Expression of p53 protein in normal, dysplastic, and malignant gastric mucosa: an immunohistochemical study

Tumor suppressor OTUD3 induces growth inhibition and apoptosis by directly deubiquitinating and stabilizing p53 in invasive breast carcinoma cells

Background

P53 pathway inactivation plays an important role in the process of breast cancer tumorigenesis. Post-translational protein modification abnormalities have been confirmed to be an important mechanism underlying inactivation of p53. Numerous deubiquitinating enzymes are aberrantly expressed in breast cancer, and a few deubiquitination enzymes can deubiquitinate and stabilize p53. Here, we report that ovarian tumor (OTU) deubiquitinase 3 (OTUD3) is a deubiquitylase of p53 in breast carcinoma (BC).

Methods

Correlations between the mRNA expression levels of OTUD3, TP53 and PTEN and the prognosis of BC were assessed with the Kaplan-Meier Plotter tool. OTUD3 protein expression in 80 pairs of specimens in our cohort was examined by immunohistochemistry and western blotting. The relationship among OTUD3, p53, and p21 proteins was analyzed. Half-life analysis and ubiquitylation assay were performed to elucidate the molecular mechanism by which OTUD3 stabilizes p53. The interaction between OTUD3 and p53 in BC cells was verified by a co-immunoprecipitation assay and GST pulldown experiments. MTS assay for proliferation detection, detection of apoptosis induced by cisplatin and colony formation assay were employed to investigate the functional effects of OTUD3 on breast cancer cells.

Results

OTUD3 downregulation is correlated with a poor prognosis in BC patients. OTUD3 expression is decreased in breast cancer tissues and not associated with the histological grade. OTUD3 also inhibits cell proliferation and clone formation and increases the sensitivity of BC cells to apoptosis induced by chemotherapy drugs. Reduced OTUD3 expression accompanied by decreased p53 abundance is correlated with human breast cancer progression. Ectopic expression of wild-type OTUD3, but not its catalytically inactive mutant, stabilizes and activates p53. Mechanistically, OTUD3 interacts directly with p53 through the amino-terminal OTU region. Finally, OTUD3 protects p53 from murine double minute 2 (Mdm2)-mediated ubiquitination and degradation, enabling the deubiquitination of p53 in BC cells.

Conclusions

In summary, we found that OTUD3 may be a potential therapeutic target for restoring p53 function in breast cancer cells and suggest that the OTUD3-p53 signaling axis may play a critical role in tumor suppression.

Expression of Hematopoietic Stem and Endothelial Cell Markers in Canine Hemangiosarcoma

Several chemicals and pharmaceuticals increase the incidence of hemangiosarcomas (HSAs) in mice, but the relevance to humans is uncertain. Recently, canine HSAs were identified as a powerful tool for investigating the pathogenesis of human HSAs. To characterize the cellular phenotype of canine HSAs, we evaluated immunoreactivity and/or messenger RNA (mRNA) expression of markers for hematopoietic stem cells (HSCs), endothelial cells (ECs), a tumor suppressor protein, and a myeloid marker in canine HSAs. Neoplastic canine cells expressed EC markers and a myeloid marker, but expressed HSC markers less consistently. The canine tumor expression results were then compared to previously published immunoreactivity results for these markers in human and mouse HSAs. There are 2 noteworthy differences across species: (1) most human HSAs had HSC marker expression, indicating that they were comprised of tumor cells that were less differentiated than those in canine and mouse tumors; and (2) human and canine HSAs expressed a late-stage EC maturation marker, whereas mouse HSAs were negative, suggesting that human and canine tumors may retain greater differentiation potential than mouse tumors. These results indicate that HSA development is variable across species and that caution is necessary when discussing translation of carcinogenic risk from animal models to humans.

XZ-1 regulates cell apoptosis of gastric epithelial dysplasia via NF-κB/p53/Ki67 signaling pathway

We aimed to determine the effect of ‘Xiaozeng No. 1’ (XZ-1) on cellular apoptosis changes of gastric epithelial dysplasia (GED) and to explore the underlying mechanism. Specimens taken from the pyloric area of the stomachs from rats in each group were subjected to Hematoxylin and Eosin (H&E) staining for pathological examination, TUNEL staining for apoptosis detection, and Western blot analysis for apoptosis-related proteins. The results showed that XZ-1 decreased GED incidence and enhanced gastric epithelial apoptosis. Furthermore, XZ-1 up-regulated the proapoptotic proteins including cleaved caspases (cysteine-dependent aspartate-specific protease) (-3, -8, and -9), Fas, Bax, and Bid, and facilitated the release of cytochrome c from mitochondria to the cytoplasm. Interestingly, XZ-1 enhanced protein expression of NF-κB p65, Ki67, and p53. Moreover, inhibition of NF-κB pathway suppressed the XZ-induced p53 expression, whereas inhibition of NF-κB or p53 pathway suppressed the XZ-induced Ki67. More importantly, inhibition of NF-κB or p53 pathway attenuated the XZ-1-mediated induction of gastric epithelial apoptosis and decline of GED incidence. Collectively, our results demonstrated that XZ-1, almost equivalent effect exerted by the positive control Retin-A, dramatically decreased GED incidence and enhanced gastric epithelial apoptosis. Meanwhile, XZ-1 activated the NF-κB/p53/Ki67-apoptosis signaling pathway, which might be one of the mechanisms whereby XZ-1 reversed GED.

Clinical significance of serum anti-p53 antibody expression following curative surgery for colorectal cancer

The aim of the present study was to investigate the usefulness of serum anti-p53 antibody (Ap53Ab) measurement for the diagnosis of colorectal cancer (CRC), and the clinical significance of the association between Ap53Ab expression and survival rate. Ap53Ab, carcinoembryonic antigen (CEA) and carbohydrate antigen (CA)19-9 were measured by ELISA in 674 CRC patients and 115 healthy volunteers (control group). The half-life time of Ap53Ab and CEA was calculated. The association between positive Ap53Ab expression and clinicopathological characteristics, including survival rate, was analyzed. Of the 674 CRC patients, 195 (28.9%) were positive for Ap53Ab expression, while the positive rates of CEA and CA19-9 level were 39.9 and 16.9%, respectively. Positivity for Ap53Ab alone was observed in 94 patients (13.9%), whereas the positivity rate of any markers examined was 58.7%. The mean half-life of Ap53Ab and CEA was 30.7 and 11.3 days, respectively. Positive expression of Ap53Ab was significantly associated with the depth of tumor invasion (P<0.001), lymph node metastasis (P=0.024), stage (P<0.001) and CEA level (P=0.005). No significant correlation between Ap53Ab expression and poor survival rate was observed. The positive rate of Ap53Ab was higher compared with that of CEA and CA19-9 in early-stage CRC. The combination of these markers improved the diagnostic yield of CRC up to ~60%. Furthermore, Ap53Ab expression was associated with lymph node metastasis, but not with shorter survival. These results indicated that the measurement of Ap53Ab may contribute to increased rate of detection of CRC, particularly in patients with early-stage disease, in clinical practice.

p53 Accumulation in Malignant Bone Tumors: An Immunohistochemical Analysis of 217 Cases

Using formalin-fixed paraffin-embedded tissue specimens, the authors studied the accumulation of p53 protein in various malignant bone tumors. p53 accumulation was detected in osteosarcoma (16.7%), malignant fibrous histiocytoma (MFH) of bone (30.4%), and chordoma (16.7%). In osteosarcoma, no difference was seen in the incidence of p53 accumulation according to the histologic grade of malignancy and any clinical factors including prognosis, but the incidence was significantly higher in conventional osteosarcoma than in other subtypes of osteosarcoma. In MFH of bone, the p53-positive group had a significantly worse prognosis compared with the p53-negative group. p53 accumulation is thus considered to be related to the prognosis of MFH of bone although it did not demonstrate any prognostic value for osteosarcoma in the current study.

p53 Protein and Proliferating Cell Nuclear Antigen (PCNA) Expression in Small Round Cell Tumors of Bone and Adjacent Soft Tissue

Sixty small cell tumors of bone and adjacent soft tissue were studied in an attempt to define the incidence of immunohistochemically detectable p53 protein and cor relate these findings with the results of proliferating cell nuclear antigen (PCNA) immunohistochemical staining and mitotic counts. All of the lesions had been for malin-fixed and paraffin-embedded; half were subjected to decalcification prior to processing. The study population included 12 Ewing's sarcomas of bone, 3 atypical Ewing's sarcomas of bone, 3 primitive neuroectodermal tumors of bone, 11 Askin tumors of the thoracopulmonary region, 11 small cell osteosarcomas of bone, 10 mesenchymal chondrosarcomas of bone, and 10 malignant lymphomas involving bone. The patients ranged in age at the time of presentation from 17 to 67 years. Overall, the incidence of p53 positivity was extremely low in these lesions, irre spective of tumor type. Positive nuclear staining with an antibody to p53 was found in none of the 12 Ewing's sarcomas, none of the 3 atypical Ewing's sarcomas, none of the 3 primitive neuroectodermal tumors of bone, 1 of the 11 Askin tumors of the thoracopulmonary region (1.5% of tumor cells positive), 1 of the 11 small cell osteosarcomas (2% of tumor cells positive), 1 of the 10 mesenchymal chondrosar comas of bone (7% of tumor cells positive), and 2 of the 10 malignant lymphomas involving bone (0.5% and 1% of tumor cells positive, respectively). The majority of tumors showed PCNA positivity within the tumor cells, although the incidence of PCNA positivity within the histologic types varied greatly; in general, the higher PCNA counts corresponded to higher mitotic counts within the individual lesions. The present study did not demonstrate any correlation between mutant p53 accu mulation detected by immunohistochemistry and tumor type, and so it is unlikely that p53 positivity will prove to be of great use in the differential diagnosis of these lesions. A correlation between p53 positivity and PCNA staining or mitotic activity was not apparent. Int J Surg Pathol 2(4):259-268, 1995

Molecular genetics of gastric adenocarcinoma in clinical practice

The molecular genetics of gastric carcinoma (GC) dictates their biology and clinical behavior. The two morphologically distinct types of gastric carcinoma by Lauren classification, i.e., intestinal and diffuse cell types, have a significant difference in clinical outcome. These two types of GC have different molecular pathogenetic pathways with unique genetic alterations. In addition to environmental and other etiologies, intestinal type GC is associated with Helicobacter pylori (H. pylori) infection and involves a multistep molecular pathway driving the normal epithelium to intestinal metaplasia, dysplasia, and malignant transformation by chromosomal and/or microsatellite instability (MSI), mutation of tumor suppressor genes, and loss of heterozygosity among others. Diffuse type shows no clear causal relationship with H. pylori infection, but is commonly associated with deficiency of cell-cell adhesion due to mutation of the E-cadherin gene (CDH1), and a manifestation of the hereditary gastric cancer syndrome. Thus, detection of CDH1 mutation or loss of expression of E-cadherin may aid in early diagnosis or screening of diffuse type GC. Detection of certain genetic markers, for example, MSI and matrix metalloproteinases, may provide prognostic information, particularly for intestinal type. The common genetic alterations may offer therapeutic targets for treatment of GC. Polymorphisms in Thymidylate synthase to metabolize 5-fluorouracil, glutathione S-transferase for degradation of Cisplatin, and amplification/overexpression of human epidermal growth factor receptor 2 targeted by monoclonal antibody Trastuzumab, are a few examples. P13K/Akt/mTOR pathway, c-Met pathways, epidermal growth factor receptor, insulin-like growth factor receptor, vascular endothelial growth factor receptor fibroblast growth factor receptor, and micro RNAs are several potential therapeutic biomarkers for GC under investigation.

Pathology of gastric cancer and its precursor lesions

Gastric cancers are a histologically heterogenous group of neoplasms arising from unique epidemiologic and molecular backgrounds. There is accumulating evidence that the intestinal type of gastric adenocarcinoma develops through a multistep process beginning with chronic gastritis triggered primarily by Helicobacter pylori and progressing through atrophy, intestinal metaplasia, and dysplasia (intraepithelial neoplasia) to carcinoma. Loss of E-cadherin expression resulting from CDH1 gene alterations is the primary carcinogenetic event in hereditary diffuse gastric cancer. Proximal gastric adenocarcinomas likely result from either gastroesophageal reflux or H pylori gastritis. This article provides an update of the histologic, immunohistochemical, and molecular pathways of gastric cancer and its precursors.

Fiber-optic Raman spectroscopy probes gastric carcinogenesis in vivo at endoscopy

Intestinal-type gastric carcinogenesis is a complex multi-step disease, and early precursors (e.g. intestinal metaplasia (IM), dysplasia) can be very challenging to identify using conventional white-light endoscopic imaging. This study aims to assess the capability of Raman spectroscopy for multi-class elucidation of intestinal-type gastric carcinogenesis sequence in vivo for improving precancer detection at endoscopy. We employ a novel image-guided Raman endoscopy technique developed for in vivo gastric tissue Raman measurement within 0.5 s during clinical endoscopic examination. We have acquired a total of 1277 in vivo Raman spectra from 83 gastric patients associated with intestinal-type carcinogenesis. In vivo Raman spectroscopy integrated with semi-quantitative spectral modelling (e.g. DNA, lipids, glycoprotein, proteins and blood) reveals the progressive changes of biochemical constituents in gastric tissue associated with preneoplastic and neoplastic transformation (i.e., IM, dysplasia and adenocarcinoma). Multi-class probabilistic partial least squares-discriminant analysis (PLS-DA) diagnostic algorithms based on in vivo Raman spectra are able to identify normal mucosa with sensitivity of 75.88% and specificity of 87.21%; IM with sensitivity of 46.67% and specificity of 87.55%; dysplasia with sensitivity of 83.33%; specificity of 95.80%, and adenocarcinoma with sensitivity of 84.91% and specificity 95.57%, respectively. This work demonstrates that Raman spectroscopy is a sensitive biomolecular probe for monitoring intestinal-type gastric carcinogenesis to realize early diagnosis and detection of precancer and early gastric cancer in vivo during clinical endoscopic examination.

Expression of p53-MDM2 feedback loop related proteins in different gastric pathologies in relation to Helicobacter pylori infection: implications in gastric carcinogenesis

AIM

To explore the association of p53-MDM2 feedback loop related proteins with gastric pathologies in relation to Helicobacter pylori infection.

METHODS

Gastric biopsies were obtained from 157 H. pylori-negative and positive patients, including normal gastric mucosa (NGM), chronic gastritis (CG), intestinal metaplasia (IM), dysplasia (Dys), and gastric cancer (GC). The expression of mutant p53, MDM2, Bax and PUMA in gastric tissues was detected by immunohistochemistry.

RESULTS

Overall expression of MDM2 and Bax is progressively increased from NGM to GC. PUMA expression is increased in CG but subsequently decreased after the development of IM. H. pylori infection is associated with increased mutant p53 and Bax expression but decreased PUMA expression in IM, and increased MDM2 expression in Dys.

CONCLUSIONS

These results suggest that different p53-MDM2 feedback loop related proteins are distinctly expressed in the various stages of gastric carcinogenesis; their roles in gastric carcinogenesis in the presence of H. pylori infection need to be further investigated.

Molecular Genetics of Gastric Adenocarcinoma

Gastric carcinoma is the second leading cause of cancer deaths in the world. Its aetiology is closely linked to the bacterial pathogen Helicobacter pylori which is believed to induce a state of chronic inflammation that predisposes to a cascade of molecular and cellular alterations leading to carcinogenesis. Although the exact process of gastric carcinogenesis has yet to be elucidated fully, the interaction of the genetic factors with environmental factors is likely to be a significant consideration. Numerous genes and molecular pathways have been discovered to be associated with gastric adenocarcinoma and more importantly, it is now becoming possible to use some of these as means of prognostication and targeted therapy. This review will outline our current understanding of the aetiology and molecular genetics of gastric adenocarcinoma and its current clinical applications.

The discrepancy between genetic polymorphism of p53 codon 72 and the expression of p53 protein in Helicobacter pylori-associated gastric cancer in Korea

The p53 gene has been referred to as 'the guardian of the genome' because it controls apoptosis and cell cycle arrest. The purpose of this study was to evaluate the association of p53 codon 72 genetic polymorphism and the p53 immunohistochemistry with Helicobacter pylori-associated gastroduodenal diseases, including gastric cancer. This study included 1,852 subjects: controls and patients with gastric cancer, dysplasia, benign gastric ulcers, and duodenal ulcers (DU). Biallelic polymorphism was genotyped by restriction fragment length polymorphism. Immunohistochemical analysis for the detection of mutant type p53 expression was performed. The frequency of the Pro/Pro allele of the p53 codon 72 was higher in the patients with H. pylori-positive dysplasia than in controls (OR: 2.3, 95% CI: 1.3-4.3), but it was less frequent among patients with a H. pylori-positive DU (OR: 0.5, 95% CI: 0.3-0.8). However, there was no significant association with gastric cancer, including the location, stage, or histological type of gastric cancer. Expression of a mutant type of p53 protein was detected in 6.3% of dysplastic tissues and 26.5% of cancerous tissues compared 0% in the controls. Positive expression was higher in the intestinal type of cancer (34.9%) than in the diffuse type (15.0%; P = 0.001). These results suggest that genetic polymorphism of p53 codon 72 played a role in the determination of H. pylori-associated gastroduodenal diseases, but p53 immunostaining did not correlate with those of the p53 genetic polymorphism analysis.

Gastric epithelial dysplasia: the Western perspective

The need for early diagnosis of gastric cancer is emphasized by the fact that gastric cancer remains the second most common cause of cancer related deaths worldwide. The aggressive surveillance and definite therapy for low and high-grade dysplasia, which can be achieved endoscopic means, remains the cornerstone of clinical management. Although the precursor status of dysplasia is not contested, its classification is controversial and fraught with marked inter-observer variations. Most cases of gastric dysplasia have an "intestinal" phenotype referred to as adenomatous dysplasia. Hyperplastic (type II dysplasia) is another less common variant. The progression of dysplasia to carcinoma is paralleled by a stepwise accumulation of multiple, but yet uncertain, genetic abnormalities. There are no immunohistochemical or molecular assays that can stratify with certainty the risk of progression to cancer. Given the low rate of transformation of low-grade dysplasia, annual endoscopic surveillance with re-biopsy is advocated. A diagnosis of indefinite for dysplasia should also prompt endoscopic surveillance. A diagnosis of high-grade dysplasia is more ominous, since it progress to cancer in most cases. However, the novel imaging and endoscopic modalities have modified management strategies with mucosal lesions amenable to endoscopic resection, while surgical resection is reserved to invasive adenocarcinoma with submucosal invasion.

Cytogenetic and molecular aspects of gastric cancer: clinical implications

Gastric cancer is of major importance world-wide being the second most common cause of cancer-related death in the world. According to Lauren's histological classification gastric cancer is divided in two groups, the better differentiated intestinal carcinomas and the poorly differentiated diffuse-type cancers. The genetic changes underlying the initiation and progression of gastric cancer are not well defined. Gastric carcinogenesis is a multistep process involving a number of genetic and epigenetic factors. Although it has been proposed that different genetic pathways exist for differentiated and undifferentiated carcinomas, the two histological subtypes of gastric cancer share some common genetic alterations. Currently, tumor histology and pathologic stage are the major prognostic variables used in the clinical practice for gastric cancer patients. However, it is known that tumors with similar morphology may differ in biological aggressiveness, prognosis and response to treatment. Molecular genetic analysis of gastric cancer revealed a number of associations of certain genetic changes with pathological features, tumor biological behavior and prognosis of gastric cancer patients, suggesting that these genetic abnormalities might play an important role in gastric tumorigenesis. Increasing evidence suggests that the molecular genetic changes could be helpful in the clinical setting, contributing to prognosis and management of patients. Regarding epigenetic events in gastric tumorigenesis, a number of methylating markers have been proposed for risk assessment, prognostic evaluation and as therapeutic targets. However, further research is required in order to systematically investigate the genetic changes in gastric cancer estimating also their usefulness in the clinical practice. A good understanding of the genetic changes underlying gastric carcinogenesis may provide new perspectives for prognosis and screening of high risk individuals. Some of the genetic alterations could definitely improve tumor classification and management of gastric cancer patients. Also, based on molecular data identified in gastric cancer novel therapeutics might help to improve the treatment of this disease.

Gastric preneoplastic lesions and epithelial dysplasia

The incidence of gastric cancer is declining; however, it remains the second most common cause of cancer-related deaths worldwide. This article describes gastric preneoplastic lesions and epithelial dysplasia. The possible role of Helicobacter pylori infection is emphasized.

Prognostic value of immunohistochemistry in gastric neuroendocrine (carcinoid) tumors

Three subtypes of enterochromaffin-like cell tumors (carcinoids) have been described: type I, associated with chronic atrophic gastritis; type II, multiple endocrine neoplasia 1 and Zollinger-Ellison syndrome; and type III, sporadic tumors.

OBJECTIVES

(i) To investigate the immunoexpression of Ki-67, p53 and Bcl-2 proteins in enterochromaffin-like cell (carcinoid) tumors and (ii) to evaluate the prognostic value of these markers.

METHODS

Fifty-four samples from 21 patients with gastric carcinoid tumors were sectioned and immunostained using avidin-biotin peroxidase method.

RESULTS

The mean age was 62.2+/-11.4 years (36-83 years-old) and 13 (61.9%) were women. Type I lesions were detected in 61.9% and type III in 38.1%. Tumors were single in 10 (47.6%) and were multiple and/or multicentric in 11 (52.4%). Nuclear p53 immunoreactivity was observed in 6/21 patients (28.6%), and all of them were type III tumors (6/8), compared with no p53 expression in type I (0/13), P=0.0002. p53 expression was also associated with high degree of cell proliferation (Ki-67-positive nuclear cells), P=0.00001. Bcl-2 expression was either unreactive or weakly positive in all tumor lesions. The mean follow-up period was 50.4 months (SD=45.2), varying from 6 to 144 months. Overall survival time of patients with positive p53 expression and high proliferative rate was significantly lower than that of negative patients (14.4 vs 123 months, P=0.0007).

CONCLUSIONS

(i) p53 immunoexpression associated with high proliferative rate was useful to distinguish between type I and type III gastric carcinoid tumors and (ii) these markers were able to predict a shorter survival.

Aneuploidies, deletion, and overexpression of TP53 gene in intestinal metaplasia of patients without gastric cancer

Gastric carcinogenesis is attributable to interacting environmental and genetic factors, through a sequence of events including intestinal metaplasia. Using a fluorescence in situ hybridization technique, we investigated the occurrence of aneuploidies of chromosomes 3, 7, 8, 9, and 17, TP53 gene deletion, and expression of p53 in 21 intestinal metaplasia (IM) samples from cancer-free patients and in 20 gastric adenocarcinoma samples. Aneuploidies were found in 71% (15/21) of the IM samples. Trisomy of chromosomes 7 and 9 occurred mainly in complete-type IM; in the incomplete type, trisomy of chromosomes 7 and 8 were more commonly found. The TP53 gene deletion was observed in 60% (3/5) of the IM cases, and immunohistochemistry revealed p53 overexpression in 12% (2/17) of the analyzed IM cases. All gastric adenocarcinoma cases presented higher frequencies of trisomy or tetrasomy of chromosomes 3, 7, 8, 9, and 17. The TP53 deletion was found in all three of the gastric adenocarcinoma analyzed for it, and immunohistochemistry detected overexpression of protein p53 in 80% (12/15) of the analyzed cases. Our study revealed for the first time the presence of aneuploidies of chromosomes 7, 8, 9, and 17 and of TP53 gene deletion and overexpression in IM samples from cancer-free patients. These results suggest that IM and gastric adenocarcinoma may share the same genetic alterations.

Enhanced TGFalpha-EGFR expression and P53 gene alterations contributes to gastric tumors aggressiveness

We determined whether alterations in the expression of p53, p16(INK4) and p21(WAF1/CIP1) influence the invasiveness of a subset of gastric adenocarcinomas co-expressing TGFalpha and EGFR. Immunopositivity for TGFalpha-EGFR (26%) was observed in both early and advanced adenocarcinomas, and 88% of these showed immunoreactivity for p53. SSCP analysis revealed that in 81% of these tumors the p53 gene was mutated in exons 5-8. The intensity of p53 immunoreactivity was significantly higher (P < 0.013) in deeply invasive tumors. p16(INK4) and p21(WAF1/CIP1) immunoreactivity was detected in 93 and 76% of the samples co-expressing TGFalpha-EGFR but the levels were not correlated with those of p53 and other clinico-pathological parameters. We conclude that gastric adenocarcinomas potentially dependent upon the TGFalpha-EGFR autocrine loop for growing exhibit increased aggressiveness in the presence of aberrant p53.

Detection of p53 mutations in precancerous gastric tissue

Intestinal-type gastric cancer is preceded by gastritis and intestinal metaplasia. There is uncertainty regarding the stage at which genetic alterations in the p53 gene occur. Reactive oxygen species (ROS) may participate in the production of mutations and the inactivation of p53 is due to infection by the bacterium Helicobacter pylori. We have investigated whether alterations of the p53 gene can be detected in gastritis and intestinal metaplasia using the restriction site mutation assay. We also assessed the potential contribution of ROS to p53 inactivation using electron spin resonance spectroscopy (ESR) and correlated with the presence of H. pylori. In all, 35% of the gastritis samples and 45% of the intestinal metaplasia samples were found to contain mutations in exons 5–8 of the p53 gene. Electron spin resonance spectroscopy analysis showed a significant increase in free radical levels in gastritis samples compared with normal, intestinal metaplasia and cancer samples, suggesting that free radicals present in gastritis may contribute to p53 mutations. There was no significant difference in free radical levels between the H. pylori-positive and -negative groups. However, a small subpopulation of the H. pylori-negative patients had much higher levels of free radicals. This suggests a more prominent role for other factors in ROS production.

Mutant p53 expression and apoptotic activity of Helicobacter pylori positive and negative gastritis in correlation with the presence of intestinal metaplasia

BACKGROUND

Mutation of the p53 gene is detectable in most cases of gastric cancer, as it is the most common genetic alteration in human malignancies. It is also well documented that Helicobacter pylori infection plays an important role in gastric carcinogenesis. There is still no clarification, however, concerning how genetic instability influences the homeostasis of gastric epithelium. We have studied the effect of H. pylori infection on apoptosis of the antral epithelium in the presence/absence of intestinal metaplasia and the expression of the p53 oncoprotein. The relationship between these two processes is analysed.

METHODS

Antral biopsies were taken from 36 patients who underwent routine upper endoscopy (17 men, 19 women, mean age 61.0 years). The biopsies were fixed in formalin and embedded in paraffin. Patients were classified into two histological groups: (1) as chronic gastritis without intestinal metaplasia (n = 19), and (2) chronic gastritis with intestinal metaplasia (n = 17). An immunohistochemical method was used to detect the expression of p53 oncoprotein, and the terminal transferase mediated dUTP nick end-labelling (TUNEL) method was used to detect apoptotic cells.

RESULTS

In the absence of intestinal metaplasia, both the apoptotic index (0.0272 +/- 0.011 vs 0.0128 +/- 0.006) and expresssion of p53 (35.55 +/- 31.16 vs 18.33 +/- 19.65) were significantly higher in H. pylori positive cases compared to H. pylori negative cases. In the presence of intestinal metaplasia, p53 expression was further increased (P < 0.05), but apoptosis was similar to that observed in H. pylori negative gastritis without intestinal metaplasia. In the presence of intestinal metaplasia, H. pylori infection did not influence apoptosis (0.013 +/- 0.004 vs 0.011 +/- 0.004), or p53 ratio (70.16 +/- 22.54 vs 68.50 +/- 28.96). In the sequence of gastritis-intestinal metaplasia the two indices show a close negative correlation (P < 0.05).

CONCLUSION

In the absence of intestinal metaplasia H. pylori infection increases both apoptotic activity and expression of p53 oncoprotein in the gastric mucosa. The lack of increased apoptosis with a higher p53 expression in the presence of intestinal metaplasia suggests an increased genetic instability and also may suggest that mutation of the p53 gene is an early step in the multistep process of gastric carcinogenesis.

TP53 and gastric carcinoma: a review

In this article, we survey the major p53 (TP53) alterations identified in gastric carcinomas and their precursors. These include p53 expression, mutations, and loss of heterozygosity (LOH). Not only are the various abnormalities summarized, but in addition there is a survey of the literature with respect to the impact of these changes on patient prognosis and treatment response. The majority of published studies involve the immunohistochemical detection of the protein. These use different antibodies, different detection techniques, and different methods of interpretation. Therefore not surprisingly, the results of many of the studies are contradictory with one another. Overall, however, it appears that p53 alterations occur early in the development of gastric carcinoma, being present even in the nonneoplastic mucosa and they increase in frequency as one progresses along the pathway of gastric carcinoma development. p53 immunoreactivity is seen in 17%-90.7% of invasive gastric carcinomas. p53 alterations occur much more commonly in proximal lesions than in distal ones, suggesting that the molecular events leading to the development of gastric carcinoma may be very different in proximal vs. distal tumors. p53 mutations occur in 0%-77% of gastric carcinomas. The mutations are distributed widely across the gene from exons 4-11 with hot spots of mutation at codons 175, 248, 273, 282, 245, and 213. G:C>A:T transitions at CpG sites are the commonest type of mutation. At least 60% of carcinomas with mutations also exhibit p53 LOH.

Molecular and cellular phenotypic profiles of gastric noninvasive neoplasia

According to the Padova international classification, 52 gastric noninvasive neoplasias (NIN) were classified as follows: 20 low-grade NIN (L-NIN); 9 high-grade NIN including suspicion for carcinoma without invasion (H-NIN); and 23 high-grade NIN including carcinoma without invasion (Ca-NIN). The molecular and cellular phenotypic profiles were investigated and compared. The APC gene was mutated in seven (35%) L-NIN, two (22%) H-NIN, and two (9%) Ca-NIN tumors; APC mutations were significantly more frequent in L-NIN compared with Ca-NIN tumors (p < 0.05). Mutations of the p53 gene were found in five (22%) Ca-NIN tumors but were not observed in L-NIN or H-NIN tumors (p < 0.05). Loss of heterozygosity involving at least one chromosomal locus was detected in 14 (61%) Ca-NIN tumors but was not detected in L-NIN or H-NIN tumors. High-frequency microsatellite instability (MSI-H) was detected in one (5%) L-NIN tumor and in six (26%) Ca-NIN tumors. The frequencies of loss of heterozygosity and MSI-H were significantly higher in Ca-NIN than in L-NIN or H-NIN tumors (p < 0.05). Nuclear accumulation of p53 protein was detected in no L-NIN tumors, 1 (11%) H-NIN tumor, and 10 (44%) Ca-NIN tumors (p < 0.01). All tumors with loss of hMLH1 expression exhibited MSI-H (p < 0.01). Cellular phenotypic analysis revealed that seven (35%) L-NIN tumors and one (4%) Ca-NIN tumor had complete-type intestinal metaplastic phenotype and that one (5%) L-NIN tumor and one (4%) Ca-NIN tumor had a gastric foveolar epithelial phenotype, whereas the remaining tumors exhibited an ordinary phenotype. Thus, the complete-type intestinal metaplastic phenotype was more characteristic of L-NIN tumors than of H-NIN or Ca-NIN tumors (p < 0.01). In summary, the Padova international classification correlated with both the molecular and cellular phenotypic profiles. In practice, p53 and hMLH1 immunohistochemistry discriminated Ca-NIN from L-NIN and H-NIN tumors.

Immunohistochemical study of p53, p21 and PCNA in pterygium

Since mutated p53 is one of the most frequent gene abnormalities in human cancer, we hypothesized that mutation of p53 may play an important role in growth and recurrence of pterygia, a dysplasia of the conjunctiva. Therefore, we compared pterygia of Japanese and Tunisian patients using antibodies against p53, p21 and proliferating cell nuclear antigen (PCNA). In Nagasaki, 21 pterygia of Japanese individuals were removed and in Gabes, 19 primary pterygia of Tunisian individuals. Positive staining of wild type p53 was not found in the Japanese pterygia, whereas 38.1% were positive for mutant p53, none were positive for p21 and 76.2% were positive for PCNA. The incidence of mutant p53-positive staining was 50.0% in males and 22.2% in females, which was statistically significant. In the 19 Tunisian patients, positive staining of wild type p53 was not found, whereas 36.8% were positive for mutant p53, 0% for p21 and 63.1% for PCNA. Differences between Japanese patients and Tunisian patients were not significant. There were 2 types of pterygium. One type did not show mutant p53 and the other showed mutant p53 caused by ultraviolet light. However, damage caused by p53-dependent programmed cell death of pterygium cells may lead to mutations in other genes which may allow the progressive multistep development of limbal tumors. It is possible that mutant p53-positive pterygia can develop into limbal tumors.

Diagnostic and prognostic tumor markers in the gastrointestinal tract

The gastrointestinal tract is the most common site of malignancies of any anatomic system in the body. An early detection of primary tumors of the bowel, pancreas, liver, stomach, and esophagus is often difficult in asymptomatic patients and for this reason these tumors are often detected at a relatively advanced stage, when symptoms lead to a diagnostic evaluation. Furthermore, gastrointestinal tract tumors have an extremely variable prognosis; thus, the identification of new prognostic parameters may be useful for selecting patients to more tailored therapies. In this work, the main molecular, genetic, tissular, and circulating tumor markers proposed for diagnosis and prognosis of gastrointestinal malignancies are reviewed and discussed.

Expressions of cell-cycle regulatory gene products in conventional gastric adenomas: possible immunohistochemical markers of malignant transformation

In 54 lesions of gastric adenomas consisting of 31 low-grade adenomas (LGAs) and 23 high-grade adenomas (HGAs), 28 intramucosal carcinomas (IMCs), and 23 carcinomas invading the submucosa (SMCs), the expression of cell-cycle regulatory gene products (p53, p21/waf1, p27/kip1, and Ki-67) was studied using immunohistochemical techniques. Several lesions were also analyzed by the fluorescence in situ hybridization method. The overexpression of p53 was found in no LGAs and in 9% of HGAs, whereas a considerable number of cases showed an overexpression in IMCs (39%) and SMCs (43%). A reduced expression of p21/waf1 was present in only 4% of HGAs. Superficial eccentric positivity was present in all LGAs and 74% of HGAs, whereas it was present in 46% of IMCs and 4% of SMCs. P53-positive and p21/waf1-negative lesions, which were supposed to have a mutated p53 gene, were observed in no LGAs, in 4% of HGAs, in 11% of IMCs, and in 26% of SMCs. The expression of cyclin E was more frequently present in carcinomas than in adenomas. However, no high expression of cyclin E was observed among the adenomas. A reduced expression of p27/kip1 was encountered more frequently in carcinoma than adenoma. By a semiquantitative evaluation comparing adenoma and carcinoma in the same stomach, the increased degrees of both p21/waf1 and cyclin E were highlighted. A chromosome gain was detected among 7% of the adenomas and 85% of the carcinomas. In conclusion, the expressions of p53, p21/waf1, p27/kip1, and cyclin E were considered to be of great value for estimating the dysplastic progression of gastric adenomas. Especially, various aspects of protein expression, including its distribution and semiquantitative evaluation of positive cells, and a combined analysis with several proteins, may thus be useful as possible markers of dysplastic evolution in gastric adenomas.

P53-protein accumulation and MDM2-protein overexpression in gastric carcinomas. No apparent correlation with survival

Forty-five cases of primary gastric carcinoma were investigated immunohistochemically for p53 protein accumulation and MDM2 protein overexpression. The results were correlated with pathological and clinical data. The incidence of p53 accumulation was 12 of 45 (26.7%) cases and that of MDM2 expression was 30 of 45 (66.7%). Eighteen of 45 (40%) cases showed MDM2 overexpression without p53 accumulation. All of the 12 p53-positive cases exhibited a co-expression of MDM2. Accumulation of p53 and MDM2 overexpression correlated with the grade of malignancy. MDM2 expression occurred more often in intestinal carcinomas than in the diffuse types. No correlation was found between p53 accumulation and the histopathology of gastric cancer. p53 accumulation and MDM2 overexpression did not correlate with tumor size, nodal status, presence of metastases, age or survival. p53 alteration, which seems to be a late step in gastric carcinogenesis, is a marker of higher grade tumors. MDM2 functions as a cofactor of p53 in late gastric carcinogenesis. An independent role of this oncoprotein in gastric carcinogenesis also seems possible. Neither p53 nor MDM2 is a useful prognostic indicator.

p21(Waf1/Cip1) expression and the p53/MDM2 feedback loop in gastric carcinogenesis

Data are non-existent regarding coincidental alterations in the expression of p53 and its downstream target genes MDM2 and p21(Waf1/Cip1) in gastric carcinogenesis. An immunohistochemical study was therefore performed to examine the interrelationships of p53, MDM2, and p21(Waf1/Cip1) expression in a series of Caucasian early gastric carcinomas and precursor lesions. In normal gastric mucosa, chronic gastritis, and intestinal metaplasia, the surface cells expressed p21(Waf1/Cip1) in the absence of detectable nuclear p53 and MDM2 protein. Nuclear p53 protein accumulation was found in 60 per cent of the carcinomas, with significant differences in staining characteristics between the Lauren types in the absence of detectable MDM2 protein ( p< 0.005). Nearly 80 per cent of the carcinomas expressed p21(Waf1/Cip1), irrespective of Lauren type. Stratification of the carcinomas according to histological grade and growth pattern did not result in significant differences in p53 and p21(Waf1/Cip1) expression. Finally, no significant correlation was found between overall p53 and p21(Waf1/Cip1) expression in early gastric carcinomas. It is concluded that p21(Waf1/Cip1) expression in the non-neoplastic mucosa most likely relates to cell senescence and/or terminal differentiation, perhaps even in a p53-independent manner. In view of p53/MDM2 homeostasis, the differences in p53 staining characteristics between intestinal and diffuse-type carcinomas probably result, at least in part, from a difference in the prevalence of p53 gene mutations. Moreover, p53-independent induction of p21(Waf1/Cip1) expression apparently occurs in a considerable proportion of early carcinomas. Finally, in contrast to other carcinomas, p21(Waf1/Cip1) expression is not significantly correlated with histological grade in gastric carcinomas, suggesting possible defects downstream of p21(Waf1/Cip1) as an underlying cause for this apparent discrepancy.

p53 immunoreactivity in endometrial metaplasia with dysfunctional uterine bleeding

AIM

Overexpression of p53 has been reported in endometrial carcinomas, especially in uterine papillary serous carcinoma (UPSC), to correlate with worse prognosis. Endometrial metaplasia is commonly encountered in patients with dysfunctional uterine bleeding (DUB) and may on occasion be difficult to distinguish from atypical endometrial hyperplasia or carcinoma on biopsies. The present study was initiated in the belief that metaplastic tissue might not show overexpression of p53 and would thus help to distinguish it from carcinomas of non-endometrioid histology.

METHODS AND RESULTS

Paraffin-embedded tissue of endometrial biopsies with papillary metaplasia (22 cases), tubal metaplasia (five cases) and eosinophilic meta-plasia (seven cases) from patients with DUB were immunostained for p53 immunoreactivity. No evidence of hyperplasia was noted in any of the cases selected for the study. Twenty-eight cases of UPSC were included for comparison. Our study showed p53 overexpression in 25 of 28 (89%) UPSC. Weak and heterogeneous p53 immunoreactivity was present in 10 of 22 (45%) papillary metaplasias, four of five (80%) tubal metaplasias and four of seven (57%) eosinophilic metaplasias. Follow-up of 16-45 (median 32) months was unremarkable except for one patient with eosinophilic metaplasia who had simple endometrial hyperplasia in subsequent biopsy.

CONCLUSIONS

The presence of weak and heterogeneous p53 immunoreactivity in metaplastic endometrium is unexpected and might be a consequence of DNA damage. Intense, diffuse and homogeneous p53 staining favours carcinoma.

Field cancerization, clonality, and epithelial stem cells: the spread of mutated clones in epithelial sheets

There has been considerable debate about the origin of human tumours, whether they arise from a single cell and are clonal populations or whether there needs to be some sort of co-operativity between cells for the neoplastic process to begin. Current theories subscribe to the clonal view, where a series of mutations in one cell begins a process of selection and clonal evolution leading to the development of the malignant phenotype. This review approaches this problem by asking how mutated clones, once established, spread through tissues before becoming overtly invasive. While there is substantial evidence in favour of independent origins of each tumour from a unique mutated clone, there are instances where such clones expand and remain cohesive, often involving a large area of tissue. The main example is the movement of mutated clonal crypts through the colorectal epithelium, by the process of crypt fission. In passing, the clonal architecture of early, pre-invasive lesions is examined, often with some surprising results.

Presence of high-level DNA copy number gains in gastric carcinoma and severely dysplastic adenomas but not in moderately dysplastic adenomas

Our aim was to investigate the presence of DNA copy number changes in gastric adenomas and to identify the changes that may play a role in gastric carcinogenesis. DNA copy number changes in 16 patients with gastric adenoma and in 22 tumors from patients with intestinal type gastric carcinomas were studied by using comparative genomic hybridization. DNA copy number changes were found in 44% of the adenoma cases and in 86% of the intestinal type gastric carcinomas. On average, gains were more common than losses (0.9 vs. 0.5 in adenomas and 4.1 vs. 1.8 in carcinomas). In adenomas, the most common gains involved chromosome 8 in 3 cases, and gain of chromosome 7 and 20q was detected in 2 cases. The most frequent losses were observed at 5q (three times). Only adenomas with severe dysplasia showed high-level amplifications that were detected at chromosome 13, 17cen-q22, and 20q12-ter. In gastric cancer, the most common gains were detected at 20q (55%), 17q12-q21 (41%), and 8q (41%), and the most common losses were detected at 18q (41%) and 4q (32%). High-level amplifications were observed at 20q (3 tumors), 17cen-q21 (3 tumors), 2p (1 tumor), and 18q (1 tumor). These findings suggest that the progression of dysplasia is associated with higher levels of DNA copy number increase (e.g., the gains at 17q and 20q), which were typically observed in the intestinal type gastric cancer. Furthermore, the results support the hypothesis that adenoma precedes cancer.

Overexpression of p53 predicts shorter survival in diffuse type gastric cancer

BACKGROUND

It has been suggested that p53 plays an important part in gastric carcinogenesis but the data remain inconclusive.

METHODS

Alteration of the tumour suppressor gene p53 was prospectively investigated by immunohistochemistry in 168 primary gastric cancers.

RESULTS

Positive staining, indicative of gene mutations, was detected in 34 tumours (20.2 per cent). No correlation was observed between expression of p53 and various clinicopathological factors, including age, sex, tumour site, gross type, tumour size, depth of invasion, lymph node metastases, distant metastases, and tumour node metastasis stage. However, p53 overexpression was different between intestinal and diffuse type gastric cancer. Survival analysis revealed a significant survival disadvantage of p53 expression in diffuse type gastric cancer (P=0.039) but not in the intestinal type. Multivariate analysis of all 168 patients revealed that independent predictors of recurrent disease included age, invasion depth and nodal involvement but not p53 expression.

CONCLUSION

The presence of p53 overexpression may identify a subset of more aggressive tumours with a poor prognosis in diffuse type gastric cancer.

Proliferative epithelial changes in ectopic gastric mucosa of Meckel's diverticula

Twenty-one Meckel's diverticula containing an adequate amount of assessable heterotopic gastric mucosa were investigated for epithelial changes. Marked or moderate foveolar hyperplasia was present in 52% and 29% of the cases, respectively. Four cases displayed an excessive epithelial proliferation indefinite for dysplasia. It is pointed out that reflux type gastritis or gastropathy, which is the most common lesion in the ectopic gastric mucosa of Meckel's diverticulum, can be associated with the same confusing epithelial proliferation as reflux gastritis in the stomach, but these lesions are best regarded as representing atypia of repair. Distinguishing features from dysplasia are maturation towards the surface, lack of hyperchromatism and abscence of atypical mitoses. Negative p53 immunostaining and localization of the Ki-67 positivity to the expanded neck region could be additive clues that can help to classify lesions indefinite for dysplasia as negative for dysplasia. On the basis of the similarities of the ectopic and ortotopic gastric mucosa, it is suggested that these additive clues previously used in other parts of the digestive tract could also apply for the stomach.

Capsaicin can alter the expression of tumor forming-related genes which might be followed by induction of apoptosis of a Korean stomach cancer cell line, SNU-1

Capsaicin (CAP) has been known to inhibit some tumor development in vivo (J.J. Jang, S.H. Kim, T.K. Yun, Inhibitory effect of capsaicin on mouse lung tumor development, in vivo, J. Korean Med. Sci. 3 (1989) 49-53; J.J. Jang, K.J. Cho, Y.S. Lee, J.H. Bae, Different modifying responses of capsaicin in a wide-spectrum initiation model of F344 rat, J. Korean Med. 6 (1991) 31-36) [1,2] even though its mechanism of action is not well understood. The objectives of this study were to examine the effect of CAP on expression of tumor forming-related genes in a Korean stomach tumor cell, SNU-1. We used slot blot hybridization to investigate its effect on a wide spectrum of proto-oncogenes. It was found that CAP enhanced the transcripts of two proto-oncogenes (c-myc and c-Ha-ras) and tumor suppressor gene p53. While a low concentration of CAP (0.01 microM) did not significantly increase the level of p53 transcript in SNU-1, it did increase it by a factor of 3.5 at a 10 microM dose of CAP. Consequently, SNU-1 cells are sensitive to CAP in the overexpression of tumor suppressor gene, p53 and proto-oncogenes, c-myc and c-Ha-ras, but not those of c-erbB-2, c-jun and bcl-2 genes. Both cell death and DNA fragmentation were shown in SNU-1 cells with treatment of CAP. Our results suggest that CAP induces apoptotic cell death in human gastric cancer cells (SNU-1) in vitro which may be possibly mediated by the overexpression of p53 and/or c-myc genes. Because cell suicide is arguably the most potent natural defense against cancer, the correlation between the induction of apoptosis and the change of tumor forming-related gene expression after CAP treatment should be further studied in detail.

Comparison of p53 expression in proximal and distal gastric cancer: histopathologic correlation and prognostic significance

BACKGROUND

The overexpression of p53 has been found to be correlated with prognosis of some carcinomas, including gastric cancer, but no studies have reported on its relationship to the location of gastric cancer. In the present study, we compared the p53 expression of proximal and distal gastric cancer concerning histopathology and prognosis.

METHODS

A total of 170 tumors in the patients with proximal (80 cases) and distal (90 cases) gastric cancer were studied by immunohistochemical methods.

RESULTS

p53 immunopositivity was detected in 28.8% of all tumors. The p53-positive expression in proximal gastric cancer was higher than in distal gastric cancer (38.8% vs. 20.0%, p < 0.05). A 5-year survival analysis showed that there is no significant difference between tumors that are p53 positive and p53 negative. No correlation was found between p53 expression and histopathology of gastric cancer.

CONCLUSION

p53 nuclear staining is not useful as a prognostic indicator or as a parameter in gastric cancer.

p53 protein immunoexpression in esophageal squamous cell carcinoma and adjacent epithelium

BACKGROUND

Immunoreactivity for p53 tumor suppressor gene product is commonly found in human malignancies and some premalignant lesions, but its role in cancer development and its value as a marker of tumor biologic behavior is still unclear.

OBJECTIVES

This study was undertaken to assess p53 immunoexpression in esophageal squamous cell carcinoma and attempts to determine its correlation with morphological features associated with tumor behavior.

METHODS

Immunohistochemical study was performed on archival paraffin-embedded tissue of 37 esophageal squamous cell carcinomas and respective adjacent mucosa.

RESULTS

Twenty-one tumors (56.8%) demonstrated specific staining for p53. Sixteen areas of dysplasia were present in 14 out of the 35 cases. p53 positivity was found in one low-grade dysplasia and in six high-grade dysplasias. By univariate analysis, p53 immunoexpression correlated positively with local invasion (P = 0.01) and perineural spread (P = 0.04). Multivariate analysis with logistic regression showed that tumor invasion was the only factor that discriminated between p53 positive and p53 negative cases (OR: 15.6, P < 0.02). No relationship was found between p53 expression and tumor grade, DNA nuclear ploidy, and S-phase fraction.

CONCLUSIONS

These data suggest that p53 dysfunction may be implicated in early, preinvasive, stages of esophageal cancer as well as in the tumor progression related to a more invasive phenotype.

Numerical aberration and point mutation of p53 gene in human gastric intestinal metaplasia and well-differentiated adenocarcinoma: analysis by fluorescence in situ hybridization (FISH) and PCR-SSCP

This study examined p53 gene alterations in human gastric mucosa, intestinal metaplasia and well-differentiated (cohesive type) adenocarcinomas to clarify to the role of the p53 gene in gastric tumorigenesis by means of fluorescence in situ hybridization (FISH), polymerase-chain-reaction-single-strand-conformation polymorphism (PCR-SSCP) and immunohistochemistry. Gene alterations were compared with numerical changes of chromosome 17. Samples were obtained from 31 surgically resected stomachs affected with gastric cancer. There was no nuclear p53 protein in cells from normal gastric mucosa. Among 23 specimens of intestinal metaplasia, cells with p53 protein were variably detected in 5 incomplete metaplasias (colonic type). A histological study revealed a mildly dysplastic appearance. PCR-SSCP identified p53-gene mutation in exons 5 and 8 in 2 of the 5 samples. Numerical aberrations of chromosome 17 and the p53 gene were undetectable both in normal mucosa and in intestinal metaplasia. Variable numbers of tumor cells contained p53 protein in 13 (54%) of 24 carcinomas, and PCR-SSCP revealed abnormal bands in 5 of them. Mutations were detected in exons 5, 7, 7, 7 and 8. FISH analysis demonstrated that 6 carcinomas emitted 3 or 4 signals for chromosome 17, and 7 gave one signal for the p53 gene in over 20% of the cells. Ten (77%) of 13 carcinomas examined by FISH appeared to show a p53-gene deletion.

Prognostic influence of p53 expression in gastric cancer

The presence of the nuclear phosphoprotein p53 was investigated in a series of 120 consecutive gastric carcinomas. This immunohistochemical study on formalin-fixed, paraffin-embedded material found p53 expression in 43 per cent (n = 51) of carcinomas using a monoclonal antibody (DO-1), whereas no immunoreactivity for p53 was present in tumour-associated non-neoplastic gastric mucosa or tumour stroma. There was no statistically significant correlation with known prognostic parameters such as extent of tumour growth (pT state), nodal involvement (pN state), or tumour grade. The same applied for association with patient age and sex or pathological parameters such as tumour size, localization, or growth pattern according to histological classification. Kaplan-Meier analysis revealed marginal statistically significant differences in survival times between patients with p53-positive tumours with more than 35 per cent of p53-positive tumour cells and those with less than 35 per cent of p53-positive tumour cells or p53-negative tumours (P = 0.04). However, by multivariate analysis, p53 immunoreactivity did not turn out as an independent prognostic parameter. p53 expression can easily be detected in a variety of human malignancies including gastric cancer by immunohistochemical methods, but its prognostic significance and possible role as an independent marker of poor prognosis still have to be confirmed by further studies.

Tumor genes and their proteins in cytologic and surgical specimens: relevance and detection systems

Oncogenesis is the consequence of a series of genetic alterations that allow unrestrained cellular growth, tissue invasion, and eventual metastases. Tumor-related genes can be classified into functional categories. Proto-oncogenes/oncogenes have a stimulatory role in cell growth, and the inactivation of cancer-suppressor genes/antioncogenes results in the loss of cell cycle regulation. More recently, three other groups of tumor-related genes have been recognized. They include the antiapoptosis genes which protect from programmed cell death, the antimetastasis genes, and multidrug resistance genes. Besides aiding in tumor diagnosis, the detection of such tumor-associated genes and their products allows the identification of individuals with an inherited predisposition to neoplastic growths, and the overexpression of many of these oncogene products has been shown to be a potential marker of tumor behavior and a predictor of treatment outcome and response. The ability to utilize DNA and RNA probes for nucleic acid hybridization and polymerase chain reaction procedures in cell and tissue preparations of solid tumors and lymphoid proliferations expands and complements the information provided by immunohistochemical techniques. These probes allow direct visualization and correlation of specific genes and their protein products with cytomorphologic features, and form a powerful addition to the armamentarium of the cytopathologist and surgical pathologist.

Evaluation of overexpression of p53 tumor suppressor protein in superficial and invasive transitional cell bladder cancer: comparison with DNA ploidy

OBJECTIVES

p53 tumor suppressor gene is considered to play a significant role in carcinogenesis. Mutations in the p53 are the most frequent genetic abnormalities encountered in human malignancies. Our aim was to investigate the expression of p53 oncoprotein in superficial and invasive transitional cell bladder cancer (TCC) as well as its correlation with established prognostic factors, such as histologic grade, tumor stage, DNA content, and survival.

METHODS

Forty-five patients with superficial TCC (Ta-T1) and 42 with invasive TCC (T2-T4) were included in our study. Material from transurethral biopsy was examined using an immunohistochemical method and the monoclonal antibody Pab 1801.

RESULTS

p53 tumor suppressor protein was overexpressed in 48.3% of TCC cases and more frequently in invasive than superficial TCCs (P = 0.03) and undetectable in the tumor adjacent to normal tissue. p53 positivity was related to the degree of differentiation and with the stage of the disease of invasive TCCs (P = 0.03 and P = 0.004, respectively), whereas no statistical significance was documented for superficial TCCs. Moreover, p53 overexpression demonstrated a statistical significance with DNA ploidy in superficial Ta-T1 tumors (P = 0.04) and was suggestive in invasive T2-T4 tumors (P = 0.08). There was no correlation of recurrence related to p53-positive superficial tumors (P = 0.29). Patients with p53-positive invasive TCCs showed statistically significant worse survival (P = 0.007), but in multivariate analysis, p53 positivity is not independently related to poor overall survival (P = 0.30). When we combined ploidy and p53 status, we realized that the subset of patients with aneuploidy and p53 positivity had the worst prognosis (P = 0.008).

CONCLUSIONS

The results suggest the involvement of p53 protein as a late event in bladder carcinogenesis. p53 does not seem to be a prognostic marker for recurrences of superficial tumors and is not independently related to survival. The aneuploidy of tumors correlates with the p53 positivity in bladder cancer. The combined expression of aneuploidy and p53 positivity in invasive tumors has strong association with the survival of patients.

Cell proliferation patterns and p53 expression in gastric dysplasia

Gastric dysplasia (high-grade, HGD, and low-grade, LGD) and normal mucosa were tested for anti-p53, anti-Ki-67 and anti-PCNA monoclonal antibodies on paraffin sections, and for relative AgNOR area and number on semithin Epon-Araldite sections. The proliferative compartment in normal mucosa was restricted to the middle layer corresponding to the neck-isthmus region. In LGD and HGD there was an expansion of this compartment to the lower and upper layers of mucosa, and in HGD in particular to the upper layer. p53 was always negative in LGD as well as in normal mucosa, while it was positive in 34 out of 51 cases of HGD. The most discriminant variables between LGD and HGD were relative AgNOR area and the percentages of MIB-1, p53 and PCNA. In p53-positive HGD the highest percentages of PCNA and MIB-1 were in the middle and upper layers (PCNA) or the upper layer (MIB-1), while in p53-negative HGD cases cell proliferation was maximal in the middle layer, although also present in the upper layer. The majority of cases of LGD did not demonstrate cell proliferation in the upper layer, but 5 cases behaved similarly to the p53-negative HGD cases. No significant correlations were found among percentages of MIB-1 and of PCNA and relative AgNOR area and number.

Expression of p53 and flow cytometric DNA analysis of isolated neoplastic glands of the stomach: an application of the gland isolation method

The expression of p53 was studied immunohistochemically in combination with the DNA ploidy pattern by gland isolation in 97 alcohol-fixed gastric lesions. A polyclonal antibody, CM-1, was applied to the paraffin-embedded sections in this study. Overexpression of the p53 protein was found in 73.2% of 41 well or moderately differentiated gastric carcinomas and 52.2% of 23 cases with poor differentiation (P < 0.05). Immunoreactivity of p53 was also detected in isolated cancerous glands. No p53 immunoreactivity was detected in benign gastric lesions including adenomas, hyperplastic polyps and regions of intestinal metaplasia. In addition, flow cytometric DNA analysis was performed on isolated glandular epithelium adjacent to the portions used for immunostaining. DNA aneuploidy (DA) was detected in 85.7% of the well or moderately differentiated carcinomas and 42.9% of those with poor differentiation (P < 0.05). There was a positive correlation between DA, p53 positivity and the presence of regional lymph node metastasis, but not with other clinicopathological variables. In spite of the limited applicability of this method to poorly differentiated gastric cancer, we found that immunostaining and flow cytometry in combination with the gland isolation method facilitates analysis of gastric carcinogenesis.

Chronology of p53 protein accumulation in gastric carcinogenesis

p53 Protein accumulation in early gastric carcinoma was studied in relation to the histological type (Lauren classification) and the type of growth pattern, including the chronology of p53 protein accumulation during carcinogenesis. Forty five, paraffin embedded gastrectomy specimens from early carcinomas were examined for the presence of chronic atrophic gastritis, subtypes of intestinal metaplasia, and dysplasia. The Lauren type and the type of growth pattern were reassessed for all early carcinomas. p53 Protein accumulation was examined using the monoclonal antibody DO-7. Complete absence of p53 protein accumulation was observed in normal gastric mucosa, chronic atrophic gastritis, and intestinal metaplasia, irrespective of subtype. In gastric dysplasia (one mild, two moderate, and one severe), only severe dysplasia was p53 positive. Intestinal type (n = 20) and diffuse type early gastric carcinomas (n = 25) were p53 positive in 70% and 52% of cases, respectively. Both tumour types differed significantly in the percentage of p53 positive tumour cells per tumour (p < 0.01) and in staining intensity (p < 0.05). No significant difference in p53 protein accumulation was found between early carcinomas with different types of growth pattern. It is concluded that p53 protein accumulation--usually reflecting missense p53 gene mutation--seems to be a late event in gastric carcinogenesis. Moreover, it is suggested that missense p53 gene mutation occurs in a final pathway common to both intestinal and diffuse type of early gastric carcinoma. Finally, the types of growth pattern do not seem to differ in p53 protein accumulation.

TP53 gene mutations in gastric carcinoma detected by polymerase chain reaction/single-strand conformation polymorphism analysis of archival material

TP53 gene mutations, one of the most common alterations described in human tumors, have also been detected in gastric carcinoma, and shown to occur rather late in disease progression. A better assessment of the prognostic value of TP53 gene mutations can be obtained by examining archival material, as this allows stored cases with well-defined histories to be monitored. We performed immunohistochemical and polymerase chain reaction/single-strand conformation polymorphism (PCR-SSCP) analyses of formalin-fixed paraffin-embedded material from nine selected cases of gastric carcinoma at different pathological stages. PCR-SSCP analysis of TP53 exons 5-8 detected missense point mutations in two out of five immunostain(PAb1801)-positive tumors, and a deletion (allowing for a premature stop codon) in one of the remaining four immunostain-negative tumors. Thus, PCR-SSCP analysis represents a feasible strategy for the detection of TP53 alterations in archival material of gastric carcinoma cases.