Detection of p53 in inflammatory tissue and lymphocytes using immunohistology and flow cytometry: a critical comment

Detection of the p53 response in zebrafish embryos using new monoclonal antibodies

The zebrafish has many advantages as a vertebrate model organism and has been extensively used in the studies of development. Its potential as a model in which to study tumour suppressor and oncogene function is now being realized. Whilst in situ hybridization of mRNA has been well developed in this species to study gene expression, antibody probes are in short supply. We have, therefore, generated a panel of anti-zebrafish p53 monoclonal antibodies and used these to study the p53 response in zebrafish embryos. By immunohistochemistry, we show that the exposure of zebrafish embryos to p53-activating agents such as R-roscovitine and gamma-irradiation results in the accumulation of p53 protein in the gut epithelium, liver and pancreas. A combination of R-roscovitine and gamma-irradiation results in massive p53 induction, not only in the pharyngeal arches, gut region and liver but also in brain tissues. Induction of apoptosis and expression of p53 response genes are seen in regions that correspond to sites of p53 protein accumulation. In contrast, although zebrafish tp53(M214K) mutant embryos showed a similar accumulation of p53 protein, a complete lack of a downstream p53-dependent response was observed. In this system the p53 gene is identified as a p53-responsive gene itself. Our results demonstrate that zebrafish p53 protein can readily be induced in embryos and detected using these new antibody tools, which will increase the usefulness of zebrafish as a model in compound-based screening for novel drugs in cancer research.

p53 is required for spontaneous autoantibody production in B6/lpr lupus mice

The p53 tumor suppressor molecule triggers a key pathway of apoptosis in injured cells, in part through induction of Fas. The importance of Fas as a receptor mediating apoptosis is highlighted by the lupus-like systemic autoimmunity seen in animals and humans with nonfunctional Fas molecules. We set out to see if the absence of p53, superimposed on the Fas defect of lpr mice, might further accelerate or exacerbate their systemic autoimmunity. We generated double mutant mice (p53(-/-) lpr) having defects in both p53- and Fas-dependent pathways, hypothesizing that animals with lesions in both Fas- and p53-dependent pathways would show reduced ability to delete autoreactive or injured cells, thereby producing more severe autoimmune disease. Surprisingly, these mice have lower autoantibody levels than the single mutant lpr mice. These studies suggest an unanticipated role for p53 in the progression of autoimmunity and the production of autoantibodies.

Discrepancy between mRNA and protein expression of tumour suppressor maspin in synovial tissue may contribute to synovial hyperplasia in rheumatoid arthritis

OBJECTIVE

To investigate the expression of maspin in RA synovial tissue and compare it with the expression in osteoarthritis (OA) and normal synovial tissue (NS).

METHODS

Using specific primers for maspin, a 237 bp fragment was amplified from cDNA obtained from cultured RA, OA, and normal synovial fibroblasts (SF) by RT-PCR. Additionally, mRNA expression levels were determined quantitatively by real time PCR. mRNA expression of maspin was investigated on snap frozen and paraffin embedded synovial tissue sections by in situ hybridisation. Immunohistochemistry was used to identify the cell type expressing maspin. SDS-PAGE and western blotting were performed to evaluate the protein expression in cultured SF. To confirm protein synthesis in situ, immunohistochemistry with specific anti-maspin antibodies was performed in synovial tissue sections of patients with RA.

RESULTS

RT-PCR showed expression of maspin in all cDNA samples from cultured SF. Maspin mRNA was found to be decreased in RA SF twofold and 70-fold compared with OA SF and NS SF, respectively. Maspin mRNA was expressed in RA, OA, and normal synovial tissue. Importantly, maspin transcripts were also found at sites of invasion into cartilage and bone. At the protein level, maspin could be detected in RA and, less prominently, OA SF. In RA synovial tissue, maspin protein was detected in only a few synovial lining cells.

CONCLUSION

Maspin is expressed intensively in RA SF at the mRNA level, but only slightly at the protein level, possibly owing to down regulation of maspin; this may contribute to the hyperplasia of synovial tissue in RA.

Over-expression of TATA binding protein (TBP) and p53 and autoantibodies to these antigens are features of systemic sclerosis, systemic lupus erythematosus and overlap syndromes

The aim of this study was to determine the expression levels of p53 and TATA binding protein (TBP) and the presence of autoantibodies to these antigens in Asian Indian patients with systemic sclerosis (SSc), overlap syndromes (OS) and systemic lupus erythematosus (SLE). Fifty patients with SSc, 20 with OS, including mixed connective tissue diseases (MCTD), 20 with SLE, 10 disease controls (DC) and 25 controls (C) were studied. The over-expression of p53 and TBP antigen was determined quantitatively by sandwich enzyme-linked immunosorbent assay (ELISA), varies between four- and sevenfold higher in patients with SSc, OS and SLE, in comparison to DC and C. The expressed protein antigens were not present as free antigens but as immune-complexes. Autoantibodies to p53 were detected by ELISA in 78% subjects with SSc, 100% with OS and 80% with SLE. Autoantibodies to TBP were observed in 28% patients with SSc, 25% with OS and 15% with SLE. In comparison to healthy controls, the titre of antibodies to p53 was significantly higher in patients with SSc (P = 0.00001) than the patients with OS (P = 0.00279) and SLE (P = 0.00289), whereas the titre of antibodies to TBP was higher in patients with OS (P = 0.00185) than the SLE (P = 0.00673) and the SSc (P = 0.00986) patients. Autoantibodies to p53 and TBP were detected in all these patients and the levels of these two autoantibodies showed weak negative correlation with each other. We propose that the over-expression of these antigens might be due to hyperactive regulatory regions in the p53 and TBP gene.

Tumor suppressor protein p53 and anti-p53 autoantibodies in pediatric rheumatological diseases

The tumor suppressor protein p53 plays an important role in cell cycle regulation. One of the major features in rheumatic diseases is the abnormal proliferation of lymphocytes. p53 expression in peripheral blood mononuclear cells (by flowcytometry) and serum anti-p53 antibodies (by ELISA) were therefore measured in 18 children and adolescents with juvenile rheumatoid arthritis (JRA) and 17 with systemic lupus erythematosus (SLE) in comparison to 20 healthy controls, to determine their role. p53 expression in patients was insignificantly higher than that of controls (2.28 +/- 2.71% vs. 1.08 +/- 1.02%, respectively, p > 0.05) with 29.4% of the patients showing values above a cut-off level of 2.55% (95th percentile of controls). SLE patients with active disease had significantly higher p53 expression compared to controls and to patients with quiescent disease although no significant correlation with ESR or complement 3 was detected. Seropositivity to anti-p53 antibodies was observed in none of controls but in 22.8% of patients, all of whom, except one, had active disease. Seropositivity to anti-p53 antibodies was more prominent in lupus nephritis than in other presentations of SLE (p < 0.05). The mean p53 expression in seropositive patients was insignificantly higher than in seronegatives. p53 expression and seropositivity to anti-p53 were slightly higher in SLE than in JRA and were not significantly affected by the mode of therapy. Thus, the overexpression of p53 in some patients with active SLE and JRA might explain the abnormal proliferation of autoreactive lymphocytes that perpetuates the inflammatory response. The presence of anti-p53 antibodies might cause malfunctioning of p53 protein interfering with its regulatory functions.

TP53 mutations in workers exposed to occupational carcinogens

In some cases, evidence exists that exogenous carcinogenic exposures contribute to the mutation spectrum of the TP53 gene (p53) in human cancers. Although the clearest examples come from dietary and environmental sources, only a restricted number of papers have concentrated specifically on TP53 mutations in tumors from workers exposed to occupational carcinogens. In populations exposed to dietary aflatoxin B1 with liver cancer (AFB1) and ultraviolet (UV)-radiation with skin cancer, a single specific-looking TP53 mutation has been described in some of the tumors. Whether these fingerprints in the TP53 gene can be used to reveal an occupational etiology remains to be shown. In other cases, although differences in the TP53 mutation spectrum exist, they are more diffuse and difficult to interpret at this point. For instance, cigarette smoking seems to induce long-lasting molecular footprints in TP53. However, their use to rule out other occupational exposures as etiological factors in occupational cancers is still very questionable, especially due to the putative synergistic effects of cigarette smoke with other carcinogens. Although interesting implications of possible typical mutation spectra among cancers with other occupational etiologies exist, the data are scanty and await further development of TP53 mutation databases.

Comparison of anti-p53 antibodies in immunoblotting

Some of the most important tools to study p53 protein are various anti-p53 antibodies and immunological methods based on antibody-antigen reactions. Critical comments on the specificity and sensitivity of anti-p53 antibodies have been published. Four monoclonal and two polyclonal anti-p53 antibodies, four of them from two different sources, were compared for their ability to detect in immunoblotting the benzo(a)pyrene-induced p53 from C57BL/6 mouse skin and MCF-7 human breast carcinoma cells. Multiple extra bands were seen with most antibodies. A theoretical comparison of the equivalent epitopes of p53 homologues with the known epitopes of p53 antibodies indicated that the extra bands seen with most antibodies are not due to cross-reactivity with these homologues. A careful adjustment of antibody dilutions is needed for each application utilizing commercial p53 antibodies, regardless of the recommendations of the supplier.

p53, proto-oncogene and rheumatoid arthritis

OBJECTIVE

To review the literature published in the past 6 years concerning the role of p53 tumor-suppressor protein in rheumatoid arthritis (RA).

METHODS

A MEDLINE search was performed to identify all publications that covered the role of p53 in RA. In addition, selected articles related to proto-oncogenes and matrix metalloproteinases were included in this review.

RESULTS

p53 protein is expressed in RA fibroblast-like synoviocytes (FLSs), and its overexpression is a characteristic feature of RA. The overexpression of p53 is probably induced by DNA strand breaks caused by the genotoxic environment of RA joints, in some cases because of p53 mutations. Independent studies from 3 groups indicated that p53 mutations can and do occur in RA synovial tissue samples derived from a subset of RA patients. Inactivation of p53 may contribute to the invasiveness of FLSs and to the high-level expression of cartilage degradation enzymes as well. Gene transfer or gene knockout studies using a collagen-II-induced RA animal model to examine the role of p53 in RA have been reported. Initial results are positive and indicate that gene transfer of p53 may be clinically useful for the management of RA.

CONCLUSIONS

p53 protein is expressed in RA FLSs, and its overexpression is a characteristic feature of RA. p53 mutations occur in the synovial tissues derived from a subset of RA patients. The clinical implications of p53 expression and the functional importance of somatic mutations in RA, however, are still unclear. Further research is needed to fully understand the implications of these findings and develop corresponding new therapeutic strategies.

The p53 status in juvenile chronic arthritis and rheumatoid arthritis

The aim of this study was to investigate the p53 status in two autoimmune diseases; juvenile chronic arthritis (JCA) and rheumatoid arthritis (RA). In a PCR-sequencing analysis of exons 4-9 of the p53 gene, no mutation was identified, except for the case of an RA synovectomy sample with two mutations of intron 7. p53 gene polymorphisms for codons 36, 47, and 213 were not detected. Codon 72 polymorphism showed an indication of an increased occurrence of the Pro/Pro allelotype in JCA. Expression of P53 protein was comparable for JCA and RA synovectomy samples. For all RA samples P53 protein was detectable, whereas one sample of a JCA patient failed to express P53 protein.

Rheumatoid arthritis and p53: how oxidative stress might alter the course of inflammatory diseases

Oxidative stress at sites of chronic inflammation can cause permanent genetic changes. The development of mutations in the p53 tumor suppressor gene and other key regulatory genes could help convert inflammation into chronic disease in rheumatoid arthritis and other inflammatory disorders.

Apoptosis and p53 expression in rat adjuvant arthritis

STATEMENT OF FINDINGS: The kinetics of apoptosis and the apoptosis-regulating gene p53 in adjuvant arthritis (AA) were investigated to assess the value of the AA rat model for testing apoptosis-inducing therapies. Very few terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end-labeling (TUNEL)-positive cells were detected during the early phases of AA, but on day 23 (chronic arthritis) the percentage of TUNEL-positive cells was significantly increased. Expression of p53 in synovial tissue gradually increased from days 5-23, which was markedly higher than p53 levels in rheumatoid arthritis (RA) synovium. Significant apoptosis only occurs late in rat AA and is concordant with marked p53 overexpression, making it useful model for testing proapoptotic therapies, but rat AA is not the best model for p53 gene therapy because dramatic p53 overexpression occurs in the latter stages of the disease.

P53 gene protein overexpression predicts results of trimodality therapy in esophageal cancer patients

BACKGROUND

P53 protein overexpression in esophageal cancer and its correlation with response and survival after chemoradiation was retrospectively investigated.

METHODS

Pretreatment and resection specimens were stained by automatic p53 immunohistochemical staining technique.

RESULTS

P53 was expressed in 84.0% of esophagoscopy (EGD) biopsies; 71.4% of patients with metastasis of thoracoscopy/laparoscopy lymph nodes (TS/LS LN) identified by hematoxylin/eosin (H/E) were p53 (+); 14.2% of patients with negative TS/LS LN by H/E were p53 (+). Eleven out of 18 patients with p53 (+) in pretreatment EGD remained p53 (+) after chemoradiation; 38.8% of these patients had a pathological complete response (pCR). The median survival of this group was 15 months. Of 4 patients with p53 (-) pretreatment EGD, all of those were still p53 (-) after chemoradiation; 75% of these patients had pCR. The median survival was 30 months. In patients with p53 (+) TS/LS LN, 23% had a pCR after chemoradiation with a median survival of 16 months. In patients with p53 (-) TS/LS LN, 50.0% had a pCR with a median survival of 31.5 months.

CONCLUSIONS

P53 protein overexpression in pretreatment EGD and TS/LS LN may predict response to chemoradiation and survival in esophageal cancer patients.

Analysis of the p53 tumor suppressor gene in rheumatoid arthritis synovial fibroblasts

OBJECTIVE

To determine whether mutations in the tumor suppressor gene p53 may contribute to the transformed-appearing phenotype of rheumatoid arthritis (RA) synovial fibroblasts.

METHODS

We performed p53 gene mutation analysis using different molecular approaches. Synovial fibroblasts of 10 patients with RA were cultured and RNA and DNA were harvested after 3-5 passages in cell culture. Sequence analysis of all exons of the p53 gene was performed using 3 different techniques: 1) single-strand conformational polymorphism, 2) nonisotopic RNase cleavage assay, and 3) base excision sequence scanning T-scan, followed by sequence analysis of specific gene segments.

RESULTS

Although p53 antigen could be detected by immunocytochemistry in numerous cultured fibroblasts, gel electrophoresis analysis of products obtained using all 3 methods and subsequent sequence analysis showed no specific mutation pattern in the genome of the synovial fibroblasts from patients in Germany, including the known "hot spots" within the p53 genome. However, p53 mutations were identified in different clones of 3 additional RA synovial fibroblast populations from the United States. Sequence analysis of the p53 promoter did not reveal mutational base changes.

CONCLUSION

The findings of the study support the hypothesis that the majority of the mutations of the p53 gene observed in RA synovium are not derived from the genome of RA synovial fibroblasts, and that the variability of the mutation pattern reflects, in part, the heterogeneity of the disease.

Dominant-negative p53 mutations in rheumatoid arthritis

OBJECTIVE

Studies were performed to determine if p53 mutations identified in rheumatoid arthritis (RA) synovial tissue are dominant negative.

METHODS

Site-directed mutagenesis was used to produce 2 RA-derived mutants: asparagine-->serine at codon 239 (N239S) and arginine-->stop at codon 213 R213*). HS68 dermal fibroblasts were transfected with either empty vector, wild-type p53 cDNA (wt), or the N239S or R213* mutant p53 cDNA clones. Interleukin-6 (IL-6) and bax gene expression were determined by Northern blot analysis. Bax transcription was determined using a bax promoter/reporter gene construct (bax-luc).

RESULTS

Transfection of HS68 cells with wt increased bax mRNA levels. This process was blocked by cotransfection with either mutant. The mutant p53 genes also increased IL-6 gene expression. Low levels of bax promoter activity were detected in HS68 cells co-transfected with bax-luc and empty vector, N239S, or R213*, indicating that the RA mutants lacked transcriptional activity. Transfection with wt and bax-luc led to a 10-fold increase in luciferase expression. When the wt gene was cotransfected with either of the mutants, there was a dose-dependent inhibition of bax promoter activity.

CONCLUSION

These data indicate that at least 2 of the p53 mutants identified in RA joint samples are dominant negative and suppress endogenous wild-type p53 function.