Tumor P53 Overexpression Research Articles

Pre- and Post-Zygotic TP53 De Novo Mutations in SHH-Medulloblastoma.

Simple SummaryMedulloblastoma is the most common malignant brain tumor in children. In a subset of cases, a causal factor is a constitutive mutation of the TP53 gene, which may be inherited or arise for the first time in a patient (de novo). Using an immunohistochemistry assay as a screening tool, we selected patients suspected of harboring a TP53 mutation and offered genetic counseling and germline testing. Our study, which was the first to investigate the parental origin of TP53 mutations in medulloblastoma, allowed the identification of two additional cases with de novo mutations. Moreover, we demonstrated that in one patient the mutation originated at a post-zygotic stage, resulting in somatic mosaicism. These findings have important implications for genetic counseling since they highlight the occurrence of both pre- and post-zygotic TP53 de novo mutations in medulloblastoma, pointing out that in a specific subgroup of patients genetic testing should be offered regardless of family history.Li-Fraumeni syndrome (LFS) is an autosomal dominant disorder caused by mutations in the TP53 gene, predisposing to a wide spectrum of early-onset cancers, including brain tumors. In medulloblastoma patients, the role of TP53 has been extensively investigated, though the prevalence of de novo mutations has not been addressed. We characterized TP53 mutations in a monocentric cohort of consecutive Sonic Hedgehog (SHH)-activated medulloblastoma patients. Germline testing was offered based on tumor p53 immunostaining positivity. Among 24 patients, three (12.5%) showed tumor p53 overexpression, of whom two consented to undergo germline testing and resulted as carriers of TP53 mutations. In the first case, family history was uneventful and the mutation was not found in either of the parents. The second patient, with a family history suggestive of LFS, unexpectedly resulted as a carrier of the mosaic mutation c.742=/C>T p.(Arg248=/Trp). The allele frequency was 26% in normal tissues and 42–77% in tumor specimens. Loss of heterozygosity (LOH) in the tumor was also confirmed. Notably, the mosaic case has been in complete remission for more than one year, while the first patient, as most TP53-mutated medulloblastoma cases from other cohorts, showed a severe and rapidly progressive disease. Our study reported the first TP53 mosaic mutation in medulloblastoma patients and confirmed the importance of germline testing in p53 overexpressed SHH-medulloblastoma, regardless of family history.

Abstract 2331: Deletion of ΔNp63 and ΔNp73 in p53 deficient mice results in TAp63 and TAp73 compensation of p53 tumor suppression in vivo.

Abstract p53 tumor suppressor undergoes mutational loss in majority of cancers contributing to tumor formation. Therapeutic strategies are aimed towards p53 overexpression in tumors or to identify targets that compensate for p53-functional loss. p63 & p73, share structural similarities to p53, making them excellent candidates for therapeutic compensation of p53. Unlike p53, p63 and p73 do not undergo mutational loss and their role in tumorigenesis is being delineated. p63 and p73 have two major isoforms, the transactivation (TA), with activities similar to p53 and the delta (Δ)N- isoform with oncogenic functions. Inhibition of TAp63 and TAp73 is observed in cancers as a consequence of overexpression of ΔN isoforms of p63 and p73. In disparity, recent studies report, tumor suppressive properties of ΔNp63 and ΔNp73 in activating genes involved in DNA repair and apoptosis. To define the functional roles of ΔNp63 and ΔNp73 in cancer, mouse models targeting the ΔN isoforms were generated. We observed that, ΔNp63+/- and ΔNp73−/− mice on a p53−/− background had lower thymic lymphoma incidence compared to the p53−/− mice. I found TAp63 and TAp73 up regulated in the double mutant mice that correspond with an increase in p53-downstream apoptotic (PUMA, Noxa, BAX) and cell cycle targets (p21, p16, PML). This suggests that ablation of ΔN isoforms mediate TAp63 and TAp73 up regulation inducing apoptosis or cell cycle arrest by activation of p53-downstream targets. To further demonstrate this, I ablated ΔNp63 and ΔNp73 in vivo in p53−/- mice thymic lymphoma by administering adenoviral-CRE specifically to the thymus. The CRE-treated mice had a significant thymic lymphoma regression within 3 weeks as imaged by MRI in comparison to the mock-treated mouse cohorts. Additionally, RNA-Seq analysis from CRE-treated versus untreated mice, has identified novel metabolic genes with apoptotic or cell-cycle functions. We further report, ΔNp63 and ΔNp73 to bind to promoter site of TAp63 and TAp73 by chromatin immunoprecipitation (ChIP). This supports the notion that ablation of ΔN isoforms of p63 and p73 restores the function of TAp63 and TAp73 thus compensating for p53-tumor suppressive function in vivo. To test, if ablation of ΔN isoforms reduces tumorigenesis in human cancers, ΔNp63 and ΔNp73 were knocked down in human cancer cell lines were p53 expression was ablated or mutated. TAp63 and TAp73 were upregulated in ΔNp63/ΔNp73 knock down human cancer cell lines. However, induction of apoptosis or cell-cycle arrest was observed in p53-deleted cancer cell lines in comparison to the p53-mutated cell lines. This highlights the co-repressive effect of mutant p53, preventing activation of TAp63/TAp73 downstream targets. Current work is aimed towards overcoming mutant p53 effect in these cancer cell lines. Thus, targeting the ΔNp63/ΔNp73 compensates for p53-functional loss mediating tumor suppression. Citation Format: Avinashnarayan Venkatanarayan, Deepavali Chakravarti, Xiaohua Su, Santosh Sandur, Lingzhi Liu, Eliot Fletcher Sananikone, Payal Raulji, Cristian Coarfa, William Norton, Preethi Gunaratne, Elsa Renee Flores. Deletion of ΔNp63 and ΔNp73 in p53 deficient mice results in TAp63 and TAp73 compensation of p53 tumor suppression in vivo. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2331. doi:10.1158/1538-7445.AM2013-2331

Association of p53 and mdm‐2 Polymorphisms and Expression pattern with Breast Cancer in Saudi Arabia

p53 and its regulator mdm‐2 play a crucial role in maintaining genomic stability. Despite the importance of p53 in breast cancer development and progression, little is known about the association of functional SNPs in the p53 and mdm‐2 genes and breast cancer aggressiveness in Saudi population. The present study has assessed p53 and mdm2 transcripts based on genotype pattern in breast cancer patients to understand their relative expression profile. To investigate if p53 and mdm‐2 SNPs regulate their expression, we analyzed association between each SNP and their expression in breast cancer. We found association between SNP status and tumor p53 overexpression. 24 cases of the 50 cases for p53 SNP as having the CC, 15 were CT and 9 had TT genotype. Genotypes were correlated with p53 and mdm‐2 transcript levels to check their independent association. Genotype versus expression analysis has shown that p53 level was 9.65 fold, significantly over expressed in cases with CC genotype (13.81) as compared to CT and TT genotypes, which is 5.58 (p<0.03). Interestingly, p53 SNP is associated with mdm‐2 levels, with 7.68 fold higher expression of mdm2 levels with CC genotype when compared to TT and CT genotypes (3.47). Our results suggest that elevated levels of mdm2 contributes advantage to mdm2 mediated signal transduction events resulting in over expression of genes such as p53 in breast cancer of Saudi population.

Cigarette smoking, body mass index, gastro-esophageal reflux disease, and non-steroidal anti-inflammatory drug use and risk of subtypes of esophageal and gastric cancers by P53 overexpression

A number of risk factors for esophageal and gastric cancers have emerged, yet little is known whether risk factors map to molecular tumor markers such as overexpression of the tumor suppressor TP53. Using a US multicenter, population-based case-control study (170 cases of esophageal adenocarcinomas, 147 gastric cardia adenocarcinomas, 220 non-cardia gastric adenocarcinomas, and 112 esophageal squamous cell carcinomas), we examined whether the risk associated with cigarette smoking, body mass index (BMI), gastroesophageal reflux disease (GERD), and non-steroidal anti-inflammatory drug (NSAID) use varied by P53 overexpression. We defined P53 overexpression through immunohistochemistry of paraffin-embedded tumor tissues, using cutpoints based on percent of cells positive. Polytomous logistic regression was used to assess differences between each case group (defined by tumor subtype and P53 expression) and the control group by risk factors. The proportion of cases overexpressing P53 by tumor subtype was 72% for esophageal adenocarcinoma, 69% for gastric cardia adenocarcinoma, 52% for non-cardia gastric adenocarcinoma, and 67% for esophageal squamous cell carcinoma. For most tumor subtypes, we found little difference in risk factors by tumor P53 overexpression. For non-cardia gastric cancer however, an association with cigarette smoking was suggested for tumors that do not overexpress P53, whereas larger BMI was related to adenocarcinomas that overexpress P53 versus no overexpression. Overall, this study did not find a clear relationship between P53 protein overexpression and the known risk factors for subtypes of esophageal and gastric cancers. Further research on these tumors is needed to identify molecular markers associated with variations in the risk factor profiles.

Detection of Serum Anti-p53 Antibodies from Patients with Ovarian Cancer in China: Correlation to Clinical Parameters

Background: Ovarian cancer has been one of the most common malignant tumor among women in China. The aims of this research were to increase the detection efficiency of anti-p53 antibodies in the sera from patients with ovarian cancer and to assist the diagnosis for patients with ovarian cancer. Methods: The hybrid phage displaying the immunodominant epitope SQAMDDLMLS in p53 N-terminal region was constructed and the fusion protein was prepared and purified. Ninety-two nonselected Chinese women with ovarian cancer were involved in this study. Tumor p53 overexpression was assessed by immunohistochemical analysis of tissue sections. Serum antibodies to p53 were also detected by enzyme-linked immunosorbent assay (ELISA) using recombinant human wild-type p53 protein and the hybrid phage as the coating antigen respectively. Furthermore, the correlations between the anti-p53 antibodies and clinicopathological parameters were analyzed. Results: The positive rate of anti-p53 antibodies in the patients with ovarian cancer was increased (39.1%, 36/92) through the combination of the two ELISA methods compared with each method. The anti-p53 antibodies were not associated with the clinicopathologic parameters, while there was a significant correlation between the presence of p53 Abs and tissue overexpression of p53 in ovarian cancer. Conclusion: These preliminary results demonstrate that the combination of the two ELISA methods increased the positive rate of anti-p53 antibodies in patients with ovarian cancer and provided a useful marker to complement routine clinical diagnosis for patients with ovarian cancer.

P53 protein accumulation as a prognostic marker in sporadic colorectal cancer

p53 protein plays a crucial role in the pathogenesis of a large number of malignancies. In this study, our goal was to elucidate the prognostic role of p53 overexpression and its relationship to clinicopathological variables in colorectal cancer. Between 1999 and 2004, surgical specimens of 258 patients who received surgical treatment for colorectal cancer at the Veterans General Hospital, Taipei were collected. p53 expression in tumor tissue was evaluated by immunohistochemical analysis using the human p53-specific mouse monoclonal antibody, PAb 1801. Of the 258 patients, 97 (37.6%) had overexpression of p53 in tumor tissues. The accumulation of p53 protein in tumor tissues did not correlate with age, gender, preoperative serum carcinoembryonic antigen (CEA) level, mucin content, nodal status, and tumor stage. A statistically significant correlation was found between p53 overexpression and location of the tumor in the rectum (p=0.038). Well to moderately differentiated tumors had significantly higher frequency of p53 overexpression than poorly differentiated tumors (40.0 vs 20.0%, p=0.050). Each patient was followed up for a minimum of 2 years (median 35 months). In univariate analysis, 3-year cancer-specific survival rate was significantly higher in patients with tumor p53 overexpression (88.2%) than in patients without overexpression (log rank test, p=0.037). However, in multivariate analysis, the tumour node metastasis stage remained the most significant independent prognostic factor. The accumulation of p53 protein might have a favorable prognostic value in colorectal cancer, but it is not an independent prognostic factor.

Elevated Serum Levels of Vascular Endothelial Growth Factor Are Associated With Tumor-Associated Macrophages in Primary Breast Cancer

We analyzed serum and tumor samples from 133 patients with operable primary breast cancer to determine the possible relationship between presurgery and postsurgery circulating serum vascular endothelial growth factor (VEGF) levels and tumor-associated macrophage (TAM) numbers, tumor VEGF expression, and other immunohistochemical parameters. A significant positive correlation was observed between the number of TAM and postsurgery circulating VEGF values (P < .05). Moreover, patients with a p53+ tumor had higher postsurgery serum VEGF levels than those with a p53- tumor (P < .05), and tumor p53 overexpression correlated significantly with TAM number (P = .007). We observed no significant association between serum values and tumor VEGF expression. Although the macrophage index was higher in VEGF+ than in VEGF- tumors, the differences were not statistically significant. Our data show a positive interrelation between high circulating VEGF levels, the number of TAM, and p53 overexpression, a relationship that might have an important role in the enhanced angiogenesis processes in breast cancer.

Relation between Serum Anti-p53 Antibodies and Microvessel Density in Bladder Cancer Patients

Introduction: Etiology of serum anti-p53 antibodies in bladder cancer patients is still unknown. In this study we evaluated the relationship between serum anti-p53 antibodies and microvessel density in bladder cancer patients. Materials and Methods: Seventy-six patients with transitional cell carcinoma of the urinary bladder were assessed prospectively (18 Ta, 30 T₁, 28 T₂ ≧). Serum anti-p53 antibodies were detected by enzyme-linked immunosorbent assay. Tumor p53 overexpression was assessed by immunohistochemical staining. Vessels were stained immunohistochemically using an antibody against platelet endothelial cell-adhesion molecule CD31. Spearman correlation test and t test were used for statistical analysis. Results: Serum anti-p53 antibodies were positive in 25 (60%) of 41 tumor p53-positive patients. While the mean (SD, range) microvessel density was found to be 43 (7.59, 8–99) in patients who had positive serum anti-p53 antibodies, it was found to be 23 (4.53, 6–98) in patients who had negative serum anti-p53 antibodies. There was a good correlation between serum anti-p53 antibodies and microvessel density (p < 0.05). No correlation was found between tumor p53 expression and microvessel density (p > 0.05). Conclusions: We found that there is a significant correlation between the microvessel density and serum anti-p53 antibodies. This result may show the role of angiogenesis in the etiology of serum anti-p53 antibodies in bladder cancer patients.

P53 Gene Mutation, Tumor p53 Protein Overexpression, and Serum Anti-p53 Antibody in Patients with Gastric Cancer

【Purpose: The clinical implication of p53 mutation in gastric cancer is still unclear, as shown by the discordant results that continue to be reported in the literature. Materials and Methods: To assess p53 gene mutation, tumor p53 overexpression, and serum anti-p53 antibody, we employed a polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis, an immunohistochemistry using monoclonal antibody DO-7, and an enzymelinked immunosorbent assay (ELISA), respectively. Results: Of 169 surgical specimens of gastric cancer, mutation at exon $5\∼8$ of the p53 was identified in 33 ( $19.5\%$ ) and was significantly correlated with lymph node metastasis. Overexpression of p53 was found in 62 specimens ( $36.7\%$ ) and had a significant correlation with tumor differentiation. Serum anti-p53 antibody was positive in 18 patients ( $10.7\%$ ). Twenty-three of the mutated tumors ( $69.7\%$ ) and 39 of the non-mutated tumors ( $28.7\%$ ) displayed immunoreactivity. Twelve of the immunopositive tumors ( $19.4\%$ ) and 6 of the immunonegative tumors produced anti-p53 antibody. These differences were statistically significant (P】

Prevalence of Serum p53 Antibodies against Tumor p53 Protein in Colorectal Cancer

Background: Genetic events associated to colorectal carcinoma are well characterized, but there is scanty information about this issue in Egyptian subjects. The aim of this study was to investigate tissue p53 overexpression in paraffin embedded tumor and serum p53 antibodies in colorectal cancer patients with special reference to patient outcome. Patients and Methods: The study was conducted to 135 consecutive colorectal cancer patients. The tumor p53 protein was overexpressed in 60% and serum p53 antibodies in 35%, also tumor p53 accumulation is not necessarily associated with serum p53 antibodies positive cases. Tumor p53 overexpression was more frequent in distal colorectum than in proximal tumor (63.7% vs 41%) (p > 0.05). Results: Both tumor p53 overexpression and serum p53 antibodies increased signficantly with the stage of the tumor and lymph node involvement, but not with the grade, histopathological types and other histologic parameters. After a follow-up of 5 years, in the Kaplan Meier univariate analysis the factors stage (p = 0.0004), tumor p53 immunostaining (p < 0.0001) and serum p53 antibodies (p < 0.04) had a prognostic value. Conclusion: In conclusion p53 overexpression was associated with advanced histopathological stage and a high risk of recurrence.

Biologic behavior of and p53 overexpression in multifocal renal cell carcinoma of clear cell type: an immunohistochemical study correlating grading, staging, and proliferation markers.

In the treatment of small renal cell carcinoma (RCC), there is controversy between radical and nephron-sparing surgical treatment because of the risk of tumor multifocality. The biologic behavior of multifocal RCC compared with that of unifocal RCC is not well investigated, and the relevance of p53 and the proliferation markers MIB-1 and proliferating cell nuclear antigen (PCNA) to multifocal RCC is not yet established. In this study, p53 protein overexpression was investigated immunohistochemically in 27 multifocal and 65 unifocal clear cell RCCs using a monoclonal antibody (DO-1). The nuclear expression of p53 was compared with the expression of PCNA and MIB-1 (Ki-67 antigen) and other prognostic factors, including grade and stage. Thirty-three RCCs (35.9%) had p53 positive nuclear staining. MIB-1 positivity was significantly higher in p53 positive tumors than in p53 negative tumors. PCNA positivity was not different in p53 positive tumors compared with p53 negative tumors. Proliferation marker expression was not associated with tumor focality. p53 overexpression was more often found in unifocal tumors than in multifocal tumors. Intracellular accumulation of the p53 protein was related to tumor grade but not to the T classification of tumor stage. In addition, lymph node involvement was significantly associated with p53 overexpression in tumors of the kidney. Focality did not influence progression free survival. This study demonstrated that there is no difference in the proliferative activity or biologic behavior of multifocal and unifocal tumors.

Circulating antibodies against p53 protein in patients with ovarian carcinoma

BACKGROUND Genetic alterations of the p53 tumor suppressor protein are the most frequent molecular events in human carcinogenesis. For as yet unknown reasons, mutant p53 often acts as an immunogen for autoantibody generation. These autoantibodies can be detected in the serum of cancer patients. The presence of such antibodies has been identified in a subset of patients with ovarian carcinoma, but their clinical significance has not been investigated. METHODS Serum samples from patients with ovarian carcinoma were quantitatively analyzed for the presence of p53 autoantibodies with a time-resolved immunofluorometric procedure. Tumor p53 overexpression was assessed by immunohistochemical analysis of tissue sections. Kaplan–Meier survival curves were calculated for p53 antibody positive and negative patients, and the Cox model was used to evaluate the strength of the associations between the presence of serum p53 antibodies and cancer relapse or death, and also between the presence of such antibodies and other clinicopathologic features. RESULTS P53 antibodies were detected in the serum of 41 of 174 patients with ovarian carcinoma (24%). Antibody levels ranged from a few hundred to 9 × 106 arbitrary Units/L, and fluctuated during the course of the disease. p53 antibody positive patients tended to have tumors overexpressing p53, but the association between the two parameters was not statistically significant (P = 0.13). There was also no association between the presence of p53 antibodies and clinical stage, tumor histologic type, or overall patient survival. However, these antibodies were more frequently present in patients older than 50 years (P = 0.001), in patients with moderately or poorly differentiated tumors (P = 0.001), and in patients who received chemotherapy (P = 0.015), and who suffered relapse after surgery (P = 0.018). In univariate analysis, p53 antibody positive patients were at an increased risk for relapse but not death. In multivariate analysis, the differences in disease free and overall survival between patients who were p53 antibody positive or negative were not statistically significant. CONCLUSIONS P53 autoantibodies are found frequently in the serum of patients with ovarian carcinoma. The presence of such autoantibodies was associated with older patient age, more aggressive tumors, and reduced patient disease free survival. In multivariate analysis the prognostic value of p53 autoantibodies was not statistically significant. Cancer 1996;78:2146-52.

Circulating antibodies against p53 protein in patients with ovarian carcinoma

Genetic alterations of the p53 tumor suppressor protein are the most frequent molecular events in human carcinogenesis. For as yet unknown reasons, mutant p53 often acts as an immunogen for autoantibody generation. These autoantibodies can be detected in the serum of cancer patients. The presence of such antibodies has been identified in a subset of patients with ovarian carcinoma, but their clinical significance has not been investigated. Serum samples from patients with ovarian carcinoma were quantitatively analyzed for the presence of p53 autoantibodies with a time-resolved immunofluorometric procedure. Tumor p53 overexpression was assessed by immunohistochemical analysis of tissue sections. Kaplan-Meier survival curves were calculated for p53 antibody positive and negative patients, and the Cox model was used to evaluate the strength of the associations between the presence of serum p53 antibodies and cancer relapse or death, and also between the presence of such antibodies and other clinicopathologic features. p53 antibodies were detected in the serum of 41 of 174 patients with ovarian carcinoma (24%). Antibody levels ranged from a few hundred to 9 x 10(6) arbitrary Units/L, and fluctuated during the course of the disease. p53 antibody positive patients tended to have tumors overexpressing p53, but the association between the two parameters was not statistically significant (P = 0.13). There was also no association between the presence of p53 antibodies and clinical stage, tumor histologic type, or overall patient survival. However, these antibodies were more frequently present in patients older than 50 years (P = 0.001), in patients with moderately or poorly differentiated tumors (P = 0.001), and in patients who received chemotherapy (P = 0.015), and who suffered relapse after surgery (P = 0.018). In univariate analysis, p53 antibody positive patients were at an increased risk for relapse but not death. In multivariate analysis, the differences in disease free and overall survival between patients who were p53 antibody positive or negative were not statistically significant. p53 autoantibodies are found frequently in the serum of patients with ovarian carcinoma. The presence of such autoantibodies was associated with older patient age, more aggressive tumors, and reduced patient disease free survival. In multivariate analysis the prognostic value of p53 autoantibodies was not statistically significant.