Glutathione S-transferase P1 Ile105Val polymorphism and oral cancer risk: a meta-analysis

Single nucleotide polymorphisms and microsatellites in the canine glutathione S-transferase pi 1 (GSTP1) gene promoter

BACKGROUND

Genetic polymorphisms within the glutathione S-transferase P1 (GSTP1) gene affect the elimination of toxic xenobiotics by the GSTP1 enzyme. In dogs, exposure to environmental chemicals that may be GSTP1 substrates is associated with cancer. The objectives of this study were to investigate the genetic variability in the GSTP1 promoter in a diverse population of 278 purebred dogs, compare the incidence of any variants found between breeds, and predict their effects on gene expression. To provide information on ancestral alleles, a number of wolves, coyotes, and foxes were also sequenced.

RESULTS

Fifteen single nucleotide polymorphisms (SNPs) and two microsatellites were discovered. Three of these loci were only polymorphic in dogs while three other SNPs were unique to wolves and coyotes. The major allele at c.-46 is T in dogs but is C in the wild canids. The c.-185 delT variant was unique to dogs. The microsatellite located in the 5' untranslated region (5'UTR) was a highly polymorphic GCC tandem repeat, consisting of simple and compound alleles that varied in size from 10 to 22-repeat units. The most common alleles consisted of 11, 16, and 17-repeats. The 11-repeat allele was found in 10% of dogs but not in the other canids. Unequal recombination and replication slippage between similar and distinct alleles may be the mechanism for the multiple microsatellites observed. Twenty-eight haplotypes were constructed in the dog, and an additional 8 were observed in wolves and coyotes. While the most common haplotype acrossbreeds was the wild-type *1A(17), other prevalent haplotypes included *3A(11) in Greyhounds, *6A(16) in Labrador Retrievers, *9A(16) in Golden Retrievers, and *8A(19) in Standard Poodles. Boxers and Siberian Huskies exhibited minimal haplotypic diversity. Compared to the simple 16*1 allele, the compound 16*2 allele (found in 12% of dogs) may interfere with transcription factor binding and/or the stability of the GSTP1 transcript.

CONCLUSIONS

Dogs and other canids exhibit extensive variation in the GSTP1 promoter. Genetic polymorphisms within distinct haplotypes prevalent in certain breeds can affect GSTP1 expression and carcinogen detoxification, and thus may be useful as genetic markers for cancer in dogs.

GTSP1 expression in non-smoker and non-drinker patients with squamous cell carcinoma of the head and neck

Introduction

The main risk factors for head and neck squamous cell carcinoma (HNSCC) are tobacco and alcohol consumption and human papillomavirus (HPV) infection. However, in a subset of patients, no risk factors can be identified. Glutathione S-transferase π (GTSP1) is a carcinogen-detoxifying enzyme that is activated by exposure to carcinogens, and it is associated with a reduction in response to toxic therapies. We studied the expression of GTSP1 in tumor and non-tumor tissue samples from patients with and without these risks to identify whether GTSP1 expression differs according to exposure to carcinogens.

Materials and methods

Non-smoker/non-drinker (NSND) and smoker/drinker (SD) patients were matched according to age, gender, tumor site, TNM stage, grade and histological variants to establish 47 pairs of patients who have been previously tested for HPV. GTSP1 immunostaining was analyzed using a semi-quantitative method with scores ranging from 0 to 3 according to the area of immunostaining.

Results

GTSP1 expression was detected in the tumors of both groups. GTSP1 expression was higher in the non-tumor margins of SD patients (p = 0.004). There was no association between GTSP1 expression and positivity for HPV. No differences in survival were observed according to GTSP1 staining in tumors and non-tumor margins.

Conclusion

This study showed that GTSP1 was expressed in tumors of HNSCC patients regardless of smoking, drinking or HPV infection status. The difference in GTSP1 expression in non-tumor margins between the two groups may have been due to two possible reasons. First, elevated GTSP1 expression in SD patients might be the result of activation of GTSP1 in response to exposure to carcinogens. Second, alternatively, impairment in the detoxifying system of GTSP1, as observed by the reduced expression of GTSP1, might make patients susceptible to carcinogens other than tobacco and alcohol, which may be the underlying mechanism of carcinogenesis in the absence of risk factors.

Low Survival Rates of Oral and Oropharyngeal Squamous Cell Carcinoma

Aim

To assess the epidemiological and clinical factors that influence the prognosis of oral and oropharyngeal squamous cell carcinoma (SCC).

Methods

One hundred and twenty-one cases of oral and oropharyngeal SCC were selected. The survival curves for each variable were estimated using the Kaplan-Meier method. The Cox regression model was applied to assess the effect of the variables on survival.

Results

Cancers at an advanced stage were observed in 103 patients (85.1%). Cancers on the tongue were more frequent (23.1%). The survival analysis was 59.9% in one year, 40.7% in two years, and 27.8% in 5 years. There was a significant low survival rate linked to alcohol intake (p = 0.038), advanced cancer staging (p = 0.003), and procedures without surgery (p < 0.001). When these variables were included in the Cox regression model only surgery procedures (p = 0.005) demonstrated a significant effect on survival.

Conclusion

The findings suggest that patients who underwent surgery had a greater survival rate compared with those that did not. The low survival rates and the high percentage of patients diagnosed at advanced stages demonstrate that oral and oropharyngeal cancer patients should receive more attention.

Association between coffee consumption and the risk of oral cancer: a meta-analysis of observational studies

OBJECTIVE

Quantification of the association between the coffee consumption and risk of oral cancer is still conflicting. Thus, we conducted a meta-analysis to summarize the evidence from epidemiological studies of coffee consumption with the risk of oral cancer.

METHODS

Pertinent studies were identified by a search of PubMed and Web of Knowledge to March 2015. The random effect model was used. Sensitivity analysis and publication bias were conducted.

RESULTS

Data from 12 studies including 4,037 oral cancer cases and 1,872,231 participants were used in this meta-analysis. Pooled results suggested that highest coffee consumption amount versus lowest amount was significantly associated with the risk of oral cancer [summary relative risk (RR) = 0.694, 95% CI = 0.543-0.886, I(2) = 65.0%]. The association was also significant in Europe [summary RR = 0.571, 95% CI = 0.378-0.863], but not in America. No publication bias was found.

CONCLUSIONS

Our analysis suggested that the higher coffee consumption might reduce the risk of oral cancer, especially in Europe.

Association of tea consumption and the risk of oral cancer: a meta-analysis

OBJECTIVES

Epidemiological studies evaluating the association of tea consumption and the risk of oral cancer risk have produced inconsistent results. Thus, we conducted a meta-analysis to assess the relationship between tea consumption and oral cancer risk.

METHODS

Pertinent studies were identified by a search in PubMed, Web of Knowledge and Wan Fang Med Online. The fixed or random effect model was used based on heterogeneity test. Publication bias was estimated using Egger's regression asymmetry test.

RESULTS

Finally, 14 articles with 19 studies comprising 4675 oral cancer cases were included in this meta-analysis. The relative risk (95% confidence interval) of oral cancer for the highest versus the lowest category of tea consumption was 0.853 (0.779-0.934), and the association was significant between oral cancer risk and green tea consumption [0.798 (0.673-0.947)] but not in the black tea consumption [0.953 (0.792-1.146)]. The associations were also significant in Asian and Caucasian.

CONCLUSIONS

Our analysis indicated that tea consumption may have a protective effect on oral cancer, especially in green tea consumption.