Glutathione-S-transferase and p53 polymorphisms in cervical carcinogenesis

Relationship between GSTM1 and GSTT1 polymorphisms and HPV infection: a systematic review

Human Papillomavirus (HPV) is the most important risk factor for cervical cancer, although not the only one. The allelic polymorphism of enzymes acting on carcinogen metabolism has shown to influence the risk of both intraepithelial lesions and cervical carcinogenesis. Several studies found an association between GSTM1/GSTT1 null genotypes and risk of cancer. This research aimed to review studies addressing the relationship between GSTT1 and GSTM1 and HPV infection in women, with or without cervical pathologies. A database search was conducted in four databases - PubMed, LILACS, SciELO, and Virtual Health Library - using the following descriptors: Glutathione transferase, HPV, and Genetic polymorphism. In total, we found 319 studies. After screening titles and abstracts, 27 articles were selected for full-text read, among which 20 were excluded and 7 were included in the review. No study has exclusively approached the relationship between the virus and GSTM1/GSTT1 variants. However, studies investigating the association between single nucleotide polymorphisms (SNPs) and cervical lesions or cancer found a probable relationship between them and infections with high-risk oncogenic subtypes. Although inconclusive, GSTT1 null alleles were more common in women with more aggressive HPV than GSTM1.

Genetic polymorphisms as non-modifiable susceptibility factors to laryngeal cancer

Laryngeal squamous cell carcinoma (LSCC) is a highly disabling disease to the patient, affecting speech, swallowing and respiratory skills. Smoking and alcohol abuse are principal risk factors linked to this disease. Genetic factors can be involved in carcinogenesis by controlling the cell cycle, cell survival, angiogenesis, and invasiveness. Single nucleotide polymorphisms (SNPs) involving specific genes could modulate the risk of LSCC related to known carcinogens by modifying cellular responses, but not all genetic associations are known.

In a case–control study, we assess the associations between cyclooxygenase-2 (COX2), epidermal growth factor (EGF), EGF receptor (EGFR), and tumor suppressor P53 SNPs on the risk of LSCC development in the Chilean population. A total of 85 LSCC patients and 95 healthy volunteers were recruited. SNPs genotype were analyzed from genomic DNA by Polymerase Chain Reaction (PCR)-Restriction Fragment Length Polymorphism (RFLP) and associations were estimated by odds ratios (ORs) using unconditional logistic regressions.

A significant association between COX2 and TP53 SNP and LSCC risk was found, with an OR = 3.27 for COX2 c.-1329A>G (rs689466) SNP, and an OR = 1.94 for TP53 c.215C>G, Pro72Arg (rs1042522) SNP. These findings suggest that COX2 c.-1329A>G and TP53 c.215C>G (Pro72Arg) SNPs may be risk factors for LSCC.

Through this research, we identify two low penetrance genetic variants that may be evaluated as novel biomarkers for this disease, in South American Mestizo populations.

An Updated Meta-Analysis: Risk Conferred by Glutathione S-Transferases (GSTM1 and GSTT1) Polymorphisms to Age-Related Cataract

Purpose. To study the effects of glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) polymorphisms on age-related cataract (ARC). Methods. After a systematic literature search, all relevant studies evaluating the association between GSTs polymorphisms and ARC were included. Results. Fifteen studies on GSTM1 and nine studies on GSTT1 were included in this meta-analysis. In the pooled analysis, a significant association between null genotype of GSTT1 and ARC was found (OR = 1.229, 95% CI = 1.057–1.429, and P = 0.007). In subgroup analysis, the association between cortical cataract (CC) and GSTM1 null genotype was statistically significant (OR = 0.713, 95% CI = 0.598–0.850, and P < 0.001). In addition, GSTM1 null genotype was significantly associated with ARC causing risk to individuals working indoors and not individuals working outdoors. The association between GSTT1 null genotype and risk of ARC was statistically significant in Asians (OR = 1.442, 95% CI = 1.137–1.830, and P = 0.003) but not in Caucasians. Conclusions. GSTM1 positive genotype is associated with increased risk of CC and loses the protective role in persons who work outdoors. Considering the ethnic variation, GSTT1 null genotype is found to be associated with increased risk of ARC in Asians but not in Caucasians.

Human papillomavirus and host genetic polymorphisms in carcinogenesis: a systematic review and meta-analysis

BACKGROUND

As the role of human papillomavirus (HPV) in carcinogenesis continues to rise, the role of genetic factors that modify this risk have become increasingly important. In this study, we reviewed the literature for associations between polymorphisms and HPV in carcinogenesis.

OBJECTIVE

To identify any associations of genetic polymorphisms with oncogenic HPV in carcinogenesis and to evaluate the methodology used.

STUDY DESIGN

Systematic literature review of HPV, genetic polymorphisms, and cancer risk. Odds ratios (OR), interaction terms, and p-values were tabulated. Meta-analyses and measures of heterogeneity were estimated using RevMan 5.1.

RESULTS

The cervix was the most frequently studied cancer site followed by the head and neck. Overall risk of cancer (cancer vs. control) was the most common comparison, whereas reports of initiation (pre-cancer vs. control) and progression (cancer vs. pre-cancer) were rare. Case-series and joint-effect of HPV and genotype on risk was evaluated frequently, but the independent effect of either risk factor alone was rarely provided. P53-Arg72Pro was the most commonly studied polymorphism studied. No consistent interaction was detected by meta-analysis in the HPV(+) [OR 0.98 (0.55-1.76)] or the HPV(-) [OR 1.10 (0.76-1.60)] subsets in head and neck cancer risk. Polymorphisms in genes known to encode proteins that physically interact with HPV were infrequently studied.

CONCLUSION

No consistent polymorphism-HPV interactions were observed. Study design, choice of candidate polymorphisms/genes, and a focus on overall risk rather than any specific portions of the carcinogenic pathway may have contributed to lack of significant findings.

Molecular profiling of cervical neoplasia

Cervical cancer, a potentially preventable disease, remains the second most common malignancy in women worldwide. Human papillomavirus is the single most important etiological agent in cervical cancer, contributing to neoplastic progression through the action of viral oncoproteins, mainly E6 and E7, which interfere with critical cell cycle pathways, p53 and retinoblastoma. However, evidence suggests that human papillomavirus infection alone is insufficient to induce malignant changes and that other host genetic variations are important in the development of cervical cancer. This article will discuss the latest molecular profiling techniques available and review the published literature relating to their role in the diagnosis and management of cervical dysplasia and cancer. It is hoped that these techniques will allow the detection of novel biomarkers at DNA, RNA, microRNA and protein levels, which may ultimately play a role in facilitating early disease diagnosis and in predicting response to therapies, thus allowing the development of personalized treatment strategies.

Meta-analysis of the association between GSTM1 and GSTT1 gene polymorphisms and cervical cancer

AIM

We conducted a meta-analysis to analyze the influence of GSTM1 and GSTT1 gene polymorphisms on cervical cancer risk, and explore gene-environment interactions.

METHODS

Identification of relevant studies was carried out through a search of Medline and the EMbase up to Oct. 2011. All case-control studies that investigated the association between GSTM1 and GSTT1 gene polymorphisms and risk of cervical cancer were included. The pooled odds ratio (OR) was used for analyses of results and the corresponding 95% confidence intervals (CI) were estimated.

RESULTS

A total of 21 case-control studies were included in the meta-analysis of GSTM1 (2,378 cases and 2,639 controls) and GSTT1 (1,229 cases and 1,223 controls) genotypes. The overall results showed that the GSTM1 null was related to an increased risk of cervical cancer (OR=1.50, 95% CI=1.21-1.85). Subgroup analysis were performed based on smoking and ethnicity. Our results showed that smokers with null GSTM1 genotype had a moderate increased risk of cervical cancer (OR=1.85, 95% CI=1.07-3.20). For the ethnicity stratification, moderate significantly increased risk of null GSTM1 genotype was found in Chinese (OR=2.12, 95% CI=1.43-3.15) and Indian populations (OR=2.07, 95% CI=1.49-2.88), but no increased risk was noted in others.

CONCLUSION

This meta-analysis provided strong evidence that the GSTM1 genotype is associated with the development of cervical cancer, especially in smokers, and Chinese and Indian populations. However, no association was found for GSTT1 null genotype carriers.

A comprehensive review on host genetic susceptibility to human papillomavirus infection and progression to cervical cancer

Cervical cancer is the second most common cancer in women worldwide. This is caused by oncogenic types of human papillomavirus (HPV) infection. Although large numbers of young sexually active women get HPV-infected, only a small fraction develop cervical cancer. This points to different co-factors for regression of HPV infection or progression to cervical cancer. Host genetic factors play an important role in the outcome of such complex or multifactor diseases such as cervical cancer and are also known to regulate the rate of disease progression. The aim of this review is to compile the advances in the field of host genetics of cervical cancer. MEDLINE database was searched using the terms, ‘HPV’, ‘cervical’, ‘CIN’, ‘polymorphism(s)’, ‘cervical’+ *the name of the gene* and ‘HPV’+ *the name of the gene*. This review focuses on the major host genes reported to affect the progression to cervical cancer in HPV infected individuals.

Contribution of retinoblastoma LOH and the p53 Arg/Pro polymorphism to cervical cancer

Epidemiological studies indicate that infections by certain types of human papillomaviruses (HPVs) are causally linked to the development of cervical cancer. It is also known that HPV infections alone do not cause progression to cervical cancer, as additional genetic changes such as loss of distinct chromosomal regions, inactivation of tumor-suppressor genes and activation of oncogenes must also occur in order for malignant transformation to take place. In the present study, 78 patients diagnosed with cervical cancer and 36 cervical cancer-free cases (control) were analyzed for high-risk HPV genotypes (16 and 18) by polymerase chain reaction (PCR). Loss of heterozygosity (LOH) of the retinoblastoma gene (Rb) at two polymorphic intronic sites (intron 1 and 17) and the p53 polymorphism in codon 72 were detected by RFLP and allele-specific PCR, respectively. HPV 16 and 18 were found at frequencies of 93.6 and 8.3% in the cervical cancer and control samples, respectively. LOH was detected in 63% of patients in intron 1 and/or intron 17. p53 allele frequency for Arg/Arg was 43.6% (34/78), for Arg/Pro 37.2% (29/78) and for Pro/Pro 19.2% (15/78). The relative risk (RR) of LOH and Arg/Arg alone was 1.7 and 1.1, respectively, while the combined RR for Rb LOH and p53 Arg/Arg was 2.5. The present study showed a significant association of the chromosomal allelic loss of Rb in Sudanese cervical cancer patients, while no such association was observed with other parameters, such as clinical stage and degree of differentiation; hence, it cannot be a determinant of tumor behavior in cervical carcinoma. Although the p53 arginine allele is itself an important risk factor for cervical cancer, the combined risk with LOH of Rb, which appears to be greater, might indicate a possible epistatic effect of the two genes/polymorphisms.

Meta-analysis of association between GSTM1 gene polymorphism and cervical cancer

OBJECTIVE

To investigate association between glutathione S-transferases (GSTs) and cervical cancer.

METHODS

Published literature from PubMed, EMBASE, and other databases were retrieved. All studies evaluating the association between GSTM1/GSTT1 polymorphisms and cervical were included. Pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using fixed- or random-effects model.

RESULTS

A total of 15 case-control studies were included in the meta-analysis of GSTM1 genotypes (1,825 cases and 2,104 controls). The overall result showed that the association between GSTM1 null genotype and risk for cervical cancer was statistically significant (OR=1.53, 95%CI=1.18-2.00). Great heterogeneity was found between studies. Subgroup analysises were performed based on smoking and ethnicity. Our results showed that smokers with null GSTM1 genotype had higher risk of cervical cancer (OR=1.56, 95%CI=1.01-2.41). For the ethnicity stratification, significant increased risk of null GSTM1 genotype was found in Chinese and Indian population, but no increased risk in other population.

CONCLUSIONS

This meta-analysis provides strong evidence that the GSTM1 null genotype is associated with the development of cervical cancer, and especially in Chinese and Indian population, and smoking shows a modification on the association between GSTM1 null genotype and cervical cancer.

A common carcinogen benzo[a]pyrene causes p53 overexpression in mouse cervix via DNA damage

Benzo[a]pyrene (BaP) is cytotoxic and/or genotoxic to lung, stomach and skin tissue in the body. However, the effect of BaP on cervical tissue remains unclear. The present study detected DNA damage and the expression of the p53 gene in BaP-induced cervical tissue in female mice. Animals were intraperitoneally injected and orally gavaged with BaP at the doses of 2.5, 5, and 10mg/kg twice a week for 14 weeks. The single-cell gel electrophoresis (SCGE) assay was used to detect the DNA damage. Immunohistochemistry (IHC) and in situ hybridization (ISH) were used to detect the expression of p53 protein and p53 mRNA, respectively. The results showed that BaP induced a significant and dose-dependent increase of the number of cells with DNA damaged and the tail length as well as Comet tail moment in cervical tissue. The expression level of p53 protein and mRNA was increased. The results demonstrate that BaP may show toxic effect on the cervix by increasing DNA damage and the expression of the p53 gene.

Null genotypes of GSTM1 and GSTT1 contribute to risk of cervical neoplasia: an evidence-based meta-analysis

Background and Objectives

Glutathione S-transferases (GSTs) are multifunctional enzymes that play a key role in the detoxification of varieties of both endogenous products of oxidative stress and exogenous carcinogens.

Methods

In this meta-analysis, twenty-five studies were identified by searching PubMed, EMBASE, ISI Web of Science and CBM databases: 23 evaluated GSTM1 and 19 evaluated GSTT1. Crude odds ratios with corresponding 95% confidence intervals were used to estimate the association between GSTM1 and GSTT1 polymorphisms and risk of cervical neoplasia. Subgroup analyses were conducted by pathological history, ethnicity, source of DNA for genotyping, quality score, and matching variable.

Results

The null genotypes of GSTM1 and GSTT1 polymorphisms were associated with a significantly increased risk of cervical neoplasia (for GSTM1: OR = 1.40; 95%CI, 1.19–1.65; for GSTT1: OR = 1.30; 95%CI, 1.05–1.62, respectively). Subgroup analyses showed that the null genotype of GSTM1 increased the risk of cervical neoplasia in Asians, studies with DNA isolation from white blood cells and tissue samples, both high and low quality studies, and matched studies. In GSTM1-GSTT1 interaction analysis, individuals with dual null genotype were associated with a significantly increased risk of cervical neoplasia (OR = 1.72; 95%CI, 1.18–2.51).

Conclusion

These findings indicate that GSTM1 and GSTT1 polymorphisms, particularly GSTM1-GSTT1 interaction, may play critical roles in the development of cervical neoplasia. A conservative manner should be adopted to interpret these results because of obvious heterogeneity between-study, unadjusted data, and relatively small sample size in this meta-analysis. Well designed studies with larger sample size are of great value to confirm these results.

Germline polymorphism of cancer susceptibility genes in gynecologic cancer

The multifactorial process of carcinogenesis involves mutations in oncogenes, or tumor suppressor genes, as well as the influence of environmental etiological factors. Common DNA polymorphisms in low penetrance genes have emerged as genetic factors that seem to modulate an individual's susceptibility to malignancy. Genetic studies, which lead to a true association, are expected to increase understanding of the pathogenesis of each malignancy and to be a powerful tool for prevention and prognosis in the future. Here, we review the findings of genetic association studies of gene polymorphisms in gynecologic cancer with special reference to glutathione-S-transferase, FAS/CD95 and p53 genes including our recent research results.

GSTM1 and codon 72 P53 polymorphism in multiple myeloma

The GSTM1 and GSTT1 genes reduce the effects of exposure to cytotoxic agents. Both genes have a null variant allele in which the entire gene is absent. On the other hand, a common polymorphism of the tumour suppressor P53 gene results in either arginine (A) or proline (P) at amino-acid position 72. The A and P alleles code proteins with distinct functions in apoptosis and DNA repair and have been associated with variable risks for several cancers. However, their roles in multiple myeloma (MM) are still unknown. We tested in study whether the GSTM1, GSTT1 and P53 genotypes altered the risk for MM in Brazilian patients. Genomic DNA from 106 patients and 230 controls were analysed by polymerase chain reaction-based methods for identification of the genotypes. Similar frequencies of the GSTM1, GSTT1 and P53 genotypes were seen in patients and controls. Individuals with the distinct genotypes had similar risks for disease. In contrast, an excess of the GSTM1 null (45.1 vs 17.2%, P = 0.009), the P53 PP+AP (70.4 vs 44.8%, P = 0.041) and the GSTM1 null plus P53 PP+AP (29.6 vs 10.3%, P = 0.004) genotypes were seen in MM patients at stage III compared with those at stages I + II. Our data suggest that the GSTM1, GSTT1 and P53 genotypes do not influence the risk for MM. However, the inherited presence of the variant codon 72 P53 allele, described here for the first time, and the absence of the GSTM1 detoxification pathway, seem to act in disease progression in our country.

Molecular and genetic pathways in penile cancer

Penile cancer is a rare malignancy affecting more than 400 men per year in the UK. Studies on the aetiopathogenesis of this cancer have focused on its association with the human papilloma virus; however, there have also been several studies on the genetic and molecular changes that occur. Human papilloma virus has shown differential levels of prevalence in association with different types of penile cancer. The virus seems to act as a trigger for this disease via its oncogenes. We review this process, and assess the independent genetic events that occur in penile cancer. Knowledge of this cancer is progressing slowly and could be furthered by multicentre cooperation and the formation of national tumour banks, which will aid the development of novel therapeutic agents to reduce the morbidity and mortality of penile cancer.

Glutathione-S-transferase M1 polymorphisms on the susceptibility to esophageal cancer among three Chinese minorities: Kazakh, Tajik and Uygur

AIM: To investigate the glutathione-S-transferase M1 (GSTM1) polymorphisms in three Chinese minorities, Kazakh, Uygur, and Tajik; and the pathological significance of GSTM1 polymorphisms in esophageal carcinogenesis in Kazakh.

METHODS: A total of 1121 blood samples (442 males and 679 females) were obtained from healthy Kazakh (654), Uygur (412) and Tajik (55). Primary esophageal squamous cell cancer (ESCC) tissues from Kazakh were obtained from 116 patients who underwent surgery. GSTM1 polymorphisms were analyzed by a combined approach of PCR and electrophoresis techniques.

RESULTS: GSTM1 null genotype was found in 62.63% Uygur, 50.91% Tajik and 47.40% Kazakh. A significantly higher frequency of GSTM1 null genotype in Uygur was observed compared with Kazakh (OR: 1.859, 95% CI: 1.445 -2.391, χ² = 23.71, P = 0.000). In addition, GSTM1 null genotype was found in 23.53% of well-differentiated ESCC in Kazakh, in 49.23% of poorly differentiated ESCC, with a significant difference (OR: 3.152, 95% CI: 1.403-7.080, χ² = 8.018, P = 0.007).

CONCLUSION: There is a marked difference in the frequency of common GSTM1 null genotype between Uygur and Kazakh. GSTM1 null genotype is associated with differentiation of ESCC in Kazakh.

Exposure to wood smoke, HPV infection, and genetic susceptibility for cervical neoplasia among women in Colombia

Cervical cancer is the second leading cause of death from cancer among women in Colombia (16/100,000). Infection with high-risk human papillomavirus (HPV) plays a major role in the etiology of high-grade squamous intraepithelial lesions (HSILs). Exposure to chemical agents may be a cofactor for tumor induction, and individual genetic differences in the metabolism of these chemical agents may affect the susceptibility of individuals towards the development of HSIL. In this case-control study, a total of 91 cases with HSIL and 92 healthy controls, frequency-matched by age and place of origin, were recruited, and their frequencies of CYP2E1, GSTM1, and GSTT1 polymorphism were determined. We then evaluated the association of these polymorphisms, by themselves and in combination with wood smoke exposure and HPV-infection status, with the risk of HSIL. The results indicate that GSTM1 and GSTT1 polymorphism were not associated with HSIL, although a small increase in risk was observed for individuals who were GSTT1 null (OR = 1.4, 95% CI = 0.57-3.44). Contrary to other investigations, the c2/c2 variant of the CYP2E1 gene was associated with a significant increase in risk after adjusting for wood smoke exposure (OR = 6.3, 95% CI = 1.10-36.38) or wood smoke exposure and HPV-infection status (OR = 10.7, 95% CI = 1.76-65.58). Wood smoke exposure also increased the risk of HSIL among CYP2E1 c2/c2 HPV-positive women (OR = 3.3, CI = 0.50-22.50); however, the increase did not achieve statistical significance. Our study provides tantalizing evidence that genetic differences in the metabolism of wood smoke carcinogens, particularly metabolism by CYP2E1, may confer susceptibility for HSIL development. Further investigations with larger populations will be needed to confirm this association, which may provide important information for improving cervical cancer prevention programs.

Germline polymorphism of p53 codon 72 in gynecological cancer

OBJECTIVE

To investigate the biological significance of single nucleotide polymorphism at codon 72 of the p53 gene in the development of gynecological cancer.

METHODS

p53 codon 72 polymorphism was examined in a total of 354 blood samples from 95 normal, 83 cervical, 108 endometrial and 68 ovarian cancer cases using polymerase chain reaction and restriction fragment length polymorphism techniques.

RESULTS

When p53 codon 72 genotype was classified into two subgroups of Arg/Arg and Arg/Pro + Pro/Pro, the Arg/Arg genotype was associated with an increased risk for the development of endometrial cancer (OR = 1.86, 95% CI = 1.06 to 3.26) compared with the Arg/Pro + Pro/Pro genotype (P = 0.0301). The Arg allele also increased the risk of endometrial cancer (OR = 1.42, 95% CI = 0.93 to 1.52) compared with the Pro allele, but no statistical difference was found (P = 0.1031). There was no significant difference in the genotype or allele prevalence between control subjects and cervical or ovarian cancer patients.

CONCLUSION

Homozygous Arg at codon 72 of the p53 gene may be a risk factor for developing endometrial cancer in a Japanese population.

The p53 codon 72 polymorphism and risk of high-grade cervical intraepithelial neoplasia

BACKGROUND

The Arg/Arg genotype versus Arg/Pro or Pro/Pro at codon 72 of the p53 gene has been implicated in increasing susceptibility of the cervix to human papillomavirus (HPV) infection and thus altering cancer risk. However, research on this topic has been contentious, which prompted us to carry out a case-control study in the Montreal area.

METHODS

Cases were women with histologically-confirmed high-grade cervical intraepithelial neoplasia (HGCIN). Controls were women without a history of cervical abnormalities. From each woman, we obtained a cervical specimen for HPV testing and p53 genotyping, and a questionnaire was completed. DNA sequencing was used to minimize genotype misclassification. A subsample of specimens was also genotyped using the TaqMan assay.

RESULTS

There were 357 cases and 760 controls recruited between February 2001 and December 2003. The distribution of Arg/Arg, Arg/Pro and Pro/Pro was 55.2, 36.4 and 8.4%, respectively, among cases, and 52.1, 38.7 and 9.2%, among controls, corresponding to an odds ratio (OR) adjusted for ancestral origin of 1.16 (95% confidence interval (CI): 0.9-1.5) for Arg/Arg versus other genotypes. When restricted to high-risk HPV-positive women, the adjusted ORs were 1.40 (CI: 0.9-2.1) and 2.12 (CI: 1.1-4.2), for Arg/Arg versus other genotypes and versus Pro/Pro, respectively. The findings were comparable with analyses of genotype results that agreed between DNA sequencing and TaqMan.

CONCLUSIONS

In this study, we attempted to minimize selection bias, population stratification and genotype misclassification. The results suggest that the role of the p53 codon 72 polymorphism on HGCIN is weak at best. Further research may reveal if the polymorphism has a stronger influence on the risk of invasive cervical cancer.