p53 codon 72 polymorphism in vulval cancer and vulval intraepithelial neoplasia

Genetic Predisposition to Persistent Human Papillomavirus-Infection and Virus-Induced Cancers

Human papillomaviruses (HPVs) are the most common sexually transmitted pathogens worldwide and among the more than 200 identified HPV types, approximately 15 high risk (HR-HPV) types are oncogenic, being strongly associated with the development of cervical cancer, anogenital cancers and an increasing fraction of head and neck squamous cell carcinomas (HNSCC). HPV-associated cervix cancer accounts for 83% of HPV-attributable cancers, and more than two-thirds of those cases occur in developing countries. Despite the high frequency of HPV infections, in most cases, the virus is cleared by the host immune response and only a small proportion of infected individuals develop persistent infections that can result in malignant transformation, indicating that other elements, including biological, genetic and environmental factors may influence the individual susceptibility to HPV-associated cancers. Previous studies have quantified that heritability, in the form of genetic variants, common in the general population, is implicated in nearly 30% of cervical cancers and a large number of studies conducted across various populations have identified genetic variants that appear to be associated with genes that predispose or protect the host to HPV infections thereby affecting individual susceptibility to HPV-associated cancers. In this article, we provide an overview of gene association studies on HPV-associated cancers with emphasis on genome-wide association study (GWAS) that have identified novel genetic factors linked to HPV infection or HPV-associated cancers.

TP53 Mutations in Human Meningiomas

Overexpression of p53 has been reported to play a role in the development of neoplasms of the central nervous system. Meningiomas are generally benign intracranial tumors originating from the meninges. Overexpression of the p53 protein in meningiomas and an association with histological type and recurrence has been reported. Mutation of the TP53 gene leads to a more stable p53 protein in quantities high enough for detection by immunohistochemistry. In the search for these mutations the core domain of the TP53 gene of meningiomas has been analyzed. Only a very low incidence of mutations was reported. The apparent discordance between overexpression of p53 protein and TP53 gene mutations may be explained by mutations located outside the core domain. This issue was addressed in the present study. All 11 exons of 17 meningiomas were analyzed for DNA alterations by PCR single-strand conformation polymorphism (PCR-SS-CP) analysis with subsequent sequencing. PCR-SSCP analysis showed a various number of band shifts and nucleotide alterations, caused either by alterations in the flanking introns or common polymorphisms (codon 36 and 72). The allele frequencies of the polymorphisms found in this small population of tumors resemble the frequencies reported in the literature. In addition, three nucleotide changes located in introns 2, 3 and 7 were found in 11, 3 and 4, respectively, of 17 specimens. Based on this study and on reports by others we conclude that it is not very likely that TP53 mutations are involved in the etiology of meningiomas.

Does p53 codon 72 polymorphism have a prognostic value in carcinoma of the vulva and vagina?

Human papilloma virus (HPV) is considered to be responsible for a large part of vaginal and vulvar carcinomas, and the p53 codon 72 polymorphism has been implicated in susceptibility to cancer induced by this virus, but with contradicting results. In this study, we have investigated the prognostic value of the codon 72 polymorphism by real-time PCR (qPCR) in two cohorts of vaginal (n = 66) and vulvar (n = 123) carcinomas. In vaginal carcinoma, arginine homozygous patients were significantly associated with a higher primary cure rate (p = 0.023) but also associated with a higher recurrence rate (p = 0.073), significant at distant locations (p = 0.009). No significant differences were found in overall survival rate (p = 0.499) or cancer-specific survival rate (p = 0.222). A higher frequency of arginine homozygosity was noted in HPV-positive tumors (p = 0.190) in comparison with HPV-negative tumors. In vulvar carcinoma, the genotype homozygous for arginine was significantly associated with a larger tumor size at diagnosis in the entire cohort (p = 0.015) and a lower cancer-specific survival rate (p = 0.024) compared with heterozygous (arginine/proline) in HPV-negative tumors. Our results indicate that the relation between HPV and the p53 codon 72 polymorphism is complex and the significance and mechanisms responsible for this relationship need to be further elucidated.

Phenotypic features with p53 alterations related to human papillomavirus and prognostic evaluation in cervical cancer

Cervical cancer is one of the most common tumor affecting women worldwide. Human papillomavirus (HPV) was found to have a causal relationship with cervical cancer and its precursors. The interaction between HPV E6 protein and p53 was identified in in vitro studies. The aim of the study was to evaluate the prevalence of p53 alterations related to HPV infection and the prognostic significance of p53 alterations in cervical cancer. Studies were identified by a MEDLINE search, and all relevant articles were retrieved from 1991 to March 2004. The prevalence of p53 mutations is a rare event in cervical cancer. The correlation between p53 mutations and HPV or prognosis is controversial. Loss of heterozygosity (LOH) of p53 is more commonly found in cervical cancer and is related with the prognosis of this disease. There is no significant correlation between p53 polymorphism and development of cervical cancer. The p53 mutations were not commonly found in cervical cancer. LOH of p53 may contribute to the progression of this malignancy. p53 polymorphism failed to be an independent prognostic factor in predicting the outcome of patients with cervical cancer. Further, epidemiologic surveys should be undertaken in larger populations and in different geographical regions.

A polymorphism of the interleukin-1 receptor antagonist plays a prominent role within the interleukin-1 gene cluster in vulvar carcinogenesis

OBJECTIVE

The interleukin-1 (IL-1) family, that is, IL-1alpha and beta and the IL-1 receptor antagonist (IL-1RA), is known to modulate various tumorigenic and tumoricidal effects in humans. Its biological function in squamous cell carcinogenesis of various anatomical sites has been stressed. Although various studies showed a certain association between genes encoding the IL-1 family and human malignancies, no data with respect to vulvar cancer have been published to date.

METHODS

We ascertained four polymorphisms of the IL-1alpha gene (IL1A C[-889]T), the IL-1beta gene (IL1B promoter C[-511]T and IL1B exon 5 position +3953), and the IL-1RA gene (IL1RN intron 2) in 68 patients with surgically treated squamous cell vulvar cancer and 228 healthy Caucasian controls.

RESULTS

Presence of the minor allele of the IL1RN polymorphism was found to be protective for vulvar cancer [odds ratio (OR)=0.5, P=0.03], the other investigated polymorphisms showed no association with the disease and the investigated clinicopathological parameters. In a multivariate analysis, only the established prognosticators were associated with patients' survival.

CONCLUSION

We are the first to report on polymorphisms in genes encoding cytokines in patients with vulvar cancer. Reflecting its biological role, the common IL1RN intron 2 polymorphism seems to play a prominent role within the IL-1 gene cluster with respect to vulvar carcinogenesis.

Proline homozygosity in codon 72 of p53: a risk genotype for human papillomavirus related cervical cancer in Indian women

The objective of the present study was to determine the codon 72 genotypic frequencies of p53 in Indian women and to analyze the association of this polymorphism with human papillomavirus (HPV) related cervical cancer (CaCx). We used tissues derived from 55 women diagnosed with squamous cell carcinoma of the cervix (of whom 46 were HPV types 16/18 positive) and cervical scrapes derived from 201 cytologically normal women (of whom 84 were HPV types 16/18 positive) as controls. The DNA isolated from these samples was genotyped for p53 polymorphism by polymerase chain reaction and restriction fragment length polymorphism method. The genotypic frequency of homozygous arginine among women with CaCx was 27% and this did not differ with the controls. But, proline homozygosity of 33% in the malignant samples was significantly higher than controls (OR=2.23; 95% CI: 1.14-4.35; P=0.02). The associated risk of this genotype towards CaCx was more prominent (OR=2.67; 95% CI: 1.16-6.15; P=0.02) when analysis was restricted to HPV 16/18 positive women. Thus, proline homozygosity at codon 72 of p53 and not arginine homozygosity, could be a risk factor for development of CaCx associated with high risk HPV among Indian women.