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

Elevated serum expression of p53 and association of TP53 codon 72 polymorphisms with risk of cervical cancer in Bangladeshi women

Differential expression of p53 has been reported in cervical cancer, primarily in tumor tissue biopsies. In this study, we examined the association of TP53 codon 47 and codon 72 polymorphisms and serum level expression of p53 in cervical cancer patients (n = 129) and healthy controls (n = 122). We found elevated levels of serum p53 protein levels in cervical cancer patients (p = 0.0442) compared to healthy controls. Moreover, we found higher levels of serum p53 in patients with grade-III tumor (p = 0.001) compared to healthy controls. Examination of SNPs showed TP53 Arg/Pro heterozygosity (adjusted OR = 2.126, 95% CI = 1.181-3.827, p = 0.012), Pro/Pro mutant homozygosity (adjusted OR = 3.564, 95% CI = 1.647-7.713, p = 0.001), along with the combined genotype (Arg/Pro+Pro/Pro) (adjusted OR 2.542, 95% CI = 1.517-4.260, p<0.001) significantly increases the risk of cervical cancer. Expression quantitative trait analysis revealed no significant association with protein expression. Our results represent for the first time the upregulation of serum p53 in cervical cancer in Bangladeshi women and supports the association of TP53 codon 72 polymorphisms with cervical cancer.

Genetic Susceptibility for Cervical Cancer in African Populations: What Are the Host Genetic Drivers?

Human papillomavirus (HPV) is an essential but not a sufficient cervical cancer etiological factor. Cancer promoters, such as host genetic mutations, significantly modulate therapeutic responses and susceptibility. In cervical cancer, of interest have been viral clearing genes and HPV oncoprotein targets, for which conflicting data have been reported among different populations. This expert analysis evaluates cervical cancer genetic susceptibility biomarkers studied in African populations. Notably, the past decade has seen Africa as a hotbed of biomarker and precision medicine innovations, thus potentially informing worldwide biomarker development strategies. We conducted a critical literature search in PubMed/MEDLINE, Google Scholar, and Scopus databases for case-control studies reporting on cervical cancer genetic polymorphisms among Africans. We found that seven African countries conducted cervical cancer molecular epidemiology studies in one of Casp8, p53, CCR2, FASL, HLA, IL10, TGF-beta, and TNF-alpha genes. This analysis reveals a remarkable gap in cervical cancer molecular epidemiology among Africans, whereas cervical cancer continues to disproportionately have an impact on African populations. Genome-wide association, whole exome- and whole-genome sequencing studies confirmed the contribution of candidate genes in cervical cancer. With such advances and omics technologies, the role of genetic susceptibility biomarkers can be exploited to develop novel interventions to improve current screening, diagnostic and prognostic methods worldwide. Exploring these genetic variations is crucial because African populations are genetically diverse and some variants or their combined effects are yet to be discovered and translated into tangible clinical applications. Thus, translational medicine and flourishing system sciences in Africa warrant further emphasis in the coming decade.

Meta-Analysis of Polymorphic Variants Conferring Genetic Risk to Cervical Cancer in Indian Women Supports CYP1A1 as an Important Associated Locus

Objective: Association of multiple polymorphic variants with cervical cancer has been elucidated by several candidate gene based as well as genome-wide association studies. However, contradictory outcomes of those studies have failed to estimate the true effect of the polymorphic variants on cervical cancer. Methods: Literature mining of the PubMed database was done to gather all the publications related to genetic association with cervical cancer in India. Out of 98 PubMed hits only 29 genetic association studies were selected for meta-analysis based on specific inclusion criteria. A fixed-effect meta-analysis was performed to evaluate the overall association of the genetic polymorphisms with cervical cancer. Cochran’s Q test was performed to assess between study heterogeneity. Publication bias was also estimated by funnel plots and Egger’s regression test. Further, sub-group analysis was conducted by fixed-effect meta-regression to assess the impact of polymorphisms on cervical cancer in the presence of Human Papilloma Virus (HPV). Result: Following a fixed-effect model, meta-analysis was conducted that revealed 2 polymorphic variants viz. ‘deletion polymorphism (Del2) (OR=1.79, 95% CI= 1.08-2.95, P=0.023) in GSTM1’ and ‘rs1048943 (OR = 2.34, 95% CI=1.37-3.99, P=0.0018) in CYP1A1’ to be associated with cervical cancer. However, multiple testing correction showed only rs1048943 of CYP1A1 to be significantly associated (P-value=0.029) with cervical cancer with significant publication bias (P-value=0.0113) as estimated by Egger’s regression test. The polymorphic variants ‘rs1801131’, ‘rs1801133’, ‘rs2430561’, ‘rs1799782’, ‘rs25486’ and ‘rs25487’ showed significant (p<0.05) evidence of heterogeneity between studies by Cochran’s Q test and also by heterogeneity index (I2) calculation. Conclusion: Therefore, our study revealed significant association of rs1048943 in CYP1A1, but a nominal association of deletion polymorphism (Del2) in GSTM1 with cervical cancer, which provides a comprehensive insight on the true effect of the polymorphisms, reported in various case-control studies, on the risk of the development of cervical cancer in Indian women.

Effect of p53 codon 72 polymorphism on the survival outcome in advanced stage cervical cancer patients in India

Background & objectives:

The Arg>Pro polymorphism in codon 72 of p53 gene is known to affect the susceptibility of cervical cancer differently in different population worldwide although information regarding its role in determining survival status and disease outcome in patients is lacking. The present study was conducted to determine the genotype frequency and prognostic role of p53 codon 72 Arg>Pro polymorphism in patients with advanced stage cervical cancer in India.

Methods:

The p53 codon 72 polymorphism was determined in tumour biopsies (n = 107) and matched blood samples (n = 19) in cervical cancer patients using polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP). Effect of p53 genotype on the overall survival (OS) and recurrence-free survival (RFS) was analyzed. Individual Arg or Pro alleles were studied for their significance on survival as Pro carriers (Pro/Pro + Arg/Pro) versus Arg/Arg individuals or Arg carriers (Arg/Arg + Arg/Pro) versus Pro/Pro individuals.

Results:

The frequencies for Arg/Arg, Arg/Pro and Pro/Pro genotypes were 27.2, 49.5 and 23.3 per cent, respectively. There was no significant difference in the genotypes with respect to patients’ OS or RFS.

Interpretation & conclusions:

The findings of our study indicated that p53 codon 72 polymorphism might not be an independent marker in predicting clinical outcome in advanced stage cervical cancer patients. Further studies need to be done in larger samples to confirm these findings.

The preliminary study of p53 codon 72 polymorphism and risk of cervical carcinoma in Gabonese women

Cervical cancer is the leading cause of cancer-related death in Africa and the first most common cancer in Gabonese women due to infection of high-risk human papillomavirus (HPV). However, other cofactors such as genetic factors also come into play. A common polymorphism of the p53 codon 72 in exon 4 with two alleles encoding arginine or proline is known at this locus. The homozygous arginine form of this polymorphism has been associated with the development of cervical cancer as an increased genetic risk factor. However, the results are still controversial. This study aims to investigate whether the genotype distribution of p53 codon 72 may be a risk factor for cervical cancer among Gabonese women. Samples from 102 Gabonese women, 31 diagnosed with cervical cancer and 71 healthy controls, were used. HPV detection was done by nested PCR with MY09/11 and GP5+/6+ primers followed by sequencing for HPV genotyping. p53 codon 72 polymorphism determination was performed by allele-specific PCR assay. Viral DNA was detected in 87.1 % of cases and in 54.93 % of control. HPV 16 was the most predominant in cancer and controls cases. The distribution of Arg/Arg, Arg/Pro and Pro/Pro genotypes was 35.5, 51.6 and 12.9 % in the cervical cancer group and 22.5, 62 and 15.5 % in the control group. No significant association was found between polymorphism of p53 itself as well as in combination with HPV16/18 infection and risk of development of cervical cancer among Gabonese women. Thus, the polymorphism of p53 codon 72 in exon 4 does not seem to play a role in the development of cervical cancer among Gabonese women.

MTHFR/p53 Polymorphisms as Genetic Factors for Cervical Intraepithelial Neoplasia and Cervical Cancer in HPV-infected Mexican Women

We performed a case-control association study to evaluate the association between common polymorphisms in MTHFR (C677T and A1298C) and the Arg72Pro polymorphism in the p53 gene and the risk for cervical intraepithelial neoplasia (CIN) or invasive cervical cancer (ICC) in Mexican HPV-infected women. We included 131 women with diagnosis of CIN grade I-II and 78 with CIN III or ICC; as controls we also included 274 women with normal Pap smear and negative HPV test. Genotyping for MTHFR and p53 polymorphisms was performed by PCR-RFPLs. HPV was tested by Hybrid Capture II. Odds ratios and 95% confidence intervals were estimated. Genotype frequencies for the 3 studied polymorphisms were distributed according to the Hardy-Weinberg equilibrium. The A1298C-MTHFR polymorphism showed significant differences for the heterozygous AC genotype and the C allele, whereas the AA genotype and A allele resulted to be genetic risk factors for CIN or ICC (p<0.03). The Arg72Pro-p53 polymorphism showed for the genotypes Arg/Pro and Pro/Pro, and for the Pro allele, a significant association only to the risk for CIN (p<0.03). The MTHFR/p53 interaction showed that the genotype combinations AA/ArgArg and AA/ArgPro were associated, respectively, to the risk of ICC and CIN (p<0.05). This study suggests that the A1298C-MTHFR polymorphism contributes to the genetic risk for both CIN and ICC, whereas the Arg72Pro-p53 polymorphism only contributes to the risk for CIN. The MTHFR/p53 genetic combinations AA/ArgArg and AA/ArgPro are associated genetic risk factors for ICC and CIN in Mexican HPV-infected women.

cgaTOH: extended approach for identifying tracts of homozygosity

Identification of disease variants via homozygosity mapping and investigation of the effects of genome-wide homozygosity regions on traits of biomedical importance have been widely applied recently. Nonetheless, the existing methods and algorithms to identify long tracts of homozygosity (TOH) are not able to provide efficient and rigorous regions for further downstream association investigation. We expanded current methods to identify TOHs by defining "surrogate-TOH", a region covering a cluster of TOHs with specific characteristics. Our defined surrogate-TOH includes cTOH, viz a common TOH region where at least ten TOHs present; gTOH, whereby a group of highly overlapping TOHs share proximal boundaries; and aTOH, which are allelically-matched TOHs. Searching for gTOH and aTOH was based on a repeated binary spectral clustering algorithm, where a hierarchy of clusters is created and represented by a TOH cluster tree. Based on the proposed method of identifying different species of surrogate-TOH, our cgaTOH software was developed. The software provides an intuitive and interactive visualization tool for better investigation of the high-throughput output with special interactive navigation rings, which will find its applicability in both conventional association studies and more sophisticated downstream analyses. NCBI genome map viewer is incorporated into the system. Moreover, we discuss the choice of implementing appropriate empirical ranges of critical parameters by applying to disease models. This method identifies various patterned clusters of SNPs demonstrating extended homozygosity, thus one can observe different aspects of the multi-faceted characteristics of TOHs.

Integrative genomic analysis reveals extended germline homozygosity with lung cancer risk in the PLCO cohort

Susceptibility to common cancers is multigenic resulting from low-to-high penetrance predisposition-factors and environmental exposure. Genomic studies suggest germline homozygosity as a novel low-penetrance factor contributing to common cancers. We hypothesized that long homozygous regions (tracts-of-homozygosity [TOH]) harbor tobacco-dependent and independent lung-cancer predisposition (or protection) genes. We performed in silico genome-wide SNP-array-based analysis of lung-cancer patients of European-ancestry from the PLCO screening-trial cohort to identify TOH regions amongst 788 cancer-cases and 830 ancestry-matched controls. Association analyses was then performed between presence of lung cancer and common(c)TOHs (operationally defined as 10 or more subjects sharing ≥100 identical homozygous calls), aTOHs (allelically-matched groups within a cTOH), demographics and tobacco-exposure. Finally, integration of significant c/aTOH with transcriptome was performed to functionally-map lung-cancer risk-genes. After controlling for demographics and smoking, we identified 7 cTOHs and 5 aTOHs associated with lung cancer (adjusted p<0.01). Three cTOHs were over-represented in cases over controls (OR = 1.75–2.06, p = 0.007–0.001), whereas 4 were under-represented (OR = 0.28–0.69, p = 0.006–0.001). Interaction between smoking status and cTOH3/aTOH2 (2p16.3–2p16.1) was observed (adjusted p<0.03). The remaining significant aTOHs have ORs 0.23–0.50 (p = 0.004–0.006) and 2.95–3.97 (p = 0.008–0.001). After integrating significant cTOH/aTOHs with publicly-available lung-cancer transcriptome datasets followed by filtering based on lung cancer and its relevant pathways revealed 9 putative predisposing genes (p<0.0001). In conclusion, differentially-distributed cTOH/aTOH genomic variants between cases and controls harbor sets of plausible differentially-expressed genes accounting for the complexity of lung-cancer predisposition.

Common genetic variation in TP53 and risk of human papillomavirus persistence and progression to CIN3/cancer revisited

Driven by findings that human papillomavirus (HPV)-induced degradation of p53 differs by a TP53 polymorphism at codon 72 (Pro72Arg), past studies of TP53 genetic variants and cervical cancer have focused on this nonsynonymous polymorphism, with mixed results. We analyzed common single nucleotide polymorphisms (SNP) across the TP53 locus in a population-based nested case-control study in Guanacaste, Costa Rica. We evaluated 11 SNPs, including Pro72Arg (rs1042522), among 1,281 women: 465 with cervical intraepithelial neoplasia grade 3/cancer (CIN3+), 380 with HPV persistence (median, 25 months), and 436 random population controls. We combined HPV persistence and CIN3+ into one case group because they did not differ in TP53 genotypic frequencies and calculated odds ratios and 95% confidence intervals (CI) for individual SNPs and inferred haplotypes. We observed that proline at codon 72 was associated with increased risk of CIN3+/persistence compared with population controls. Relative to GG (Arg), the CG (Pro/Arg) and CC (Pro) genotypes had a 1.3-fold (95% CI, 0.99-1.6) and 1.8-fold (95% CI, 1.2-2.7) increased risk, respectively (P(trend) < 0.01). rs12951053 and rs1642785 were also associated with CIN3+/persistence (P (trend), 0.05 and 0.04, respectively), as was a haplotype containing the codon 72 variant (rs1042522), rs12951053, rs1642785, and rs12947788 (odds ratio, 1.6; 95% CI, 1.1-2.3 versus the most common haplotype, which comprised the major alleles for all 11 SNPs). Although genetic variation in TP53 might affect the natural history of HPV and cervical cancer, further work is needed to elucidate the possible mechanism.

Age-specific prevalence of infection with human papillomavirus in females: a global review

PURPOSE

Global data on age-specific prevalence of human papillomavirus (HPV) infection overall, and for high-risk HPV types 16 and 18, are essential for the future implementation of HPV prophylactic vaccines for cervical cancer prevention.

METHODS

A systematic review of peer-reviewed publications was conducted to summarize worldwide data on genital HPV-DNA prevalence in women. Studies with clear descriptions of polymerase chain reaction or hybrid capture detection assays were included.

RESULTS

A total of 346,160 women were included in 375 studies. Of 134 studies with age-stratified HPV prevalence data (116 low sexual risk populations, 18 high sexual risk populations), over 50% were from Europe and the Middle East (38%) and North America (19%), with smaller proportions from Asia and Australia (21%), Central and South America (11%), and Africa (10%). Across all geographical regions, data on HPV prevalence were generally limited to women over 18 years of age. Consistently across studies, HPV infection prevalence decreased with increasing age from a peak prevalence in younger women (< or =25 years of age). In middle-aged women (35-50 years), maximum HPV prevalence differed across geographical regions: Africa (approximately 20%), Asia/Australia (approximately 15%), Central and South America (approximately 20%), North America (approximately 20%), Southern Europe/Middle East (approximately 15%), and Northern Europe (approximately 15%). Inconsistent trends in HPV prevalence by age were noted in older women, with a decrease or plateau of HPV prevalence in older ages in most studies, whereas others showed an increase of HPV prevalence in older ages. Similar trends of HPV 16 and/or 18 prevalence by age were noted among 12 populations with available data.

DISCUSSION

Genital HPV infection in women is predominantly acquired in adolescence, and peak prevalence in middle-aged women appears to differ across geographical regions. Worldwide variations in HPV prevalence across age appear to largely reflect differences in sexual behavior across geographical regions. Further studies of HPV prevalence in adolescents are needed for all geographic regions.

Combined effects of the p53 codon 72 and p73 G4C14-to-A4T14 polymorphisms on the risk of HPV16-associated oral cancer in never-smokers

Because p53 and p73 are associated with critical cellular processes and can be inactivated or degraded by the human papillomavirus (HPV) E6 oncoprotein, we investigated the combined effects of p53 codon 72 and p73 G4C14-to-A4T14 polymorphisms on the risk of HPV16-associated oral cancer. We analyzed genotype data from 326 patients with squamous cell carcinoma of the oral cavity or oropharynx and 349 cancer-free controls. We found that HPV16 seropositivity was associated with an increased risk of oral cancer [adjusted odds ratio (OR), 3.42; 95% confidence interval (CI), 2.28-5.13], especially among never-smokers (adjusted OR, 8.20; 95% CI, 3.66-18.4) and subjects with variant genotypes [adjusted OR for p53 Arg/Pro + Pro/Pro (Pro carriers), 5.00; 95% CI, 2.72-9.21; adjusted OR for p73 GC/AT + AT/AT (AT carriers), 3.83; 95% CI, 1.98-7.41]. HPV16 seropositivity was also associated with an significantly increased risk of oral cancer in all three risk groups with combined genotypes [adjusted ORs (95% CIs) were 2.28 (1.15-4.54) for p53 Arg/Arg and p73 GC/GC, the low-risk group; 3.97 (2.14-7.36) for p53 Arg/Arg and p73 AT carriers or p53 Pro carriers and p73 GC/GC, the medium-risk group and 5.11 (2.00-13.0) for p53 Pro carriers and p73 AT carriers, the high-risk group]. Moreover, HPV16-seropositive never-smokers in the high-risk group exhibited an approximately 11-fold greater risk of oral cancer (adjusted OR, 11.3; 95% CI, 1.22-106.0) than did HPV16-seronegative never-smokers in the low-risk group. These findings suggest that the combined variants of p53 and p73 significantly increase the risk of HPV16-associated oral cancer, especially among never-smokers.

p53 codon 72 polymorphism associated with risk of human papillomavirus-associated squamous cell carcinoma of the oropharynx in never-smokers

The tumor suppressor p53 protein can be bound, degraded and inactivated by the human papillomavirus (HPV) E6 oncoprotein. The p53 protein's susceptibility to this oncoprotein may be influenced by the p53 codon 72 polymorphism, but the role of such a polymorphism in the development of HPV16-associated squamous cell carcinoma of the oropharynx (SCCOP) has not been established. To investigate the role of the p53 codon 72 polymorphism in the risk of HPV16-associated SCCOP, we conducted a hospital-based case-control study of 188 non-Hispanic white patients with newly diagnosed SCCOP and 342 cancer-free control subjects frequency matched by age (+/-5 years), sex, tobacco smoking status and alcohol drinking status. We found that HPV16 seropositivity was associated with an increased risk of SCCOP [adjusted odds ratio (OR), 5.7; 95% confidence interval (CI), 3.7-8.7], especially among never-smokers (adjusted OR, 14.1; 95% CI, 6.0-32.9) and among subjects with the p53 codon 72 variant genotypes [Arginine (Arg)/Proline (Pro) and Pro/Pro] (adjusted OR, 9.2; 95% CI, 4.7-17.7). A significant multiplicative interaction on the risk of SCCOP was also found between the p53 codon 72 polymorphism and HPV16 seropositivity (P = 0.05). Among never-smokers, the risk of SCCOP for those who had both HPV16 seropositivity and p53 codon 72 variant genotypes (Arg/Pro + Pro/Pro) was particularly high (adjusted OR, 22.5; 95% CI, 4.8-106.2). These findings suggest that p53 codon 72 variant genotypes modify the risk of HPV16-associated SCCOP and may be markers of genetic susceptibility to HPV16-associated SCCOP, especially among never-smokers.

Predisposition to HPV16/18-related cervical cancer because of proline homozygosity at codon 72 of p53 among Indian women is influenced by HLA-B*07 and homozygosity of HLA-DQB1*03

This study was undertaken to examine whether predisposition to human papillomavirus (HPV)16/18-related cervical cancer (CaCx) because of p53 proline homozygosity (Pro72Pro) among Indian women was mediated singly or jointly with immunogenetic risk factors such as HLA-B*07 or homozygosity of HLA-DQB1*03. Molecular detection of all three genetic factors was performed by polymerase chain reaction-restriction fragment length polymorphism using DNA from (i) 114 CaCx samples (78 HPV16/18 positive) and (ii) 195 cytologically normal cervical scrapes (116 HPV-negative and 79 HPV16/18-positive samples). Multiple logistic regression analyses were performed to examine independent effects of the three factors and to determine age-adjusted odds ratio (OR) [95% confidence interval (CI)] and P-values. HLA-B*07 was observed to be significantly associated with HPV16/18 infection in asymptomatic controls (OR(age-adjusted) = 4.73; 95% CI: 1.55-14.45; P = 0.006) and CaCx (OR(age-adjusted) = 6.14; 95% CI: 2.15-17.53; P < 0.001) in this enhanced sample set of CaCx cases. There was a lack of association between HLA-B*07 and HLA-DQB1*03 in our study samples. The association of p53Pro72Pro with CaCx was non-significant in the absence of HLA-B*07 in HPV16/18-positive women. In this group, prevalence of p53Pro72Pro and HLA-B*07 together was significantly higher (7.0%) among CaCx cases (OR(age-adjusted) = 14.05; 95% CI: 1.11-177.30; P = 0.04), compared with controls (1.3%) lacking both factors. HLA-DQB1*03 homozygosity (OR(age-adjusted) = 4.75; 95% CI: 1.17-19.30; P = 0.03) or p53Pro72Pro (OR(age-adjusted) = 5.84; 95% CI: 1.18-28.99; P = 0.03) was found to be significantly associated with CaCx, each in the absence of the other in this group but not when present jointly in contrast to those lacking both factors (P = 0.214). Thus, modulation of p53Pro72Pro-mediated susceptibility to CaCx by immunogenetic factors could possibly be mediated through cross talk between HPV16/18-induced immune evasion and cell transformation.

No relationship observed between human p53 codon-72 genotype and HPV-associated cervical cancer in a population group with a low arginine-72 allele frequency

Infection with high-risk human papillomavirus (HR-HPV) is a necessary but not a sufficient event in the development of cervical cancer, as most infections regress without intervention. Thus, genetic host factors and cellular immune responses could be potential modifiers for the risk of developing cervical cancer. In particular, p53 is considered as the most critical tumour suppressor gene and is involved in regulating cell division. The polymorphism on p53, which encodes either a proline or an arginine amino acid residue at codon 72, has been reported as a possible risk factor for cervical disease. This polymorphism has been shown to differentially affect the efficiency of degradation of p53 protein mediated by HR-HPV E6 oncoprotein. Women with histologically proven cancer of the cervix (n = 111) and hospital-based controls (n = 143) were included in this study. The patients and controls were from the Western Cape Province in South Africa. Genotyping of the p53 polymorphism was conducted using polymerase chain reaction and restriction fragment-length polymorphism method. The distributions of the allelic frequencies were stratified in both patients and controls into two South African ethnic population groups. In this study, we observed no association between the distribution of p53 polymorphism and susceptibility to cervical cancer in the Western Cape Province populations (P = 0.466). However, the frequency of the Pro/Pro residue at codon 72 was increased in the South African population when compared to Caucasians, Indians and Portuguese population groups. Notably, as the distribution of the Pro/Pro at codon 72 of p53 gene was significantly different (P < 0.05) between the control groups of South Africa and other population groups. This result suggests that ethnic disparity may influence the levels of p53 produced.

Lack of evidence that proline homozygosity at codon 72 of p53 and rare arginine allele at codon 31 of p21, jointly mediate cervical cancer susceptibility among Indian women

OBJECTIVES

The objective of this study was to identify whether variants of p53Arg72Pro and p21Ser31Arg were associated with increased risk for cervical cancer (CaCx), either independently or jointly, among Indian women.

METHODS

Genotyping was done by PCR-RFLP using DNA from (i) 120 cervical biopsy tissues of squamous cell carcinoma of the cervix (of which 82 were HPV16/18 positive), and (ii) a total of 205 cytologically normal cervical scrapes (121 HPV-negative and 84 HPV16/18-positive samples, considered as discreet groups). Multiple logistic regression analyses were performed to examine additive or interactive effects of the two factors and for determining age-adjusted OR (95% CI) and P values.

RESULTS

The observed association of proline homozygosity at codon 72 of p53 with CaCx infection (Bhattacharya, P., Duttagupta, C., Sengupta, S. 2002.Proline homozygosity in codon 72 of p53: A risk genotype for Human Papillomavirus related cervical cancer in Indian women. Cancer Lett 188: 207-211) was retained among Indian women harboring HPV16/18 (OR(age-adjusted) = 3.76; 95% CI = 1.03-13.80; P = 0.04). Significant independent association was evident between the p21 arginine allele (rare allele with frequency of 0.1) at codon 31 and CaCx, compared to HPV-negative cytologically normal controls (OR(age-adjusted) = 2.01; 95% CI = 1.00-4.06; P = 0.05). The two risk factors jointly failed to show statistical interaction towards susceptibility to CaCx. The p21 arginine allele was significantly associated with CaCx in the p53 proline non-homozygous group of subjects (OR(age-adjusted) = 2.68; 95% CI: 1.21-5.91; P = 0.01), and specifically in the p53 heterozygous group (OR(age-adjusted) = 2.91; 95% CI = 1.12-7.56; P = 0.03).

CONCLUSIONS

p53 and p21 act in series in mediating cell cycle arrest. However, the two risk factors, p53 proline homozygosity and p21 arginine allele, although part of a common causal pathway, appear to act in a mutually exclusive manner.

Association of specific genotype and haplotype of p53 gene with cervical cancer in India

BACKGROUND

The predictive value of codon 72 arginine homozygosity at the p53 gene for human papilloma virus associated cervical cancer risk remains inconclusive. It has also been proposed that the inheritance of specific germline haplotypes based on three biallelic polymorphisms of p53 (intron 3 16 bp duplication, codon 72 Bst UI (Arg/Pro), and intron 6 Nci I restriction fragment length polymorphism at nucleotide 13494) is a better predictor of various cancer risks.

AIMS

To determine the genotype and haplotype frequency of these three p53 polymorphisms in 61 patients with cervical squamous cell carcinoma and 94 ethnically matched controls from the eastern region of India and estimate the risk, if any, of specific genotypes and haplotypes.

METHODS

Samples were genotyped by polymerase chain reaction followed by variant specific restriction enzyme digestion. Haplotypes were estimated by the maximum likelihood method using the expectation maximisation algorithm.

RESULTS

Genotype distributions of the three polymorphisms in patients and controls showed a good fit to the Hardy-Weinberg equilibrium. The p53 codon 72 arginine homozygous genotype was significantly over represented in patients compared with controls. Those with the homozygous arginine genotype exhibited a 2.59 fold higher risk of developing squamous cell carcinoma of the uterine cervix. A significant risk was also seen with a combination of two haplotypes, 1-2-1 and 1-2-2.

CONCLUSION

p53 codon 72 arginine homozygotes appear to be at greater risk of developing squamous cell carcinoma of the uterine cervix. The high risk haplotypes 1-2-1 and 1-2-2 also contain the arginine allele, further strengthening this conclusion.

p53 Codon 72 Polymorphism and Cervical Neoplasia: A Meta-Analysis Review

The Arg/Arg genotype versus Arg/Pro or Pro/Pro at codon 72 of the p53 gene has been implicated as a risk marker in cervical neoplasia. However, research on this topic has produced controversial results. We reviewed the published literature to summarize the association and to identify methodological features that may have contributed to the heterogeneity. Information on specific methodological features of studies addressing this topic published between 1998 and 2002 were obtained. Study-specific odds ratios (ORs) were combined in a meta-analysis, assuming random effects. To identify characteristics that significantly contributed to heterogeneity, we used meta-regression analysis. We identified 50 articles, of which 45 were included in the meta-analyses and regressions. No evidence of association or heterogeneity was detected for preinvasive lesions. For invasive cervical cancer with undefined histology, the Arg/Arg genotype was not found to affect risk (OR, 1.1; 95% confidence interval (CI), 0.9-1.3). However, a slightly increased risk was observed for squamous cell carcinoma (OR, 1.5; 95% CI, 1.2-1.9) and adenocarcinoma (OR, 1.7; 95% CI, 1.0-2.7). Meta-regression analysis identified that the most important factor contributing to heterogeneity among results for invasive lesions was departures from Hardy-Weinberg equilibrium in the control group. Summary ORs for studies in equilibrium were essentially null. A possible susceptibility role by the p53 codon 72 polymorphism at a late carcinogenetic stage in cervical cancer cannot be ruled out. However, various methodological features can contribute to departures from Hardy-Weinberg equilibrium and consequently to less than ideal circumstances for the examination of this polymorphism. Future investigations require appropriate attention to design and methodological issues.

Polymorphism p53 codon-72 and invasive cervical cancer: a meta-analysis

OBJECTIVES

Although some studies have reported that the arginine isoform on codon 72 of p53 increases the susceptibility to invasive cervical cancer, such data remain controversial. The objective of this study was to quantitatively summarize the evidence for such a relationship.

METHODS

Our data sources consisted of a MEDLINE search of the literature published before December 2002, bibliography review, and expert consultation. Thirty-seven studies met the inclusion criteria. Information on sample size, study design, Hardy-Weinberg equilibrium, and method of genotype determination was abstracted by two reviewers using a standardized protocol. The overall odds ratio (OR) of the p53 gene on invasive cervical cancer was estimated using the Mantel-Haenzel method.

RESULTS

The overall OR (95% confidence interval) for cervical cancer among those with the homozygous mutant (Arg/Arg) was 1.2 (1.1-1.3, P=0.001) compared with those with the heterozygous mutant (Arg/Pro). By a cellular type of cervical cancer, the overall OR among those with Arg/Arg was statistically significant in adenocarcinomas (1.7, 1.1-2.6, P=0.024), but not in squamous cell carcinomas (1.1, 0.9-1.2, P=0.960), compared with Pro/Pro. Compared with Arg/Pro, the OR among those with Arg/Arg was statistically significant in HPV types 16 (1,5, 1.2-2.0, P=0.002).

CONCLUSIONS

Overall, the p53 gene was associated with increased risk for invasive cervical cancer. However, the risk varied by country, cellular, and HPV type.

Ethnic differences in allelic distribution of IFN-g in South African women but no link with cervical cancer

BACKGROUND: The failure of specific types of human papillomaviruses (HPV) to raise effective immune responses may be important in the pathogenesis of cervical cancer, the second most common cancer in South African women. Polymorphisms of a number of cytokine genes have been implicated in inducing susceptibility or resistance to cancers caused by infectious agents owing to their role in determining host immune response. Polymorphisms of IL-10 and IFN-gamma genes are believed to influence the expression and/or secretion levels of their respective cytokines. METHODS AND RESULTS: In this study, women with histologically proven cancer of the cervix (n = 458) and hospital-based controls (n = 587) were investigated for bi-allelic -1082 (A/G) polymorphisms of IL-10 and the bi-allelic +874(A/T) polymorphisms of IFN-gamma. In addition, the distributions of the allelic frequencies were stratified in both the African and mixed race population groups of South Africa. We found striking differences in the allele distribution of IFN-gamma (X2 = 0.02) among the two ethnic groups. A significant increase in the allele distribution of the IFN-gamma AA genotype was found in the African group compared to the mixed population group (OR, 0.5; 95% CI, 0.2-1.0). For IL-10 there were no significant allelic differences between the two South African ethnic groups. Furthermore, when the ethnic groups were combined the IL-10 allelic frequencies in the combined South African data were similar to those observed in an Oriental population from Southern China and in an Italian population. However, the allele frequencies of the IFN-gamma genotype among the two South African ethnic groups were different when compared to an Italian Caucasoid group. While crude analysis of these data showed both statistically significantly increased and diminished risks of cervical cancer among high producers of INF-gamma and low producers of IL-10 respectively, these associations were no longer significant when the data were adjusted for confounding factors. CONCLUSION: These findings demonstrate a clear correlation between ethnicity and IFN-gamma polymorphism across different population groups. However, these differences in ethnicity and gene polymorphisms in the aforementioned cytokines are suggested not to influence the development of invasive cervical cancer but may represent an important susceptibility biomarker for other diseases and should be explored further.