Metabolic polymorphisms, smoking, and oral cancer in Puerto Rico.

Genetic polymorphisms resulting in variation in metabolism of tobacco carcinogens may influence oral cancer risk. In a population-based case-control study in Puerto Rico, genotypes of CYP1A1, GSTM1, and GSTT1 were determined by a PCR-based method for 132 oral cancer patients and 143 control subjects. Genotype-associated risks were estimated by logistic regression. The null variant of GSTM1 was associated with a marginally significant decrease in oral cancer risk [odds ratio (OR) = 0.6, 95% confidence interval (CI) = 0.3-1.0, and P for trend = 0.09]. Risks increased with increasing cigarette use among subjects with the GSTM1-present genotype (P for trend <0.0001), rising to OR = 9.5, 95% CI = 3.0-30, among the heaviest cigarette users. In contrast, among subjects with the GSTM1-null genotype, risks did not clearly increase with increasing cigarette use (P for trend <0.61; OR = 1.8, 95% CI = 0.6-5.2 among the heaviest tobacco users). The GSTT1-null variant (OR = 1.0, 95% CI = 0.5-1.9) and CYP1A1(462Val) variant (OR = 0.9, 95% CI = 0.5-1.7) were not associated with the risk. Risks rose with increasing cigarette use in a similar manner for subjects with or without the CYP1A1(462Val) variant (P for interaction = 0.3) and for subjects with or without the GSTT1-null genotype (P for interaction = 0.4). In conclusion, cigarette use significantly increased the risk of oral cancer in this population. The GSTM1-present genotype was associated with higher tobacco-associated risk for oral cancer among heavy smokers than the null genotype.

Sugarcane farming, occupational solvent exposures, and the risk of oral cancer in Puerto Rico.

The work history information from a population-based case-control study conducted in Puerto Rico was analyzed using a job exposure matrix to investigate the relationship between occupational exposures and cancers of the oral cavity or pharynx. After adjustment for age, alcohol, smoking, and residence in a logistic model, the risk for cancer of the oral cavity, but not the pharynx, was significantly elevated among farm workers in the sugarcane industry (OR = 4.4, 95% CI = 1.4-13.6). An exposure-response trend was seen for cumulative exposure to solvents, with an OR = 3.2 (95% CI = 0.8-12.6) in the highest exposure category. The overall contribution to the risk of cancer of the oral cavity or pharynx associated with occupational exposures in Puerto Rico appears to be small, however, the elevated risks were seen among sugarcane farmers and subjects with high cumulative exposure to solvents.

Microsatellite polymorphisms in the epidermal growth factor receptor (EGFR) gene and the transforming growth factor-alpha (TGFA) gene and risk of oral cancer in Puerto Rico.

OBJECTIVES AND METHODS: Risks of oral cancer related to a CA microsatellite repeat polymorphism in intron 1 of the epidermal growth factor receptor (EGFR) gene and a TaqI polymorphism in the transforming growth factor-alpha (TGFA) gene were evaluated in a population-based case-control study consisting of 157 cases and 149 controls recruited in Puerto Rico. RESULTS: Carriers of > or = 16 CA repeats in EGFR showed a 1.9-fold increased risk for oral cancer (OR=1.9, 95% CI=1.0-3.5). Risks also tended to increase with decreasing number of alleles with > or = 16 CA repeats (P for trend=0.06). Our data suggested a non-significant reduction in risk for subjects heterozygous for the TGFA polymorphism (OR=0.6, 95% CI=0.2-1.3). CONCLUSIONS: The EGFR-associated risk appeared to be independent of tobacco and alcohol use and may be restricted primarily to subjects who consumed low amounts of fresh fruits and vegetables (OR=5.9, 95%CI: 2.3-15.2). These data implicate dietary and molecular targets for oral cancer prevention.

Alcohol concentration and risk of oral cancer in Puerto Rico.

Alcohol consumption is a major risk factor for cancers of the mouth and pharynx (oral cancer), but the differential risks by beverage type are unclear. In this 1992-1995 study, the authors examined oral cancer risk in Puerto Rico, comparing alcohol intake among 286 male cases aged 21-79 years and 417 population-based male controls, frequency matched by age. Heavy consumers of liquor (>/=43 drinks per week) had strongly increased risks of oral cancer (odds ratio = 6.4, 95% confidence interval: 2.4, 16.8); beer/wine showed only modest effects. Among liquor drinkers, risks were consistently greater for those who drank straight (undiluted) liquor than for those who usually drank mixed (diluted) liquor (odds ratio = 4.0, 95% confidence interval: 2.4, 6.7). Risks associated with combined exposure to tobacco were also more pronounced when subjects drank liquor straight. The elevated risks associated with drinking homemade rum were similar to those for other types of liquor. These results suggest that alcohol concentration is a risk factor for oral cancer independent of the total quantity of alcohol consumed.

Folate intake, serum homocysteine and methylenetetrahydrofolate reductase (MTHFR) C677T genotype are not associated with oral cancer risk in Puerto Rico.

We examined the relationships between folate and methionine intake, serum homocysteine levels (as a biomarker for folate metabolism), and methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism genotype and risk of oral cancer in a population-based, case-control study in Puerto Rico. Structured questionnaires were used to collect information on demographic factors, usual adult diet, and tobacco and alcohol use. Oral epithelial cells and blood samples were collected from a subset of subjects. Analyses were conducted by logistic regression, adjusting for age, sex, lifetime smoking and lifetime alcohol intake, with the following numbers of cases/controls, respectively: dietary data (341/521); MTHFR genotype (148/149); and homocysteine (60/90). Although increased folate intake was associated with decreased oral cancer risk [adjusted odds ratio (OR) in highest vs. lowest quartile = 0.6, 95% confidence interval (CI): 0.4, 1.0, P(trend) = 0.05)], this finding was due almost entirely to folate intake from fruit (adjusted OR = 0.4, 95% CI: 0.2, 0.6; P(trend) = 0.0001), whereas other dietary folate sources showed no clear association. Methionine intake and serum homocysteine levels were not associated with oral cancer risk. Subjects with the MTHFR C677T homozygous variant (TT) genotype had a nonsignificantly lower risk, and risk patterns tended to differ by level of folate, methionine, alcohol intake and smoking, although the power to detect significant associations in subgroups of these variables was low. Risks for oral cancer are not folate specific; preventive recommendations for this disease should emphasize the importance of a healthy diet, including substantial intake of fruits.