The different apoptotic potential of the p53 codon 72 alleles increases with age and modulates in vivo ischaemia-induced cell death

A common arginine to proline polymorphism is harboured at codon 72 of the human p53 gene. In this investigation, we found that fibroblasts and lymphocytes isolated from arginine allele homozygote centenarians and sexagenarians (Arg+) undergo an oxidative-stress-induced apoptosis at a higher extent than cells obtained from proline allele carriers (Pro+). At variance, the difference in apoptosis susceptibility between Arg+ and Pro+ is not significant when cells from 30-year-old people are studied. Further, we found that Arg+ and Pro+ cells from centenarians differ in the constitutive levels of p53 protein and p53/MDM2 complex, as well as in the levels of oxidative stress-induced p53/Bcl-xL complex and mitochondria-localised p53. Consistently, all these differences are less evident in cells from 30-year-old people. Finally, we investigated the in vivo functional relevance of the p53 codon 72 genotype in a group of old patients (66-99 years of age) affected by acute myocardial ischaemia, a clinical condition in which in vivo cell death occurs. We found that Arg+ patients show increased levels of Troponin I and CK-MB, two serum markers that correlate with the extent of the ischaemic damage in comparison to Pro+ patients. In conclusion, these data suggest that p53 codon 72 polymorphism contributes to a genetically determined variability in apoptotic susceptibility among old people, which has a potentially relevant role in the context of an age-related pathologic condition, such as myocardial ischaemia.     

p53 codon 72 genotype affects apoptosis by cytosine arabinoside in blood leukocytes

A wide difference in the susceptibility to undergo in vitro apoptosis exists among individuals, and this fact has potential implications in predicting the in vivo response to apoptotic agents, such as those employed in chemotherapy. In this report, we addressed the question whether the natural variability at p53 locus (the proline-arginine substitution at codon 72) affects the capacity of peripheral-blood mononuclear cells from healthy subjects to undergo in vitro apoptosis in response to the cytotoxic drug cytosine arabinoside. We found that cells from subjects carrying the arginine/arginine genotype undergo in vitro apoptosis at a higher extent in comparison to those from arginine/proline subjects. This finding suggests that naturally occurring genetic variability at p53 gene explains part of the inter-individual difference in the in vitro susceptibility to a chemotherapeutic drug, thus resulting as an eligible predictor marker of in vivo response to chemotherapy and its adverse effects.     

Glutathione S-transferase GSTM1, GSTT1 and p53 codon 72 polymorphisms in human tumor cells

The genes of the glutathione S-transferase (GST) family encode enzymes that appear to be critical in cellular protection against the cytotoxic effects, whereas p53 is a tumor suppressor gene. Despite a large number of studies on germline polymorphisms of GSTM1, GSTT1 and p53 genes, there have been very few reports on genotyping of these genes in human malignant tumor cells. In this study, we investigated GSTM1, GSTT1 and p53 codon 72 polymorphisms in a variety of human tumor cell lines originating from different organs to clarify tissue-specific polymorphic frequency of these genes in human solid tumors. The GSTM1 and GSTT1 genetic polymorphisms were evaluated using multiplex PCR techniques and PCR-RFLP analysis was conducted to identify p53 codon 72 genotypes. Gene expression of GSTM1 or GSTT1 was detected by RT-PCR in the cells with respective present genotype for each. Polymorphisms of p53 codon 72 detected by PCR-RFLP were also confirmed using SSCP and sequence analyses. GSTM1 and GSTT1 genotypes were various in 104 cell lines examined. Null GSTM1 genotype was dominant in small cell lung, kidney and ovarian carcinoma cells, whereas null GSTT1 genotype was dominant in cervical and endometrial carcinoma cells. GSTM1 and GSTT1 genotypes in ovarian carcinoma cells were quite similar to those in small cell lung carcinoma cells. Polymorphic frequency of p53 codon 72 was also various among the cells, however, the Pro allele was found in only 1 of 6 kidney, 14 cervical and 4 endometrial carcinoma cell lines. There was a significant difference in GSTM1 and p53 genotypes between 34 small cell and 24 non small cell lung carcinoma cells (P < 0.01). Combined study on the distribution of GSTM1, GSTT1 and p53 genotypes revealed that null GSTM1 genotype was associated with the Arg allele of p53 codon 72 in 58 lung carcinoma cells and null GSTT1 genotype was associated with the Pro/Pro homozygote in 104 tumor cell lines examined. This is the first study examining GSTM1, GSTT1 and p53 codon 72 polymorphisms in a variety of human solid tumor cells and suggesting that polymorphic frequency of these genes may be tissue- and organ-specific. The molecular interaction between GST gene defects and p53 codon 72 genotype in the development of human malignant tumors should be further investigated.     

Influence of Arg72Pro polymorphisms of TP53 on the response of buccal cells to radiotherapy

Polymorphisms in the TP53 gene codon 72 (Arg72Pro) influence apoptosis induction and DNA damage repair. We evaluated how variants of protein p53 (p53Arg and p53Pro) affect cell death and DNA damage repair by analyzing the frequencies of karyorrhexis and micronuclei. There were significant differences in the frequency of karyorrhexis between the three p53 genotypes (Arg/Arg, Arg/Pro, and Pro/Pro), between samples taken before and after radiotherapy, and between patients and controls. The frequency of micronucleated cells increased significantly after radiotherapy. There were no significant differences in the micronucleus frequency in healthy tissues of these patients compared to controls, or in the comparisons between the three genotypes. We conclude that Arg72Pro polymorphism influences cell apoptotic capacity. This is the first study investigating karyorrhexis and micronuclei, as indicators of apoptosis after radiotherapy, and how these indicators are influenced by the TP53 polymorphism Arg72Pro.     

P53 codon 11, 72, and 248 gene polymorphisms in endometriosis

OBJECTIVE: Mutated p53 gene is related to the instability of cell growth and cell cycle progression. We aimed to evaluate the association between endometriosis and p53 codon 11, 72 and 248 gene polymorphisms.PATIENTS AND METHODS: Women were divided into two groups: (1) moderate/severe endometriosis (n=148), and (2) non-endometriosis groups (n=150). P53 gene polymorphisms include codon11 Glu/Gln or Lys (GAG->CAG or AAG), codon 72 Arg/Pro (CGC->CCC), and codon 248 Arg/Thr (CGG->TCG). These gene polymorphisms were amplified by polymerase chain reaction and detected by electrophoresis after restriction enzyme (Taq I, BstU I, Hap II) digestions. Associations between the endometriosis and p53 polymorphisms were evaluated.RESULTS: The distributions of p53 codon 72 polymorphisms in both groups were significantly different. The proportions of Arg homozygotes/heterozygotes/Pro homozygotes in both groups were 9.5/66.2/24.3% and 30.7/50/19.3%. The proportions of Arg/Pro alleles were 42.6/57.4% and 56/44%. The distributions of p53 codon 11 and 248 polymorphisms in both groups were non-significantly different. All individuals appeared the wild genotypes (Glu11 and Arg248 homozygotes).CONCLUSION: Association between endometriosis and p53 codon 72 polymorphism exists. P53 codon 72*Pro-related genotype and allele are related with higher susceptibility of endometriosis. P53 codon 11 and 248 polymorphisms are not related with endometriosis susceptibility.     

Meta-analysis of an association of codon 72 polymorphisms of the p53 gene with increased endometrial cancer risk

Polymorphisms of the p53 gene have been associated with susceptibility to endometrial cancer. However, whether there is a specific association is still controversial. We investigated a possible association between p53 codon 72 polymorphism and endometrial cancer risk by conducting a meta-analysis. Publications addressing this association were selected from the Pubmed, Embase and CBM databases (up to January 2011). Data were extracted from the studies by two independent reviewers. The meta-analysis was performed using RevMan 5.0.25 and STATA 9.2 softwares. The odds ratio (OR) with 95% confidence intervals (CI) was calculated. Then, 10 case-control studies were retrieved, with a total of 917 endometrial cancer patients and 1680 healthy controls. Meta-analysis results showed that the Pro allele and Pro carrier (Arg/Pro + Pro/Pro) of p53 codon 72 polymorphism were significantly related with endometrial cancer risk (OR = 1.25, 95%CI = 1.10-1.41, P = 0.0005; OR = 1.34, 95%CI = 1.12-1.59, P = 0.001, respectively). In the subgroup analysis, based on ethnicity, studies were divided into Asian and Caucasian populations; the Pro allele and Pro carrier (Arg/Pro + Pro/Pro) of p53 codon 72 polymorphism were significantly related with endometrial cancer risk in Asian populations (OR = 1.41, 95%CI = 1.19-1.66, P < 0.0001; OR = 1.66, 95%CI = 1.30-2.13, P < 0.0001, respectively), but not in Caucasian populations (both P > 0.05). We concluded that the Pro allele (Arg/Pro + Pro/Pro) of p53 codon 72 polymorphism is a potential risk factor for endometrial cancer.     

湖南地区汉族人群p53基因第72位密码子多态性与宫颈鳞癌的相关性

目的：探讨宫颈组织p53基因第72位密码子的多态性及分析第72位密码子的多态性与湖南地区汉族人群宫颈鳞癌的相关性。方法：采用PCR方法扩增101例正常宫颈和150例宫颈鳞癌石蜡组织p53基因第72位密码子基因,回收目的片段进行测序。采用SPSS11．5软件分析p53基因第72位密码子的多态性。结果：p53第72位密码子基因测序结果显示,在宫颈鳞癌组织中Arg／Arg、Pro／Pro、Arg／Pro所占比例分别为40．66％、16．67％、42．67％;在正常宫颈组织中Arg／Arg、Pro／Pro、Arg／Pro所占比例分别为47．53％、7．92％、44．55％。统计学分析结果显示,Arg／Arg和Arg／Pro基因型在宫颈鳞癌和对照组中的表达差异没有统计学意义（P〉0．05）;Pro／Pro基因型在宫颈鳞癌组中所占比例显著高于正常宫颈组织（P〈0．05）。结论：p53基因第72位密码子Pro／pro基因型是湖南地区女性发生宫颈鳞癌易感因素。     

湖南地区汉族人群p53 基因第72 位密码子多态性与宫颈鳞癌的相关性

目的:探讨宫颈组织p53基因第72位密码子的多态性及分析第72位密码子的多态性与湖南地区汉族人群宫颈鳞癌的相关性。方法:采用PCR方法扩增101例正常宫颈和150例宫颈鳞癌石蜡组织p53基因第72位密码子基因,回收目的片段进行测序。采用SPSS 11.5软件分析p53基因第72位密码子的多态性。结果:p53第72位密码子基因测序结果显示,在宫颈鳞癌组织中Arg/Arg、Pro/Pro、Arg/Pro所占比例分别为40.66%、16.67%、42.67%;在正常宫颈组织中Arg/Arg、Pro/Pro、Arg/Pro所占比例分别为47.53%、7.92%、44.55%。统计学分析结果显示,Arg/Arg和Arg/Pro基因型在宫颈鳞癌和对照组中的表达差异没有统计学意义(P>0.05);Pro/Pro基因型在宫颈鳞癌组中所占比例显著高于正常宫颈组织(P<0.05)。结论:p53基因第72位密码子Pro/pro基因型是湖南地区女性发生宫颈鳞癌易感因素。     

Prognostic value of TP53 Pro47Ser and Arg72Pro single nucleotide polymorphisms and the susceptibility to gliomas in individuals from Southeast Brazil

The TP53 tumor suppressor gene codifies a protein responsible for preventing cells with genetic damage from growing and dividing by blocking cell growth or apoptosis pathways. A common single nucleotide polymorphism (SNP) in TP53 codon 72 (Arg72Pro) induces a 15-fold decrease of apoptosis-inducing ability and has been associated with susceptibility to human cancers. Recently, another TP53 SNP at codon 47 (Pro47Ser) was reported to have a low apoptosis-inducing ability; however, there are no association studies between this SNP and cancer. Aiming to study the role of TP53 Pro47Ser and Arg72Pro on glioma susceptibility and oncologic prognosis of patients, we investigated the genotype distribution of these SNPs in 94 gliomas (81 astrocytomas, 8 ependymomas and 5 oligodendrogliomas) and in 100 healthy subjects by the polymerase chain reaction-restriction fragment length polymorphism approach. Chi-square and Fisher exact test comparisons for genotype distributions and allele frequencies did not reveal any significant difference between patients and control groups. Overall and disease-free survivals were calculated by the Kaplan-Meier method, and the log-rank test was used for comparisons, but no significant statistical difference was observed between the two groups. Our data suggest that TP53 Pro47Ser and Arg72Pro SNPs are not involved either in susceptibility to developing gliomas or in patient survival, at least in the Brazilian population.     

Hairless expression attenuates apoptosis in a mouse model and the COS cell line; involvement of p53

Background

Neurons are more likely to die through apoptosis in the immature brain after injury whereas adult neurons in the mature brain die by necrosis. Several studies have suggested that this maturational change in the mechanism of cell death is regulated, in part, by thyroid hormone. We examined the involvement of the hairless (Hr) gene which has been suspected of having a role in cell cycle regulation and apoptosis in the hair follicle and is strongly regulated by the thyroid hormone in the brain.

Methodology

Forced expression of Hr by transfection decreased the number of apoptotic nuclei, levels of caspase-3 activity, and cytosolic cytochrome C in COS cells exposed to staurosporine and tunicamycin. Similarly, capsase-3 activity was lower and the decrease in mitochondrial membrane potential was smaller in cultures of adult cerebellar granule neurons from wild type mice compared to Hr knockout mice induced to undergo apoptosis. In vivo, apoptosis as detected by positive TUNEL labeling and caspase 3 activity was lower in wild-type mice compared to Hr knockouts after exposure to trimethyltin. Hr expression lowered levels of p53, p53 mediated reporter gene activity, and lower levels of the pro-apoptotic Bcl2 family member Bax in COS cells. Finally, Hr expression did not attenuate apoptosis in mouse embryonic fibroblasts from p53 knockout mice but was effective in mouse embryonic fibroblasts from wild type mice.

Conclusions/Significance

Overall, our studies demonstrate that Hr evokes an anti-apoptotic response by repressing expression of p53 and pro-apoptotic events regulated by p53.     

Epstein-Barr virus efficiently immortalizes human B cells without neutralizing the function of p53.

Epstein-Barr virus (EBV) efficiently converts resting human B cells into actively cycling, immortal, lymphoblastoid cell lines (LCLs). Here we show that LCLs expressing the full complement of latent viral genes are very sensitive to DNA-damaging agents such as cisplatin. The response includes a rapid accumulation of the tumour suppressor protein p53 and induction of the cellular genes mdm2 and WAF1/p21. Although the levels of Bcl2 protein and Bax mRNA appear unaltered by the activation of p53, within 24 h the majority of cells undergo apoptosis. Over-expression of wild-type p53 in an LCL also resulted in apoptosis; this was preceded by the dephosphorylation of the retinoblastoma gene product, pRb. Primary resting B cells showed no response to cisplatin and even after drug treatment, p53 remained undetectable. However, after infection with EBV, p53 gene expression was induced to a similar level to that found in mitogen-activated B cells. When the physiologically activated primary B cells were exposed to cisplatin, although p53 accumulated as in LCLs, the outcome was growth-arrest rather than gross cell death. We conclude that, in contrast to the transformation of fibroblasts by adenovirus, SV40 or HPV, when B cells become activated and immortalized by EBV they are sensitized to the p53-mediated damage response. When the resulting LCLs are treated with genotoxic agents such as cisplatin, they are unable to arrest like normal cells because they are driven to proliferate by EBV and consequently undergo apoptosis.     

Evaluating the Association between p53 Codon 72 Arg>Pro Polymorphism and Risk of Ovary Cancer: A Meta-Analysis

Aim

Allelic polymorphism in codon 72 of the p53 tumor suppressor gene causes imbalance of p53 protein expression. Earlier studies have shown association between allelic polymorphism in codon 72 of the p53 gene with risk of ovary cancer (OC); however the results are inconclusive and conflicting. Therefore, we performed this meta-analysis to investigate the relation between p53 codon 72 Arg>Pro polymorphism and overall OC susceptibility.

Methods

We searched all eligible published studies based on the association between codon 72 of the p53 Arg>Pro polymorphism and risk of OC. Data were pooled together from individual studies and meta-analysis was performed. Pooled odds ratios (ORs) and 95% CI were calculated for allele contrast, homozygous, heterozygous, dominant and recessive genetic models.

Results

A total of twelve studies comprising of 993 OC cases and 1264 healthy controls were included in this meta-analysis. Overall, no significant association was detected for Pro allele carrier (Pro vs. Arg: p = 0.916; OR = 0.980, 95% CI = 0.677 to 1.419), homozygous (Pro/Pro vs. Arg/Arg: p = 0.419; OR = 0.731, 95% CI = 0.341 to 1.564), heterozygous (Arg/Pro vs. Arg/Arg: p = 0.248; OR = 1.237, 95% CI = 0.862 to 1.773), dominant (Pro/Pro+Arg/Pro vsArg/Arg: p = 0.699; OR = 1.089, 95% CI = 0.706 to 1.681), and recessive (Pro/Pro vs Arg/Arg+Arg/Pro: p = 0.329; OR = 0.754, 95% CI = 0.428 to 1.329) genetic models, respectively. Also, in the stratified analysis by ethnicity, no significant association of this polymorphism with risk of OC was found in the Caucasian population.

Conclusions

This meta-analysis suggested that codon 72 of the p53 Arg>Pro polymorphism may not significantly contribute in ovary cancer susceptibility. However, future large studies with gene-gene and gene-environment interactions are needed to validate these findings.     

Down-regulation of p53 by double-stranded RNA modulates the antiviral response

p53 has been well characterized as a tumor suppressor gene, but its role in antiviral defense remains unclear. A recent report has demonstrated that p53 can be induced by interferons and is activated after vesicular stomatitis virus (VSV) infection. We observed that different nononcogenic viruses, including encephalomyocarditis virus (EMCV) and human parainfluenza virus type 3 (HPIV3), induced down-regulation of p53 in infected cells. Double-stranded RNA (dsRNA) and a mutant vaccinia virus lacking the dsRNA binding protein E3L can also induce this effect, indicating that dsRNA formed during viral infection is likely the trigger for down-regulation of p53. The mechanism of down-regulation of p53 by dsRNA relies on translation inhibition mediated by the PKR and RNase L pathways. In the absence of p53, the replication of both EMCV and HPIV3 was retarded, whereas, conversely, VSV replication was enhanced. Cell cycle analysis indicated that wild-type (WT) but not p53 knockout (KO) fibroblasts undergo an early-G(1) arrest following dsRNA treatment. Moreover, in WT cells the onset of dsRNA-induced apoptosis begins after p53 levels are down-regulated, whereas p53 KO cells, which lack the early-G(1) arrest, rapidly undergo apoptosis. Hence, our data suggest that the down-regulation of p53 facilitates apoptosis, thereby limiting viral replication.     

p53-independent apoptosis is induced by the p19ARF tumor suppressor

p19(ARF) is a potent tumor suppressor. By inactivating Mdm2, p19(ARF) upregulates p53 activities to induce cell cycle arrest and sensitize cells to apoptosis in the presence of collateral signals. It has also been demonstrated that cell cycle arrest is induced by overexpressed p19(ARF) in p53-deficient mouse embryonic fibroblasts, only in the absence of the Mdm2 gene. Here, we show that apoptosis can be induced without additional apoptosis signals by expression of p19(ARF) using an adenovirus-mediated expression system in p53-intact cell lines as well as p53-deficient cell lines. Also, in primary mouse embryonic fibroblasts (MEFs) lacking p53/ARF, p53-independent apoptosis is induced irrespective of Mdm2 status by expression of p19(ARF). In agreement, p19(ARF)-mediated apoptosis in U2OS cells, but not in Saos2 cells, was attenuated by coexpression of Mdm2. We thus conclude that there is a p53-independent pathway for p19(ARF)-induced apoptosis that is insensitive to inhibition by Mdm2.     

Association between p53 codon 72 genetic polymorphisms and tobacco use and lung cancer risk in a Chinese population

Genetic polymorphisms of p53 codon 72 are thought to have significant effects on the metabolism of environmental carcinogens and thus on lung cancer risk, but the reported results are not always consistent. The aim of this study is to investigate the relationship between p53 codon 72 genetic polymorphisms and tobacco use and lung cancer risk in a Chinese population. A population-based control study was conducted in 360 lung cancer patients and 360 cancer-free controls. The genotype of the p53 codon 72 was determined by using a polymerase chain reaction?Crestriction fragment length polymorphism assay. Patients with lung cancer had a significantly lower frequency of Pro/Pro genotype [odds ratio (OR)?=?0.58, 95?% confidence interval (CI)?=?0.40, 0.84; P?=?0.004] and Pro allele (OR?=?0.72, 95?% CI?=?0.59, 0.89; P?=?0.002) than controls. Patients with squamous cell carcinoma had also a significantly lower frequency of Pro/Pro genotype (OR?=?0.45, 95?% CI?=?0.25, 0.82; P?=?0.009). In the analysis combining p53 codon 72 polymorphisms and smoking, smokers who had smoked for more than 30 pack-years had a significantly lower frequency of Pro/Pro genotype (OR?=?0.52, 95?% CI?=?0.30, 0.92; P?=?0.03) compared with non-smokers. This study suggests that p53 codon 72 polymorphisms play a role in the development of lung cancer and modifies the risk for smoking-related lung cancer in a Chinese population.     

The associations of p53 overexpression with p53 codon 72 genetic polymorphism in esophageal cancer

Variations in p53 codon 72 have been identified as significant predisposing factors for various cancers, but molecular mechanisms remain unclear. We investigated associations of p53 overexpression with codon 72 variants and other factors with esophageal cancer. Status of p53 overexpression was determined by immunohistochemical staining. Codon 72 polymorphisms and mutation of p53 was identified by PCR-RFLP and direct sequencing from exons 4 to 9, respectively. We evaluated 126 patients who underwent esophagectomy in the National Taiwan University Hospital, and found that the status of p53 overexpression was significantly influenced by presence of codon 72 polymorphisms. After adjustment for other possible confounders, the incidence of p53 overexpression was significantly decreased in patients with Pro/Pro genotype with an odds ratio (OR) of 0.21 (95% CI: 0.067-0.64) (p = 0.0065) compared with incidence in patients with Arg/Arg genotype. The incidence of p53 overexpression was additively increased with environmental exposure to cigarette smoke, alcohol, and areca quid. When compared with individuals exposed to only one of these environmental risk factors, patients who had exposure to two or three risk factors had ORs of 6.11 (95% CI: 1.80-20.75) and 6.22 (95% CI: 1.81-21.34) for p53 overexpression, respectively. Elderly patients (age >70 years) were also more likely to have p53 overexpression, with an OR of 5.63 (95% CI: 1.53-20.64) compared with overexpression among patients aged less than 55 years. Forty-one patients received further evaluation of p53 mutation. There was also a higher incidence of, but without reaching a statistical significance, p53 mutation in patients with p53 overexpression (OR[95% CI]: 2.18 [0.52-9.6]) and codon 72 Arg/Arg genotype (OR [95% CI] of 0.8 [0.13-4.2], comparing genotypes of Pro/Pro and Arg/Pro with Arg/Arg). Our data provide the first observations that the presence of p53 codon 72 variants can be a significant factor influencing p53 overexpression in esophageal cancer, with overexpression also influenced by combined or prolonged environmental exposures.     

Polymorphism at codon 72 of the p53 gene in human acute myelogenous leukemia.

A common polymorphism at codon 72 of the p53 gene in patients with acute myelogenous leukemia (AML) was analyzed by single-strand conformation polymorphism assay and sodium dodecyl sulfate polyacrylamide-gel electrophoresis of immunoprecipitated 35S-labeled P53 protein. No association between this polymorphism and a marked predisposition to AML was found. The half-lives of these two polymorphic forms of P53 were equivalent in normal phytohemagglutinin-stimulated lymphocytes, while the P53 Pro72 isoform was found to be twice as stable as the Arg72 isoform in Daudi cells.     

p53 codon 72 polymorphism, DNA damage and repair, and risk of non-melanoma skin cancer

A very common polymorphism of p53, that of codon 72, codes either for a proline (P72) or an arginine (R72). The two alleles differ in their biological properties: P72 is a stronger inducer of p21, while R72 induces 5-10 times more apoptosis. It is not known, however, whether this polymorphism influences genome stability. The influence of p53 codon 72 polymorphism on cancer risk has been studied for different types of cancer with mixed and inconsistent results. With respect to sporadic non-melanoma skin cancer (NMSC), there are few studies, with small sample sizes, and none in a Latinoamerican population. These studies have found no association between p53 genotype at codon 72 and NMSC. We analyzed whether p53 codon 72 genotype influences genomic stability and the sensitivity of cells to UVB. We also carried out a case-control study of NMSC in a Mexican population which included 204 BCC cases, 42 SCC cases, and 238 controls. There was no association between p53 genotype and basal levels of DNA damage, oxidative DNA damage sensitivity, or DNA repair capacity. R72 dominantly increased the in vitro sensitivity of cells to UVB-induced apoptosis. There was no significant association either between p53 genotype and basal cell carcinoma (BCC), squamous cell carcinoma (SCC) or both combined.     

p53 codon 72 polymorphism is associated with susceptibility to hepatocellular carcinoma in the Turkish population: a case–control study

The tumor suppressor p53 gene plays a crucial role in preventing carcinogenesis through its ability to induce cell cycle arrest and apoptosis following DNA damage and oncogene activation. A guanine (G)/cytosine (C) common single nucleotide polymorphism (SNP) at second position of codon 72 in exon 4 of p53 gene determines a arginine (Arg) to proline (Pro) (Arg72Pro) aminoacidic substitution within the proline-rich domain of p53 protein. Arg72 and Pro72 allele are different from a biochemical and biological point of view and many reports suggest that they can modulate individual cancer susceptibility. To determine the association of the p53 Arg72Pro polymorphism with the risk of hepatocellular carcinoma (HCC) development in a Turkish population, a hospital-based case–control study was designed consisting of 119 subjects with HCC and 119 cancer-free control subjects matched for age, gender, smoking and alcohol status. The genotype frequency of the p53 Arg72Pro polymorphism was determined by using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Our data shows that the Pro/Pro genotype of the p53 Arg72Pro polymorphism is associated with increased risk of HCC development in this Turkish population (OR = 3.20, 95% CI: 1.24–8.22, P = 0.02). Furthermore, according to stratified analysis, a significant association was observed between the homozygote Pro/Pro genotype and HCC risk in the subgroups of male gender (OR = 3.01, 95% CI: 1.14–7.97, P = 0.03) and patients with hepatitis B virus (HBV)-related HCC (OR = 4.04, 95% CI: 1.46–11.15, P = 0.007). Because our results suggest for the first time that the Pro/Pro homozygote of p53 Arg72Pro polymorphism may be a genetic susceptibility factor for HCC (especially in the male gender and HBV-infected patients) in the Turkish population, further independent studies are required to validate our findings in a larger series, as well as in patients of different ethnic origins.