Synergism of herpes simplex virus and tobacco-specific N'-nitrosamines in cell transformation

Detección del virus herpes simplex y del virus de epstein-barr en los carcinomas de células escamosas de vías aerodigestivas superiores

OBJECTIVE

Previous studies have investigated the role of viruses in tumor origin of head and neck cancer. Despite this, mechanis of viral carcinogenesis remain unclear. The aim of this study is to determine the prevalence of herpes simplex virus (HSV) and Epstein-Barr virus (EBV) in malignant laryngeal and oropharyngeal lesions.

MATERIAL AND METHODS

Fresh frozen specimens of 28 laryngeal and oropharyngeal squamous cell carcinomas were studied. The presence or absence of HSV and EBV was determined with polymerase chain reaction (PCR) assays.

RESULTS

None of the samples showed evidence for EBV DNA. One tonsilar carcinoma case (3.5%) was positive for HSV DNA detection.

CONCLUSIONS

These results do not support HSV and EBV as etiological factors in head and neck cancer.

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.

Smokeless tobacco extracts modulate exogenous gene expression in early passage cultured human oral epithelial cells: an in vitro system to study chemical and viral enhancer/promoter interaction

The increased risk for cancers of the oral cavity from smokeless tobacco use may reflect the interaction of tobacco with genetic factors, such as oncogenes, and other exogenous factors, such as viruses. An in vitro system was developed based on expression of the chloramphenicol acetyltransferase (CAT) reporter gene to study interactions of chemical treatments with viral enhancer/promoters in early passage cell cultures of oral cavity-derived epithelial cells. Expression of CAT in transfected cells was significantly greater with CAT under the control of the cytomegalovirus immediate early enhancer/promoter (pCEP4/CAT) compared to the Rous sarcoma virus long terminal repeat enhancer/promoter (pRSV-cat) and the simian virus 40 (SV40) early promoter (pSV2-cat). No CAT expression was detected using corresponding control plasmids without the CAT reporter gene. Using this system, smokeless tobacco extracts prepared from either dry snuff or moist snuff delayed maximum CAT expression from Day 4 to Day 5, with sustained, significantly increased CAT expression at 12 days compared to the declining CAT expression observed in untreated control cells. Smokeless tobacco extracts can modulate intracellular gene expression. This system provides an in vitro model to test specificity of toxic agents on enhancer/promoter activity and the interaction on exogenous gene expression.

Prevalence of herpes simplex virus in malignant laryngeal lesions

OBJECTIVE

To determine the prevalence of herpes simplex virus (HSV) in malignant laryngeal lesions.

STUDY DESIGN

Retrospective review.

MATERIALS AND METHODS

Paraffin-embedded, histologically confirmed specimens containing benign laryngeal lesions, squamous cell carcinoma of the larynx, and squamous cell carcinoma of the oral cavity were identified from archived surgical specimens. Biopsies of normal-appearing oral cavity tissue were also obtained from fresh-frozen cadavers. These tissues were analyzed for the presence of HSV DNA using polymerase chain reaction techniques. Patient charts were reviewed for patient demographics, risk factors, stage, clinical course, treatment, and outcome.

RESULTS

HSV was detected in nine laryngeal squamous cell carcinomas (75%) and in none of the benign laryngeal lesions (P = .0001). HSV was also found in three oral cavity squamous cell carcinomas (25%) and in none of the controls (P = .049).

CONCLUSION

HSV is more prevalent in squamous cell carcinoma of the larynx and oral cavity than in their respective control groups, suggesting a role for carcinogenesis. HSV is more prevalent in squamous cell carcinoma of the larynx than of the oral cavity. Further studies to determine the role of HSV as a cocarcinogen and its interrelationship with other environmental factors in laryngeal cancer are warranted.

Evaluation of the effect of smokeless tobacco purified products and extracts on latent Epstein-Barr virus

Numerous chemical tumor promoters induce latent Epstein Barr virus (EBV) to active replication. The effect of smokeless tobacco purified products N-nitrosonornicotine (NNN), 4-(N-methyl-N-nitrosamine)-1-3-pyridinyl)-1-butanone (NNK), benzo(a)pyrene (BaP), and smokeless tobacco extracts (dry snuff, moist snuff, and loose leaf tobacco) was tested for induction of latent EBV in Raji cells using fluorescence-activated cell sorter flow cytometry detection of the restricted component of EBV early antigen (EA-R). Concentrations of smokeless tobacco purified products or preparations were used that have carcinogenic effects in animal cell lines. There was no discernible effect for the 6-7-day duration of treatment on viability of Raji cells, or on induction of latent EBV in Raji cells. Results were comparable using paraformaldehyde- or acetone-fixed cells. There does not appear to be an in vitro effect of smokeless tobacco constituents on EBV-infected lymphocytes that may contribute to development of oral cancers.

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.

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.