences observed. Much responsibility likely sits with contributions of specific epithelial cells and the cellular microenvironment at infected sites to the process of malignant transformation, both of which affect the regulation of viral gene expression and the viral life cycle. By understanding the biology of these epithelial sites, better diagnosis/treatment/management of HPV-associated cancer and/or pre-cancer lesions will be provided.

The Tumor-Specific Immune Landscape in HPV+ Head and Neck Cancer

Human papillomaviruses (HPVs) are the causative agent of several anogenital cancers as well as head and neck cancers, with HPV+ head and neck squamous cell carcinoma (HNSCC) becoming a rapidly growing public health issue in the Western world. Due its viral etiology and potentially its subanatomical location, HPV+ HNSCC exhibits an immune microenvironment which is more inflamed and thus distinct from HPV-negative HNSCC. Notably, the antigenic landscape in most HPV+ HNSCC tumors extends beyond the classical HPV oncoproteins E6/7 and is extensively targeted by both the humoral and cellular arms of the adaptive immune system. Here, we provide a comprehensive overview of HPV-specific immune responses in patients with HPV+ HNSCC. We highlight the localization, antigen specificity, and differentiation states of humoral and cellular immune responses, and discuss their similarities and differences. Finally, we review currently pursued immunotherapeutic treatment modalities that attempt to harness HPV-specific immune responses for improving clinical outcomes in patients with HPV+ HNSCC.

Topological implications of DNA tumor viral episomes

A persistent DNA tumor virus infection transforms normal cells into cancer cells by either integrating its genome into host chromosomes or retaining it as an extrachromosomal entity called episome. Viruses have evolved mechanisms for attaching episomes to infected host cell chromatin to efficiently segregate the viral genome during mitosis. It has been reported that viral episome can affect the gene expression of the host chromosomes through interactions between viral episomes and epigenetic regulatory host factors. This mini review summarizes our current knowledge of the tethering sites of viral episomes, such as EBV, KSHV, and HBV, on host chromosomes analyzed by three-dimensional genomic tools. [BMB Reports 2022; 55(12): 587-594].

The Diagnostic Value of Circulating Cell-Free HPV DNA in Plasma from Cervical Cancer Patients

Circulating cell-free HPV DNA (ccfHPV DNA) may serve as a marker for cervical cancer. In this study, we used digital droplet PCR (ddPCR) to detect and quantify ccfHPV DNA in plasma from patients with HPV16- or HPV18-associated cervical cancer. Blood samples from 60 patients diagnosed with cervical cancer (FIGO IA1-IVA) at Aarhus or Odense University Hospital (June 2018 to March 2020) were collected prior to treatment, and patients were subdivided into an early stage (n = 30) and a late-stage subgroup (n = 30) according to disease stage. Furthermore, blood samples from eight women with HPV16- or 18-associated premalignant conditions (CIN3), and 15 healthy controls were collected. ddPCR was used to analyze plasma from all participants. ccfHPV DNA was detected in 19 late-stage patients (63.33%), 3 early stage patients (10.00%), and none of the CIN3 patients or controls. Quantitative evaluation showed significant correlations between ccfHPV DNA level and stage, tumor score, and tumor size. Thus, our results indicate that ccfHPV DNA may not be a useful marker for early detection of cervical cancer. However, for patients with advanced stage cervical cancer, ccfHPV DNA level represents a promising tool to establish tumor burden, making it useful for establishing treatment response and monitoring the disease.

High-Risk Human Papillomavirus Oncogenic E6/E7 mRNAs Splicing Regulation

High-risk human papillomavirus infection may develop into a persistent infection that is highly related to the progression of various cancers, including cervical cancer and head and neck squamous cell carcinomas. The most common high-risk subtypes are HPV16 and HPV18. The oncogenic viral proteins expressed by high-risk HPVs E6/E7 are tightly involved in cell proliferation, differentiation, and cancerous transformation since E6/E7 mRNAs are derived from the same pre-mRNA. Hence, the alternative splicing in the E6/E7-coding region affects the balance of the E6/E7 expression level. Interrupting the balance of E6 and E7 levels results in cell apoptosis. Therefore, it is crucial to understand the regulation of E6/E7 splice site selection and the interaction of splicing enhancers and silencers with cellular splicing factors. In this review, we concluded the relationship of different E6/E7 transcripts with cancer progression, the known splicing sites, and the identified cis-regulatory elements within high-risk HPV E6/E7-coding region. Finally, we also reviewed the role of various splicing factors in the regulation of high-risk HPV oncogenic E6/E7 mRNA splicing.

Integrated analysis of virus and host transcriptomes in cervical cancer in Asian and Western populations

Race may influence vulnerability to HPV variants in viral infection and perisistence. Integrated analysis of the virus and host transcriptomes from different populations provides an unprecedented opportunity to understand these racial disparities in the prevalence of HPV and cervical cancers. We performed RNA-Seq analysis of 90 tumors and 39 adjacent normal tissues from cervical cancer patients at Zhejiang University (ZJU) in China, and conducted a comparative analysis with RNA-Seq data of 286 cervical cancers from TCGA. We found a modestly higher rate of HPV positives and HPV integrations in TCGA than in ZJU. In addition to LINC00393 and HSPB3 as new common integration hotspots in both cohorts, we found new hotspots such as SH2D3C and CASC8 in TCGA, and SCGB1A1 and ABCA1 in ZJU. We described the first, to our knowledge, virus-transcriptome-based classification of cervical cancer associated with clinical outcome. Particularly, patients with expressed E5 performed better than those without E5 expression. However, the constituents of these virus-transcriptome-based tumor subtypes differ dramatically between the two cohorts. We further characterized the immune infiltration landscapes between different HPV statuses and revealed significantly elevated levels of regulatory T cells and M0 macrophages in HPV positive tumors, which were associated with poor prognosis. These findings increase our understanding of the racial disparities in the prevalence of HPV and its associated cervical cancers between the two cohorts, and also have important implications in the classification of tumor subtypes, prognosis, and anti-cancer immunotherapy in cervical cancer.

Perspectives in HPV Secondary Screening and Personalized Therapy Basing on Our Understanding of HPV-Related Carcinogenesis Pathways

As cervical cancer is one of the most common malignancies in women worldwide even with present screening methods, the incidence in most developed countries is not decreasing for the last 15-20 years. A shift has been observed in the age of diagnosis in favour of younger women, and treatment of already developed cervical cancer is a challenge for surgeons. It is imperative to find new diagnostic methods for accurately pointing out patients at high risk of developing malignant disease and developing personalized treatment. Since cervical cancer is almost exclusively associated with HPV infection, understanding changes happening in an infected cell may prove invaluable for search of such methods, but it may also prove helpful in the diagnosis and treatment of other anogenital and nasopharyngeal region cancers. This review follows HPV-related changes in infected cell biology to point what potential markers and targets for therapy are in option when dealing with HPV-related diseases.

E5 can be expressed in anal cancer and leads to epidermal growth factor receptor-induced invasion in a human papillomavirus 16-transformed anal epithelial cell line

We created the first human papillomavirus (HPV)-16-immortalized anal epithelial cell line, known as AKC2 cells to establish an in vitro model of HPV-16-induced anal carcinogenesis. Consistent with detection of E6, E7 and E5 expression in anal cancer biopsies, AKC2 cells expressed high levels of all three HPV oncogenes. Also, similar to findings in anal cancer biopsies, epidermal growth factor receptor (EGFR) was overexpressed in AKC2 cells. AKC2 cells exhibited a poorly differentiated and invasive phenotype in three-dimensional raft culture and inhibition of EGFR function abrogated AKC2 invasion. Reducing E5 expression using E5-targeted siRNAs in AKC2 cells led to knockdown of E5 expression, but also HPV-16 E2, E6 and E7 expression. AKC2 cells treated with E5-targeted siRNA had reduced levels of total and phosphorylated EGFR, and reduced invasion. Rescue of E6/E7 expression with simultaneous E5 knockdown confirmed that E5 plays a key role in EGFR overexpression and EGFR-induced invasion.

Folate Deficiency Facilitates Genomic Integration of Human Papillomavirus Type 16 DNA In Vivo in a Novel Mouse Model for Rapid Oncogenic Transformation of Human Keratinocytes

Background

Epidemiologic and in vitro studies suggest independent linkages between poor folate and/or vitamin B-12 nutrition, genomic human papillomavirus (HPV) type 16 viral integration, and cancer. However, there is no direct evidence in vivo to support the causative role of poor folate nutrition in HPV16 integration into the cellular genome.

Objective

We tested the hypothesis that folate deficiency enables the integration of HPV16 into the genome of HPV16-harboring keratinocytes, and could thereby influence earlier transformation of these cells to cancer in an animal model.

Methods

HPV16-harboring human keratinocytes [(HPV16)BC-1-Ep/SL] were differentiated into 3-dimensional HPV16-organotypic rafts under either folate-replete or folate-deficient conditions in vitro. These were then subcutaneously implanted in severely immunocompromised female Beige Nude XID (Hsd: NIHS-LystbgFoxn1nuBtkxid) mice (4-6 wk old, 16-18 g) fed either a folate-replete diet (1200 nmol folate/kg diet) or a progressively folate-deficient diet (600 or 400 nmol folate/kg diet) for 2 mo prior to raft-implantation surgery, and indefinitely thereafter. The tumors that subsequently developed were characterized for onset, pattern of growth, morphology, HPV16 oncogene expression, and HPV16-genomic integration.

Results

All HPV16-organotypic rafts developed in either folate-replete or physiologic low-folate media in vitro and subsequently implanted in folate-replete mice eventually transformed into aggressive malignancies within weeks. When compared to HPV16-high folate-organotypic raft-derived tumors from mice fed either a 1200 or 600 nmol folate/kg diet, those raft-derived cancers that developed in mice fed a 400 nmol folate/kg diet expressed significantly more HPV16 E6 (1.8-fold more) and E7 (2.8-fold more) oncogenic proteins (P = 0.001), and revealed significantly more HPV16-integration sites in genomic DNA (2-fold more), either directly into, or in the vicinity of, cellular genes (P < 0.05).

Conclusions

This unprecedented animal model for the consistent rapid transformation of differentiated (HPV16)BC-1-Ep/SL-derived organotypic raft-keratinocytes to cancer in Beige Nude XID mice confirms that dietary folate deficiency can profoundly influence and modulate events leading to HPV16-induced carcinogenesis, and facilitates genomic integration of HPV16 DNA in vivo.

Cytokeratin7 and cytokeratin19 expression in high grade cervical intraepithelial neoplasm and squamous cell carcinoma and their possible association in cervical carcinogenesis

Background

High risk human papillomavirus (HR HPV) infects cells at the squamocolumnar junction (SCJ) of the cervix, causing cancer. Cytokeratin (CK)7 is an SCJ marker, and stains cervical neoplasia. CK19 is a binding partner of CK7 and expressed in cervical cancer. Despite this possible association between CK7/CK19 and cervical cancer, not much is known about the mechanism of CK7/CK19 involvement in HR HPV-mediated cervical carcinogenesis.

Methods

We analyzed the expression pattern of CK7, CK19, and p16 by using immunohistochemistry and HPV infection by in situ hybridization in 25 cases of high grade cervical intraepithelial neoplasia (CIN3) and in 30 cases of squamous cell carcinoma (SCC).

Results

CK19, p16, and HPV expression was positive in all CIN3 and SCC cases. CK7 expression was positive in all CIN3 cases and in 20/30 (66%) SCCs. Each protein showed diffuse or patchy staining with topographic distinction. Patchy staining of CK7 and episomal HPV DNA overlapped in the upper layer of CIN3 and central portion of an invasive nest in the SCC, whereas patchy CK19 staining and integrated HPV DNA were usually noted in the lower layer of CIN3 and the periphery of the SCC nest. The p16 staining pattern coincided with that of CK19 in a subset of SCC.

Conclusion

These results suggest that CK7 may be more related with viral episomal replication and CK19 with viral integration, contributing to viral replication and malignant transformation in HR HPV infected cells. In addition, coordinate CK7/CK19 staining may be used as a valuable marker for predicting physical status of HR HPV and E7 oncoprotein level in cervical tumor.

Electronic supplementary material

The online version of this article (doi:10.1186/s13000-017-0609-4) contains supplementary material, which is available to authorized users.

Human papillomavirus molecular biology

Human papillomaviruses are small DNA viruses with a tropism for squamous epithelia. A unique aspect of human papillomavirus molecular biology involves dependence on the differentiation status of the host epithelial cell to complete the viral lifecycle. A small group of these viruses are the etiologic agents of several types of human cancers, including oral and anogenital tract carcinomas. This review focuses on the basic molecular biology of human papillomaviruses.

Human papillomavirus molecular biology and disease association

Human papillomaviruses (HPVs) have evolved over millions of years to propagate themselves in a range of different animal species including humans. Viruses that have co‐evolved slowly in this way typically cause chronic inapparent infections, with virion production in the absence of apparent disease. This is the case for many Beta and Gamma HPV types. The Alpha papillomavirus types have however evolved immunoevasion strategies that allow them to cause persistent visible papillomas. These viruses activate the cell cycle as the infected epithelial cell differentiates in order to create a replication competent environment that allows viral genome amplification and packaging into infectious particles. This is mediated by the viral E6, E7, and E5 proteins. High‐risk E6 and E7 proteins differ from their low‐risk counterparts however in being able to drive cell cycle entry in the upper epithelial layers and also to stimulate cell proliferation in the basal and parabasal layers. Deregulated expression of these cell cycle regulators underlies neoplasia and the eventual progression to cancer in individuals who cannot resolve high‐risk HPV infection. Most work to date has focused on the study of high‐risk HPV types such as HPV 16 and 18, which has led to an understanding of the molecular pathways subverted by these viruses. Such approaches will lead to the development of better strategies for disease treatment, including targeted antivirals and immunotherapeutics. Priorities are now focused toward understanding HPV neoplasias at sites other than the cervix (e.g. tonsils, other transformation zones) and toward understanding the mechanisms by which low‐risk HPV types can sometimes give rise to papillomatosis and under certain situations even cancers. Copyright © 2015 John Wiley & Sons, Ltd.

The E5 proteins

The E5 proteins are short transmembrane proteins encoded by many animal and human papillomaviruses. These proteins display transforming activity in cultured cells and animals, and they presumably also play a role in the productive virus life cycle. The E5 proteins are thought to act by modulating the activity of cellular proteins. Here, we describe the biological activities of the best-studied E5 proteins and discuss the evidence implicating specific protein targets and pathways in mediating these activities. The primary target of the 44-amino acid BPV1 E5 protein is the PDGF β receptor, whereas the EGF receptor appears to be an important target of the 83-amino acid HPV16 E5 protein. Both E5 proteins also bind to the vacuolar ATPase and affect MHC class I expression and cell-cell communication. Continued studies of the E5 proteins will elucidate important aspects of transmembrane protein-protein interactions, cellular signal transduction, cell biology, virus replication, and tumorigenesis.

Significance of binucleated cells with compression in atypical squamous cells of undetermined significance

OBJECTIVE

To increase the accuracy of the diagnosis of atypical squamous cells of undetermined significance (ASC-US), ASC-US were divided into high-risk human papillomavirus (HPV HR+) and non-high-risk HPV (HPV HR-) cases to analyze the significance of binucleated cells with compression.

STUDY DESIGN

ThinPrep specimens of ASC-US were examined. This study included 21 CIN and HPV HR+ (CIN+), 19 benign and HPV HR- (B-) and 10 benign and HPV HR+ (B+) cases. The number of cells were examined by defining binucleated cells with their nuclei pressing against each other as positive compression, and their relation to the relative light units (RLUs) of the DNA Hybrid capture 2 (HC2) was determined.

RESULTS

95.2% of CIN+ and 15.8% of B- cases were compression positive, while 4.8% of CIN+ and 84.2% of B- cases were compression negative, which was significantly different. The average number of cells with positive compression was 5.7 ± 5.3 in CIN+, 2.0 ± 0.7 in B- and 5.5 ± 1.5 in B+ cases, with significant differences between CIN+ and B- and between B- and B+ cases. The number of compression-positive cells increased as HPV HC2 RLUs became higher.

CONCLUSION

Positive compression is useful in determining ASC-US with HPV HR+. The identification of positive compression is highly practical because it can be observed morphologically.

Human Papillomavirus 16 E6/E7 Transcript and E2 Gene Status in Patients with Cervical Neoplasia

BACKGROUND

The viral transforming genes E6 and E7 of human papillomavirus (HPV) 16 cause the degradation of tumor suppressor proteins. Expression of these oncoproteins increases following the integration of viral DNA into the host cell, resulting in the disruption of the E2 open reading frame (ORF).

AIM

To detect and correlate HPV-16 oncogene transcripts and HPV-16 E2 DNA in cervical biopsies obtained from women (n = 68) with cervical neoplasia.

METHODS

HPV-16 E6/E7 transcript and HPV-16 E2 DNA detection was performed on the cervical biopsies of 42 women positive for HPV-16 (36 with invasive cervical carcinoma and 6 with cervical intraepithelial neoplasia [CIN]). PCR was used to detect HPV DNA in cervical biopsies then restriction fragment length polymorphism (RFLP) was used to type the HPV DNA. Reverse-transcription (RT)-PCR for HPV-16 E6/E7 oncogene mRNA transcripts and a PCR to detect the HPV-16 E2 DNA was performed on HPV-16-positive samples.

RESULTS

HPV-16 E6/E7 mRNA transcripts were not detected in any of the CIN I or II biopsies, but were detected in all cases of CIN III and invasive cancer in different combinations (E6 alone, E6*I, E6*I/E6*II, E6/E6*I/E6*II) except for one patient with stage IIB cancer treated with radiotherapy. The incidence of episomal E2 DNA was high in this study with 52.4% of the samples positive for episomal E2. It was even detected in patients with advanced stage cancer with 50%, 42%, and 66.6% of samples positive in stages IIB, IIIB, and IV, respectively.

DISCUSSION

HPV-16 E6/E7 mRNA oncogene transcripts, in various combinations, were uniformly detectable in the majority of the high-grade cervical lesions examined. Intact episomal E2 DNA was seen in a high proportion of samples, even from advanced cervical lesions. Conservation of the E2 gene with concomitant expression of viral oncogenes in advanced cervical lesions may point to alternate mechanisms, other than integration, bringing about the enhanced expression of E6/E7 mRNA.

CONCLUSIONS

This study suggests that the detection of the HPV-16 oncogene transcripts could serve as an indicator for assessing the prognosis of patients on radiotherapy. The majority of HPV-16-positive cervical neoplastic lesions are transcriptionally active and express the oncogene transcripts. The increased occurrence of intact HPV-16 episomal E2 DNA in advanced lesions further substantiates the fact that the disruption of E2 ORF is not mandatory for increased oncogene expression. Thus, this study underscores the significance of investigating alternative mechanisms of oncogene expression in HPV-16.

The biology and life-cycle of human papillomaviruses

Human papillomaviruses (HPVs) comprise a diverse group, and have different epithelial tropisms and life-cycle strategies. Many HPVs are classified as low-risk, as they are only very rarely associated with neoplasia or cancer in the general population. These HPVs typically cause inapparent/inconspicuous infections, or benign papillomas, which can persist for months or years, but which are eventually resolved by the host's immune system. Low-risk HPVs are difficult to manage in immunosuppressed people and in individuals with genetic predispositions, and can give rise to papillomatosis, and in rare instances, to cancer. The high-risk HPV types are, by contrast, a cause of several important human cancers, including almost all cases of cervical cancer, a large proportion of other anogenital cancers and a growing number of head and neck tumours. The high-risk HPV types constitute a subset of the genus Alphapapillomavirus that are prevalent in the general population, and in most individuals cause only inconspicuous oral and genital lesions. Cancer progression is associated with persistent high-risk HPV infection and with deregulated viral gene expression, which leads to excessive cell proliferation, deficient DNA repair, and the accumulation of genetic damage in the infected cell. Although their life-cycle organisation is broadly similar to that of the low-risk HPV types, the two groups differ significantly in their capacity to drive cell cycle entry and cell proliferation in the basal/parabasal cell layers. This is thought to be linked, at least in part, to different abilities of the high- and low-risk E6 proteins to modulate the activity of p53 and PDZ-domain proteins, and the differential ability of the E7 proteins to target the several different members of the retinoblastoma protein family. This article forms part of a special supplement entitled "Comprehensive Control of HPV Infections and Related Diseases" Vaccine Volume 30, Supplement 5, 2012.

Some novel insights on HPV16 related cervical cancer pathogenesis based on analyses of LCR methylation, viral load, E7 and E2/E4 expressions

This study was undertaken to decipher the interdependent roles of (i) methylation within E2 binding site I and II (E2BS-I/II) and replication origin (nt 7862) in the long control region (LCR), (ii) expression of viral oncogene E7, (iii) expression of the transcript (E7-E1/E4) that encodes E2 repressor protein and (iv) viral load, in human papillomavirus 16 (HPV16) related cervical cancer (CaCx) pathogenesis. The results revealed over-representation (p<0.001) of methylation at nucleotide 58 of E2BS-I among E2-intact CaCx cases compared to E2-disrupted cases. Bisulphite sequencing of LCR revealed overrepresentation of methylation at nucleotide 58 or other CpGs in E2BS-I/II, among E2-intact cases than E2-disrupted cases and lack of methylation at replication origin in case of both. The viral transcript (E7-E1/E4) that produces the repressor E2 was analyzed by APOT (amplification of papillomavirus oncogenic transcript)-coupled-quantitative-RT-PCR (of E7 and E4 genes) to distinguish episomal (pure or concomitant with integrated) from purely integrated viral genomes based on the ratio, E7 C(T)/E4 C(T). Relative quantification based on comparative C(T) (threshold cycle) method revealed 75.087 folds higher E7 mRNA expression in episomal cases over purely integrated cases. Viral load and E2 gene copy numbers were negatively correlated with E7 C(T) (p = 0.007) and E2 C(T) (p<0.0001), respectively, each normalized with ACTB C(T), among episomal cases only. The k-means clustering analysis considering E7 C(T) from APOT-coupled-quantitative-RT-PCR assay, in conjunction with viral load, revealed immense heterogeneity among the HPV16 positive CaCx cases portraying integrated viral genomes. The findings provide novel insights into HPV16 related CaCx pathogenesis and highlight that CaCx cases that harbour episomal HPV16 genomes with intact E2 are likely to be distinct biologically, from the purely integrated viral genomes in terms of host genes and/or pathways involved in cervical carcinogenesis.

Quantitative measurement of human papillomavirus type 16 e5 oncoprotein levels in epithelial cell lines by mass spectrometry

The high-risk human papillomavirus type 16 (HPV-16) E5 protein (16E5) induces tumors in a transgenic mouse model and may contribute to early stages of cervical carcinogenesis. Although high-risk E5 expression is generally thought to be lost during the progression to cervical carcinoma following integration of HPV DNA into the host genome, episomal viral DNA has been documented in a subset of HPV-16-positive malignant lesions. Numerous studies have shown that transcripts that could potentially encode 16E5 are present in cervical biopsy specimens and cervical cancer cell lines, but the presence of E5 protein has been demonstrated in only two reports that have not been corroborated. In the present study, we show that trypsin cleavage of 16E5 generates a unique four-amino-acid C-terminal peptide (FLIT) that serves as a marker for E5 expression in transfected cells and epithelial cell lines containing integrated and episomal HPV-16 DNA. Following trypsin cleavage, reversed-phase chromatography and mass spectrometry (MS) were used to detect FLIT. Immunoprecipitation assays using a newly generated anti-16E5 antibody confirmed that 16E5 was solely responsible for the FLIT signal, and deuterated FLIT peptide provided an internal standard that enabled us to quantify the number of 16E5 molecules per cell. We show that 16E5 is expressed in the Caski but not in the SiHa cervical cancer cell line, suggesting that 16E5 may contribute to the malignant phenotype of some cervical cancers, even in cells exclusively containing an integrated HPV genome.

The HPV transcriptome in HPV16 positive cell lines

BACKGROUND

Infections with high-risk human papillomaviruses (HPV), mainly HPV type 16, can cause malignant transformation of the human cervical epithelium and cervical cancer (CxCa). Very little is known about the quantitative expression of the various HPV16 transcripts in frequently used cervical cancer cell lines.

METHODS

We have quantitatively analysed the viral transcriptome in the HPV16-transformed cell lines SiHa, CaSki, MRI-H196, MRI-H186, HPK-IA and C3. We used a nucleic acid sequence-based amplification (NASBA)-Luminex hybridisation assay quantifying spliced and unspliced HPV16 transcripts.

RESULTS

The cell lines differed in their qualitative and quantitative expression of viral transcripts depending on the physical HPV genome status. In SiHa, we found no transcripts containing the splice acceptor at nucleotide 3358 or downstream sequences. In CaSki cells virtually all viral transcripts were detected but with a reduced quantity of late transcripts. We further found that the tumorigenic phenotype of late passage HPK-IA cells may not be mediated through changes in HPV expression. In MRI-H186, HPK-IA and C3 cells very high levels of full-length early transcripts ending at the early polyadenylation signal were found. MRI-H196 expressed L1 full-length (fl) but no E5 fl RNA suggesting the presence of integrated HPV16 genomes with a disrupted E2 region and rearranged L1 DNA sequence.

CONCLUSION

Quantitative expression changes of HPV16 transcript markers correlate with the physical state of the HPV genome in HPV16 positive cervical cancer cell lines.

Diagnostic role of p16/INK4A protein in Human Papillomavirus (HPV) induced cervical dysplasia

The p16/INK4A protein is a cellular regulatory polypeptide over-expressed in the presence of high levels of the Human Papillomavirus (HPV) coded E7 protein. This review outlines the use of p16 antigen staining in cervical biopsies as well as in PAP smears summarizing the corresponding literature and commenting the authors’ own experience. The p16 antigen is a reliable marker for dysplastic cells in CINII/CINIII (HSIL) lesions as viewed in cervical biopsies. When PAP smears were examined at large scale screening for p16 antigenreactive and atypical cells, considerable variations could be found especially in ASCUS graded lesions. Therefore, the presence of p16-reactive atypical cells in PAP smears should be interpreted together with the cytological signs of dysplasia, such as the altered N/C ratio. In addition, women revealing p16-positive ASCUS/LSIL specimens should be examined for the presence of HPV DNA. Detection of HPV DNA alone, i.e. in the absence of cytological screening has a low predictive value, since the clearance of HPV may occur even in the absence of morphological alterations. Combined cytological as well as molecular follow up contributes to the efficiency of diagnostic and increases the probability of correct interpretation of the pre-cancerous lesions by non-invasive techniques.

The human papillomavirus type 16 E5 oncoprotein inhibits epidermal growth factor trafficking independently of endosome acidification

The human papillomavirus type 16 E5 oncoprotein (16E5) enhances acute, ligand-dependent activation of the epidermal growth factor receptor (EGFR) and concomitantly alkalinizes endosomes, presumably by binding to the 16-kDa "c" subunit of the V-ATPase proton pump (16K) and inhibiting V-ATPase function. However, the relationship between 16K binding, endosome alkalinization, and altered EGFR signaling remains unclear. Using an antibody that we generated against 16K, we found that 16E5 associated with only a small fraction of endogenous 16K in keratinocytes, suggesting that it was unlikely that E5 could significantly affect V-ATPase function by direct inhibition. Nevertheless, E5 inhibited the acidification of endosomes, as determined by a new assay using a biologically active, pH-sensitive fluorescent EGF conjugate. Since we also found that 16E5 did not alter cell surface EGF binding, the number of EGFRs on the cell surface, or the endocytosis of prebound EGF, we postulated that it might be blocking the fusion of early endosomes with acidified vesicles. Our studies with pH-sensitive and -insensitive fluorescent EGF conjugates and fluorescent dextran confirmed that E5 prevented endosome maturation (acidification and enlargement) by inhibiting endosome fusion. The E5-dependent defect in vesicle fusion was not due to detectable disruption of actin, tubulin, vimentin, or cytokeratin filaments, suggesting that membrane fusion was being directly affected rather than vesicle transport. Perhaps most importantly, while bafilomycin A(1) (like E5) binds to 16K and inhibits endosome acidification, it did not mimic the ability of E5 to inhibit endosome enlargement or the trafficking of EGF. Thus, 16E5 alters EGF endocytic trafficking via a pH-independent inhibition of vesicle fusion.

The role of HPV type in Recurrent Respiratory Papillomatosis

OBJECTIVE

Human Papillomavirus (HPV) 6 and 11 are the aetiological agents responsible for Recurrent Respiratory Papillomatosis (RRP). There is general consensus that HPV11 results in more aggressive disease compared to HPV6.

METHOD

Pubmed was searched using the terms respiratory papillomatosis, HPV 6 and HPV11. Comparisons were made in the outcomes of HPV6 versus HPV11 positive RRP disease.

RESULTS

There are numerous sub-types or variants of both HPV6 and HPV11. These sub-types have different activities at least in-vitro. The numbers of different HPV types within RRP tissue may be more extensive than initially appeared. This depends specifically upon the HPV types tested for.

CONCLUSION

The clinical differences between HPV6 and HPV11 disease may not be accurately predictable as these viruses exist in numerous sub-types. Also, RRP tissue may contain more than one subtype or even be co-infected with other viruses that may influence outcome. In-vitro studies upon cell lines are a reasonable starting point for evaluation of these differences.

Selective targeting of HPV-16 E6/E7 in cervical cancer cells with a potent oncolytic adenovirus and its enhanced effect with radiotherapy in vitro and vivo

Recent studies have shown that oncolytic adenovirus specifically targeted tumor cells while sparing normal cells. Here, we report a novel E1A-mutant adenovirus (M6) with antisense HPV16 E6 E7 DNA inserted into the deleted 6.7K/gp19K region of E3. The target effects of M6 on HPV16-positive cervical cancer cells were evaluated in vivo and in vitro. By using cytopathic effect (CPE) and viral replication assays, we verified M6 was competent to selectively replicate in cervical cancer cells in vitro. Moreover, we found infection of M6 was able to inhibit the expression of HPV16 E6 and E7 oncogenes and induce apoptosis of HPV16-positive cervical cancer cells. Further analysis in vitro revealed that the invasive ability of SiHa cells was significantly inhibited by M6. To determine if M6 synergized with radiotherapy-induced anti-tumor activity against HPV16-related cancer cells, we transfected SiHa cells with M6 followed by a single exposure to radiation. A significantly suppression of cell growth and induced apoptosis was observed in SiHa cells received M6 transfection combined with radiotherapy. Animal experiments showed that M6 transfection notably improved the survival of tumor-bearing mice in combination with radiotherapy, much superior to that of those treated by Adv5/dE1A plus radiation or M6 alone. These findings indicated the anti-tumoral efficacy of M6 on HPV16-positive cervical cancer cells and its synergic therapeutic application in radiation for cervical cancer.

Women with HIV are more commonly infected with non-16 and -18 high-risk HPV types

OBJECTIVE

To review and summarize evidence from clinical, translational and epidemiologic studies which have examined the clinically relevant aspects of HPV type prevalence and cervical dysplasia in HIV-infected women.

METHODS

Relevant studies were identified through a MEDLINE search. References of identified reports were also used to identify additional published articles for review.

RESULTS

HIV-infected women in different geographic regions (such as Zambia, Brazil, Rochester NY) appear to be infected with less prevalent types of HR-HPV as compared to the general population who, across all continents, are more commonly infected with types 16 and 18. Secondly, integration of HPV DNA into the host genome is no longer thought to be a necessary cause of malignant transformation of cervical cells. However, rate of integration appears to differ by the type of HPV. In fact, the types of HPV which appear to be more common in cervical dysplasia of HIV-infected women are the same types which are more likely to require integration for malignant transformation. Finally, HPV types found in HIV-infected women are relatively common and likely to persist. The most common among these types belong to the alpha-9 and -7 species which are the most carcinogenic species.

CONCLUSION

Given that current vaccines target HR-HPV-16/18, the findings from the above mentioned studies may have important implications for the design of HPV vaccines that target the types of HPV associated with disease risk in HIV-infected women. HPV typing and assessment of the physical state (whether it is integrated or episomal) appear to be two valuable parameters for the prognostic evaluation of dysplastic lesions of the uterine cervix. This, however, has not yet been assessed in HIV-infected women. Recent data about the immune response in HPV/HIV co-infection may lead to understanding potential mechanisms for less virulent HPV causing malignant transformation in HIV-infected women.

[Protection against uterine cervical cancer by HPV vaccines]

Research literature has definitively shown HPV to be a necessary cause of cervical cancer. HPV is highly prevalent in sexually active populations and its natural history is now traceable thanks to recent advances in technology. HPV-like particle can now be synthesized and assembled in vitro to constitute the major virion protein L1, and this technology has been exploited to produce HPV-L1-VLP vaccines. Now, HPV-related diseases can thus be prevented by commercially available HPV prophylactic vaccines such as Gardasil (recombinant HPV genotype 6/11/16/18) and Cervarix (recombinant HPV genotype 16/18). These advances have dramatically changed the administration of cervical cancer screening programs.

Disruption of the E2 gene is a common and early event in the natural history of cervical human papillomavirus infection: a longitudinal cohort study

Integration of high-risk human papillomavirus (HPV) types into the host-cell genome disrupts the HPV regulatory E2 protein, resulting in a loss of negative feedback control of viral oncogene expression; this disruption has been considered a critical event in the pathogenesis of cervical neoplasia, and a potential biomarker of progressive disease. However, using serial samples taken from a cohort of young women who were recruited soon after they first had sexual intercourse, we show that disruption of the E2 gene is a common and early event in the natural history of incident cervical HPV infections. The E2 gene was significantly more likely to be disrupted in women who tested positive for HPV18 in their baseline sample than in those who tested positive for HPV16 [26% versus 58%; relative risk, 2.26; 95% confidence interval (CI), 1.38-3.71; chi(2), 9.23; 1 degree of freedom (df); P = 0.002]. Among women with an intact E2 gene in their baseline sample, the median time to first detection of E2 disruption was also shorter for those who tested positive for HPV18 than HPV16 (5.7 versus 10.9 months; hazards ratio, 1.93; 95% CI, 0.84-4.44; chi(2), 2.49; 1 df; P = 0.11). This tendency for HPV18 to integrate early, coupled with the substantial reduction in viral load in HPV18-positive samples in which E2 is disrupted, may explain why HPV18-associated disease is often reported to be characterized by minor cytologic changes, which underestimate the severity of the underlying histologic abnormality.

Ancillary testing of liquid-based cytology specimens for identification of patients at high risk of cervical cancer

Integration of human papillomavirus DNAs into the host genome is crucial to the development of cervical cancer. Overexpression of the P16 protein has been reported in cervical intraepithelial neoplasia (CIN) as well as cervical cancer. Such molecular biomarkers have been utilized for ancillary testing of liquid-based cytology specimens; however, their clinical application remains controversial. To detect CIN 2 or more advanced lesions, 153 liquid-based cytology (LBC) specimens were investigated to determine the physical status of the human papillomavirus (HPV) DNA by in situ hybridization (ISH) and to detect overexpression of the P16 protein by immunocytochemistry combined with HPV genotyping by polymerase chain reaction. The combination of ISH, P16 immunocytochemistry, and LBC showed high sensitivity (89.3%) as well as high specificity (92.6%). We confirmed the usefulness of P16 immunocytochemistry combined with ISH and HPV genotyping as ancillary molecular-biological tests of LBC specimens for identifying patients at high risk of cervical cancer.

Second hit in cervical carcinogenesis process: involvement of wnt/beta catenin pathway

The Human papillomavirus plays an important role in the initiation and progression of cervical cancer. However, it is a necessary but not sufficient cause to develop invasive carcinoma; hence, other factors are required in the pathogenesis of this malignancy. In this review we explore the hypothesis of the deregulation of wnt/beta-catenin signaling pathway as a "second hit" required to develop cervical cancer.

Pitfalls in the epidemiologic classification of human papillomavirus types associated with cervical cancer using polymerase chain reaction: driver and passenger

Cervical cancer is a common malignancy in women worldwide, and it has now been established that the human papillomavirus (HPV) is both necessary and causal for these lesions. HPV itself is both ubiquitous and markedly heterogeneous but can nevertheless be classified as either a high-risk type or a low-risk type based upon its frequency of detection in cervical cancer. Given that the association between HPV and cervical cancer is causal, the classification of this virus has been strengthened by large-scale epidemiologic studies and is widely accepted across many disciplines. It is evident, however, that cervical cancer is frequently associated with multiple HPV types. Therefore, it is crucial to distinguish causal types of HPV (drivers) from noncausal types (passengers) in cervical lesions. In this review, we highlight the current pitfalls of using polymerase chain reaction methods instead of Southern blot hybridization for detecting HPV and discuss the distinction between driver and passenger HPVs with regard to the viral type, the length of the viral genome, and the levels of viral DNA associated with cervical cancer. Finally, we newly propose three categories of HPV instead of two risk groups, based on similarities between viral genes.

Human papillomavirus DNA integration and messenger RNA transcription in cervical low- and high-risk squamous intraepithelial lesions in Austrian women

The human papillomavirus (HPV) plays an important role in the progression of cervical carcinoma. High-risk (HR) HPV types have been mainly identified in cytologic high-grade squamous intraepithelial lesions (HSILs) and histologic invasive carcinoma of the cervix. We examined cervical swabs of patients with abnormal Papanicolaou (Pap) smears, diagnosed as low-grade squamous intraepithelial lesions (LSILs) including atypical squamous cells of uncertain significance or HSILs. Low-risk (LR) HPV and HR-HPV types were identified by the Digene Hybrid Capture II test. Two-dimensional (2D) gel electrophoresis was used to specify the physical state of HPV DNA sequences. Expression of E6/E7 messenger RNA (mRNA) transcripts was analyzed by reverse transcriptase-polymerase chain reaction. Histopathologic results were correlated to the patients' physical status and HPV DNA mRNA transcripts. Pap smears with HPV infections of LR and HR types were correlated to the degree of squamous intraepithelial lesions (SILs). Comparing the physical states of HPV DNA sequences with the expression of HPV E6/E7 mRNA transcripts, all types were identified only as extrachromosomal in benign cervical smears, cervical intraepithelial neoplasia (CIN) I and II. HPV16 showed all physical states in CIN III/carcinoma in situ (CIS), whereas HPV18 only existed in mixed and integrated forms. HPV31/33/52b/58 appeared in all stages of lesions most commonly in extrachromosomal form; in integrated form, they were present only in CIN III/CIS. Although integration of some HR-HPV types is not always necessary for progression of SILs, the above-mentioned method is useful to analyze the physical state of HPV DNA sequences and predict the progression of SILs.

The natural history of cervical HPV infection: unresolved issues

The identification of high-risk human papillomavirus (HPV) types as a necessary cause of cervical cancer offers the prospect of effective primary prevention and the possibility of improving the efficiency of cervical screening programmes. However, for these opportunities to be realized, a more complete understanding of the natural history of HPV infection, and its relationship to the development of epithelial abnormalities of the cervix, is required. We discuss areas of uncertainty, and their possible effect on disease prevention strategies.

Detection of human papillomavirus type 16 integration in pre-neoplastic cervical lesions and confirmation by DIPS-PCR and sequencing

BACKGROUND

Persistent infections with high-risk types of human papillomavirus (HR-HPV) favour integration of viral DNA into the host cells and are associated with cervical carcinoma. HPV16 is the prevalent HR-type worldwide associated to cervical cancer. Integration of viral DNA promotes a selective cell growth advantage, resulting a risk factor for cancer development.

OBJECTIVES

To test physical status of HPV16 infection in pre-neoplastic cervical lesions using a quantitative real time-PCR (QRT-PCR) based method. To investigate reliability of this method in identification of HPV16 integrated sequences, by detection of integrated papillomavirus sequences (DIPS-PCR) assay and sequencing.

STUDY DESIGN

One hundred and seventy HR-HPV positive archival cervical specimens were tested for presence of HPV16 DNA. In HPV16 positive samples, viral load and physical status were evaluated.

RESULTS

HPV16 DNA was detected in 74/170 (43%) HR-HPV positive specimens. In 52/74 a QRT-PCR was performed, and 3 integrated, 13 mixed and 36 episomal forms were detected. Presence of integrated forms was confirmed by DIPS-PCR and sequencing.

CONCLUSIONS

Presence of HPV integrated forms was detected and confirmed in pre-neoplastic cervical lesions. The QRT-PCR method we used is sensitive and specific for identification of HPV integration in cervical samples, and may be suitable for large scale investigations with prognostic and clinical implications in management of cervical cancer.

CpG methylation of HPV 16 LCR at E2 binding site proximal to P97 is associated with cervical cancer in presence of intact E2

Human papillomavirus type 16 (HPV-16) E2 protein negatively regulates transcription of the E6 and E7 genes. This study was done to test the hypothesis that methylation of the HPV 16 long control region (LCR) is overrepresented among cervical cancer (CaCx) cases compared to cytologically normal controls harboring intact E2 gene. Methylation of the E2 binding site (E2BS-I), proximal to the P97 promoter, was assessed by HpaII/ MspI restriction digestion while McrBC digestion was used to assess LCR-E6 (7289-540) for 57 CaCx samples and 15 normal controls. E2BS-I methylation was found to be significantly higher (56.14%) in cases compared to (20%) controls [OR(age-adjusted) (95% CI): 4.53 (1.05-19.43) p=0.042]. The difference between cases (54.39%) and controls (40%) with respect to LCR-E6 methylation status [OR(age-adjusted) (95% CI): 1.77(0.5-6.3); p=0.38] was not significant. Sequencing of a randomly selected set of 13 methylated malignant samples revealed absence or rare presence, of methylation at CpGs 7579, 7535, 7683 and 7862 respectively. Methylation was found to be more at CpGs within E2 binding sites proximal to the P97 promoter. These results indicate the involvement of E2 binding site methylation in presence of intact E2, leading to loss of E2 repressor activity in CaCx.

p14ARF, a prognostic predictor in HPV-negative vulvar carcinoma

The present study addressed the impact of human papillomavirus (HPV), p14, and the product of the retinoblastoma gene (pRb) in vulvar carcinoma in relation to other clinicopathologic variables and prognosis. We immunohistochemically studied 217 primary tumors from patients with vulvar carcinoma for the expression of pRb and p14. By the use of in situ hybridization, the primary tumors and 7 lymph node metastases were studied for the presence of HPV-16, HPV-18, HPV-31, and HPV-33 DNA. HPV-infected cases significantly correlated with high expression of p14 (P < .01) and p16 (P < .01). In HPV- cases with high expression of p53, no p14 expression predicted the poorest disease-specific survival (P < .01). For the first time, we have shown that p14 expression indicates longer disease-specific survival in patients with vulvar carcinoma. In patients with HPV- tumors expressing high levels of p53, low p14 indicated the poorest 5-year disease-specific survival.

Identification of a proliferation gene cluster associated with HPV E6/E7 expression level and viral DNA load in invasive cervical carcinoma

Specific HPV DNA sequences are associated with more than 90% of invasive carcinomas of the uterine cervix. Viral E6 and E7 oncogenes are key mediators in cell transformation by disrupting TP53 and RB pathways. To investigate molecular mechanisms involved in the progression of invasive cervical carcinoma, we performed a gene expression study on cases selected according to viral and clinical parameters. Using Coupled Two-Way Clustering and Sorting Points Into Neighbourhoods methods, we identified a 'cervical cancer proliferation cluster' composed of 163 highly correlated transcripts. Most of these transcripts corresponded to E2F pathway genes controlling cell division or proliferation, whereas none was known as TP53 primary target. The average expression level of the genes of this cluster was higher in tumours with an early relapse than in tumours with a favourable course (P = 0.026). Moreover, we found that E6/E7 mRNA expression level was positively correlated with the expression level of the cluster genes and with viral DNA load. These findings suggest that HPV E6/E7 expression level plays a key role in the progression of invasive carcinoma of the uterine cervix via the deregulation of cellular genes controlling tumour cell proliferation. HPV expression level may thus provide a biological marker useful for prognosis assessment and specific therapy of the disease.

HPV16 E2 gene disruption and polymorphisms of E2 and LCR: some significant associations with cervical cancer in Indian women

OBJECTIVES

We evaluated the status of the HPV16 E2 gene (disrupted or intact), nucleotide sequence alterations within intact E2 genes and LCR of HPV16 isolates in a group of CaCx cases (invasive squamous cell carcinomas, n = 81) and population controls (normal cervical scrapes, n = 27) from Indian women.

METHODS

E2 disruption was detected by amplifying the entire E2 gene with single set of primers, while overlapping primers were used to determine if any particular region got selectively disrupted. Nucleotide variations in E2 and LCR were analyzed by PCR amplification followed by bi-directional sequencing. The associations between the viral factors and CaCx were analyzed using Fisher's Exact or Chi-squared test and interpreted as OR (95% CI) and P values.

RESULTS

E2 disruption was significantly higher among the cases [3.38 (1.07-10.72); P = 0.02], which was maximum in the region between nucleotides 3650 and 3872 (DNA-binding region). The European (E) variant was found to be the prevalent subgroup (87.76% among cases and 96.30% among the controls), and the remaining samples were Asian-American variants. Among the E subgroup, variation at position 7450 (T > C) within the E2-binding site-IV was found to be significantly higher among the E2 undisrupted cases (21/37; 56.76%), compared to controls (5/18; 27.78%) [3.41 (1.01-11.55); P = 0.03].

CONCLUSIONS

Besides HPV16 E2 disruption, LCR 7450T > C variation within undisrupted E2 of E subgroup appears to be a major factor contributing to the risk of CaCx development in Indian women. Furthermore, polymorphisms in the E2 gene of HPV16 may not be significant for disease risk.

Establishment and partial characterization of an ovine synovial membrane cell line obtained by transformation with Simian Virus 40 T antigen

The small ruminant lentiviruses, namely caprine arthritis encephalitis virus (CAEV) and Maedi Visna virus (MVV) are grown currently in secondary synovial membrane cells. Primary and secondary cell cultures are sometimes difficult to obtain and support a low number of passages and, therefore, permissive cell lines are needed. A transformed cell line was obtained by transfection of ovine synovial membrane secondary cell culture with a plasmid containing the SV40 large T antigen gene. The transformed cell culture described in this paper showed a higher growth rate and a more homogenous population of fibroblast-like cells when compared to the original ovine synovial membrane secondary cell cultures. Karyotype analysis has indicated the induction of many random chromosome changes, leading to a decrease in chromosome number. The SV40 DNA was detected in the nucleus and in the cytoplasm of transformed cells. The putative expression of large T antigen was presumed by the detection of the corresponding mRNA by PCR. Finally, the transformed ovine synovial membrane cells were shown to be permissive to small ruminant lentiviruses, and these are suggested as a cell line for in vitro isolation and propagation of these viruses.

Comparison between in situ hybridization and real-time PCR technique as a means of detecting the integrated form of human papillomavirus 16 in cervical neoplasia

Integration of the human papillomavirus (HPV) genome is thought to be one of the causes of cancer progression. However, there is controversy concerning the physical status of HPV 16 in premalignant cervical lesions, and there have been no reports on the concordance between detection of the integrated form of HPV16 by real-time PCR and by in situ hybridization. We investigated specimens of cervical intraepithelial neoplasia (CIN) and invasive carcinomas for the physical status of HPV 16 by real-time PCR and in situ hybridization. The presence of the integrated form was detected by both real-time PCR and in situ hybridization in zero of four cases of CIN1, three of six cases of CIN2, nine of 27 cases of CIN3, and two of six cases of invasive carcinomas. Integrated HPV 16 was present in some premalignant lesions but was not always present in carcinomas. The concordance rate between the two methods for the detection of the presence of the integrated form was 37 of 43 (86%) cases. Real-time PCR and in situ hybridization were found to be complementary and convenient techniques for determining the physical status of the HPV genome. We conclude that a combination of both methods is a more reliable means of assessing the physical status of the HPV genome in cervical neoplasia.

Cervical human papillomavirus screening by PCR: advantages of targeting the E6/E7 region

PCR is a promising method for detection of human papillomavirus (HPV), the high-risk forms of which are responsible for cervical cancer. PCR primers that target the L1 or E1 region can be unreliable and may miss more advanced disease, whereas those directed at the E6 or E7 regions, which encode oncogenic products, are preferable because 1) the LI/E1 regions, but never the E6/E7 regions, are lost during integration of viral DNA into host genomic DNA, a process that can represent an integral component of progression from infection to tumorigenesis; and 2) the E6/E7 nucleotide sequence exhibits less nucleotide variation. The choice of region used for PCR has implications for HPV screening strategies in the clinical diagnosis and management of cervical cancer.

E2 sequence variations of HPV 16 among patients with cervical neoplasia seen in the Indian subcontinent

OBJECTIVES

Specific nucleotide variations in the E2 DNA sequence were looked for in samples with an intact human papillomavirus (HPV) 16 episomal E2 DNA.

METHODS

Ninety-two women, 76 with invasive cervical carcinoma and 16 with cervical intraepithelial neoplasia (CIN) were recruited. HPV DNA typing was performed by polymerase chain reaction (PCR) based restriction fragment length polymorphism (RFLP). Intact episomal E2 DNA of HPV 16 was detected by PCR. Important nucleotide variations in samples with amplifiable E2 DNA were detected by RFLP. Nucleotide sequencing was performed on representative samples to confirm RFLP findings.

RESULTS

A total of 89 (96.7%) women were positive for HPV DNA. Of these, 56 (63%) were positive for HPV 16, and of these, 38 (68%) were positive for intact episomal HPV 16 E2 DNA while 18 (32%) were negative. Samples with intact episomal HPV 16 E2 DNA sequences were grouped into four different digestion profiles I to IV based on RFLP patterns. Digestion patterns revealed absence of any sequence variations in samples with digestion profile I and presence of a 2983 A-G variation in those with profile II. Samples with digestion profiles III and IV revealed three variations in the hinge region (3516 C-A, 3538 A-C, 3566 T-G) and two in the DNA binding domain (3684 C-A, 3694 T-A) of the E2 sequence. Sequencing performed on representative samples confirmed RFLP findings.

CONCLUSIONS

PCR-RFLP helped in the identification of important HPV 16 E2 sequence variations, circumventing the need for sequencing. The presence of the nucleotide variations in positions that could alter the biological and immunological functions of the E2 protein combined with its increased occurrence in this study bring out the importance of these variations.

Human papillomavirus genomes in squamous cell carcinomas of the uterine cervix

The association between invasive cervical carcinoma and human papillomavirus (HPV) has now been established beyond doubt, but this is not necessarily a direct-and-effect association. To assess the causality of HPV, we analyzed HPV genomes in squamous cell carcinomas (SCCs) [corrected] of the uterine cervix by both blot hybridization and PCR. Genital HPV sequences were found in 231 (79%) of 294 SCCs by blot hybridization with more than five copies of entire HPV genomes identified in some cases including HPV 16 (92 cases), HPV 58 (32 cases), and HPV 52 (24 cases). By PCR-direct sequence analysis in 250 of 294 SCCs, genital HPV sequences were found in 240 samples (96%). The partial L1 sequences of HPV 16 were identified in 123 cases, and those of HPVs 18 and 31 were found in 24 and 20 cases, respectively. In addition, multiple HPV types were identified in 29 (12%) of 250 SCCs, and the HPV copy number, detected by PCR only, was less than 0.05. Marked discrepancies were therefore evident between the two analytical techniques. In this report, we discuss the causality of HPV for SCC with regard to the length of the viral genome, the amount of viral DNA, and multiple HPVs in single SCCs.