Mutagen sensitivity in patients with head and neck cancers: a biologic marker for risk of multiple primary malignancies.

Eighty-four patients with head and neck cancers were evaluated for in vitro sensitivity to mutagens and then followed longitudinally for development of multiple primary malignancies. We assessed mutagen sensitivity by exposing lymphocytes to bleomycin in vitro and quantitating the bleomycin-induced chromosomal breaks per cell. The mutagen-hypersensitive patients, ie, those who expressed greater than 1.0 break per cell, were significantly more likely to develop multiple primary cancers than were patients who were less sensitive (less than or equal to 1.0 break per cell) (relative risk = 4.4; 95% confidence limits = 1.2, 15.8). This relationship was independent of age, sex, site, and treatment of first primary cancer and tobacco or alcohol exposures. Sensitivity to bleomycin-induced chromosomal damage serves as an indicator of genetic susceptibility to multiple primary malignancies in patients with head and neck cancers.

Natural killer cell activity and head and neck cancer: a clinical assessment.

In 127 patients with squamous cell carcinoma of the upper aerodigestive system, an assessment of natural killer (NK) cell function was performed. The mean lytic unit (LU) value of this cancer population was noted to be less than the mean value of 67 age-matched controls assessed concurrently. The major determinant of cytolytic function was related to the growth pattern of the tumor. Increased NK cell function was observed in patients with lesions that were more locally or regionally aggressive, i.e., that infiltrated surrounding anatomic structures. The magnitude of NK cell response also correlated with increased amounts of circulating IgG immunoglobulin to herpes simplex virus-type 1-associated antigens; elevated IgG levels were also associated with locally aggressive lesions. The clinical significance of NK cell activity in these patients is shown by its relationship to disease-free prognosis. Patients with elevated NK activity followed for a mean of 12 months had an improved disease-free survival as compared to the survival of the remaining population. Furthermore, NK LU values were not reflected in standard staging methods, which suggests that the measurement of NK cell function represents an independent prognostic parameter in the patient with head and neck cancer.

Tobacco carcinogen-detoxifying enzyme UGT1A7 and its association with orolaryngeal cancer risk.

BACKGROUND: UDP-glucuronosyltransferase 1A7 (UGT1A7) detoxifies several tobacco carcinogens. We determined whether UGT1A7 expression is observed in normal orolaryngeal tissue and whether UGT1A7 allelic variations are associated with the risk for orolaryngeal cancer. METHODS: UGT1A7 expression in normal orolaryngeal tissue was determined by semiquantitative reverse transcription-polymerase chain reaction (PCR). Buccal cell DNA isolated from 194 case subjects with orolaryngeal cancer and from 388 control subjects who were matched by sex, age, and race was subjected to UGT1A7 genotyping with the use of combined PCR-restriction fragment length polymorphism and allelic discrimination analysis. All statistical tests were two-sided. RESULTS: UGT1A7 messenger RNA was expressed at similar levels in the esophagus, tongue, tonsil, floor of the mouth, and larynx. Genotyping revealed the presence of three variant reduced-activity UGT1A7 alleles in both Caucasians and African-Americans. Individuals with any of the predicted low-activity UGT1A7 genotypes had an increased risk of orolaryngeal cancer (odds ratio [OR] = 3.7; 95% confidence interval [CI] = 1.7 to 8.7) relative to subjects with the wild-type genotype. Both Caucasians and African-Americans with the low-activity genotypes had statistically significantly increased orolaryngeal cancer risk compared with Caucasians and African-Americans with the wild-type genotype (OR = 2.8 [95% CI = 1.1 to 7.6] and OR = 6.2 [95% CI = 1.2 to 31], respectively). For subjects with the predicted low-activity genotypes, the risks of oral cavity cancer (OR = 4.2; 95% CI = 1.7 to 10) and laryngeal cancer (OR = 3.7; 95% CI = 0.99 to 14) were similar. There was no association between UGT1A7 genotype and orolaryngeal cancer risk in never smokers, whereas subjects with predicted low-activity UGT1A7 genotypes who were light smokers (OR = 3.7; 95% CI = 1.1 to 12) or heavy smokers (OR = 6.1; 95% CI = 1.5 to 25) had an increased risk. CONCLUSIONS: The tissue expression of UGT1A7 is consistent with the possibility of a physiologic role in orolaryngeal cancer. Variations in the UGT1A7 gene that reduce UGT1A7 activity may affect the risk of smoking-related orolaryngeal cancer.

Mutagen sensitivity as a risk factor for second malignant tumors following malignancies of the upper aerodigestive tract.

BACKGROUND: Second malignant tumors in patients successfully treated for an initial cancer of the upper aerodigestive tract are an important cause of morbidity and mortality. Biologic markers capable of identifying high-risk subgroups of patients who could be targeted for intensive clinical surveillance, therefore, have immense therapeutic and prognostic relevance. We previously demonstrated in a pilot study of 84 patients with cancers of the upper aerodigestive tract that mutagen sensitivity was a significant predictor of risk of developing second malignant tumors. PURPOSE: We extended the study to include 278 patients diagnosed with previously untreated cancers of the upper aerodigestive tract from 1987 to August 1993. METHODS: For each patient, base-line (pretreatment) mutagen sensitivity was measured in vitro in 50 metaphases established from peripheral lymphocyte cultures. Patients with an average of more than 1 chromosomal break/cell were deemed mutagen hypersensitive. Cox proportional hazards analysis was used to predict the risk of developing second malignant tumors associated with mutagen sensitivity. RESULTS: Overall, 44% of the case group exhibited mutagen hypersensitivity. There were no differences in the distribution of mutagen hypersensitivity by site, sex, stage of disease, or smoking status. There were 17 synchronous and 11 metachronous cancers, of which 15 (54%) were smoking-related malignancies. Sixteen (13.1%) of the mutagen-sensitive patients developed second malignant tumors, compared with 12 (7.7%) of the nonsensitive patients. The mean break/cell value (+/- SD) for patients developing second malignant tumors was 1.17 (+/- 0.54), compared with 0.98 (+/- 0.44) for patients with only one cancer (P = .04). Mutagen hypersensitivity conferred a relative risk of 2.67 (95% confidence interval = 1.22-5.79) of developing second malignant tumors. CONCLUSIONS: Mutagen hypersensitivity increases the risk of developing second malignant tumors. IMPLICATIONS: Future research should focus on the molecular mechanisms underlying mutagen sensitivity.

Genetic susceptibility to head and neck squamous cell carcinoma.

BACKGROUND: In addition to influences of exposure to carcinogenic compounds, the development of cancer may depend on an individual intrinsic cancer susceptibility. Biomarkers for cancer susceptibility can be powerful additions to epidemiologic analyses. PURPOSE: This multicenter, case-control analysis combines previously published data and new data to substantiate the value of mutagen sensitivity as a biomarker of susceptibility to head and neck squamous cell carcinoma and, more importantly, to gain insight into the interaction between susceptibility and exposure to carcinogens. METHODS: Mutagen sensitivity (mean number of chromatid breaks per cell of cultured lymphocytes treated with bleomycin in the late S-G2 phase of the cell cycle) was determined in 313 patients with head and neck cancer and in 334 control subjects at two major U.S. medical institutions and one European institution, yielding a unique study population. The ages of the case and control subjects, as well as their history of use of tobacco and alcohol, were also recorded. The relationships between variables were analyzed by use of Student's t tests, Spearman's rank correlations, and multiple linear regression. For estimation of cancer risk, crude odds rations (ORs) were measured and multiple logistic regression was performed. All P values were based on two-sided tests. RESULTS: There were no differences across institutions in the distribution of mutagen sensitivity (Kruskal-Wallis test) for both case subjects and control subjects. Values for case subjects were consistently and significantly (P<.0001) higher than values for control subjects in the overall analyses. Age and tobacco or alcohol use did not influence the outcome in terms of mutagen-sensitivity values for either the case or the control subjects. A mean number of breaks per cell dichotomized at 1.0 was found to be the best predictor of a hypersensitive phenotype. For nonsensitive, heavy smokers, the OR was 11.5 (95% confidence interval [CI] = 5.0-26.6). This risk increased dramatically in mutagen-hypersensitive, heavy smokers to 44.5 (95% CI = 17.4-114.0). Multiple logistic regression analysis confirmed these results, and a significant trend was found (P<.01) for the dose-dependent increase in cancer risk by smoking. The consumption of alcohol potentiated the effects of smoking, resulting in an OR of 57.5 (95% CI = 17.5-188.0) in hypersensitive persons. CONCLUSIONS: Mutagen sensitivity was found to be a biomarker of cancer susceptibility. This study underscores the importance of utilizing both susceptibility markers and the exposure data for the identification of persons at high risk of developing cancer. IMPLICATIONS: More accurate risk estimation can define susceptible subgroups who might be targeted for intensive behavioral interventions, surveillance through screening, and enrollment in chemoprevention programs.

13-cis-retinoic acid and interferon alpha-2a: effective combination therapy for advanced squamous cell carcinoma of the skin.

BACKGROUND: Retinoids (vitamin A derivatives) and interferon-alpha (IFN-alpha) are potent regulators of malignant cell differentiation and proliferation, and both have immunomodulatory and antiangiogenesis activity. A large body of preclinical and clinical data supports the use of combination therapy with 13-cis-retinoic acid (13-cRA) and IFN-alpha in patients with squamous cell carcinoma of the skin. This carcinoma is an extremely common and frequently severely disfiguring cancer, for which about 10% of patients remain uncured following standard local therapy. PURPOSE: Our purpose was to test whether a 20% or greater complete response rate could be achieved using a combination of these two agents in patients with advanced squamous cell carcinoma of the skin in whom local therapy had failed or was unfeasible or who had regional and/or distant metastases. METHODS: Thirty-two patients with heavily pretreated, advanced inoperable cutaneous squamous cell carcinoma of the skin were given a combination of oral 13-cRA (1 mg/kg per day) and subcutaneous recombinant human IFN alpha-2a (3 million units per day) for at least 2 months, unless disease progressed earlier, in a phase II trial. RESULTS: Nineteen (68%) of the 28 assessable patients responded, seven (25%) of whom had complete responses. Response rates were 93% (13 of 14) in patients with advanced local disease (six complete responses), 67% (four of six) in patients with regional disease (no complete responses), and 25% (two of eight) in patients with distant metastases (one complete response). The relationship between decreased response rate and increased extent of disease was highly statistically significant (P less than .005, chi-square test). The median response duration was greater than 5 months. No life-threatening toxic effects occurred in assessable patients treated with this combination, although dose reductions were required in 18 patients. The major limiting side effect in this elderly patient population (median age, 67 years) was cumulative fatigue. CONCLUSION: These results indicate that combined systemic therapy with 13-cRA and IFN alpha-2a is highly effective in patients with advanced squamous cell carcinoma of the skin.

Association of levels of circulating C1q binding macromolecules with induction chemotherapy response in head and neck cancer patients.

Ninety-five untreated patients with squamous cell carcinoma of the upper aerodigestive tract expressed significantly higher levels of C1q-binding macromolecules as compared to 45 noncancer-bearing controls. No relationship between C1q-binding macromolecules and levels of circulating IgG-immune complexes as determined by the solid-phase C1q-binding assay or the C3d-solid-phase assay could be defined suggesting that C1q-binding macromolecules were distinct from IgG-circulating immune complexes. An elevated level of C1q-binding macromolecules within these patients was predictive of subsequent response to induction chemotherapy; those with elevated levels characteristically showed no response. Using multivariate logistic regression analysis including the covariates of American Joint Committee staging parameters as well as C1q assay results, levels of the isolated macromolecules added significant prognostic information as to the probability of chemotherapeutic response. The quantitation of C1q macromolecules has clinical implication as to choice of therapeutic regimens against head and neck cancer. The nature of these substances remains to be defined.

Chromosome sensitivity to bleomycin-induced mutagenesis, an independent risk factor for upper aerodigestive tract cancers.

Defective DNA repair capability, measured by enumerating mutagen-induced chromosomal lesions, might explain variable host susceptibility to the action of environmental carcinogens. We compared sensitivity to bleomycin-induced chromosome damage in 75 patients (53 men and 22 women) with previously untreated upper aerodigestive tract malignancies with that in 62 healthy control subjects. Data on tobacco and alcohol use were derived from a detailed, self-administered cancer risk factor questionnaire. Forty-five patients and 13 controls were sensitive to bleomycin-induced mutagenesis (average breaks/cell greater than 0.8). Differential susceptibility was detected in patients categorized by primary tumor location. Odds ratios for chromosome sensitivity were significantly elevated for all sites (odds ratio = 10.3 for pharyngeal cancers, 8.0 for laryngeal cancers, and 3.8 for oral cavity cancers). On logistic regression analysis, chromosome sensitivity remained a strong and independent risk factor after adjustment for potential confounding from age, sex, and tobacco and alcohol use (odds ratio = 4.3, 95% confidence limits = 2.0, 10.2). Despite the small study size and design constraints, the strength of the association with chromosome sensitivity even after adjustment for potential confounders is impressive and suggests a promising avenue for further research. The preventive implications of a valid marker for carcinogen sensitivity are manifold.

Retinoids suppress epidermal growth factor-induced transcription of cyclooxygenase-2 in human oral squamous carcinoma cells.

Cyclooxygenase-2 (Cox-2), the inducible form of cyclooxygenase, is up-regulated in tumors and transformed cells. Because this enzyme catalyzes the formation of prostaglandins from arachidonic acid, chemopreventive strategies that suppress its expression could be useful for preventing cancer. We investigated whether retinoids suppressed basal expression of Cox-2 or EGF-mediated induction of Cox-2 in human oral squamous carcinoma cells. Treatment with retinoids [all-trans-retinoic acid (all-trans-RA), 9-cis-RA, 13-cis-RA, and retinyl acetate] suppressed both basal levels of Cox-2 and EGF-mediated induction of Cox-2 protein and synthesis of prostaglandin E2. Retinoids also suppressed the induction of Cox-2 mRNA by EGF. Transient transfection experiments showed that EGF caused about a 100% increase in Cox-2 promoter activity, an effect that was suppressed by retinoids. Levels of epidermal growth factor receptor were unaffected by retinoids. Epidermal growth factor caused a nearly 10-fold increase in mitogen-activated protein kinase activity; this effect was not blocked by retinoids.

Retinoids suppress phorbol ester-mediated induction of cyclooxygenase-2.

Cyclooxygenase-2 expression is up-regulated in transformed cells and tumors. Because this enzyme catalyzes the synthesis of prostaglandins, strategies aimed at suppressing its expression may prove useful in preventing or treating cancer. We investigated the ability of retinoids to suppress phorbol ester-mediated induction of cyclooxygenase-2 in human oral epithelial cells. Treatment with phorbol myristate acetate (PMA) resulted in approximately a 3-fold increase in the production of prostaglandin E2 (PGE2). Retinoids [all-trans-retinoic acid (RA), 13-cis-RA, and retinyl acetate] markedly suppressed PMA-mediated increases in amounts of cyclooxygenase-2 (Cox-2) and the production of PGE2. Retinoids also suppressed the induction of Cox-2 mRNA by PMA. Nuclear run-offs revealed increased rates of Cox-2 transcription after treatment with PMA; this effect was inhibited by all-trans-RA. Transient transfection experiments showed that PMA caused about a 2-fold increase in Cox-2 promoter activity, an effect that was suppressed by all-trans-RA. Our data indicate that treatment of oral epithelial cells with PMA is associated with enhanced transcription of Cox-2 and increased production of PGE2. These effects of PMA were inhibited by retinoids.

Significance of C1q-binding macromolecules within the head and neck cancer patient.

Elevated levels of macromolecules, within the peripheral blood of head and neck cancer patients, capable of binding the first component of complement (C1qBM) in vitro have prognostic implication. Namely, elevated levels of C1qBM have been associated with nonresponse to induction chemotherapy. In this investigation, a series of in vitro studies regarding the biological properties of C1qBM were combined with a longitudinal analysis of 112 previously untreated head and neck cancer patients. Our purpose was to shed light on the biological significance of this circulating macromolecule, a substance composed, in part, of IgG and IgM. A potential confounding influence of C1qBM with induction chemotherapy, which could contribute to observed prognostic findings, was negated by two in vitro observations: the macromolecule failed both to bind the chemotherapeutic agents cisplatin, bleomycin, and 5-fluorouracil and to impede the cytotoxic effect of these same drugs on a cultured human head and neck cancer cell line. The clinical relevance of C1qBM was reinforced by the observation that elevated levels predicted a high probability of death with disease (P = 0.005 by Cox's proportional hazards model). The prognostic implication was independent of the use of induction chemotherapy, i.e., patients with high C1qBM levels treated with multimodality therapy not composed of anticancer drugs did equally poorly. Thus, the prognostic significance of C1qBM in patients undergoing induction chemotherapy appears independent of drug effect and appears reflective of tumors that are more rapidly progressive and potentially less responsive to therapeutic intervention, including combinations of surgery, radiation, and/or chemotherapy.

Immunologic determinants of head and neck cancer response to induction chemotherapy.

Various measures of immune response were assessed prior to induction chemotherapy (intravenous [IV] cisplatin, fluorouracil [5-FU], and bleomycin) in 43 previously untreated head and neck cancer patients to derive a clinical response prediction model. These were parameters of functional cellular immunity (natural killer [NK] cell activity, lymphocyte blastogenesis response to mitogens), total lymphocyte and lymphocyte subset numbers and percentages, and circulating humoral immunity (total immunoglobulin, immunoglobulin classes, and C1q binding activity [C1q BA]). The C1q BA may reflect levels of circulating immune complexes within peripheral blood. The objective primary tumor response rate was 65% (16 complete responses and 12 partial responses). Univariate logistic regression analysis showed that failure to respond to therapy was significantly related to higher value (vis-à-vis response) of humoral immune parameters total immunoglobulin (Ig), P less than .01; IgG, P less than .01; and C1q BA, P less than .001. No association between cellular immune response measurements and response to chemotherapy was identified. By multivariate logistic regression analysis, only C1q BA levels were predictive of drug therapy responsiveness (P less than .001). Results extend our previous investigations regarding C1q BA measurement in head and neck cancer patients, and show that C1q BA levels add accuracy of prediction of subsequent chemotherapy response to that based solely on standard staging criteria and other parameters of immune status.

Clinical correlates of circulating immune complexes and antibody reactivity in squamous cell carcinoma of the head and neck. The Department of Veterans Affairs Laryngeal Cancer Study Group.

PURPOSE: To evaluate the correlation between the presence and titer of host-derived antibody reactivity, circulating immune complexes, and clinical course and prognosis in patients with squamous cell carcinoma of the head and neck (SCCHN). MATERIALS AND METHODS: Serum samples, obtained from untreated patients with squamous cell carcinoma of the larynx entered onto a multiinstitutional trial, were evaluated for the presence of elevated circulating immune complexes (221 patients) and host-derived antibody directed against two SCCHN cell lines (107 patients). RESULTS: Patients had significantly elevated levels of circulating immune complexes as measured by C1q binding compared with normal controls. Patients with higher levels of circulating immune complexes were less likely to respond to chemotherapy. No correlations were noted between immune complex levels and stage of disease, nodal status, site of disease, recurrence, or survival. Evaluation of native antibody titers for their relationship to clinical correlates showed no statistically significant associations. In sera subjected to immune complex dissociation, patients with moderately or poorly differentiated tumors had significantly higher antibody titers when compared with patients with well-differentiated tumors. Because marked variation in the increase of antibody titers following immune complex dissociation was noted, the ratio of immune complex-dissociated to native antibody titer was examined. Patients with a high ratio had a lower proportion of complete and partial responses to chemotherapy. CONCLUSION: Our results support the conclusion that the formation of tumor-associated immune complexes in patients with SCCHN is associated with a decreased response to chemotherapy.

In vivo native cellular fluorescence and histological characteristics of head and neck cancer.

Native cellular fluorescence (NCF) represents the innate capacity of tissues to absorb and emit light of a specified wavelength. The ability to define the relationship of in vivo NCF with biological characteristics of neoplastic disease may allow for an improved understanding of the clinical course of disease. Head and neck cancers from 35 patients were evaluated in vivo for NCF characteristics using a xenon lamp-based spectrometer coupled to a handheld fiberoptic probe. Spectral assessment was limited to lambda 450-nm emission characteristics, in which tissues were excited at various wavelengths, ranging from lambda 290 nm to lambda 415 nm, and the intensity of lambda 450 nm emission was recorded. Each cancer was subsequently biopsied and assessed for histological differentiation by a pathologist who was blinded to NCF analysis. Considerable variation in spectral characteristics between head and neck cancers was identified, which was determined, in part, by NCF characteristics of the normal mucosa from the same patient. Poorly differentiated tumors were more likely than well- or moderately differentiated tumors to have lower excitation maxima (P < 0.05 by ANOVA). Most significantly, the tumor differentiation status, as well as the probability of demonstrating recurrent disease, could also be related to the NCF characteristics of the patient's normal mucosa from the same site within the upper aerodigestive tract. NCF analysis may represent an effective tool to identify biological characteristics of head and neck tumors in vivo without the need for invasive biopsies. Results suggest the need to explore the determinants of NCF characteristics expressed by clinically normal mucosa.

A simple method for fixation and microdissection of frozen fresh tissue sections for molecular cytogenetic analysis of cancers.

Microdissection has been widely used for procuring DNA from specific microscopic regions of formalin fixed, paraffin embedded tissue sections. We have developed a method for fixation and microdissection of frozen fresh biopsy tissue sections. Five micrometer frozen fresh tissue sections were fixed with ethanol and stored at room temperature. Well defined regions from hematoxylin and eosin (H & E) stained or unstained sections were briefly steamed and microdissected using a needle. The dissected tissue was digested with proteinase K and DNA was isolated. Whole genome amplifications were obtained by degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) from these samples. The reliability of this technique was demonstrated by comparing conventional comparative genomic hybridization (CGH) with DOP-PCR-CGH. The advantages of this method are that frozen fresh sections can be fixed easily and stored for more than 4 years, it is easy to microdissect and pick-up very minute regions (0.1 mm(2)), and it is rapid; microdissection and purification can be accomplished within 3 h. Using DNA from microdissected sections, DOP-PCR-CGH revealed genetic abnormalities more accurately than conventional CGH. Although this novel method was demonstrated using DOP-PCR-CGH, we believe that it will be useful for other genetic analyses of specific small regions and cell populations. We also observed whether storage time, H & E staining and crude DNA extracts affected the quality of amplified DNA. DNA integrity was maintained for at least 49 months in ethanol fixed sections that were stored at room temperature, but DNA was gradually degraded after one month if the ethanol fixed sections had been H & E stained and stored. When crude DNA extracts from H & E stained sections were used, the size of the DOP-PCR product was reduced. Our study suggests that ethanol fixed tissue sections may be stored at room temperature for at least 4 years without DNA degradation, the H & E stains may not affect the quality of amplified DNA, but H & E or other components in the staining process may reduce the size of DOP-PCR product, which is critical for the quality of CGH hybridization.

Association between glutathione S-transferase pi genetic polymorphisms and oral cancer risk.

Polymorphisms in the gene encoding the glutathione S-transferase (GST) pi metabolizing enzyme have previously been associated with susceptibility to various cancers. In this study, the importance of GSTP1 genotypes as determinants of risk for oral cancer was assessed by examining the prevalence of GSTP1 alleles in 157 incident oral cancer cases and 260 non-cancer control individuals frequency-matched by race, sex, and age at diagnosis (+/- 5 years). The GSTP1*A, GSTP1*B, GSTP1*C, and GSTP1*D alleles were elucidated by polymerase chain reaction-restriction fragment length polymorphism analysis of polymorphisms present in codons 105 (isoleucine:valine) and 114 (alanine:valine) of the GSTP1 gene. Increased risk for oral cancer was observed in individuals who were homozygous for any combination of GSTP1 polymorphic alleles (i.e. *B, *C, and/or *D alleles; odds ratio = 2.4, 95% confidence interval = 1.2-4.8). Similar risk was observed in both Caucasians (odds ratio = 2.6, 95% confidence interval = 1.1-6.2) and African-Americans (odds ratio = 2.3, 95% CI = 0.68-7.5). A greater risk was observed in individuals with the GSTP1 (Var/Var) genotype who were exposed to low levels of smoking (i.e. < or = 20 pack-years [py], odds ratio = 3.4, 95% confidence interval = 1.1-11) than among heavier smokers (i.e. > 20 pack-years [py], odds ratio = 1.4, 95% confidence interval = 0.48-4.0). These results suggest that GSTP1 genotype may play a role in risk for oral cancer particularly among lighter smokers.

Comparison of GSTM polymorphisms and risk for oral cancer between African-Americans and Caucasians.

Two members of the mu class of glutathione S-transferase (GST) genes, GSTM1 and GSTM3, have polymorphic alleles which have been associated with altered levels of GST mu protein expression and may be linked to increased risk for several tobacco-related cancers. Oral cancer is a tobacco-related disease that affects African-American men at a significantly higher incidence than Caucasian men. To examine the potential role of GSTM polymorphisms in risk for oral cancer in African-Americans and Caucasians, the prevalences of the GSTM1 null and GSTM3 intron 6 polymorphisms were examined in 63 African-American and 101 Caucasian patients with histologically confirmed primary oral cancer, as well as in 133 African-American and 213 Caucasian matched control subjects. In African-Americans, the odds ratio for oral cancer associated with the GSTM1 (0/0) genotype was 3.1 [95% confidence interval (CI) = 1.1-8.5], with the association between the GSTM1 (0/0) genotype and oral cancer risk strongest in heavy smokers [i.e. > 24 pack-years; odds ratio (OR) = 5.4, 95% CI = 1.2-24]. Using the potentially most protective GSTM1 [+]/GSTM3 (B/B) genotype as the reference group, increased risk for oral cancer was observed in African-Americans with the GSTM1 [+]/GSTM3 [(A/A) + (A/B)] (OR = 2.2, 95% CI = 0.82-6.0), GSTM1 (0/0)/GSTM3 (B/B) (OR = 4.3, 95% CI = 1.1-16), and GSTM1 (0/0)/GSTM3 [(A/A) + (A/B)] (OR = 6.6, 95% CI = 1.2-38) genotypes (P < 0.01, trend test). No significant associations were observed between GSTM genotype and oral cancer risk in Caucasians. These results suggest that the GSTM1 null and GSTM3 intron 6 polymorphisms play an important role in risk for oral cancer among African-Americans and implicates the mu class of GSTs as important tobacco carcinogen detoxifying enzymes in this population.

Mutagen sensitivity: a biological marker of cancer susceptibility.

We intend to continue our exploration of the bleomycin assay as a biological marker for the development of environmentally induced cancers. The impetus for such efforts would be enhanced through effective integration of cancer screening and intervention to achieve diminished cancer mortality. Currently, we are integrating combining bleomycin sensitivity screening to chemopreventive therapy against second primary malignancies in head and neck cancer patients. Previous studies have demonstrated that cis-retinoic acid, the agent used in our chemopreventive trial, is effective in such circumstances (35). Our purpose is to identify a high-risk subpopulation through application of the bleomycin sensitivity assay and then demonstrate that we can modulate the carcinogenic process with cis-retinoic acid. The use of genetic markers clearly enhances the power and precision of epidemiological research. The preventive implications of precise and valid markers for carcinogen sensitivity are obvious. We are aware of the need for extensive validation of the assay and for rigorously designed and conducted epidemiological studies. The strength of the association between cancer risk and mutagen sensitivity, despite the inherent problems in the size and design of the studies, is noteworthy. The thesis that chromosome instability and defective DNA repair may underlie susceptibility to environmental carcinogenesis is plausible and presents a promising avenue for further multidisciplinary research.

Mutagen sensitivity in upper aerodigestive tract cancer: a case-control analysis.

Variability in DNA repair capability may be a determinant of interindividual difference in susceptibility to carcinogenic exposures. A cytogenetic assay which quantifies chromosomal breakage induced by in vitro exposure to a clastogen provides an indirect measure of repair. We report the results of a case-control study of upper aerodigestive tract cancers assessing differences in mutagen sensitivity based on this assay. There were 108 cases with previously untreated squamous cell cancers and 108 age and sex frequency-matched controls selected from blood donors to The University of Texas M. D. Anderson Cancer Center. Sixty-nine% of the cases, compared with 44% of the controls, were classified as mutagen sensitive (breaks per cell > or = 0.8). On multivariate analysis, mutagen sensitivity [odds ratio (OR), 2.5], heavy cigarette smoking (OR, 4.8), and heavy alcohol consumption (OR, 3.1) were associated with significantly increased risk. Stratified analyses showed that the combined effects of cigarette smoking (OR, 8.1) and mutagen sensitivity (OR, 3.2) were suggestive of a multiplicative effect (OR, 23.0). The combined estimate for alcohol use (OR, 3.0) and mutagen sensitivity (OR, 3.0) was 5.8. These data confirm those of a previously published preliminary study of upper aerodigestive cancers and underscore the importance of considering interindividual susceptibility in cancer risk characterization, even for those cancers with well quantified exposures.

Blood and urine levels of tea catechins after ingestion of different amounts of green tea by human volunteers.

The inhibitory activity of tea against tumorigenesis has been demonstrated in many animal models and has been suggested by some epidemiological studies. Such activity has generally been attributed to tea catechins. To understand the bioavailability of tea catechins in humans, we gave 18 individuals different amounts of green tea and measured the time-dependent plasma concentrations and urinary excretion of tea catechins. After taking 1.5, 3.0, and 4.5 g of decaffeinated green tea solids (dissolved in 500 ml of water), the maximum plasma concentration (Cmax) of (-)-epigallocatechin-3-gallate (EGCG) was 326 ng/ml, the Cmax of (-)-epigallocatechin (EGC) was 550 ng/ml, and the Cmax of (-)-epicatechin (EC) was 190 ng/ml. These Cmax values were observed at 1.4-2.4 h after ingestion of the tea preparation. When the dosage was increased from 1.5 to 3.0 g, the Cmax values increased 2.7-3.4-fold, but increasing the dose to 4.5 g did not increase the Cmax values significantly, which suggested a saturation phenomenon. The half-life of EGCG (5.0-5.5 h) seemed to be higher than the half-life of EGC or EC (2.5-3.4 h). EGC and EC, but not EGCG, were excreted in the urine. Over 90% of the total urinary EGC and EC was excreted within 8 h. When the tea dosage was increased, the amount of EGC and EC excretion seemed to increase, but a clear dose-response relationship was not observed. The present study provides basic pharmacokinetic parameters of green tea catechins in humans; these parameters may be used to estimate the levels of these compounds after drinking tea.