Characterization of the human p53 gene

DNA nanotechnology-based strategies for gastric cancer diagnosis and therapy

Gastric cancer (GC) is a formidable adversary in the field of oncology. The low early diagnosis rate of GC results in a low overall survival rate. Therefore, early accurate diagnosis and effective treatment are the key to reduce the mortality of GC. With the advent of nanotechnology, researchers continue to explore new possibilities for accurate diagnosis and effective treatment. One such breakthrough is the application of DNA nanotechnology. In this paper, the application of exciting DNA nanomaterials in the diagnosis and treatment of GC is discussed in depth. Firstly, the biomarkers related to GC and the diagnostic strategies related to DNA nanotechnology are summarized. Second, the latest research progress of DNA nanomaterials in the GC targeted therapy are summarized. Finally, the challenges and opportunities of DNA nanomaterials in the research and clinical application of GC are prospected.

TP53 in Myelodysplastic Syndromes

Simple Summary

The importance of gene variants in the prognosis of myelodysplastic syndromes (MDSs) has been repeatedly reported in recent years. Especially, TP53 mutations are independently associated with a higher risk category, resistance to conventional therapies, rapid transformation to leukemia, and a poor outcome. In the review, we discuss the features of monoallelic and biallelic TP53 mutations within MDS, the carcinogenic mechanisms, and the predictive value of TP53 variants in current standard treatments including hypomethylating agents, allogeneic hematopoietic stem cell transplantation, and lenalidomide, as well as the latest progress in TP53-targeted therapy strategies in MDS.

Abstract

Myelodysplastic syndromes (MDSs) are heterogeneous for their morphology, clinical characteristics, survival of patients, and evolution to acute myeloid leukemia. Different prognostic scoring systems including the International Prognostic Scoring System (IPSS), the Revised IPSS, the WHO Typed Prognostic Scoring System, and the Lower-Risk Prognostic Scoring System have been introduced for categorizing the highly variable clinical outcomes. However, not considered by current MDS prognosis classification systems, gene variants have been identified for their contribution to the clinical heterogeneity of the disease and their impact on the prognosis. Notably, TP53 mutation is independently associated with a higher risk category, resistance to conventional therapies, rapid transformation to leukemia, and a poor outcome. Herein, we discuss the features of monoallelic and biallelic TP53 mutations within MDS, their corresponding carcinogenic mechanisms, their predictive value in current standard treatments including hypomethylating agents, allogeneic hematopoietic stem cell transplantation, and lenalidomide, together with the latest progress in TP53-targeted therapy strategies, especially MDS clinical trial data.

Mechanisms of TP53 Pathway Inactivation in Embryonic and Somatic Cells-Relevance for Understanding (Germ Cell) Tumorigenesis

The P53 pathway is the most important cellular pathway to maintain genomic and cellular integrity, both in embryonic and non-embryonic cells. Stress signals induce its activation, initiating autophagy or cell cycle arrest to enable DNA repair. The persistence of these signals causes either senescence or apoptosis. Over 50% of all solid tumors harbor mutations in TP53 that inactivate the pathway. The remaining cancers are suggested to harbor mutations in genes that regulate the P53 pathway such as its inhibitors Mouse Double Minute 2 and 4 (MDM2 and MDM4, respectively). Many reviews have already been dedicated to P53, MDM2, and MDM4, while this review additionally focuses on the other factors that can deregulate P53 signaling. We discuss that P14^ARF (ARF) functions as a negative regulator of MDM2, explaining the frequent loss of ARF detected in cancers. The long non-coding RNA Antisense Non-coding RNA in the INK4 Locus (ANRIL) is encoded on the same locus as ARF, inhibiting ARF expression, thus contributing to the process of tumorigenesis. Mutations in tripartite motif (TRIM) proteins deregulate P53 signaling through their ubiquitin ligase activity. Several microRNAs (miRNAs) inactivate the P53 pathway through inhibition of translation. CCCTC-binding factor (CTCF) maintains an open chromatin structure at the TP53 locus, explaining its inactivation of CTCF during tumorigenesis. P21, a downstream effector of P53, has been found to be deregulated in different tumor types. This review provides a comprehensive overview of these factors that are known to deregulate the P53 pathway in both somatic and embryonic cells, as well as their malignant counterparts (i.e., somatic and germ cell tumors). It provides insights into which aspects still need to be unraveled to grasp their contribution to tumorigenesis, putatively leading to novel targets for effective cancer therapies.

Association of PIN3 16-bp duplication polymorphism of TP53 with breast cancer risk in Mali and a meta-analysis

Background

Breast cancer, the most common tumor in women in Mali and worldwide has been linked to several risk factors, including genetic factors, such as the PIN3 16-bp duplication polymorphism of TP53. The aim of our study was to evaluate the role of the PIN3 16-bp duplication polymorphism in the susceptibility to breast cancer in the Malian population and to perform a meta-analysis to better understand the correlation with data from other populations.

Methods

We analyzed the PIN3 16-bp duplication polymorphism in blood samples of 60 Malian women with breast cancer and 60 healthy Malian women using PCR. In addition, we performed a meta-analysis of case-control study data from international databases, including Pubmed, Harvard University Library, Genetics Medical Literature Database, Genesis Library and Web of Science. Overall, odds ratio (OR) with 95% CI from fixed and random effects models were determined. Inconsistency was used to assess heterogeneity between studies and publication bias was estimated using the funnel plot.

Results

In the studied Malian patients, a significant association of PIN3 16-bp duplication polymorphism with breast cancer risk was observed in dominant (A1A2 + A2A2 vs. A1A1: OR = 2.26, CI 95% = 1.08–4.73; P = 0.02) and additive (A2 vs. A1: OR = 1.87, CI 95% = 1.05–3.33; P = 0.03) models, but not in the recessive model (P = 0.38). In the meta-analysis, nineteen (19) articles were included with a total of 6018 disease cases and 4456 controls. Except for the dominant model (P = 0.15), an increased risk of breast cancer was detected with the recessive (OR = 1.46, 95% CI = 1.15–1.85; P = 0.002) and additive (OR = 1.11, 95% CI = 1.02–1.19; P = 0.01) models.

Conclusion

The case-control study showed that PIN3 16-bp duplication polymorphism of TP53 is a significant risk factor for breast cancer in Malian women. These findings are supported by data from the meta-analysis carried out on different ethnic groups around the world.

Molecular cloning, characterization and expression analysis of p53 from turbot Scophthalmus maximus and its response to thermal stress

The tumor suppressor protein, p53 plays a crucial role in protecting genetic integrity. Once activated by diverse cell stresses, p53 reversibly activates downstream target genes to regulate cell cycle and apoptosis. However, few studies have investigated the effects of thermal stress in turbot, specifically the p53 signaling pathway. In this study, the rapid amplification of cDNA ends was used to obtain a full-length cDNA of the turbot p53 gene (Sm-p53) and perform bioinformatics analysis. The results showed that the cDNA of the Sm-p53 gene was 2928 bp in length, encoded a 381 amino acid protein, with a theoretical isoelectric point of 6.73. It was composed of a DNA binding and a tetramerization domain. Expression of Sm-p53 in different tissues was detected and quantified by qRT-PCR, and was highest in the liver. We also investigated the expression profiles of Sm-p53 in different tissue and TK cells after thermal stress. These result suggested that Sm-p53 plays a key role, and provides a theoretical basis for Sm-p53 changes in environmental stress responses in the turbot.

Translational Control in p53 Expression: The Role of 5'-Terminal Region of p53 mRNA

In this review, the latest research concerning the structure and function of the 5'-terminal region of p53 mRNA was discussed. Special attention was focused on defined structural motifs which are present in this region, as well as their conservation and plausible functional role in translation. It is known that the length of the 5'-terminal region and the structural environment of initiation codons can strongly modulate translation initiation. The ability of this region of p53 mRNA to bind protein factors was also described with special emphasis on general principles that govern, such RNA-protein interactions. The structural alterations within the 5'-terminal region of p53 mRNA and proteins that bind to this region have a strong impact on the rate of mRNA scanning and on translation efficiency in in vitro assays, in selected cell lines, and under stress conditions. Thus, the structural features of the 5'-terminal region of p53 mRNA seem to be very important for translation and for translation regulation mechanisms. Finally, we suggested topics that, in our opinion, should be further explored for better understanding of the mechanisms of the p53 gene expression regulation at the translational level.

Insights into the molecular features of the von Hippel-Lindau-like protein

We present an in silico characterization of the von Hippel-Lindau-like protein (VLP), the only known human paralog of the von Hippel-Lindau tumor suppressor protein (pVHL). Phylogenetic investigation showed VLP to be mostly conserved in upper mammals and specifically expressed in brain and testis. Structural analysis and molecular dynamics simulations show VLP to be very similar to pVHL three-dimensional organization and binding dynamics. In particular, conservation of elements at the protein interfaces suggests VLP to be a functional pVHL homolog potentially possessing multiple functions beyond HIF-1α-dependent binding activity. Our findings show that VLP may share at least seven interactors with pVHL, suggesting novel functional roles for this understudied human protein. These may occur at precise hypoxia levels where functional overlap with pVHL may permit a finer modulation of pVHL functions.

The human amniotic fluid mesenchymal stem cells therapy on, SKOV3, ovarian cancer cell line

Purpose

One of the most common malignancies peculiar to female health with few symptoms, low response to therapy, difficult diagnosis, frequent relapse, and high mortality, is ovarian cancer. Thus, our experiment, using Human amniotic fluid mesenchymal stem cells (hAFMSCs) as a therapeutic tool, aims to find an efficient treatment approach for patients suffering from SKOV3 ovarian cancer.

Material & Methods

In this study, we obtained 5 ml amniotic fluid from 16–20 week pregnant women who underwent amniocentesis for routine prenatal diagnosis by karyotyping in Al‐Zahra Hospital of Tabriz University of Medical Sciences, Iran. Using trans wells in 24 wells plate, hAFMSCs were isolated from all samples, co‐cultured with SKOV3 ovarian cancer cell line, and characterized via flow cytometry and RT‐PCR. Human skin fibroblast cells (HSFCs) were isolated and used as a negative control. SKOV3 and HSFCs' viability after 5 days was evaluated by MTT assay. Cell cycle and apoptotic genes were analyzed by real‐time PCR.

Results

We successfully isolated and characterized hAFMSCs through it positivity for CD44 and CD90 specific mesenchymal stem cell markers and negativity for CD31 and CD45. Oct4 and NANOG were evaluated by RT‐PCR as pluripotency markers, and visualized on 2% gel electrophoresis. We established hAFMS cell lines after 5 days of co‐culturing the SKOV3 cells, viability was decreased; however, HSFCs did not show toxicity by MTT assay. The genes indicated upregulation and high expression by a real‐time PCR.

Conclusions

Our findings showed that hAFMSCs have natural tumor tropism, and can release soluble factors in a cell culture, which cause an efficient anticancer effect. Thus, we can use hAFMSCs for complete anticancer therapy on SKOV3 cell line at cell culture condition and possibly in vivo in the near future.

Nasopharyngeal carcinoma: understanding its molecular biology at a fine scale

Among all cancers, the incidence of nasopharyngeal carcinoma (NPC) is quite high in the endemic regions. NPC is a head and neck cancer with poor survival rate, and is rare throughout most of the world but common in certain geographic areas, like southern Asia and some regions of North East India (Nagaland, Manipur, and Mizoram). A clear understanding of its etiology is still lacking, but NPC is widely suspected to be the result of both genetic susceptibility and exposure to environmental factors or Epstein-Barr virus infection. Diagnosis in the early stages needs a high index of clinical acumen, and, although most cross-sectional imaging investigations show the tumor with precision, confirmation is dependent on histology. This article reviews all related research reports on NPC histopathological classifications worldwide that have been published within the past 20 years. Genome-wide association studies suggested that there might be common disease mechanisms between that disease and NPC. Personalized management rules, quality assessment of life in patients, and an understanding of the essential mechanisms of recurrence could be directed toward research into recurrent NPC. Hence, this literature would offer otolaryngologists a deeper insight into the etiological and management aspects of NPC.

Lack of Prognostic Value of p53 Protein Expression in Node-Negative Breast Cancer

Aims and background

The association of p53 protein accumulation and prognosis in node-negative breast cancer patients has been alternately demonstrated and denied in literature reports, and opinions on the use of p53 expression as an indicator of high risk of recurrence and as a guide for adjuvant therapy are controversial.

Study design

The association of p53 protein accumulation with prognosis was retrospectively evaluated in a series of 221 node-negative breast cancer patients treated with surgery alone and followed up for a minimum of 10 years. p53 accumulation was determined by immunohistochemistry on archive material, and classified into four grades of increasing immunostaining.

Results

No association was observed between p53 and age or pT category, whereas a significant association with nuclear grade was found (P = 0.0014). Univariate and multivariate analysis of 10-yr disease-free and overall survival showed a significant and independent prognostic association for tumor size (pT category) and nuclear grading but not for p53 expression, whatever grade grouping was used.

Conclusions

We did not find any evidence supporting the use of p53 immunostaining in current practice as an independent prognostic indicator or as a discriminant factor for adjuvant treatment of node-negative breast cancer patients.

Mutation spectrum of TP53 gene predicts clinicopathological features and survival of gastric cancer

Background and aim

TP53 gene is frequently mutated in gastric cancer (GC), but the relationship with clinicopathological features and prognosis is conflicting. Here, we screened TP53 mutation spectrum of 214 GC patients in relation to their clinicopathological features and prognosis.

Results

TP53 nonsilent mutations were detected in 80 cases (37.4%), being frequently occurred as C:G to T:A single nucleotide transitions at 5′-CpG-3′ sites. TP53 mutations occurred more frequently in differentiated histologic type than in undifferentiated type in the early stage (48.6% vs. 7%, P=0.0006), while the mutations correlated with venous invasion among advanced stage (47.7% vs. 20.7%, P=0.04). Subset of GC with TP53 hot spot mutations (R175, G245, R248, R273, R282) presented significantly worse overall survival and recurrence free survival compared to others (both P=0.001).

Methods

Matched biopsies from GC and adjacent tissues from 214 patients were used for the experiment. All coding regions of TP53 gene (exon2 to exon11) were examined using Sanger sequencing.

Conclusion

Our data suggest that GC with TP53 mutations seems to develop as differentiated histologic type and show aggressive biological behavior such as venous invasion. Moreover, our data emphasizes the importance of discriminating TP53 hot spot mutations (R175, G245, R248, R273, R282) to predict worse overall survival and recurrence free survival of GC patients.

Mandarin fish p53: Genomic structure, alternatively spliced variant and its mRNA expression after virus challenge

A number of size variants of the p53 protein have been described in mammal, but little is known about alternative splicing of p53 expression and function in the fish. In our previous study, the immune defense and antiviral responses of p53 had been determined in mandarin fish (Siniperca chuatsi). However, the role of its splicing variants remains unknown. In the present study, the organization of mandarin fish p53 (Sc-p53) genome sequence was determined and a novel splice variant was characterized. The Sc-p53 genomic sequence was composed of 5543 bp, containing 11 exons and 10 introns, which was similar to other species. Then, a 1106 bp full-length cDNA of a novel splice variant p53 from mandarin fish (designed as Sc-p53I6) was cloned and characterized. Quantitative real-time PCR assays revealed that Sc-p53I6 was expressed in all tissues examined, and it was most abundant in the gill, hemocyte and hind kidney. Western blotting analysis revealed that Sc-p53I6 protein was abundant in liver, trunk kidney, hind kidney, stomach and heart. In addition, the regulation of Sc-p53I6 gene expression after virus infection was determined and characterized. The results showed twice rise expression pattern of Sc-p53I6 in CPB cells and spleen of mandarin fish in response to infectious kidney and spleen necrosis virus (ISKNV). However, a different expression pattern, once rise, of Sc-p53I6 in response to Siniperca chuatsi rhabdovirus (SCRV) infection was found. The mRNA expression of Sc-p53I6 was significantly up-regulated in CPB at 4 h and spleen of mandarin fish at 12 h post-infection. These results will shed a new light on antiviral response mechanisms of p53 in mandarin fish.

Significant Prognostic Features and Patterns of Somatic TP53 Mutations in Human Cancers

TP53 is the most frequently altered gene in human cancers. Numerous retrospective studies have related its mutation and abnormal p53 protein expression to poor patient survival. Nonetheless, the clinical significance of TP53 (p53) status has been a controversial issue. In this work, we aimed to characterize TP53 somatic mutations in tumor cells across multiple cancer types, primarily focusing on several less investigated features of the mutation spectra, and determine their prognostic implications. We performed an integrative study on the clinically annotated genomic data released by The Cancer Genome Atlas. Standard statistical methods, such as the Cox proportional hazards model and logistic regression, were used. This study resulted in several novel findings. They include the following: (1) similar to previously reported cases in breast cancer, the mutations in exons 1 to 4 of TP53 were more lethal than those in exons 5 to 9 for the patients with lung adenocarcinomas; (2) TP53 mutants tended to be negatively selected in mammalian evolution, but the evolutionary conservation had various clinical implications for different cancers; (3) conserved correlation patterns (ie, consistent co-occurrence or consistent mutual exclusivity) between TP53 mutations and the alterations in several other cancer genes (ie, PIK3CA, PTEN, KRAS, APC, CDKN2A, and ATM) were present in several cancers in which prognosis was associated with TP53 status and/or the mutational characteristics; (4) among TP53-mutated tumors, the total mutation burden in other driver genes was a predictive signature (P < .05, false discovery rate <0.11) for better patient survival outcome in several cancer types, including glioblastoma multiforme. Among these findings, the fourth is of special significance as it suggested the potential existence of epistatic interaction effects among the mutations in different cancer driver genes on clinical outcomes.

p53 in Low-grade Gliomas

Although the p53 tumor suppressor gene is well known to be involved in the pathogen esis of malignant astrocytomas, its significance in the development of low-grade glio mas, including the nonastrocytic tumors, remains underexplored. In an attempt to further understanding the molecular genetics of glial tumorigenesis, 37 low-grade gliomas of different histologic subtypes were screened for p53 mutations with the polymerase chain reaction, single-strand conformation polymorphism analysis and direct DNA sequencing. Forty-eight tumors, including the previously mentioned 37 cases, were examined immunohistochemically with paraffin-embedded tissues for p53 protein labeling. Only two diffuse astrocytomas exhibited p53 genetic abnormalities, and both tumors behaved aggressively. Two tumors exhibited p53 protein immuno labeling, including one of the cases with genetic changes. p53 genetic alterations are only rarely involved in the pathogenesis of low-grade gliomas. The authors speculate that they occur late in the transition from low-grade to high-grade tumors. Int J Surg Pathol 1 (3):163-170, 1994

p53 and Breast Cancer

Inactivation of the p53 tumor suppressor gene is one of the commonest genetic changes identified in human breast cancer. In this review, the structure and function of the p53 gene and its protein products will be discussed, with particular reference to p53 alterations that contribute to carcinogenesis. The frequency and pattern of p53 alterations in breast cancer will be outlined, laboratory methods for their detection briefly summarized, and the potential use of p53 as a prognostic and predictive marker discussed.

Review : p53 in the pathogenesis, diagnosis, and treatment of cancer

Objective. The cellular functions of p53, the conse quences of the loss of p53 function, and the potential impact of p53 in oncology are reviewed within the framework of an overview of the molecular basis of cancer and cell cycle control.

Data Sources. A MEDLINE search of articles from 1976 to the present was conducted using the terms p53 protein and p53 gene. The search was restricted to the English language. Oncology and molecular biology textbooks were used as additional references.

Data Extraction. We reviewed the literature to discuss the cellular function of p53, the mechanisms of p53 inactivation, the cellular consequences of the loss of p53 function, the role of p53 loss in tumori genesis, and the potential applications of this knowl edge.

Data Synthesis. p53 mutations are found in ~ 50% of human cancers. Knowledge of p53 functions and defects provides the basis for potential applica tions in the areas of cancer epidemiology, cancer diagnosis, and determination of prognosis. An under standing of the functions and defects of p53 also presents a host of opportunities for the design of novel cancer therapies. Therapeutic approaches be ing studied include the restoration of p53 by gene therapy, the alteration of mutant p53 expression by antisense therapy, and the use of p53 mutations as a target for directing therapy to cancer cells; some of these approaches are already under phase I investiga tion. As knowledge of p53 unfolds, additional thera peutic approaches will certainly be developed. The story of p53 illustrates that the manipulation of mo lecular interactions is a new frontier in therapeutics and offers an additional role for oncology pharmacy specialists.

TP53 polymorphisms in sporadic North Indian breast cancer patients

BACKGROUND

The purpose of this study was to evaluate the potential association of five (p.P47S, p.R72P, PIN3 Ins16bp, p.R213R and r.13494g>a) polymorphisms of TP53 with the risk of developing breast cancer in North Indian Punjabi population.

METHODS

We screened DNA samples of 200 sporadic breast cancer patients (197 females and 3 males) and 200 unrelated healthy, gender and age matched individuals for the polymorphisms.

RESULTS

For the p.P47S polymorphism, we observed the PP genotype in 99.5% of the patients and PS genotype in only 1 patient. All the controls had the wild type PP genotype. The frequency of RR, RP and PP genotype of p.R72P was 23.5% vs 33.5%, 51.5% vs 45.5% and 25% vs 21% in patients and controls respectively. Heterozygous (RP) genotype was increased in breast cancer patients as compared to controls (51.5 vs 45.5%) and showed 1.61 fold significantly increased risk for breast cancer (OR=1.61, 95% CI, 1.01-2.58, p=0.04). In breast cancer patients the frequencies of A1A1, A1A2 and A2A2 genotypes of PIN3 Ins16bp polymorphism were 67%, 26% and 7% respectively whereas in controls the genotype frequencies were 68.5%, 27.5% and 4% respectively, with no significant difference. For p.R213R (c.639A>G), all individuals had homozygous wild type genotype. The frequencies of GG, GA and AA genotypes of TP53 r.13494g>a polymorphism were 62 vs 67.5%, 33 vs 28% and 5 vs 4.5% in patients and controls respectively, again without significant difference. We observed that RP- A1A1 genotype combination of p.R72P and PIN3 Ins16bp and RP-GG combination of p.R72P and r.13494g>a polymorphism showed significant risk of breast cancer (OR=1.65, 95%CI: 0.98-2.78, p=0.05; OR=1.72, 95%CI: 1.01-2.92, p=0.04).

CONCLUSION

The results of present study indicated that among the five TP53 polymorphisms investigated, the p.R72P polymorphism, and the RP-A1A1 and RP-GG genotype combination contribute to breast cancer susceptibility in North Indians.

DNA methylation analysis of cancer-related genes in oral epithelial cells of healthy smokers

AIM

The aim of this study was to investigate the smoking habit influence on DNA methylation status in the promoters of the cancer related-genes MLH1, hTERT and TP53 in oral epithelial cells of healthy subjects.

MATERIALS AND METHODS

DNA methylation analysis was performed using methylation-sensitive restriction enzymes (MSRE) in oral epithelial cells from non-smokers, smokers and ex-smokers.

RESULTS

The investigated CpG dinucleotides located at HhaI and HpaII sites in the MLH1 gene promoter were observed to be fully methylated in the majority of DNA samples from the smoker group and statistical differences were found between non-smokers and smokers and between smokers and ex-smokers (p<0.05). The same was observed in the hTERT gene promoter at HhaI sites (p<0.05) and for HpaII sites the unmethylated condition was more frequent in smokers in comparison to non-smokers (p<0.05). For TP53, no differences were found among groups (p>0.05), with the fully methylated condition found to be a common event in healthy oral epithelial cells.

CONCLUSION

We conclude that smoking may induce changes in DNA methylation status in cancer-related genes of oral epithelial cells and that the cessation of smoking is capable of reversing this process. Based on our data, we suggest that DNA methylation status of the hTERT and MLH1 gene promoters are promising markers for screening a set of smoking-related alterations in oral cells.

The base discriminating potential of pyrrolidinyl PNA demonstrated by magnetic Fe(x)O(y) particles

Pyrrolidinyl PNA was immobilized on Fe(x)O(y) magnetic particles and was able to capture and thereby discriminate single base alterations in DNA counterstrands better than DNA. The selectivities of matched vs. mismatched oligonucleotides measured by the absorption differences were up to 10-12 which are remarkable values for linear probes.

Relationship between p53 status and response to chemotherapy in patients with gastric cancer: a meta-analysis

BACKGROUND

Previous studies have yielded conflicting results regarding the relationship between p53 status and response to chemotherapy in patients with gastric cancer. We therefore performed a meta-analysis to expound the relationship between p53 status and response to chemotherapy.

METHODS/FINDINGS

Thirteen previously published eligible studies, including 564 cases, were identified and included in this meta-analysis. p53 positive status (high expression of p53 protein and/or a mutant p53 gene) was associated with improved response in gastric cancer patients who received chemotherapy (good response: risk ratio [RR] = 0.704; 95% confidence intervals [CI] = 0.550-0.903; P = 0.006). In further stratified analyses, association with a good response remained in the East Asian population (RR = 0.657; 95% CI = 0.488-0.884; P = 0.005), while in the European subgroup, patients with p53 positive status tended to have a good response to chemotherapy, although this did not reach statistical significance (RR = 0.828, 95% CI = 0.525-1.305; P = 0.417). As five studies used neoadjuvant chemotherapy (NCT) and one used neoadjuvant chemoradiotherapy (NCRT), we also analyzed these data, and found that p53 positive status was associated with a good response in gastric cancer patients who received chemotherapy-based neoadjuvant treatment (RR = 0.675, 95% CI = 0.463-0.985; P = 0.042).

CONCLUSION

This meta-analysis indicated that p53 status may be a useful predictive biomarker for response to chemotherapy in gastric cancer. Further prospective studies with larger sample sizes and better study designs are required to confirm our findings.

Expression of β-catenin and cyclin D1 in Merkel cell carcinomas of the head and neck

BACKGROUND

Merkel cell carcinomas (MCC) are very aggressive tumors of the sun-exposed skin with a high potential to metastasize. Little is known about the genesis of MCC and very few prognostic markers have been detected so far. The Wnt pathway protein β-catenin and the cell cycle protein cyclin D1 are two promotors of tumor growth and are expressed in a variety of malignant neoplasms such as lymphomas, thyroid, breast cancer, and many others.

PATIENTS AND METHODS

Tissue samples of 27 patients with MCC were immunohistochemically stained for β-catenin and cyclin D1 and correlated with overall survival of patients. In addition, western blot analysis was carried out in the two MCC cell lines MCC-13 and MCC-26.

RESULTS

β-catenin showed a cytoplasmatic expression of 10-30 % in 11 samples and an expression lower than 10 % in eight samples. Nuclear staining was visible in two samples. None of the 27 samples expressed cyclin D1.

CONCLUSION

Neither cyclin D1 nor β-catenin was expressed in a statistically significant manner, concluding that the development of MCCs is independent of β-catenin and cyclin D1 expression and these proteins are not suitable as prognostic markers. We could describe the expression pattern of cyclin D1 for the first time.

TP53 intronic mutations in bovine enzootic hematuria-associated urinary bladder tumors

Tumor protein 53 (TP53) is a tumor suppressor gene that is frequently mutated in urinary bladder tumors in both humans and animals. In cattle, urinary bladder tumors have been reported as occurring spontaneously as well as in conjunction with bracken fern consumption-induced bovine enzootic hematuria (BEH). The goal of this study was to evaluate various types of bovine urinary bladder neoplasms for the presence of TP53 alterations, using the polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) method. DNA was extracted from both epithelial and mesenchymal urinary bladder tumor samples in cattle, associated with the chronic consumption of bracken fern. PCR was performed using primers targeted to exons 5 to 8, following electrophoresis and isolation, and the products were assessed by SSCP. Tumors in which alterations in the electrophoresis patterns were noted included hemangiomas, papillomas, and carcinomas in situ. Exemplars of these tumor types were selected for sequencing, and although no changes were noted in the 5 to 8 exon range, on either side of the designed primers for exon 6, there was some portion of intron 6 in which sequencing demonstrated a deletion of the thyamine nucleotide at position 9332. In summary, although mutations were not observed within exons 5 to 8, this represents the first report of an intronic mutation in the TP53 gene in association with bovine urinary bladder tumors. Mutations within introns can predispose tissues to the development of cancer, and therefore, a possible association between mutations of the introns of TP53 and the development of urinary bladder tumors in cattle with BEH should be further investigated.

Blinded study determination of high sensitivity and specificity microchip electrophoresis-SSCP/HA to detect mutations in the p53 gene

Knowledge of the genetic changes that lead to disease has grown and continues to grow at a rapid pace. However, there is a need for clinical devices that can be used routinely to translate this knowledge into the treatment of patients. Use in a clinical setting requires high sensitivity and specificity (>97%) in order to prevent misdiagnoses. Single-strand conformational polymorphism (SSCP) and heteroduplex analysis (HA) are two DNA-based, complementary methods for mutation detection that are inexpensive and relatively easy to implement. However, both methods are most commonly detected by slab gel electrophoresis, which can be labor-intensive, time-consuming, and often the methods are unable to produce high sensitivity and specificity without the use of multiple analysis conditions. Here, we demonstrate the first blinded study using microchip electrophoresis (ME)-SSCP/HA. We demonstrate the ability of ME-SSCP/HA to detect with 98% sensitivity and specificity >100 samples from the p53 gene exons 5-9 in a blinded study in an analysis time of <10 min.

The repair of melphalan-induced DNA adducts in the transcribed strand of active genes is subject to a strong polarity effect

To investigate the mechanisms of the therapeutic action and drug resistance to the nitrogen mustard melphalan, melphalan-induced DNA damage repair and chromatin structure were examined along the p53, N-ras and d-globin gene loci in cells carrying different repair activities. In nucleotide excision repair-deficient XP-A cells, similar levels of adducts were found in all fragments examined, indicating uniform distribution of DNA damage. In both, repair-proficient CS-B and XP-C cells, faster repair was observed in regions inside the transcribed N-ras and p53 genes, compared to regions on both sides outside of the genes, while no such difference was observed for the inactive d-globin gene. Moreover, very fast adduct repair on the transcribed strand of the active genes was seen immediately downstream of the transcription start site, together with a steeply decreasing gradient of repair efficiency along the gene towards the 3'-end. In all cells analyzed, the above variation in DNA repair efficiency was paralleled exactly by the variation in the degree of local chromatin condensation, more relaxed chromatin being associated with faster repair. Similar results were obtained using peripheral blood mononuclear cells from healthy volunteers, suggesting that the existence of a repair gradient along transcribed genes may be a universal phenomenon. In conclusion, these findings demonstrate that the repair of melphalan adducts in the transcribed strand of active genes is subject to a strong polarity effect arising from variations in the chromatin structure.

P53 mutation is a rare event in Merkel cell carcinoma of the head and neck

The aim of this retrospective analysis was to evaluate the status of p53 and possible mutations in Merkel cell carcinoma (MCC) cell lines and MCC tissue samples. The p53 mutations are common in different cancer origins but rare in MCCs detected so far. MCCs are highly aggressive neuroendocrine tumors with an enhanced potential to metastasize. Until now, less is known about MCC and new approaches to understand this disease are necessary. RNA and DNA were extracted from two MCC cell lines and 27 archival paraffin-embedded patient samples. After reverse transcription, a real-time PCR and a high-resolution melt analysis were carried out. In both MCC cell lines, we could detect a p53 missense mutation at codon 193 (exon 6) with a change in amino acids (His → Leu). This mutation was equal in both cell lines and was investigated in 27 tissue samples in succession to detect possible accounts for the aggressive behavior of MCCs. Unfortunately, no corresponding p53 mutation could be observed in the investigated tissue samples. A new p53 mutation was detected in MCC cell lines. This mutation could not be determined in patients' samples. Therefore, the aggressiveness of MCC seems to be independent of p53 mutations and other mutations might be responsible for developing MCC.

The Role of Wild-Type p53 in Cisplatin-Induced Chk2 Phosphorylation and the Inhibition of Platinum Resistance with a Chk2 Inhibitor

The major obstacle in platinum chemotherapy is the repair of platinum-damaged DNA that results in increased resistance, reduced apoptosis, and finally treatment failure. Our research goal is to determine and block the mechanisms of platinum resistance. Our recent studies demonstrate that several kinases in the DNA-repair pathway are activated after cells are exposed to cisplatin. These include ATM, p53, and Chk2. The increased Chk2 phosphorylation is modulated by p53 in a wild-type p53 model. Overexpression of p53 by cDNA transfection in wt-p53 (but not p53 deficient) cells doubled the amount of Chk2 phosphorylation 48 hours after cisplatin treatment. p53 knockdown by specific siRNA greatly reduced Chk2 phosphorylation. We conclude that wild-type p53, in response to cisplatin stimulation, plays a role in the upstream regulation of Chk2 phosphorylation at Thr-68. Cells without normal p53 function survive via an alternative pathway in response to the exogenous influence of cisplatin. We strongly suggest that it is very important to include the p53 mutational status in any p53 involved studies due to the functional differentiation of wt p53 and p53 mutant. Inhibition of Chk2 pathway with a Chk2 inhibitor (C3742) increased cisplatin efficacy, especially those with defective p53. Our findings suggest that inhibition of platinum resistance can be achieved with a small-molecule inhibitor of Chk2, thus improving the therapeutic indices for platinum chemotherapy.

Evaluation of the noncovalent binding interactions between polycyclic aromatic hydrocarbon metabolites and human p53 cDNA

The binding of reactive polycyclic aromatic hydrocarbon (PAH) metabolites, formed enzymatically, to DNA is a crucial step in PAH carcinogenesis in vivo. We investigated the noncovalent binding interactions between 11 PAH metabolites and human p53 complementary DNA (p53 cDNA) using the fluorescence displacement method and molecular docking analysis. All of the examined metabolites predominantly interacted with p53 cDNA by intercalation instead of groove binding. The dissociation constants ranged from 0.02 to 12.34μM. Of the metabolites tested, 1-hydroxypyrene and 3-hydroxybenzo[a]pyrene showed the strongest binding affinities to DNA, while 2-naphthol was the weakest DNA intercalator. The intercalation of the metabolites was stabilized by stacking the PAH phenyl rings with the DNA base pairs and the formation of hydrogen bonds between the oxide or hydroxyl groups on the metabolites, and DNA bases or backbones. The binding of the metabolites to DNA showed some sequence selectivity. The binding affinities and hydrogen bonds for 3-hydroxybenzo[a]pyrene, benzo[a]pyrene-4,5-dihydroepoxide (BPE) and benzo[a]pyrene-r-7,t-8-dihydrodiol-t-9,10-epoxide (BPDE) differed. It seems that the functional groups on the periphery of the PAH aromatic ring play crucial roles in regulating its binding affinity with DNA. Although it was difficult to determine the correlation between DNA noncovalent binding affinity and carcinogenicity for some of the PAH metabolites, the present study improved our understanding of the formation of PAH metabolite-DNA adducts.

Current status of biodosimetry based on standard cytogenetic methods

Knowledge about dose levels in radiation protection is an important step for risk assessment. However, in most cases of real or suspected accidental exposures to ionizing radiation (IR), physical dosimetry cannot be performed for retrospective estimates. In such situations, biological dosimetry has been proposed as an alternative for investigation. Briefly, biodosimetry can be defined as individual dose evaluation based on biological endpoints induced by IR (so-called biomarkers). The relationship between biological endpoints and absorbed dose is not always straightforward: nausea, vomiting and diarrhoea, for example, are the most well-known biological effects of individual irradiation, but a precise correlation between those symptoms and absorbed dose is hardly achieved. The scoring of unstable chromosomal-type aberrations (such as dicentrics and rings) and micronuclei in mitogen-stimulated peripheral blood, up till today, has been the most extensively biodosimetry assay employed for such purposes. Dicentric assay is the gold standard in biodosimetry, since its presence is generally considered to be specific to radiation exposure; scoring of micronuclei (a kind of by-product of chromosomal damages) is easier and faster than that of dicentrics for dose assessment. In this context, the aim of this work is to present an overview on biodosimetry based on standard cytogenetic methods, highlighting its advantages and limitations as tool in monitoring of radiation workers' doses or investigation into accidental exposures. Recent advances and perspectives are also briefly presented.

Familial predisposition to adrenocortical tumors: clinical and biological features and management strategies

The incidence of adrenocortical tumors (ACTs) is increased in several familial cancer syndromes resulting from abnormalities in genes that encode transcription factors implicated in cell proliferation, differentiation, senescence, apoptosis, and genomic instability. These include P53, MEN1, APC, and PRKAR1A. Adenomas are the most common ACTs, but adrenocortical carcinomas occur rarely as well. The clinical manifestations of ACTs, which result from increased secretion of adrenocortical hormones, are similar in the familial and sporadic forms of the disease. However, their management may differ because of unique aspects of the constitutional syndromes. The analysis of gene expression profiles of ACTs in these constitutional syndromes have contributed to our understanding of adrenal tumorigenesis and revealed new molecular diagnostic and prognostic markers and candidate genes for targeted therapies. This chapter summarizes the clinical and biological features, pathogenesis, and management strategies for ACTs that develop in patients with familial cancer syndrome.

Transformation of pleomorphic adenoma to carcinoma ex pleomorphic adenoma of the parotid gland is independent of p53 mutations

BACKGROUND AND OBJECTIVES

This retrospective study was performed to evaluate the status of p53 in pleomorphic adenomas and carcinomas ex pleomorphic adenoma in the parotid gland. As loss or mutation of p53 can cause malignant transformation, the possible degeneration of pleomorphic adenomas to carcinomas ex pleomorhic adenoma was investigated by mutational analysis.

METHODS

Twenty-five Patients including 14 patients with pleomorphic adenomas and 11 patients with carcinoma ex pleomorphic adenoma of the parotid gland were examined for p53 status. DNA was extracted out of paraffin-embedded tissue and PCR was performed for the coding exons 2-11. Denaturing gradient gel electrophoresis (DGGE) was carried out for mutational analysis and DNA sequencing was performed in case of a suspected mutation.

RESULTS

Fourteen pleomorphic adenomas and 11 carcinomas ex pleomorphic adenoma were screened for p53 status and potent mutations. Subsequent sequencing of the distinct exons showed no mutation.

CONCLUSION

We could not detect mutations of p53 neither in benign nor malignant parotid tumors and we therefore assume that p53 plays no role in the transformation from pleomorphic adenoma to carcinoma ex pleomorphic adenoma.

The prolyl cis/trans isomerase cyclophilin 18 interacts with the tumor suppressor p53 and modifies its functions in cell cycle regulation and apoptosis

The functional diversity of the tumor suppressor protein p53 is mainly regulated by protein interactions. In this study, we describe a new interaction with the peptidyl-prolyl cis/trans isomerase cyclophilin 18 (Cyp18). The interaction reduced the sequence-specific DNA binding of p53 in vitro, whereas the inhibition of the interaction increased p53-reporter gene activity in vivo. The active site of the folding helper enzyme Cyp18 was directly involved in binding. The proline-rich region (amino acids 64-91) of p53 was most likely responsible for the observed binding because a synthetic peptide comprising amino acids 68-81 of p53 inhibited this interaction, and a p53 variant containing a proline residue at position 72 (p53(P72)) interacted with Cyp18 more effectively than the corresponding p53(R72) variant. Impairment of the Cyp18-p53 interaction induced an accumulation of cells in the G2/M phase of the cell cycle, which was more pronounced when p53(P72) was expressed compared with p53(R72) in an otherwise isogenic cellular background. Moreover, p53-dependent apoptosis was elevated in Cyp18 knockout cells, suggesting an antiapoptotic potential of Cyp18-p53 complexes. Functional in vivo data hint to a possible clinical relevance of the p53-Cyp18 interaction observed.

p53 Mutations in carcinoma of the esophagus and gastroesophageal junction

BACKGROUND

Recent studies suggested p53 mutations as a prognostic factor. Tumors of the esophagus and gastroesophageal (GE) junction show raising incidence with a general poor prognosis.

METHODS

p53 Mutational spectra in 103 patients (68 squamous cell carcinoma/SCC and 35 adenocarcinoma/AC) were compared to clinical and pathologic data.

RESULTS AND CONCLUSIONS

p53 Mutations were found in 26 of 68 SSC (38.2%) and in 12 of 35 AC (34.5%). We only found G > T transversions in smokers with SCC. The survival of patients was not affected by p53 mutational status. In our study, the frequency and mutational spectrum of mutant p53 is similar in both histological types without prognostic relevance.

Ets-1 binds cooperatively to the palindromic Ets-binding sites in the p53 promoter

Due to its autoinhibition for DNA binding, the Ets-1 transcription factor must interact with partners to enhance its affinity for DNA. In a study on the stromelysin-1 promoter, we showed that Ets-1 binds cooperatively to two Ets-binding sites (EBS) organized in palindrome, thereby circumventing the need for a binding partner to counteract autoinhibition. This leads to the formation of an Ets-1-DNA-Ets-1 ternary complex necessary for promoter activation. Here we show that Ets-1 also binds cooperatively to the EBS palindrome of the human p53 promoter, despite the presence of a degenerate EBS to which Ets-1 cannot otherwise bind. Transcriptional transactivation through this palindrome fully correlates to Ets-1 binding. Thus, the cooperative binding model that we initially proposed for the stromelysin-1 promoter may be a general mechanism of Ets-1 binding to palindromic EBS separated by 4bp and a way to counteract binding site degeneracy.

Distribution of p53 expression in tissue from 774 Danish ovarian tumour patients and its prognostic significance in ovarian carcinomas

The clinical roles played by normal and altered p53 in cancer are under intensive investigation, but larger studies describing the pattern as well as the prognostic value are still needed. The aim of this study was, using tissue array (TA), to examine the overexpression of p53 protein in 774 epithelial ovarian tumour tissues from Danish women and to evaluate whether p53 tissue expression levels correlate with clinicopathological parameters and prognosis. The distribution of p53 expression levels at different stages of disease, in different histological subtypes, and the prognostic value of p53 tissue expression were examined. Overall, p53 was expressed in 24/189 (13%) low malignant potential ovarian tumours (LMP) and in 278/585 (48%) ovarian cancers (OC). No significant difference in frequency of p53 tissue expression in LMP tissue was noted with increasing tumour stage (p=0.98). By contrast, there was a significant increase in the frequency of p53 tissue expression in OC with increasing FIGO stage (p<0.00001). Multivariate Cox regression analysis found that less than 20% tissue expression of p53 was associated with longer OC disease-specific survival. Tissue p53 expression may be of prognostic value in women with OC.

Chromosomal aberrations in 17p predict in vitro drug resistance and short overall survival in acute myeloid leukemia

Chromosomal aberrations are important prognostic parameters in acute myeloid leukemia (AML). Indicators of poor prognosis include del(5q)/-5, del(7q)/-7, abnormal 3q or complex karyotype. In recent years, it has become clear that aberrations in 17p represent one of the indicators of poor prognosis in haematological malignancies. In AML, deletions in 17p have been shown to indicate a dismal prognosis; genetic aberrations in 9p have also been discussed as influencing long-term survival in AML. In this study, we correlated genetic abnormalities in chromosomes 9 and 17 in patients with de novo AML to in vitro cytotoxicity of conventional anti-leukemic drugs, and long-term overall survival. Blast cells were isolated from 387 patients diagnosed with AML. Chromosomal analysis was successful in 336 cases. All samples were tested for in vitro cytotoxicity against fludarabine, amsacrine, mitoxantrone, etoposide, daunorubicin and Ara-C after being cultured for 4 days, using an ATP assay. Among the 336 patients, five main groups were identified. Abnormal chromosome 17 (n = 22), abnormal 9p (n = 13), monosomy 7 or deletion 7q (n = 35), complex karyotype (n = 52) and normal karyotype (n = 132). Patients with abnormalities of chromosome 17 showed significantly greater resistance to all drugs tested and significantly shorter overall survival compared with patients with normal and complex karyotypes (p = 0.0001 and 0.041, respectively). All patients with abnormalities of chromosome 17 died within 11 months of diagnosis. A tendency towards shorter overall survival and greater drug resistance was also noted when comparing chromosome 17 abnormalities with del(7q)/-7, but the differences did not reach statistical significance. Patients with abnormal 9p showed significantly shorter overall survival but did not differ significantly as regards in vitro drug resistance compared with patients presenting with a normal karyotype. Chromosomal abnormalities affecting the p53 pathway have a significant impact on cytostatic drug resistance and survival in AML. Developing new drugs targeting the p53 pathway could be a way to improve treatment of AML.

p53 gene expression is modulated by endocrine disrupting chemicals in the hermaphroditic fish, Kryptolebias marmoratus

The full-length of cDNA of tumour suppressor gene p53 from the self-fertilizing fish Kryptolebias marmoratus (Km-p53) was determined using molecular cloning and rapid amplification of cDNA ends (RACE). The Complete cDNA sequences of K. marmoratus (Km-p53) gene was 1.8 kb in length. K. marmoratus p53 amino acid sequence showed a high degree of homology with the sequences from fishes, amphibians, and mammals. Although basal level of expression of Km-p53 mRNA was low, all the studied tissues showed some level of expression. After exposure of K. marmoratus to endocrine disrupting chemicals (EDCs) such as bisphenol A, 4-nonylphenol, and 4-tert-octylphenol, Km-p53 expression was significantly increased within 3 h of exposure in juveniles. However, expression was down-regulated by exposure to most of the EDCs when measured at 96 h in adult fish. In adult fish, suppressive effect of EDCs was more pronounced in liver as compared to other tissues. These findings suggest that Km-p53 gene would be involved in cellular defense mechanism in early stage of exposure to EDCs and long-term exposure may suppress its expression. It may be possible that the suppression of p53 by EDCs may predispose the host to environmental chemical carcinogenesis.

Immunologic markers of cancer progression and prognosis

During the past decade, significant progress has been made in understanding the interactions between the immune system and cancer. The re-emergence of cancer immunosurveillance and immunoediting concepts has provided an understanding of several immunologic markers that are associated with cancer progression and prognosis. Recent studies have attempted to define the critical role of tumor infiltration by lymphocytes as a reflection of a tumor-related immune response. More recently, there has been an improved ability to demonstrate distinct subsets of tumor-infiltrating lymphocytes (TILs) in different tumor compartments. Several of these studies indicate that the presence of TILs may be associated with improved clinical outcome in several human cancers. However, this improved clinical outcome is dependent upon the intratumoral balance and quality of TILs, or infiltration of regulatory T cells or myeloid-derived suppressor cells. Immunologic markers have an important role in demonstrating intermediate end points of a therapeutic intervention and ultimately may be useful in predicting clinical outcomes. These markers are important to the development of successful immunotherapy strategies in cancer.

Prognostic significance of p53 gene mutations and protein overexpression in localized gastrointestinal stromal tumours

AIMS

Mutation of c-kit is a relatively early event in the tumorigenesis of gastrointestinal stromal tumours (GISTs). The aim was to determine the prognostic significance of p53 alterations as an additional genetic change in GISTs.

METHODS AND RESULTS

We reviewed 125 patients with localized GISTs subjected to complete resection between 1990 and 2002. Mutational analyses of c-kit exons 9, 11, 13 and 17, p53 exons 4-8 and immunohistochemistry for p53 protein were conducted using paraffin-embedded tissues. Alterations of p53 were observed in 50 patients (40.0%). Based on the National Institutes of Health's risk category, p53 alterations were noted more frequently in the higher risk categories (P = 0.041). With a median follow-up of 56.5 months (range: 2.3-126.8), 5-year relapse-free survival (RFS) rates were 61.7% without p53 alterations, compared with only 40.2% with p53 alterations (P = 0.009). Multivariate analysis indicated that p53 alterations comprised an independent, poor prognostic factor for RFS, in addition to c-kit mutations, large size, a high mitotic count and non-gastric primary sites.

CONCLUSIONS

Alterations in p53 were more commonly observed in localized GISTs at higher risk of relapse. This suggests that they are significant as an independent, poor prognostic factor.

Mutation of the p53 tumour suppressor gene and overexpression of its protein in 62 Japanese non-Hodgkin's lymphomas

To clarify whether p53 mutation could be involved in the pathogenesis of various subtypes of lymphoma, we investigated 62 Japanese cases of non-Hodgkin's lymphomas (NHLs) for p53 gene mutations and their relationship with the expression of p53 protein. Mutations in exons 5-9 of the p53 gene were screened for using the non-isotopic RNase cleavage assay (NIRCA) and confirmed by direct sequencing, followed by immunohistochemical analysis for p53 protein. Missense and/or nonsense mutations of p53 were detected in 3 (10.7%) of 28 diffuse large B-cell lymphomas (DLBLs) and 2 (15.4%) of 13 T-cell NHLs (15.4%). A single missense mutation at codon 157 (Val to Phe) in exon 5 and at codon 273 (Arg to Pro) in exon 8 was found respectively in 2 DLBLs and in one peripheral T-cell lymphoma (unspecified). In these 3 cases harbouring a missense mutation, overexpression of p53 protein was observed in more than 80% of tumour cells. Double transversion mutations comprising of a missense mutation at codon 167 (Gln to His) in exon 5 and a nonsense mutation at codon 183 (Ser to stop codon) in exon 5 were detected in one DLBL that had apparently transformed from follicular lymphoma and in one advanced adult T-cell lymphoma (ATL). In these two cases harbouring p53 nonsense mutation, no cells positive for p53 protein immunostaining were detected, as well as lymphomas without p53 mutation.

Missense mutation with/without nonsense mutation of the p53 gene is associated with large cell morphology in human malignant lymphoma

Mutations in p53 gene exons 5-9 were studied in 44 non-Hodgkin's lymphomas (NHL) consisting of 35 B-NHL and 9 T-NHL. Missense mutations were found in two diffuse large B-cell lymphomas (DLBL) and one peripheral T-cell lymphoma (unspecified). Double transversion missense and nonsense mutations were detected in one DLBL and one adult T-cell leukemia/lymphoma. Silent mutations were found in two DLBL. Detailed histomorphological study showed that cases harboring p53 missense mutation with/without nonsense mutation tended to have larger nuclei with much more prominent nucleoli. Cytomorphometric analysis was therefore conducted by measuring the gross area of 100 lymphoma cell nuclei in 44 cases and the results were compared between lymphomas harboring p53 missense mutation with/without nonsense mutation and lymphomas harboring p53 silent mutation or lacking mutation. It was found that the lymphomas harboring p53 missense mutation with/without nonsense mutation had a highly significantly larger nuclear gross area than lymphomas with silent p53 mutation or lacking mutation (two-sample t-test, P < 0.00001; Exact Wilcoxon rank-sum test, P < 0.00001). This result suggests that p53 mutation might induce enlargement of neoplastic cell nuclei by some molecular mechanism.

Analysis of p53 protein expression levels on ovarian cancer tissue microarray using automated quantitative analysis elucidates prognostic patient subsets

BACKGROUND

p53 protein is regarded as a valuable prognostic marker in cancer with a potential use as a molecular target. Here, we sought to determine the prognostic value of p53 in ovarian cancer using a novel method of compartmentalized in situ protein analysis.

PATIENTS AND METHODS

A tissue array composed of 141 advanced stage ovarian cancers uniformly treated was constructed. For evaluation of p53 protein expression, we used an immunofluorescence-based method of automated in situ quantitative measurement of protein analysis (AQUA).

RESULTS

High nuclear p53 expression levels were associated with better outcome for overall survival (OS) (P = 0.0023) and disease-free survival (P = 0.0338) at 5-years. High cytoplasmic p53 expression levels were associated with better outcome for OS (P = 0.0002). In multivariable analysis, high nuclear and high cytoplasmic p53 level with International Federation of Gynecology and Obstetrics (FIGO) stage were the most significant predictor variables for OS and high nuclear p53 level with FIGO stage were the significant predictor variables for disease-free survival.

CONCLUSIONS

Assessment of the prognostic value of p53 protein levels using conventional immunohistochemistry is limited by the nonquantitative nature of the method. AQUA provides precise estimation of p53 protein levels and was able to elucidate the association of p53 protein levels and ovarian cancer prognosis.

In vivo expression and antitumor activity of p53 gene transfer with naked plasmid DNA in an ovarian cancer xenograft model in nude mice

INTRODUCTION

Abnormalities in the p53 and p16 tumor suppressor genes are one of the most common occurrences associated with human neoplasia. Consequently, restoration of wild-type p53 or p16 functions is seen as a particularly promising approach for cancer gene therapy. In vitro and in vivo data have demonstrated that virus-mediated p53 gene transfer can induce active cell death and ovarian tumor regression.

AIM

To evaluate the efficiency of intratumoral injection of naked DNA in tumor growth inhibition in an ovarian xenograft model. For that purpose, plasmid vectors encoding wild-type p53 (wt-p53) or p16 alone or in combination were used.

METHODS

Nude mice were injected subcutaneously with the human ovarian adenocarcinoma cell line SKOV3. Three weeks after xenograft, tumor-bearing mice were injected twice a week with plasmid vectors carrying WT-p53 and/or WT-p16 cDNA. Empty plasmids and saline buffer were used as control. Tumor growth was monitored to evaluate the inhibition potential with p53 and/or p16 restoration.

RESULTS

When compared to the control, intratumoral repeated injections of naked plasmid DNA encoding wt-p53 were inhibiting tumor growth. This inhibition was not observed with p16 and no synergy could be obtained between p53 and p16. p53 expression was restored in 84% of mice injected with plasmid encoding wt-p53. p16 expression was restored in 63% of mice injected with plasmid encoding p16.

CONCLUSIONS

In this report we demonstrated that: (i) naked DNA represents an efficient gene transfer in the SKOV3 xenograft model; (ii) restoration of wt-p53 gene allows tumor growth inhibition; and (iii) this inhibition could be correlated with p53 expression as seen in 84% of treated mice after repeated naked DNA injections. These results allow us to envisage naked DNA as a therapeutic adjuvant in ovarian cancer treatment, concomitantly with tumor resection and chemotherapy.

High frequency of TP53 mutations in juvenile pilocytic astrocytomas indicates role of TP53 in the development of these tumors

In adults, the TP53 tumor suppressor gene is frequently mutated in astrocytic brain tumors which is supposed to represent an early event in their development. In juvenile pilocytic and low-grade astrocytomas, however, TP53 mutations have until now been reported as rare, which has led to the suggestion that these tumors may follow a different molecular pathogenesis with an involvement of genes other than TP53. Our analysis of 20 pilocytic and two low-grade astrocytomas of childhood, based on a comprehensive denaturing gradient gel electrophoresis (DGGE) mutation detection assay of the entire coding region, including all splice site junctions of TP53, showed mutations considered as causative in 7 of the 20 (35%) pilocytic astrocytomas and in one of the two low-grade astrocytomas. Our finding is significantly different from the mutation frequency of 1.3% (2/155) previously reported for these tumor types. This may be attributed to the mutation detection system used, which also detects mutations occurring outside the evolutionary conserved region of TP53. Our results suggest that, contrary to the present notion, TP53 mutations may well play a role in the development of juvenile astrocytomas. Furthermore, no mutations were found in tumors of patients with progression of residual tumor after postoperative follow-up. This suggests that TP53 mutations may be associated with less aggressive forms of juvenile astrocytomas, analogous to the situation in adult astrocytomas.

Age dependent phosphorylation and deregulation of p53 in human vestibular schwannomas

Tumor-specific alterations at the p53 gene locus in 30 human vestibular schwannomas (VS) comprising 10 confirmed NF2 cases and 20 sporadic cases were analyzed. We found loss of heterozygosity (LOH) at the first intron of the p53 gene locus in 54% of the informative cases. This is the first report showing LOH at the p53 gene locus in a significant number of human VS and both sporadic and NF2 cases show the LOH event. Increased levels of normal size p53 mRNA and p53 protein were found in all the tumors analyzed. Thus p53 appears to be deregulated in all the tumors suggesting that p53 alterations may be associated with tumor progression in VS. There was a negative significant correlation of patients' age and percentage of Ser 392 phosphorylated p53 protein. The tumor samples obtained from younger patients of 35 yr and below showed higher percentage of Ser 392 phosphorylated p53 protein compared to the tumors of older patients. The increased percentage of Ser 392 phosphorylated p53 protein indicates that it could be involved in the acceleration of tumor growth in the younger patients. Our results suggest that age dependent phosphorylation of p53 protein and deregulation of p53 gene has a role in the development of human vestibular schwannomas.