P53 polymorphisms and haplotypes in lung cancer

Importance of TP53 codon 72 and intron 3 duplication 16 bp polymorphisms and their haplotypes in susceptibility to sarcopenia in Iranian older adults

Background

Sarcopenia is described as age-related progressive skeletal muscle failure that results in marked reduction in the patient’s independence and life quality. In this study, we explored the association of TP53 exon 4 Arg72pro (rs1042522) and Intron 3 16-bp Del/Ins (rs17878362) polymorphisms and their haplotypes with sarcopenia, anthropometric, body composition and biochemical parameters.

Methods

A total of 254 older individuals (65 sarcopenic and 189 healthy) were recruited in this research and genotyped by PCR–RFLP. Linear regression was applied to find the correlation between TP53 polymorphism, and biochemical and anthropometric parameters. The correlation between TP53 polymorphism and haplotypes and the risk of sarcopenia was investigated by logistic regression.

Results

Arg/Pro genotype carriers was at a lower (ORadj = 0.175, 95% CI = 0.068 – 0.447; P < 0.001) risk of sarcopenia compared to the Arg/Arg group. In haplotypes analysis, Arg-Ins (ORadj: 0.484, 95% CI = 0.231 – 1.011, P = 0.043) and Pro-Ins (ORadj: 0.473, 95% CI = 0.210 – 1.068, P = 0.022) haplotypes showed decreased risk of developing sarcopenia. Moreover, in the case of codon 72 polymorphism, skeletal muscle mass, appendicular lean mass (ALM), skeletal muscle mass index (SMI), hand grip strength and Triglycerides, for Intron 3 16-bp Del/Ins polymorphism, albumin, calcium, cholesterol, and LDL were different, and for the haplotypes, skeletal muscle mass, SMI, ALM, HDL and triglycerides were significantly different between groups.

Conclusions

We suggested that the Arg/Pro genotype of the codon 72 polymorphism in exon 4 of TP53, and Arginine-Insertion and Proline-Insertion haplotypes might decrease the risk of sarcopenia in Iranian older adults.

The cell cycle regulatory gene polymorphisms TP53 (rs1042522) and MDM2 (rs2279744) in lung cancer: a meta-analysis

Lung cancer is one of the most common types of cancer in the world. Although the mechanism of lung cancer is still unknown, a large number of studies have found a link between gene polymorphisms and the risk of lung cancer. The tumor suppressor p53 plays a crucial role in maintaining genomic stability and tumor prevention. MDM2 is a critical regulator of the p53 protein. Despite the importance of p53 pathway in cancer, data on the contribution of SNPs of TP53 (rs1042522) and MDM2 (rs2279744) to the development of lung cancer are very contradictory. A metaanalysis that collects quantitative data from individual studies and combines their results has the advantage of improving accuracy, providing reliable estimates, and resolving those issues in which studies on individual associations are not effective enough. The aim of this study was to determine whether the TP53 (rs1042522) and MDM2 (rs2279744) polymorphisms confer susceptibility to lung cancer. A meta-analysis was conducted on the associations between the TP53 (rs1042522) and MDM2 (rs2279744) polymorphisms and lung cancer. A total of 51 comparison studies including 25,366 patients and 25,239 controls were considered in this meta-analysis. The meta-analysis showed no association between lung cancer and MDM2 (rs2279744) under any model. A noteworthy association of TP53 (rs1042522) with susceptibility to lung cancer in overall pooled subjects was observed under three different models (allele contrast, homozygote contrast (additive) and dominant). Stratification by ethnicity indicated an association between the TP53 (rs1042522) and lung cancer in Asians and Caucasians. This meta-analysis demonstrates that the TP53 (rs1042522), but not MDM2 (rs2279744) polymorphism may confer susceptibility to lung cancer.

No association of TP53 codon 72 and intron 3 16-bp duplication polymorphisms with breast cancer risk in Chinese Han women: new evidence from a population-based case-control investigation

Background

Many studies have demonstrated that the genetic variants of tumor suppressor gene TP53 contribute to the prediction of breast cancer risk. However, most of them focused on Europeans and Americans; the investigations about Asians, especially Chinese women, are scarce. Thus, the aim of this study was to explore the influence of TP53 codon 72 and intron 3 16-bp duplication polymorphisms on the breast cancer risk in Chinese women, especially those from eastern China.

Methods

Blood samples collected from 254 breast cancer patients and 252 healthy female individuals were investigated. Genotypes of the two polymorphisms were determined by direct sequencing and conventional PCR, respectively.

Results

Heterozygous Arg/Pro and homozygous Del/Del were the most frequent genotypes of the two polymorphisms, respectively. Heterozygous Arg/Pro had a higher prevalence in breast cancer cases (P_adj = 0.10; OR_adj = 1.43, 95% CI 0.93–2.18), and no homozygous 16-bp duplication (Ins/Ins) genotype was found in the whole 506 clinical samples. For the distributions of allele and haplotype frequencies, no statistically significant difference was observed between the two groups when multiple (additive, dominant and recessive) genetic models were utilized in the analysis (P_adj > 0.05).

Conclusion

The results suggested that the two TP53 polymorphisms did not affect breast cancer risk in Chinese Han women, but the heterozygous Arg/Pro may exist as the possible risk genotype of the codon 72 polymorphism in contrast to the homozygous Arg/Arg and Pro/Pro.

Electronic supplementary material

The online version of this article (10.1186/s40001-018-0345-6) contains supplementary material, which is available to authorized users.

Role of cancer stem cells in racial disparity in colorectal cancer

Although African‐Americans (AAs) have a higher incidence of colorectal cancer (CRC) than White people, the underlying biochemical mechanisms for this increase are poorly understood. The current investigation was undertaken to examine whether differences in self‐renewing cancer stem/stem‐like cells (CSCs) in the colonic mucosa, whose stemness is regulated by certain microRNAs (miRs), could partly be responsible for the racial disparity in CRC. The study contains 53 AAs and 47 White people. We found the number of adenomas and the proportion of CD44⁺CD166⁻  CSC phenotype in the colon to be significantly higher in AAs than White people. MicroRNAs profile in CSC‐enriched colonic mucosal cells, expressed as ratio of high‐risk (≥3 adenomas) to low‐risk (no adenoma) CRC patients revealed an 8‐fold increase in miR‐1207‐5p in AAs, compared to a 1.2‐fold increase of the same in White people. This increase in AA was associated with a marked rise in lncRNA PVT1 (plasmacytoma variant translocation 1), a host gene of miR‐1207‐5p. Forced expression of miR‐1207‐5p in normal human colonic epithelial cells HCoEpiC and CCD841 produced an increase in stemness, as evidenced by morphologically elongated epithelial mesenchymal transition( EMT) phenotype and significant increases in CSC markers (CD44, CD166, and CD133) as well as TGF‐β, CTNNB1, MMP2, Slug, Snail, and Vimentin, and reduction in Twist and N‐Cadherin. Our findings suggest that an increase in CSCs, specifically the CD44⁺CD166⁻ phenotype in the colon could be a predisposing factor for the increased incidence of CRC among AAs. MicroRNA 1207‐5p appears to play a crucial role in regulating stemness in colonic epithelial cells in AAs.

TP53 Codon 72 Polymorphisms and Lung Cancer Risk in the Bangladeshi Population

OBJECTIVE

To assess associations between codon 72 polymorphisms (Pro or B and Arg or b alleles) of the TP53 gene and lung cancer risk among Bangladeshis.

MATERIALS AND METHODS

The distribution of the BB, Bb, and bb genotypes and the frequencies of the B and b alleles were determined by PCR-RFLP method using DNA extracted from leucocytes of 50 confirmed lung cancer patients and 50 age-matched controls and the data were analysed.

RESULTS

The ratio of BB, Bb, and bb genotypes were in Hardy-Weinberg equilibrium except for the male patients (χ2=4.6). The B allele is overrepresented among all patients (OR=2.0, p=0.02) and the female patients (OR=4.1, p≤0.01) compared to the controls. The BB/bb ratio was also higher among the patients (OR=3.0, p=0.03). The relative risk of cancer for having BB over bb genotype was 1.8 (p=0.04) but no effect was observed for the Bb genotype. The B allele was overrepresented among patients with adenocarcinomas (OR=2.4, p≤0.01) and squamous cell carcinomas (OR=2.7, p≤0.01) over the controls but the difference was not significant for those with small cell lung carcinomas (OR=1.1, p=0.66). The B allele was overrepresented among patients age 50 or younger (OR=2.7, p≤0.01), but not for older patients (OR=1.7, p=0.07), and among smokers compared to the controls (OR=1.8-10.0, p≤0.01-0.03). However, no correlation between increasing pack-years and lung cancer was observed.

CONCLUSIONS

The Pro/Pro (BB) genotype and the B allele are risk factors for lung cancer among Bangladeshis, particularly for people under age 50, women and smokers.

Tumor suppressor miR-24 restrains gastric cancer progression by downregulating RegIV

BACKGROUND

microRNAs are small noncoding RNAs that modulate a variety of cellular processes by regulating multiple targets, which can promote or inhibit the development of malignant behaviors. Accumulating evidence suggests miR-24 plays important roles in human carcinogenesis. However, its precise biological role remains largely elusive. This study examined the role of miR-24 in gastric cancer (GC).

METHODS

The expression of miR-24 in GC tissues compared with matched non-tumor tissues and GC cells was detected by qRT-PCR. Synthetic short single or double stranded RNA oligonucleotides and lentiviral vectors were used to regulate miR-24 expression in GC cells to investigate its function in vitro and in vivo.

RESULTS

miR-24 was significantly downregulated in GC tissues compared with matched non-tumor tissues and was associated with tumor differentiation. Ectopic expression of miR-24 in SGC-7901 GC cells suppressed cell proliferation, migration and invasion in vitro as well as tumorigenicity in vivo by inducing cell cycle arrest in G0/G1 phase and promoting cell apoptosis. Furthermore, we identified RegIV as a target of miR-24 and demonstrated that miR-24 regulated RegIV expression via binding its 3' untranslated region.

CONCLUSIONS

miR-24 functions as a novel tumor suppressor in GC and the anti-oncogenic activity may involve its inhibition of the target gene RegIV. These findings suggest the possibility for miR-24 as a therapeutic target in GC.

The association between TP53 Arg72Pro polymorphism and lung cancer susceptibility: evidence from 30,038 subjects

BACKGROUND

The TP53 codon 72 polymorphism has been associated with the individual susceptibility to lung cancer. However, the association remains uncertain and varies with ethnicity, smoking status, cancer histology, and stage.

METHODS

We performed a meta-analysis to evaluate the relationship between TP53 Arg72Pro polymorphism and lung cancer susceptibility basing on 15,647 lung cancer patients and 14,391 controls from 36 published literatures. We also performed stratified analysis in populations of different ethnicities, smoking statuses, lung cancer stages, and histological types.

RESULTS

The analysis showed a significantly increased lung cancer susceptibility among Pro allele carriers (P < 0.001, odds ratio (OR) = 1.14, 95% confidence interval (CI) = 1.1-1.19), especially for smokers (P < 0.001, OR = 1.29, 95% CI = 1.12-1.47). Stratified analysis indicated that Pro72 elevates lung cancer susceptibility in Asians, while it has no effect on lung cancer risk of Caucasians. Moreover, Pro carriers present an increased risk of developing squamous cell carcinoma and adenocarcinoma, instead of large cell carcinoma and small cell carcinoma. Interestingly, patients with the Pro allele seemed to be diagnosed with lung cancer at the early stages (stage I-II, P = 0.008, OR = 1.2, 95% CI = 1.05-1.37).

CONCLUSIONS

Our results suggest that the Pro allele acts as a risk factor for development of lung cancer, especially for smokers and Asians.

Molecular characterization of TP53 gene in human populations exposed to low-dose ionizing radiation

Ionizing radiation, such as that emitted by uranium, may cause mutations and consequently lead to neoplasia in human cells. The TP53 gene acts to maintain genomic integrity and constitutes an important biomarker of susceptibility. The present study investigated the main alterations observed in exons 4, 5, 6, 7, and 8 of the TP53 gene and adjacent introns in Amazonian populations exposed to radioactivity. Samples were collected from 163 individuals. Occurrence of the following alterations was observed: (i) a missense exchange in exon 4 (Arg72Pro); (ii) 2 synonymous exchanges, 1 in exon 5 (His179His), and another in exon 6 (Arg213Arg); (iii) 4 intronic exchanges, 3 in intron 7 (C → T at position 13.436; C → T at position 13.491; T → G at position 13.511) and 1 in intron 8 (T → G at position 13.958). Alteration of codon 72 was found to be an important risk factor for cancer development (P = 0.024; OR = 6.48; CI: 1.29–32.64) when adjusted for age and smoking. Thus, TP53 gene may be an important biomarker for carcinogenesis susceptibility in human populations exposed to ionizing radiation.

p53 codon 72 polymorphism and hepatocellular carcinoma: a meta-analysis

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignant neoplasms worldwide. The p53 gene is frequently mutated in some histological subtypes of HCC. The role of p53 mutations and polymorphic variant of codon 72 in the prognosis of disease is still unclear. The p53 tumor suppressor gene Arg72Pro polymorphism has been associated with HCC. However, results were inconsistent. This meta-analysis was performed to estimate the association between p53 Arg72Pro polymorphism and HCC or HCC infected by HBV/HCV.

METHODS

Electronic search of PubMed was conducted to select studies. Studies containing available genotype frequencies of Arg72Pro were chosen, and pooled odds ratio (OR) with 95 % confidence interval (CI) was used to assess the association.

RESULTS

Ten published studies, including 1,371 HCC cases and 2,517 controls were identified. The overall results suggested that the variant genotypes were associated with the HCC risk (Pro/Pro vs. Pro/Arg + Arg/Arg: OR 1.355, 95 % CI 1.041-1.764, p = 0.024). In the stratified analysis, individuals with the Pro/Pro in the recessive model had increased risk of HCC (OR 1.927, 95 % CI 1.127-3.297, p = 0.017) in Caucasian. A symmetric funnel plot, the Begg's test, was suggestive of the lack of publication bias. There was no association between the p53 codon 72 polymorphism and HBV/HCV-positive HCC.

CONCLUSION

This meta-analysis suggests that p53 condon 72 Pro/Progenotypes are associated with increased risk of HCC in Caucasian. To validate this association, further studies with larger participants worldwide are needed to examine the associations between this polymorphism and HCC.

Investigation of Differences in P53 Gene Polymorphisms between Schizophrenia and Lung Cancer Patients in the Turkish Population

Objective. The reduced incidence of cancer observed in schizophrenia patients may be related to differences in genetic background. It has been suggested that genetic predisposition towards schizophrenia is associated with reduced vulnerability to lung cancer, and p53 gene is one of the candidate genes. In our study, we aimed to investigate polymorphisms in the BstUI in exon 4 and MspI in intron 6 restriction sites of the p53 gene in Turkish schizophrenia patients, lung cancer patients, and controls. Material and Methods. Allele and genotype incidence of these polymorphisms with their haplotype combinations were studied in 100 Turkish lung cancer and schizophrenia patients and 100 controls without malignant and schizophrenia diseases. The genotype characteristics were determined by PCR-based RFLP method using DNA extracted from peripheral blood. Results. For the BstUI and MspI polymorphism, there were found significant differences in the genotype and allele frequencies between schizophrenia and lung cancer patients with control groups (P < .01). The analysis based on haplotype frequencies showed the presence of BstUI-MspI 2-1 haplotype in cancer patients (12%) in contrast to the absence of this haplotype in schizophrenia and controls. Only in lung cancer patients we found both significant decrease of A1 allele of the p53 codon 72 (OR 0.23, 95% CI 0.9–0.58) and A1/A1 homozygous genotype (P < .0001, OR 0.19). Conclusion. The results of this study suggest a protective effect of A1 allele against lung cancer, and the p53 MspI polymorphism may modify the susceptibility to lung cancer as a single factor rather than in combination with BstUI polymorphism.

TP53 polymorphisms in gliomas from Indian patients: Study of codon 72 genotype, rs1642785, rs1800370 and 16 base pair insertion in intron-3

Several single nucleotide polymorphisms of the TP53 gene have been reported, amongst which polymorphism in codon 72 (rs1042522) has received significant attention and shown to be associated with disease susceptibility in different cancer types. However, there are variable reports on this polymorphism in gliomas from worldwide with inconsistent results. In addition, the implications of other polymorphic loci are not much explored in gliomas. Hence, in the present study the TP53 sequence was analyzed for all polymorphism and mutations in a total of 84 gliomas of different types and grades from patients of Indian origin. The complete sequence of all coding exons (2 to 11) and introns 2, 3, 5 and 8 of TP53 gene were studied while for introns 1, 4, 6, 7, 9 and 10, only exon flanking regions could be studied. The polymorphic loci were compared with control population. In addition to the well known codon 72 polymorphism (rs1042522), three other polymorphisms rs1642785, rs1800370 and a 16 base pair insertion in intron-3 were found. At codon 72, our study showed higher Arg/Arg genotype in gliomas compared to normal population (38% versus 13%). The Arg allele frequency in glioma patients was comparatively higher than controls (0.55 versus 0.45; P=0.037). The Arg allele frequency was also high in adult glioblastomas compared to paediatric counterparts (0.55 versus 0.36). However, there was no significant association of TP53 mutations with any genotype of codon 72. At rs1642785, the G allele frequency was significantly higher in gliomas than in control population (0.55 versus 0.36, P=0.005). The genotype at a 16 base pair insertion in intron-3 was almost similar in case and control. However, the polymorphism at rs1800370 was exclusive to gliomas. This is the first report of TP53 gene polymorphism in glioma patients from India. Our study also delineates the frequency of four polymorphisms in gliomas for the first time. The codon 72 variant (rs1042522) and rs1642785 polymorphisms possibly poses risk to glioma development in Indian population. However, the functional significance of these polymorphism needs further elucidation.

CD8+ T cell recognition of polymorphic wild-type sequence p53(65-73) peptides in squamous cell carcinoma of the head and neck

The TP53 tumor suppressor gene contains a well-studied polymorphism that encodes either proline (P) or arginine (R) at codon 72, and over half of the world's population is homozygous for R at this codon. The wild-type sequence (wt) p53 peptide, p53(65-73), has been identified as a CD8+ T cell-defined tumor antigen for use in broadly applicable cancer vaccines. However, depending on the TP53 codon 72 polymorphism of the recipient, the induced responses to the peptides incorporating R (p53(72R)) or P (p53(72P)) can be "self" or "non-self." Thus, we sought to determine which wt p53(65-73) peptide should be used in wt p53-based cancer vaccines. Despite similar predicted HLA-A2-binding affinities, the p53(72P) peptide was more efficient than the p53(72R) peptide in HLA-A2 stabilization assays. In vitro stimulation (IVS) of CD8+ T cells obtained from healthy HLA-A2(+) donors with these two peptides led to the generation of CD8+ T cell effectors in one-third of the samples tested, at a frequency similar to the responsiveness to other wt p53 peptides. Interestingly, regardless of their p53 codon 72 genotype, CD8+ T cells stimulated with either p53(72P) or p53(72R) peptide were cross-reactive against T2 cells pulsed with either peptide, as well as HLA-A2(+) head and neck cancer (HNC) cell lines presenting p53(72P) and/or p53(72R) peptides for T cell recognition. Therefore, the cross-reactivity of CD8+ T cells for the polymorphic wt p53(65-73) peptides, irrespective of their p53 codon 72 polymorphism, suggests that employing either peptide in wt p53-based vaccines can result in efficient targeting of this epitope.

International Lung Cancer Consortium: coordinated association study of 10 potential lung cancer susceptibility variants

BACKGROUND

Analysis of candidate genes in individual studies has had only limited success in identifying particular gene variants that are conclusively associated with lung cancer risk. In the International Lung Cancer Consortium (ILCCO), we conducted a coordinated genotyping study of 10 common variants selected because of their prior evidence of an association with lung cancer. These variants belonged to candidate genes from different cancer-related pathways including inflammation (IL1B), folate metabolism (MTHFR), regulatory function (AKAP9 and CAMKK1), cell adhesion (SEZL6) and apoptosis (FAS, FASL, TP53, TP53BP1 and BAT3).

METHODS

Genotype data from 15 ILCCO case-control studies were available for a total of 8431 lung cancer cases and 11 072 controls of European descent and Asian ethnic groups. Unconditional logistic regression was used to model the association between each variant and lung cancer risk.

RESULTS

Only the association between a non-synonymous variant of TP53BP1 (rs560191) and lung cancer risk was significant (OR = 0.91, P = 0.002). This association was more striking for squamous cell carcinoma (OR = 0.86, P = 6 x 10(-4)). No heterogeneity by center, ethnicity, smoking status, age group or sex was observed. In order to confirm this association, we included results for this variant from a set of independent studies (9966 cases/11,722 controls) and we reported similar results. When combining all these studies together, we reported an overall OR = 0.93 (0.89-0.97) (P = 0.001). This association was significant only for squamous cell carcinoma [OR = 0.89 (0.85-0.95), P = 1 x 10(-4)].

CONCLUSION

This study suggests that rs560191 is associated to lung cancer risk and further highlights the value of consortia in replicating or refuting published genetic associations.

Intron 3 16 bp duplication polymorphism of TP53 contributes to cancer susceptibility: a meta-analysis

A few genetic polymorphisms of TP53 are known to have a significant effect on cancer susceptibility. Intron 3 16 bp duplication polymorphism of TP53 has been reported to be associated with breast cancer, colorectal cancer, lung cancer and other cancers, but the reported results remain inconclusive. The present study, a meta-analysis including a total of 9801 cases and 10,391 controls from 26 studies, revealed that the 16 bp insertion (Ins) allele is significantly associated with an increased cancer risk in overall analysis [Ins/Ins + deletion (Del)/Ins versus Del/Del: odds ratio (OR) = 1.14, 95% confidence interval (CI) = 1.02-1.27, P = 0.02; Ins/Ins versus Del/Del: OR = 1.35, 95% CI = 1.11-1.63, P = 0.002; Del/Ins versus Del/Del: OR = 1.10, 95% CI = 0.98-1.23, P = 0.11.), particularly in breast cancer subgroup (Ins/Ins + Del/Ins versus Del/Del: OR = 1.16, 95% CI = 1.03-1.31, P = 0.02; Ins/Ins versus Del/Del: OR = 1.81, 95% CI = 1.30-2.52, P < 0.001; Del/Ins versus Del/Del: OR = 1.10, 95% CI = 0.97-1.25, P = 0.13). The relative risks to the colorectal and lung cancers increased but their association power was relatively weak, which may result from a limited number of studies of these two cancer types. These results suggest that intron 3 16 bp duplication polymorphism of TP53 is potentially an important and clinically relevant genetic marker contributing to cancer susceptibility.

Differential levels of transcription of p53-regulated genes by the arginine/proline polymorphism: p53 with arginine at codon 72 favors apoptosis

Human populations contain a functional coding polymorphism (codon 72) in the p53 gene. To explore whether this polymorphism alters the transcriptional pattern of p53-regulated genes, the human isogenic cell lines harboring p53 with either the proline or arginine at codon 72 were employed to activate p53-mediated transcription. Thirty-four p53-regulated genes were assayed for their increased levels of mRNA using quantitative real-time PCR. The largest difference between p53-arginine and p53-proline was found with the PERP gene involved in cell-cell adhesion and apoptosis. The most common set of genes that are transcribed better by the p53-arginine protein than the p53-proline protein was found in the apoptotic function (DR-4, NOXA, PUMA, and PIG-3). LIF, a cytokine that is required for optimal reproductive function, was produced at 2x higher levels by the p53-arginine than the p53-proline allele. The genes that induced their mRNAs at the highest levels compared to the baseline tended to be synthesized better by the p53-arginine protein than the p53-proline protein. These molecular studies may help to explain the complicated associations observed between this polymorphism and the incidence of some cancers, the longevity of some populations, and the fecundity of different groups.

TP53 Arg72Pro polymorphism and lung cancer risk: a meta-analysis

No clear consensus has been reached on the TP53 Arg72Pro polymorphism (G12139C) and lung cancer risk. Thus, a meta-analysis was conducted to summarize the possible association. There was no statistical association between 12139C (Pro allele) and lung cancer risk in Caucasians compared with 12139G allele. However, the association was observed in all subjects (9,387 patients and 9,922 controls, p=0.04, OR=1.08, 95% CI 1.00-1.17), as well as in Asians (p=0.0004, OR=1.14, 95% CI 1.06-1.22). The association was also found in Asians under recessive genetic model (p<0.00001, OR=1.37, 95% CI 1.20-1.57) and homozygote comparison (CC vs. GG) (p<0.0001, OR=1.34, 95% CI 1.16-1.56). 12139C allele might increase the lung adenocarcinoma risk compared with 12139G allele (p=0.01, OR=1.11, 95% CI 1.02-1.21), and the effect was also found under recessive genetic model (p=0.003, OR=1.28, 95% CI 1.09-1.50) and homozygote comparison (CC vs. GG) (p=0.007, OR=1.28, 95% CI 1.07-1.52). There was an elevated association between the 12139C and the stage I lung cancer under dominant genetic model (p=0.04, OR=1.48, 95% CI 1.02-2.16), but no association was observed in other stages. No association of smoking was found between 12139C allele and lung cancer under recessive genetic model. Our result indicated that 12139C might increase the risk of lung cancer under recessive genetic model in adenocarcinoma, in Asians, and in lung cancer stage I. More studies stratified for lung cancer stage-genotyping interaction should be performed to clarify the role of TP53 Arg72Pro polymorphism in the development of lung cancer.

Polymorphisms in p53 and the p53 pathway: roles in cancer susceptibility and response to treatment

The p53 tumour suppressor protein lies at the crossroads of multiple cellular response pathways that control the fate of the cell in response to endogenous or exogenous stresses and inactivation of the p53 tumour suppressor signalling pathway is seen in most human cancers. Such aberrant p53 activity may be caused by mutations in the TP53 gene sequence producing truncated or inactive mutant proteins, or by aberrant production of other proteins that regulate p53 activity, such as gene amplification and overexpression of MDM2 or viral proteins that inhibit or degrade p53. Recent studies have also suggested that inherited genetic polymorphisms in the p53 pathway influence tumour formation, progression and/or response to therapy. In some cases, these variants are clearly associated with clinico-pathological variables or prognosis of cancer, whereas in other cases the evidence is less conclusive. Here, we review the evidence that common polymorphisms in various aspects of p53 biology have important consequences for overall tumour susceptibility, clinico-pathology and prognosis. We also suggest reasons for some of the reported discrepancies in the effects of common polymorphisms on tumourigenesis, which relate to the complexity of effects on tumour formation in combination with other oncogenic changes and other polymorphisms. It is likely that future studies of combinations of polymorphisms in the p53 pathway will be useful for predicting tumour susceptibility in the human population and may serve as predictive biomarkers of tumour response to standard therapies.

P53 polymorphism and lung cancer susceptibility: a pooled analysis of 32 case-control studies

To explore the real association between p53 codon 72 polymorphism and lung cancer risk, a pooled analysis of 32 case-control studies involving 19,255 subjects was conducted. When all 32 studies were pooled into the analysis, significantly elevated lung cancer risks were associated with variant genotypes in all genetic models (for Pro/Arg vs. Arg/Arg: OR 1.21, 95% CI 1.01-1.23; for Pro/Pro vs. Arg/Arg: OR 1.20, 95% CI 1.03-1.39; for Pro/Pro + Pro/Arg vs. Arg/Arg: OR 1.14, 95% CI 1.03-1.25; for Pro/Pro vs. Arg/Arg + Pro/Arg: OR 1.06, 95% CI 1.01-1.12). In the subgroup analysis by ethnicity, histological type, or smoking status, significantly increased risks were found in subgroups such as Asians, Caucasians, lung adenocarcinoma patients, or smokers, respectively. In conclusion, our results suggest that the Pro allele at p53 codon 72 is emerging as a low-penetrance susceptibility allele for lung cancer development.

A meta-analysis of TP53 codon 72 polymorphism and lung cancer risk: evidence from 15,857 subjects

The genetic polymorphism of TP53 codon 72 is thought to have significant effect on lung cancer risk, but the results are inconsistent. In this meta-analysis, we assessed 23 published studies involving 15,857 subjects of the association between TP53 codon 72 polymorphism and risk of lung cancer. For the homozygote Pro/Pro and Pro allele carriers (Pro/Pro+Pro/Arg), the ORs for all studies combined (7495 cases and 8362 controls) were 1.221 (95% CI=1.046-1.425; P=0.021 for heterogeneity) and 1.148 (95% CI=1.040-1.266; P=0.008 for heterogeneity). In the stratified analysis by ethnicity, significantly increased risks were found in Asians (3254 cases and 3350 controls) for both the homozygote Pro/Pro (OR=1.395; 95% CI=1.206-1.613; P=0.806 for heterogeneity) and the Pro allele carriers (OR=1.109; 95% CI=1.000-1.228; P=0.458 for heterogeneity). In Caucasians (3359 cases and 3953 controls), significantly elevated risk was associated with Pro allele carriers (OR=1.180; 95% CI=1.029-1.353; P=0.073 for heterogeneity). In the subgroup analyses by pathological type, the ORs for the homozygote Pro/Pro and Pro allele carriers were 1.289 (95% CI=1.027-1.618; P=0.096 for heterogeneity) and 1.168 (95% CI=1.062-1.284; P=0.231 for heterogeneity) for lung adenocarcinoma (2724 cases and 6591 controls). When stratified by smoking status, the pooled OR was 1.440 (95% CI=1.078-1.923; P=0.042 for heterogeneity) for the Pro allele carriers among smokers (1480 cases and 1414 controls). Although some statistical bias could not be eliminated, this meta-analysis suggests that the Pro allele is a low-penetrant risk factor for developing lung cancer. Additionally, we found that this phenomenon was more prominent in subgroups such as in Asians and Caucasians, in lung adenocarcinoma, or in smokers.

Association between p53 codon 72 genetic polymorphism and tobacco use and lung cancer risk

Lung cancer (LCa) is the leading cause of death by cancer in men. Genetic and environmental factors play a synergistic role in its etiology. We explore in 111 lung cancer cases and 133 unrelated noncancer controls the gene-environment interaction (G x E) between p53cd72 polymorphism variants and smoking and the effect on LCa risk in two kinds of case-control designs. We assessed the interaction odds ratio (IOR) using an adjusted unconditional logistic model. We found a significant and positive interaction association between Pro* allele carriers and smoking habits in both case-control and case-only designs: IOR = 3.90 (95% confidence interval [CI] = 1.10-13.81) and 3.05 (95% CI = 1.63-5.72), respectively. These exploratory results suggest a synergistic effect of the smoking habit and the susceptibility of the Pro allele on lung cancer risk compared with each risk factor alone.

Construction of a high resolution linkage disequilibrium map to evaluate common genetic variation in TP53 and neural tube defect risk in an Irish population

Genetic and environmental factors contribute to the etiology of neural tube defects (NTDs). While periconceptional folic acid supplementation is known to significantly reduce the risk of NTDs, folate metabolic pathway related factors do not account for all NTDs. Evidence from mouse models indicates that the tumor protein p53 (TP53) is involved in implantation and normal neural tube development. To determine whether genetic variation in TP53 might contribute to NTD risk in humans, we constructed a high resolution linkage disequilibrium (LD) map of the TP53 genomic region based on genotyping 21 markers in an Irish population. We found that nine of these variants can be used to capture the majority of common variation in the TP53 genomic region. In contrast, the 3-marker haplotype commonly reported in the TP53 literature offers limited coverage of the variation in the gene. We used the expanded set of polymorphisms to measure the influence of TP53 on NTDs using both case-control and family based tests of association. We also assayed a functional variant in the p53 regulator MDM2 (rs2279744). Alleles of three noncoding TP53 markers were associated with NTD risk. A case effect was seen with the GG genotype of rs1625895 in intron 6 (OR = 1.37 [1.04-1.79], P = 0.02). A maternal effect was seen with the 135/135 genotype of the intron 1 VNTR (OR = 1.86 [1.16-2.96], P = 0.01) and the TT genotype of rs1614984 (RR = 0.58 [0.37-0.91], P = 0.02). As multiple comparisons were made, these cannot be considered definitive positive findings and additional investigation is required.

Metabolic gene polymorphisms andp53mutations in healthy centenarians and younger controls

To obtain insights into the genetic mechanisms of ageing, we studied the frequency of the simultaneous presence of polymorphisms in phase I and phase II genes and of several p53 germline mutations in a group of 66 nonagenarians and centenarians in good health, selected from a larger sample of a multicentre Italian study in Northern Italy, and in a sample of 150 young healthy volunteers of the same ethnic group. We found a statistically significant difference in the frequency of 1the GSTT1 deletion and the p53 genotypes: the absence of any p53 polymorphisms and of GSTT1 deletion, and the simultaneous presence of the three p53 polymorphisms and of GSTT1 deletion, were much more frequent in young subjects than in centenarians (41.5% versus 26.9% and 8.8% versus 3.8%, respectively). One hypothesis to explain this difference is that subjects with both GSTT1 deletion and p53 polymorphisms may accumulate carcinogens and may have reduced DNA repair ability, and thus are more at risk for cancer. Another possible explanation is that both metabolic genes and p53 act on pathways related to cell ageing and death, and therefore certain composite genetic patterns could represent a generic mechanism of protection against ageing, not just against the development of chronic diseases. It is likely that longevity is related to a complex genetic trait as well as to certain environmental exposures.

Importance of TP53 codon 72 and intron 3 duplication 16bp polymorphisms in prediction of susceptibility on breast cancer

Background

TP53 is one of major tumour suppressor genes being essential in preservation of genome integrity. Two very common polymorphisms have been demonstrated to contribute to cancer susceptibility and tumour behaviour. The purpose of this study was to evaluate the role of Arg72Pro and PIN3 Ins16bp polymorphisms in TP53 gene as genetic susceptibility and predictive markers to breast cancer.

Methods

We analysed DNA samples from 264 breast cancer patients and 440 controls, for TP53 Arg72Pro and PIN3 Ins16bp polymorphisms using PCR-RFLP.

Results

We observed that women with A2A2 genotype have increased risk for developing breast cancer, either in women with or without familial history (FH) of the disease (OR = 4.40, 95% CI 1.60–12.0; p = 0.004; OR = 3.88, 95% CI 1.18–12.8; p = 0.026, respectively). In haplotype analysis, statistically significant differences were found between TP53 Arg-A2 haplotype frequencies and familial breast cancer cases and the respective control group (OR = 2.10, 95% CI 1.08–4.06; p = 0.028). Furthermore, both TP53 polymorphisms are associated with higher incidence of lymph node metastases.

Conclusion

Our findings suggest TP53 PIN3 Ins16bp polymorphism as a real risk modifier in breast cancer disease, either in sporadic and familial breast cancer. Furthermore, both TP53 polymorphisms are associated with higher incidence of lymph node metastases.

Genetic polymorphisms in TP53, nonsteroidal anti-inflammatory drugs and the risk of colorectal cancer: evidence for gene-environment interaction?

OBJECTIVE

Substantial evidence indicates that nonsteroidal anti-inflammatory drugs protect against colorectal cancer by altering cell cycle progression and/or inducing apoptosis, whereas p53 protein is crucial to maintaining cell-cycle arrest and regulating DNA repair, differentiation, and apoptosis. Genetic variants in TP53 gene might therefore influence colorectal cancer risk and modify the effects of nonsteroidal anti-inflammatory drugs. We assessed the association of TP53 Arg72Pro and p53PIN3 polymorphisms with colorectal cancer risk and their possible interaction with nonsteroidal anti-inflammatory drug use.

METHODS

We included 467 cases and 563 controls from a population-based case-control study. Multivariate logistic regression analysis was used to estimate the association between genotypes, environmental exposures and colorectal cancer risk, adjusting for potential confounders.

RESULTS

Odds ratios of colorectal cancer were 0.75 (95% confidence interval, 0.57-0.99) for TP53 72Pro carriers compared with those homozygous for the TP53 72Arg allele and 0.78 (95% confidence interval, 0.58-1.05) for p53PIN3 A2 carriers compared with p53PIN3 A1A1. Risks differed by nonsteroidal anti-inflammatory drug use. For both investigated TP53 polymorphisms, we found that the colorectal cancer risk associated with regular nonsteroidal anti-inflammatory drug use was statistically significantly modified by the TP53 genotype (P values for interaction=0.049 and 0.034, respectively), whereby a substantial protective effect of nonsteroidal anti-inflammatory drug use was observed for homozygous carriers of the 72Arg allele and of the PIN3 A1 allele (odds ratio 0.44; 95% confidence interval, 0.30-0.65 and odds ratio, 0.45; 95% confidence interval, 0.31-0.65). The interaction between nonsteroidal anti-inflammatory drugs and TP53 genetic polymorphisms was confirmed by haplotype analysis.

CONCLUSIONS

These data suggest that the TP53 genotype may modify the influence of nonsteroidal anti-inflammatory drug use on the risk of colorectal cancer. A direct proof of functional analysis is warranted to confirm these findings.

Common Genetic Variation in TP53 Is Associated with Lung Cancer Risk and Prognosis in African Americans and Somatic Mutations in Lung Tumors

Lung cancer is primarily caused by tobacco smoking, but susceptibility is likely modified by common genetic variation. In response to many forms of cellular stress, including DNA damage, the p53 protein functions to induce cell cycle arrest, DNA repair, senescence, or apoptosis. We hypothesized that common TP53 haplotypes modulate pathways of lung carcinogenesis and lung cancer susceptibility or prognosis. To investigate our hypothesis, 14 polymorphisms in TP53, including haplotype tagging and coding single nucleotide polymorphisms, were genotyped in two studies from the greater Baltimore, Maryland area. One study is a case-control study and the second is a case-only study for which TP53 mutational spectra data are available. African Americans with Pro-T-A-G-G haplotypes of the combined TP53 polymorphisms TP53_01 (rs1042522), TP53_65 (rs9895829), TP53_66 (rs2909430), TP53_16 (rs1625895), and TP53_11 (rs12951053) had both an increased risk for lung cancer (odds ratio, 2.32; 95% confidence interval, 1.18-4.57) and a worsened lung cancer prognosis (hazards ratio, 2.38; 95% confidence interval, 1.38-4.10) compared with those with Arg-T-A-G-T haplotypes. No associations of TP53 polymorphisms with lung cancer were observed in Caucasians. In the case-only study, several polymorphisms in TP53 and TP53 haplotypes, overlapping regions of TP53 associated with risk and prognosis in African Americans, were associated with increased odds of somatic TP53 mutation in lung tumors in Caucasians. In conclusion, common genetic variation in TP53 could modulate lung cancer pathways, as suggested by the association with lung cancer in African Americans and somatic TP53 mutation frequency in lung tumors.

Linkage of TP53 codon 72 pro/pro genotype as predictive factor for nasopharyngeal carcinoma development

Genetic predisposition has been suggested as a cofactor for cancer aetiology and a polymorphism in TP53 codon 72 has been associated as a susceptibility factor for several cancers. Nasopharyngeal carcinoma is a rare neoplasia in western civilizations and genetic predisposition might play an important role in its development. We evaluated the linkage of the polymorphic variants (Arg/Pro) on TP53 codon 72 with nasopharyngeal cancer development in a case-control study with 392 individuals from a northern Portuguese population, including 107 patients with nasopharyngeal carcinoma and 285 healthy controls. This study revealed a three-fold risk for carriers of Pro/Pro genotype either against carriers of Arg/Arg (OR=2.62; 95% CI=1.10-6.30; P=0.016) or total Arg carriers (OR=2.67; 95% CI=1.21-5.90; P=0.012). Moreover, step-wise logistic regression analysis identified Pro/Pro genotype (OR=3.1; 95% CI=1.3-7.3; P=0.009), age >49 at diagnosis (OR=2.5; 95% CI=1.6-4.0; P<0.001) and male gender (OR=2.7; 95% CI=1.6-4.4; P<0.001) as predictive factors for the development of nasopharyngeal carcinoma. These results confirm the data from Asiatic populations suggesting that Pro/Pro genotype represents a stable risk factor for nasopharyngeal carcinoma development in Portugal and that TP53 codon 72 polymorphism can contribute as a genetic susceptibility marker, providing additional information to improve the knowledge about nasopharyngeal carcinoma aetiology.

The additive effect of p53 Arg72Pro and RNASEL Arg462Gln genotypes on age of disease onset in Lynch syndrome patients with pathogenic germline mutations in MSH2 or MLH1

p53 and the prostate-cancer-susceptibility gene RNASEL are tumour suppressor genes involved in apoptosis. We have previously reported that the common, functionally different variants Arg72Pro in p53 and Arg462Gln in RNASEL are associated with the age of disease onset of colorectal cancer in Lynch syndrome patients. To assess the combined effect of both variants, we screened 246 unrelated Lynch syndrome patients with a pathogenic germline mutation either in MSH2 (n=138) or in MLH1 (n=108) and colorectal cancer as first tumour, and 245 healthy controls. The global log rank test revealed significant differences in the age of disease onset for the genotypes of each variant (p=0.0176 for p53 and p=0.0358 for RNASEL) and for the combined genotypes of both variants (p=0.0174). The highest difference in median age of disease onset was seen between homozygotes for the wild-types in both genes (42years [range 22-75]) and homozygotes for the variant alleles in both genes (30years [range 26-47]). A multivariate Cox regression model indicated that only the p53 and RNASEL genotypes had a significant influence on age of disease onset (p=0.016 for p53 and p=0.014 for RNASEL) in an additive mode of inheritance, and that the effects of both variants are purely additive, which supports the notion that the p53 and RNaseL pathways do not interact. These findings may be relevant for preventive strategies in Lynch syndrome.

An increased lung cancer risk associated with codon 72 polymorphism in the TP53 gene and human papillomavirus infection in Mazandaran province, Iran

The TP53 gene has a polymorphism in exon 4 at codon 72 that presents the arginine or proline genotype. The association of TP53 codon 72 polymorphism with lung cancer risk has been studied by several groups, although with inconsistent results. Our previous study showed that the human papillomavirus (HPV) infection is associated with the development of lung cancer in Mazandaran, north part of Iran (cases=25.6% versus controls=9.0%, P=0.002). The frequency of TP53 codon 72 polymorphism was studied in a north part Iranian group of 92 healthy controls and 141 lung cancer patients. The allelic distribution of the three genotypes (ArgArg, ArgPro, ProPro) in healthy normal controls was 46.1, 32.6 and 21.3%, respectively, which differs from that of lung cancer patients showing genotype frequency as 42.6, 49.6 and 7.8%. A relation between the presence of the Arg allele and lung cancer risk was observed. Our study reveals that Arg allele, active smoking and HPV infection are the important risk factors in lung cancer development in the north part of Iran, Mazandaran province.

p53 genotypes and haplotypes associated with risk of breast cancer

INTRODUCTION

The biological significance of sequence variants in form of SNPs needs to be carefully evaluated, as conflicting associations with cancer predisposition have been reported. Haplotypes, the combination of closely linked alleles on a chromosome, play key roles in the study of the genetic basis of disease. There is strong evidence that different polymorphisms within a single gene in cis position can interact to create a large effect on the observed phenotype. Several polymorphisms have been reported in the p53 gene. Some of these are within the coding region and may affect the function of the p53 protein, others are within introns or non-coding regions, and their significance is unclear. In this study, we investigated the association of specific p53 genotypes and haplotypes with risk of breast cancer.

METHODS

One hundred and fifteen patients with breast cancer and 63 healthy individuals were analyzed. DNA was isolated by salting out. The polymorphic sites were analyzed by PCR RFLP. Pearson's chi(2) and Kolmogorof Simirnow tests were used for statistical analyses. Extended haplotype frequencies were estimated.

RESULTS

The distribution of the genotypes was similar for all three polymorphisms in the cases and the controls. Our estimated haplotype results indicate that the intron 3 (+16bp)|exon 4 (Arg) diplotype and the intron 3 (+16bp)|exon 4 (Arg)|intron 6 (G) haplotype combinations are overrepresented in the breast cancer group, suggesting that the intron 3 (+16bp)|exon 4 (Arg) alleles may play a role in breast carcinogenesis.

CONCLUSION

We conclude that two haplotypes harboring the intron 3 polymorphic (+16bp) allele are associated with a higher risk of breast cancer in the Turkish population.

Single tube genotyping of GSTM1, GSTT1 and TP53 polymorphisms by multiplex PCR

Glutathione S-transferases (GST) are enzymes involved in the conjugation of a number of human carcinogens, while p53 tumour suppressor gene is the most frequently mutated gene identified till now in human neoplasias. Typically, GSTM1 and GSTT1 genotyping are performed together, with several different protocol described and sometimes with the risk of misclassification due to "false negative", depending on the internal positive control employed. Here, we report a modification of the classical multiplex polymerase chain reaction (PCR) method, allowing the genotyping of GSTM1, GSTT1, together with a polymorphism within the intron 3 of TP53 tumour suppressor gene (a 16 base pairs (bp) duplication) in a single tube, with an appropriate internal positive control. To test the applicability of the method, the frequencies of the deleted alleles of GSTM1 and GSTT1 (null genotypes), and the 16 bp duplication of TP53 gene were assayed in a series of Caucasian DNA samples.

Association of specific p53 polymorphisms with keratosis in individuals exposed to arsenic through drinking water in West Bengal, India

Although, more than six million people are endemically exposed to inorganic arsenic in West Bengal, India by drinking heavily contaminated groundwater, only about 300,000 people show arsenic induced skin lesions. This suggests that genetic variability plays an important role in arsenic induced skin lesions and skin cancers. Arsenic induced keratosis is considered as a possible precancerous state of in situ carcinoma. Several reports have suggested the role of p53 polymorphisms as potential marker for risk assessment of different types of cancers. This prompted us to study the association of three p53 polymorphisms with arsenic induced keratosis in a population exposed to arsenic through drinking water. A total of 366 unrelated individuals (177 individuals with arsenic induced keratosis and 189 individuals with no arsenic induced skin lesions) were recruited from North 24 Parganas, Nadia and Murshidabad districts between January 2003 and February 2005 for the study of the genotypic distribution of three p53 polymorphisms (16bp duplication at intron 3, codon 72 Arg/Pro and G>A at intron 6 [nt 13,494]) by PCR-RFLP. The arginine homozygous genotype at codon 72, and homozygous genotype of no duplication polymorphism at intron 3 were over represented in the individuals with keratosis compared with individuals with no skin lesions (OR=2.086; 95% CI=1.318-3.299 and OR=2.086; 95% CI=1.257-3.457, respectively). This study indicates that individuals carrying the arginine homozygous genotype at codon 72, and/or no duplication homozygous genotype at intron 3 are at risk for the development of arsenic induced keratosis.

A haplotype containing the p53 polymorphisms Ins16bp and Arg72Pro modifies cancer risk in BRCA2 mutation carriers

Germline mutations in the BRCA1 and BRCA2 genes confer a high lifetime risk of developing breast and other cancers; however, remarkable differences exist regarding disease manifestation in mutation carriers. It has been suggested that other genetic and/or environmental factors modify not only the appearance but also the age of onset and type of tumor in BRCA1/2-associated cases. The aim of the present study was to investigate the role of two p53 polymorphisms (c.97-147ins16bp and c.215c>g, p.Arg72Pro) as potential modifiers. For this purpose we investigated the possible association between the two polymorphisms and disease status in 447 BRCA1/2 mutation carriers belonging to 170 Spanish breast and/or ovarian cancer families. Genotype and haplotype analyses revealed that the presence of a specific haplotype carrying the allele without the 16-bp insertion and the variant allele for the Arg72Pro (No Ins-72Pro haplotype) was associated with an earlier age of onset in BRCA2 mutation carriers. We found an increased risk of developing a first primary tumor (breast or ovarian) before 35 years of age for individuals who carried at least one No Ins-72Pro haplotype (OR: 2.69; 95% CI: 1.15-6.29; P=0.022). We confirmed these data by a functional study in which we compared different p53 genotypes in relation to their apoptotic response after cell treatment with a cytotoxic drug (AraC). Our results revealed a decrease in p53 apoptotic rate associated with the No Ins-72Pro haplotype.

Role of glutathione-S-transferase and codon 72 of P53 genotypes in epithelial ovarian cancer patients

PURPOSE

A series of polymorphisms in germ-line DNA have been investigated in an effort to delineate polygenic models of cancer susceptibility and prognosis. As low-penetrance susceptibility genes may combine additively or multiplicatively and contribute to cancer incidence and to the response to chemotherapy, we studied GSTT1, GSTM1, GSTO2, GSTP1 and codon 72 of p53 genotype profiles in ovarian cancer patients.

METHODS

We compared 69 ovarian cancer patients with 222 control healthy women paired for ethnic and life-style characteristics. Outcome was evaluated in 29 stage III and IV patients submitted to a platinum-based chemotherapy followed-up for 6-29 months (17 +/- 9 months).

RESULTS

GSTT1, GSTM1, GSTO2 and GSTP1 genes presented a similar genotype distribution, but codon 72 of p53 gene wild-type variant was less frequent in ovarian cancer patients than in controls (chi(2); P = 0.0004).

CONCLUSIONS

We were unable to demonstrate any association between the GST genotypes studied and the risk of ovarian cancer but the inheritance of a heterozygous Arg/Pro genotype of p53 increased the risk of ovarian cancer more than 2.5 times (OR = 2.571; 95% CI = 1.453-4.550). There was no association of the studied genes to any clinical or pathological feature of the patients or to their response to chemotherapy.

Increased risk of non-small cell lung cancer and frequency of somatic TP53 gene mutations in Pro72 carriers of TP53 Arg72Pro polymorphism

The aim of this study was to assess whether the TP53 Arg72Pro polymorphism is associated with an increased risk of non-small cell lung cancer (NSCLC). Additionally, in NSCLC patients, we investigated a potential association between this polymorphism and somatic TP53 gene mutations in tumour cells. The study group included 240 NSCLC patients who underwent curative pulmonary resection. The control group (576 healthy subjects) was matched for sex and cigarette smoking. TP53 Arg72Pro polymorphism was determined by denaturing high-performance liquid chromatography. Tumours from 157 NSCLC patients were analysed for mutation in TP53 exons 5-8 by single strand conformation polymorphism, followed by sequencing of samples with different band pattern. Tumours from the remaining 83 patients were subjected to a direct sequencing of TP53 exons 5-8. The proportion of Pro homo/heterozygotes versus Arg homozygotes was significantly higher in NSCLC patients (54%) than in controls (46%, p = 0.034). The crude odds ratio for NSCLC development in Pro72 allele carriers was 1.39 (95% CI: 1.03-1.88). When adjusted for sex, age and smoking status in the multivariate logistic regression model, odds ratio for NSCLC development was 1.28 (95% CI: 0.91-1.80). Somatic TP53 mutations were found in 62 out of 240 NSCLC patients (26%), more frequently in Pro carriers (31%) than in Arg homozygotes (20%, p = 0.06). These results indicate that the TP53 codon 72 Pro allele may increase the risk of NSCLC. Additionally, the correlation between Pro72 and somatic TP53 mutations suggests that Pro72 allele carriers may be predisposed to tumour development along a p53 associated form of NSCLC, a finding that warrants further investigations.

Infection of human papillomavirus type 18 and p53 codon 72 polymorphism in lung cancer patients from India

STUDY OBJECTIVES

Infection with specific high-risk HPV types 16 and 18 and polymorphism of p53 codon 72 has been strongly associated with the genesis of various neoplasms in humans, but such study in lung cancer is limited and the results are controversial. In India, the role of these two factors has been strongly implicated in cervical and other cancers, but the occurrence of HPV or p53 codon 72 polymorphism has not been examined in lung cancer, which is the most common cause of cancer-related death in India.

DESIGN AND PATIENTS

A total of 40 tumor biopsy specimens from advanced lung cancer patients and blood samples from 40 matching control subjects were obtained for the analysis of high-risk HPV types 16 and 18 infection and p53 codon 72 polymorphism by polymerase chain reaction.

RESULTS

Only HPV type 18 was detected in 5% (2 of 40 lung cancer patients), but no other HPV could be detected. A significantly increased frequency of Arg/Arg homozygotes was observed in patients with advanced lung cancer when compared to that of control subjects (p = 0.004; odds ratio, 5.13; 95% confidence interval, 1.59 to 17.26). However, no significant correlation could be made between p53 polymorphism and different clinical stages, except for advanced stage IV patients, who showed a higher proportion of Arg/Pro heterozygous genotype.

CONCLUSIONS

HPV detected in a small proportion of lung cancer patients in India demonstrated an exclusive prevalence of HPV type 18, and there was a significantly higher frequency of p53 Arg/Arg genotype when compared to that of control subjects. Observation of a shorter duration of symptoms (< or = 4 months) in as many as 78% (seven of nine stage IV patients) with Arg/Pro genotype may be an indication that lung cancer patients with the heterozygous p53 genotype are more susceptible to early progression.

Risk assessment of p53 genotypes and haplotypes in tobacco-associated leukoplakia and oral cancer patients from eastern Idia

The role of 3 p53 polymorphisms (16 bp duplication at intron 3, codon 72 Arg/Pro and intron 6 NciI RFLP at np 13494) as potential markers for indicating cancer risk remains inconclusive. In our case-control study consisting of 197 leukoplakia and 310 oral squamous cell carcinoma (SCC) patients and 348 controls, genotype frequencies at these 3 p53 loci were determined by PCR-RFLP method and analyzed by multiple logistic regression to determine the risks of the diseases. The 2/2 genotype at codon 72 of p53 was at risk for developing leukoplakia (OR = 1.6, 95% CI 1.1-2.3), whereas the combination of 1/2 and 2/2 genotypes at intron 3 and 1/1 and 1/2 genotypes at intron 6 conferred a protective effect against leukoplakia and oral SCC development, respectively (OR = 0.5, 95% CI 0.4-0.8 and OR = 0.6, 95% CI 0.5-0.9, respectively). When subjects were stratified according to specific tobacco habit, the risk/protection estimates improved significantly in some cases. Specifically, the exclusive smokers with p53 codon 72 2/2 genotype showed a higher risk of developing leukoplakia (OR = 2.7, 95% CI 1.2-6.3). Furthermore, a particular p53 haplotype 1-2-2 was at risk for both tobacco-associated leukoplakia and oral SCC (OR = 1.5, 95% CI 1.1-1.9 and OR = 1.3, 95% CI 1.1-1.7, respectively). Our results show that both specific p53 genotype and haplotype can indicate risk of tobacco-associated leukoplakia, but risk of development of tobacco-associated oral SCC can be predicted by specific p53 haplotype only.

The p53 codon 72 proline allele is associated with p53 gene mutations in non-small cell lung cancer

The p53 gene plays a critical role in cell cycle control, the initiation of apoptosis, and in DNA repair. An Arg/Pro polymorphism at codon 72 of the p53 gene alters the ability of the p53 protein to induce apoptosis, influences the behavior of mutant p53, decreases DNA repair capacity, and may be linked with an increased risk of lung cancer. To further define the role of the p53 codon 72 polymorphism on DNA repair, lung cancer risk, and mutant p53 function, we examined the effect of this polymorphism on mutation of the p53 gene and patient survival in non-small cell lung cancer (NSCLC). Tumor and nonneoplastic (lung or lymphocyte) samples were collected from 182 patients with NSCLC. p53 mutations were detected by direct sequencing and/or the Gene Chip p53 assay in 93 of 182 (51%) tumors. p53 codon 72 polymorphisms were identified by PCR/RFLP analysis. p53 mutations were significantly (P = 0.01) associated with the number of codon 72 Pro alleles: Pro/Pro homozygotes, 17 of 26 (65%); Arg/Pro heterozygotes, 45 of 79 (57%); and Arg/Arg homozygotes, 31 of 77 (40%). The number of codon 72 Pro alleles was independently associated with p53 mutations (odds ratio, 1.97; 95% confidence interval, 1.14-3.40; P = 0.01) in a multiple logistic regression model. The codon 72 polymorphism did not influence patient survival in either the entire patient group or among patients with p53 mutant tumors. In summary, the p53 Pro allele is associated with an increased frequency of p53 mutations in NSCLC.

Differential gene expression in normal human mammary epithelial cells treated with malathion monitored by DNA microarrays

Organophosphate pesticides are a major source of occupational exposure in the United States. Moreover, malathion has been sprayed over major urban populations in an effort to control mosquitoes carrying West Nile virus. Previous research, reviewed by the U.S. Environmental Protection Agency, on the genotoxicity and carcinogenicity of malathion has been inconclusive, although malathion is a known endocrine disruptor. Here, interindividual variations and commonality of gene expression signatures have been studied in normal human mammary epithelial cells from four women undergoing reduction mammoplasty. The cell strains were obtained from the discarded tissues through the Cooperative Human Tissue Network (sponsors: National Cancer Institute and National Disease Research Interchange). Interindividual variation of gene expression patterns in response to malathion was observed in various clustering patterns for the four cell strains. Further clustering identified three genes with increased expression after treatment in all four cell strains. These genes were two aldo-keto reductases (AKR1C1 and AKR1C2) and an estrogen-responsive gene (EBBP). Decreased expression of six RNA species was seen at various time points in all cell strains analyzed: plasminogen activator (PLAT), centromere protein F (CPF), replication factor C (RFC3), thymidylate synthetase (TYMS), a putative mitotic checkpoint kinase (BUB1), and a gene of unknown function (GenBank accession no. AI859865). Expression changes in all these genes, detected by DNA microarrays, have been verified by real-time polymerase chain reaction. Differential changes in expression of these genes may yield biomarkers that provide insight into interindividual variation in malathion toxicity.

Mutation and homozygous deletion analyses of genes that control the G1/S transition of the cell cycle in skin melanoma: p53, p21, p16 and p15

INTRODUCTION

The role of genes involved in the control of progression from the G1 to the S phase of the cell cycle in melanoma tumors is not fully known.

MATERIAL AND METHODS

The aims of our study were to analyse alterations in p53, p21, p16 and p15 genes in melanoma tumors and melanoma cell lines by single strand conformational polymorphism (SSCP), and to detect homozygous deletions. We analysed the DNA from 39 patients with primary and metastatic melanomas, and from 9 melanoma cell lines.

RESULTS

The SSCP technique showed heterozygous defects in the p53 gene in 8 of 39 (20.5%) melanoma tumors: three point mutations in intron sequences (introns 1 and 2) and exon 10, and three new polymorphisms located in introns 1 and 2 (C to T transition at position 11701 in intron 1; C insertion at position 11818 in intron 2; and C insertion at position 11875 in intron 2). One melanoma tumor exhibited two heterozygous alterations in the p16 exon 1 (stop codon and missense mutation). No defects were found in the remaining genes. Homozygous deletions were more frequent in melanoma cell lines than in melanoma tumors in p21, p16 and p15 (22.2%, 44.4%, and 44.4% versus 7.7%, 2.5%, and 5.1% respectively). TP53 did not show homozygous deletions.

CONCLUSIONS

Our results suggest that these genes are involved in melanoma tumorigenesis; but perhaps not in the major targets. Other suppressor genes that may be informative of the mechanism of tumorigenesis in skin melanomas need to be studied.

Mutation analysis of genes that control the G1/S cell cycle in melanoma: TP53, CDKN1A, CDKN2A, and CDKN2B

Background

The role of genes involved in the control of progression from the G1 to the S phase of the cell cycle in melanoma tumors in not fully known. The aim of our study was to analyse mutations in TP53, CDKN1A, CDKN2A, and CDKN2B genes in melanoma tumors and melanoma cell lines

Methods

We analysed 39 primary and metastatic melanomas and 9 melanoma cell lines by single-stranded conformational polymorphism (SSCP).

Results

The single-stranded technique showed heterozygous defects in the TP53 gene in 8 of 39 (20.5%) melanoma tumors: three new single point mutations in intronic sequences (introns 1 and 2) and exon 10, and three new single nucleotide polymorphisms located in introns 1 and 2 (C to T transition at position 11701 in intron 1; C insertion at position 11818 in intron 2; and C insertion at position 11875 in intron 2). One melanoma tumor exhibited two heterozygous alterations in the CDKN2A exon 1 one of which was novel (stop codon, and missense mutation). No defects were found in the remaining genes.

Conclusion

These results suggest that these genes are involved in melanoma tumorigenesis, although they may be not the major targets. Other suppressor genes that may be informative of the mechanism of tumorigenesis in skin melanomas should be studied.

Homozygosity for Pro of p53 Arg72Pro as a potential risk factor for hepatocellular carcinoma in Chinese population

AIM: Codon 72 exon 4 polymorphism (Arg72Pro) of the p53 gene has been implicated in cancer risk. Our objective was to investigate the possible association between p53 Arg72Pro polymorphism and susceptibility to hepatocellular carcinoma (HCC) among Chinese population.

METHODS: The p53 Arg72Pro genotypes were determined by PCR-based restriction fragment length polymorphism (RFLP) analysis in 507 HCC cases and 541 controls. Odds ratios (ORs) for HCC and 95% confidence intervals (CIs) from unconditional logistic regression models were used to evaluate relative risks. Potential risk factors were included in the logistic regression models as covariates in the multivariate analyses on genotype and HCC.

RESULTS: The frequencies for Pro and Arg alleles were 44.5%, 55.5% in HCC cases, and 40.3% and 59.7% in controls, respectively. The Pro allele was significantly associated with the presence of HCC (P = 0.05) and had a higher risk for HCC (OR = 1.19, 95% CI 1.00-1.41) as compared with the Arg allele. After adjusted for potential risk factors, Arg/Pro heterozygotes had an 1.21-fold increased risk (95% CI 0.82-1.78, P = 0.34) of HCC compared with Arg homozygotes, whereas the risk for Pro homozygotes was 1.79 (95% CI 1.06-3.01, P = 0.03) times higher than that for Arg homozygotes. Pro-allele carriers had a higher relative risk of HCC than the Arg-only carriers (adjusted OR = 1.33, 95% CI 0.92-1.92, P = 0.13), although the difference was not statistically significant.

CONCLUSION: Homozygosity for Pro of p53 Arg72Pro is potentially one of the genetic risk factors for HCC in Chinese population. The p53 Arg72Pro polymorphism may be used as a stratification marker in screening individuals at a high risk of HCC.

Estrogen receptor, progesterone receptor, and bcl-2 are markers with prognostic significance in CIN III

There are no known biological markers or technologies to predict the natural history of an individual CIN III. The probability of progression is considered greater with the persistence of high-risk human papillomavirus (HPV) infection and age. p53 polymorphism has been associated with cervical carcinogenesis. Hormone-induced cervical cancer is mediated by estrogen receptor (ER) and progesterone receptor (PR). In cervical cancer, increased bcl-2 and Bax immunoreactivity is generally associated with a better prognosis. The purpose of this study was to evaluate the value of HPV 16 and HPV 18 typing and p53 codon polymorphism genotyping by polymerase chain reaction and ER, PR, bcl-2, and Bax expression by immunohistochemistry in predicting the CIN III clinical behavior of CIN III lesions. We studied the expression of these prognostic factors in the CIN III adjacent to squamous cell microinvasive carcinomas of the cervix (MIC) from 29 patients with FIGO stage IA1 cervical cancer and in 25 patients with CIN III and no documented focus of invasion. In the MIC group, only the CIN III was considered at least 2 mm away from the microinvasive complex. The ER, PR, bcl-2, and Bax immunoreactivity was scored as positive (>10% staining cells) and negative (<10% staining cells). No significant difference was observed between MIC and CIN III group concerning HPV infection and p53 polymorphism. The ER, PR, bcl-2, and Bax immunohistochemical expression was stronger and more frequent in the CIN III group. After multivariable analysis, coexpression of ER, PR, and bcl-2 was the only independent factor in defining low risk of progression for CIN III. Our study suggests that coexpression of ER, PR, and bcl-2 may be a useful tool in identifying the CIN III lesions with low risk of progression to cervical cancer.

The effect of oxythioquinox exposure on normal human mammary epithelial cell gene expression: a microarray analysis study

BACKGROUND

Inter-individual variation in normal human mammary epithelial cells in response to oxythioquinox (OTQ) is reported. Gene expression signatures resulting from chemical exposures are generally created from analysis of exposures in rat, mouse or other genetically similar animal models, limiting information about inter-individual variations. This study focused on the effect of inter-individual variation in gene expression signatures.

METHODS

Gene expression was studied in primary normal human mammary epithelial cells (NHMECs) derived from four women undergoing reduction mammoplasty [Cooperative Human Tissue Network (National Cancer Institute and National Disease Research Interchange)]. Gene transcription in each cell strain was analyzed using high-density oligonucleotide DNA microarrays (HuGeneFL, Affymetrix) and changes in the expression of selected genes were verified by real-time polymerase chain reaction at extended time points (ABI). DNA microarrays were hybridized to materials prepared from total RNA that was collected after OTQ treatment for 15, 60 and 120 min. RNA was harvested from the vehicle control (DMSO) at 120 min. The gene expression profile included all genes altered by at least a signal log ratio (SLR) of +/- 0.6 and p value < or = 0.05 in three of four cell strains analyzed.

RESULTS

RNA species were clustered in various patterns of expression highlighting genes with altered expression in one or more of the cell strains, including metabolic enzymes and transcription factors. Of the clustered RNA species, only 36 were found to be altered at one time point in three or more of the cell strains analyzed (13 up-regulated, 23 down-regulated). Cluster analysis examined the effects of OTQ on the cells with specific p53 polymorphisms. The two strains expressing the major variant of p53 had 83 common genes altered (35 increased, 48 decreased) at one or more time point by at least a 0.6 signal log ratio (SLR). The intermediate variant strains showed 105 common genes altered (80 increased, 25 decreased) in both strains.

CONCLUSION

Differential changes in expression of these genes may yield biomarkers that provide insight into inter-individual variation in cancer risk. Further, specific individual patterns of gene expression may help to determine more susceptible populations.

Prognostic value of TP53 codon 72 polymorphism in advanced gastric adenocarcinoma

PURPOSE

A common polymorphism of the tumor suppressor gene TP53 at codon 72 has been associated with human cancer susceptibility. The prognostic role of the polymorphism was assessed in 102 patients with advanced gastric adenocarcinoma.

EXPERIMENTAL DESIGN

We followed up 102 consecutive Caucasian patients with advanced gastric adenocarcinoma for >5 years and determined the status of the TP53 codon 72 polymorphism in DNA samples extracted from archived gastric tissues.

RESULTS

The frequency of the arginine homozygous allele was positively correlated to patient age at baseline (P = 0.002). However, the age-related increase in the percentage of codon 72 arginine p53 was not correlated to the prognosis for gastric cancer patients. Multivariable analysis in patients who had surgery showed that baseline age may be inversely associated with patient survival (odds ratio, 1.1; 95% confidence interval, 1.0-1.2; P = 0.02). Furthermore, alcohol consumption may be associated with reduced survival (P = 0.06).

CONCLUSIONS

These findings indicate that codon 72 arginine p53 may not be associated with a prolonged survival in patients with advanced gastric adenocarcinoma, but further study is needed to assess whether this polymorphism is associated with a late onset or slow progress of early gastric adenocarcinoma.

P53 (codon 72) and P21 (codon 31) polymorphisms alter in vivo mRNA expression of p21

p21 (Waf1/Cip1) is a downstream target of p53. We evaluated the association between p21 polymorphism (codon 31), p53 polymorphism (codon 72) and their corresponding in vivo mRNA expression. In this study, p21 and p53 genetic polymorphisms (using standard PCR-RFLP techniques) and p21 and p53 gene expressions (using a radiolabelled ribonuclease protection assay (RPA) technique) were evaluated in the peripheral leukocytes of 84 individuals (63 with lung cancer). Log-transformed values of mRNA expression by RPA, which approximated a normal distribution, were analyzed. p53 genotypes did not correlate with p53 mRNA log-expression (P>0.05 for all comparisons), but the Pro allele variants of p53 were associated with a significant decrease in mRNA log-expression of its downstream target, p21. The variant Arg allele of p21 was also associated with a significant decrease in p21 mRNA log-expression. When individuals with at least one variant allele of both p53 and p21 (double-variants) were compared with all other genotype groups, these double-variants had significantly lower log-expression of p21 (P<0.005 by both t-tests (crude) and linear regression analyses (adjusted)). This is translated into an approximate 48% reduction in the geometric mean of the mRNA expression of the double-variants, when compared with all other groups. Results were consistent in both patients with lung cancer (n=63) and in normal controls (n=21). In conclusion, the presence of a p53 Pro allele and/or p21 Arg allele is associated with lower downstream target gene expression of p21.