The Pro variant of the p53 codon 72 polymorphism is associated with hepatocellular carcinoma in Moroccan population

Association of the rs1042522 SNP with prostate cancer risk: a study of cancer tissues, primary tumor cultures, and serum samples from a Spanish Caucasian population

Background

Prostate cancer (PCa) is a leading cause of cancer-related deaths in European men, emphasizing the urgent need for effective risk assessment strategies. The TP53 gene, a tumor suppressor gene frequently mutated in cancer, commonly harbors the rs1042522 single nucleotide polymorphism (SNP), known as the P72R SNP, which may influence PCa susceptibility. This study investigated the prevalence of the P72R SNP in European Caucasian PCa samples and its association with PCa risk.

Methods

Genotyping was conducted on 12 hormone-naïve aggressive PCa cultures (hnPCs) from untreated patients (Gleason ≥8), 11 radical prostatectomies (RP), and 94 serum samples using DNA Sanger sequencing and melting curve analysis. Comparative analysis utilized data from the GnomAD database's European Caucasian non-cancer population.

Results

Our results demonstrate a significantly higher frequency of the P72R SNP in PCa samples and serums compared to the general European non-cancer population. A robust and statistically significant association (p < 0.0001) between the SNP and prostate cancer risk was identified, with an odds ratio of 7.937 (95% CI 5.37-11.00). Notably, the G allele (R72) showed a pronounced prevalence in high Gleason score (≥8) patients, although statistical significance was not reached. These results highlight a potential association with undifferentiated and malignant PCa lesions.

Conclusion

The compelling association between the P72R SNP and prostate cancer risk underscores the potential utility of this marker for the early identification of patients at risk of aggressive metastatic prostate cancer. This insight could empower further research to intervene at an early stage by offering enhanced opportunities for timely and targeted interventions.

Association between TLR2, TLR4, and TLR5 genetic variants and the risk of hepatocellular carcinoma in Moroccan population

Hepatocellular carcinoma (HCC) is the fifth most common human malignancy and the fourth most frequent cause of cancer-related deaths worldwide. Toll-like receptors (TLRs), are known to play a key role in hepatocarcinogenesis through induction of inflammation. We aimed to investigate the association between TLR2 rs3804099, TLR4 rs4986790, rs4986791, and rs11536889 and TLR5 rs5744174 and HCC risk in a total of 306 Moroccan subjects, including 152 HCC patient and 154 controls using a TaqMan allelic discrimination assay. Our result showed that the frequency of TLR4 rs11536889 C allele was higher in control group than in HCC patients (OR = 0.52, 95% CI = 0.30-0.88, p = 0.01). Moreover, under the dominant model, we observed that CG/CC genotypes were protective factors against HCC risk (OR = 0.51, 95% CI = 0.28-0.91, p = 0.02). However, no significant differences were found in the allele and genotype frequencies of TLR4 rs4986790 and rs4986791, between HCC patients and controls. Similarly, genotypic frequencies of TLR2 and TLR5 polymorphisms did not differ significantly between HCC patients and controls. However, TLR4 haplotype analysis revealed that ACC haplotype may be protective of HCC risk in patients with HCC (OR = 0.53, 95% CI = 0.31-0.92, p = 0.02). In conclusion, our result suggest that TLR4 rs11536889 polymorphism and ACC haplotype may decrease risk of hepatocellular carcinoma in Moroccan population.

A Review of Cancer Genetics and Genomics Studies in Africa

Cancer is the second leading cause of death globally and is projected to overtake infectious disease as the leading cause of mortality in Africa within the next two decades. Cancer is a group of genomic diseases that presents with intra- and inter-population unique phenotypes, with Black populations having the burden of morbidity and mortality for most types. At large, the prevention and treatment of cancers have been propelled by the understanding of the genetic make-up of the disease of mostly non-African populations. By the same token, there is a wide knowledge gap in understanding the underlying genetic causes of, and genomic alterations associated with, cancer among black Africans. Accordingly, we performed a review of the literature to survey existing studies on cancer genetics/genomics and curated findings pertaining to publications across multiple cancer types conducted on African populations. We used PubMed MeSH terms to retrieve the relevant publications from 1990 to December 2019. The metadata of these publications were extracted using R text mining packages: RISmed and Pubmed.mineR. The data showed that only 0.329% of cancer publications globally were on Africa, and only 0.016% were on cancer genetics/genomics from Africa. Although the most prevalent cancers in Africa are cancers of the breast, cervix, uterus, and prostate, publications representing breast, colorectal, liver, and blood cancers were the most frequent in our review. The most frequently reported cancer genes were BRCA1, BRCA2, and TP53. Next, the genes reported in the reviewed publications’ abstracts were extracted and annotated into three gene ontology classes. Genes in the cellular component class were mostly associated with cell part and organelle part, while those in biological process and molecular function classes were mainly associated with cell process, biological regulation, and binding, and catalytic activity, respectively. Overall, this review highlights the paucity of research on cancer genomics on African populations, identified gaps, and discussed the need for concerted efforts to encourage more research on cancer genomics in Africa.

Virus-associated human cancers in Moroccan population: From epidemiology to prospective research

Eight human viruses have been classified by the International Agency for Research on Cancer as carcinogenic or probably carcinogenic for humans. Infection with high risk human papillomaviruses, hepatitis B and C viruses, Epstein-Barr virus (EBV), human T-Cell Lymphotropic Virus Type 1 (HTLV-1), Human herpesvirus 8 (HHV-8), Merkel cell polyomavirus and human immunodeficiency virus-1 (HIV1) alone or in combination with other agents are the main etiologic factors of many cancers. This review highlights some aspects of virus-associated human cancers, potentially responsible for >14,000 malignancies per year in Morocco. Given that not all individuals infected with these viruses develop cancer, somatic alterations, genetic predisposition, and lifestyle or environmental factors obviously play potentializing roles modulating viral activity. These viral, host genetic signatures and lifestyle interactions may represent a reservoir of biomarkers for early detection, prevention of cancer and rationale-based therapy.

TP53 R72P Polymorphism and Susceptibility to Human Papillomavirus Infection Among Women With Human Immunodeficiency Virus in Morocco: A Case-control Study

Background

Human papillomavirus (HPV) is the most common sexually transmitted agent worldwide. HPV is the main causative agent for cervical cancer. The HPV oncoprotein E6 binds to the tumor suppressor gene product p53, promoting its degradation; the Arg allele of TP53 R72P polymorphism binds more ardently with HPV E6 than the Pro variant. Here, we investigated whether TP53 R72P gene variant, rs104252, was associated with susceptibility to HPV infection in women with human immunodeficiency virus (HIV).

Methods

We analyzed 200 HPV-positive and 68 uninfected women with HIV. Genomic DNA was isolated from cervical swab. The TP53 R72P polymorphism was genotyped by PCR-RFLP. Unconditional logistic regression was used to assess the association between polymorphism and the clinical, lifestyle, and behavioral data.

Results

The genotype and allele frequencies of rs104252 variant did not differ between women without or with HPV infection (P > 0.05). Moreover, the p53 polymorphism was not associated with cervical cytology. In contrast, when we analyzed according to behavior factors, the P72P genotype was more frequent among HPV-positive smoker women. However, no significant relationship was found between alcohol, contraceptive use, and number of partners with TP53 R72P genotype distributions among HPV-positive cases (P > 0.05).

Conclusions

The R72 variant of p53 R72P is not associated with HPV infection and progression of lesions. There was no association between this variant and behavior factors in HPV-positive cases. The P72P genotype may be more frequent among HPV-positive smoker women.

Association between MDM2 SNP309, p53 Arg72Pro, and hepatocellular carcinoma risk: A MOOSE-compliant meta-analysis

Epidemiological studies have determined the associations between polymorphisms on the promoter of MDM2 (SNP309) and the codon 72 on exon 4 of p53 (p53 Arg72Pro) and the risk of hepatocellular carcinoma (HCC); however, the results were not always consistent. The aim of the present meta-analysis was to evaluate the overall associations between these 2 variants and HCC risk.The MEDLINE, Web of science, EMBASE, Cochrane Library, and CNKI databases were searched for eligibility studies and the data were synthesized under the fixed- or random-effects model. Heterogeneity among the studies was evaluated with the Cochrane test Q and I statistic.For MDM2 SNP309, the pooled odds ratio (OR) from 15 independent studies with a total of 4038 cases and 5491 controls suggested a significant association for the variant with HCC risk [allele model, G vs T: pooled OR = 1.48, 95% confidence interval (95% CI) = 1.26-1.73; pooled OR = 1.53, 95% CI = 1.26-1.81, for G/T vs T/T; pooled OR = 2.04, 95% CI = 1.54-2.71 for G/G vs T/T]. For p53 Arg72Pro, a total of 21 studies with 7285 cases and 9710 controls suggested that the variant was also associated with HCC risk under common genetic model (allele Pro vs Arg, pooled OR = 1.13, 95% CI = 1.02-1.25; Pro/Pro vs Arg/Arg, pooled OR = 1.32, 95% CI =1.06-1.64). No publication bias was found for all the meta-analysis as suggested by the Begg funnel plot and Egger tests.These results suggested that variants MDM2 SNP309 and p53 Arg72Pro are susceptibility factors for HCC; however, more studies are warranted to validate the results.

Association of p53 codon 72 polymorphism with susceptibility to hepatocellular carcinoma in a Chinese population from northeast Sichuan

The p53 tumor suppressor gene is key in tumor development and progression, and the single nucleotide polymorphism (SNP) of the p53 gene codon 72 (p53Arg/Pro) changes the structure of the protein. In addition, it affects its activity, which may affect cancer risk. The aim of the present study was to investigate the association between p53 codon 72 polymorphism and susceptibility to hepatocellular carcinoma (HCC) in a Chinese population from northeast Sichuan. A total of 342 HCC patients and 347 non-cancer control subjects were recruited, and the polymorphism of p53 codon 72 was measured by TaqMan^® minor groove binder fluorescent quantitative polymerase chain reaction assay. The distribution frequency of p53 sites of arginine (Arg)/Arg, Arg/proline (Pro), Pro/Pro were 18.4, 48.8 and 32.8% in the control group, as compared with 18.7, 49.9 and 31.4% in the case group, which indicated that there was no difference between two groups (χ²=0.14; P=0.93). Upon further stratification with smoking, alcohol consumption, gender and hepatitis B virus (HBV) infection, no risk increasing genotype was identified. However, interactions between p53 codon 72 SNP and smoking, alcohol consumption and HBV infection may increase the risk of HCC [smoking odds ratio (OR), 2.00; 95% confidence interval (CI), 1.21-3.29; alcohol consumption OR, 1.87; 95% CI, 1.08-3.26; HBV infection OR, 1.84; 95% CI, 1.10-3.08]. No significant association was identified between p53 codon 72 polymorphism and HCC, and it may not have an independent effect on the susceptibility to HCC in a Chinese population from northeast Sichuan. However, interaction between genetic factors and environment exposure significantly increased the risk of HCC.

Association between mannose-binding lectin variants, haplotypes and risk of hepatocellular carcinoma: A case-control study

The innate immunity gene mannose-binding lectin2 (MBL2) has played an important role in hepatitis B virus (HBV) infection, and the relationship between MBL2 variants and hepatocellular carcinoma (HCC) risk has not yet been identified. In total, 315 HCC cases and 315 healthy controls were enrolled and blood samples were acquired. High resolution melt analysis (HRM) was employed to genotype 6 polymorphisms in MBL2 gene. Increased HCC risk in carriers of LL genotype of -550 polymorphism with an adjusted OR (AOR) of 1.61 (95%CI = 1.00-2.57) was observed but no significant association detected in HL genotype. Both YX and XX genotype demonstrated a significantly elevated HCC risk in the analysis of -221 polymorphism. The B variants in codon 54 was also significantly associated with elevated HCC risk. HYB was identified as the protective factor of HCC while LXB was significantly associated with increase HCC risk. ELISA technique revealed that the MBL2 protein was significantly reduced in HCC cases. Moreover, both IL-1β and IL-6 were inversely associated with plasma MBL2 level.The mutations in MBL2 could lead to compromised innate immunity, and possibly lead to elevated HCC risk, and a novel haplotype HXB has been identified with a rate of 12.5%.

Interaction between p53 codon 72 and MDM2 309T>G polymorphisms and the risk of hepatocellular carcinoma

The p53 tumor suppressor and its negative regulator, murine double minute 2 (MDM2), play critical roles in carcinogenesis. P53 codon 72 and MDM2 309T>G polymorphisms could influence p53 and MDM2 function, respectively, and might affect cancer susceptibility. We therefore investigated the association between these two SNPs, alone or in combination, and the risk of hepatocellular carcinoma (HCC) in Chinese. In this case-control study, we genotyped p53 codon 72 and MDM2 309T>G polymorphisms in 985 HCC cases and 992 cancer-free age- and sex-matched controls and evaluated their associations with the risk of HCC. Although no significant main effects were found for these two SNPs in the single-locus analysis and stratified analysis by age, sex, smoking, drinking, and hepatitis B virus (HBV) infection, we found that individuals carrying at least one G allele of the MDM2 309T>G polymorphism had statistically significant increased risk of HCC among those with the p53 Pro/Pro genotype (adjusted odds ratio (OR) = 2.23, 95 % confidence interval (95%CI) = 1.20-4.14 for TG genotype; adjusted OR = 2.67, 95%CI = 1.32-5.42 for GG genotype), and the interaction between p53 codon 72 and MDM2 309T>G was significant (P interaction = 0.017). Our findings suggest that the interaction of p53 codon 72 and MDM2 309T>G may play an important role in the etiology of HCC. More studies with well-designed and large sample sizes are required to validate these observations.

Evaluation of the p53 Arg72Pro polymorphism and its association with cancer risk: a HuGE review and meta-analysis

Codon 72 is a hotspot of polymorphisms in the TP53 gene, which encodes a hub protein in the protein-protein interaction network of p53. It is thus a central player in the apoptotic pathway, preventing cancer. A large number of articles have been published exploring its association with an increased susceptibility to most common cancers. However, these studies have produced inconclusive results, which may be due to their small sample sizes or study designs. To comprehensively evaluate the potential correlation between the TP53 Pro72Arg polymorphism and cancer risk and to better characterize the Pro72Arg polymorphism, we performed a systematic HuGE review and meta-analysis of candidate studies through online resources, according to the proposal of MOOSE and the PRISMA statement. The identified articles were carefully examined according to the inclusion criteria. Pooled odds ratios were calculated on the basis of different genetic models, while heterogeneity was assessed through a chi-based Q-test and I2. After applying the inclusion filters, we obtained a pool of 54 eligible studies, representing 18 718 cases and 21 261 controls. Overall, non-significant cancer risk was observed in all the genetic models but their observed heterogeneity was extremely significant. In subgroup analysis, an increased susceptibility was observed in the case of colorectal cancer, while in cancers of the female reproductive system, significantly increased risk was detected in all the genetic models except the dominant model. In another subgroup analysis, significantly increased cancer risk was observed among Asians in homozygous and recessive models, while in Americans increased cancer risk was observed only in dominant and recessive models. No association was observed in the rest of the populations. In conclusion, pooled subgroup analysis on the basis of ethnicity proved that the TP53 Arg72Pro polymorphism is associated with an increased risk of cancer in Asians and Americans only and is not associated in other populations. It can therefore be concluded that this meta-analysis of available data suggests partial confirmation of the association between the TP53 Arg72Pro polymorphism and cancer risk susceptibility.

TP53 R72P polymorphism modulates DNA methylation in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is characterized by widespread epidemiological and molecular heterogeneity. Previous work showed that in the western part of North Africa, a region of low incidence of HCC, mutations are scarce for this tumor type. As epigenetic changes are considered possible surrogates to mutations in human cancers, we decided, thus, to characterize DNA methylation in HCC from North-African patients.

METHODS

A set of 11 loci was investigated in a series of 45 tumor specimens using methylation-specific and combined-bisulfite restriction assay PCR. Results obtained on clinical samples were subsequently validated in liver cancer cell lines.

RESULTS

DNA methylation at tumor suppressor loci is significantly higher in samples displaying chromosome instability. More importantly, DNA methylation was significantly higher in Arg/Arg when compared to Pro/Pro genotype carriers at codon 72 rs1042522 of TP53 (65% vs 20% methylated loci, p = 0.0006), a polymorphism already known to affect somatic mutation rate in human carcinomas. In vitro experiments in cell lines indicated that enzymes controlling DNA methylation were differentially regulated by codon 72 Arg or Pro isoforms of p53. Furthermore, the Arg72-carrying version of p53 was shown to re-methylate DNA more rapidly than the pro-harboring isoform. Finally, Pro-carrying cell lines were shown to be significantly more resistant to decitabine treatment (two-fold, p = 0.005).

CONCLUSIONS

Our data suggest that Arg72Pro polymorphism in a WT p53 context may act as a primary driver of epigenetic changes in HCC. It suggests, in addition, that rs1042522 genotype may predict sensitivity to epigenetic-targeted therapy. This model of liver tumorigenesis that associates low penetrance genetic predisposition to epigenetic changes emerges from a region of low HCC incidence and it may, therefore, apply essentially to population living in similar areas. Surveys on populations submitted to highly mutagenic conditions as perinatally-acquired chronic hepatitis B or aflatoxin B1 exposure remained to be conducted to validate our observations as a general model.

Genetic factors, viral infection, other factors and liver cancer: an update on current progress

Primary liver cancer is one of the most common cancers at the global level, accounting for half of all cancers in some undeveloped countries. This disease tends to occur in livers damaged through alcohol abuse, or chronic infection with hepatitis B and C, on a background of cirrhosis. Various cancer-causing substances are associated with primary liver cancer, including certain pesticides and such chemicals as vinyl chloride and arsenic. The strong association between HBV infection and liver cancer is well documented in epidemiological studies. It is generally acknowledged that the virus is involved through long term chronic infection, frequently associated with cirrhosis, suggesting a nonspecific mechanism triggered by the immune response. Chronic inflammation of liver, continuous cell death, abnormal cell growth, would increase the occurrence rate of genetic alterations and risk of disease. However, the statistics indicated that only about one fifth of HBV carries would develop HCC in lifetime, suggesting that individual variation in genome would also influence the susceptibility of HCC. The goal of this review is to highlight present level of knowledge on the role of viral infection and genetic variation in the development of liver cancer.

Association between polymorphisms in tumor suppressor genes and oncogenes and risk of hepatocellular carcinoma: a case-control study in an HCC epidemic area within the Han Chinese population

Data concerning the risk of hepatocellular carcinoma (HCC) and specific single nucleotide polymorphisms (SNPs) in an HBV-free population are currently limited. Therefore, we performed a case-control study to investigate the association between SNPs and the risk of HCC in individuals without chronic HBV infection. A total of 160 Han Chinese patients with HCC and an identical number of healthy controls were enrolled in this study. rs1042522, rs10814325, rs17401966, and rs2279744 genotypes were determined using matrix-associated laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS). CG and GG genotypes in rs1042522 and heterozygote and homozygote in rs2279744 were significantly associated with an elevated risk of HCC. Homozygous mutation of rs1081432 conferred a 2.68-fold risk of HCC (95% CI 1.35-5.34); however heterozygosity was not statistically significant. rs17401966 heterozygosity or homozygosity was not significantly associated with a increased risk of HCC. Several polymorphisms associated with a significantly increased risk of HCC were identified. These may serve as biomarkers in evaluating HCC risk in the general population.

TP53 and MDM2 gene polymorphisms, gene-gene interaction, and hepatocellular carcinoma risk: evidence from an updated meta-analysis

Background

The association between TP53 R72P and/or MDM2 SNP309 polymorphisms and hepatocellular carcinoma (HCC) risk has been widely reported, but results were inconsistent. To clarify the effects of these polymorphisms on HCC risk, an updated meta-analysis of all available studies was conducted.

Methods

Eligible articles were identified by search of databases including PubMed, Cochrane Library, EMBASE and Chinese Biomedical Literature database (CBM) for the period up to July 2013. Data were extracted by two independent authors and pooled odds ratio (OR) with 95% confidence interval (CI) was calculated. Metaregression and subgroup analyses were performed to identify the source of heterogeneity.

Results

Finally, a total of 10 studies including 2,243 cases and 3,615 controls were available for MDM2 SNP309 polymorphism and 14 studies containing 4,855 cases and 6,630 controls were included for TP53 R72P polymorphism. With respect to MDM2 SNP309 polymorphism, significantly increased HCC risk was found in the overall population. In subgroup analysis by ethnicity and hepatitis virus infection status, significantly increased HCC risk was found in Asians, Caucasians, Africans, and HCV positive patients. With respect to TP53 R72P polymorphism, no significant association with HCC risk was observed in the overall and subgroup analyses. In the MDM2 SNP309–TP53 R72P interaction analysis, we found that subjects with MDM2 309TT and TP53 Pro/Pro genotype, MDM2 309 TG and TP53 Arg/Pro genotype, and MDM2 309 GG and TP53 Pro/Pro genotype were associated with significantly increased risk of developing HCC as compared with the reference MDM2 309TT and TP53 Arg/Arg genotype.

Conclusions

We concluded that MDM2 SNP309 polymorphism may play an important role in the carcinogenesis of HCC. In addition, our findings further suggest that the combination of MDM2 SNP 309 and TP53 Arg72Pro genotypes confers higher risk to develop HCC. Further large and well-designed studies are needed to confirm this association.

The association between polymorphism of P53 Codon72 Arg/Pro and hepatocellular carcinoma susceptibility: evidence from a meta-analysis of 15 studies with 3,704 cases

Emerging evidence has shown that p53gene participates in human carcinogenesis as tumor suppressors. Polymorphism of p53 gene codon72 arginine (Arg)/proline (Pro) (rs1042522) may influence the function of p53 protein and then affect the processing of carcinogenesis. It has been suggested that p53 codon72 Arg/Pro polymorphism is associated with susceptibility to hepatocellular carcinoma (HCC). However, published results are inconsistent and inconclusive. To examine the validity of the association between the polymorphism and HCC risk, we performed this meta-analysis. We have conducted a search of case-control studies on the associations of p53 codon72 polymorphism with susceptibility to HCC in PubMed, ScienceDirect, BioMed central, Springer, EBSCO, Wanfang databases, and Chinese National Knowledge Infrastructure databases. A total of 15 studies were identified with 3,704 cases and 4,559 controls for codon72 Arg/Pro polymorphism. The result did support a significant genetic association between Pro allele and susceptibility to HCC in all the genetic models. Similarly, subgroup analysis showed significant associations between the Arg/Pro polymorphism and susceptibility to HCC when stratifying by race, gender, source of controls, and hepatitis virus infection status. This meta-analysis suggests that p53 codon72 Arg/Pro polymorphism may be associated with the risk of HCC, especially in subgroup analysis of Asian and Caucasian population, hospital-based population, the female, and the individuals infected with hepatitis virus. However, well-designed studies based on different ethnic groups with larger sample size and more detailed data are needed to confirm these conclusions.

The association between polymorphism of P53 codon 72 Arg/Pro and hepatocellular carcinoma susceptibility: evidence from a meta-analysis of 15 studies with 3704 cases

BACKGROUND

Emerging evidence has shown that p53gene participates in human carcinogenesis as tumor suppressors. Polymorphism of p53 gene codon 72 Arg/Pro (rs1042522) may influence the function of p53 protein and then affect the processing of carcinogenesis. It has been suggested that p53 codon 72 Arg/Pro polymorphism is associated with susceptibility to hepatocellular carcinoma (HCC). However, published results are inconsistent and inconclusive. To examine the validity of the association between the polymorphism and HCC risk, we performed this meta-analysis.

METHODOLOGY/PRINCIPAL FINDINGS

We have conducted a search of case-control studies on the associations of p53 codon 72 polymorphism with susceptibility to HCC in PubMed, ScienceDirect, Bio-Med central, Springer-link, EBSCO, Wanfang databases and Chinese National Knowledge Infrastructure (CNKI) databases. A total of 15 studies were identified with 3704 cases and 4559 controls for codon 72 Arg/Pro polymorphism. The result did support a significant genetic association between Pro allele and susceptibility to HCC in all the genetic models. Similarly, subgroup analysis showed significant associations between the Arg/Pro polymorphism and susceptibility to HCC when stratifying by race, gender, source of controls and hepatitis virus infection status.

CONCLUSIONS/SIGNIFICANCE

This meta-analysis suggests that p53 codon 72 Arg/Pro polymorphism may be associated with the risk of HCC, especially in subgroup analysis of Asian and Caucasian population, hospital-based population, the female, and the individuals infected with hepatitis virus. However, well-designed studies based on different ethnic groups with larger sample size and more detailed data are needed to confirm these conclusions.

Human genetic variation and the risk of hepatocellular carcinoma development

Our understanding of the patho-physiology of hepatocellular carcinoma (HCC) is still much fragmented making difficult the improvement of the clinical outcome for the majority of HCC patients. Discovery of single nucleotide polymorphisms (SNPs) associated with individual susceptibility to HCC may enable the persons at risk to adapt their lifestyle and legitimate implementation by their doctors of surveillance programs facilitating early detection and subsequent management of the disease. To shed light on the influence of human genetic variation on HCC, we conducted a review of the meta-analyses of candidate SNPs and genome wide association studies (GWAS) performed for HCC by search of PubMed and Google Scholar databases. Genetic variations occurring in pathways historically considered as instrumental for liver tumorigenesis (TP53/MDM2, HLA, glutathione-S-transferases/cytochrome P540, TNFα/TGFβ, etc…) are discussed. An immense majority of the data has been produced in Eastern Asia (China, Japan, Korea). These meta-analyses indicate that the TP53, the MDM2 SNP309 G and the GSTT1 null genotype contribute to an increased risk of HCC both in Asians and Caucasians. Significant differences of odds ratios are, however, commonly observed between Eastern-Asians and other populations. Amazingly, GWAS studies performed so far exclusively with HCC patients from Eastern Asia produced drastically different outcomes pointing at unrelated biological pathways. The small magnitude of the risk associated with the genetic variants raises the question of their future utility as markers in clinical practice. An assessment of their impact on tumor progression (vascular invasion, metastases) remains, however, to be done and may prove to be more useful for clinicians. Finally, the evaluation of these variants is not available for various populations of the world and particularly for Subsaharan Africans who are especially affected by HCC.

Association between TP53 Arg72Pro polymorphism and hepatocellular carcinoma risk: a meta-analysis

BACKGROUND

Previous studies on the association between the TP53 Arg72Pro polymorphism and hepatocellular carcinoma (HCC) risk obtained controversial findings. This study aimed to quantify the strength of the association by meta-analysis.

METHODS

We searched PubMed and Wangfang databases for published studies on the association between the TP53 Arg72Pro polymorphism and HCC risk, using the pooled odds ratio (OR) with its 95% confidence intervals (95% CI) for assessment.

RESULTS

10 studies with a total of 2,026 cases and 2,733 controls were finally included into this meta-analysis. Overall, the TP53 Arg72Pro polymorphism was not associated with HCC risk (all P values greaterth HCC risk in Caucasians in three genetic models (For Pro versus Arg, OR = 1.20, 95%CI 1.03-1.41; For ProPro versus ArgArg, OR = 1.74, 95%CI 1.23-2.47; For ProPro versus ArgPro/ArgArg, OR = 1.85, 95%CI 1.33-2.57). However, there was no significant association between the TP53 Arg72Pro polymorphism and HCC risk in East Asians (all P values greater than 0.10). No evidence of publication bias was observed.

CONCLUSION

Meta-analyses of available data suggest an obvious association between the TP53 Arg72Pro and HCC risk in Caucasians. However, the TP53 Arg72Pro polymorphism may have a race-specific effect on HCC risk and further studies are needed to elucidate this possible effect.

Association between the p53 codon 72 Arg/Pro polymorphism and hepatocellular carcinoma risk

Previous studies regarding the association of p53 codon 72 Arg/Pro polymorphism with hepatocellular carcinoma (HCC) risk have provided conflicting and inconclusive findings. Thus, a meta-analysis of all currently available publications was performed to address this issue. Eleven individual case-control studies involving a total of 2,718 cases and 3,752 controls were identified after a systematic search of the PubMed, Embase, Web of Science, and Wanfang databases. The strength of the association of p53 codon 72 Arg/Pro polymorphism with HCC risk was estimated by the pooled odds ratio (OR) with its corresponding 95 % confidence interval (95 % CI). Subgroup analyses stratified by ethnicity, source of controls, gender, hepatitis virus infection status, and family history of HCC were also conducted to assess the association. Overall, significantly increased risk of HCC was identified among carriers of the homozygous genotype ProPro (ORProPro vs. ArgArg=1.38 (95 % CI, 1.03-1.85), P OR=0.033; ORProPro vs. ArgArg + ArgPro =1.28 (95 % CI, 1.03-1.59), P OR=0.026). In subgroup analysis by ethnicity, the pooled results suggested that the p53 codon 72 Arg/Pro polymorphism was associated with an increased risk of HCC in Asians and Caucasians (for Asians, ORProPro vs. ArgArg + ArgPro=1.17 (95 % CI, 1.02-1.34), P OR=0.025; for Caucasians, ORProPro vs. ArgArg = 1.65 (95 % CI, 1.07-2.56), P OR=0.025; ORProPro vs. ArgArg + ArgPro=1.74 (95 % CI, 1.14-2.66), P OR=0.010). Subgroup analyses by source of controls and hepatitis virus infection status further demonstrated the significant association, whereas stratification factors involving gender and family history of HCC did not modify the association between p53 codon 72 Arg/Pro polymorphism and HCC risk. This meta-analysis suggests that the p53 codon 72 Arg/Pro polymorphism may play a critical role in the development of HCC, and gender and family history of HCC may not modulate the effect of p53 codon 72 Arg/Pro in HCC risk.

The p53 Codon 72 Polymorphism Modifies the Cellular Response to Inflammatory Challenge in the Liver

The p53 protein is a critical stress-response mediator and signal coordinator in cellular metabolism and environmental exposure to deleterious agents. In human populations, the p53 gene contains a common single nucleotide polymorphism (SNP) affecting codon 72 that determines whether a proline (P72) or an arginine (R72) is present at this amino acid position of the polypeptide. Previous studies carried out using human populations, mouse models, and cell culture analyses have provided evidence that this amino acid difference can alter p53 functional activities, and potentially also can affect clinical presentation of disease. The clinical presentation associated with many forms of liver disease is variable, but few of the responsible underlying genetic factors or molecular pathways have been identified. The aim of the present study was to investigate whether the p53 codon 72 polymorphism influences the cellular response to hepatic stresses. A humanized p53 knock-in (Hupki) mouse model was used to address this issue. Mice expressing either the P72 or R72 normal variation of p53 were given an acute-, intermittent- or a chronic challenge, associated with exposure to lipopolysaccharide, D-galactosamine, or a high-fat diet. The results reveal that the livers of the P72 and R72 mice exhibit notable differences in inflammatory and apoptotic response to these distinct forms of stress. Interestingly the influence of this polymorphism on the response to stress is context dependent, with P72 showing increased response to liver toxins (lipopolysaccharide and D-galactosamine), but R72 showing increased response to metabolic stress (high fat diet). When taken together, these data point to the p53 codon 72 polymorphism as an important molecular mediator of events contributing to hepatic inflammation and metabolic homeostasis.

TP53 codon 72 polymorphism with hepatocellular carcinoma: a metaanalysis

OBJECTIVE

The association between codon 72 polymorphism of the tumour protein p53 (TP53) gene - which results in a missense mutation of arginine (R) to proline (P) - and susceptibility to hepatocellular carcinoma (HCC) is controversial. A metaanalysis was performed in order to define this relationship more precisely.

METHODS

Published studies of TP53 codon 72 polymorphism and the risk of HCC were identified. Data were extracted, and summary odds ratios (OR) and 95% confidence intervals (95% CI) were calculated. Pooled ORs were determined for an additive model (R/R versus P/P), a dominant model ([R/R + R/P] versus P/P) and a recessive model (R/R versus [R/P + P/P]).

RESULTS

The meta-analysis included seven case-control studies (total 1511 cases and 2165 controls). The risk of cancer was significantly decreased in the overall dominant model and the dominant model in Asian populations. A significantly decreased risk was found for all models in hospital-based but not population-based studies. There was no association between polymorphism and cancer risk when data were stratified according to hepatitis B or C virus infection status.

CONCLUSION

The TP53 codon 72 polymorphism may be a risk factor for HCC.

Role of p53 codon 72 polymorphism in chromosomal aberrations and mitotic index in patients with chronic hepatitis B

Polymorphisms of the p53 gene, which participates in DNA repair, can affect the functioning of the p53 protein. The Arg and Pro variants in p53 codon 72 were shown to have different regulation properties of p53-dependent DNA repair target genes that can affect various levels of cytogenetic aberrations in chronic hepatitis B patients. The present study aimed to examine the frequency of chromosomal aberrations and the mitotic index in patients with chronic hepatitis B and their possible association with p53 gene exon 4 codon 72 Arg72Pro (Ex4+119 G>C; rs1042522) polymorphism. Fifty-eight patients with chronic hepatitis B and 30 healthy individuals were genotyped in terms of the p53 gene codon 72 Arg72Pro polymorphism by PCR-RFLP. A 72-h cell culture was performed on the same individuals and evaluated in terms of chromosomal aberrations and mitotic index. A high frequency of chromosomal aberrations and low mitotic index were detected in the patient group compared to the control group. A higher frequency of chromosomal aberrations was detected in both the patient and the control groups with a homozygous proline genotype (13 patients, 3 control subjects) compared to patients and controls with other genotypes [Arg/Pro (38 patients, 20 control subjects) and Arg/Arg (7 patients, 7 control subjects)]. We observed an increased frequency of cytogenetic aberrations in patients with chronic hepatitis B. In addition, a higher frequency of cytogenetic aberrations was observed in p53 variants having the homozygous proline genotype compared to variants having other genotypes both in patients and healthy individuals.

Variability in the precore and core promoter regions of HBV strains in Morocco: characterization and impact on liver disease progression

Background

Hepatitis B virus (HBV) is one of the most common human pathogens that cause aggressive hepatitis and advanced liver disease (AdLD), including liver cirrhosis and Hepatocellular Carcinoma. The persistence of active HBV replication and liver damage after the loss of hepatitis B e antigen (HBeAg) has been frequently associated with mutations in the pre-core (pre-C) and core promoter (CP) regions of HBV genome that abolish or reduce HBeAg expression. The purpose of this study was to assess the prevalence of pre-C and CP mutations and their impact on the subsequent course of liver disease in Morocco.

Methods/Principal Findings

A cohort of 186 patients with HBeAg-negative chronic HBV infection was studied (81 inactive carriers, 69 with active chronic hepatitis, 36 with AdLD). Pre-C and CP mutations were analyzed by PCR-direct sequencing method. The pre-C stop codon G1896A mutation was the most frequent (83.9%) and was associated with a lower risk of AdLD development (OR, 0.4; 95% CI, 0.15–1.04; p = 0.04). HBV-DNA levels in patients with G1896A were not significantly different from the other patients carrying wild-type strains (p = 0.84). CP mutations C1653T, T1753V, A1762T/G1764A, and C1766T/T1768A were associated with higher HBV-DNA level and increased liver disease severity. Multiple logistic regression analysis showed that older age (≥40 years), male sex, high viral load (>4.3 log₁₀ IU/mL) and CP mutations C1653T, T1753V, A1762T/G1764A, and C1766T/T1768A were independent risk factors for AdLD development. Combination of these mutations was significantly associated with AdLD (OR, 7.52; 95% CI, 4.8–8; p<0.0001).

Conclusions

This study shows for the first time the association of HBV viral load and CP mutations with the severity of liver disease in Moroccan HBV chronic carriers. The examination of CP mutations alone or in combination could be helpful for prediction of the clinical outcome.

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.

Impact of TP53 codon 72 and MDM2 promoter 309 allelic dosage in a Moroccan population with hepatocellular carcinoma

Single-nucleotide polymorphisms (SNPs) in codon 72 of the TP53 gene (rs1042522) and in the promoter region of the MDM2 gene (SNP309; rs2279744) have been shown to play a role in the predisposition to many cancers. However, these findings were inconsistent in other tumor types, and ethnicity is suspected to be a critical factor influencing the effects of these SNPs on the cancer risk. The aim of the present study was to investigate whether these functional SNPs were associated with an enhanced risk of liver tumorigenesis in Moroccan patients. We have genotyped both polymorphisms in 96 patients with hepatocellular carcinoma (HCC) and 222 controls without HCC matched for age, gender and ethnicity by PCR-RFLP confirmed by sequencing. A joint effect between the MDM2 and TP53 polymorphisms and an increased risk of liver cancer was detected, with the odds ratio for the presence of both MDM2 309GG and TP53 72Pro/Pro genotypes being 10 (95% confidence interval 0.39-255.55). Interestingly, a significant increase in the HCC risk was observed when at least two deleterious alleles were present, indicating an allele dosage effect. There was no evidence for any association with early age of HCC onset when deleterious alleles of MDM2 SNP309 and TP53 Arg72Pro where present. Our findings suggest that the combination of TP53 72Pro and MDM2 309G polymorphisms enhance the risk of developing HCC. These results deserve further confirmation in other populations.

Associations of genetic variants in the transcriptional coactivators EP300 and PCAF with hepatocellular carcinoma

BACKGROUND AND AIMS

Hepatocellular carcinoma (HCC) is a common cause of death by cancer worldwide. In Morocco, HCC is characterized by few mutations and a mild chromosome instability suggesting that epigenetic changes may represent the driving force of tumorigenesis in the region. Recently, three studies looked for an association between EP300 or PCAF polymorphisms and cancer but there is a conspicuous lack of data regarding these histone acetyltransferase (HAT) variants and HCC development. The aim of the current study was to assess the impact of the Ile997Val in EP300 and Asn386Ser in PCAF polymorphisms on the risk of HCC.

MATERIALS AND METHODS

We performed a case-control study comparing 94 cases with HCC and 220 matching controls. Sequencing methods were used to determine the genotype at the Ile997Val and Asn386Ser on EP300 and PCAF.

RESULTS

We found an overall association between genotypes Val/Val in EP300 and HCC risk (OR, 3.03; 95% CI, 1.08-8.47; P=0.028). Population stratifications revealed a trend or significantly higher risks of HCC development for women and HCV-negative patients carrying the EP300 Val/Val genotype (OR, 4.06; 95% CI, 0.71-23.36; P=0.09 and OR, 4.48; 95% CI, 1.04-19.14; P=0.02, respectively). The PCAF Ser/Ser genotype at codon 386 was more frequent in HCC cases than in control group (P=0.03). We observed trends for higher risk of HCC among men and/or HCV-negative patients carrying Ser/Ser genotype when compared with controls (OR, 10.62; 95% CI, 0.50-225.13 and OR, 11.78; 95% CI, 0.47-295.56, respectively).

CONCLUSION

It appears that variants of the transcriptional coactivator genes (EP300 and PCAF) may influence HCC risk in populations with low mutations or chromosomal instability rates. Additional surveys are warranted to confirm this first report.

TP53 and MDM2 gene polymorphisms and risk of hepatocellular carcinoma among Italian patients

Background

Single-nucleotide polymorphisms within TP53 gene (codon 72 exon 4, rs1042522, encoding either arginine or proline) and MDM2 promoter (SNP309; rs2279744), have been independently associated with increased risk of several cancer types. Few studies have analysed the role of these polymorphisms in the development of hepatocellular carcinoma.

Methods

Genotype distribution of TP53 codon 72 and MDM2 SNP309 in 61 viral hepatitis-related hepatocellular carcinoma cases and 122 blood samples (healthy controls) from Italian subjects were determined by PCR and restriction fragment length polymorphism (RFLP).

Results

Frequencies of TP53 codon 72 alleles were not significantly different between cases and controls. A significant increase of MDM2 SNP309 G/G and T/G genotypes were observed among hepatocellular carcinoma cases (Odds Ratio, OR = 3.56, 95% Confidence Limits, 95% CI = 1.3-9.7; and OR = 2.82, 95% CI = 1.3-6.4, respectively).

Conclusions

These results highlight a significant role of MDM2 SNP309 G allele as a susceptibility gene for the development of viral hepatitis-related hepatocellular carcinoma among Italian subjects.

Genetic variants of the p53 and p73 genes jointly increase risk of second primary malignancies in patients after index squamous cell carcinoma of the head and neck

BACKGROUND

Because of the structural and biochemical similarities between the antitumor p53 and p73 proteins, the authors hypothesized that individuals who carry high-risk genotypes of p53 codon 72 and p73 G4C14-to-A4T14 polymorphisms have a higher risk of developing second primary malignancy (SPM) after index squamous cell carcinoma of the head and neck (SCCHN).

METHODS

A cohort of 1269 patients with index cases of SCCHN was recruited between May 1995 and January 2007 at The University of Texas MD Anderson Cancer Center and followed for SPM development. Patients were genotyped for p53 codon 72 and p73 G4C14-to-A4T14 polymorphisms. A log-rank test and Cox proportional hazard models were used to compare SPM-free survival and SPM risk among different risk groups with the combined risk genotypes of the 2 polymorphisms.

RESULTS

The data demonstrated that patients with p53 WP + PP and p73 GC/GC genotypes had a worse SPM-free survival and an increased SPM risk compared with the corresponding p53 WW and p73 GC/AT + AT/AT genotypes. After combining the 2 polymorphisms, a borderline significantly or significantly reduced SPM-free survival and increased SPM risk were observed in the medium-risk group (p53 WW and p73 GC/GC or p53 P carriers and p73 AT carriers) and high-risk group (p53 P carriers and p73 GC/GC) compared with low-risk group (p53 WW and p73 AT carriers), respectively.

CONCLUSIONS

The results suggest an increased risk of SPM after index SCCHN with both p53 and p73 polymorphisms individually and in combination.

Associations between P53 Arg72Pro and development of digestive tract cancers: a meta-analysis

BACKGROUND AND AIMS

The relationships between P53 Arg72Pro and risks of digestive tract cancers have been extensively studied, and conclusive results were unavailable.

METHODS

Fifty three case-control studies were included through searching the databases of Medline, Embase and CNKI (up to August 2010). The odds ratio (OR) and 95% confidence interval (95% CI) were used to investigate the strength of the associations.

RESULTS

The results showed that there were no overall associations between P53 Arg72Pro and risks of digestive tract cancers. Subgroup analyses showed that P53 Arg72Pro was associated with risk of gallbladder and pancreatic cancer (OR [95% CI]: 1.44 [1.13-1.83] for Pro carriers vs. ArgArg). In addition, subgroup analyses also suggested that the Pro allele was associated with increased risks of digestive tract cancers among Asians (1.19 [1.01-1.42] for ProPro vs. ArgArg). Meanwhile, Pro allele was also suggested to be associated with increased risk of gastric cancer (1.33 [1.02-1.74] for ProPro vs. ArgPro for diffuse type of gastric cancer and 1.29 [1.05-1.57] for ProPro vs. Arg carriers for gastric cardia cancer) and colorectal cancer (1.26 [1.05-1.51] for ProPro vs. ArgPro for population-based case-control studies; 1.43 [1.09-1.87] for ProPro vs. ArgArg for colon cancer; 1.49 [1.09-2.06] for ProPro vs. ArgArg for rectal cancer and 2.22 [1.44-3.44] for ProPro vs. ArgArg for early stage of colorectal cancer).

CONCLUSIONS

This meta-analysis suggests that Pro allele in P53 Arg72Pro is significantly associated with the increased risks of digestive tract cancers, especially for Asians, and for gastric cancer, colorectal cancer and gallbladder and pancreatic cancer.

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.

p53 codon 72 polymorphism and liver cancer susceptibility: A meta-analysis of epidemiologic studies

AIM: To evaluate the association between p53 codon 72 polymorphism and liver cancer risk by means of meta-analysis.

METHODS: Two investigators independently searched the Medline, Embase and Chinese Biomedicine databases. Summary odds ratios and 95% CI for p53 codon 72 polymorphism and liver cancer were calculated in fixed-effects model (Mantel-Haenszel method) and random-effects model (DerSimonian and Laird method) when appropriate.

RESULTS: This meta-analysis included 1115 liver cancer cases and 1778 controls. The combined results based on all studies showed that there was a statistically significant link between Pro/Pro genotype and liver cancer, but not between Arg/Arg or Pro/Arg genotype and liver cancer. When stratifying for race, similar results were obtained, i.e. patients with liver cancer had a significantly higher frequency of Pro/Pro genotype than non-cancer patients among Asians. After stratifying the various studies by control source, gender, family history of liver cancer and chronic hepatitis virus infection, we found that (1) patients among hospital-based studies had a significantly higher frequency of Pro/Pro and a significantly lower frequency of Arg/Arg genotype than individuals without cancer; (2) female patients with liver cancer had a significantly lower frequency of Arg/Arg and a higher frequency of Pro/Arg+Pro/Pro genotypes than female individuals without cancer; (3) subgroup analyses for family history of liver cancer did not reveal any significant association between p53 codon 72 polymorphism and liver cancer development; and (4) patients with negative hepatitis virus infection had a significantly higher frequency of Pro/Pro and a significantly lower frequency of Arg/Arg genotype than individuals without cancer.

CONCLUSION: This meta-analysis suggests that the p53 codon 72 polymorphism may be associated with liver cancer among Asians.

DeltaN133p53 expression levels in relation to haplotypes of the TP53 internal promoter region

The transcription of the DeltaN133p53 isoform of the TP53 gene is controlled by an internal promoter region (IPR) containing eight polymorphisms in 11 common haplotypes, following a resequencing of 47 Caucasians. We assayed the functional effects of the commonest six haplotypes on the promoter activity with a luciferase reporter system, in HeLa and 293T cells. These studies showed that different IPR haplotypes are associated with differences in the promoter activity resulting in marked variation in the baseline expression of DeltaN133p53. In vivo quantitative-polymerase chain reaction (PCR) on human tissues confirmed that the baseline levels of DeltaN133p53 showed haplotype specific differences that paralleled those seen in vitro. When cell lines were treated with camptothecin, the fold-increase in DeltaN133p53 levels was dose-dependent but haplotype-independent (i.e., similar for all the haplotypes). Finally, we used an electrophoretic mobility shift assay to analyze the rs1794287 polymorphism and found changes in the pattern of protein binding. This partially confirmed our in silico analysis showing that the polymorphism rs1794287 can affect the function of the internal promoter by changing its affinity for several transcription factors. Thus, we showed that the expression of DeltaN133p53 is under genetic control, and suggested the presence of interindividual differences underlying this mechanism.

Association of p53 codon 72 polymorphism with risk of second primary malignancy in patients with squamous cell carcinoma of the head and neck

BACKGROUND

p53 plays a critical role in cellular anticancer mechanisms, and has been correlated with second primary malignancy (SPM) development. A common polymorphism in codon 72 of p53 results in an amino acid substitution and could influence p53 function. The authors hypothesized that p53 codon 72 polymorphism may be associated with risk of SPMs and SPM-free survival among patients with squamous cell carcinoma of the head and neck (SCCHN).

METHODS

A total of 1271 patients, who were diagnosed with incident SCCHN between May 1995 and January 2007, were genotyped and observed for SPM development. Log-rank test and Cox proportional hazard models were used to compare SPM-free survival and SPM risk between the different genotype groups.

RESULTS

The authors found significantly reduced SPM-free survival for patients with variant proline (Pro) 72 allele compared with patients with arginine (Arg) 72 homozygous genotype (log-rank test, P = .005). Compared with SCCHN patients with the p53 72Arg/Arg genotype, there was a significantly greater risk of SPM associated with the p53 72Arg/Pro genotype (hazard ratio [HR], 1.75; 95% confidence interval [CI], 1.17-2.61) and combined p53 72Arg/Pro + Pro/Pro (HR, 1.58; 95% CI, 1.07-2.34). Furthermore, stratification analyses showed that the risk of SPM associated with p53 variant genotypes (Arg/Pro + Pro/Pro) was more pronounced in several subgroups.

CONCLUSIONS

p53 codon 72 polymorphism could be a risk marker for genetic susceptibility to SPM in patients with primary SCCHN.

p53 immunocytochemistry and TP53 gene mutations in patients with chronic hepatitis C virus (HCV) infection

Chronic infection with hepatitis C virus (HCV) is regarded as a risk factor for hepatocellular carcinoma (HCC), mostly in patients with liver cirrhosis. Present study aimed at evaluation of cellular expression of p53 protein, genetic TP53 changes in liver samples and anti-p53 in serum of patients with chronic hepatitis C virus infection. The expression of p53 protein were analysed by immunocytochemistry in liver biopsies from adult patients with chronic, long-lasting hepatitis C. In order to detect TP53 mutations, PCR/SSCP and sequencing were performed. Antibodies against p53 in serum were determined using enzyme immunoassay (ELISA).In two out of 14 examined patients TP53 point mutations were detected in the liver samples. In the first patient, a substitution of C to T was demonstrated in position 1 of the codon 250, resulting in substitution of proline by serine. The other patient carried a substitution of C to G in position 13274 of the intron 6. The patient carrying mutation in the codon 250 demonstrated morphological traits of liver cirrhosis and had high number of p53-immunoreactive cell nuclei in tissue. None of the patients manifested elevated titres of serum anti-p53. In the liver, significant positive correlations were disclosed between expression of p53 on one hand and grading and staging on the other. A negative correlation was disclosed between cellular expression of p53 and duration time of infection. In conclusions, genetic changes in TP53 can be detected also in non-neoplastic lesions linked to chronic HCV infection.

Tumour suppressors in liver carcinogenesis

The circuitous cell signalling pathways of hepatocytes comprise several factors that operate to downgrade or even interrupt the transmission of a given signal. These down-regulating influences are essential to keep cell proliferation and cell survival in check and if impaired, can alter a delicate balance in favour of cell proliferation. Each signalling pathway that has been implicated in carcinogenesis is influenced by both oncogenic factors that promote tumour growth when activated as well as tumour suppressor proteins that have to be impaired to favour tumour growth. This summary of the Tumour Suppressors in Liver Carcinogenesis Symposium held at the 2007 EASL Annual Meeting discusses four pathways with pre-eminent tumour suppressor activity, each involved in hepatocarcinogenesis: p53, mTOR, beta-catenin and hedgehog.