theTP53 Gene Research Articles

The lack of correlation between TP53 mutations and gastric cancer: A report from a province of Iran

Gastric cancer ranks second cause of cancer death worldwide after lung cancer. Its etiology is heterogeneous and genetic factors including protooncogenes and tumor suppressor genes always contribute to the progression of cancer. The TP53 tumor suppressor gene has a broad role in genomic stability and DNA repair. The aim of this study was to determine the TP53 gene mutations in gastric cancer specimens in Chaharmahal Va Bakhtiari province of Iran. In this descriptive-lab based study, we investigated the promoter and exons of TP53 gene mutations in 38 paraffin-embedded gastric cancer specimens. DNA was extracted following a standard phenol-chloroform protocol. The TP53 gene mutations were determined using PCR-SSCP & PCR-RFLP procedures. The present study revealed no TP53 gene mutation in the promoter and exons in the gastric cancer subjects studied. While TP53 gene mutations have been reported as the most frequent genetic alterations and are found in about 50% of the human malignancies, no mutation was detected in this study. This may be due to mutations in other related genes in the same pathway or epigenetic factors.

Abstract C61: Genetic alterations in the TP53 genomic region of African American and Caucasian colorectal cancers

Abstract Purpose: In the US, colorectal cancer (CRC) is the second leading cause of cancer-related deaths and the third most common cancer in both men and women. CRC affects African Americans (AAs) disproportionately, relative to non-Hispanic Caucasians (CAs). Data from our prior studies indicate that the p53 codon 72 polymorphism is disproportionately higher in AAs compared to CAs [Clin Cancer Res; 15(14); 2406–-2416. 2009]. It is also evident that genetic human diversity is due not only to single nucleotide polymorphisms (SNPs), but also to structural variants or retrotransposons. Retrotransposons induce mutations, near or within genes by several mechanisms: insertions, deletions, duplications, copy number variants, inversions, or translocations, all of which expand human diversity and possibly alter cancer susceptibility. Thus, our objectives are to establish genomic profiles of the p53 tumor suppressor (TP53) region of CRCs of AA and CA patients to identify race/ethnic-specific alterations that are associated with ancestry, and to develop a DNA sequencing protocol to delineate AA and CA patient profiles using this complex genomic region (∼19 Kb). Methods: Genomic DNA was extracted from 4 frozen tissue samples (2 CRCs and their corresponding normal pairs) and 4 (2 CRCs/normal pairs) formalin-fixed, paraffin-embedded (FFPE) tissues. For the DNA of two CRC patients (one tumor/normal pair each of AA and CA patients), the complete TP53 gene (∼19 Kb, including exons and introns) was amplified by PCR in two halves, followed by Illumina next-generation sequencing and comparison to the human genome 19 reference sequence. For each patient, paired normal (benign/control) and tumor tissue DNAs were compared. Results: TheTP53 gene was amplified from DNA extracted from all 4 frozen CRC tissues, but not from the 4 FFPE tissues. Sequence comparisons of normal versus tumor DNA revealed 80 single nucleotide polymorphisms (SNPs). Most (96%, n=77) located within introns. Of these, 34 were shared by AA and CA patients. In contrast, 8 SNPs were detected only in a CA patient, and 13 others were present only in an AA patient. Two SNPs found in our AA patient were absent in our CA patient and in the publicly available HapMap database of CAs, suggesting that these SNPs reflect African ancestry. Also, 22 SNPs were exclusively present in the CA tumor, whereas only 3 SNPs were unique to the AA tumor. These findings deserve further investigation. Conclusions: We developed PCR protocols that should allow us to conduct a comprehensive mutational profiling of coding and non-coding regions of the TP53 genomic region in DNA isolated from frozen tissues. Comparison of genetic alteration profiles of TP53 in AAs and CAs will aid in determining the race/ethnicity of CRC patients. These studies were supported by a Charles Barkley Foundation grant though the UAB MHRC and a pre-pilot project of the UAB/TU/MSM Partnership grant, U54-CA 118948. Citation Format: Jesus F. Salazar-Gonzalez, Maria G. Salazar, Balananda Dhurjati Kumar Putcha, Edward E. Partridge, Mona N. Fouad, Manne Upender. Genetic alterations in the TP53 genomic region of African American and Caucasian colorectal cancers. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C61. doi:10.1158/1538-7755.DISP13-C61

Abstract A7: Targeting mutant p53 and cell-cell adhesion in ovarian cancer

Abstract One of the most important challenges in the ovarian cancer research is to identify new molecular pathways that can be targeted to kill ovarian cancer cells. High-grade serous ovarian cancer (HGS-OvCa) cells survive, proliferate, and assemble into multicellular clusters that have a capacity to disseminate within the peritoneum. Therefore, it is important to identify specific molecular mechanisms that can be targeted to block survival, growth, and assembly of ovarian cancer multicellular clusters that metastasize within peritoneum. High-grade ovarian tumors originate from the fallopian tube epithelium (FTE) and almost all have mutations in theTP53 gene. The contribution of various mutant p53 proteins (m-p53) to ovarian cancer and whether targeting mutant p53 –dependent molecular mechanisms in ovarian cancer is poorly understood and of clinical significance. We have developed new methodologies and used them to identify m-p53-dependent pathways that support HGS-OvCa survival, proliferation and assembly of multicellular aggregates under condition mimicking peritoneal suspension. To determine whether mutations in TP53 contribute to the ability of HGS-OvCa cells to survive, proliferate, and assemble into multicellular clusters we introduced different variants of mutant p53 (m-p53) into normal human non-transformed FTE cells. We found that expression of m-p53 variants (R175H; R249S; R273H) in FTE cells promoted survival, growth, and assembly of multicellular clusters under conditions mimicking peritoneal suspension. Interestingly m-p53-driven phenotypes were not induced by the loss of p53 expression; and more importantly, these phenotypes were blocked by the reactivation of p53 pathway with small molecule inhibitor NSC319726. We further found that m-p53 induced phenotypes were dependent on the expression of integrin β 1 (ITGB1). The evidence that activated ITGB1 is enriched at cell's surface of precursors of HGS-OvCa within the fallopian tube and HGS-OvCa isolated from ovarian cancer patients highlighted the relevance of these findings to ovarian cancer. We hypothesize that mutant p53 supports survival, growth, and assembly of multicellular HGS-OvCa clusters through mechanisms in which ITGB1 plays a critical role. Our data indicate that observed phenotypes are the consequence of the m-p53 gain of function mechanisms that are amenable to therapeutic inhibitions and targeting m-p53 in HGS-OvCa might be of clinical significance. Citation Format: Marcin P. Iwanicki, Marian Novak, Ioannis K. Zervantonakis, Tan A. Ince, Ronny Drapkin, Joan S. Brugge. Targeting mutant p53 and cell-cell adhesion in ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr A7.

Effect of the codon 72 polymorphism (c.215G>C, p.Arg72Pro) in combination with somatic sequence variants in theTP53 gene on survival in patients with advanced ovarian carcinoma

Effect of the codon 72 polymorphism (c.215G>C, p.Arg72Pro) in combination with somatic sequence variants in theTP53 gene on survival in patients with advanced ovarian carcinoma

Análisis mutacional de los genes de la familiaTP53 en oligodendrogliomas

IntroductionThere is considerable homology amongTP53/TP63/TP73 genes. The last of these is located at 1p36.33; a chromosome region frequently deleted in a wide variety of tumours of the nervous system. This suggests that these genes could be involved in the development of oligodendrogliomas.Material and methodsWe performed a DNA mutation study using PCR/SSCP methods and sequencing of theTP53/TP63/TP73 genes in a series of 41 patients with oligodendrogliomas.ResultsWe found one mutation (518 T→C; Val173Ala) in theTP53 gene and none in theTP63 andTP73 genes. The other nucleotide changes identified corresponded to polymorphisms.ConclusionsThese data suggest that mutations of theTP53 gene family do not appear to play a significant role in the pathology of oligodendrogliomas.

Alterations of theTP53 gene and TP53 protein expression in epithelial ovarian cancer before and after chemotherapy

Background A role for theTP53 (alias p53) tumor-suppressor gene in chemoresistance has recently been discussed, but little is known about the clinical relevance of theTP53 gene to chemoresistance. To elucidate the relevance ofTP53 status to chemoresistance, we investigated theTP53 gene and TP53 protein expression in tumors from the same patients, before and after chemotherapy.

High prevalence of codon 213Arg-->Stop mutations of the TP53 gene in human ovarian cancer in the southwestern part of The Netherlands.

As in many human malignancies, TP53 mutations are the most common genetic alterations in malignant human ovarian tumours. An approach often used in the determination of TP53 status is immunohistochemical staining of the protein. Non-missense mutations, especially those of the null type, causing premature termination codons and resulting in truncated proteins, may often not be detectable by immunohistochemistry. Therefore, current estimates of TP53 alterations in ovarian cancer may be inaccurate. By using polymerase chain reaction-single strand conformation polymorphism analysis and sequencing techniques, we have found a high prevalence of TP53 non-missense mutations in exons 5-8 in ovarian tumour specimens from patients from the southwestern part of The Netherlands. Twenty-nine of 64 tumours showed mutations, of which 10 were non-missense mutations. The majority (9 of 10) of these non-missense mutations, including 7 nonsense mutations and 2 frameshift deletions, were null type mutations and could not be detected by immunohistochemical staining. Five of the 7 nonsense mutations were mutations at codon 213 (Arg-->Stop). The nature of the high prevalence of this nonsense mutation in our series of ovarian carcinomas remains unknown. In addition to the 9 null type mutations, a splice junction mutation was encountered. In conclusion, we have observed a high prevalence (13%) of ovarian tumours with null type mutations in exons 5-8 that did not result in immunostaining. Our data suggest that, especially in ovarian cancer, immunological assessment of TP53 is not an adequate tool to study TP53 alteration. A frequent nonsense mutation at codon 213 in 5 (8%) of 64 tumour specimens represents an important finding.

Molecular alterations in theTP53 gene of peripheral blood cells of patients with chronic myeloid leukemia

The TP53 gene has been extensively studied in patients with chronic myeloid leukemia (CML), both in chronic phase and in blast crisis. Mutations in the gene were found in up to 30% of the patients, especially among those in blast crisis. We report the results of an analysis of 29 blood samples from CML patients: 8 samples from chronic phase patients, 8 from patients in the accelerated phase, and 13 from patients in blast crisis. By using genomic DNA, we sequenced PCR products of the coding exons and most introns of the TP53 gene, finding genetic changes in 30% of the blast crisis samples and 12% in chronic phase. All mutations were found in introns and were previously unreported. Immunocytochemical studies revealed accumulation of TP53 in blood cells of samples both from chronic phase and blast crisis patients. Since these samples had no TP53 mutations, we believe that wild type TP53 accumulates in blood cells of CML patients. Our results, therefore, indicate that molecular changes in coding regions of the TP53 gene are rare. The significance of the abundance of intronic changes should be investigated further. Accumulation of wild type TP53 in CML cells may indicate an additional mechanism involving this gene in the pathogenesis of this disease.

Loss of heterozygosity at the TP53 gene: independent occurrence from genetic instability events in node-negative breast cancer.

TP53 abnormalities have been reported as an early event in the process of cellular transformation of human breast cancers, and involved in mammary-tumor evolution, from in situ to invasive disease. In this study, node-negative (N-) tumors were examined for TP53 allelic loss in relation to different genetic instability events, including allelic loss at chromosome 17p13.3 and c-H-ras-1 loci, as well as alteration of the c-myc and c-erbB-2/neu oncogenes. TP53 allelic loss was analyzed to determine whether such an abnormality was the more important, among other genetic events, in the N- tumors, whether it appeared independently of these genetic events, and whether accumulation of genetic events arises in this group of breast tumors. Clinicopathological parameters were also examined. Loss of heterozygosity (LOH) at the TP53 gene appears the most frequent alteration detected (26% vs. 13%, 8%, 9% and 3% for LOH at D17S30 and c-H-ras-1 loci, and amplification of c-myc and c-erbB-2/neu respectively). There was no association between LOH at the TP53 locus and other genetic events. Among clinicopathological parameters, significant associations were observed only with estrogen-receptor-negative tumors (p = 0.05). Our results demonstrate that LOH at TP53 arises more frequently in the N- breast cancer, thus supporting earlier findings suggesting that TP53 abnormality has a role early in the pathogenesis of breast lesions. Moreover, the data indicate that accumulation of many genetic events occurs at a low level in N- breast tumors, and that TP53 abnormality occurs independently of these genetic events.

Three germline mutations in theTP53 gene

Three germline mutations in the TP53 tumor-suppressor gene are reported, two of which are not reported previously. A missense mutation at codon 265 of TP53 was found in three patients of a family that complied with the definition of the Li-Fraumeni syndrome. A nonsense mutation in codon 306 was found in a woman who had had a rhabdomyosarcoma at age 4 and a subsequent breast cancer at age 22. She was part of a Li-Fraumeni-like family, but the parental origin of the mutation could not be traced. Finally, while screening for somatic alterations in TP53 in a series of 141 sporadic breast tumors, we detected a constitutional missense mutation in codon 235 in a woman diagnosed with breast cancer at age 26 and a recurrence 4 years later. The recurrence, but not the primary tumor, showed an additional missense mutation at codon 245 as well as loss of the wild-type allele. This suggests that the 245 mutation was particularly important for tumor progression and that there might exist heterogeneity in terms of cancer predisposition potential among the various germline TP53 mutations.