p53 polymorphisms: cancer implications

p53 Stabilization induces cell growth inhibition and affects IGF2 pathway in response to radiotherapy in adrenocortical cancer cells

Adrenocortical carcinoma (ACC) is a very rare endocrine tumour, with variable prognosis, depending on tumour stage and time of diagnosis. However, it is generally fatal, with an overall survival of 5 years from detection. Radiotherapy usefulness for ACC treatment has been widely debated and seems to be dependent on molecular alterations, which in turn lead to increased radio-resistance. Many studies have shown that p53 loss is an important risk factor for malignant adrenocortical tumour onset and it has been reported that somatic mutations in TP53 gene occur in 27 to 70% of adult sporadic ACCs. In this study, we investigated the role of somatic mutations of the TP53 gene in response to ionizing radiation (IR). We studied the status of p53 in two adrenocortical cell lines, H295R and SW-13, harbouring non-functioning forms of this protein, owing to the lack of exons 8 and 9 and a point mutation in exon 6, respectively. Moreover, these cell lines show high levels of p-Akt and IGF2, especially H295R. We noticed that restoration of p53 activity led to inhibition of growth after transient transfection of cells with wild type p53. Evaluation of their response to IR in terms of cell proliferation and viability was determined by means of cell count and TUNEL assay.(wt)p53 over-expression also increased cell death by apoptosis following radiation in both cell lines. Moreover, RT-PCR and Western blotting analysis of some p53 target genes, such as BCL2, IGF2 and Akt demonstrated that p53 activation following IR led to a decrease in IGF2 expression. This was associated with a reduction in the active form of Akt. Taken together, these results highlight the role of p53 in response to radiation of ACC cell lines, suggesting its importance as a predictive factor for radiotherapy in malignant adrenocortical tumours cases.

Monodisperse double-walled microspheres loaded with chitosan-p53 nanoparticles and doxorubicin for combined gene therapy and chemotherapy

We have designed and evaluated a dual anticancer delivery system to provide combined gene therapy and chemotherapy. Double-walled microspheres consisting of a poly(d,l-lactic-co-glycolic acid) (PLGA) core surrounded by a poly(lactic acid) (PLA) shell were fabricated via the precision particle fabrication (PPF) technique. We make use of the advantages of double-walled microspheres to deliver chitosan-DNA nanoparticles containing the gene encoding the p53 tumor suppressor protein (chi-p53) and/or doxorubicin (Dox), loaded in the shell and core phases, respectively. Different molecular weights of PLA were used to form the shell layer for each formulation. The microspheres were monodisperse with a mean diameter of 65 to 75 μm and uniform shell thickness of 8 to 17 μm. Blank and Dox-loaded microspheres typically exhibited a smooth surface with relatively few small pores, while chi-microspheres containing p53 nanoparticles, with and without Dox, presented rough and porous surfaces. The encapsulation efficiency of Dox was significantly higher when it was encapsulated alone compared to co-encapsulation with chi-p53 nanoparticles. The encapsulation efficiency of chi-p53 nanoparticles, on the other hand, was not affected by the presence of Dox. As desired, chi-p53 nanoparticles were released first, followed by simultaneous release of chi-p53 nanoparticles and Dox at a near zero-order rate. Thus, we have demonstrated that the PPF method is capable of producing double-walled microspheres and encapsulating dual agents for combined modality treatment, such as gene therapy and chemotherapy.

Tumor suppression in the absence of p53-mediated cell-cycle arrest, apoptosis, and senescence

Cell-cycle arrest, apoptosis, and senescence are widely accepted as the major mechanisms by which p53 inhibits tumor formation. Nevertheless, it remains unclear whether they are the rate-limiting steps in tumor suppression. Here, we have generated mice bearing lysine to arginine mutations at one (p53(K117R)) or three (p53(3KR); K117R+K161R+K162R) of p53 acetylation sites. Although p53(K117R/K117R) cells are competent for p53-mediated cell-cycle arrest and senescence, but not apoptosis, all three of these processes are ablated in p53(3KR/3KR) cells. Surprisingly, unlike p53 null mice, which rapidly succumb to spontaneous thymic lymphomas, early-onset tumor formation does not occur in either p53(K117R/K117R) or p53(3KR/3KR) animals. Notably, p53(3KR) retains the ability to regulate energy metabolism and reactive oxygen species production. These findings underscore the crucial role of acetylation in differentially modulating p53 responses and suggest that unconventional activities of p53, such as metabolic regulation and antioxidant function, are critical for suppression of early-onset spontaneous tumorigenesis.

Alterations of the TP53 gene in gastric and esophageal carcinogenesis

TP53 genes is one of more important tumor suppressor gene, which acts as a potent transcription factor with fundamental role in the maintenance of genetic stability. The development of esophageal and gastric cancers is a multistep process resulting in successive accumulation of genetic alterations that culminates in the malignant transformation. Thus, this study highlights the participation of the main genetic alterations of the TP53 gene in esophageal and gastric carcinogenesis. Among these changes, high frequency of TP53 mutations, loss of heterozygosity (LOH), overexpression of the p53 protein, and consequently loss of p53 function, which would be early events in esophageal and gastric cancers, as well as an important biomarker of the prognosis and treatment response. Furthermore, Single Nucleotide Polymorphisms (SNPs) of TP53 have been implicated in the development and prognosis of several cancers, mainly TP53 codon 72 polymorphism whose role has been extensively studied in relation to susceptibility for esophageal and gastric cancer development.

Leukocyte p53 protein biosignature through standard-aligned two-dimensional immunoblotting

Peripheral leukocytes may reflect systemic disease and stress states through their gene expression profile. Subsequent protein analyses of leukocytes are hypothesized to provide essential information regarding systemic diseases. We have developed a protein biosignature analysis of the tumour suppressor and cell stress sensor p53 based on two-dimensional gel electrophoresis and immunoblotting, and utilize fluorescently labelled reference standards to significantly improve the alignment and comparison of biosignatures, including full-length p53 and isoforms p53β and p53γ. Analysis of the p53 biosignatures of peripheral blood mononuclear cells from 526 healthy individuals and 65 acute myeloid leukaemia patients indicated a novel putative p53 protein variant in a subset of individuals (227 of 526 healthy tested). The p53 variant was more distinct in the reference standard aligned biosignatures of healthy individuals, compared to the non-standard aligned leukaemia biosignatures. This approximately 2 kDa heavier variant of p53 appeared with similar frequency in leukemic and healthy test persons, without coinciding with known splice forms or post-translational modifications of p53. We propose that a standardized leukocyte protein biosignature of p53 provides a powerful research tool and indicate how p53 protein biosignatures may be used in future diagnostics. This article is part of a Special Issue entitled: Integrated omics.

Mycoepoxydiene, a fungal polyketide inhibits MCF-7 cells through simultaneously targeting p53 and NF-κB pathways

Mycoepoxydiene (MED) is a cytotoxic polyketide that is isolated from the marine fungal strain Diaporthe sp. HLY-1, which is associated with mangroves; however, the mechanism of action of MED remains unknown. Here, we report the molecular mechanisms of apoptosis activation and growth inhibition induced by MED in MCF-7 cells. The present results show that MED induces DNA damage through the production of reactive oxygen species (ROS), which resulted in the phosphorylation of H2AX and the activation of the Ataxia telangiectasia mutated kinase (ATM) and p53 signaling pathways. In addition, MED increases the accumulation of IκBα and enhances the association between IKKγ and Hsp27 via the activation of Hsp27, which eventually resulted in the inhibition of TNF-α-induced NF-κB transactivation. Therefore, we conclude that MED inhibits MCF-7 cells by simultaneously activating p53 to induce apoptosis and suppressing NF-κB to disrupt cell proliferation. Because small molecules having both of these effects are rare, further exploration of MED as an antitumor lead compound is needed.

p53 and risk of endometriosis in Indian women

AIM

To investigate the role of loss of heterozygosity (LOH), single nucleotide polymorphisms (SNPs), and the expression of gene p53 in the pathogenesis of endometriosis.

METHODS

LOH at the p53 gene locus (17p13.1) was examined in matched ectopic and eutopic endometrial tissues from 31 endometriosis patients by polymerase chain reaction (PCR)-GeneScan analysis. The genotyping of selected p53 SNPs (n=10) was carried out on genomic DNA of blood from endometriosis patients (n=720) and controls (n=500) by PCR sequencing. The p53 expression levels were analyzed in the endometrial tissues from endometriosis patients (n=5) and controls (n=4) by Western blot and immunohistochemical analysis.

RESULTS

LOH was observed at the 17p13.1 locus (38.7%) in the ectopic endometrium but not in the eutopic endometrium of patients. The genotype (p=0.909) and allele (p=0.729) distribution of the p53 codon Arg72Pro polymorphism was not significantly different between patients and controls. The polymorphism was not observed at codon 47 along the other SNPs studied. There was no preferential loss of either "Arg72" or "Pro72" alleles among the LOH-positive heterozygous cases. In addition, decreased p53 expression was observed more often in the endometrium of patients than in controls.

CONCLUSIONS

p53 SNPs are not associated with endometriosis in Indian women. However, LOH and reduced expression of p53 are related with the risk of endometriosis in Indian women.

Interactions of miR-34b/c and TP53 polymorphisms on the risk of intracranial aneurysm

Several lines of evidence indicate that inflammatory processes play a key role in the happening and development of intracranial aneurysm (IA). Recently, polymorphisms in the TP53 gene were shown to be associated with inflammation and inflammatory disease. The aim of this study was to investigate the interactions of miR-34b/c and TP53 Arg72-Pro polymorphisms on the risk of IA in a Chinese population. A total of 590 individuals (including 164 patients with IA and 426 controls) were involved in this study. The polymorphisms (i.e., miR-34b/c rs4938723 and TP53 Arg72-Pro) were genotyped by polymerase chain reaction-restriction fragment length polymorphism assay and DNA sequencing. We found that the CC genotype of miR-34b/c rs4938723 was significantly associated with a decreased risk of IA compared with the TT genotype. Moreover, a significant gene interaction of the carriers with the combined genotypes of miR-34b/c rs4938723CC and TP53 Arg72Pro CG/CC/GG had a decreased risk of IA, compared with those carrying miR-34b/c rs4938723CT/TT+TP53 Arg72Pro GG/CG/CC combined genotypes. These findings suggest that the miR-34b/c rs4938723CC and TP53 Arg72-Pro polymorphisms may be involved in the susceptibility to IA.

TP53 codon 72 polymorphism in pigmentary phenotypes

The p53 protein exerts different cellular functions, and recent findings have demonstrated its influence on the cascade of skin pigmentation during UV exposure. Among TP53 gene polymorphisms, the most studied is the G to C transversion in exon 4 at codon 72, which results in three distinct genotypes, Arg/Arg, Pro/Pro and Arg/Pro, each one encoding different p53 isoforms. Therefore, this study aimed to determine the relationship between TP53 codon 72 polymorphism and skin protection against sunburn. Genomic DNA was extracted from peripheral blood samples and genotyping was performed by PCR and confirmed by restriction enzyme digestion. The genotype frequency was 50% for Arg/Arg and 14.6% for Pro/Pro genotype. The frequency of heterozygous subjects was 35.4%. In our population, p53 genotypes were in Hardy-Weinberg (HW) equilibrium (X2 HM less than 3.84), showing a predominance of arginine allele (total Arg allele frequency of 68%). No significant association between p53 genotype and skin colour, hair or eye colour and susceptibility to sun exposure was found. However, further analysis demonstrated a significant association between the genotype Pro/Pro and blue/green eyes among participants who presented redness (P=0.016). Our findings indicate susceptibility to sun exposure when this phenotype (eye colour) occurs simultaneously with Pro/Pro genotype.

Triptolide sensitizes TRAIL-induced apoptosis in prostate cancer cells via p53-mediated DR5 up-regulation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising agent for cancer therapy. However, a number of prostate cancer cells exhibit high resistance to TRAIL effect. In this study, we found that Triptolide, a Chinese medicine, significantly sensitizes prostate cancer cells to TRAIL-mediated cellular apoptosis by up-regulating DR5 expression. Triptolide treatment can suppress Akt/Hdm2 signaling pathway, and lead to p53 accumulation, thereby up-regulating DR5 expression. Taken together, all evidences indicate that Triptolide may become a promising therapeutic agent that prevents the progression of prostate cancer.

The effect of Trp53 gene-dosage and parent-of-origin of inheritance on mouse gamete and embryo function in vitro

The transformation-related protein 53 (TRP53) has a canonical role as the "guardian of the genome," serving to protect against the propagation of cells with genomic damage. Autocrine trophic signals act to block the accumulation of TRP53 in the normal preimplantation embryo. Culture of the early embryo at limiting dilutions in simple defined media limits autocrine signaling, resulting in the accumulation of TRP53. This TRP53 reduces the rate of development of embryos. In this study we show that deletion of the Trp53 gene improved development in vitro in a dose-dependent manner. Development to morphological blastocysts increased as the dose of Trp53 was reduced, and this was accompanied by a Trp53-dependent increase in the allocation of cells to the inner cell mass. The intermediate developmental response of heterozygous mice provides evidence for haploinsufficiency of this trait. This haploinsufficiency was evident irrespective of the parent-of-origin of the null allele; however, zygotes with paternal inheritance of the Trp53-null allele had better development in vitro than those with maternal inheritance. There was a beneficial effect of the Trp53-null allele on the number of oocytes released by Trp53(+/-) females, and heterozygous males produced higher fertilization rates than controls, although this was independent of the genotype of the fertilizing sperm. The study shows that ovulation induction or culture of embryos in limiting conditions creates conditions that favor the early development of embryos inheriting loss of Trp53 function. This occurs even in the heterozygous state, showing that the conditions provide a potential basis for accelerated accumulation of deleterious mutations within a population.

The tumour suppressor p53 is frequently nonfunctional in Sézary syndrome

BACKGROUND

Primary cutaneous T-cell lymphomas (CTCLs) are a heterogeneous group with Sézary syndrome (SS) as one of the most aggressive variants. Recently, we identified a loss of E2A as a recurrent event in SS, which enhanced proliferation via upregulation of the proto-oncogene MYC. MYC-induced transformation usually requires deleterious alterations of key apoptotic genes including p53; however, p53 functionality and mutation status in SS are unclear.

OBJECTIVES

We investigated functionality of p53 signalling by pharmacological treatment with the MDM2 antagonist nutlin-3, which might result in p53 activation. Furthermore, we analysed the TP53 mutation status in CTCL cell lines and highly purified tumour cells from patients with SS by mRNA and DNA sequencing.

METHODS

We analysed the apoptosis induction due to nutlin-3 treatment in various SS cell lines and primary patient samples by annexin V/propidium iodide staining. Induction of p53 target genes was analysed by immunoblotting, and TP53 was sequenced at the mRNA and DNA level.

RESULTS

We identified various TP53 mutations and an impaired p53 signalling in the vast majority of the investigated cell lines and primary SS cells.

CONCLUSIONS

In accordance with the importance of MYC deregulation in SS, p53 signalling is frequently nonfunctional in SS. However, although most likely ineffective as exclusive treatment in SS, it remains possible that pharmacological p53 activation could be beneficial in combination with other approaches including classical chemotherapeutics.

AKT-dependent phosphorylation of Niban regulates nucleophosmin- and MDM2-mediated p53 stability and cell apoptosis

Although Niban is highly expressed in human cancer cells, the cellular functions of Niban remain largely unknown. We demonstrate here that ultraviolet irradiation induces phosphorylation of Niban at S602 by AKT, which increases the association of Niban with nucleophosmin and disassociation of nucleophosmin from the MDM2 complex. This leads to the promotion of MDM2-p53 interaction and subsequent p53 degradation, thereby providing an antiapoptotic effect. Conversely, depletion of or deficiency in Niban expression promotes stabilization of p53 with increased cell apoptosis. Our findings illustrate a pivotal role for AKT-mediated phosphorylation of Niban in protecting cells from genotoxic stress-induced cell apoptosis.

Is cellular senescence an example of antagonistic pleiotropy?

It is generally accepted that the permanent arrest of cell division known as cellular senescence contributes to aging by an antagonistic pleiotropy mechanism: cellular senescence would act beneficially early in life by suppressing cancer, but detrimentally later on by causing frailty and, paradoxically, cancer. In this review, we show that there is room to rethink this common view. We propose a critical appraisal of the arguments commonly brought in support of it, and we qualitatively analyse published results that are of relevance to understand whether or not cellular senescence-associated genes really act in an antagonistic-pleiotropic manner in humans.

Alterations of the p53 and PIK3CA/AKT/mTOR pathways in angiosarcomas: a pattern distinct from other sarcomas with complex genomics

BACKGROUND

The p53 and phosphoinositide-3-kinase, catalytic, alpha polypeptide/v-akt murine thymoma viral oncogene homolog/mechanistic target of rapamycin (PIK3CA/AKT/mTOR) pathways frequently are altered in sarcoma with complex genomics, such as leiomyosarcoma (LMS) or undifferentiated pleomorphic sarcoma (UPS). The scale of genetic abnormalities in these pathways remains unknown in angiosarcoma (AS).

METHODS

The authors investigated the status of critical genes involved in the p53 and PIK3CA/AKT/mTOR pathways in a series of 62 AS.

RESULTS

The mutation and deletion rates of tumor protein 53 (TP53) were 4% and 0%, respectively. Overexpression of p53 was detected by immunohistochemistry in 49% of patients and was associated with inferior disease-free survival. Although p14 inactivation or overexpression of the human murine double minute homolog (HDM2) were frequent in LMS and UPS and could substitute for TP53 mutation or deletion, such alterations were rare in angiosarcomas. Phosphorylated ribosomal protein S6 kinase (p-S6K) and/or phosphorylated eukaryotic translation initiation factor 4E binding protein 1 (p-4eBP1) overexpression was observed in 42% of patients, suggesting frequent activation of the PIK3CA/AKT/mTOR pathway in angiosarcomas. Activation was not related to intragenic deletion of phosphatase and tensin homolog (PTEN), an aberration that is frequent in LMS and UPS but absent in angiosarcomas.

CONCLUSIONS

The current results indicated that angiosarcomas constitute a distinct subgroup among sarcomas with complex genomics. Although TP53 mutation and PTEN deletion are frequent in LMS and UPS, these aberrations are rarely involved in the pathogenesis of angiosarcoma.

Mutations and polymorphisms in TP53 gene--an overview on the role in colorectal cancer

A functionally normal TP53 is essential to protect organisms from developing cancer. Somatic mutations in the gene represent one of the highest recurring perturbations in human tumours, including colorectal cancer (CRC). However, the variegated phenotype of wide spectrum of somatic mutations in TP53 and the complexity of the disease prevent a straight interpretation of the mutational analysis in tumours. In addition to the presence of somatic mutations, polymorphic features of the gene may also contribute to alteration of the normal TP53 functioning and variants, mainly in the form of single nucleotide polymorphisms, can be expected to impact susceptibility to sporadic CRC. In the present study, we reviewed the potential role of alterations in the TP53 gene, both somatic mutations and inherited sequence variations, in predisposition to CRC and in the prognosis and response to therapy. The available data from association studies have mostly shown contradictory outcomes. The majority of the studies were based on limited sample sizes and focussed on a limited number of polymorphisms, with main being the rs1042522 (Arg72Pro). Thus far, there is no possible generalisation of the role of TP53 as also a predictor of therapeutic response and prognosis. The effects of TP53, and its abnormalities, on the response of tumours to cytotoxic drugs, radiation and chemoradiation are complex. However, from studies it is emerging that the inherited genetics of TP53 pathway components could be utilised to further define patient populations in their abilities to induce p53 activity in response to either DNA damaging or p53-targeted therapies.

Analysis of Tp53 codon 72 polymorphisms, Tp53 mutations, and HPV infection in cutaneous squamous cell carcinomas

Background

Non-melanoma skin cancers are one of the most common human malignancies accounting for 2–3% of tumors in the US and represent a significant health burden. Epidemiology studies have implicated Tp53 mutations triggered by UV exposure, and human papilloma virus (HPV) infection to be significant causes of non-melanoma skin cancer. However, the relationship between Tp53 and cutaneous HPV infection is not well understood in skin cancers. In this study we assessed the association of HPV infection and Tp53 polymorphisms and mutations in lesional specimens with squamous cell carcinomas.

Methods

We studied 55 cases of histologically confirmed cutaneous squamous cell carcinoma and 41 controls for the presence of HPV infection and Tp53 genotype (mutations and polymorphism).

Results

We found an increased number of Tp53 mutations in the squamous cell carcinoma samples compared with perilesional or control samples. There was increased frequency of homozygous Tp53-72R polymorphism in cases with squamous cell carcinomas, while the Tp53-72P allele (Tp53-72R/P and Tp53-72P/P) was more frequent in normal control samples. Carcinoma samples positive for HPV showed a decreased frequency of Tp53 mutations compared to those without HPV infection. In addition, carcinoma samples with a Tp53-72P allele showed an increased incidence of Tp53 mutations in comparison carcinomas samples homozygous for Tp53-72R.

Conclusions

These studies suggest there are two separate pathways (HPV infection and Tp53 mutation) leading to cutaneous squamous cell carcinomas stratified by the Tp53 codon-72 polymorphism. The presence of a Tp53-72P allele is protective against cutaneous squamous cell carcinoma, and carcinoma specimens with Tp53-72P are more likely to have Tp53 mutations. In contrast Tp53-72R is a significant risk factor for cutaneous squamous cell carcinoma and is frequently associated with HPV infection instead of Tp53 mutations. Heterozygosity for Tp53-72R/P is protective against squamous cell carcinomas, possibly reflecting a requirement for both HPV infection and Tp53 mutations.

Dysfunction of the TP53 tumor suppressor gene in lymphoid malignancies

Mutations of the TP53 gene and dysregulation of the TP53 pathway are important in the pathogenesis of many human cancers, including lymphomas. Tumor suppression by p53 occurs via both transcription-dependent activities in the nucleus by which p53 regulates transcription of genes involved in cell cycle, DNA repair, apoptosis, signaling, transcription, and metabolism; and transcription-independent activities that induces apoptosis and autophagy in the cytoplasm. In lymphoid malignancies, the frequency of TP53 deletions and mutations is lower than in other types of cancer. Nonetheless, the status of TP53 is an independent prognostic factor in most lymphoma types. Dysfunction of TP53 with wild-type coding sequence can result from deregulated gene expression, stability, and activity of p53. To overcome TP53 pathway inactivation, therapeutic delivery of wild-type p53, activation of mutant p53, inhibition of MDM2-mediated degradation of p53, and activation of p53-dependent and -independent apoptotic pathways have been explored experimentally and in clinical trials. We review the mechanisms of TP53 dysfunction, recent advances implicated in lymphomagenesis, and therapeutic approaches to overcoming p53 inactivation.

Potential genotype-specific single nucleotide polymorphism interaction of common variation in p53 and its negative regulator mdm2 in cholangiocarcinoma susceptibility

Aberrant cell cycle control and apoptosis deregulation are involved in biliary carcinogenesis. The tumor suppressor gene p53 and its key negative regulator murine double minute 2 (mdm2) cooperate in modulating these basic cell functions and germline p53 alteration promotes cholangiocarcinoma (CCA) formation in animal models. The potential association between common functional genetic variation in p53 (SNP72 G/C) and mdm2 (SNP309 T/G) and susceptibility to bile duct cancer, however, has not been studied. p53/SNP72 G/C (rs1042522) and mdm2/SNP309 T/G (rs2279744) were genotyped in 182 Caucasian CCA patients and 350 controls using TaqMan assays. Allelic and genotypic differences, including exploratory data analyses (according to gender, tumor localization, early onset and genotypic interactions) were compared in contingency tables using the χ(2) and Fisher's exact tests. The overall comparison of allele and genotype frequencies yielded no significant association between either SNP and CCA susceptibility. Similarly, gender- and localization-specific analyses did not reveal deviations in allelic or genotypic distributions. In carriers of the low-apoptotic p53 genotype CC, the mdm2 SNP309 T allele conferred borderline significant CCA risk [P=0.049; odds ratio (OR), 4.36; 95% CI, 0.92-20.77]. Power analysis confirmed adequate statistical power to exclude major SNP effects (each >97% for OR 1.7). Collectively, the results we obtained from the largest European CCA cohort do not support the hypothesis of a prominent role of common p53 and mdm2 variation in the genetic susceptibility to bile duct cancer. However, epistatic effects may modulate genetic CCA risk in individual subsets.

Functional and clinical characterization of the putative tumor suppressor WWOX in non-small cell lung cancer

INTRODUCTION

The oxidoreductase WWOX was initially described as a putative tumor suppressor in breast cancer. Non-small cell lung cancers (NSCLCs) frequently show aberrant WWOX expression. Herein, we characterized WWOX at a functional level in preclinical NSCLC models and in primary NSCLC biopsies.

METHODS

The human wild-type (wt) WWOX complementary DNA and a mutant WWOX with structurally disrupted short-chain dehydrogenase/reductase domain were conditionally expressed at physiological levels in several human NSCLC models. Resulting transgenic cell populations were analyzed with respect to clonogenic survival and apoptosis sensitivity in vitro and tumor growth in immune-deficient mice. Tissue microarrays prepared from surgically resected primary human NSCLC tumors were studied to correlate intratumoral WWOX expression with patient outcomes.

RESULTS

Conditional expression of wt WWOX, but not mutant WWOX, suppressed clonogenic survival of NSCLC cells in vitro and tumor growth in vivo. In addition, preserved intratumoral WWOX expression was associated with improved outcome in a cohort of 85 patients with surgically resected NSCLC. Unexpectedly, wt WWOX failed to sensitize NSCLC cells to various apoptotic stimuli but robustly protected against apoptosis induced by inhibitors of growth factor signal transduction.

CONCLUSIONS

WWOX acts as a tumor suppressor in human NSCLC models in a short-chain dehydrogenase/reductase domain-dependent manner. This activity is independent of sensitization to apoptotic cell death. WWOX expression as detected by immunohistochemistry may be a prognostic biomarker in surgically resected, early-stage NSCLC.

Towards an understanding of the role of p53 in adrenocortical carcinogenesis

Adrenocortical carcinoma (ACC) is recognized to be a component tumor of the Li Fraumeni Syndrome (LFS), a familial cancer predisposition resulting from germline mutations in the p53 tumor-suppressor. p53 activity is tightly regulated by multiple post-translational mechanisms, disruption of which may lead to tumorigenesis. ACC is present in disproportionately high rates among p53-mutation carriers, suggesting tissue-specific manifestations of p53 deficiency. Additionally, p53-associated ACC demonstrates a strong predominance in infants and children. Several of the p53 alleles associated with pediatric ACC, however, retain significant wild-type activity and demonstrate incomplete penetrance, a finding distinct from other LFS-component tumors. In this review, we discuss the relationship between p53 and adrenocortical carcinogenesis, with specific focus on disease-specific alleles, tumorigenesis in the context of adrenal development and potential therapeutic approaches to p53-associated ACC.

Combined effects of E2F1 and E2F2 polymorphisms on risk and early onset of squamous cell carcinoma of the head and neck

Deregulated expression of most members of the E2F family has been detected in many human cancers. We examined the association of common single nucleotide polymorphisms (SNPs) of E2F transcription factors 1 and 2 (E2F1 and E2F2) with risk of squamous cell carcinoma of the head and neck (SCCHN) in 1,096 SCCHN patients and 1,090 cancer-free controls. We genotyped 10 selected SNPs in E2F1 and E2F2, including those at the near 5'-untranslated region (UTR), microRNA (miRNA)-binding sites at the near 3'-UTR and tagSNPs according to bioinformatics analysis. Although none of the selected SNPs alone was significantly associated with risk of SCCHN, there was a statistically significantly increased risk of SCCHN associated with the combined risk genotypes (i.e., rs3213182 AA, rs3213183 GG, rs3213180 GG, rs321318121 GG, rs2742976 GT+TT, rs6667575 GA+AA, rs3218203 CC, rs3218148 AA, rs3218211 CC, and rs3218123 GT+TT). Compared with those with 0-4 risk genotypes, an increased risk was observed for those who carried 5-8 risk genotypes (adjusted OR = 1.04; 95% CI = 0.86-1.26) and 9-10 risk genotypes (adjusted OR = 1.62; 95% CI = 1.14-2.30) in a dose-response manner (P = 0.045). Furthermore, the joint effect was more pronounced among patients with oropharyngeal cancer, younger adults (≤57 yr old), men, non-smokers, non-drinkers, and individuals with family history of cancer in first-degree relatives. Additionally, we also observed that those with 5-10 risk genotypes had an earlier SCCHN onset than those with 0-4 risk genotypes, particularly for non-smokers and/or non-drinkers. We concluded that E2F1 and E2F2 genetic variants may jointly play important roles in head and neck carcinogenesis.

The p53 codon 72 polymorphism is associated with risk and early onset of breast cancer among Saudi women

Breast cancer has a major impact on the health of women worldwide. In the Kingdom of Saudi Arabia (KSA), breast cancer incidence is on the increase and is characterized by early onset and aggressiveness. Owing to the importance of the TP53 gene in breast carcinogenesis, we analyzed the possible link between TP53 single nucleotide polymorphisms (SNPs) and the risk of breast cancer in Saudi women by direct sequencing of the TP53 gene exon 4 from 100 breast cancer tissues. The proportion of the polymorphic forms of SNP72 in the Saudi breast cancer patients were: Arg/Arg (RR), 39%; Pro/Pro (PP), 36%; and Arg/Pro (RP), 25%. The frequencies of these forms in disease-free Saudi women were 7.59, 22.22 and 60.19%, respectively. This indicates that the RR form of the codon 72 polymorphism is a potential risk factor, whereas the RP form is a protection factor against breast cancer among Saudi women (p=0.0001). Moreover, the results have shown that the p53 R72P SNP is significantly associated with the early onset of breast cancer in the Saudi population (p=0.0138). However, the codon 47 polymorphism appears to have no role in this disease among Saudi women. These results indicate that the TP53 gene could play a major role in breast carcinogenesis and the early onset of the disease among Saudi women.

Comparison of hepatocellular carcinoma in American and Asian patients by tissue array analysis

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Although some epidemiologic and etiologic differences between Asian and Western HCC are known, detailed comparative studies with pathologic correlations have not been performed.

METHODS

Paraffin sections of resected HCC specimens from Memorial Sloan-Kettering Cancer Center and Korea University Medical Center were used to construct tissue microarrays. Immunohistochemical staining of microarray sections was performed using antibodies against markers of proliferation and regulators of cell cycle. Patient data were correlated with staining results.

RESULTS

When comparing both cohorts, significant differences were found in expression of p53 and MDM2. In the Asian group, more frequent positive staining for p53 (24%) was observed compared with the American group (9%; P = 0.037). For MDM2, 26% of American cases stained positive compared with 2% of Asian cases (P = 0.0003). No significant differences were found in expression of Ki67, p21, p27, cyclin D1, or bcl2. Female gender, vascular invasion, and lack of viral hepatitis infection correlated with positive MDM2 staining.

CONCLUSION

These data likely correlate with differences in molecular pathogenesis of HCC based on racial and regional differences. These findings may have implications in choice of molecular targeted therapies based on patient ethnicity.

The miR-29 family: genomics, cell biology, and relevance to renal and cardiovascular injury

The human miR-29 family of microRNAs has three mature members, miR-29a, miR-29b, and miR-29c. miR-29s are encoded by two gene clusters. Binding sites for several transcriptional factors have been identified in the promoter regions of miR-29 genes. The miR-29 family members share a common seed region sequence and are predicted to target largely overlapping sets of genes. However, the miR-29 family members exhibit differential regulation in several cases and different subcellular distribution, suggesting their functional relevance may not be identical. miR-29s directly target at least 16 extracellular matrix genes, providing a dramatic example of a single microRNA targeting a large group of functionally related genes. Strong antifibrotic effects of miR-29s have been demonstrated in heart, kidney, and other organs. miR-29s have also been shown to be proapoptotic and involved in the regulation of cell differentiation. It remains to be explored how various cellular effects of miR-29s determine functional relevance of miR-29s to specific diseases and how the miR-29 family members may function cooperatively or separately.

Codon 72 polymorphism (rs1042522) of TP53 is associated with changes in diastolic blood pressure over time

p53 is involved in stress response, metabolism and cardiovascular functioning. The C-allele of rs1042522 in the gene encoding for p53 is associated with longevity and cancer. In this study, we aimed to investigate the association of rs1042522 with changes in blood pressure, BMI and waist circumference using a longitudinal approach. Rs1042522 was analyzed in two longitudinal studies; the Doetinchem Cohort Study (DCS) and the Botnia Prospective Study (BPS). Changes in quantitative traits over time were investigated according to rs1042522 genotypes. An association between rs1042522 and changes in diastolic blood pressure (DBP) in the DCS over time was observed (P=0.004). Furthermore, a borderline significant association was detected with changes in waist circumference over time (P=0.03). These findings were also observed in the BPS (P=0.02 and P=0.05). The C/C-genotype (Pro/Pro) showed the most moderate time-related increase for the studied endpoints. Furthermore, data from the BPS suggested that the C/C-genotype protects against increases in glucose levels over time at 30 and 60 min during oral glucose tolerance test (P=0.01 and P=0.02). In conclusion, we found an association between the C/C-genotype of rs1042522 and changes in DBP and waist circumference over time. This might contribute to the longevity phenotype observed for the same genotype by others.

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

Studies investigating the relationship between TP53 Arg72Pro polymorphism and endometrial cancer risk reported conflicting results. To explore a more precise estimate of the effect of this polymorphism on endometrial carcinogenesis, a meta-analysis was performed by searching eligible studies in PubMed. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the association for codominant model (Arg/Arg vs. Pro/Pro, Arg/Pro vs. Pro/Pro), dominant model (Arg/Arg+Arg/Pro vs. Pro/Pro), and recessive model (Arg/Arg vs. Arg/Pro+Pro/Pro), respectively. Subgroup analyses were performed by Hardy-Weinberg equilibrium (HWE) in controls, the specimen of cases for determining TP53 genotypes, sample size, the source of control and case groups, and ethnicity. We identified 8 case-control studies involving 2,154 subjects for this meta-analysis. Overall, no evidence of association was observed between TP53 genotypes and endometrial cancer risk in all genetic models (Arg/Arg vs. Pro/Pro: OR=0.98, 95% CI: 0.69-1.39, P=0.90; Arg/Pro vs. Pro/Pro: OR=1.00, 95% CI: 0.71-1.42, P=0.98; dominant model: OR=0.99, 95% CI: 0.71-1.38, P=0.95; recessive model: OR=1.06, 95% CI: 0.80-1.41, P=0.95). Stratified analyses also detected no significant association in any subgroup, except among those studies with controls deviated from HWE in recessive model (OR=1.60, 95% CI: 1.07-2.39). In conclusion, we did not observe any evidence for a role of TP53 Arg72Pro polymorphism in endometrial cancer. The reported significant association between this polymorphism and endometrial cancer risk may be due to methodological errors such as selection bias, small sample size, Type I error, and population stratification.

MMP9 expression in oesophageal adenocarcinoma is upregulated with visceral obesity and is associated with poor tumour differentiation

Overweight and obesity is linked to increased incidence and mortality of many cancer types. Of all cancers, oesophageal adenocarcinoma (OAC) displays one of the strongest epidemiological links with obesity, accounting for up to 40% of cases, but molecular pathways driving this association remain largely unknown. This study aimed to elucidate mechanisms underpinning the association of obesity and cancer, and to determine if visceral obesity is associated with aggressive tumour biology in OAC. Following co-culture with visceral adipose tissue explants, expression of genes involved in tumour cell invasion and metastasis (matrix metalloproteinase (MMP)2 and MMP9) were upregulated between 10-fold (MMP2) and 5000-fold (MMP9), and expression of tumour suppressor p53 was downregulated 2-fold in OAC cell lines. Western blotting confirmed these results at the protein level, while zymographic analysis detected increased activity of MMPs in OAC cell lines following co-culture with adipose tissue explants. When OAC cell lines were cultured with adipose tissue conditioned media (ACM) from visceral adipose tissue, increased proliferative, migratory and invasive capacity of tumour cells was observed. In OAC patient tumour biopsies, elevated gene expression of MMP9 was associated with visceral obesity, measured by visceral fat area, while increased gene expression of MMP9 and decreased gene expression of tumour suppressor p53 was associated with poor tumour differentiation. These novel data highlight an important role for visceral obesity in upregulation of pro-tumour pathways contributing to aggressive tumour biology, and may ultimately lead to development of stratified treatment for viscerally obese OAC patients.

Proteasomal degradation of p53 by human papillomavirus E6 oncoprotein relies on the structural integrity of p53 core domain

The E6 oncoprotein produced by high-risk mucosal HPV stimulates ubiquitinylation and proteasome-dependent degradation of the tumour suppressor p53 via formation of a trimeric complex comprising E6, p53, and E6-AP. p53 is also degraded by its main cellular regulator MDM2. The main binding site of p53 to MDM2 is situated in the natively unfolded N-terminal region of p53. By contrast, the regions of p53 implicated in the degradation by viral E6 are not fully identified to date. Here we generated a series of mutations (Y103G, Y107G, T155A, T155V, T155D, L264A, L265A) targeting the central folded core domain of p53 within a region opposite to its DNA-binding site. We analysed by in vitro and in vivo assays the impact of these mutations on p53 degradation mediated by viral E6 oncoprotein. Whereas all mutants remained susceptible to MDM2-mediated degradation, several of them (Y103G, Y107G, T155D, L265A) became resistant to E6-mediated degradation, confirming previous works that pointed to the core domain as an essential region for the degradation of p53. In parallel, we systematically checked the impact of the mutations on the transactivation activity of p53 as well as on the conformation of p53, analysed by Nuclear Magnetic Resonance (NMR), circular dichroism (CD), and antibody probing. These measurements suggested that the conformational integrity of the core domain is an essential parameter for the degradation of p53 by E6, while it is not essential for the degradation of p53 by MDM2. Thus, the intracellular stability of a protein may or may not rely on its biophysical stability depending on the degradation pathway taken into consideration.

Report from the fifth National Cancer Institute Mouse Models of Human Cancers Consortium Nervous System Tumors Workshop

Cancers of the nervous system are clinically challenging tumors that present with varied histopathologies and genetic etiologies. While the prognosis for the most malignant of these tumors is essentially unchanged despite decades of basic and translational science research, the past few years have witnessed the identification of numerous targetable molecular alterations in these cancers. With the advent of advanced genomic sequencing methodologies and the development of accurate small-animal models of these nervous system cancers, we are now ideally positioned to develop personalized therapies that target the unique cellular and molecular changes that define their formation and drive their continued growth. Recently, the National Cancer Institute convened a workshop to advance our understanding of nervous system cancer mouse models and to inform clinical trials by reconsidering these neoplasms as complex biological systems characterized by heterogeneity at all levels.

LQTS-associated mutation A257G in α1-syntrophin interacts with the intragenic variant P74L to modify its biophysical phenotype

The SNTA1-encoded α1-syntrophin (SNTA1) missense mutation, p.A257G, causes long QT syndrome (LQTS) by pathogenic accentuation of Nav1.5's sodium current (I_Na). Subsequently, we found p.A257G in combination with the SNTA1 polymorphism, p.P74L in 4 victims of sudden infant death syndrome (SIDS) as well as in 3 adult controls. We hypothesized that p.P74L-SNTA1 could functionally modify the pathogenic phenotype of p.A257G-SNTA1, thus explaining its occurrence in non-LQTS populations. The SNTA1 variants p.P74L, p.A257G, and the combination variant p.P74L/p.A257G were engineered using PCR-based overlap-extension and were co-expressed heterologously with SCN5A in HEK293 cells. I_Na was recorded using the whole-cell method. Compared to wild-type (WT), the significant increase in peak I_Na and window current found with p.A257G was reversed by the intragenic variant p.P74L (p.P74L/p.A257G). These results report for the first time the intragenic rescue of an LQT-associated SNTA1 mutation when found in combination with the SNTA1 polymorphism p.P74L, suggesting an ever-increasing picture of complexity in terms of genetic risk stratification for arrhythmia.

Inhibitor of growth-4 mediates chromatin modification and has a suppressive effect on tumorigenesis and innate immunity

Inhibitor of growth-4 (ING4) is a member of the ING family and acts as a tumor suppressor protein. ING4 is a promising candidate for cancer research due to its anti-angiogenic function and its role in the inhibition of cell migration, cell cycle, and induction of apoptosis. Interaction of this protein with the histone acetyl transferase complex plays a vital role in the regulation of multiple nuclear factor kappa light chain enhancer of activated B cells response elements and thus in the regulation of innate immunity. Splice variants of ING4 have different binding affinities to target sites, which results in the enhancement of its functional diversity. ING4 is among the few known regulatory proteins that can directly interact with chromatin as well as with transcription factors. The influence of ING4 on tumor necrosis factor-α, keratinocyte chemoattractant, interleukin (IL)-6, IL-8, matrix metalloproteinases, cyclooxygenase-2, and IκBα expression clearly demonstrates its critical role in the regulation of inflammatory mediators. Its interaction with liprin α1 and p53 contribute to mitigate cell spreading and induce apoptosis of cancer cells. Multiple factors including breast cancer melanoma suppressor-1 are upstream regulators of ING4 and are frequently deactivated in tumor cells. In the present review, the different properties of ING4 are discussed, and its activities are correlated with different aspects of cell physiology. Special emphasis is placed on our current understanding of ING4 with respect to its influence on chromatin modification, tumorigenesis, and innate immunity.

A germline variant in the TP53 polyadenylation signal confers cancer susceptibility

To identify new risk variants for cutaneous basal cell carcinoma, we performed a genome-wide association study of 16 million SNPs identified through whole-genome sequencing of 457 Icelanders. We imputed genotypes for 41,675 Illumina SNP chip-typed Icelanders and their relatives. In the discovery phase, the strongest signal came from rs78378222[C] (odds ratio (OR) = 2.36, P = 5.2 × 10(-17)), which has a frequency of 0.0192 in the Icelandic population. We then confirmed this association in non-Icelandic samples (OR = 1.75, P = 0.0060; overall OR = 2.16, P = 2.2 × 10(-20)). rs78378222 is in the 3' untranslated region of TP53 and changes the AATAAA polyadenylation signal to AATACA, resulting in impaired 3'-end processing of TP53 mRNA. Investigation of other tumor types identified associations of this SNP with prostate cancer (OR = 1.44, P = 2.4 × 10(-6)), glioma (OR = 2.35, P = 1.0 × 10(-5)) and colorectal adenoma (OR = 1.39, P = 1.6 × 10(-4)). However, we observed no effect for breast cancer, a common Li-Fraumeni syndrome tumor (OR = 1.06, P = 0.57, 95% confidence interval 0.88-1.27).

Effects of MDM2 promoter polymorphisms and p53 codon 72 polymorphism on risk and age at onset of squamous cell carcinoma of the head and neck

Both p53 tumor suppressor and murine double minute 2 (MDM2) oncoprotein are crucial in carcinogenesis. We hypothesized that MDM2 promoter single nucleotide polymorphisms (SNPs) SNP309 T > G, A2164G, and p53 codon 72 are associated with risk and age at onset of squamous cell carcinoma of head and neck (SCCHN). We genotyped these SNPs in a study of 1,083 Caucasian SCCHN cases and 1,090 cancer-free controls. Although none of these SNPs individually had a significant effect on risk of SCCHN, nor did their combined putative risk genotypes (i.e., MDM2 SNP309 GT + GG, 2164 AA, and p53 codon 72 CC), we found that individuals with two to three risk genotypes had significantly increased risk of non-oropharyngeal cancer (OR = 1.42; 95% CI = 1.07-1.88). This increased risk was more pronounced among young subjects, men, smokers, and drinkers. In addition, female patients carrying the MDM2 SNP309 GT and GG genotypes showed a 3-yr (56.7 yr) and 9-yr (51.2 yr) earlier age at onset of non-oropharyngeal cancer (P(trend) = 0.007), respectively, compared with those carrying the TT genotype (60.1 yr). The youngest age (42.5 yr) at onset of non-oropharyngeal cancer was observed in female patients with the combined MDM2 SNP309 GG and p53 codon 72 CC genotypes. The findings suggest that MDM2 SNP309, A2164G, and p53 codon 72 SNPs may collectively contribute to non-oropharyngeal cancer risk and that MDM2 SNP309 individually or in combination with p53 codon 72 may accelerate the development of non-oropharyngeal cancer in women. Further studies with large sample sizes are warranted to validate these results.

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.

Sputum-based molecular biomarkers for the early detection of lung cancer: limitations and promise

Lung cancer is the leading cause of cancer deaths, with an overall survival of 15% at five years. Biomarkers that can sensitively and specifically detect lung cancer at early stage are crucial for improving this poor survival rate. Sputum has been the target for the discovery of non-invasive biomarkers for lung cancer because it contains airway epithelial cells, and molecular alterations identified in sputum are most likely to reflect tumor-associated changes or field cancerization caused by smoking in the lung. Sputum-based molecular biomarkers include morphology, allelic imbalance, promoter hypermethylation, gene mutations and, recently, differential miRNA expression. To improve the sensitivity and reproducibility of sputum-based biomarkers, we recommend standardization of processing protocols, bronchial epithelial cell enrichment, and identification of field cancerization biomarkers.

P53 codon 72 (Arg72Pro) polymorphism and prostate cancer risk: association between disease onset and proline genotype

The tumor suppressor gene p53 plays an important role in the stress response of the cell and is mutated in 50% of all human tumors. The p53 Arg72Pro single-nucleotide polymorphism (SNP) was found to be associated with an increased risk of various malignancies. Biochemical and biological differences between the 2 polymorphic variants of wild-type P53 might lead to distinct susceptibility to HPV- and non-HPV-induced tumors. For prostate cancer, only limited data are available, especially in the Caucasian population. Therefore, we determined the distribution of the Arg72Pro SNP in a Caucasian case-control study including 118 prostate cancer patients and 194 male controls without any malignancy using restriction fragment length polymorphism analysis. A subset of 33 tumors was tested for HPV infection, and no HPV DNA was found. Cases and controls showed similar distributions of alleles in the SNP (p = 0.720). Regarding the onset of the disease, patients diagnosed at ≤60 years of age and older patients (>60 years of age) showed a significant difference in genotype distribution (p = 0.035); there was also an increased occurrence of risk allele Pro72 in cases aged ≤60 years (p = 0.045). A subset of 64 prostate tumors was stained immunohistochemically for P53. 5 of 64 prostate tumors (7.8%) were positive for P53 expression, indicating integrity of the protein in the majority of cases. Genotype distribution showed no association with the Gleason score or additional histopathological characteristics. This study shows that the overall risk of prostate cancer was not associated with Arg72Pro SNP and HPV infection in our cohort. However, disease onset might be modulated by the p53 Pro72 allele, suggesting an important role of apoptosis regulation in prostate carcinogenesis.

OTX1 expression in breast cancer is regulated by p53

The p53 transcription factor has a critical role in cell stress response and in tumor suppression. Wild-type p53 protein is a growth modulator and its inactivation is a critical event in malignant transformation. It has been recently demonstrated that wild-type p53 has developmental and differentiation functions. Indeed an over-expression of p53 in tumor cells induces asymmetrical division avoiding self-renewal of cancer stem cells (CSCs) and instead promoting their differentiation. In this study, 28 human breast carcinomas have been analyzed for expression of wild-type p53 and of a pool of non-clustered homeobox genes. We demonstrated that orthodenticle homolog 1 gene (OTX1) is transcribed in breast cancer. We established that the p53 protein directly induces OTX1 expression by acting on its promoter. OTX1 has been described as a critical molecule for axon refinement in the developing cerebral cortex of mice, and its activity in breast cancer suggests a synergistic function with p53 in CSC differentiation. Wild-type p53 may regulate cellular differentiation by an alternative pathway controlling OTX1 signaling only in breast cancer cells and not in physiological conditions.

Association of the germline TP53 R72P and MDM2 SNP309 variants with breast cancer survival in specific breast tumor subgroups

The tumor suppressor gene TP53 and its regulator MDM2 are both important players in the DNA-damage repair "TP53 response pathway". Common germline polymorphisms in these genes may affect outcome in patients with tumors characterized by additional somatic changes in the same or a related pathway. To evaluate this hypothesis, we determined the effect of the common germline TP53 R72P and MDM2 SNP309 polymorphisms on breast cancer survival in a consecutive cohort of breast cancer patients (age at diagnosis <53 years, n = 295) with gene expression data available. Patients were classified in subgroups according to their tumor TP53 mutation status and three gene expression profiles; a TP53 mutation status expression signature, a PTEN/PI3K pathway signature and the 70-gene prognosis profile. Survival analyses were performed using Cox regression models adjusting for clinico-pathological characteristics and treatment. An increase in breast cancer-specific mortality was observed for carriers of the germline MDM2 SNP309 rare GG-genotype (range hazard ratios: 2-3) or TP53 R72P heterozygous GC-genotype (range hazard ratios: 1-2) compared to those having the common genotypes within subgroups of tumors displaying a "more aggressive phenotype" gene expression profile. There was no evidence of such an effect on survival within the TP53-mutated tumor group for TP53 R72P carriers but a suggestion of an effect for MDM2 SNP309 carriers (GG vs. TT-genotype HR 2.99, P = 0.06). These results indicate that common polymorphisms in specific pathways may add to the worse prognosis of patients with tumors in which these pathways are affected by somatic alterations.

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.

Toward a pathway-centered approach for the treatment of adrenocortical carcinoma

PURPOSE OF REVIEW

Adrenocortical carcinoma is an aggressive, lethal malignancy of the adrenal cortex. The rarity of the disease has stymied therapeutic development. Recent work toward understanding the molecular pathogenesis of the disease has identified several potential new diagnostic and therapeutic targets.

RECENT FINDINGS

The molecular characterization of adrenocortical carcinoma has identified dysregulation of the Gap 2/mitosis transition and the insulin-like growth factor 1 receptor signaling cascade as two major pathways for therapeutic development. These studies have also highlighted an unappreciated heterogeneity of the disease at the gene level that nevertheless seems to converge onto common cellular pathways. Additionally, the characterization of Wnt signaling through β-catenin in adrenal development, the demonstration of the involvement of BMP signaling in adrenocortical carcinoma growth regulation, and the discovery that ERCC1 expression levels can predict therapeutic response to platinum are just a few of the recent advances that promise to shed light on adrenocortical carcinoma biology.

SUMMARY

Short-term, therapeutic development should target the Gap 2/mitosis transition and the downstream signaling of the insulin-like growth factor 1 receptor receptor. Long-term, additional characterization of patient samples, particularly at the sequence level, is required to fully understand adrenocortical carcinoma biology and apply that knowledge to clinical practice.

A novel oncoprotein Pirh2: rising from the shadow of MDM2

Pirh2 (p53-induced RING-H2) is an E3 ubiquitin ligase that can target p53 for degradation and thereby repress a diverse group of biological activities regulated by p53. Notably, Pirh2, rather than MDM2, is the primary degrader of active p53 under conditions of DNA damage. Moreover, Pirh2 is highly expressed in multiple cancer cell lines regardless of p53 status. Recent research has shown that Pirh2 is involved in many signalling pathways related to the genesis and evolution of cancer. This review aims to summarize a comprehensive picture of the role of Pirh2 in cellular processes and its significance to tumorigenesis. Furthermore, this review focuses on its potential role as a cancer therapeutic target.