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Human Papillomavirus Type 16 Infection and Squamous Cell Carcinoma of the Head and Neck in Never-Smokers

A Matched Pair Analysis¹

Departments of Head and Neck Surgery [K. R. D., A. K. E., E. M. S.], Epidemiology [K. R. D., C. J. E., Z. L., M. R. S., Q. W., E. M. S.], and Pathology [A. K. E.], The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030; The University of Texas Health Science Center—Houston Dental Branch, Houston, Texas 77225 [K. A-S., L. D.]; and Laboratory of Cellular Oncology, National Cancer Institute, NIH, Bethesda, Maryland 20892 [J. T. S.]

	ABSTRACT

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Purpose: Infection with human papillomavirus (HPV) type 16 has been suggested to be a risk factor for squamous cell carcinoma of the head and neck (SCCHN) and to be more commonly associated with SCCHN occurring in the oropharynx and in never-smokers. We hypothesized that HPV-16 exposure, as evidenced by seropositivity, is a risk factor for SCCHN and may be of particular importance in never-smokers.

Experimental Design: To test this hypothesis, we conducted a hospital-based case-control study of 120 patients with SCCHN (60 never-smokers and 60 matched smokers) and 120 cancer-free matched controls. We compared the presence of HPV-16 antibodies in ever-smoker and never-smoker patients matched on age (±5 years), sex, and tumor site. Each patient was also matched with a corresponding ever-smoker or never-smoker cancer-free control on age (±5 years) and sex. Serum was collected from study subjects and assayed for IgG reactivity to HPV-16 L1 virus-like particles by using an ELISA.

Results: Forty-nine of the 120 case subjects (40.8%) but only 11 (9.2%) of the control subjects tested positive for HPV-16 antibodies (adjusted odds ratio, 6.69; 95% confidence interval, 3.01–14.90). Among cases, HPV-16 seropositivity was more common in those with oropharyngeal cancer (41 of 70, 58.6%) and poorly differentiated tumors (25 of 43, 58.1%). HPV-16 seropositivity was associated with a significantly increased risk of oropharyngeal cancer (adjusted odds ratio, 59.53; 95% confidence interval, 5.71–620.20). Whereas HPV-16 seropositivity was more common in never-smokers with SCCHN than in ever-smokers (43.3% versus 38.3%, respectively), this difference was not statistically significant.

Conclusions: HPV-16 infection is associated with a significant increased risk for oropharyngeal cancer but not oral cavity cancer. Furthermore, HPV-16 infection does not appear to be more common in never-smokers than ever-smokers with SCCHN.

	INTRODUCTION

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Tobacco and alcohol are well-established risk factors for SCCHN,³ but SCCHN also develops in individuals who have never smoked. HPV-16 has been established as an etiological agent in cervical cancer (1, 2, 3, 4, 5, 6) , and more recently, several investigators have suggested that infection with HPV (especially the high-risk types HPV-16 and HPV-18) is a risk factor for SCCHN (7, 8, 9, 10) . Numerous studies using methods such as PCR, Southern blotting, and in situ hybridization have detected HPV DNA in the tumor tissue and sera of SCCHN patients (11 , 12) . However, because these studies did not include cancer-free controls, most of these studies were unable to estimate the risk of SCCHN attributable to HPV-16. Whereas some studies have assessed HPV-16 DNA positivity in the mucosa of cancer-free controls (13 , 14) , the absence of viral DNA in normal mucosa may not be an accurate indicator of past exposure (15 , 16) because HPV DNA can be cleared from normal mucosa (17) .

In 1994, an ELISA for detecting HPV-16 VLPs was developed (18) . VLP ELISAs have been validated as type-restricted measures of past and present infections (19) . Such serological assays may be better than HPV DNA detection for epidemiological studies in which cumulative exposure to specific HPV types is relevant. Serological assays are also not subject to sampling bias, unlike DNA-based assays involving biopsy material.

Recent investigations suggested that the association between cancer and HPV-16 infection may depend on the tumor site within the head and neck region, with oropharyngeal cancers having the highest rates of HPV-16 DNA and seropositivity [18.6–56.7% (12 , 20 , 21) ]. HPV-16 DNA-positive oropharyngeal tumors (but not other SCCHNs) may be less commonly associated with risk factors such as drinking and smoking than HPV-16-negative tumors are (12) .

The chief oncoproteins of HPV-16 are encoded by the genes E6 and E7. The E6 protein targets the tumor suppressor gene p53 for ubiquitination and degradation. In fact, degradation of p53 in HPV-positive cells is fully dependent on the presence of E6 (22) . The E7 oncoprotein is involved in suppression of pRb function. Reduced pRb expression is common in HPV-positive tonsillar cancers (23 , 24) . This leads to the hypothesis that there are two pathways by which head and neck carcinogenesis occurs: (a) HPV-16 inactivates p53 and pRb, leading to tumor formation; or (b) more commonly, SCCHN is induced by tobacco and alcohol. In theory, these two carcinogenic pathways could occur in isolation or in conjunction. We hypothesized that HPV-16 infection, as evidenced by seropositivity, is a risk factor for SCCHN and for oropharyngeal cancer in particular and may be of particular importance in SCCHN occurring in never-smokers. We tested this hypothesis in a matched-pair case-control study of both smokers and never-smokers.

	MATERIALS AND METHODS

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Subjects.
Patients with histologically confirmed, previously untreated SCCHN (excluding cancers of the skin, sinonasal tract, nasopharynx, lip, or salivary glands) were recruited at our institution from May 1996 to January 2001. Cancer-free control subjects were selected from a pool of healthy controls identified during a similar time period from ongoing hospital-based case-control studies. The controls were clients of a local managed-care organization with multiple clinics throughout the Houston metropolitan area. The control subjects were first surveyed by means of a short questionnaire to determine their willingness to participate in research studies and to obtain information about their smoking behavior and demographic factors (25) . All participants agreed to donate 30 ml of blood and to complete a self-administered questionnaire that elicited information on age, sex, ethnicity, and tobacco and alcohol consumption. Approximately 95% of eligible cases and 75% of eligible controls agreed to participate. Ever-smokers were defined as those who had smoked more than 100 cigarettes in their lifetimes and ever drinkers were defined as those who had drunk alcoholic beverages at least once a week for more than 1 year. Each never-smoker case subject was matched on age (±5 years), sex, and tumor site with an ever-smoker case subject. Each case subject was also matched to a control subject on age, sex, and smoking status. All subjects were non-Hispanic whites.

HPV-16 Serological Testing.
VLPs generated from recombinant baculovirus-infected insect cells were used to test for antibodies against HPV-16 in the plasma of study subjects by using a standard ELISA, as described previously (18) . The cutoff level used was based on the absorbance value of a standard pooled serum known to be at the threshold of detection (26 , 27) . All samples were tested in duplicate. Any value above the cutoff value was considered positive, and any value below the cutoff was considered negative. The 38 samples that were within 15% of the cutoff point were tested twice more, and the 17 that were positive in all three assays were considered positive. We also retested a randomly chosen 10% of the samples and obtained 100% concordance on the repeat assays.

To eliminate potential binding interference by heparin, we treated the plasma samples with 43 units/ml heparinase I (Sigma, St. Louis, MO) before use (28) . We also obtained heparinized plasma as well as serum from three individuals. There was no discernable difference in the serological reactions between the serum samples and the heparinized plasma samples treated with heparinase (data not shown).

Cotinine Levels.
Cotinine is a chemical metabolite of tobacco smoke with a circulating half-life of at least 18 h after exposure to tobacco. We used anti-cotinine antibody-coated microtiter plates (STC Technologies, Inc., Bethlehem, PA) to measure the cotinine levels of all study subjects. The absorbances of known concentrations of cotinine were used as cutoff levels. There were very few subjects whose cotinine levels were intermediate (between 10 and 50 ng/ml), so the data were dichotomized. A subject was considered negative (no recent exposure) if his or her cotinine level was less than 25 ng/ml and positive (recent exposure) if it was greater than 25 ng/ml.

HPV-16 in Tumor Tissue.
DNA was extracted from the paraffin-embedded tumors samples of 34 of the case subjects. Tumor tissue was not available from the rest of the patients because it was archived at another institution or because only a cytologic aspirate was collected. The integrity of the DNA was determined by PCR amplification of the FAS gene. The DNA of 27 samples was intact and tested for the presence of HPV-16 viral DNA by using PCR with primers specific for E6 and E7, as described previously (29 , 30) .

Statistical Analyses.
² analyses were performed to determine the difference in the distribution of each demographic and exposure variable in cases and controls. Conditional logistic regressions were completed using LogXact 4 for Windows (Version 4.1; Cytel Software Corp., Cambridge, MA). ORs and their corresponding 95% CIs for HPV-16 seropositivity were calculated. For the case-control matched pairs, the ORs were calculated after adjusting for alcohol status and cotinine level and stratified by smoking. Exact conditional logistic regression was completed when data were highly unbalanced (risk for oropharyngeal cancer only). For the case-case matched pairs, the ORs were calculated after adjusting for alcohol status and cotinine level and stratified by cancer site. ² analyses were performed to determine the difference in the distribution of seropositivity prevalence within and between each tumor site and between tumor grades.

	RESULTS

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Table 1 demonstrates the matching variable distributions between cases and controls. One HPV-16-negative control subject was miscoded as a smoker before matching. The two groups were similar in their exposure history to alcohol (Table 1) . Their similar plasma cotinine levels showed that similar percentages of the case and control subjects had been recently exposed to tobacco (P = 0.191; Table 1 ).

	DISCUSSION

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This matched pair serological case-control study adds to the molecular epidemiological evidence suggesting that HPV-16 exposure is a risk factor for oropharyngeal cancer and explores the importance of HPV-16 in the never-smoker with SCCHN. In a nested case-control study of 292 cases and 1568 controls from a Scandinavian cohort of almost 900,000 subjects, Mork et al. (21) recently reported that HPV-16 seropositivity was associated with a 2.2-fold increased risk of SCCHN after adjustment for cotinine levels. However, 25% of the cases in that study were not classic SCCHN (3% were nasopharynx cancer, 20% were lip cancer, and 2% were sinus cancer). Because subjects with cancers of these sites were less frequently HPV-16 seropositive, Mork et al. (21) may have underestimated the risk of SCCHN associated with HPV-16 exposure. In addition, differences in the proportion of cases with oropharynx cancer may also account for the differences in risk estimates. In fact, in their subgroup analysis of oropharyngeal cancer, Mork et al. (21) reported an estimated risk of 14.4 (95% CI, 3.6–58.1). In a retrospective case-control study of 259 subjects with prevalent cancers of the oral cavity and oropharynx and 446 population-based controls, Schwartz et al. (31) found seropositivity to HPV-16 viral capsids associated with an adjusted risk of SCCHN of 2.3 (95% CI, 1.6–3.3). The highest risk estimates were associated with oropharyngeal cancers, and data suggested that HPV-16 seropositivity and current cigarette smoking were associated with a greater than additive increased risk for SCCHN. These landmark studies demonstrated the utility of HPV-16 serological screening and demonstrate that HPV-16 infection is a risk factor for oropharyngeal cancer.

Three additional case-control studies have been conducted using PCR to identify HPV-16 DNA in tumor tissue from SCCHN patients and head and neck mucosal tissue from cancer-free controls (13 , 14 , 32) . A study of oral cavity cancer (13) in which the HPV DNA in oral cavity was amplified and sequenced revealed that 15% of 93 oral cavity cancer cases and only 5% of 205 cancer-free controls were positive for HPV DNA (OR, 3.70; 95% CI, 1.47–9.32). A second study (14) found only a slight difference in high-risk HPV DNA types in 44 cases with laryngeal cancer, 10 cases with leukoplakia, and 12 cancer-free controls (18.2%, 20.0% and 16.7%, respectively). More recently, a retrospective case-control study of 52 patients with squamous cell carcinoma of the tonsil and 48 age- and sex-matched patients with benign tonsillar hyperplasia demonstrated a 18.2-fold risk of tonsillar carcinoma associated with the presence of HPV in tonsillar tissue (32) . Whereas these studies were relatively small, retrospective, unmatched, lacked smoking information, or did not include patients with oropharyngeal cancer, two of the three support the hypothesis that HPV-16 is a risk factor for SCCHN.

Our findings are also consistent with many case-series reports of HPV-16 DNA in the tumors of SCCHN patients. Past studies have also indicated that HPV-associated tumors are more likely to be in the oropharynx than in other parts of the head and neck (12 , 14 , 31) . In our study, 58.6% of the patients with oropharyngeal tumors were seropositive, compared with 8.3% and 35.7% of the patients with oral cavity and larynx cancer, respectively. This is in agreement with the previous results of both serological and tumor DNA studies reported by other investigators (11, 12, 13 , 21 , 32) . The subgroups within the oropharynx (the base of the tongue and the tonsil) did not differ significantly in HPV seropositivity. Furthermore, HPV-positive tumors are poorly differentiated and nonkeratinizing and have a basaloid morphology, which is more common in oropharyngeal tumors and is also consistent with our findings (12 , 23 , 33, 34, 35, 36) . Whereas the association between HPV seropositivity and poorly differentiated tumors may be restricted to tumors of the oropharynx, we are unable to confirm this due to a sample size of only four patients with poorly differentiated tumors of the oral cavity (one seropositive) and only a single patient (seronegative) with a poorly differentiated laryngeal cancer. We did find a high prevalence of seropositivity in the patients with supraglottic cancer, which was also consistent with previous reports (21 , 37) . Also, the 27 case subjects with HPV-16-positive tumors were three times more likely to be serologically positive than those with HPV-16-negative tumors. Although the number of cases was small, the correlation between serological data and tumor data is consistent with previous reports on head and neck (21) and gynecological cancer (18 , 38) .

Finally, we did not find that never-smokers with SCCHN were significantly more frequently HPV-16 seropositive than ever-smokers with SCCHN were. We did observe that almost 70% of oropharyngeal cancer patients who never smoked were serologically positive for HPV-16 and a higher risk of oropharyngeal cancer associated with HPV-16 seropositivity in the never-smokers than in the ever-smokers, but these differences were not statistically significant. Whereas our study included only 60 never-smokers with SCCHN, this is the largest number of never-smokers previously examined for HPV-16 status and is the first to systematically explore the role of HPV-16 in never-smokers with SCCHN. Other studies have also found that HPV is more common in SCCHN in never-smokers, but those studies had few never-smokers and no matching (particularly for tumor site) between ever-smokers and never-smokers. Fouret et al. (20) found that 5 of 10 SCCHNs (50%) in nonsmokers but only 15 of 177 SCCHNs (8.5%) in smokers had HPV DNA. Smith et al. (13) found that 7 of 18 oral and pharyngeal cancers (38.9%) in nonsmokers but only 7 of 75 oral and pharyngeal cancers (9.3%) in smokers were HPV positive. Strome et al. (32) found 6 of 7 (86%) tonsil cancers occurring in never-smokers to be HPV positive and 18 of 45 (40%) tonsil cancers in smokers to be HPV positive. Based on previous case-control studies and case series and the findings reported here, we conclude that HPV-16 is a clear risk factor for oropharyngeal cancer in ever-smokers and also a substantial risk factor for oropharyngeal cancers in never-smokers.

The literature and our findings together support many of the classic criteria for disease causality [including at least three of the five used by the Surgeon General in the official report linking smoking to lung cancer (39) ]. These criteria include the strength of the association (between HPV-16 and oropharyngeal cancer), the consistency in the literature (of HPV-16 DNAs being identified frequently in oropharyngeal cancers and associated with risk of oropharyngeal cancer in case-control studies), the specificity (of HPV-16 and not other HPV types), the consistency (of the cancer site associated with HPV-16), the coherence of the explanation and the analogy (of HPV-16-induced oropharyngeal cancer to cervical carcinogenesis), and the biological plausibility (of the HPV-16 carcinogenesis model). However, these studies could not demonstrate either a dose-response effect on risk or (with one exception) a clear temporal link between infection and tumor development. Consequently, a larger prospective cohort study is needed to verify the etiological role of HPV-16 in oropharyngeal cancer, to accurately quantify the risk of oropharyngeal cancer in those with serological evidence of HPV-16 exposure, and to explore the interaction between HPV-16 and degree of tobacco exposure. Ultimately, such studies may lead to improved cancer prevention by identifying individuals at high-risk of oropharyngeal cancer, who may benefit from aggressive smoking cessation efforts, screening for early detection, chemoprevention protocols, and possibly even prophylactic tonsillectomy.

	ACKNOWLEDGMENTS

 
We thank Margaret Lung for assistance with recruiting patients, Dr. Maureen Goode for scientific editing, and Deanna Thomas for manuscript preparation.

	FOOTNOTES

 
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Supported by Start-up Funds UT M. D. Anderson Cancer Center (E. M. S.), K-12 Ca88084 (R. C. B.), and P-30 Ca16672 (J. M.). Presented at the 93^rd Annual Meeting of the American Association for Cancer Research, April 6–10, 2002, San Francisco, California.

² To whom requests for reprints should be addressed, at Department of Head and Neck Surgery, Unit 441, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030-4009. Phone: (713) 792-5432; Fax: (713) 794-4662; E-mail: esturgis{at}mail.mdanderson.org

³ The abbreviations used are: SCCHN, squamous cell carcinoma of the head and neck; HPV, human papillomavirus; VLP, virus-like particle; pRb, retinoblastoma protein; OR, odds ratio; CI, confidence interval.

Received 10/21/02; accepted 3/12/03.

	REFERENCES

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1. Munoz N. Human papillomavirus and cancer: the epidemiological evidence. J. Clin. Virol., 19: 1-5, 2000.[CrossRef][Medline]
2. Zur Hausen H. Papillomaviruses causing cancer: evasion for host-cell control in early events in carcinogenesis. J. Natl. Cancer Inst. (Bethesda), 92: 690-698, 2000.[Abstract/Free Full Text]
3. Schiffmann M. H., Bauer H. M., Hoover R. N., Glass A. G., Cadell D. M., Rush B. B., Scott D. R., Sherman M. E., Kurman R. J., Wacholder S. Epidemiologic evidence showing that human papillomavirus infection causes most cervical intraepithelial neoplasia. J. Natl. Cancer Inst. (Bethesda), 85: 958-964, 1993.[Abstract/Free Full Text]
4. zur Hausen H. Human papillomaviruses in the pathogenesis of anogenital cancer. Virology, 184: 9-13, 1991.[Medline]
5. Lorincz A. T., Reid R., Jenson A. B., Greenberg M. D., Lancaster W., Kurman R. J. Human papillomavirus infection of the cervix: relative risk associations of 15 common anogenital types. Obstet. Gynecol., 79: 328-337, 1992.[Medline]
6. Munoz N., Bosch F. X., de Sanjose S., Tafur L., Isarzugaza I., Gili M., Viladiu P., Navarro C., Martos C., Ascunce N. The causal link between human papillomavirus and invasive cervical cancer: a population-based case-control study in Columbia and Spain. Int. J. Cancer, 52: 743-749, 1992.[Medline]
7. McKaig R. G., Baric R. S., Olshan A. F. Human papillomavirus and head and neck cancer: epidemiology and molecular biology. Head Neck, 20: 250-265, 1998.[CrossRef][Medline]
8. Mineta H., Ogino T., Amano H. M., Ohkawa Y., Araki K., Takebayashi S., Miura K. Human papillomavirus (HPV) type 16 and 18 detected in head and neck squamous cell carcinoma. Anticancer Res., 18: 4765-4768, 1998.[Medline]
9. Steinberg B. M., DiLorenzo T. P. A possible role for human papillomaviruses in head and neck cancer. Cancer Metastasis Rev., 15: 91-112, 1996.[CrossRef][Medline]
10. Snijders P., Cromme F. V., van den Brule A., Schrijnemakers H. F., Snow G. B., Meijer C. J., Walboomers J. M. Prevalence and expression of human papillomavirus in tonsillar carcinomas, indicating a possible viral etiology. Int. J. Cancer, 51: 845-850, 1992.[Medline]
11. Capone R. B., Pai S. I., Koch W. M., Gillison M. L., Danish H. N., Westra W. H., Daniel R., Shah K. V., Sidransky D. Detection and quantitation of human papillomavirus (HPV) DNA in the sera of patients with HPV-associated head and neck squamous cell carcinoma. Clin. Cancer Res., 6: 4171-4175, 2000.[Abstract/Free Full Text]
12. Gillison M. L., Koch W. M., Capone R. B., Spafford M., Westra W. H., Wu L., Zahurak M. L., Daniel R. W., Viglione M., Symer D. E., Shah K. V., Sidransky D. Evidence for a causal association between human papillomavirus and a subset of head and neck cancer. J. Natl. Cancer Inst. (Bethesda), 92: 709-720, 2000.[Abstract/Free Full Text]
13. Smith E. M., Hoffman H. T., Summersgill K. S., Kirchner H. L., Lubomir P. T., Haugen T. H. Human papillomavirus and risk of oral cancer. Laryngoscope, 108: 1098-1103, 1998.[CrossRef][Medline]
14. Smith E. M., Summersgill K. F., Allen J., Hoffman H. T., McCulloch T., Turek L. P., Haugen T. H. Human papillomavirus and risk of laryngeal cancer. Ann. Otol. Rhinol. Laryngol., 109: 1069-1076, 2000.[Medline]
15. Nonnenmacher B., Hubbert N., Kirnbauer R., Shah K. V., Munoz N., Bosch F. X., de Sanjose S., Viscidi R., Lowy D. R., Schiller J. T. Serological response to human papillomavirus type 16 (HPV-16) virus-like particles in HPV-16 DNA-positive invasive cervical cancer and cervical intraepithelial neoplasia grade III patients and controls from Columbia and Spain. J. Infect. Dis., 172: 19-24, 1995.[Medline]
16. Nonnenmacher B., Kruger Kjaer S., Svare E. I., Scott J. D., Hubbert N. L., van den Brule A. J., Kirnbauer R., Walboomers J. M., Lowy D. R., Schiller J. T. Seroreactivity to HPV-16 virus-like particles as markers for cervical cancer in high risk areas. Int. J. Cancer, 68: 704-709, 1996.[CrossRef][Medline]
17. Evander M., Edlund K., Gustafsson A., Jonsson M., Karlsson R., Rylander E., Wadell G. Human papillomavirus infection is transient in young women: a population-based cohort study. J. Infect. Dis., 171: 1026-1030, 1995.[Medline]
18. Kirnbauer R., Hubbert N. L., Wheeler C. M., Becker T. M., Lowy D. R., Schiller J. T. A virus-like particle enzyme-linked immunosorbent assay detects serum antibodies in a majority of women infected with human papillomavirus type 16. J. Natl. Cancer Inst. (Bethesda), 86: 494-499, 1994.[Abstract/Free Full Text]
19. Dillner J. The serological response to papillomaviruses. Cancer Biol., 9: 423-430, 1999.
20. Fouret P., Monceaux G., Temam S., Lacourreye L., St Guily J. L. Human papillomavirus in head and neck squamous cell carcinomas in nonsmokers. Arch. Otolaryngol. Head Neck Surg., 123: 513-516, 1997.[Abstract]
21. Mork J., Lie K., Glattre E., Hallmans G., Jellum E., Koskela P., Moller B., Pukkala E., Schiller J. T., Youngman L., Lehtinen M., Dillner J. Human papillomavirus infection as a risk factor for squamous cell carcinoma of the head and neck. N. Engl. J. Med., 344: 1125-1131, 2001.[Abstract/Free Full Text]
22. Hengstermann A., Linares L. K., Ciechanover A., Whitaker N. J., Scheffner M. Complete switch from Mdm2 to human papillomavirus E6-mediated degradation of p53 in cervical cancer cells. Proc. Natl. Acad. Sci. USA, 98: 1218-1223, 2001.[Abstract/Free Full Text]
23. Andl T., Kahn T., Pfuhl A., Nicola T., Erber R., Conradt C., Klein W., Helbig M., Dietz A., Weidauer H., Bosch F. X. Etiological involvement of oncogenic human papillomavirus in tonsillar squamous cell carcinomas lacking retinoblastoma cell cycle control. Cancer Res., 58: 5-13, 1998.[Abstract/Free Full Text]
24. Munger K., Werness B. A., Dyson N., Phelps W., Harlow E., Howley P. Complex formation of human papillomavirus E7 proteins with the retinoblastoma tumor suppressor gene product. EMBO J., 8: 4099-4105, 1989.[Medline]
25. Hudmon K. S., Honn S. E., Jiang H., Chamberlain R. M., Xiang W., Ferry G., Gosbee W., Spitz M. R. Identifying and recruiting healthy control subjects from a managed care organization: a methodology for molecular epidemiologic case-control studies of cancer. Cancer Epidemiol. Biomark. Prev., 6: 565-571, 1997.[Abstract]
26. Han C. L., Qiao G., Hubbert N. L., Li L., Sun C., Wang Y., Yan M., Li Y., Lowy D. R., Schiller J. T. Serological association between human papillomavirus type 16 infection and esophageal cancer in Shaanxi Province, China. J. Natl. Cancer Inst. (Bethesda), 88: 1467-1471, 1996.[Abstract/Free Full Text]
27. Svare E. I., Kruger-Kjaer S., Nonnenmacher B., Worm A. M., Moi H., Christensen R. B., van den Brule A., Walboomer J., Meijer C., Hubbert N. L., Lowy D. R., Schiller J. T. Seroreactivity to human papillomavirus type 16 virus-like particles is lower in high-risk men than in high-risk women. J. Infect. Dis., 176: 876-883, 1997.[Medline]
28. Alcantara F. F., Iglehart D. J., Ochs R. L. Heparin in plasma samples causes nonspecific binding to histones on Western blots. J. Immunol. Methods, 226: 11-18, 1999.[CrossRef][Medline]
29. Samoylova E. V., Shaikhaiev G. O., Petrov S. V., Kisseljova N. P., Kisseljov F. L. HPV infection in cervical-cancer cases in Russia. Int. J. Cancer, 61: 337-341, 1995.[Medline]
30. Walboomers J. M., Jacobs M. V., Manos M. M., Bosch F. X., Kummer J. A., Shah K. V., Snijders P. J., Peto J., Meijer C. J., Munoz N. Human papillomavirus is a necessary cause of invasive cervical cancer worldwide. J. Pathol., 189: 12-19, 1999.[CrossRef][Medline]
31. Schwartz S. M., Daling J. R., Doody D. R., Wipf G. C., Carter J. J., Madeleine M. M., Mao E. J., Fitzgibbons E. D., Huang S., Beckmann A. M., McDougall J. K., Galloway D. A. Oral cancer risk in relation to sexual history and evidence of human papillomavirus infection. J. Natl. Cancer Inst. (Bethesda), 90: 1626-1636, 1998.[Abstract/Free Full Text]
32. Strome S. E., Savva A., Brissett A. E., Gostout B. S., Lewis J., Clayton A. C., McGovern R., Weaver A. L., Persing D., Kasperbauer J. L. Squamous cell carcinoma of the tonsils: a molecular analysis of HPV associations. Clin. Cancer Res., 8: 1093-1100, 2002.[Abstract/Free Full Text]
33. Wilczynski S. P., Lin B. T., Xie Y., Paz I. B. Detection of human papillomavirus DNA and oncoprotein overexpression are associated with distinct morphological patterns of tonsillar squamous cell carcinoma. Am. J. Pathol., 152: 145-156, 1998.[Abstract]
34. Banks E. R., Frierson H. F., Jr., Mills S. E., George E., Zarbo R. J., Swanson P. E. Basaloid squamous cell carcinoma of the head and neck. A clinicopathologic and immunohistochemical study of 40 cases. Am. J. Surg. Pathol., 16: 936-946, 1992.
35. Raslan W. F., Barnes L., Krause J. R., Contis L., Killeen R., Kapadia S. B. Basaloid squamous cell carcinoma of the head and neck: a clinicopathologic and flow cytometric study of 10 new cases with review of the English literature. Am. J. Otolaryngol., 15: 204-211, 1994.[CrossRef][Medline]
36. Barnes L., Ferlito A., Altavilla G., MacMillan C., Rinaldo A., Doglioni C. Basaloid squamous cell carcinoma of the head and neck: clinicopathological features and differential diagnosis. Ann. Otol. Rhinol. Laryngol., 105: 75-82, 1996.[Medline]
37. Clayman G. L., Stewart M. G., Weber R. S., El-Naggar A. K., Brimm E. A. Human papillomavirus in laryngeal and hypopharyngeal carcinomas. Relationship to survival. Arch. Otolaryngol. Head Neck Surg., 120: 743-748, 1994.[Abstract]
38. Elfgren K., Bistoletti P., Dillner L., Walboomers J. M., Meijer C. J., Dillner J. Conization for cervical intraepithelial neoplasia is followed by disappearance of human papillomavirus deoxyribonucleic acid and a decline in serum and cervical mucus antibodies against human papillomavirus antigens. Am. J. Obstet. Gynecol., 174: 937-942, 1996.[CrossRef][Medline]
39. . Smoking and Health. Report of the Advisory Committee to the Surgeon General of the Public Health Service, United States Department of Health, Education, and Welfare Washington, DC 1964.

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				B Perez-Ordonez, M Beauchemin, and R C K Jordan Molecular biology of squamous cell carcinoma of the head and neck. J. Clin. Pathol., May 1, 2006; 59(5): 445 - 453. [Abstract] [Full Text] [PDF]

				G. Li, Z. Liu, E. M. Sturgis, Q. Shi, R. M. Chamberlain, M. R. Spitz, and Q. Wei Genetic polymorphisms of p21 are associated with risk of squamous cell carcinoma of the head and neck Carcinogenesis, September 1, 2005; 26(9): 1596 - 1602. [Abstract] [Full Text] [PDF]

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				K. B. Pytynia, J. R. Grant, C. J. Etzel, D. B. Roberts, Q. Wei, and E. M. Sturgis Matched-Pair Analysis of Survival of Never Smokers and Ever Smokers With Squamous Cell Carcinoma of the Head and Neck J. Clin. Oncol., October 1, 2004; 22(19): 3981 - 3988. [Abstract] [Full Text] [PDF]

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				G. Li, E. M. Sturgis, L.-E. Wang, R. M. Chamberlain, M. R. Spitz, A. K. El-Naggar, W. K. Hong, and Q. Wei Association between the V109G Polymorphism of the p27 Gene and the Risk and Progression of Oral Squamous Cell Carcinoma Clin. Cancer Res., June 15, 2004; 10(12): 3996 - 4002. [Abstract] [Full Text] [PDF]

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