Expression of human papillomavirus E7 mRNA in human oral and cervical neoplasia and cell lines

Cancer Precursor Syndromes and Their Detection in the Head and Neck

This article explores the multifaceted landscape of oral cancer precursor syndromes. Hereditary disorders like dyskeratosis congenita and Fanconi anemia increase the risk of malignancy. Oral potentially malignant disorders, notably leukoplakia, are discussed as precursors influenced by genetic and immunologic facets. Molecular insights delve into genetic mutations, allelic imbalances, and immune modulation as key players in precancerous progression, suggesting potential therapeutic targets. The article navigates the controversial terrain of management strategies of leukoplakia, encompassing surgical resection, chemoprevention, and immune modulation, while emphasizing the ongoing challenges in developing effective, evidence-based preventive approaches.

Establishment and characterization of a human papillomavirus type 16-positive tonsillar carcinoma xenograft in BALB/c nude mice

BACKGROUND

Among head and neck cancers, human papillomavirus type 16 (HPV16) is associated with tonsillar carcinomas. Despite this, no HPV16-positive tonsillar cancer cell line has been established in nude mice.

METHODS

Fresh tonsillar carcinoma biopsies were obtained from 23 patients and implanted subcutaneously into nude mice (BALB/c, nu/nu).

RESULTS

After 7 months, one xenograft was established. The primary tumor harbored 2.7 copies (95% confidence interval = 2.4-2.9) of HPV16/cell and displayed 99.9% (7904/7906) nucleotide identity to HPV16 (EU118173.1). The xenograft showed increased methylation in two E2-binding sites of the HPV16 genome. Both episomal and integrated HPV16 were detected in the original tumor and in 14 xenografts from the second passage. From this passage, a viral load of 6.4 copies/cell (range = 4.6-9.6) and 3.7 (range = 1.0-5.5) E7-mRNA transcripts/HPV16-genome were detected.

CONCLUSION

This xenograft represents the first established HPV16-positive tonsillar tumor in nude mice and could provide an experimental system of HPV16-positive tonsillar cancers.

Evidence for a causal association for HPV in head and neck cancers

Current data have now attributed a viral etiology and causality of Human papillomavirus (HPV). Epidemiological analysis of the last decade demonstrates a rapid increase of HPV-associated HNSCC. Genomic detection of HPV DNA in the nuclei of certain oro-pharyngeal cancer cells gives strong evidence of a viral etiology in HNSCC. Non-smokers, non-drinkers, and a sexual debut at a younger age and other sexual risk factors have an increased risk of HPV-positive oropharyngeal cancer. Sexual transmission is considered to play a causal role. In contrast to HPV-negative HNSCC most studies reveal a favorable prognosis for HPV-positive tumors. There is evidence of alterations in the p53 pathway through expression of E6 oncogene with subsequent induction of tumor cell proliferation. Synergies between viral oncogenes and other carcinogens are hypothesized. HPV alone appears to be insufficient as the sole cause of HNSCC; this may explain the long latency period between HPV infection and cancer development. There is now sufficient evidence for a causal role for HPV in HNSCC. As in cervical cancer, HPV requires oncogenes and co-factors for tumor development. Thus, inhibition or loss of such co-factors may lead to tumor regression. The vast amounts of epidemiological, molecular pathological and in vitro experimental data are consistent with the hypothesis that HPV does indeed have a causal role. We await final validation from animal experimentation in which regression of HPV-positive tumors will follow from loss or inhibition of E6 and E7.

Transactivation and expression patterns of Jun and Fos/AP-1 super-family proteins in human oral cancer

Transcription factor activator protein-1 (AP-1) super-family is known to modulate expression of array of genes during development of many cancers and considered as an important target for modern therapeutics. But the role of AP-1 during development of human oral cancers is still poorly understood. Because oral cancer is one of the most common cancers in India and south-east Asia, we studied the activation and expression pattern of AP-1 family of proteins and mRNA in different stages of oral carcinogenesis. Gel-shift assay, western blotting, immunohistochemistry and northern blotting have been used to assess the binding activity and expression pattern of AP-1 family (c-Jun, JunB, JunD, c-Fos, FosB, Fra-1 and Fra-2) proteins and mRNA transcripts in a total of 100 fresh oral tissue specimens comprising precancer (n = 40), cancer (n = 50) and healthy control (n = 10). Constitutive activation of AP-1 with concomitant upregulated expression of majority of AP-1 family of proteins and mRNA was observed in cancer cases. Interestingly, almost all precancerous cases showed JunD homodimers, whereas c-Fos/JunD was the most prevalent complex found in cancer tissues. The overexpression of EGFR mRNA, p50:p50/NF-kappaB homodimer formation, together with overexpression of pERK and c-Fos proteins in this study suggests an interesting cross talk between AP-1 and NF-kappaB pathways in oral cancers. Thus, this study demonstrates differential expression and activation of AP-1 super-family proteins in relation to severity of lesion and their crucial role in human oral carcinogenesis.

Human papillomavirus typing and viral gene expression analysis for the triage of women with abnormal results from papanicolaou test smears to colposcopy

CONTEXT

A cascade of molecular tests for human papillomavirus (HPV), as a follow-up to Papanicolaou test screening, could eliminate unnecessary colposcopy. Tests based on detection of HPV E6 messenger RNA (mRNA) are already being used as screening tools, but there is a good biological rationale for expecting that an increase in the relative amounts of HPV E6 mRNA in cervical samples may better predict cancerous transformation.

OBJECTIVE

To compare some of the available diagnostic methods and our novel method of relative quantification (RQ) of HPV gene expression for the effective triage of women with abnormal results from Papanicolaou tests to colposcopy.

DESIGN

Sensitivities, specificities, and likelihood ratios were calculated for repeat Papanicolaou test smears, HPV DNA polymerase chain reactions, HPV genotyping, HPV-16 E6 mRNA detection, and the RQ of HPV-16 E6 mRNA calibrated to cellular RNA and DNA levels and standardized to viral load.

RESULTS

Human papillomavirus genotype in combination with a repeat Papanicolaou test can be used to categorize most women (96%) with cervical intraepithelial neoplasia of grade 2 or higher for colposcopy while eliminating 44% of women with cervical intraepithelial neoplasia 1 or less. The presence of HPV-16 E6 mRNA (P < .001) and RQ of HPV-16 E6 mRNA (P < .001) displayed significant median differences among the various grades of cervical intraepithelial neoplasia. Further testing of women who are positive for HPV-16 demonstrated that the RQ of E6 mRNA has diagnostic potential when combined with Papanicolaou testing in populations with higher disease prevalence.

CONCLUSIONS

The RQ of HPV E6 mRNA and HPV genotype could be useful in a cascade of diagnostic testing designed to refer women with findings of cervical abnormalities for colposcopy or treatment while reducing triage numbers.

Viral interaction: a possible contributing factor in head and neck cancer progression

CONCLUSION

Human herpesvirus-8 could potentiate the effects of human papillomavirus (HPV)-16 on cell cycle dysregulation by up-regulating the transcription of HPV-16 E7, which can lead to malignant transformation of normal epithelial cells.

OBJECTIVES

High-risk HPV-16 is known for its association with development of head and neck carcinoma, leading to considerable morbidity and mortality worldwide. HPV-16 produces two early proteins, E6 and E7, that can disrupt the cell cycle and transform cells. Other viruses may potentiate dysregulation of the cell cycle by HPV-16. Herpes viruses are known to produce replication transcription activators, which may contribute to the malignant transformation of normal cells. This study aimed to determine if the ORF50/Rta protein of HHV-8 binds to genomic regions within HPV-16 and alters the transcription and/or translation of E6 and E7 in HPV-infected cells.

MATERIALS AND METHODS

Protein shift assays determined the binding potential of ORF50 to various HPV-16 genomic regions. A real-time polymerase chain reaction (PCR) assay quantified the effect of ORF50 on the transcription of E6 and E7 within these cells. Finally, immunofluorescent confocal microscopy was used to quantify E6 and E7 protein levels within transfected cells and study their localization patterns.

RESULTS

The results reveal potential ORF50/Rta binding sites within HPV-16 and a significant up-regulation of E7 transcription in ORF50 transfected cells.

Human papillomavirus-related diseases: oropharynx cancers and potential implications for adolescent HPV vaccination

Molecular and epidemiological data now support an etiologic role for oncogenic human papillomavirus (HPV) in oral cancers in women and men. Recent studies have demonstrated an increase in the incidence of HPV-associated oral cancers in the United States. Moreover, the incidence rates for these cancers are higher in men than women. Oral HPV infections acquired through oral sex appear to be the principal risk factor for HPV-associated oral cancers. Despite reports in the popular press that the prevalence of oral sexual behaviors is increasing in the adolescent population, trends in these behaviors over time are largely unavailable. However, data indicate that oral-genital contact is frequently practiced among adolescents; adolescents do not typically consider this a risky behavior. The majority of oral cancers (approximately 90%) caused by HPV are identified as HPV 16 positive. Therefore, HPV-associated oral cancers could be prevented by a prophylactic vaccine if the vaccine were demonstrated to be capable of preventing oral HPV 16 infection. These findings have created new potential opportunities for the primary prevention of oral cancers.

Detection of human papillomavirus and relevant tumor suppressors and oncoproteins in laryngeal tumors

PURPOSE

The mechanism of larynx oncogenesis is complex and controlled by various factors, most of them involved in cell proliferation and apoptosis. In this study, we evaluated the levels of two suppressor proteins (pRb and p53) and two oncogenic proteins (c-Myc and Bcl-2), as well as the apoptotic levels and the presence of human papillomavirus (HPV) in both tumor types.

EXPERIMENTAL DESIGN

Low- or high-risk HPV viral DNA was determined by PCR and in situ PCR; the level of cellular proteins was examined by immunohistochemistry; the presence of apoptotic cells was evaluated by in situ cell death detection.

RESULTS

Most laryngeal papillomatosis samples contained low-risk HPV determined by both techniques. However, 25% of laryngeal carcinoma samples were positive for HPV employing PCR or in situ PCR. In papillomatosis, pRb and p53 levels were higher than in normal larynxes, whereas laryngeal cancer presented the lowest levels. c-Myc oncogene expression was very low in normal and cancer tissues but highly increased in papillomatosis. Bcl-2 expression was low and showed no significant difference between laryngeal papillomatosis and normal larynxes. By contrast, Bcl-2 was clearly up-regulated in cancer. Normal larynx samples and those from laryngeal papillomatosis exhibited similar relatively high numbers of apoptotic cells, whereas in malignant tumors, these cells were scarce.

CONCLUSION

Our results suggest that HPV is an important risk factor in papillomatosis and in some malignant larynx tumors with a strong participation of cellular genes, specifically involved in proliferation and apoptosis. In benign papillomatosis lesions but not in larynx cancer, high p53 activity might preserve the apoptosis process. In larynx cancer, low p53 levels and high bcl-2 expression may be playing an important role to block apoptosis.

Absolute quantitative real-time polymerase chain reaction for the measurement of human papillomavirus E7 mRNA in cervical cytobrush specimens

Background

Few reports of the utilization of an accurate, cost-effective means for measuring HPV oncogene transcripts have been published. Several papers have reported the use of relative quantitation or more expensive Taqman methods. Here, we report a method of absolute quantitative real-time PCR utilizing SYBR-green fluorescence for the measurement of HPV E7 expression in cervical cytobrush specimens.

Results

The construction of a standard curve based on the serial dilution of an E7-containing plasmid was the key for being able to accurately compare measurements between cervical samples. The assay was highly reproducible with an overall coefficient of variation of 10.4%.

Conclusion

The use of highly reproducible and accurate SYBR-based real-time polymerase chain reaction (PCR) assays instead of performing Taqman-type assays allows low-cost, high-throughput analysis of viral mRNA expression. The development of such assays will help in refining the current screening programs for HPV-related carcinomas.

Human papillomavirus-related cellular changes measured by cytometric analysis of DNA ploidy and chromatin texture

BACKGROUND

Image cytometry has provided two highly sensitive markers for the identification of the malignant potential of squamous lesions. Aneuploidy and chromatin texture have been investigated as quantitative measures of nuclear damage in premalignant lesions and carcinoma. Real-time PCR methods have evolved to yield highly specific measurements of mRNA expression in very sparse cellular samples.

METHODS

Human papillomavirus (HPV) 16 and 18 E7 mRNA expression was measured using quantitative RT-PCR. DNA index and chromatin measures were taken from image cytology samples. The chromatin features, through discriminant analysis, were aggregated into a score, and both measurements were related to mRNA expression.

RESULTS

mRNA level and DNA index show an increasing trend over increasing histological grades. However, DNA index and chromatin score were not correlated to mRNA levels in these samples. Chromatin score differed by mRNA type found with HPV 18 infected samples having a higher score than those with HPV 16. Samples infected with HPV 16 and HPV 18 had even higher chromatin scores.

CONCLUSIONS

DNA index and chromatin score were not directly correlated with mRNA levels. However both mRNA and DNA index were related to histological grade, and chromatin score was associated with HPV type. Therefore, DNA index and mRNA levels could be independent predictors of cervical dysplasia, and chromatin score could be related to the viral integration process in cells infected with HPV 18 or dual infections.

Clinical implications of human papillomavirus in head and neck cancers

Human papillomavirus (HPV) is now recognized to play a role in the pathogenesis of a subset of head and neck squamous cell carcinomas (HNSCCs), particularly those that arise from the lingual and palatine tonsils within the oropharynx. High-risk HPV16 is identified in the overwhelming majority of HPV-positive tumors, which have molecular-genetic alterations indicative of viral oncogene function. Measures of HPV exposure, including sexual behaviors, seropositivity to HPV16, and oral, high-risk HPV infection, are associated with increased risk for oropharyngeal cancer. HPV infection may be altering the demographics of HNSCC patients, as these patients tend to be younger, nonsmokers, and nondrinkers. There is sufficient evidence to conclude that a diagnosis of HPV-positive HNSCC has significant prognostic implications; these patients have at least half the risk of death from HNSCC when compared with the HPV-negative patient. The HPV etiology of these tumors may have future clinical implications for the diagnosis, therapy, screening, and prevention of HNSCC.

Overexpression of p16INK4 is a reliable marker of human papillomavirus–induced oral high-grade squamous dysplasia

OBJECTIVE

Human papillomavirus (HPV) infection has been implicated in the development of high-grade squamous dysplasia and carcinoma of the oral cavity in the absence of other known risk factors such as smoking. HPV-induced oral dysplasia or carcinoma may be a unique tumor entity in terms of biologic behavior and treatment decisions. In detecting such cases, most reported studies have used techniques that are less sensitive than DNA amplification. Recent reports have suggested that overexpression of the p16INK4 protein is a surrogate marker of HPV-induced high-grade dysplasia or carcinoma. However, the correlation between expression of p16INK4 and the presence of HPV DNA as determined by polymerase chain reaction (PCR) amplification has not been previously reported. The purpose of this research was to determine if immunohistochemistry for p16 would serve as a marker of HPV-associated high-grade oral squamous dysplasia.

STUDY DESIGN

Archival formalin-fixed, paraffin-embedded tissue sections from 41 cases of high-grade oral squamous dysplasia were randomly selected. Expression of p16INK4 protein was assessed by immunohistochemical analysis (16P04 Neomarkers, Fremont, CA). Strong and diffuse nuclear staining restricted to the dysplastic region in the epithelium was scored as positive for protein expression, whereas focal or weak nuclear or cytoplasmic staining was scored as negative. The presence of HPV was determined by microdissection, DNA extraction, and PCR DNA amplification using elongated primers that align with corresponding sequences of the L1 region of 23 mucosotropic HPV genotypes. The HPV type was determined by direct sequencing of the PCR product. Normal squamous epithelium was used as an internal negative control, and cases of severe cervical high-grade squamous dysplasia were used as a positive control for immunohistochemical staining and PCR.

RESULTS

The results of immunohistochemical analysis for overexpression of p16INK4 were positive in 6 of the 41 tissue sections. The results of PCR DNA amplification were also positive for these 6 sections. HPV-16 was identified in 5 of the positive cases; in the other case, the viral strain could not be determined.

CONCLUSIONS

Immunohistochemical detection of p16INK4 is a technically simple and potentially reliable assay for diagnosing cases of HPV-induced oral high-grade squamous dysplasia. Detecting such lesions may influence future therapeutic decisions.

DNA damaging drugs-induced down-regulation of Bcl-2 is essential for induction of apoptosis in high-risk HPV-positive HEp-2 and KB cells

DNA damaging chemotherapeutic agents like carboplatin (Carb) and 5-fluorouracil (5-FU), whose effects are mediated through diverse intracellular targets, induce apoptosis in various cancer cells including human papillomavirus (HPV) positive HEp-2 and KB cells. The present work reports the involvement of Bcl-2 in response to the exposure of HEp-2 and KB cells to Carb or 5-FU. We demonstrate that both these drugs are potent inducers of apoptosis. Apoptosis was preceded by decrease in Bcl-2 protein level accompanied by caspase-9 activation and poly(ADP-ribose) polymerase (PARP) cleavage without altering Bax expression. Further analysis revealed down-regulation of Bcl-2 mRNA as well as protein in drugs treated cells. Ectopic expression of Bcl-2 protected cells against drugs mediated DNA damage-induced apoptosis. Overall, data indicates that genotoxic stress leads to down-regulation of Bcl-2 in HEp-2 and KB cells, which plays a decisive role in the outcome of stress in these cells.

Correlation of human papillomavirus type 16 and human papillomavirus type 18 e7 messenger RNA levels with degree of cervical dysplasia

Infection with certain types of human papillomavirus (HPV) is a necessary event in the development of cervical carcinoma; however, not all women who become infected with HPV will progress to cancer. Much is known about the molecular influence of HPV E6 and E7 proteins on the malignant transformation. Little is known about the additional factors needed to drive the process. Quantitative real-time PCR was used to quantitate mRNA expression of the E7 gene in women exhibiting normal epithelium, low-grade squamous intraepithelial lesions (LSIL), and high-grade squamous intraepithelial lesions (HSIL). Prevalence of mRNA transcripts was lower among normal women (27%) than for women with LSIL (40%) and HSIL (37%). Mean levels ranged from 2.0 (ln scale per 20 ng cDNA) among normal women to 4.2 among those with HSIL, with a significant trend (P=0.008). This trend was only significant for HPV 18 transcripts if separately analyzed by HPV type. The transcriptional activity of HPV 18 is higher than that of HPV 16 and increases with increasing level of dysplasia. This is in concert with the findings of other studies, and reinforces the notion that HPV 18 is a more aggressive viral type. Real-time PCR of viral transcripts could provide a more efficient method to analyze the oncogenic potential within cells from a cervical swab, thus providing a way to better screen women who may progress to higher grade lesions or invasive carcinoma from those who will spontaneously regress.

Human papillomavirus and disease mechanisms: relevance to oral and cervical cancers*

Oral squamous cell carcinoma (OSCC) is the sixth most common malignancy and is a major cause of cancer morbidity and mortality worldwide. Carcinoma of the uterine cervix is the most common female malignancy in the world. While cervical cancer is a worldwide disease, oral cancer has the highest incidence in developing countries, especially among tobacco and alcohol users and betel quid chewers. A strong association of cervical and oral cancer with high-risk human papillomavirus (HPV) 16 and 18 infections underlines the importance of the virus in the pathogenesis of these squamous cell carcinomas. Functionally high-risk HPV infection contributes to carcinogenesis and tumor progression predominantly through the actions of two viral oncogenes, E6 and E7. The E6 and E7 genes have been studied in different patient populations and a number of variants have been described. More than 40 variants have been classified and may be related to differences in progression of squamous intraepithelial lesions. The transcription factor, NFkappaB and its activation pathways are frequently targeted by viruses and aberrant constitutive activation of NFkappaB is frequently found in human tumors of diverse tissue origin. Diet-gene interactions are also likely to contribute considerably to the observed inter-individual variations in HPV associated cancer risk, in response to exposures to the nutritional factors that have the potential to promote or protect against cancer.

Human papillomavirus (HPV) in head and neck cancer

The term "head and neck cancer" has been widely adopted in the recent literature, to include the lesions at several anatomic sites: the lip, oral cavity, nose and para-nasal sinuses, naso-pharynx, oro-pharynx, hypo-pharynx, and larynx. In this communication, the data on human papillomavirus (HPV) involvement in oral, oro-pharyngeal, sino-nasal, and laryngeal carcinomas are reviewed. Our group was the first to present evidence on the involvement of HPV infections in both laryngeal and oral carcinogenesis, prompted by the discovery of morphological similarities between oral and cervical squamous cell lesions. The latest meta-analyses of the epidemiological studies as well as the multi-centre case-control studies have confirmed HPV as an independent risk factor for oral cancer, with a range of odds ratios (OR) between 3.7 and 5.4. Until 2002, 4768 oral carcinomas have been analysed for HPV DNA, and 22% were reported to contain HPV by any of the detection techniques. Of all non-genital cancers, tonsillar carcinomas appear to have the highest prevalence of HPV. By the end of 2002, 422 cases of tonsillar carcinoma have been analyzed for the presence of HPV DNA, with the overall detection rate of 51%. HPV 16 is the most prevalent HPV type found in 84% of HPV DNA-positive tumours. HPV seems to be mainly episomal in tonsillar carcinomas, but the significance of this observation is still obscure. Interestingly, patients with HPV 16-positive tumours seem to have a better overall- and disease-specific survival, as compared with the HPV-negative group. To date, 1041 sino-nasal papillomas have been analysed for HPV and 347 (33%) cases have been positive, whereas of the 322 sino-nasal carcinomas analysed so far, 70 (22%) have been positive for any HPV type. Laryngeal squamous cell papilloma and recurrent respiratory papillomatosis (RRP) are well-established HPV-induced tumours, whereas the role of HPV in laryngeal carcinomatosis remains controversial. The molecular mechanisms of HPV-associated carcinogenesis of the head and neck require further study.

Antiviral activity of Cidofovir on a naturally human papillomavirus-16 infected squamous cell carcinoma of the head and neck (SCCHN) cell line improves radiation sensitivity

High risk HPV types 16 and 18 are associated with cervical cancer and squamous cell carcinoma of the head and neck (SCCHN). Cidofovir is an antiviral drug used to treat HPV-induced laryngeal papillomatosis and other viral infections, with initial reports suggesting activity in cervical carcinoma cells. We investigated the effects of Cidofovir on a naturally HPV-16-transformed SCCHN cell line (UPCI:SCC090), in comparison with a cervical carcinoma cell line (CasKi) of similar viral characteristics, to evaluate its therapeutic potential. HPV-16 gene transcription was only marginally reduced, and the antiviral and p53 restorative effects were modest in SCC90 cells. However, combination with irradiation enhanced the effects of Cidofovir treatment on these cells. Several days of treatment were required for this effect, which may limit its clinical applicability. Future therapies for HPV-associated tumors may include intralesional antiviral therapy in combination with radiation therapy, but optimization for clinical utility is needed.

Human papillomavirus-16 associated squamous cell carcinoma of the head and neck (SCCHN): A natural disease model provides insights into viral carcinogenesis

Uncertainty regarding the causality of human papillomaviruses (HPVs) in squamous cell carcinoma of the head and neck (SCCHN) necessitates better in vitro models. We carried out molecular analyses of a novel, naturally HPV-16-transformed SCCHN cell line (UPCI:SCC090) and show high copy number of HPV-16 DNA, present in a head to tail, tandemly repeated integrated state. Sequence analysis of the HPV-16 long control region (LCR) in UPCI:SCC090 revealed a deletion of 163 bp, removing a portion of the enhancer sequence, including the binding sites for the transcription factors YY1 and NF1. The E6 and E7 oncogenes of HPV-16 are expressed at high levels in this cell lines, as determined by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). UPCI:SCC090 contains wild-type tumour suppressor TP53 gene, and undetectable p53 protein, except after treatment with cisplatin, specific proteasome inhibitors or by E6 RNA interference, suggesting E6-dependent degradation of p53 in this cell line. The results of our studies are consistent with a causative role of HPV-16 in the pathogenesis of SCCHN.

An association between human papillomavirus 16/18 deoxyribonucleic acid in peripheral blood with p16 protein expression in neoplastic cervical lesions

BACKGROUND

Human papillomavirus (HPV) infection plays a crucial role in cervical carcinogenesis. Apart from the detection of p16 protein in cervical tissues, the feasibility of the presence of HPV DNA in peripheral blood being an auxiliary marker of cervical lesions was examined.

METHODS

Peripheral blood samples and cervical tissues, from 36 cervical tissues from high-grade squamous intraepithelial lesions (HSIL) and 31 early invasive cervical cancers (EICC), were analyzed for HPV 16/18 DNA and HPV 16/18 E7 mRNA expression, as well as the in situ expressions of p16 and pRb to investigate the in-between associations.

RESULTS

The prevalence of HPV 16/18 DNA in patients with EICC was relatively higher than those of HSIL, in both of cervical tissues and peripheral blood. The presence of HPV 16/18 DNA in peripheral blood was positively correlated with that in cervical tissue, as well as with p16 overexpression in cervical tissues together with a significant correlation between E7 mRNA and pRb and p16 protein expressions.

DISCUSSION

A positive correlation between the presence of HPV 16 or 18 DNA in peripheral blood and p16 overexpression in tissues of patients with cervical lesions was confirmed. Together with p16 immunostaining in cervical tissues, the detection of high-risk HPV 16 or 18 DNA in peripheral blood may act as an auxiliary biomarker for HPV-associated neoplastic cervical lesions.

Human growth hormone presented by K14hGH‐transgenic skin grafts induces a strong immune response but no graft rejection

Although immune responses leading to rejection of transplantable tumours have been well studied, requirements for epithelial tumour rejection are unclear. Here, we use human growth hormone (hGH) expressed in epithelial cells (skin keratinocytes) as a model neo-self antigen to investigate the consequences of antigen presentation from epithelial cells. Mice transgenic for hGH driven from the keratin 14 promoter express hGH in skin keratinocytes. This hGH-transgenic skin is not rejected by syngeneic non-transgenic recipients, although an antibody response to hGH develops in grafted animals. Systemic immunization of graft recipients with hGH peptides, or local administration of stimulatory anti-CD40 antibody, induces temporary macroscopic graft inflammation, and an obvious dermal infiltrate of inflammatory cells, but not graft rejection. These results suggest that a neo-self antigen expressed in somatic cells in skin can induce an immune response that can be enhanced further by induction of specific immunity systemically or non-specific immunity locally. However, immune responses do not always lead to rejection, despite induction of local inflammatory changes. Therefore, in vitro immune responses and in vivo delayed type hypersensitivity are not surrogate markers for immune responses effective against epithelial cells expressing neoantigens.

Human papillomavirus-associated head and neck cancer is a distinct epidemiologic, clinical, and molecular entity

There is currently sufficient evidence to conclude that human papillomavirus (HPV) plays a role in the pathogenesis of a distinct subset of head and neck squamous cell cancers (HNSCC), particularly tonsillar cancers. There is a strong and consistent association between high-risk HPV types, specifically HPV16, a known human carcinogen, and these distinctive oropharyngeal cancers with molecular characteristics indicative of viral oncogene function. Risk for HPV-HNSCC is increased by certain sexual behaviors after consideration of alcohol and tobacco exposure, consistent with an extensive literature that has established HPV infection as a sexually transmitted disease. Furthermore, exposure to HPV16 has been associated with increased risk for subsequent development of oropharyngeal cancer. Prophylactic and therapeutic vaccines targeted against the viral capsid components and oncoproteins will provide the ultimate evidence for a role for HPV in HNSCC, if demonstrated to be effective in the prevention or therapy of this disease. It is time for clinician scientists to translate knowledge of this newly recognized disease entity into potential applications for the prevention, detection, and treatment of HPV-HNSCC.

HPV DNA and survivin expression in epithelial oral carcinogenesis: a relationship?

HPV has been thought to be involved in the development of several oral diseases, such as premalignant mucosal lesions and oral carcinoma. Survivin is a recently characterized IAP protein, which is abundantly expressed in most solid and haematological malignancies, but undetectable in normal adult tissues. Aim of this study was to investigate survivin expression and HPV presence in oral premalignant lesions and oral carcinoma. 47 samples of oral tissue including 11 squamous cell carcinomas (OSCC), 16 oral leukoplakias (OL) and 20 normal oral mucosa specimens, after investigation of HPV presence by nested PCR (consensus MY/GP primers) and viral genotype identification by direct sequencing were investigated by immunohistochemistry to detect survivin expression. Survivin expression was evident in 4/7 (57.1%) HPV+ and 4/4 (100%) HPV- OSCC, 6/7 (85.7%) HPV+ and 5/9 (55.5%) HPV- OL and in 0/20 (0%) control samples. Data showed high levels of survivin expression in HPV-positive SCCs, even if mean values were lower than HPV-negative ones, which in particular showed survivin expression in 100% of cases. Conversely, survivin expression was greater in HPV+ precancerous lesions than in HPV- ones. Our findings suggest that survivin may be involved in HPV- mediated deregulation during maturation of squamous epithelium through modulation of the apoptotic processes and, conversely, HPV may have a direct or indirect effect on the regulation of the survivin expression level. In particular, the results of this study suggest distinguishing between cancerous and precancerous oral lesions with respect to survivin expression when HPV infection is present. The most unfavourable behaviour is likely to be for the HPV- OSCC.

Cyclin D1 is essential for neoplastic transformation induced by both E6/E7 and E6/E7/ErbB-2 cooperation in normal cells

More than 25% of head and neck squamous cell carcinomas (HNSCC) and 99% of cervical cancers (CxCa) are positive for high-risk human papillomaviruses (HPVs). Furthermore, the type I tyrosine kinase receptor ErbB-2 is overexpressed in at least 30% of HNSCC and CxCa. Recently, we demonstrated that E6/E7 of HPV type 16 cooperate with ErbB-2 to induce cell transformation of human normal oral epithelial (NOE) cells. This is accompanied by overexpression of cyclin D1 in NOE cells. To determine the role of cyclin D1 in E6/E7/ErbB-2 cooperation, we examined the independent effects of E6/E7 and ErbB-2, and the combined effect of E6/E7 and ErbB-2 in mouse normal embryonic fibroblast (NEF), wild type (wt), and knockout cyclin D1 (D1(-/-)) cells. We report that NEF-wt cells transduced with E6/E7 alone and E6/E7/ErbB-2 together form small and large tumors in nude mice, respectively, as well as different sized colonies in soft agar; whereas ErbB-2 alone elicits neither tumor formation in vivo nor colony formation in soft agar. More importantly, E6/E7, ErbB-2 and E6/E7/ErbB-2 together all fail to induce neoplastic transformation of cyclin D1(-/-) cells in vivo and in vitro. Furthermore, using antisense cyclin D1 we completely inhibited tumor and colony formation of NEF-wt-E6/E7 and wt-E6/E7-ErbB-2 as well as human NOE-E6/E7-ErbB-2-transformed cells. These analyses reveal that cyclin D1 is the downstream target of the neoplastic transformation induced by E6/E7 or E6/E7/ErbB-2 cooperation in normal cells. Our data suggest that anti-cyclin D1 therapy may be highly specific in the treatment of all human cancers expressing high-risk HPVs or HPVs/ErbB-2.

E6/E7 proteins of HPV type 16 and ErbB-2 cooperate to induce neoplastic transformation of primary normal oral epithelial cells

Head and neck squamous cell carcinomas (HNSCC) are characterized by a marked propensity for local invasion and spread to cervical lymph nodes, with distant metastases developing in 30-40% of cases. HPV-16 is an important risk factor for HNSCC. How HPV enhances susceptibility to HNSCC is not fully understood, but seems to involve cofactors. In this study, we examined the effect of the cooperation between HPV-16 and the tyrosine kinase receptor ErbB-2 on E-cadherin/catenin complex patterns and neoplastic transformation of human normal oral epithelial (NOE) cells. We report that overexpression of ErbB-2 or E6/E7 alone does not affect E-cadherin/catenin complex patterns nor does it induce cell transformation of NOE cells. In contrast, coexpression of E6/E7 and ErbB-2 downregulates E-cadherin and catenin expression. This is accompanied by cytoplasmic localization of E-cadherin, as well as nuclear translocation of alpha, beta, and gamma-catenins. Furthermore, we demonstrate that E6/E7 cooperate with overexpressed ErbB-2 to induce tumor formation in nude mice and to upregulate cyclin D1 and c-myc expression. Our data suggest that E6/E7 cooperate with ErbB-2 in head and neck carcinogenesis, at least in part, via the conversion of beta-catenin from a cell adhesion to a nuclear function, that is, to act as a potential transcriptional regulator. This conversion leads to the upregulation of cyclin D1, c-myc and other oncoproteins necessary for alteration of the E-cadherin/catenin complex and cell transformation of NOE cells.

An AP-1 binding site mutation in HPV-16 LCR enhances E6/E7 promoter activity in human oral epithelial cells

Expression of the human papillomavirus (HPV) E6 and E7 oncoproteins is responsible for the transforming ability of the virus. The HPV long control region (LCR) and E6/E7 promoter regulate transcription of the E6 and E7 viral oncogenes. However, factors involved in the stimulation of E6/E7 promoter activity in carcinogenesis are unclear. We previously identified a point mutation in an HPV-16 immortalized human oral keratinocyte cell line subsequently exposed to a tobacco-specific carcinogen. This mutation was located in the LCR at nucleotide 7633 and contains binding sites for the transcription activator, AP-1, overlapping with putative binding regions for the transcription factor, C/EBP, which represses the E6/E7 promoter. In this study, this mutation was analyzed by both electrophoretic mobility shift analysis and luciferase assays. We found that the point mutation enhanced the binding affinity of AP-1 to the LCR, thus stimulating the E6/E7 promoter activity. Our results suggest that mutations in binding sites for crucial regulators may be the result of exposure to carcinogens and could induce expression of the E6 and E7 oncogenes.

Human articular chondrocytes immortalized by HPV-16 E6 and E7 genes: Maintenance of differentiated phenotype under defined culture conditions

OBJECTIVE

To establish an immortalized normal human articular chondrocyte line which could be useful for a better understanding of cell molecular mechanisms relevant for the development of new therapeutic approaches in rheumatic diseases.

DESIGN

Chondrocytes from human adult articular healthy cartilage were transfected in primary culture with a plasmid containing two human papilloma virus type 16 (HPV-16) early function genes: E6 and E7, using the highly efficient cationic liposome-mediated (lipofection) procedure. The transfection was verified by reverse transcriptase-polymerase chain reaction analysis of E7 mRNA and by immunofluorence localization of the E7 protein in the cell cytoplasm. The established chondrocyte cell line was examined in monolayer and in two culture conditions that were described to re-induce differentiated characteristics: culturing in a serum-free defined medium supplemented with an insulin-containing serum substitute and seeding on a hyaluronan-based non-woven structured biomaterial. The expression of markers characteristic of cartilage was shown in the mRNA by reverse transcriptase-polymerase chain reaction. Immunohistological staining and Western blotting analysis were performed to evaluate type II collagen synthesis. Proteoglycans deposition was detected by Alcian Blue staining. A Field Emission In Lens Scanning Microscopy was used to look at the morphology of the immortalized cells at very high magnification.

RESULTS

Normal human articular chondrocytes were efficiently transfected leading to the establishment of an immortalized cell line as confirmed by HPV-16 E7 mRNA and protein detection. These cells were able to re-express type II collagen both at mRNA and protein levels under the two defined cultured conditions we used, still maintaining type I collagen expression. Collagen IX mRNA was present only in early primary culture while collagen type X and aggrecan transcripts were always detected. Alcian Blue staining showed a proteoglycan-rich matrix production. The ultrastructural analysis of the immortalized cells revealed that their morphology strictly resembled that of normal chondrocytes.

CONCLUSIONS

The cell line that we obtained may be a useful tool for increasing our knowledge of the genetic and biochemical events involved in the processes of cartilage growth and differentiation. Moreover, it appears to be a suitable model for pharmacological and toxicological studies related to rheumatic diseases relevant to humans.

The DNA repair protein, O(6)-methylguanine-DNA methyltransferase is a proteolytic target for the E6 human papillomavirus oncoprotein

We have previously shown that O(6)-methylguanine-DNA methyltransferase (MGMT), a DNA repair protein that protects tissues against toxic and carcinogenic effects of alkylating agents, is degraded through ubiquitination-dependent proteolysis. Here, we investigated the role of the human papillomavirus (HPV) E6 protein in MGMT degradation. In three pairs of isogenic human tumor cell lines in which a member of each pair expressed the E6 protein through stable transfection (HCT116/HCT116-E6, MCF7/MCF7-E6, and RKO/RKO-E6), we found a consistent 40-55% reduction in the MGMT protein level and its activity in all E6-expressing cells compared with the parent cells (P=<0.05). E6 expression did not, however, alter the levels of MGMT mRNA. Addition of the recombinant MGMT (rMGMT) protein to extracts of HCT116/E6 cells resulted in the binding of E6 to MGMT. Further, the purified E6 protein promoted the degradation of rMGMT in rabbit reticulocyte lysates. Immunoprecipitation assays showed the presence of a ternary protein complex between MGMT, E6, and the cellular ubiquitin-ligase E6-associated protein (E6-AP). Transient transfection of the p53-null H1299 lung tumor cells with an E6 construct also down-regulated the MGMT. The MGMT protein also showed structural features that are compatible for interaction with the E6, and E6-AP components. Collectively, these data suggest that the oncogenic E6 proteins enhance the ubiquitin-dependent proteolysis of MGMT.

Oral squamous cell carcinoma; from an hypothesis about a virus, to concern about possible sexual transmission

Nearly two decades ago, we produced the first evidence for the presence of viral nucleic acids in oral squamous cell carcinoma (OSCC) tissues, hypothesising that there may be a viral involvement in at least some OSCC. Subsequently, human papillomaviruses (HPV) in particular have been implicated in OSCC. Antibody responses to HPV are seen and HPV-DNA detected in tumors by us and many others, the virus being mainly HPV-16, the genotype associated with ano-genital cancer. HPV are seen by in situ hybridisation only in tumour and premalignant tissue but not in surrounding normal mucosa suggesting HPV has a causal relationship. HPV may also be integrated in the host genome, further suggesting a causal role. Studies of patients with OSCC have suggested possible sexual transmission of HPV. Recent studies have indicated that HPV may be aetiologically important particularly in some types of oropharyngeal cancer, at least in tonsillar carcinogenesis, and may represent an alternative pathway in carcinogenesis to the established factors of tobacco and alcohol. We have come a very long way in the two decades since our first suggestion of a viral aetiopathogenesis was greeted with incredulity, and data from on-going studies by the International Agency for Research on Cancer, Johns Hopkins Oncology Center and others are eagerly awaited.

Both Rb and E7 are regulated by the ubiquitin proteasome pathway in HPV-containing cervical tumor cells

High-risk human papillomaviruses (HPVs) are etiologically linked to human cervical and oral cancers. The E6 and E7 oncoproteins encoded by HPV target host cell tumor suppressor proteins. E6 induces proteolysis of p53 through the ubiquitin-proteasome pathway. Recent studies showed that overexpression of E7 caused proteolytic degradation of the tumor suppressor Rb. However, unlike p53, Rb is not regulated by proteolysis in normal cells. In addition, it was unclear whether in its natural context E7 regulates Rb through the ubiquitin-proteasome pathway. Therefore, we sought to determine whether Rb is regulated by the ubiquitin-proteasome pathway in HPV-containing tumor cells. We carried out a detailed analysis in Caski cells, that are derived from HPV-containing cervical cancer tissues. Studies with various protease inhibitors revealed that Rb is regulated specifically by the ubiquitin-proteasome pathway in HPV-containing cervical tumor cells. Several inhibitors of the 26S proteasome significantly increased the level of Rb in the Caski cells. Rb controls cell growth by forming complexes with the E2F-family transcription factors. Surprisingly, in spite of a significant accumulation of the hypophosphorylated form of Rb, no Rb/E2F complex was detectable in the proteasome inhibitor treated cells. Further analysis revealed that there was an increased accumulation of the E7 oncoprotein. We showed that the proteasome inhibitors simultaneously blocked the proteolysis of E7 and Rb, suggesting that E7 is also regulated by the ubiquitin-dependent proteolysis in cervical cancer cells. Taken together, this study suggests that targeted inhibition of Rb proteolysis will be required for restoring Rb function in HPV-containing cervical cancer cells.

Human papillomavirus-associated head and neck squamous cell carcinoma: mounting evidence for an etiologic role for human papillomavirus in a subset of head and neck cancers

There is increasing molecular and epidemiologic evidence that human papillomavirus (HPV) is associated with a distinct subset of head and neck squamous cell carcinomas. The strength and consistency of HPV DNA presence in oropharyngeal cancers bolster the argument that this association is likely causal. HPV-positive tonsillar cancer in particular is emerging as a specific disease entity with distinct molecular, pathologic, and clinical characteristics. Recent data suggest that the incidence of tonsillar carcinoma in the United States is increasing, despite a decline in tobacco use, supporting the existence of other important risk factors such as HPV infection. Individuals with a history of an HPV-associated anogenital cancer and HIV-infected men are at increased risk for tonsillar carcinoma. This review focuses on the recent literature (since 1998) investigating the relationship between HPV and head and neck cancer development, using the current paradigm for causal inference in epidemiologic research attributed to Sir A. Bradford Hill. Data examining the association of HPV with pathogenesis of head and neck squamous cell carcinoma before 1999 were previously reviewed in this journal.

Human papillomavirus type 16 E7 oncoprotein represses transcription of human fibronectin

The E7 oncoprotein encoded by human papillomavirus (HPV) type 16 repressed the transcription of fibronectin, a key component of the extracellular matrix. This repression, detected in several HPV-positive nontumorigenic and tumorigenic cell lines, was abolished when the Cys-X-X-Cys repeats in E7 were disrupted.

A reliability test of standard-based quantitative PCR: exogenous vs endogenous standards

The quantitative measurement of gene expression requires consistent and reliable standards. At least two categories of standards, endogenous and exogenous, are currently used for quantitative PCR. The reliability of these two methods, however, has not been carefully compared. We hypothesized that a reliable quantitative PCR assay would be able to detect known dilutions of a given single-stranded (ss-) cDNA. By measuring VEGF ss-cDNA copy numbers or signal ratios of GAPDH/VEGF in 10x and 100x diluted samples of two original ss-cDNA preparations, an exogenous recombinant DNA standard (a VEGF-mimic plasmid) and an endogenously expressed GAPDH standard were tested for their ability to detect dilution factors. Using the recombinant DNA standard, the dilution factor was detected as 10.3 and 135.0 in 10x and 100x diluted samples of the original CaSki cell ss-cDNA, respectively. The detected dilution factors were 12.3 and 226.2, respectively, in 10x and 100x diluted ss-cDNA from U-251 MG cells. On the other hand, with the endogenous GAPDH standard, the dilution factors were detected as 2.7 and 8.0 in the same 10x and 100x dilutions of the original U-251 MG cell ss-cDNA. Using the same endogenous GAPDH standard, the detected dilution factors were both 4.8 in 10x and 100x dilutions of the original CaSki cell ss-cDNA. It was also found that the number of endogenous copies of GAPDH mRNA was about 1000 times higher than VEGF. The high internal lockup ratio of GAPDH vs VEGF copy numbers and the requirement for additional primer pairs make the use of an abundant endogenous standard an unreliable choice in quantitative or semi-quantitative PCR. In contrast, exogenous standard-based quantitative PCR was shown to be an accurate and reliable method for the quantitation of gene expression.

The E7 oncoprotein of human papillomavirus type 16 interacts with F-actin in vitro and in vivo

We report here that E7 oncoprotein of human papillomavirus type 16 (HPV-16) forms a complex in vivo and in vitro with actin, one of the components of the cellular cytoskeleton. The in vivo interaction was detected by immunofluorescent staining and confocal microscopic examination of normal human oral keratinocytes (NHOK) and CV-1 cells after transient expression of E7 employing the vaccinia virus-T7 RNA polymerase system and by coimmunoprecipitation from an immortalized, nontumorigenic cell line obtained after transfecting NHOK with the cloned HPV-16 DNA genome. The in vitro interaction was detected by cosedimentation of bacterially expressed E7 phosphorylated with rabbit reticulocyte lysate or purified casein kinase II (CKII) prior to incubation with F-actin. This interaction was inhibited if E7 phosphorylation by the rabbit reticulocyte lysate was prevented with heparin, a CKII inhibitor, or if the amino acids Ser-31 and Ser-32 in E7, which are phosphorylated by CKII, were replaced with amino acids that cannot be phosphorylated. Interestingly, a decrease in the amount of polymerized actin occurred in cells expressing E7.