Ki-ras codon 12 point mutation and p53 mutation in pancreatic diseases.

BACKGROUND/AIMS: The Ki-ras gene located at 12p, encodes the GTP binding protein involving the signal transduction system and concerns cell proliferation and differentiation. METHODOLOGY: Pancreatic tissues were obtained from 37 patients with various pancreatic diseases. Ki-ras codon 12 point mutation and p53 (exon 5-8) mutation were examined in 3 patients with chronic pancreatitis, 9 mucinous adenoma of the pancreas (2 with mucinous cystadenoma and 7 with intraductal papillary-mucinous adenoma), 22 pancreatic ductal carcinoma, and 3 serous cystadenoma. RESULTS: On usual pancreatic exocrine ductal lesions, Ki-ras point mutation was evident in 0% (0/3) of chronic pancreatitis, in 56% (5/9) of mucinous adenoma, and in 57% (12/21) of ductal carcinoma, the mutation being located in the second letter in 18 and in the 1st letter in 2. One Ki-ras codon 12 positive pancreatic cancer showed Ki-ras codon 12 point mutation in the surrounding pancreas (2nd letter mutation in both areas). p53 mutation was present in 0% (0/1) of chronic pancreatitis, in 0% (0/8) of mucinous adenoma, while it was evident in 29% (6/21) of pancreatic ductal carcinoma, the mutation being situated in exon 5 in 3, in exon 6 in 1, and in exon 7 in 2. In 3 patients with serous cystadenoma, there was no mutation in Ki-ras codon 12 or p53 (exon 5-8). CONCLUSIONS: These findings suggest that Ki-ras point mutation is involved in the early events of pancreatic ductal carcinoma, while p53 mutation is intricated in the late phase of pancreatic ductal carcinogenesis and the histogenesis of serous cystadenoma is different from that of pancreatic exocrine ductal lesions including mucinous adenoma and ductal carcinoma.     

Analysis of K-ras codon 12 mutations and p53 overexpression in colorectal nodule-aggregating tumors

BACKGROUND AND AIMS: Morphologically, colorectal nodule-aggregating tumors are quite different from polypoid-type colorectal tumors that develop via the adenoma-carcinoma sequence. Although polypoid-type colorectal tumors are well known to have a high incidence of K-ras gene mutation and p53 overexpression, colorectal nodule-aggregating tumors have not been examined in terms of genetic changes and clinicopathological features. In the present study, therefore, we analysed the clinicopathological features, genetic changes in K-ras codon 12, and p53 overexpression in colorectal nodule-aggregating tumors. METHODS: A total of 18 colorectal nodule-aggregating tumors were surgically resected and then analysed clinicopathologically. Immunohistochemistry and polymerase chain reaction-single stranded conformational polymorphism were performed to analyse p53 abnormalities in the tumors. K-ras codon 12 mutations were screened out by the polymerase chain reaction-restriction fragment length polymorphism method and analysed by fluorescence direct sequencing. RESULTS: p53 overexpression was observed in six lesions (33%). p53-overexpressing cells were observed in parts of carcinoma or adenoma showing high-grade atypia. Four of the 10 (40%) samples had a p53 gene mutation. Nine of the 18 (50%) samples had a K-ras codon 12 point mutation. In eight cases (89%), the mutations of the K-ras codon 12 were of the same type: GGT (glycine) to GTT (valine). CONCLUSIONS: The colorectal nodule-aggregating tumor has distinctive characteristics showing a morphological phenotype of the superficial-type tumors and genotype of the polypoid tumors in terms of K-ras gene mutation and p53 overexpression.     

Ki-ras point mutation in codon 12 and expression ofp53 in mucin-producing tumor of the pancreas

Mucin-producing tumors (MPTs) of the pancreas show a variety of clinical characteristics, including massive production of mucin in the pancreatic duct, dilatation of the main pancreatic duct, and a better prognosis than common invasive ductal carcinoma (IDC). These characteristics suggest that MPTs and IDCs have different cytomolecular backgrounds. The present study was designed to assess the differences in cytomolecular background between MPTs and IDCs, especially the differences in Ki-ras point mutation (PM) and wild and mutant typep53 expression. Cytomolecular backgrounds were compared in a 13 MPTs [8 carcinomas (MPCas) and 5 benign tumors (MPBTs)] and 36 IDCs. Cytomolecular studies included the evaluation of Ki-ras PM and the expression of Ki-ras p21, wild-typep53 (w-p53), and mutant-typep53 (m-p53). Ki-ras PM was assessed by the allele-specific oligonucleotide dot blot hybridization method, and the expression of p21 andp53 was assessed by an immunohistochemical staining method with monoclonal antibodies. Ki-ras PM was seen in 97% of IDCs and in 77% of MPTs (100% of MPCas and 40% of MPBTs), and MPBTs showed a significantly lower incidence of Ki-ras PM (versus IDC,P < 0.01). Guanine-Guanine-Thymine (GGT) to Guanine-Adenine-Thymine (GAT) mutation was seen in 55% of IDCs and 62% MPTs (87% of MPCas and 20% of MPBTs), and MPCas showed a significantly higher incidence of percent GAT mutation (versus IDC,P < 0.05). Ki-ras p21 was expressed in 43% of IDCs and in 31 % of MPTs (50% of MPCas and 20% of MPBTs). w-p53 and m-p53 were expressed in 51 % and 78% of IDCs and in 54% and 62% of MPTs (38% and 63% of MPCas and 20% and 60% of MPBTs), respectively. In MPBTs, hyperplasias showed higher rates of p21, w-p53, and m-p53 expression than cystadenomas. The study suggested that GAT mutation may be involved in the tumorigenesis of MPTs. It is suggested that MPBTs, especially hyperplasias, may be classified as low-grade malignancies like MPCas.     

p53 mutations and codon 213 polymorphism of p53 in lung cancers of former uranium miners

Purpose: There is a high prevalence of G→T transversions of p53 in lung cancers of smokers. One study has reported a special “hotspot” mutation at codon 249 of p53 in lung cancers of former uranium miners. The aim of our study was to look for mutational spectra of p53 in former German uranium miners with lung cancers. Methods: We investigated 16 patients with lung cancer who had worked as uranium miners in Germany and 13 lung cancer patients without a mining history of the same region. By means of the polymerase chain reaction and sequencing we looked for mutations in exons 5–7 of the p53 gene. Results: We could not find any suggestion of hotspot mutations. The only G→T mutation in former uranium miners was detected in the only nonsmoker. In 3 patients (19% of the total) we found a codon 213/3 polymorphism. Conclusions: The results indicate that G → T transversions do not seem to be very common mutations in p53 in lung cancers probably caused by radiation. Therefore, p53 may be mutated early in lung cancer development if radiation exposure is a critical factor in carcinogenesis. In accordance with studies of thyroid cancer patients in the Chernobyl region, our results may indicate an overrepresentation of codon 213/3 polymorphism in p53 in radiation-caused cancers. Received: 24 September 1998 / Accepted: 16 December 1999     

Telomerase activity, P53 mutation and Ki-ras codon 12 point mutation of the peripheral blood in patients with hepato pancreato biliary diseases

Background

With progress in molecular biology, the presence of telomerase activity, P53 mutation and Ki-ras codon 12 point mutation has been reported in malignant tumours of the liver, pancreas and biliary tree. The purpose of this paper is to clarify the clinical implications of finding these three biomarkers in the peripheral blood of affected patients.

Methods

Telomerase activity, P53 mutation, and Ki-ras codon 12 point mutation in the peripheral blood were examined among 86 patients with hepato pancreato biliary disease, both benign and malignant, and the results were compared with clinical findings.

Results

Of 20 patients with benign conditions, only one patient with intraductal papillary adenoma showing severe dysplasia exhibited a biomarker (telomerase activity) in the peripheral blood. In total, there were 66 patients with various HPB carcinomas. Of 56 cancer patients studied pre-operatively, 16 were positive for more than one biomarker, 13 were positive for telomerase activity, 4 for P53 mutation (three at exon 7 and another at exon 8), and 2 for Kiras codon 12 point mutation (both in the second letter). Twelve of the 16 biomarker-postiive patients had stage IV disease as opposed to 23 of 40 biomarker-negative patients. The resectability rate of the cancer was 38% in positive patients and 50% in negative patients. The one-year survival rate after resection was zero in positive patients and 15% in negative patients, but the difference was not significant (P=0.65). Of 32 patients with liver metastasis at the time of the molecular examination, eight were positive and 24 negative. Of 34 patients without liver metastasis, nine were positive and 25 negative. The development of subsequent liver metastases in those without them at the start was not significantly different in those with and without biomarkers (56 vs 36%: P=0.31).

Conclusions

The three novel biomarkers of the peripheral blood seemed to be of little value for screening of early malignant HPB neoplasms but may help to predict liver metastasis.     

Detection of Ki-ras and p53 gene mutations in tissue and pancreatic juice from pancreatic adenocarcinomas

Pancreatic carcinomas have a high incidence of Ki-ras mutations, and the genetic change is thought to occur at an early stage in the carcinogenesis. The aim of this study was to evaluate the usefulness of detecting genetic mutations in pure pancreatic juice (PPJ). DNA was extracted from tissue specimens of pancreatic carcinomas and from cells in PPJ, and subjected to polymerase chain reaction-single-strand conformation polymorphism analysis. Two types of mobility shifts that indicate Ki-ras mutations were observed in 13 of the 20 (65%) tissue specimens obtained by operation or autopsy. Ten of 15 specimens (67%) of PPJ collected from patients with pancreatic carcinomas showed two types of mobility shifts. Conventional imaging techniques did not show two in 10 of these patients. PPJ from patients with non-cancerous pancreatic diseases showed no Ki-ras mutations. The p53 tumor suppressor gene, examined by PCR-SSCP analysis, was mutated in 8 of the 20 tissue specimens obtained by operation or autopsy (40%). The detection of Ki-ras and p53 mutations in PPJ could be useful for the early diagnosis of pancreatic carcinomas, especially for neoplastic lesions of the intraductal type. (Received Jan. 29, 1997; accepted Sept. 26, 1997)     

p53 codon 72 polymorphism in patients affected with ulcerative colitis

Background The p53 tumor suppressor protein plays a fundamental role in maintaining genomic integrity through its ability to arrest the cell cycle in G1 and induce apoptosis. The proapoptotic activity of p53 seems to be strictly related to proline-rich regions, homologous to the SH3 binding domain. In the literature, reported data suggest a role for polymorphism at codon 72 of p53 in the predisposition to neoplastic transformation, although the results are still controversial. In this study, we investigated Arg72Pro polymorphism of p53 and related this polymorphism to clinical parameters in patients affected with ulcerative colitis (UC). Methods We studied 243 consecutive outpatients affected with well-established UC. The control group comprised 142 healthy blood donors, with age and sex comparable to those of the patients. Results p53 Pro/Pro was significantly related to the clinical course and duration of disease (odds ratio, 55.8 and 8.8, respectively). Nineteen of 24 patients with Pro homozygosity had a duration of disease >7 years. In contrast, 87 of 123 patients with Arg/Arg had short-standing UC (≤7 yrs) and 66 of 96 with Arg/Pro had short-standing UC (χ-squared, 22.86; P < 0.0001). Thirty-four of 243 patients affected with UC had a positive family history for colorectal carcinoma (CRC). In those patients p53, Pro/Pro was significantly related to a family history of CRC (odds ratio, 38.1). Conclusions These preliminary data suggest that polymorphism at codon 72 of the p53 gene influences the clinical course of UC, with continuous disease associated with p53 Pro homozygosity.     

Comparison of flow cytometry and histology with mutational screening for p53 and Ki-ras mutations in surveillance of patients with long-standing ulcerative colitis.

BACKGROUND: We evaluate the usefulness of screening for p53 and Ki-ras mutations in comparison with histological and flow cytometric findings. METHODS: We analyzed 1486 biopsy samples from 769 locations of 83 patients with long-standing ulcerative colitis enrolled in a surveillance program by means of histology, flow cytometry and SSCP analysis. As a control we used 66 biopsy samples of 16 patients with irritable bowel disease. RESULTS: With respect to all biopsy samples analyzed, DNA aneuploidy was found in 32.5% (27/83) of patients, dysplasia in 22.9% (15/83), p53 in 21.7% (18/83) and Ki-ras mutations in 18.1% (15/83) of patients. None of these markers was found in our control group. In 7 out of 10 patients who displayed dysplastic findings during endoscopic surveillance p53 and / or Ki-ras mutations were present in at least one colonoscopy. Statistically significant associations were observed between dysplasia and DNA aneuploidy (P < 0.001), between dysplasia and p53 mutations (P = 0.05) and between dysplasia and p53 and/or Ki-ras mutations (P = 0.002). No significant associations were found between dysplasia and Ki-ras mutations alone. The results for the SSCP analysis showed a much broader variation than those for the flow cytometric analysis. CONCLUSIONS: These results show that screening for p53 and Ki-ras mutations can be a useful adjunct in surveillance of patients with long-standing ulcerative colitis.     

p53 mutations in british patients with hepatocellular carcinoma: clustering in genetic hemochromatosis.

BACKGROUND & AIMS: Environmental factors are important in the etiology of hepatocellular carcinoma (HCC). Aflatoxin B1 causes a specific point mutation in the p53 tumor-suppressor gene in exposed individuals. In Western populations, mutations of this gene seem to be less frequent. We have investigated the role of p53 mutations in tumorigenesis in British patients with HCC. The aim of this study was to determine the frequency and mutational spectrum of the p53 gene in HCCs from British patients. METHODS: DNA from 170 HCCs, of well-defined etiology, in British patients was analyzed by single-stranded conformational polymorphism using the polymerase chain reaction technique. Mutations were then characterized by direct sequencing. RESULTS: Twenty-nine percent of tumors had p53 mutations. Ten of 14 (71%) hemochromatotic cancers had mutations within the p53 gene, and clustering of these mutations at codon 220 (A-G) was found in 5 cases; 3 others had T-A mutations. No clustering was found in HCCs with other etiologies. CONCLUSIONS: p53 mutations are more common than was thought in Northern European HCCs. This is the first demonstration of p53 mutational clustering in HCCs from hemochromatotic subjects.     

p53 codon 72 polymorphism and hepatocellular carcinoma: a meta-analysis

Background

Hepatocellular carcinoma (HCC) is one of the most common malignant neoplasms worldwide. The p53 gene is frequently mutated in some histological subtypes of HCC. The role of p53 mutations and polymorphic variant of codon 72 in the prognosis of disease is still unclear. The p53 tumor suppressor gene Arg72Pro polymorphism has been associated with HCC. However, results were inconsistent. This meta-analysis was performed to estimate the association between p53 Arg72Pro polymorphism and HCC or HCC infected by HBV/HCV.

Methods

Electronic search of PubMed was conducted to select studies. Studies containing available genotype frequencies of Arg72Pro were chosen, and pooled odds ratio (OR) with 95 % confidence interval (CI) was used to assess the association.

Results

Ten published studies, including 1,371 HCC cases and 2,517 controls were identified. The overall results suggested that the variant genotypes were associated with the HCC risk (Pro/Pro vs. Pro/Arg + Arg/Arg: OR 1.355, 95 % CI 1.041–1.764, p = 0.024). In the stratified analysis, individuals with the Pro/Pro in the recessive model had increased risk of HCC (OR 1.927, 95 % CI 1.127–3.297, p = 0.017) in Caucasian. A symmetric funnel plot, the Begg’s test, was suggestive of the lack of publication bias. There was no association between the p53 codon 72 polymorphism and HBV/HCV-positive HCC.

Conclusion

This meta-analysis suggests that p53 condon 72 Pro/Progenotypes are associated with increased risk of HCC in Caucasian. To validate this association, further studies with larger participants worldwide are needed to examine the associations between this polymorphism and HCC.     

High levels of p53 protein expression do not correlate with p53 mutations in hepatocellular carcinoma

To determine the relationship between p53 altered expression and p53 mutations in hepatocellular carcinoma (HCC), we analysed p53 protein immunohistochemically and assessed the presence of mutations in exons 4-8 of the p53 gene using SSCP assay in 117 HCCs corresponding to 78 patients. We also determined the relationship of p53 expression with cellular proliferation by immunostaining with monoclonal antibodies to Ki-67. We found significant levels of p53 protein expression in 23.1% of the 117 cases studied, but identified mutations in only 12 cases (10.3%). Only four of the p53-positive cases had mutations in the regions analysed. Six of the cases that displayed mutations at p53 gene were negative for immunohistochemical analysis (IHC) and two cases showed positive immunoreactivity in the cytoplasm of the cell. In conclusion, strong IHC reactivity for p53 protein is not an indicator of the presence of p53 gene mutations at exons 4-8 in HCC. Thus, p53 loss of function in HCC should be evaluated both by p53 mutation analysis and p53 protein expression, as both give complementary information about p53 status.     

p53 and p21/Waf1 protein expression and K-ras codon 12 mutation in carcinoma of the papilla of Vater

OBJECTIVE: There have been few studies on the molecular biological characteristics of carcinoma of the papilla of Vater. In this study, p53 and p21/Waf1 expression and K-ras codon 12 mutation in carcinoma of the papilla of Vater were investigated. METHODS: Thirty-seven cases of carcinoma of the papilla of Vater were studied. Macroscopically, the carcinoma was ulcerative in 15 cases and nonulcerative in 22 cases. Histologically, nine were intestinal type, 27 were pancreaticobiliary type, and one was undifferentiated. Formalin-fixed, paraffin-embedded sections were immunohistochemically stained for p53 and p21. K-ras codon 12 mutation was detected with the two-step polymerase chain reaction-restriction fragment length polymorphism method, followed by direct sequencing. RESULTS: p53 overexpression was found in 17 of 37 cases (46%) and was more frequent in the ulcerative type than in the nonulcerative type (67% vs 32%, p < 0.05). p21/Waf1 protein expression was found in 15 of 37 cases (41%), and was not correlated with that of p53. K-ras codon 12 mutation was found in 14 of 37 cases (38%), and was more frequently detected in the intestinal type than in the pancreaticobiliary type (66% vs 30%, p < 0.05). On direct sequencing, the mutations were mainly GGT to GAT (9/14) and GGT to GTT (4/14). The type of mutation did not correlate with the histological type. CONCLUSIONS: In carcinoma of the papilla of Vater, p53 overexpression may play a role in tumor ulceration. p21/Waf1 expression is induced via a p53-independent pathway. Carcinomas of the intestinal and pancreaticobiliary types may develop via different mechanisms, and K-ras mutation is mainly associated with the intestinal type.     

p53 codon 72 polymorphism in Taiwanese breast cancer patients

There are clear discrepancies between ethnicity and geographic area regarding the peak age incidence and mortality of breast cancer. Underlying variances include genetic, environmental, and socioeconomic factors. The wild-type p53 codon has two common polymorphic variants from a single-base-pair substitution at codon 72, where either C-C-C encodes proline (p53-p72) or C-G-C encodes arginine (p53-R72). We aim to study the p53 codon 72 genotypes of patients with breast cancer in Taiwan and make a comparison with the published data to ascertain whether any difference exists between Taiwanese and Western patients with breast cancer. We also evaluated the effect of the p53 codon 72 polymorphism on clinicopathologic features. We examined blood from 170 Taiwanese women with breast cancer with polymerase chain reaction–restriction fragment length polymorphism for the genotypes of p53 codon 72. For the p53 codon 72 polymorphism, there were 31 p53-P/P72 (18.2%), 93 p53-R/P72 (54.7%), and 46 p53-R/R72 (27.1%) with the allele frequencies 0.54 for the p53-R72 and 0.46 for p53-P72, respectively. Our results indicate that there was more p53-P72 (40.6% in Asians vs. 26.4% in Caucasians) and twice the incidence of p53-P/P72 homozygotes (18% in Asians vs. 8% in Caucasians) among the Asian population. Patients with the p53-R/R72 variant were more likely to have a t1 tumor size status (55.2%) compared with patients with the P53-P/R72 (30.9%) or P53-P/P72 variant (36%). Our results support the hypothesis that genetic factors may contribute to the difference between Taiwanese or Asian breast cancer and Western breast cancer patient populations.     

The association between selected risk factors for pancreatic cancer and the expression of p53 and K-ras codon 12 mutations

Background Pancreatic cancer is a major contributor to cancer mortality. Studies suggest that a few risk factors, including cigarette smoking, body mass index, having a relative with pancreatic cancer, and diabetes may be related to pancreatic cancer risk. Aim of the Study We conducted a case–control study in southeastern Michigan to examine the relation between the abovementioned risk factors and mutations of the K-ras oncogene and p53 tumor suppressor gene. Methods Two hundred forty-five patients with newly diagnosed pancreatic cancer and 420 general population controls were enrolled in the study. For this analysis, all case subjects were restricted to the pancreatic cancer patients that had tissue blocks available for study (n = 51). In-person interviews were conducted to ascertain information on demographic and lifestyle factors. Adjusted logistic regression analyses were conducted to compare various subject characteristics of pancreatic cancer patients with K-ras and p53 mutations and their subtypes to the characteristics of the general population controls. Results Smoking (adjusted odds ratio [aOR] = 2.0; 95% confidence interval [95%CI] = 0.9–4.3) and diabetes diagnosed 5 or more years before interview (aOR = 3.4; 95%CI = 1.3–8.8) were associated with pancreatic cancer patients positive for K-ras codon 12 mutations, but not with pancreatic cancer patients negative for K-ras codon 12 mutations. On the other hand, none of the examined risk factors were meaningfully related to patients with p53 mutations. Conclusions This study suggests that some recognized risk factors for pancreatic cancer may also be associated with K-ras codon 12 mutations. However, further large-scale studies are warranted.     

Prognostic value of p53 mutations in patients with locally advanced esophageal carcinoma treated with definitive chemoradiotherapy

Purpose. A significant correlation has been found between p53 mutation and response to chemotherapy or radiotherapy. To determine the prognostic value of p53 mutation in patients with locally advanced esophageal carcinoma treated with definitive chemoradiotherapy, p53 mutation was analyzed using the biopsied specimens taken for diagnosis. Methods. Concurrent chemoradiotherapy was performed for 40 patients with severe dysphagia caused by esophageal squamous cell carcinoma associated with T3 or T4 disease. Chemotherapy consisted of protracted infusion of 5-fluorouracil, combined with an infusion of cisplatinum. Radiation treatment of the mediastinum was administered concomitantly with chemotherapy. The p53 gene mutation was detected by fluorescence-based polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) methods. DNA sequences were determined for DNA fragments with shifted peaks by SSCP methods. Results. Of the 40 patients, 15 had T3 disease and 25 had T4 disease; 11 patients had M1 lymph node (LYM) disease. Of the 40 patients, 13 (33%) achieved a complete response. The median survival time was 14 months, and the 2-year survival rate was 20%. Among the 40 tumor samples, p53 mutation was detected in 24 tumors (60%). The survival rate in the 24 patients with p53 mutation did not differ significantly from that in the 16 patients without p53 mutation. In contrast, the 15 patients with T3 disease survived longer than the 25 patients with T4 disease (P = 0.016); however, the survival rate in the 11 patients with M1 LYM disease did not differ significantly from that in the 29 patients without M1 LYM disease. Conclusion. Concurrent chemoradiotherapy is potentially curative for locally advanced esophageal carcinoma, but p53 genetic abnormality has no impact on prognosis. Received: December 6, 2000 / Accepted: January 26, 2001     

p53 gene mutations and expression of p53 and mdm2 proteins in invasive breast carcinoma

The aim of the study was to analyzep53 gene mutations and the expression of p53 and mdm2 proteins in 31 randomly selected invasive breast carcinomas. The results were then correlated with tumor grade, stage, estrogen receptor status, nodal status, and DNA ploidy. The expression of the proteins p53 and mdm2 was determined immunohistochemically using formalin-fixed, paraffin-embedded material. Screening for p53 mutation involved analysis of the highly conserved regions of thep53 gene (exons 5–9) by the polymerase chain reaction/single-strand conformation polymorphism (PCR-SSCP) technique. PCR products with band shifts were directly sequenced. Immunohistochemical staining of p53 was positive in 9 cases (29.0%), only 2 of which showed ap53 gene mutation. These were identified as a CG transversion at the second position of codon 278 in exon 8 and an AG transition at the second position of codon 205 in exon 6. A third case with a mutation was observed (CT transition, position 1 of codon 250 in exon 7) that did not show p53 immunohistochemically. Of the 9 p53-positive tumors, 2 were moderately differentiated (grade II). The remaining tumors were poorly differentiated (7/9). By contrast, p53-negative carcinomas were well differentiated (grade I) in most cases (P=0.02). DNA cytometry in 8 of the 9 p53-positive carcinomas revealed an aneuploid stem line. The majority of the p53-negative tumors were diploid (P=0.01). Mdm2 oncoprotein was detected in 10 tumors (32.2%), 4 of which were p53-positive, including the 3 with mutations. The grading of the mdm2-positive tumors was moderate or poor, G1 carcinomas were always noted to be mdm2-negative (P=0.04). Overexpression of p53 protein is a complex mechanism and does not merely indicate the detection of mutations in thep53 gene. This study has shown that p53 expression correlates with tumor grade and DNA ploidy. Mdm2 expression was also associated with the tumor grade. Immunohistological demonstration of the p53 protein alone is insufficient as a basis for comment on the functional state of thep53 gene and gene product. The interrelation between recognition of the p53 protein and gene mutation needs more careful assessment to define their roles in the control of neoplasia.     

N-ras and p53 gene mutations in Japanese patients with myeloproliferative disorders

Alterations of the N-ras oncogene and p53 tumor suppressor gene have been demonstrated to play an important role in pathogenesis of hematological malignancies. We simultaneously investigated genetic lesions of both genes in bone marrow cells from 64 Japanese patients with myeloproliferative disorders (MPD), including polycythemia vera (PV), essential thrombocythemia (ET), and idiopathic myelofibrosis (MF), by direct sequencing analysis. No mutations of the N-ras gene were detected in any cases. Two patients, one with chronic neutrophilic leukemia derived from PV and one with acute mylogenous leukemia derived from ET, exhibited three mutations of the p53 gene. Among them, two were missense mutations in exon 5 or 7 and one was a deletion in exon 5. All samples in chronic phase or from MF were devoid of mutations in both genes. These data suggested that disruptions of both genes are extremely rare in MPD in chronic phase and that loss of functions in the p53 gene could be involved in progression of MPD such as PV and ET.     

p53 mutations in mantle cell lymphoma are associated with variant cytology and predict a poor prognosis

Mutations of the p53 tumor suppressor gene have been described in several subtypes of non-Hodgkin's lymphoma, but the incidence of p53 mutations in mantle cell lymphoma (MCL) is unknown. We hypothesized that cases of MCL with a variant or high-grade cytology would have a higher likelihood of p53 mutations than typical MCL. We were also interested in the prognostic significance of p53 mutations in MCL. Therefore, a series of 53 well-characterized cases of MCL with DNA from 62 tissue samples were analyzed by the polymerase chain reaction with denaturing gradient gel electrophoresis for exons 5-8 of p53. Immunoperoxidase studies with the antibody DO-7 to p53 protein were also performed on frozen sections. We found mutations of the p53 gene in 8 of the 53 cases (15%) of MCL. Missense mutations predominated, and 50% of the mutations occurred at known p53 hotspot codons. Of 21 cases with variant cytology (ie, anaplastic or blastic), 6 (28.6%) had p53 mutations as compared with only 2 of 32 cases (6.3%) with typical MCL cytology (P = .05), and p53 mutations preceded the development of variant cytology in 2 patients. Overexpression of p53 protein was observed in 6 of the 8 cases (75%) with p53 mutations and in none of the 45 wild-type cases. The median survival of the cases with mutant p53 was only 1.3 years (all died), whereas the median survival of cases with germline p53 was 5.1 years (P = .023). These results suggest that mutations of p53 may be one mechanism involved in the development of variant forms of MCL and indicate that p53 mutations in MCL predict a poor prognosis.