Two germ line polymorphisms of the tumour suppressor gene p53 may influence the biology of chronic lymphocytic leukaemia

Validation of single nucleotide polymorphisms potentially related to R-CHOP resistance in diffuse large B-cell lymphoma patients

Aim: Diffuse large B-cell lymphoma (DLBCL) is the most common B-cell non-Hodgkin lymphoma (NHL). Despite the availability of clinical and molecular algorithms applied for the prediction of prognosis, in up to 30%-40% of patients, intrinsic or acquired drug resistance occurs. Constitutional genetics may help to predict R-CHOP resistance. This study aimed to validate previously identified single nucleotide polymorphisms (SNPs) in the literature as potential predictors of R-CHOP resistance in DLBCL patients, SNPs. Methods: Twenty SNPs, involved in R-CHOP pharmacokinetics/pharmacodynamics or other pathobiological processes, were investigated in 185 stage I-IV DLBCL patients included in a multi-institution pharmacogenetic study to validate their previously identified correlations with resistance to R-CHOP. Results: Correlations between rs2010963 (VEGFA gene) and sex (P = 0.046), and rs1625895 (TP53 gene) and stage (P = 0.003) were shown. After multivariate analyses, a concordant effect (i.e., increased risk of disease progression and death) was observed for rs1883112 (NCF4 gene) and rs1800871 (IL10 gene). When patients were grouped according to the revised International Prognostic Index (R-IPI), both these SNPs further discriminated progression-free survival (PFS) and overall survival (OS) of the R-IPI-1-2 subgroup. Overall, patients harboring the rare allele showed shorter PFS and OS compared with wild-type patients. Conclusions: Two out of the 20 study SNPs were validated. Thus, these results support the role of previously identified rs1883112 and rs1800871 in predicting DLBCL resistance to R-CHOP and highlight their ability to further discriminate the prognosis of R-IPI-1-2 patients. These data point to the need to also focus on host genetics for a more comprehensive assessment of DLBCL patient outcomes in future prospective trials.

Genetic variability profiling of the p53 signaling pathway in chronic lymphocytic leukemia. Individual and combined analysis of TP53, MDM2 and NQO1 gene variants

TP53 gene disruption, including 17p13 deletion [del(17p)] and/or TP53 mutations, is a negative prognostic biomarker in chronic lymphocytic leukemia (CLL) associated with disease progression, treatment failure and shorter survival. Germline variants in p53 signaling pathway genes could also lead to p53 dysfunction, but their involvement in CLL has not been thoroughly evaluated. The aim of this study was to determine the association of TP53, MDM2 and NQO1 gene variability with clinical and genetic data of CLL patients. Individual genotype and haplotype data of CLL patients were compared with clinical prognostic factors, cytogenetic and molecular cytogenetic findings as well as IGHV and TP53 mutational status. The study included 116 CLL patients and 161 healthy blood donors. TP53 (rs1042522, rs59758982, rs1625895), NQO1 (rs1800566) and MDM2 (rs2279744, rs150550023) variants were genotyped using different PCR approaches. Analysis of genotype frequencies revealed no association with the risk of CLL. TP53 rs1042522, rs1625895 and MDM2 rs2279744 variants were significantly associated with abnormal karyotype and the presence of del(17p). Similarly, these two TP53 variants were associated with TP53 disruption. Moreover, TP53 C-A-nondel and G-A-del haplotypes (rs1042522-rs1625895-rs59758982) were associated with an increased likelihood of carrying del(17p) and TP53 disruptions. MDM2 T-nondel haplotype (rs2279744-rs150550023) was found to be a low risk factor for del(17p) (OR = 0.32; CI: 0.12-0.82; p = 0.02) and TP53 disruptions (OR = 0.41; CI: 0.18-0.95; p = 0.04). Our findings suggest that TP53 and MDM2 variants may modulate the risk to have chromosome alterations and TP53 disruptions, particularly del(17p). To our knowledge this is the first study of several germline variants in p53 pathway genes in Argentine patients with CLL.

TP53 Gene 72 Arg/Pro (rs1042522) single nucleotide polymorphism increases the risk and the severity of chronic lymphocytic leukemia

Background

Genetic variations in TP53 gene are known to be important in chronic lymphocytic leukemia (CLL) and may cause its inactivation which is associated with an aggressive form of the disease. Single nucleotide polymorphism (rs1042522:G>C) in TP53 gene at codon 72 encodes for arginine (Arg) or proline (Pro) variant which results in amino acid substitution affecting the apoptotic potential of TP53 protein. The aim of this study was to assess the correlation between TP53 codon 72 polymorphism and risk susceptibility as well as severity of CLL among Tunisian patients.

Materials and methods

A case-control study was conducted in Tunisia from February 2019 to November 2021, 160 de novo CLL patients and 160 healthy volunteers matched in age and gender were involved. DNA was extracted from peripheral blood mononuclear cells and the rs1042522 was analyzed using PCR-RFLP.

Results

Pro variant was associated with higher susceptibility to CLL than Arg variant (p= 0.023). A significant association was found between Pro variant and prognostic classification of Binet stage C (p= 0.001), low hemoglobin level (p= 0.003) and low platelet count (p= 0.016).

Conclusion

We suggest that Pro variant may increase the risk of developing CLL in our population and could be associated with the severity of the disease.

The relationship between leukemia and TP53 gene codon Arg72Pro polymorphism: analysis in a multi-ethnic population

Aim: Many studies have analyzed the relationship between Arg72Pro polymorphism of TP53 and leukemia; nevertheless, the findings continue to be indeterminate. We, therefore, performed an updated meta-analysis in multi-ethnic groups using specialized software for genome-wide association studies meta-analysis. Materials & methods: PubMed, EMBASE and Google Scholar were searched up to October 2018. An odds ratio (OR) with the corresponding 95% CI was used to evaluate the strength in the association. Results: This meta-analysis included 16 studies with 2337 cases and 9494 controls. In the overall population, significant relationship between Arg72Pro polymorphism of TP53 and leukemia susceptibility was found in two genetic models (recessive model: OR = 1.276, 95% CI = 1.102-1.476; p = 0.01; overdominant model: OR = 0.891, 95% CI = 0.802-0.988; p = 0.03). In stratified studies with ethnicity, a significant association was found in five ethnic groups, including Chinese, Americans, Africans, Japanese and Indians. Conclusion: We demonstrated that an association exist between leukemia risk and TP53 gene codon Arg72Pro polymorphism in the recessive and overdominant genetic models. Also, our findings show that the TP53 Arg72Pro polymorphism may influence leukemia development in different populations.

TP53 Gene 72 Arg/Pro (rs1042522) Single Nucleotide Polymorphism Contribute to Increase the Risk of B-Chronic Lymphocytic Leukemia in the Sudanese Population

Objective::

This study aimed at exploring the association of TP53 72Arg/Pro polymorphism and Risk of Chronic Lymphocytic Leukemia and to assess the correlation between TP53 72Arg/Pro polymorphism and clinical parameter, hematological profile and some biological prognostic markers among Sudanese patients with chronic lymphocytic leukemia.

Methods:

A case-control study was conducted in Khartoum state, Sudan, during the period from April 2017 to April 2018, involved 110 B-CLL patients and 80 healthy volunteers as a control group. Physical examination, Complete Blood Count and Immunophenotype were performed in all patients to confirm the diagnosis. Clinical staging such as Rai and Binet were studied. CD38 and ZAP70 were performed by Flow Cytometry. Blood samples were collected from all participants; DNA was extracted by using ANALYTIKJENA Blood DNA Extraction Kit (Germany) and analyzed TP53 codon 72Arg/Pro Polymorphism by using AS-PCR. The statistical analysis was performed using SPSS version 23.0 software (Chicago, IL, USA).

Results:

the Arg/Pro was the most frequent genotype in B-CLL patients(50%), followed by Arg/Arg (25.5%) and Pro/Pro (24.5%), whereas in healthy control group Arg/Pro was the most frequent (47.5%), followed by Arg/Arg (45%) and Pro/Pro (7.5%). Our data indicate a higher frequency of homozygous Pro/Pro in the B-CLL patients as compared to controls with an OR of 4.01 for the Pro/Pro genotype and lower frequency of Arg/Arg genotype in CLL patients as compared to controls with an OR of .42 for the Arg/Arg genotype. Also, the Pro allele showed higher risk than Arg allele (P value=0.000, OR 2.23, 95% CI=1.45-3.41). No significant association between gender, clinical staging systems (Rai, Binet), biological prognostic markers (CD38 expression or ZAP70 expression), and TP53 codon 72Arg/Pro polymorphisms, except Arg/Arg genotype tended to be associated with younger age (P =0.04).

Conclusion:

Our data suggested that Pro/Pro genotype contribute to increased susceptibility to B-Chronic Lymphocytic Leukemia risk in our population tenfold higher than those had Arg/Arg genotype.

ERIC recommendations for TP53 mutation analysis in chronic lymphocytic leukemia-update on methodological approaches and results interpretation

In chronic lymphocytic leukemia (CLL), TP53 gene defects, due to deletion of the 17p13 locus and/or mutation(s) within the TP53 gene, are associated with resistance to chemoimmunotherapy and a particularly dismal clinical outcome. On these grounds, analysis of TP53 aberrations has been incorporated into routine clinical diagnostics to improve patient stratification and optimize therapeutic decisions. The predictive implications of TP53 aberrations have increasing significance in the era of novel targeted therapies, i.e., inhibitors of B-cell receptor (BcR) signaling and anti-apoptotic BCL2 family members, owing to their efficacy in patients with TP53 defects. In this report, the TP53 Network of the European Research Initiative on Chronic Lymphocytic Leukemia (ERIC) presents updated recommendations on the methodological approaches for TP53 mutation analysis. Moreover, it provides guidance to ensure that the analysis is performed in a timely manner for all patients requiring treatment and that the data is interpreted and reported in a consistent, standardized, and accurate way. Since next-generation sequencing technologies are gaining prominence within diagnostic laboratories, this report also offers advice and recommendations for the interpretation of TP53 mutation data generated by this methodology.

TP53 codon 72 polymorphism and breast cancer risk in Bangladeshi population

BACKGROUND

Breast cancer, a hereditary or heterogeneous sporadic disease, is the most common cancer in women worldwide. The tumor suppressor TP53 gene has been found to be the most commonly mutated genes in many types of human cancers, including breast cancer. This study aimed to investigate the association of codon 72 polymorphism of TP53 gene with breast cancer risk in Bangladeshi females.

METHODS

The study included 125 cases and 125 healthy controls. Genotyping and polymorphism were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

The frequencies of the three genotypes Arg/Arg, Arg/Pro, and Pro/Pro were 43.2, 33.6, and 23.2% in cases, whereas 48.8, 40.8, and 10.4% in controls, respectively. The frequency of mutant homozygous (Pro/Pro) genotype was significantly increased in breast cancer patients as compared with controls (23.2 vs 10.4%), and showed 2.52-fold significantly increased risk for breast cancer (OR 2.5199, 95% CI 1.19-5.33, p = 0.0157). The frequencies of Pro/Pro genotype were significantly higher in breast cancer cases with non-breast feeding status. Pro allele frequency was found to be significantly increased in breast cancer cases (OR 1.4978, 95% CI 1.0357-2.1662, p = 0.0318).

CONCLUSIONS

Our data suggest that mutant (Pro/Pro) homozygosity at codon 72 of TP53 gene is significantly associated with breast cancer susceptibility in Bangladeshi women. In addition, this association was significantly related to lactating status.

Association between TP53 Arg72Pro polymorphism and leukemia risk: a meta-analysis of 14 case-control studies

The relationship between the TP53 Arg72Pro polymorphism (rs1042522) and the risk of leukemia remains controversial. Consequently, we performed a meta-analysis to accurately evaluate the association between TP53 Arg72Pro polymorphism and leukemia risk. A comprehensive search was conducted to find all eligible studies of TP53 Arg72Pro polymorphism and leukemia risk. Fourteen case-control studies, with 2,506 cases and 4,386 controls, were selected for analysis. The overall data failed to indicate a significant association between TP53 Arg72Pro polymorphism and the risk of leukemia (C vs. G: OR = 1.09, 95% CI = 0.93–1.26; CC vs. GC + GG: OR = 1.23, 95% CI = 0.96–1.57). In a subgroup analysis of clinical types, an increased risk was observed in the acute lymphocytic leukemia (ALL) subgroup (CC vs. GC + GG: OR = 1.73; 95% CI = 1.07–2.81) but not in the acute myeloid leukemia (AML) subgroup. In the subgroup analysis, no significant associations with ethnicity and the source of the controls were observed. In conclusion, the results suggest that there is no association between TP53 Arg72Pro polymorphism and the risk of leukemia, but the CC genotype may increase the risk of ALL TP53 Arg72Pro polymorphism CC genotype may increase the risk of ALL but is not associated with AML. Further large-scale, well-designed studies are needed to confirm our results.

The Role of TP53 Gene Codon 72 Polymorphism in Leukemia: A PRISMA-Compliant Systematic Review and Meta-Analysis

The purpose of this meta-analysis was aimed to evaluate the association of tumor protein p53 (TP53) gene codon 72 polymorphism with leukemia susceptibility. We searched PubMed to identify relevant studies, and 16 case-control studies from 14 published articles were identified as eligible studies, including 2062 leukemia patients and 5826 controls. After extracting data, odds ratio (OR) with the corresponding 95% confidence interval (95%CI) was applied to assess the association between TP53 codon 72 polymorphism and leukemia susceptibility. The meta-analysis was performed with the Comprehensive Meta-Analysis software, version 2.2. Overall, no significant association between TP53 codon 72 polymorphism and leukemia susceptibility was found in this meta-analysis (Pro vs Arg: OR = 1.05, 95%CI = 0.90-1.21; Pro/Pro vs Arg/Arg: OR = 1.13, 95%CI = 0.84-1.52; Arg/Pro vs Arg/Arg: OR = 0.94, 95%CI = 0.76-1.15; [Pro/Pro + Arg/Pro] vs Arg/Arg: OR = 0.99, 95%CI = 0.80-1.21; Pro/Pro vs [Arg/Arg + Arg/Pro]: OR = 1.19, 95%CI = 0.93-1.51). Similar results were also found in subgroup analysis by ethnicity, source of controls, and types of leukemia (either acute myeloid leukemia or acute lymphocytic leukemia). Our meta-analysis demonstrates that TP53 codon 72 polymorphism may not be a risk factor for acute leukemia; however, due to the limitations of this study, it should be verified in future studies.

TP53 Pro72 allele potentially increases the poor prognostic significance of TP53 mutation in chronic lymphocytic leukemia

Previous studies have investigated the associations between TP53 mutations and codon 72 polymorphisms and prognosis in chronic lymphocytic leukemia (CLL). However, the joint effect of TP53 mutations and TP53 codon 72 polymorphisms on CLL prognosis remains uncertain. We used direct sequencing to detect TP53 mutations and codon 72 genotype in 207 patients with CLL. The Pro/Pro genotype was associated with an increased incidence of TP53 mutations and deletion, but had no apparent effect on biological tumor behavior or clinical response. Compared to patients with wild-type p53, patients with TP53 mutations and the Pro72 allele (Arg/Pro + Pro/Pro genotypes) were associated with unmutated immunoglobulin heavy-chain variable region status and chemorefractoriness. Overall survival (OS) in the entire patient group was differed significantly between patients with TP53 mutations and either the Pro72 allele or Arg/Arg homozygotes (P = 0.014). Notably, patients with TP53 mutation and the Pro72 allele experienced a 23.7-fold increase in hazard ratio (95% CI 3.38-165.9; P = 0.001) for OS compared with patients with wild-type p53 and those with the Arg/Arg genotype. The TP53 Pro72 allele potentially increases the prognostic significance of TP53 mutations in CLL.

MDM2 promoter polymorphism and p53 codon 72 polymorphism in chronic myeloid leukemia: the association between MDM2 promoter genotype and disease susceptibility, age of onset, and blast-free survival in chronic phase patients receiving imatinib

The genetic or functional inactivation of the p53 pathway plays an important role with regards to disease progression from the chronic phase (CP) to blast phase (BP) and imatinib treatment response in chronic myeloid leukemia (CML). Two functional single nucleotide polymorphisms (SNPs), p53 R72P and MDM2 SNP309, are associated with alternation of p53 activity, however the association regarding CML susceptibility and BP transformation under imatinib treatment is unclear. The MDM2 SNP309 genotype was determined by polymerase chain reaction-restriction fragment length polymorphism and confirmed by direct sequencing from 116 CML patients, including 104 in the CP at diagnosis, and 162 healthy Taiwanese controls. The p53 R72P polymorphism was examined in all CML patients. The SNP309 G/G genotype was associated with an increased risk of CML susceptibility (OR: 1.82, 95% CI: 1.03-3.22, P = 0.037), and an earlier age of disease onset (log-rank P = 0.005) compared with the T/T + T/G genotypes. Higher MDM2 mRNA expression was found in G/G genotype compared with T/T (P = 0.034) and T/T + T/G (P = 0.056) genotypes. No associations were found between the p53 R72P genotypes and clinical parameters and survival outcomes. Among 62 CP patients receiving imatinib as first-line therapy, the G/G genotype was associated with a shorter blast-free survival (log-rank P = 0.048) and more clonal evolution compared with the T/T + T/G genotypes. In patients with advanced diseases at diagnosis, the G/G genotype was associated with a poor overall survival (log-rank P = 0.006). Closely monitoring CML patients harboring the G/G genotype and further large-scale studies are warranted.

TP53 aberrations in chronic lymphocytic leukemia

CLL patients harboring TP53 defects remain the most challenging group in terms of designing rational and effective therapy. Irrespective of the treatment employed-chemotherapy, chemoimmunotherapy, or pure biological drugs-median survival of these patients does not exceed 3-4 years. This adverse outcome is caused by a less effective response to therapeutics acting through DNA damage induction and relying on the subsequent initiation of apoptosis as well as by virtually inevitable aggressive relapse. Patient proportions with TP53 defects at diagnosis or before first therapy were reported within the range 5-15 %, but they increase dramatically in pretreated cohorts (reported up to 44 %), and also in patients with Richter transformation (50 % harbor TP53 defects). Currently, most laboratories monitor TP53 defect as presence of 17p deletion using I-FISH, but 23-45 % of TP53-affected patients were shown to harbor only mutation(s). In other patients with intact TP53, the p53 pathway may be impaired by mutations in ATM gene coding for the p53-regulatory kinase; however, prognosis of ATM-defective patients is not as poor as those with TP53 abnormalities. Though many novel agents are under development, the monoclonal antibody alemtuzumab and allogeneic stem cell transplantation remain the basic treatment options for TP53-affected CLL patients.

p53 codon 72 polymorphism and hematological cancer risk: an update meta-analysis

Background

Previous studies on the association of p53 codon 72 (Arg72Pro) polymorphism with hematological malignancies risk have produced conflicting results. The purpose of this meta-analysis is to define the effect of p53 Arg72Pro polymorphism on hematological malignancies risk.

Methodology/Principal Findings

Through searching PubMed databases (or hand searching) up to April 2012 using the following MeSH terms and keywords: “p53”, “codon 72” “polymorphism” and “leukemia”, or “lymphoma”, or “myeloma”, thirteen were identified as eligible articles in this meta-analysis for p53 Arg72Pro polymorphism (2,731 cases and 7, 356 controls), including nine studies on leukemia (1,266 cases and 4, 474 controls), three studies on lymphoma (1,359 cases and 2,652 controls), and one study on myeloma. The overall results suggested that p53 Arg72Pro polymorphism was not associated with hematological malignancies risk. In stratified analyses, significantly increased non-Hodgkin lymphomas risk was found in p53 Arg72Pro polymorphism heterozygote model (Arg/Pro vs. Arg/Arg: OR = 1.18, 95%CI: 1.02–1.35) and dominant model (Arg/Pro+Pro/Pro vs. Arg/Arg: OR = 1.18, 95%CI: 1.03–1.34), but no significant association was found between leukemia risk and p53 Arg72Pro polymorphism. Further studies showed no association between leukemia risk and p53 Arg72Pro polymorphism when stratified in subtypes of leukemias, ethnicities and sources of controls.

Conclusions/Significance

This meta-analysis indicates that the p53 Arg72Pro polymorphism may contribute to susceptibility to non-Hodgkin lymphomas.

Meta-analysis of the association between P53 codon 72 polymorphisms and gastric cancer

PURPOSE

This meta-analysis aims to examine whether the P53 codon 72 polymorphisms is associated with gastric cancer risk.

METHODS

Pooled odds ratios (ORs) were appropriately derived from random-effects models. Separate analyses were conducted on Asian and Caucasian populations. And a total of 21 studies were eligible (5,867 cases and 7,001 controls); 15 of them were conducted on Asians, others on Caucasians.

RESULTS

The combined results based on all studies showed that there was significant difference in genotype distribution between gastric cancer and non-cancer patients in the allele contrast (Pro vs. Arg); the codominant model (Pro/Pro vs. Arg/Arg) and the recessive model (Pro/Pro vs. Pro/Arg + Arg/Arg). When stratifying for race, patients with gastric cancer had a significantly higher frequency of Pro (OR = 1.136, 95% CI = 1.051-1.229), Pro/Pro (OR = 1.314, 95% CI = 1.110-1.555), Pro/Arg (OR = 1.099, 95% CI = 1.009-1.197), (Pro/Pro + Pro/Arg (OR = 1.153, 95% CI = 1.059-1.255) than non-cancer patients among Asians. There was statistically significant heterogeneity across all included studies with the Q statistic and study population may be the most important factor contributed to the heterogeneity.

CONCLUSIONS

In conclusion, the P53 codon 72 polymorphisms seems to be associated with gastric cancer risk and the analyses suggested that P53 codon 72 polymorphisms may be an important biomarker of gastric cancer susceptibility for Asians.

Evaluation of TP53 mutations with the AmpliChip p53 research test in chronic lymphocytic leukemia: correlation with clinical outcome and gene expression profiling

Given that TP53 alterations predict prognosis and response to therapy in chronic lymphocytic leukemia (CLL), screening for TP53 mutations has an increasing role in patient management. TP53 direct sequencing is a time-consuming method, while the AmpliChip p53 Research Test is a novel non time-consuming microarray-based resequencing assay and queries Exons 2-11. We evaluated the impact of TP53 mutations on clinical outcome by analyzing 98 untreated CLL using the AmpliChip p53 Research Test and direct sequencing and performed microarrays analysis on TP53 mutated and/or deleted cases. The AmpliChip p53 Research Test detected 17 mutations in 14 patients (17.3%); a significant association between TP53 mutations and del(17p) was recorded. From a clinical standpoint, a higher percentage of mutation was found in CLL with unfavorable outcome (17.2% vs. 7.1% in progressive vs. stable cases). Detection of TP53 mutations by the AmpliChip p53 Research Test was associated with a significantly worse survival (P = 0.0002). Comparison of the array and direct sequencing tests showed that the p53 Research Test detected more mutations, although it failed to identify two microdeletions. Finally, microarrays analysis showed a more distinctive signature associated with del(17p) than with TP53 mutations, likely due to a concomitant gene dosage effect. The AmpliChip p53 Research Test is a straightforward method that bears prognostic value. This study confirms a high percentage of TP53 mutations in CLL with unfavorable outcome and a significant association between TP53 aberrations and del(17p). Finally, specific gene expression profiles are recognized for TP53 alterations.

A case-control study on the combined effects of p53 and p73 polymorphisms on head and neck cancer risk in an Italian population

Background

The purpose of this study is to analyze the combined effects of selected p53 and p73 polymorphisms and their interaction with lifestyle habits on squamous cell carcinoma of the head and neck (SCCHN) risk and progression in an Italian population.

Methods

Two hundred and eighty-three cases and 295 hospital controls were genotyped for p53 polymorphisms on exon 4 (Arg72Pro), intron 3 and 6, and p73 G4C14-to-A4T14. Their association with SCCHN was estimated using a logistic regression analysis, while a multinomial logistic regression approach was applied to calculate the effect of the selected polymorphisms on SCCHN different sites (oral cavity, oropharynx, hypopharynx and larynx). We performed an haplotype analysis of the p53 polymorphisms, and a gene-gene interaction analysis for the combined effects of p73 G4C14-to-A4T14 and p53 polymorphisms.

Results

We found a significant increased risk of SCCHN among individuals with combined p73 exon 2 G4A and p53 intron 3 variant alleles (OR = 2.22, 95% CI: 1.08–4.56), and a protective effect for those carrying the p53 exon 4-p53 intron 6 diplotype combination (OR = 0.67; 95% CI: 0.47–0.92). From the gene-environment interaction analysis we found that individuals aged < 45 years carrying p73 exon 2 G4A variant allele have a 12.85-increased risk of SCCHN (95% CI: 2.10–78.74) compared with persons of the same age with the homozygous wild type genotype. Improved survival rate was observed among p53 intron 6 variant allele carriers (Hazard Ratio = 0.51 (95% CI: 0.23–1.16).

Conclusion

Our study provides for the first time evidence that individuals carrying p53 exon 4 and p53 intron 6 variant alleles are significantly protected against SCCHN, and also shows that an additional risk is conferred by the combination of p73 exon 2 G4C14-to-A4T14 and p53 intron 3 variant allele. Larger studies are required to confirm these findings.

A case-control study on the effect of p53 and p73 gene polymorphisms on gastric cancer risk and progression

The p53 protein and its functional homologue p73 share several functions in modulating cell-cycle control and apoptosis. Based on the functional interaction between p53 and p73 in carcinogenesis, we investigated the combined effect of p73 G4C14-to-A4T14 and p53 gene polymorphisms and their interaction with selected environmental factors, on the risk for gastric cancer in a hospital-based case-control study conducted in Italy. The effect of these polymorphisms on cancer progression was also investigated. One hundred and fifteen gastric cancer cases and 295 hospital controls were genotyped for p73 G4C14-to-A4T14, and p53 exon 4 (Arg72Pro), intron 3 and intron 6 polymorphisms. An increased risk for gastric cancer was found to be associated with the inheritance of the p73 homozygous variant genotype among the gastric cancer intestinal histotype (odds ratio (OR)=6.75; 95% confidence interval (95% CI)=1.88-24.24). An effect modification of the p73 variant allele by gender was observed [(OR=2.82; 95%CI=1.24-6.40) among females, versus an OR of 0.70 (95%CI=0.32-1.54) among males; p-value for homogeneity among strata estimates =0.03]. Gene-gene interaction analyses demonstrated that individuals with combined p53 exon 4 and intron 6 variant alleles are borderline significantly protected from gastric cancer (OR=0.52; 95% CI=0.26-1.07; p-value for interaction =0.005), which was confirmed by the haplotype analysis. Finally, a poorer survival was observed among carriers of the variant allele of p53 intron 6 if compared with those carrying both wild-type alleles (p-value for log-rank test =0.02). This study shows that the p73 G4C14-to-A4T14 polymorphism may be a risk factor for gastric cancer, as reported from other studies in different tumour sites among Caucasians. Along with the protective effect of p53 exon 4-intron 6 allelic variants, already noted for breast and lung cancer, our results require confirmation from larger studies.

Susceptibility genes and B-chronic lymphocytic leukaemia

Common genetic variants are thought to increase the risk of chronic lymphocytic leukaemia (CLL), and case-control studies provide an approach to detect these variants. There have been multiple candidate gene studies published to date, but relatively few disease pathway studies or large genomic association studies. We summarize the results of these previous studies, as well as present results from our recent large pathway study of 9412 single nucleotide polymorphisms from 1253 immunity and inflammation genes in a study of 126 CLL cases and 484 frequency-matched controls. Several promising genes have been identified as susceptibility genes for risk of CLL across all of these association studies. However, a number of candidate gene studies have not been replicated in follow-up studies, whereas the results from disease pathway and large genomic studies have yet to be replicated in an independent sample. The challenge of future studies of this type will be overcoming study design issues, including definition of CLL, sample size limitations and multiple testing issues.

Scan of 977 nonsynonymous SNPs in CLL4 trial patients for the identification of genetic variants influencing prognosis

To identify genetic variants associated with outcome from chronic lymphocytic leukemia (CLL), we genotyped 977 nonsynonymous single nucleotide polymorphisms (nsSNPs) in 755 genes with relevance to cancer biology in 425 patients participating in a phase 3 trial comparing the efficacy of fludarabine, chlorambucil, and fludarabine with cyclophosphamide as first-line treatment. Selection of nsSNPs was biased toward those likely to be functionally deleterious. SNP genotypes were linked to individual patient outcome data and response to chemotherapy. The effect of genotype on progression-free survival (PFS) and overall survival (OS) was assessed by Cox regression analysis adjusting for treatment and clinico-pathologic variables. A total of 78 SNPs (51 dominantly acting and a further 27 recessively acting) were associated with PFS (9 also affecting OS) at the 5% level. These included SNPs mapping to the immune-regulation genes IL16 P434S (P = .03), IL19 S213F (P = .001), LILRA4 P27L (P = .004), KLRC4 S29I (P = .007), and CD5 V471A (P = .002); and DNA response genes POLB P242R (P = .04) and TOPBP1 S730L (P = .02), which were all independently prognostic of immunoglobulin heavy-chain variable region (IgVH) mutational status. The variants identified warrant further evaluation as promising prognostic markers of patient outcome. To facilitate the identification of prognostic markers through pooled analyses, we have made all data from our analysis publicly available.

TP53 mutations in human cancers: functional selection and impact on cancer prognosis and outcomes

A large amount of data is available on the functional impact of missense mutations in TP53 and on mutation patterns in many different cancers. New data on mutant p53 protein function, cancer phenotype and prognosis have recently been integrated in the International Agency for Research on Cancer TP53 database (http://www-p53.iarc.fr/). Based on these data, we summarize here current knowledge on the respective roles of mutagenesis and biological selection of mutations with specific functional characteristic in shaping the patterns and phenotypes of mutations observed in human cancers. The main conclusion is that intrinsic mutagenicity rates, loss of transactivation activities, and to a lesser extent, dominant-negative activities are the main driving forces that determine TP53 mutation patterns and influence tumor phenotype. In contrast, current experimental data on the acquisition of oncogenic activities (gain of function) by p53 mutants are too scarce and heterogenous to assess whether this property has an impact on tumor development and outcome. In the case of inherited TP53 mutations causing Li-Fraumeni and related syndromes, the age at onset of some tumor types is in direct relation with the degree of loss of transactivation capacity of missense mutations. Finally, studies on large case series demonstrate that TP53 mutations are independent markers of bad prognosis in breast and several other cancers, and that the exact type and position of the mutation influences disease outcome. Further studies are needed to determine how TP53 haplotypes or loss of alleles interact with mutations to modulate their impact on cancer development and prognosis.

No association between p53 gene intron 7 polymorphism and chronic atrophic gastritis in Han Chinese of Jiangsu province

AIM: To explore whether the polymorphism of p53 gene intron 7 is associated with the occurrence of chronic atrophic gastritis (CAG) in Han Chinese of Jiangsu province.

METHODS: The genome DNA was extracted from tissues of 80 CAG patients and 76 healthy controls, and the exon 7 and 8 as well as the intron 7 within exon 7 and 8 of p53 gene were amplified by polymerase chain reaction (PCR). The products were sequenced after purification. The polymorphism of p53 gene intron 7 was comparatively analyzed with the standard sequences. The genotypes and allelic frequencies compared between the two groups using chi-square test.

RESULTS: In CAG cases, the allelic frequencies of the 72^th base pair (bp) and the 92^th bp in p53 gene intron 7 were 32.5% (T-G) and 67.5% (C-T), and the frequencies of genotype T-G/T-G, C-T/T-G, and C-T/C-T were 11.3%, 42.5%, and 46.3%, respectively. Meanwhile in the controls, the allelic frequencies of T-G and C-T were 29.6% and 70.4%, and the frequencies of genotype T-G/T-G, C-T/T-G, and C-T/C-T were 9.2%, 40.8%, and 50.0%, respectively. There were no significant differences in the allelic frequencies and genotypic distributions between the two groups (P > 0.05). The risk of CAG occurrence was not significantly different between the individuals with T-G and C-T allele (OR = 1.14).

CONCLUSION: There is no direct association between the polymorphism of p53 gene intron 7 and epigenetic penetrance of CAG in Han Chinese of Jiangsu province.