Detection of human papillomavirus (HPV) DNA in oral squamous cell carcinomas by in situ hybridization and polymerase chain reaction

Evaluation of HPV and EBV in OSCC and the expression of p53, p16, E-cadherin, COX-2, MYC, and MLH1

OBJECTIVE

This study aimed to evaluate the presence of human papillomavirus (HPV) and Epstein-Barr virus (EBV) and the expression of p53, p16, E-cadherin, COX-2, MLH1, and MYC in oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

One hundred OSCC specimens were submitted to in situ hybridization for HPV and EBV, and immunohistochemistry for detection of the human proteins.

RESULTS

Thirty-one cases showed HPV in tumor tissue. EBV was not detected in any case investigated. The HPV(+) group demonstrated an increase of staining scores for nuclear p16 (p = .047), cytoplasmic MYC (p = .002), while a decrease for nuclear MLH1 (p = .048), suggesting that HPV may upregulate the expression of the first two proteins and down-regulate the latter.

CONCLUSION

Our findings reinforce the hypothesis of the HPV-related oral carcinogenesis involving the expression of p16 and MYC, and MLH1 suppression. Exclusively cytoplasmic stainings for p16, MLH1, and MYC were also associated with more advanced tumors. Finally, in view of the lack of studies correlating the HPV or EBV infection to the expression of oncoproteins, more researches assessing a broader panel of markers and employing different approaches are still necessary in order to understand the role of these viruses as well as the molecular mechanisms involved in the development and progression of oral carcinomas.

HPV in Head and Neck Cancer-30 Years of History

The interesting history of papillomavirus (PV) research has been reviewed before. The history of human papillomavirus (HPV) in head and neck region starts in 1901 when the contagious transmission of warty lesions into the mouth via oral sex was described, although the confirmation of their viral etiology had to wait until 1907. Ullman was the first to associate the human wart virus with laryngeal warts. Parsons and Kidd described the natural history of oral PV infections in rabbits already in 1942, but these findings were corroborated in humans only recently. Koilocytotic atypia described by Koss and Durfee in 1956 was recognized as a sign of HPV infection in cervical precancer lesions only in 1976-1977 (Meisels and Fortin; Purola and Savia). This prompted systematic surveys of head and neck lesions for the detection of koilocytosis since the late 1970s, and the authors of this communication were the first to propose the HPV involvement in a subgroup of head and neck cancers. Brandsma and Abramson demonstrated HPV16 DNA in tonsillar SCCs in 1989. Since the early 2000s, HPV research of head and neck squamous cell carcinomas (HNSCC) has made impressive progress, confirming that the specific anatomic site plays a key role in determining the susceptibility to HPV infection. The most likely cancer sites associated with HPV are the base of the tongue and palatine tonsils, followed by oral cavity, larynx, and sinonasal mucosa. There is substantial geographic variation in HPV association with HNSCC. Patients with HPV-associated HNSCC are younger, and survival is better than in the absence of HPV.

Conversion of Normal To Malignant Phenotype: Telomere Shortening, Telomerase Activation, and Genomic Instability During Immortalization of Human Oral Keratinocytes

Normal somatic cells terminate their replicative life span through a pathway leading to cellular senescence, which is triggered by activation of p53 and/or pRb in response to critically shortened telomere DNA. Potentially neoplastic cells must first overcome the senescence checkpoint mechanisms and subsequently activate telomerase to propagate indefinitely. Although telomerase activation is closely associated with cellular immortality, telomerase alone is not sufficient to warrant tumorigenicity. Environmental factors, including chemical carcinogens and viral infection, often contribute to aberrant changes leading to tumorigenic conversion of normal cells. Of particular importance in oral cancer development are tobacco-related chemical carcinogens and human papillomavirus (HPV) infection. To describe the molecular mechanisms by which these environmental factors facilitate the genesis of oral cancer, we first established an in vitro multistep oral carcinogenesis model by sequential exposure of normal human oral keratinocytes (NHOK) to "high risk" HPV and chemical carcinogens. Upon introduction of the HPV genome, the cells bypassed the senescence checkpoint and entered into an extended, but not immortal, life span during which telomere DNA continued to shorten. In a few immortal clones surviving beyond the crisis, we found a marked elevation of telomerase activity and stabilization of telomere length. Furthermore, the E6 and E7 oncoproteins of "high risk" HPV disrupted the cell cycle control and DNA repair in immortalized HOK, and enhanced mutation frequency resulting from genomic instability. However, HPV infection alone failed to give rise to a tumorigenic cell population, which required further exposure to chemical carcinogens in addition to HPV infection. Analysis of the data presented suggests that oral carcinogenesis is a series of discrete genetic alterations that result from a continued genotoxic challenge by environmental risk factors. Our in vitro model may be useful for investigators with interest in furthering our understanding of oral carcinogenesis.

Detection of Epstein-Barr and Human Papilloma Viruses in the Middle Ear Squamous Cell Carcinoma

The uncommon ear tumor of middle ear squamous cell carcinoma (MESCC) is thought to be associated with the history of long-term chronic otitis media in the most cases. The main etiologic factor of MESCC is still unclear and may be multifactorial. Infections of Epstein-Barr virus (EBV) and Human Papillomavirus (HPV) are considered as one of the etiologic factor of MESCC. Previous studies have shown that the EBV and HPV have been detected in MESCC. Although the EBV and HPV have been implicated in human malignancies, their roles in pathogenesis of MESCC have not been elucidated. There has never been report on the presence of EBV and HPV in Indonesian MESCC. This study aimed to determine the presence of EBV and HPV in MESCC. Seven paraffin-embedded tissues of speciment from biopsy were analyzed for the presence of EBV and HPV by immunohistochemistry, stained using polyclonal antibody anti EBNA1 and anti HPV. The samples consisted of 4 (57 %) males and 3 (43 %) females with age range of 26-87 years old. Immunohistochemistry result demonstrated that EBV was detected in three of seven (43 %) and HPV in two of seven (29 %) samples. Coexistence of the presence of EBV and HPV were found in one of seven (14 %) sample. The presence of EBV and HPV in MESCC suggests that viral infection may play an important etiologic role in the carcinogenesis of middle ear.

The role of human papilloma virus (HPV) infection in non-anogenital cancer and the promise of immunotherapy: a review

Over the past 30 years, human papilloma virus (HPV) has been shown to play a role in the development of various cancers. Most notably, HPV has been linked to malignant progression in neoplasms of the anogenital region. However, high-risk HPV has also been suggested to play a significant role in the development of cancers in other anatomic locations, such as the head and neck, lung, breast and bladder. In 2006, the first vaccine for HPV, Gardasil, was approved for the prevention of subtypes 6, 11, 16 and 18. A few years later, Cevarix was approved for the prevention of subtypes 16 and 18, the HPV subtypes most frequently implicated in malignant progression. Although increased awareness and vaccination could drastically decrease the incidence of HPV-positive cancers, these approaches do not benefit patients who have already contracted HPV and developed cancer as a result. For this reason, researchers need to continue developing treatment modalities, such as targeted immunotherapies, for HPV-positive lesions. Here, we review the potential evidence linking HPV infection with the development of non-anogenital cancers and the potential role of immunotherapy in the prevention and eradication of HPV infection and its oncogenic sequela.

Evidences suggesting involvement of viruses in oral squamous cell carcinoma

Oral cancer is one of the most common cancers and it constitutes a major health problem particularly in developing countries. Oral squamous cell carcinoma (OSCC) represents the most frequent of all oral neoplasms. Several risk factors have been well characterized to be associated with OSCC with substantial evidences. The etiology of OSCC is complex and involves many factors. The most clearly defined potential factors are smoking and alcohol, which substantially increase the risk of OSCC. However, despite this clear association, a substantial proportion of patients develop OSCC without exposure to them, emphasizing the role of other risk factors such as genetic susceptibility and oncogenic viruses. Some viruses are strongly associated with OSCC while the association of others is less frequent and may depend on cofactors for their carcinogenic effects. Therefore, the exact role of viruses must be evaluated with care in order to improve the diagnosis and treatment of OSCC. Although a viral association within a subset of OSCC has been shown, the molecular and histopathological characteristics of these tumors have yet to be clearly defined.

The role of human papillomavirus in oral squamous cell carcinoma: myth and reality

INTRODUCTION

As the traditional risk factors for oral squamous cell carcinoma, especially tobacco, decline, new potential causative agents become the focus of research. Since the discovery of human papillomavirus (HPV) and its importance in carcinogenesis in cervical cancer, a lot of research has been undertaken to define its role in different types of cancer. In the present study, we evaluate the role of high-risk HPV types in initiation and progression of oral squamous cell carcinoma (OSCC) using a systematic review of the current literature.

MATERIAL AND METHODS

A literature research with the search term "HPV oral squamous cell carcinoma" was performed via PubMed. Results were screened systematically for relevance and classified into the following categories: molecular biology, genetics, clinical aspects, and prevalence. Articles were then further analyzed to assess quality.

RESULTS

The literature research led to 527 results, with an overall HPV prevalence of 30.1 % in OSCCs. The most frequently identified subtypes were HPV-16 and HPV-18 (25.4 and 18.1 %, respectively). Prognostic relevance of HPV was discussed controversially. HPV detection via polymerase chain reaction is the most established method today. Molecular changes according to carcinogenic pathways described for cervix carcinoma were not routinely found in OSCC. In general, no definite role of high-risk HPV is currently deducible from the literature.

CONCLUSIONS

High-risk subtypes 16 and 18 are present in the genome in approximately one third of OSCC. Its role as a causative agent is less clear than the role in oropharyngeal tumors. The infection might not be the cause of carcinogenesis in a significant number of patients but may become proportionally more important with the decrease of the classical risk factors of tobacco and alcohol.

Biology of human papillomavirus infections in head and neck carcinogenesis

The association between human papillomaviruses (HPV) and oral cancer was initially suggested nearly 30 years ago by us. Today, the research interest of head and neck squamous cell carcinoma (HNSCC) has substantially increased. HPV-associated HNSCC is considered a distinct clinical entity with better prognosis than the classical tobacco and alcohol associated cancers. HPV 16 seems to be the main genotype present in HNSCC and it most probably utilizes the same pathways in epithelial cell transformation as established for genital cancer. High-risk HPV E6 and E7 target the well characterized cellular proteins p53 and Rb, respectively. In addition, several other cellular targets of E6 and E7 have been identified. This review gives an overview on the biology of HPV which aids in dissecting the role of HPV in head and neck carcinogenesis. It also summarizes the possible pathways involved in creating new tools for diagnosis and therapy of HPV-associated HNSCC.

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.

The role of cytopathology in diagnosing HPV induced oropharyngeal lesions

HPV detection in fine needle aspirates from suspected head and neck metastasis may be useful in clinching the diagnosis of HPV related oral squamous cell carcinoma. Ascertaining the HPV status of a particular tumor on cytological specimens could be useful for prognostication as HPV-related tumors appear to have a better prognosis and clinical outcome. The various techniques of detection are reviewed.

Incidence of Low Risk Human Papillomavirus in Oral Cancer: A Real Time PCR Study on 278 Patients

Squamous cell carcinoma is the most frequent malignant tumour of the oral cavity. It is widely known that tobacco and alcohol consumption are the major causes of the development of oral squamous cell carcinoma (OSCC). The human papilloma virus infection has also been postulated as a risk factor for squamous cell carcinoma, although conflicting results have been reported. The aim of this study is to evaluate the presence of high-risk and low-risk type human papillomavirus in a large sample of squamous cell carcinoma limited to the oral cavity by means of quantitative real-time polymerase chain reaction. Data were obtained from 278 squamous cell carcinoma limited to oral cavity proper. Sequencing revealed that 5 samples were positive for HPV type 16, 5 for HPV type 11, and 1 for HPV type 6. Human papillomavirus 11 was detected in 5 tumours out of the 278 examined. The prevalence rate for Human papillomavirus 11 was 1.8% (C.I. 0.7–3.9). The matched case-controls analysis indicated that the prevalence among controls did not significantly differ with respect to cases and that Human papillomavirus 11 alone did not correlate with squamous cell carcinoma.

The role of human papillomavirus in head and neck cancer

Over the last 20 years, there has been increasing awareness of a subset of squamous cell carcinomas of the head and neck (HNSCC), i.e. HPV-positive HNSCC. These cancers seem to differ somewhat from HPV-negative HNSCC. Patients with HPV-positive HNSCC tend to be younger and have a lower intake of tobacco and alcohol. Distinct molecular profiles separate them from HPV-negative cancers and show similarities with HPV-positive cervical SCC. There is evidence that HPV-positive HNSCC is a sexually transmitted disease. Patients with HPV-positive HNSCC are often diagnosed at a late stage with large cystic lymph nodes in the neck. HPV-positive HNSCC show an affinity for the oropharynx, especially the tonsils and the base of the tongue, and tend to show low differentiation histopathologically. There is a better prognosis regardless of the treatment regimen for HPV-positive HNSCC compared with HPV-negative HNSCC, and this seems to be related to the immune system. Whether the new vaccines for HPV will protect not only against cervical cancer but also against HPV-positive HNSCC remains unknown.

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.

Oral cancer; the evidence for sexual transmission

The incidence of oral cancer amongst young adults is increasing in many European and high incidence countries. Most oral cancer is aetiologically linked to the use of tobacco and/or alcohol but 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 tumours by us and many others, the virus being mainly HPV-16, the genotype associated with ano-genital cancer. 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. Studies of patients with OSCC have suggested possible sexual transmission of HPV.

Human papillomavirus infections and oral tumors

In the past 20 years, there has been an increasing interest in human papillomaviruses (HPV) because of their potential role in the pathogenesis of malignant tumors. In 1983, we published the first evidence that HPV might be involved in oral squamous cell carcinomas. The identification of morphological similarities between oral and cervical mucosa lead us to this original proposal. In a recent meta-analysis, HPV was indeed confirmed as an independent risk factor for oral carcinoma. To date, totally more than 100 types of HPV have been identified. As in anogenital cancers, HPV type 16 is the most prevalent type in oral carcinomas. The benign oral lesions, associated with HPV infection, include squamous cell papilloma, condyloma acuminatum, verrucca vulgaris and focal epithelial hyperplasia (FEH). Papillomas and condylomas are mostly caused by HPV type 6 or 11, while oral verrucas are associated with the skin types 2 or 4. A family history of FEH has been suggested. The FEH lesions are caused by HPV types 13 and 32, only detected in oral epithelium. In immunocompromised patients, benign HPV-induced lesions are characterized by atypical morphology and the simultaneous detection of multiple HPV types. Oral benign HPV lesions are mostly asymptomatic, and may persist or regress spontaneously.

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.

Human papillomavirus as a risk factor for oral squamous cell carcinoma: a meta-analysis, 1982-1997

OBJECTIVE

Human papillomavirus (HPV) infection is a significant risk factor for uterine cervical carcinoma. However, the role of HPV infection in oral squamous cell carcinoma (OSCC) is less well defined. To determine the significance of the relationship of this virus in the progressive development of oral cancer, we estimated the risk of HPV detection in normal oral mucosa, precancerous oral tissue, and oral carcinoma using meta-analysis.

STUDY DESIGN

Case reports and clinical series published in English-language journals were retrieved by searching MEDLINE (January 1980-August 1998). Review articles were also examined to identify additional studies. Studies that used biochemical, immunologic, microscopic, or molecular analyses to detect HPV in tissue or cells derived from normal oral mucosa (n = 25), benign leukoplakia (n = 21), intraepithelial neoplasia (ie, dysplasia and carcinoma in situ; n = 27), and oral cancer (n = 94) were included in the meta-analysis. Information on sample size, age, sex, method of tissue preservation (ie, fresh, frozen, paraffin-embedded), assay, primer amplification region (early, late), high-risk versus low-risk genotype, and use of tobacco or alcohol was abstracted by one author (C.S.M.).

RESULTS

Data from 94 reports that analyzed 4680 samples were included in the meta-analysis. Analyses made by means of a random-effects model with and without adjustments for assay sensitivity showed increased probability of HPV detection in tissue with precancerous and cancerous features compared with normal mucosa. The likelihood of detecting HPV in normal oral mucosa (10.0%; 95% confidence interval [CI], 6.1%-14.6%) was significantly less than of detecting benign leukoplakia (22.2%; 95% CI, 15.7%-29.9%), intraepithelial neoplasia (26.2%; 95% CI, 19.6%-33.6%), verrucous carcinoma (29.5%; 95% CI, 23%-36.8%), and OSCC (46.5%; 95% CI, 37.6%-55.5%). Adjustment of findings for differences in assay sensitivity indicated that these estimates may be conservative. Overall, HPV was between 2 and 3 times more likely to be detected in precancerous oral mucosa and 4.7 times more likely to be detected in oral carcinoma than in normal mucosa. The pooled odds ratio for the subset of studies directly comparing the prevalence of HPV in normal mucosa and OSCC was 5.37, confirming the trend observed in the overall sample. The probability of detecting high-risk HPVs in OSCCs was 2.8 times greater than that of low-risk HPVs.

CONCLUSION

This meta-analysis indicates that HPV is detected with increased frequency in oral dysplastic and carcinomatous epithelium in comparison with normal oral mucosa. The findings provide further quantitative evidence that oral infection with HPV, particularly with high-risk genotypes, is a significant independent risk factor for OSCC.

Human papillomavirus in head and neck squamous cell carcinoma: are some head and neck cancers a sexually transmitted disease?

There is abundant epidemiologic and virologic evidence that high-risk human papillomaviruses (HPVs) are tumorigenic in human epithelia, particularly in the cervix, where HPV infection is necessary for cancer development. HPV DNA has been detected in a proportion of head and neck squamous cell carcinomas (HNSCCs) in numerous case series. The mere presence of the virus in tumor specimens, by itself, does not imply a causal relationship. However, recent studies support an etiologic role for HPVs in a subset of HNSCC, particularly poorly differentiated tumors arising from Waldeyer's tonsillar ring. Epidemiologic studies have shown that exposure to HPV increases the risk of HNSCC, and HPV infection may interact with alcohol and tobacco exposure in tumor promotion. Molecular studies indicate that transcriptionally active virus is confined to tumor cells. It will be important to clarify further the role that HPV has in HNSCC development, because HPV-based therapeutic vaccines which are currently being developed for cervical cancer may also be of benefit in the management of HNSCC.

Differential gene expression in neoplastic and human papillomavirus-immortalized oral keratinocytes

We have previously demonstrated that normal human oral keratinocytes immortalized by transfection with human papillomavirus type-16 Dna became tumorigenic after exposure to a chemical carcinogen. In an effort to detect differentially regulated genes associated with this transition from the immortal to the malignant phenotype, we employed representational differences analysis (a PCR-coupled subtractive hybridization technique). After analysing 50 colonies, 12 putative messages were identified. Northern analysis comparison using the identified cDNAs as probes was made between normal human oral keratinocyte, papillomavirus-immortalized human oral keratinocytes (HOK-16B), a neoplastic cell line derived from HOK-16B (HOK-16B-BaP-T) and the human oral cancer cell lines Hep-2, SCC-9 and Tu-177. We found that mRNAs encoding for cyclophilin A, c-myc binding protein 1, the heat shock protein 90alpha and one unknown transcript were up-regulated in the oral cancer cell lines analysed as well as in HOK-16B cells. We also detected a downregulation of the mRNAs encoding the skin-derived antileukoproteinase SKALP/elafin, the translationally regulated p23 protein and one unknown transcript. Whether these messages are associated to the neoplastic conversion of human keratinocytes remains to be determined.

Expression of keratin 13, 14 and 19 in oral squamous cell carcinomas from Sudanese snuff dippers: lack of association with human papillomavirus infection

In stratified squamous epithelia, altered expression of keratins (Ks) is one possible marker of malignant potential. In the epithelium of the uterine cervix, presence of human papillomaviruses (HPVs) is increasingly regarded as a marker of risk for cervical cancer. However, a similar role in oral cancer and precancer remains controversial. To address these questions, formalin-fixed, paraffin-embedded oral carcinomas from Sudanese snuff dippers (n=14) and oral carcinomas from Sudanese (n=14), Swedish (n=19) and Norwegian (n=41) non-snuff dippers were examined by immunohistochemistry for expression of K types 13, 14 and 19 using monoclonal antibodies. HPV infection was searched for in all the carcinomas by in situ hybridization (ISH) using the cocktail HPV OmniProbe and the ViraType probe. Carcinomas from Sudanese (snuff dippers/non-snuff dippers) were also examined for HPV infection by polymerase chain reaction (PCR) using the general HPV primers GP5+/GP6+. For the oral carcinomas from snuff dippers, moderate to intense expression of K13 (71%; 10/14), K14 (86%; 12/14) and K19 (93%; 13/14) was found. For the oral carcinomas from non-snuff dippers, weak to moderate expression of K13 (64%; 47/74), K14 (43%; 32/74) and K19 (45%; 33/74) was found. HPV DNA was not detected in any of the carcinomas from three countries when examined by ISH. The Sudanese (from snuff dippers/non-snuff dippers) oral carcinomas were also negative for HPV DNA with the PCR. The present study shows that (i) there is a high level of expression of K13, K14 and K19 in oral carcinomas from snuff dippers compared to those from non-snuff dippers, (ii) this high level of expression may arise from dysregulation of keratinocyte proliferation and maturation caused by damaging effects of snuff, (iii) the HPV genome is not found in Sudanese (snuff dippers/non-snuff dippers), Swedish or Norwegian oral carcinomas, and (iv) this may suggest that these viruses do not play a prominent role in the aetiology of oral carcinomas from these countries.

Human papillomavirus and head and neck cancer: epidemiology and molecular biology

BACKGROUND

Human papillomaviruses (HPV) are known to cause cancers of the cervix and other anogenital tract sites. Molecular biology has provided some evidence as to the specific mechanisms involved in the HPV-related carcinogenesis. Epidemiologic and molecular biology studies have also suggested that HPV infection may be associated with cancers of the head and neck.

METHODS

This review summarizes the biology of HPV and its potential etiologic role in head and neck cancer. Published reports were used to determine the prevalence of HPV in benign, precancerous, and neoplastic lesions of the oral cavity, pharynx, and larynx. The prevalence was also examined by head and neck site, HPV type, and method of HPV detection. In addition, the occurrence of HPV in normal head and neck tissue, epidemiologic factors related to HPV infection, and clinical implications are discussed.

RESULTS

Overall, the frequency of HPV in benign and precancerous lesions ranged from 18.5% to 35.9%, depending upon the detection methodology. Based upon the most sensitive method of detection, polymerase chain reaction (PCR), the overall prevalence of HPV in head and neck tumors was 34.5% (416 of 1205 tumors). The majority of HPV-positive tumors contained the "high risk" HPV types 16 (40.0%) and 18 (11.9%). Among head and neck sites, HPV was most often detected in tumors of the oral cavity (59%), followed by the pharynx (43%), and larynx (33%). The frequency of HPV positivity in oral samples from healthy individuals ranged from 1% to 60%. A limited number of descriptive and analytic epidemiologic studies have indicated that age (<60 years) and sex (male) were associated with the presence of HPV in the tumor, whereas tobacco and alcohol use were not. The relationship between HPV and survival is unclear, with few comprehensive studies currently available.

CONCLUSIONS

The prevalence of HPV, particularly the high-risk types, suggests a potential etiologic role for the virus in head and neck cancer. Molecular biology has provided important data on the interaction of the HPV oncoproteins with genes important in cell cycle control. Nonetheless, more basic research is needed to describe the physical state of the virus in a variety of cell types and the interaction with other genes. In addition, epidemiologic research is required to further understand the association between HPV and demographic and other risk factors as well as possible routes of transmission. Finally, much work is warranted to provide a definitive assessment of the prognostic significance of HPV in head and neck cancer.

The high risk human papillomaviruses and oral cancer: evidence for and against a causal relationship

Oncogenic human papillomaviruses (HPVs) have been detected in oral squamous cell carcinoma (SCC). HPV16 is the most frequently detected HPV type in oral SCC and is present in up to 22% of cases, either alone or in combination with other HPV types. HPV18 is present in up to 14% of cases. HPV16 and HPV18 are present together in approximately 6% of cases. However, HPV16 and 18 are also detected in normal oral mucosae (10% and 11% of subjects, respectively). These data suggest that high risk HPV infection may be a co-factor in oral carcinogenesis and that latent HPV infection of the oral mucosa is common. A role for HPV infection in oral carcinogenesis is supported by the ability of high risk HPVs to immortalize oral keratinocytes in vitro. Immortalization may involve (i) deactivation of pre-formed tumor-suppressor proteins by viral oncoproteins, (ii) blocking of tumor-suppressor gene transcription as a result of HPV oncogene insertion or (iii) stimulation of cellular oncogene transcription by the upstream insertion of HPV-derived transcription activating sequences. Hence, infection of oral keratinocytes with high risk HPV may be involved in the pathogenesis of some oral SCCs although the evidence implicating HPV in oral carcinogenesis is, at present, mainly circumstantial.

Detection of human papillomavirus in esophageal squamous cell carcinoma

BACKGROUND

Human papillomavirus (HPV) DNA has been identified in esophageal carcinomas. However, the incidence of HPV varies significantly in different geographic locations. In the current study, neoplasms from two separate geographic regions were analyzed for the presence of HPV DNA:

METHODS

One hundred and ten esophageal squamous cell carcinomas, 83 from Beijing, China and 27 from Cincinnati, Ohio, were examined for the presence of HPV DNA: In situ hybridization and polymerase chain reaction (PCR) using both consensus primers for the HPV L1 gene and type specific primers for the E6 gene of HPV types 6, 16, and 18 were performed.

RESULTS

In situ hybridization failed to demonstrate any HPV type (6, 11, 16, 18, 31, 33, or 35) in any tumor specimen. Likewise, PCR using consensus primers for the HPV L1 gene was negative in all samples. Three of the Chinese specimens (4.29%) were positive for HPV using E6 type specific primers. One tumor contained HPV type 6 DNA, whereas the other 2 contained HPV type 16 DNA. One Cincinnati tumor (4.35%) was positive for HPV 16 by type specific primer. None of the specimens contained HPV 18 DNA.

CONCLUSIONS

The incidence of HPV DNA in esophageal carcinoma specimens from Beijing, China and Cincinnati, Ohio is similar. The incidence of HPV in tumors from Beijing is significantly lower than that reported for those from other regions of China where the incidence of esophageal cancer is higher. Thus, although HPV may play a role in esophageal carcinogenesis, this role may be more pronounced in those regions of the world with a high incidence of the disease, and may be less important in areas with moderate or low risks for esophageal cancer.

Detection of human papillomavirus in esophageal squamous cell carcinoma

BACKGROUND

Human papillomavirus (HPV) DNA has been identified in esophageal carcinomas. However, the incidence of HPV varies significantly in different geographic locations. In the current study, neoplasms from two separate geographic regions were analyzed for the presence of HPV DNA:

METHODS

One hundred and ten esophageal squamous cell carcinomas, 83 from Beijing, China and 27 from Cincinnati, Ohio, were examined for the presence of HPV DNA: In situ hybridization and polymerase chain reaction (PCR) using both consensus primers for the HPV L1 gene and type specific primers for the E6 gene of HPV types 6, 16, and 18 were performed.

RESULTS

In situ hybridization failed to demonstrate any HPV type (6, 11, 16, 18, 31, 33, or 35) in any tumor specimen. Likewise, PCR using consensus primers for the HPV L1 gene was negative in all samples. Three of the Chinese specimens (4.29%) were positive for HPV using E6 type specific primers. One tumor contained HPV type 6 DNA, whereas the other 2 contained HPV type 16 DNA. One Cincinnati tumor (4.35%) was positive for HPV 16 by type specific primer. None of the specimens contained HPV 18 DNA.

CONCLUSIONS

The incidence of HPV DNA in esophageal carcinoma specimens from Beijing, China and Cincinnati, Ohio is similar. The incidence of HPV in tumors from Beijing is significantly lower than that reported for those from other regions of China where the incidence of esophageal cancer is higher. Thus, although HPV may play a role in esophageal carcinogenesis, this role may be more pronounced in those regions of the world with a high incidence of the disease, and may be less important in areas with moderate or low risks for esophageal cancer.

Human papillomavirus expression in oral mucosa, premalignant conditions, and squamous cell carcinoma: a retrospective review of the literature

OBJECTIVES

The literature of human papillomavirus detection in normal oral mucosa and oral lesions associated with the dysplastic progression of epithelium was reviewed to help define the role of this virus in the development of oral squamous cell carcinoma.

STUDY DESIGN

All available data from published studies were analyzed by chi-square test for association between the human papillomavirus and age, gender, race, DNA type, location, lesional dysplastic progression, method of detection, tissue preservation, and use of tobacco and alcohol.

RESULTS

Human papillomavirus was identified with increasing frequency in normal oral mucosa (13.5%), benign leukoplakia (14.8%), intraepithelial neoplasia (18.5%), squamous carcinoma (26.2%), and verrucous carcinoma (27%). It was detected in oral squamous cell carcinoma significantly (p < 0.005) more often (37.1%; 122 of 329) in studies that used a high sensitivity assay (polymerase chain reaction) than studies that used moderate sensitivity assays (25.2%; 84 of 334) (e.g., Southern blot hybridization) and low sensitivity assays (16.9%; 61 of 362) (e.g., immunohistochemistry, in situ hybridization). Human papillomavirus DNA was detected significantly more often (p < 0.001) in frozen oral squamous cell carcinoma (51.6%; 115 of 223) than paraffin-embedded tissue (21.7%; 136 of 628). High-risk human papillomaviruses (2, 16, 18) were detected in 81.4% of OSCCs that contained the virus compared with low-risk human papillomavirus genotypes (6, 11) in 17.9% of oral squamous cell carcinoma that contained the human papillomavirus (p < 0.001). In studies that analyzed the use of chemical cofactors, the use of tobacco and alcohol (87.3%) was associated more often with oral squamous cell carcinoma than the presence of human papillomavirus (51.3%), however, the difference was not significant.

CONCLUSION

High-risk human papillomavirus genotypes have a significant association with oral squamous cell carcinoma. However, the presence of this virus in a high proportion of oral normal mucosa makes the virus alone a poor prognosticator of progression to malignancy.

Prevalence of mucosotropic human papillomaviruses in squamous-cell carcinoma of the head and neck

The prevalence of mucosotropic human papillomavirus (HPV) DNA in 63 squamous-cell carcinomas (SCC) from different anatomic sites in the head and neck was determined by general primer-mediated polymerase chain reaction (GP-PCR). HPV DNA was detected in 20.6% of SCC. Additional type-specific PCR for HPV 6, 11, 16, 18, 31 and 33 demonstrated the presence of HPV 16 alone in these carcinomas. HPV 16 was also detected in normal epithelium from the resection margins of the majority of HPV-positive SCC. HPV status did not correlate with tumour site, whether primary or recurrent, TNM stage, metastases, degree of differentiation, smoking or alcohol history, fate or survival.

Viral infections in the immunocompetent patient

Human herpesviruses and human papillomaviruses are ubiquitous and may cause an array of oral disease. Herpesviruses are unique because recurrent localized disease occurs after the primary infection. Human papillomaviruses are known for their ability to produce benign epithelial proliferations and increasingly are implicated in the development of oral cancer. This article reviews the pathogenesis of common oral lesions induced by these viruses.

Prevalence of human papillomavirus 16 and nucleolar organizer region counts in oral exfoliated cells from normal and malignant epithelia

This study was designed to identify the prevalence of human papillomavirus 16 (HPV 16) in oral exfoliated cells from 26 patients with oral cancer and matched healthy volunteers with the use of polymerase chain reaction. In addition, the value of a silver staining technique for nucleolar organizer regions (AgNORs) was also investigated. HPV 16 was detected in 30.8% of the cancer lesions, 26.9% of the unaffected sites, and 15.4% of samples from normal mucosa. AgNOR counts on the same cases were analyzed. Although AgNOR counts are useful in distinguishing between normal and malignant oral exfoliated cells, they provided no additional prognostic information for oral cancer. However, when AgNOR counts were compared with HPV 16-positive and HPV 16-negative counts in cancer lesions, AgNOR counts were higher in HPV-positive lesions. These findings suggest that HPV 16 may play a role in tumor cell proliferation, but it is unlikely to play a significant role alone in the cause of oral cancer. Therefore evidence of HPV 16 infection in oral malignant neoplasms should be cautiously interpreted.

A polymerase chain reaction (PCR) investigation of oral verrucae which contain HPV types 2 and 57 by in situ hybridization

The polymerase chain reaction (PCR) and direct DNA sequencing have been used to identify strain variants of HPV types 2a/57 in formalin-fixed sections of human oral verrucae, where the virus had previously been detected by both immunofluorescence and in situ hybridization. By employing type-specific and type-common PCR primers we show that these lesions contain a mixture of viral DNAs which vary by up to 27% in DNA sequence, in a region where the variation between HPV types 2a and 57 is only 4%. The extra discriminatory power of fluorescent sequencing indicates that the lesions may also contain wild-type HPV2a/57 DNA which could provide a helper function for defective viral DNA molecules or indicate a mosaic origin for the lesions.

Search for evidence of three viral agents in radicular (periapical) cysts with immunohistochemistry

Sections from 20 paraffin-embedded radicular cysts and positive-control subjects were subjected to immunostaining procedures after treatment of the sections with polyclonal antibodies was performed to search for evidence of human papilloma virus and herpes viruses 1 and 2 in the lining epithelium. All 20 specimens examined were negative for the presence of all three viruses.

Association between proliferative verrucous leukoplakia and infection with human papillomavirus type 16

Proliferative verrucous leukoplakia (PVL) is a recently described clinical entity characterized by multifocal oral lesions that frequently progress to oral cancer despite abstinence from tobacco use by most patients. To determine if this condition is associated with human papillomavirus (HPV), a polymerase chain reaction (PCR) for HPV DNA was performed on 9 lesions from 7 patients with PVL, histologically diagnosed with focal keratosis (1), papilloma (1), epithelial dysplasia (5) and squamous cell cancer (2). Eight (89%) were HPV positive, 7 for HPV 16. For comparison, we studied 55 non-PVL-associated oral specimens, including 24 oral squamous cell cancers. Of the cancers, 8 (33%) were HPV positive, 4 for HPV 16. These data suggest that HPV 16 infection may play an important role in the pathogenesis of PVL-associated oral dysplasia and possibly cancer, but is found in only a small proportion of the more common, non-PVL associated-oral lesions.

Human papillomavirus (HPV) is rarely present in normal oral and nasal mucosa

The association between human papillomavirus (HPV) and cervical carcinomas is well known. HPV has been found in oral carcinomas and paranasal papillomas, and the question of a causal role of HPV has yet to be answered. Reports on the frequency of HPV in oral and paranasal sinus tumours should be considered in relation to the frequency of HPV in normal oral and nasal mucosa. In the present study 61 normal individual had oral smears taken and 48 had nasal smears. These were examined for HPV by DNA amplification with HPV consensus primers. HPV was not found in the oral mucosa, while a single individual harboured HPV in the nasal mucosa. It is concluded that HPV is rarely present in normal oral and nasal mucosa.

Detection of HPV DNA in oral carcinoma using polymerase chain reaction together with in situ hybridization

This study determined the prevalence of human papillomavirus 16/18 DNA in deparaffinized oral carcinoma specimens on slides with the use of the different sensitivities of in situ hybridization and a technique that combines polymerase chain reaction and in situ hybridization. Human papillomavirus DNA was not detected in the 30 biopsy specimens analyzed by in situ hybridization alone using biotinylated DNA probes specific for human papillomavirus 16/18. Twenty of 30 specimens (66.7%) were found to have human papillomavirus DNA (p < 0.001) with the use of the polymerase chain reaction-in situ hybridization technique. Human papillomavirus 16 was detected in 18 of 26 specimens (69.2%), and 7 of 25 carcinomas (28%) were found to contain human papillomavirus 18. Dual infections were present in 5 of 21 (23.8%) specimens. Human papillomavirus DNA was more prevalent in men (75%) than women (57.1%). However, there was no difference in the mean age of patients with oral carcinoma (men, 67.8 years; women, 67.5 years) who had human papillomavirus and those who did not (67.2 years). Carcinomas associated with dual infections occurred at a lower mean age (59.4 years) than those associated with a single human papillomavirus type (p < 0.005). We conclude that the polymerase chain reaction-in situ hybridization technique enhances our ability to demonstrate human papillomavirus types highly associated with oral squamous cell carcinoma.

Screening for human papillomavirus infections in esophageal squamous cell carcinomas by in situ hybridization

BACKGROUND

Infections with specific types of human papillomavirus (HPV) have been closely linked with human squamous cell carcinomas, those of the anogenital tract in particular. Increasing number of reports also suggest that HPV infection could be a risk factor for esophageal cancer. However, most of the previous studies on HPV involvement in esophageal carcinomas have included only small numbers of biopsy specimens, thus necessitating additional studies based on extensive series of esophageal samples.

METHODS

A series of 776 biopsy specimens derived from 363 patients who had undergone esophagectomy for squamous cell carcinoma in the high-incidence area of China were analyzed for the presence of HPV DNA by screening and specific typing in situ hybridization with biotinylated HPV DNA probes.

RESULTS

Under low-stringency conditions, 85 (23.4%) tumors were demonstrated to contain HPV DNA: Positive signals were found on the nuclei of cancer cells in 71 (19.6%), in the surrounding epithelial cells with hyperplastic or dysplastic changes in 13 (3.6%), in the cancer cells and the surrounding epithelial cells in 10 (2.8%), and in the resected margins in 1 (0.3%). Thirty-four (40%) of the 85 HPV-positive tumors were shown to contain at least one type of HPV 6, 11, 16, 18, or 30 DNA sequences. HPV 16 was the type found most frequently, occurring in 18.8% of the 85 HPV-positive specimens. In addition to the primary tumors, HPV DNA sequences were found in 12.3% (7 of 57) of the lymph node metastases.

CONCLUSION

The results confirm the previously reported HPV involvement in esophageal squamous cell lesions and implicate HPV as a potential etiologic agent in the multifactorial pathogenesis of esophageal carcinoma.

Detection of Mycobacterium leprae DNA in formalin-fixed, paraffin-embedded samples from multibacillary and paucibacillary leprosy patients by polymerase chain reaction

BACKGROUND

Diagnosis of paucibacillary leprosy is often difficult. A method that could confirm the diagnosis is the polymerase chain reaction (PCR) of M. leprae DNA. This reaction was applied to biopsied tissues of leprotic patients to determine the suitability and sensitivity of the reaction.

METHODS

Biopsy samples were taken from previously untreated patients with multibacillary (5 patients) and paucibacillary (3 patients) leprosy, fixed in formalin, and embedded in paraffin. DNA was extracted from paraffin blocks and PCR applied. The sensitivity of the PCR method was tested by using the serially diluted DNA sample as the template.

RESULTS

All eight patients showed a positive PCR for M. leprae DNA. The sensitivity was such that a single organism of M. leprae, as counted by staining of the acid-fast bacilli was identified by the PCR.

CONCLUSIONS

The PCR method is simple, sensitive, specific, and does not require the use of radioisotopes. It can be applied to the unequivocal diagnosis of paucibacillary leprosy which is difficult by other means. The diagnosis can be obtained within 10 hours.

The polymerase chain reaction. Applications in dermatology

Within the space of the last 5 years, application of the revolutionary in vitro method of deoxyribonucleic acid (DNA) amplification known as the polymerase chain reaction (PCR), has become ubiquitous. The rapidly increasing number of clinical and research articles utilizing this technology, both in the dermatologic and general medical literature, requires one to have at least a basic understanding of how the PCR is conducted, what it has to offer, and the potential shortcomings. Such knowledge will hopefully allow a more critical appraisal of an increasingly complex literature. This review aims to describe the methodology and medical applications of this powerful technique with special consideration to the increasing role PCR may have on dermatologic research and practice.

Oncogenes, tumor suppressors and viruses in oral squamous carcinoma

The pathogenesis of oral squamous cell carcinoma involves recognised carcinogens in tobacco and/or alcohol but other factors, including viruses, may also have a role. This paper reviews the gene changes revealed in oral carcinoma, the evidence implicating viruses, and mechanisms whereby viruses may affect gene function.

Human herpes simplex-1 and papillomavirus type 16 homologous DNA sequences in normal, potentially malignant and malignant oral mucosa

We have tested a range of normal, potentially malignant and malignant oral mucosal biopsies tissues by Southern blot hybridisation analysis for the simultaneous presence of HSV-1 and HPV type 16 DNA sequences, both of which have been implicated as risk factors in oral carcinogenesis. The results show that: (1) 2/4 patients with lichen planus, 2/4 patients with non-specific keratosis, 1/8 patients with oral carcinoma and 3/5 biopsy specimens of normal oral mucosa contained DNA sequences homologous to the HSV-1, Bam HI-G fragment. (2) HPV-16 homologous DNA sequences were detected in 3/4 patients with lichen planus, 4/4 non-specific keratosis, 4/8 oral carcinomas and in 3/5 biopsy specimens of normal oral mucosa. (3) Overall, only 5 patient biopsy specimens were positive for both HSV-1 and HPV-16 homologous DNA sequences; 2 lichen planus, 2 non-specific keratosis and 1 normal. The data cannot exclude a "hit and run" oncogenic mechanism for HSV but suggest that if HSV-1 and HPV-16 play a synergistic role in the development of oral cancer this may be an early event. Indeed, the data suggest HSV might be more frequently found in potentially malignant lesions than in carcinoma.

Influence of fixation on human papillomavirus DNA detection in frozen and embedded paraffin lesions by in situ hybridization with biotinylated probes

Series of frozen or paraffin-embedded tissues from various body sites, taken from non-immunosuppressed or immunosuppressed patients with persistent papilloma lesions were examined for the presence of group specific antigen from human papillomavirus (HPV) by indirect immunofluorescence or HPV DNA by in situ hybridization with biotinylated probes. We have shown that it is possible to detect HPV DNA after fixation of tissues in neutral formalin, Bouin's or Baker's solution. However, the sensitivity was reduced as compared to frozen tissues. The HPV DNA was detected in nuclei of heavily infected epithelial cells such as plantar or hand warts or in dispersed cells containing high copy numbers of HPV DNA from lesions such as squamous cell carcinomas or keratoacanthomas. In premalignant or malignant lesions of both immunosuppressed or non-immunosuppressed patients, HPV DNA was rarely detected after fixation. HPV types commonly described for skin and genital samples were identified in non-immunosuppressed patients, whereas in transplant recipients oncogenic HPV type 16 was identified in benign warts as well as in premalignant or malignant lesions. Positive reactions with several HPV types were more frequent in lesions from grafted patients than from the normal population. Virus antigen was detectable more frequently in frozen sections than in fixed tissues. Our findings indicate that in situ hybridization is an appropriate and rapid technique to study the presence of HPV infection. However, numerous controls are needed to avoid misinterpretations.

Human papillomavirus type 16 in an oral squamous carcinoma and its metastasis

DNA was extracted from fresh frozen tissues of eight patients with primary oral squamous carcinoma. Samples of normal oral mucosa were available in seven cases and metastatic tumor in two cases. The samples were probed for human papillomavirus types 16 and 18 by Southern hybridization. In one case of squamous carcinoma of the floor of the mouth, human papillomavirus type 16 was identified in the primary tumor and a lymph node metastasis, but it was not detectable in normal oral mucosa from this patient. Human papillomavirus DNA was not detected in any other sample of primary tumor, metastasis, or normal oral mucosa. Restriction enzyme digests of the human papillomavirus positive primary tumor and its metastasis revealed that the viral DNA was identical to the prototype human papillomavirus type 16 and present at 50 to 100 copies per cell in an episomal state with no evidence of integration into the host DNA. Compared to the human papillomavirus DNA in the primary tumor, the viral DNA in the metastasis was of the same type, in the same physical state, and at the approximately the same copy number. The consistent maintenance of human papillomavirus DNA in metastases from human papillomavirus positive primary tumors supports the hypothesis that human papillomaviruses are cofactors in the pathogenesis of some carcinomas.

Infectious agents in the etiology of esophageal cancer

Extensive epidemiological and experimental studies have suggested that some chemical agents, nutritional deficiencies, and physical factors are associated with the development of esophageal cancer (EC). Recent evidence also suggests an etiologic role of certain microorganisms in esophageal carcinogenesis either by producing carcinogens or promotors or by acting directly on the host cells. The mutagenic and carcinogenic effects of several fungi and bacteria isolated from the grains and foodstuffs in high-risk areas have been shown by in vitro and in vivo studies. Certain viruses, e.g., human papillomavirus, herpes simplex virus, cytomegalovirus, and Epstein-Barr virus, have been implicated in the pathogenesis of a variety of human cancers, and all of them are known to produce tumors in animals and cell transformation in vitro. These viruses also have been shown to infect the esophageal epithelium. Therefore, although many of the key issues of their mechanisms of action are unclear as yet, they should be considered potential etiologic agents of EC. The present review summarizes the data available on the etiology of EC, emphasizing the current evidence implicating an etiologic role of microorganisms in the pathogenesis of this malignancy.

Human papillomavirus involvement in esophageal precancerous lesions and squamous cell carcinomas as evidenced by microscopy and different DNA techniques

A series of 71 surgically resected esophageal squamous cell carcinomas, including 51 cases of formalin-fixed samples and 20 cases of fresh biopsy specimens derived from the high-incidence area of esophageal cancer in China, were systematically analyzed for the presence of human papillomavirus (HPV) infections by light microscopy, electron microscopy (TEM), in situ DNA hybridization, Southern blot hybridization, and polymerase chain reaction (PCR) techniques. On light microscopy, HPV-suggestive lesions were found in a total of 49.0% (25 of 51) of the specimens, including the flat type (22 of 51) and, less frequently, an inverted one (2 of 51). Of the 51 formalin-fixed, paraffin-embedded specimens, 43.1% (22 of 51) contained HPV DNA sequences by in situ hybridization. Of the positive cases, HPV 6 was present in three (5.9%), HPV 11 in three (5.9%), HPV 16 in eight (15.7%), HPV 18 in six (11.8%), double infections with HPV 11/18 in one (2.0%), and HPV 16/18 in one. In most cases the HPV-positive signals were localized in the hyperplastic and/or dysplastic epithelium adjacent to invasive carcinomas. In two specimens, however, HPV DNA sequences were found in the frankly invasive lesions, one being HPV 6 and the other HPV 18. On TEM, HPV-like particles located in the nuclei of koilocytotic cells were demonstrated in two of the five specimens previously shown to be HPV-positive by in situ hybridization. By means of the PCR technique, all specimens positive for HPV by in situ hybridization also contained amplified HPV sequences. Moreover, three additional samples negative by in situ hybridization were found to contain HPV 11 DNA sequences. Of the 20 DNA samples extracted from the fresh carcinoma samples (containing some surrounding tissues as well) 9 were shown to contain HPV DNA sequences by Southern blot hybridization under low-stringency conditions. Of these, eight samples remained positive when hybridized with the probe cocktail of HPV 11, 16, 18, and 30 DNA under high-stringency conditions. HPV DNA sequences in these carcinoma specimens appeared to be present mainly in an integrated form. The present results confirm the HPV involvement in esophageal squamous cell lesions and suggest that HPV infection might be an important etiologic factor in the pathogenesis of esophageal cancer, most probably acting synergistically with other carcinogenic factors.

Assessment of p53 protein expression in normal, benign, and malignant oral mucosa

Recent studies have shown the accumulation of high levels of p53 protein to be associated with malignant disease, within a range of tissues. This paper assesses p53 expression in oral mucosal disease. Biopsies were obtained from a range of oral disorders which included normal, benign, premalignant, and malignant oral tissue. In addition, oral smears were obtained from a limited number of patients with biopsy-proven oral cancer. Expression of the p53 protein was assessed using the polyclonal antibody CM1, together with a standard immunoperoxidase technique. A total of 37 oral cancers were assessed, of which 20 were found to express the p53 protein (54 per cent of cases). The p53 protein was not identified in normal, benign, or premalignant oral mucosa (54 cases). The identification of p53 within biopsies of oral mucosal lesions would appear to correlate with oral malignancy.