The influence of monoamine oxidase variants on the risk of betel quid-associated oral and pharyngeal cancer.

Betel quid (BQ) and areca nut (AN) (major BQ ingredient) are group I human carcinogens illustrated by International Agency for Research on Cancer and are closely associated with an elevated risk of oral potentially malignant disorders (OPMDs) and cancers of the oral cavity and pharynx. The primary alkaloid of AN, arecoline, can be metabolized via the monoamine oxidase (MAO) gene by inducing reactive oxygen species (ROS). The aim of this study was to investigate whether the variants of the susceptible candidate MAO genes are associated with OPMDs and oral and pharyngeal cancer. A significant trend of MAO-A mRNA expression was found in in vitro studies. Using paired human tissues, we confirmed the significantly decreased expression of MAO-A and MAO-B in cancerous tissues when compared with adjacent noncancerous tissues. Moreover, we determined that MAO-A single nucleotide polymorphism variants are significantly linked with oral and pharyngeal cancer patients in comparison to OPMDs patients [rs5953210 risk G-allele, odds ratio = 1.76; 95% confidence interval = 1.02-3.01]. In conclusion, we suggested that susceptible MAO family variants associated with oral and pharyngeal cancer may be implicated in the modulation of MAO gene activity associated with ROS.

Lymphangioma of the palatine tonsil.

Lymphangioma of the palatine tonsil is a rare, benign lesion that presents as a tonsillar outgrowth and causes symptoms related to irritation and airway obstruction. Histologically, the mass has abundant dilated lymphatic channels amid a fibrous stroma with lymphoid and adipose elements. There are several theories regarding the pathogenesis of these lesions, and the appropriate diagnostic classification is controversial. Because a lymphangioma may resemble a true neoplasm of the palatine tonsil clinically, the lesion must be removed for accurate histologic diagnosis and to rule out malignancy. Lymphangioma of the palatine tonsil is treated with surgical excision and has no recurrence once completely resected.

Increase of phosphatase and tensin homolog by silymarin to inhibit human pharynx squamous cancer.

Silymarin is an active principle from the seeds of the milk thistle plant and is widely used as a hepatoprotective gent due to its antioxidant-like activity. In the present study, we evaluated the potential efficacy of silymarin against oral cancer and investigated its possible mechanism of action. Cell viability assay and western blotting analyses were used to identify silymarin-induced apoptotic cell death in human pharynx squamous cell carcinoma (FaDu) cells. The short interfering RNA (siRNA) is used to confirm the role of phosphatase and tensin homolog (PTEN) in silymarin-induced apoptosis. Treatment of FaDu cells with silymarin resulted in a significant decrease in cell viability (up to 70%). Silymarin inhibited the phosphorylation of Akt (over 10-fold) with an increase in expression of PTEN (five to sixfold). Consequently, the level of Bcl-2 expression was decreased five to sixfold and caspase 3 activated to induce apoptosis. Treatment with siRNA specific to PTEN gene diminished the action of silymarin. The results suggest that silymarin inhibits the Akt signaling pathway by increasing PTEN expression in FaDu cells and directly affects Bcl-2 family members. Also, we demonstrated the inhibitory activity of silymarin for oral cancer is related to cell survival. These mechanisms may in part explain the actions of silymarin and provide a rationale for the development of silymarin as an anticancer agent.

Genetic polymorphisms in the tobacco smoke carcinogens detoxifying enzyme UGT1A7 and the risk of head and neck cancer.

BACKGROUND: UGT1A7 is an enzyme involved in the metabolism of (pre)carcinogens present in tobacco smoke. We investigated whether genetic polymorphisms in UGT1A7, with predicted altered enzyme activity, may have a risk-modifying effect on head and neck carcinogenesis. METHODS: Blood samples from 427 patients with oral, pharyngeal, and laryngeal carcinoma and 420 healthy control subjects were investigated for UGT1A7 polymorphisms. Based on these polymorphisms, patients and controls were divided according to predicted enzyme activity (low, intermediate, high). RESULTS: Logistic regression analysis showed a significant increased distribution of predicted high activity UGT1A7 polymorphisms among the patients (OR:1.44; 95% CI: 1.07-1.93). Stratified analyses demonstrated that high activity UGT1A7 polymorphisms were even more significantly present in patients with laryngeal cancer, older patients, heavy smokers, and heavy drinkers when compared with the control subjects. CONCLUSIONS: Predicted high activity UGT1A7 polymorphisms were significantly associated with an increased risk of head and neck cancer.

Absence of activating mutations in the EGFR kinase domain in Spanish head and neck cancer patients.

The discovery of kinase domain mutations in the epidermal growth factor receptor gene (EGFR) in never-smoker patients, associated with an increased sensitivity to tyrosine kinase inhibitors (TKIs) such as gefitinib or erlotinib, has been one of the most relevant findings ever in non-small cell lung carcinomas (NSCLC). Since treatment with TKIs has furthermore shown a clinical benefit in head and neck squamous cell carcinoma (HNSCC) patients, we hypothesized that these mutations could also be present in this neoplasia. Current studies looking for EGFR mutations in HNSCC are limited and results are still controversial. In this work, we screened for EGFR tyrosine kinase mutations in tumour DNA obtained from 31 Spanish patients with HNSCC by PCR-single-strand conformational polymorphism analysis. None of the patients displayed a somatic EGFR mutation, previously described in NSCLC, but other DNA sequence variations were found in 9 of 31 HNSCC patients. Accordingly, activating EGFR mutations in HNSCC patients seem to be a rare event in Spanish patients, suggesting that there is little room for the administration of TKIs in HNSCC based on the presence of these mutations. Additional investigations about EGFR amplification are indicated to establish a potential relationship between EGFR overexpression and the response to anti-EGFR therapies.

Frequent high telomerase reverse transcriptase expression in primary oral squamous cell carcinoma.

BACKGROUND: Gene copy number gain of chromosomal arm 5p is frequently found in oral squamous cell carcinoma (OSCC) suggesting the activation of proto-oncogenes. TERT is a candidate gene encoding for human telomerase reverse transcriptase (hTERT). The aim of the present study was to elucidate the relevance of TERT copy number gain and high hTERT expression in OSCC. METHODS: Fluorescence in situ hybridization (FISH) for TERT and immunohistochemistry (IHC) for hTERT were performed to analyze TERT copy numbers and hTERT expression, respectively, on tissue microarray (TMA) sections including n = 247 OSCC and n = 105 pharyngeal and laryngeal squamous cell carcinomas (PSCC/LSCC). RESULTS: Increased hTERT protein expression was more frequently found in OSCC (71.1%, 155/218) than in PSCC/LSCC (36.0%, 35/89) (P < 0.001). By contrast, specific TERT amplifications were less common in OSCC (2.1%, 4/191) compared with PSCC/LSCC (9.9%, 8/81) (P = 0.047). CONCLUSIONS: High hTERT expression is a frequent finding in OSCC. It might be a promising target for the development of specific anti-neoplastic therapy approaches.

Association between high collagenase-3 expression levels and poor prognosis in patients with head and neck cancer.

BACKGROUND: Squamous cell carcinoma of the head and neck (HNSCC) is a common cancer type. The ability for curative treatment with surgery and radiotherapy (RT) is usually highly dependent on tumor stage at the time of diagnosis. METHODS: The purpose of this study was to determine whether the expression of a cancer-specific proteinase, collagenase-3 (matrix metalloproteinase-13 [MMP-13]), is associated with survival parameters in patients with HNSCC. We studied MMP-13 expression in tumors of 81 patients with stage I-IV HNSCC treated with surgery alone or in combination with radiotherapy. RESULTS: We found a subgroup of patients with high MMP-13 expression level in their tumors (>/=90% MMP-13-positive tumor cells) associated with unfavorable prognosis (median overall survival [OS], 11.8 vs 19.6 months, p = .032). In addition, the median disease-specific survival (DSS) time was markedly reduced in this subgroup (13.8 months vs 40.7 months, p = .062). When the subgroup of patients treated with a curative intent was studied, the same association was found in OS (13.8 vs 24.6 months, p = .023) and DSS (p = .004). In addition, there was a trend for association between >/=90% MMP-13 positivity and a recurrent tumor (p = .078) in curatively treated patients. CONCLUSIONS: The short survival time associated with high MMP-13 expression levels could not be predicted by tumor size or local lymph node invasion. These results show that a high MMP-13 expression level is associated with aggressiveness of HNSCC and may have prognostic value in patient evaluation.

A quantitative RT-PCR method to determine topoisomerase I mRNA levels in human tissue samples.

DNA topoisomerase I (Topo I) is involved in DNA replication, transcription, recombination and repair. Clinical interest has focused on Topo I as it is the molecular target of camptothecin (CPT), used in first and second lines of treatment for different cancer types. Furthermore, it is well demonstrated that the patients who best responded to CPT-based chemotherapy were generally those with the greatest tumoral Topo I expression and/or activity. We developed a sensitive, simple and reproducible method to measure Topo I mRNA expression in human cancer samples. Experiments were performed in two steps. First, we checked the accuracy of the reverse transcription-polymerase chain reaction (RT-PCR) method by testing intra- and interassay reproducibility of Topo I and G6PDH gene amplification in different cell types. We observed that crossing-points (Cps) were different, depending on the cell type, dilution or cDNA concentration, but that the intra- and interassay Cp standard deviation (SD) never exceeded 0.77% and 1.39% for Topo I amplification, or 1.63% and 2.9% for G6PDH amplification, respectively. Secondly, we used our method to measure Topo I mRNA levels in primary tumor samples obtained from 27 patients with advanced colorectal cancer and 10 patients with pharyngeal/laryngeal cancer. The accuracy of G6PDH as a housekeeping gene was tested by analyzing its correlation with the mRNA level of a second housekeeping gene, porphobilinogen deaminase (PBG-D) in the tumoral samples. We found that the normalized Topo I/G6PDH mRNA ratios were significantly correlated with that of Topo I/PBGD in colorectal tumors (r(2)=0.47, p=0.02) but not in pharyngeal/laryngeal tumors (r(2)=0.35, p=0.3). Neither ratio showed any significant association with clinicopathological parameters, such as gender, age, tumor size, or grade and lymph node status. We believe that RT-PCR is a reliable and highly reproducible technique. However, the choice of the reference gene is an important point and must be defined based on the samples studied.

Association between methylenetetrahydrofolate reductase polymorphisms, alcohol intake and oropharyngolaryngeal carcinoma in northern Italy.

Folate metabolism dysregulation may lead to abnormal cell proliferation and predispose to carcinogenesis by inducing DNA hypomethylation. Folate pathways may be modified by polymorphisms in relevant genes, such as that for methylenetetrahydrofolate reductase (MTHFR), or by alcohol consumption. We investigated the relationship between MTHFR mutations at nucleotides C677T and A1298C, which cause reduced MTHFR enzyme activity, and susceptibility to oropharyngolaryngeal carcinoma in 65 patients and 100 controls. We isolated DNA from peripheral blood leukocytes. In oropharyngolaryngeal carcinoma cases the C677T heterozygous genotype was more frequent (p = 0.018), the allele frequency of MTHFR 677T was greater (p = 0.019) and the genotype 677TT/1298AA was more frequent (p = 0.001). A higher risk of carcinoma was found in the case of moderate drinkers with mutant MTHFR homozygosis or double heterozygosis (OR = 21.2 and OR = 9.1, respectively; p trend = 0.002), and the association was maintained for the different cancer sites (glottic, supraglottic, oropharyngeal). Our findings support the hypothesis that the interaction of alcohol intake and MTHFR polymorphisms might contribute to susceptibility to carcinogenesis of the oropharyngolaryngeal tract.

Acoustic stimulation promotes the expression of inducible nitric oxide synthase in the vestibule of guinea pigs.

Loud acoustic stimulation is known to cause inner ear disturbance. We examined immunohistochemically the vestibule of 12 guinea pigs after acoustic stimulation. The animals were divided into two equal groups: a control group and an acoustic stimulation group. The temporal bones were fixed by means of a cardiac infusion of fixative and immunohistochemically stained for inducible nitric oxide synthase (iNOS). The temporal bones in the control group did not show any iNOS. In the acoustic stimulation group, immunoreactivity for iNOS was detected in the supporting cells and sensory cells of the sensory epithelium, in the dark cell areas and in the vestibular ganglion cells. These findings suggest that free radicals are involved in the pathogenesis of noise-induced inner ear damage. Furthermore, free radicals may cause vestibular damage, as is seen in noise-induced inner ear damage.

Differential expression pattern of cyclooxygenase-1 and -2 in head and neck squamous cell carcinoma.

OBJECTIVE: The enzyme cyclooxygenase catalyzes the first step of the synthesis of prostanoids Cyclooxygenase has been shown to exist in two distinct isoforms: cyclooxygenase-1 is constitutively expressed as a housekeeping enzyme in most tissues whereas the inducible cyclooxygenase-2 has been reported to be involved in inflammatory processes and in the carcinogenesis of squamous cell carcinoma. The aim of this study was to investigate the distribution patterns of cyclooxygenase-1 and -2 in peritumoral lymphocytic infiltrates and tumor cells of head and neck carcinoma. MATERIAL AND METHODS: Immunohistochemical analysis was performed using paraffin-embedded tumor specimens from 24 patients suffering from oropharyngeal, hypopharyngeal and oral squamous cell carcinomas. RESULTS: We observed that cyclooxygenase-2 immunoreactivity, compared to that of cyclooxygenase-1, was significantly increased in peritumoral lymphocytic infiltrates as well as in tumor cells. CONCLUSION: The expression of cyclooxygenase-2 in both tumor specimens and the surrounding peritumoral lymphocytic infiltrates supports the hypothesis that cyclooxygenase may be one of several important links between chronic inflammation and carcinogenesis.

Simultaneous targeting of telomeres and telomerase as a cancer therapeutic approach.

Telomeres, which are important for maintaining chromosome integrity and functions, shorten with each cell division. Telomerase, responsible for telomere synthesis, is expressed in approximately 90% of human tumor cells but seldom in normal somatic cells. This study evaluated the hypothesis that simultaneous shortening of telomeres and inhibition of telomerase results in synergistic and tumor-selective cytotoxicity. In telomerase-positive human pharynx FaDu tumor cells, paclitaxel caused telomere erosion (first detected at 1 h) and apoptosis. Expression of antisense to the RNA component of human telomerase (hTR) inhibited telomerase activity, shortened telomere length, reduced cell growth rate, and resulted in a significant higher sensitivity to paclitaxel. Another telomerase inhibitor, 3'-azido-3'-deoxythymidine (AZT), at a concentration that produced little or no cell detachment or apoptosis, inhibited the telomerase activity and enhanced the paclitaxel-induced cell detachment and apoptosis. AZT also enhanced the activity of paclitaxel in mice bearing well-established s.c. FaDu xenograft tumors (i.e., reduced residual tumor size, enhanced apoptotic cell fraction, and prolonged survival time), without enhancing host toxicity. In contrast, AZT did not enhance the paclitaxel activity in the telomerase-negative osteosarcoma Saos-2 cells nor in FaDu cells where telomerase was already suppressed by antisense hTR, confirming that the AZT effect in parent FaDu cells is mediated through telomerase inhibition. These results demonstrate that combined use of agents targeting both telomere and telomerase yielded synergistic activity selective for tumors that depend on telomerase for telomere maintenance.

Inducible nitric oxide synthase expression in pharyngeal squamous cell carcinoma: relation to p53 expression, clinicopathological data, and survival.

OBJECTIVE: To investigate the expression of inducible nitric oxide synthase (iNOS) in oropharyngeal and hypopharyngeal squamous cell carcinoma (SCC) and its relation to p53 expression, histologic differentiation, clinical data, and prognosis. STUDY DESIGN: A retrospective survey. METHODS: Primary tumors for analyses were obtained from 118 patients diagnosed with SCC of the oropharynx or hypopharynx between 1975 and 1998 in eastern Finland. Immunohistochemical analysis was used to evaluate the expression of iNOS and p53. The expression pattern of iNOS was related to p53 expression, clinical data, and survival. RESULTS: High iNOS score was associated significantly with high nuclear p53 expression index (P = .006) and positive cytoplasmic p53 expression (P = .025). The score for iNOS expression was significantly lower in the largest (T4) tumors (P = .043). No association was seen between iNOS score and N or M class, tumor stage, or histologic differentiation. The score for iNOS expression was not related to overall survival. CONCLUSIONS: The expressions of iNOS and p53 seem to be inter-related in pharyngeal SCC, although the causality remains to be clarified. The expression of iNOS shows no prognostic value in pharyngeal SCC.

Overexpression of cyclo-oxygenase 2 in squamous cell carcinoma of the hypopharynx.

Upregulation of cyclo-oxygenase 2 (COX-2) expression is frequently found in a variety of human cancers. In this study, we examined COX-2 expression in squamous cell carcinoma of the hypopharynx. COX-2 messenger RNA (mRNA) analyzed by reverse-transcription polymerase chain reaction was detected in 87% (20 of 23) of tumor tissues. Expression of COX-2 protein was examined by Western blot analysis. COX-2 protein levels were increased in tumor tissues and correlated with the expression level of mRNA. Immunohistochemical study was performed to detect the subcellular localization of COX-2. Our results showed that COX-2 was predominantly detected in cancer cells, and the staining pattern was cytoplasmic. Several histologically normal adjacent tissues obtained from these patients were also investigated. We found that COX-2 mRNA was detectable in these tissues. However, COX-2 mRNA and protein levels were lower in these tissues than in tumor specimens. In contrast, COX-2 mRNA and protein levels in normal oral mucosa obtained from healthy volunteers were very low or undetectable. The frequency of COX-2 overexpression was significantly higher in the N1-N3 group than in the N0 group. These results suggest that overexpression of COX-2 is linked with increased lymphatic invasion in hypopharyngeal carcinoma. Collectively, these results suggest that overexpression of COX-2 is a frequent phenomenon in hypopharyngeal carcinoma and may play a role in tumorigenesis of this cancer.

Alcohol dehydrogenase 3 genotype is not associated with risk of squamous cell carcinoma of the oral cavity and pharynx.

Alcohol is one of the major risk factors for oral and pharyngeal cancer. The rate-limiting step in alcohol metabolism is the oxidation (activation) of ethanol to acetaldehyde by the alcohol dehydrogenases (ADHs). It has been hypothesized that individuals who are homozygous for the fast allele (ADH(1-1)(3)) are at greater risk for alcohol-related cancers. To test this hypothesis, we investigated the association between the ADH3 genotype and oral and pharyngeal cancer risk in a large racially homogeneous case-control study of 229 patients and 575 matched control subjects with frequency matching on age, sex, and smoking status. Although the smoking status was matched between cases and controls, current and former alcohol use remained a significant risk factor, compared with never use (odds ratio, 2.08; 95% confidence interval, 1.37-3.17; odds ratio, 1.97; 95% confidence interval, 1.25-3.09; and odds ratio, 1.00, respectively). The ADH1(3) allele frequency of controls was 57.4%, consistent with reports of similar racial groups (50-60%). The genotype distribution in controls was also consistent with the Hardy-Weinberg equilibrium (P = 0.51). However, the ADH1(3) allele frequency and ADH(1-1)(3) genotype frequency were not significantly different between cases and controls [55.5% versus 57.4% (P = 0.52), and 30.6% versus 31.3% (P = 0.91), respectively]. There was no association between ADH3 genotypes (ADH(1-1)(3), ADH(1-2)(3), and ADH(2-2)(3)) and risk of oral and pharyngeal cancer (odds ratios, 1.00; 0.96; 95% confidence interval, 0.68-1.37; and odds ratio, 1.23; confidence interval, 0.78-1.93, respectively). Therefore, we found no evidence that supports a main effect of ADH3 genotype or a combined effect of alcohol and ADH3 genotype on risk of cancer of the oral cavity or pharynx.

Role of alcohol dehydrogenase 3 and cytochrome P-4502E1 genotypes in susceptibility to cancers of the upper aerodigestive tract.

Alcohol is a recognized risk factor for upper aerodigestive tract (UAT) cancers, but the mechanism by which alcohol causes cancer remains obscure. Ethanol is oxidized to acetaldehyde (the suspected carcinogenic agent in alcohol) by alcohol dehydrogenases (ADHs) and cytochrome P-4502E1 (CYP2E1), both of which exhibit great inter-individual variability in activity. The hypothesis that these polymorphisms influence susceptibility to alcohol-related cancers remains poorly documented. We investigated whether ADH(3) and CYP2E1 DraI and RsaI genotypes modified the risk of UAT cancers among 121 oral cavity/pharyngeal cancer patients, 129 laryngeal cancer patients, and 172 controls, all French Caucasians. Cancer risks and gene-alcohol interactions were analyzed by unconditional logistic regression, accounting for potential confounders. ADH(3) genotype was not associated with UAT cancer. In contrast, a 2-fold risk of oral cavity/pharyngeal (OR = 2.0, 95% CI 1.0-3.9) and laryngeal (OR = 1.8, 95% CI 1.0-3.5) cancers was observed for carriers of the CYP2E1 DraI C variant allele compared with other individuals. The risk associated with the CYP2E1 RsaI c2 variant allele also increased for oral cavity/pharyngeal cancer (OR = 2.6, 95% CI 1.0-6. 6). The effects of ADH(3) or CYP2E1 genotype and alcohol or tobacco were independent. The highest risk of oral cavity/pharyngeal cancer was observed among the heaviest drinkers (>80 g/day) with the CYP2E1 DraI C allele (OR = 5.8, 95% CI 1.9-18.2) or the CYP2E1 RsaI c2 allele (OR = 7.2, 95% CI 1.4-38.2) compared with lighter drinkers with other genotypes. Our study suggests that CYP2E1 genotype modifies the risk of UAT cancers, but due to the low frequency of CYP2E1 variant alleles, large-scale studies are needed to confirm our findings.

High-activity microsomal epoxide hydrolase genotypes and the risk of oral, pharynx, and larynx cancers.

Human microsomal epoxide hydrolase (mEH), encoded by the EPHX1 gene, is involved in the metabolism of tobacco carcinogens. We investigated the effect of exon 3 and 4 polymorphisms of the EPHX1 gene in 121 patients with cancers of the oral cavity/pharynx, 129 patients with cancer of the larynx, and 172 non-cancer controls, all Caucasian regular smokers. The potential modifying role of previously analyzed GSTM1, GSTM3, and GSTP1 genotypes was also examined. Compared with the putative low-activity genotypes, odds ratios (ORs) associated with predicted intermediate and high mEH activity genotypes were significantly increased for oropharyngeal cancers [OR = 1.8; 95% confidence interval (CI) = 1.0-3.3; and OR = 2.1; 95% CI = 1.0-4.5, respectively; P(trend) = 0.03] and laryngeal cancers (OR = 1.7; 95% CI = 1.0-3.1; and OR = 2.4; 95% CI = 1.1-5.1, respectively; P(trend) = 0.02). Moreover, a positive interaction was found between mEH activity and GSTM3 genotype for laryngeal cancer. The combined EPHX1 high activity-associated genotype and GSTM3 (AB or BB) genotype conferred a 13.1-fold risk (95% CI = 3.5-48.4) compared with the concurrent presence of the EPHX1 low activity-associated genotype and the GSTM3 AA genotype. Thus, EPHX1 polymorphisms may be one of the factors of importance in susceptibility to smoking-related cancers of the upper aerodigestive tract.

Substantially reduced risk of cancer of the aerodigestive tract in subjects with variant--463A of the myeloperoxidase gene.

Myeloperoxidase (MPO), an enzyme that is highly expressed in neutrophil leukocytes, transforms precarcinogens such as benzo(a)pyrene and aromatic amines to highly reactive intermediates. A G/A polymorphism located 463 bp upstream of exon 1 in the promoter region strongly reduces MPO mRNA expression. In a matched case-control study, 196 lung cancer, 245 laryngeal cancer, and 255 pharyngeal cancer patients from the Berlin area were investigated for frequency of the G-463A polymorphism by PCR/RFLP, using AciI. They were matched by age and gender to hospital patients without known malignancies. Moreover, 270 healthy volunteers were genotyped, obtaining 61.1% of individuals with MPO genotype -463G/G, 34.8% of individuals with genotype G/A, and 4.1% of individuals with genotype A/A. In lung and laryngeal cancer patients, but not in pharyngeal cancer patients, mutant genotypes were significantly less frequent. Crude odds ratios for carriers of one or two A alleles, compared to wild-type G/G, were 0.58 [95% confidence interval (CI), 0.38-0.88; P = 0.011] for lung cancer patients, 0.63 (95% CI, 0.43-0.92; P = 0.017) for laryngeal cancer patients, and 0.82 (95% CI, 0.57-1.17; P = 0.27) for pharyngeal cancer patients. The relative risks, adjusted for age, gender, and extent of cigarette smoking were 0.47 (95% CI, 0.28-0.79; P = 0.004), 0.66 (95% CI, 0.44-1.01; P = 0.054), and 0.75 (95% CI, 0.51-1.12; P = 0.16) for lung, larynx, and pharyngeal cancer, respectively. Strikingly, relative risk for carriers of -463A among adenocarcinoma of the lung was 0.24 (95% CI, 0.10-0.58; P = 0.002). Two cases with larynx cancer, one case with lung cancer, and one reference subject displayed novel G/A mutations at -297 nucleotide and -296 nucleotide, destroying a constitutive AciI cleavage site. Our data finally suggest that the MPO -463A variant is a protective factor in the etiology of lung and larynx cancer, but possibly not of pharyngeal cancer.

Glutathione S-transferase GSTM1, GSTM3, GSTP1 and GSTT1 genotypes and the risk of smoking-related oral and pharyngeal cancers.

Several polymorphic glutathione S-transferase enzymes are involved in the detoxification of active metabolites of many potential carcinogens from tobacco smoke and may therefore be important in modulating susceptibility to smoking-related cancers. As part of a hospital-based case-control study performed in France among Caucasian smokers, we studied GSTM1, GSTM3, GSTP1 and GSTT1 gene polymorphisms in 121 patients with oral cavity and pharyngeal cancers and 172 hospital controls using peripheral blood DNA. An increase in risk was found among carriers of the GSTP1 (AG or GG) genotype (OR 1.6, 95% CI 1.0-2.8, p = 0.07) or the GSTT1 null genotype (OR 2.0, 95% CI 1.0-4.0, p = 0.05). The effect of these at-risk genotypes was most marked in subjects with a history of more than 30 years of smoking, among whom the respective ORs were 2.0 (95% CI 1.0-3.9) and 3.3 (95% CI 1.3-8.1), though the interaction tests between these genotypes and duration of smoking were not significant. In contrast, neither the GSTM1 null genotype nor the GSTM3 AA genotype was associated with oropharyngeal cancer risk (OR 0.9, 95% CI 0.5-1.5 and OR = 1.3, 95% CI 0.7-2.3, respectively). Our results thus suggest that GSTP1 and GSTT1 gene polymorphisms modulate susceptibility to smoking-related cancers of the oral cavity and pharynx.

Nitric oxide synthase activity in human squamous cell carcinoma of the head and neck.

OBJECTIVES: To test whether nitric oxide synthase (NOS) is expressed in primary otolaryngologic tumors and whether this expression is associated with the degree of malignancy. STUDY DESIGN: Twenty-six samples from the primary localization of human pharyngolaryngeal squamous cell carcinoma. MATERIALS AND METHODS: the activity of calcium-dependent and calcium-independent NOS was analyzed by the conversion of L-[14C]-arginine into L-[14C]-citrulline. RESULTS: NOS activity is below detectable levels in pharyngolaryngeal mucosa from noncancer patients. In the primary localization of the tumor, calcium-independent NOS activity is maximal at early stages of tumor growth, whereas calcium-dependent activity increases from early to advanced stages. CONCLUSIONS: These data suggest that tumor growth and malignancy is associated with a change in the enzymatic source of NO from calcium-independent NOS to calcium-dependent NOS isoform in primary localization. These data suggest that the inhibition of calcium-independent NOS activity in early stages and/or inhibition of calcium-dependent NOS activity in later stages could delay growth of solid tumors.