Attenuation of the natural course of herpes simplex virus infection in human oral epithelial cell cultures by smokeless tobacco extracts suggests the possibility of a synergistic mechanism for carcinogenesis

[Smokeless tobacco]

Use of smokeless tobacco (ST) (chewing tobacco and snuff) can lead to a number of consequences detrimental to health. ST rapidly delivers high doses of nicotine, which can lead to dependence and is also a source of carcinogenic nitrosamines. Changes usually develop in the mouth area where the ST is most often placed. Non-malignant oral lesions include leuko-oedema, hyperkeratotic lesions of the oral mucosa and localised periodontal disease. Oral premalignant lesions are leukoplakia, erythroplakia, submucosal fibrosis and lichen planus. Betel chewing, with or without tobacco, may increase the incidence of oral cancer. There is conflicting evidence with regard to snuff users about the risk of oral and gastro-oesophageal cancer. ST use is a risk factor for pancreatic cancer and may increase the risk of fatal myocardial infarction and ischemic stroke. During pregnancy, ST is associated with an increase in pre-eclampsia, preterm delivery and stillbirth. Nicotine replacement therapy and bupropion reduce withdrawal symptoms and tobacco craving during ST cessation. However, they have not been shown to help long-term abstinence. Information concerning the potential hazards of ST products should be incorporated into educational programmes to discourage its use and to help users to quit. Smokeless tobacco is not recommended to help smoking cessation.

Head and neck cancer associated with herpes simplex virus 1 and 2 and other risk factors

We investigated whether herpes simplex viruses, HSV-1 and HSV-2, are cofactors of head and neck cancer (HNC) in association with tobacco, alcohol, or HPV-16 infection. The study included 164 HNC cases and 295 controls. Serologic tests were used to distinguish HSV-1 and HSV-2. Antibodies to anti-VLP HPV-16 and HPV-16 E6 and E7 were evaluated by ELISA. After adjusting for age, tobacco, alcohol use, and number of sexual partners, risk of cancer was not significantly increased in those with HSV-1 [adjusted odds ratio (OR)=0.7] or HSV-2 (OR=0.8) compared to HSV-negative patients. Although heavy use of tobacco, alcohol and HPV-16 infection was associated with an increased risk of HNC, the adjusted risk among those infected with HSV-1 or HSV-2 lowered the odds compared to those who were not infected. Heavy smokers (OR=1.7) and heavy drinkers infected with HSV-1 (OR=4.2) or HSV-2 (smokers: OR=1.6; drinkers: OR=3.2) had lower odds compared to seronegative HSV-1 heavy users (smokers: OR=2.5; drinkers: OR=5.5) or HSV-2 (smokers: OR=1.9; drinkers: OR=6.2). Those seropositive to HPV-16 E6 and/or E7 but not HSV-1 (OR=27.4) or HSV-2 (OR=18.0) had higher risk of HNC compared to those infected with HSV-1 (OR=16.7) or HSV-2 (not estimable). These findings suggest that seropositivity to HSV-1 and HSV-2, although not independent risk factors for HNC, may modify the risk of HNC associated with exposure to tobacco, alcohol, or HPV-HR.

Different risk factors in basaloid and common squamous head and neck cancer

OBJECTIVES/HYPOTHESIS

The prevalence of human papillomavirus (HPV), herpes simplex virus (HSV), cigarette smoking and alcohol abuse was compared between two histological subgroups of head and neck cancer.

STUDY DESIGN

Retrospective review.

METHODS

Paraffin-embedded, histologically confirmed surgical specimens from the oropharynx, hypopharynx and larynx, comprising 67 conventional squamous cell carcinomas (SCC) and 10 basaloid squamous cell carcinomas (BSCC), were analyzed for the presence of HPV and HSV DNA using polymerase chain reaction (PCR) techniques. The PCR products were verified by direct sequencing. Patient charts were reviewed for clinical data and risk factors.

RESULTS

Given an overall HPV DNA detection rate of 32.5%, a basaloid morphology of the carcinomas correlated significantly with occurrence of HPV DNA (P =.0001). An association could also be demonstrated between basaloid appearance and evidence of HSV DNA (single and combined with HPV DNA; P =.014 and 0.0429, respectively), even if this result based on a low overall HSV DNA detection rate (6.5%). Demonstration of viral DNA in the BSCC specimens was not related to tobacco or alcohol consumption. In contrast, cigarette smoking proved as significant characteristic of SCC (P =.0087). Alcohol abuse occurred also predominately in patients with SCC, but without statistical significance.

CONCLUSION

These results hint at differences in the etiology of two distinct histological entities of head and neck cancer. Further research in this field could complete these preliminary data and provide the background for specific preventive strategies.

[Prevalence of oral lichen planus and oral leukoplakia in 112 patients with oral squamous cell carcinoma]

OBJECTIVE

To study the association existing between precancerous conditions, like oral lichen planus and oral leukoplakia into 112 patients with oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

We applied a protocol to 112 patients with OSCC in the "Servicio de Estomatología del Hospital General Universitario de Valencia". We made two groups: 1. patients with precancerous lesions and oral carcinoma, 2. patients with OSCC and no precancerous lesions.

RESULTS

The average age was 61.4 years, 85 of them being men and 27 women. The tongue and floor of the mouth were the most common locations. 33.6% of the tumours presented stage TNM I, most of them being histologically well differentiated and the 55.8% were ulcerated. We found differences between two groups of the patients regarding alcohol and tobacco habits, location, size and clinical stage and histological differentiation of the malignant lesions.

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.

Establishment of a human polyclonal oral epithelial cell line

OBJECTIVE

To develop a human oral epithelial cell line to constitute a continuous source of cells readily available for human oral epithelial cell research.

STUDY DESIGN

Oral epithelial cells from a 30-week gestational, stillborn male fetus were grown in serum-free medium and transfected by lipid-mediation with the shuttle vector plasmid, pZ189, containing the T-antigen coding region and replication origin from the SV40 virus.

RESULTS

Resulting cultures produced foci of rapidly multiplying cells that failed to senesce, in contrast to controls. The transformed culture, designated GMSM-K, was polyclonal. The original culture possessed a normal human male karyotype, and the transformed line was largely hypotetraploid. Multiple clones, isolated from soft agar studies and low density plating, showed decreased doubling times. Electron microscopy and immunohistochemistry confirmed an epithelial phenotype. Cells did not generate tumors in nude mice.

CONCLUSION

Few human epithelial cell lines are available to investigators and most are tumor-derived. The nontumor-derived GMSM-K line has value as a resource for human oral epithelial cell research.

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.