Frequency Of P53 Gene Mutations Research Articles

Curcumol triggers apoptosis of p53 mutant triple-negative human breast cancer MDA-MB 231 cells via activation of p73 and PUMA.

Triple-negative breast cancer (TNBC; estrogen receptor-negative, progesterone receptor-negative and Her-2-negative) is often accompanied by a higher frequency of p53 gene mutations. Therefore, TNBC is challenging to treat due to a lack of biological targets and a poor sensitivity to conventional therapies. Curcumol is a monomer composition isolated from the ethanol extracts of Curcuma wenyujin, a Chinese medicinal herb traditionally used as a cancer remedy. Previous studies have revealed that curcumol is able to block proliferation in various human tumor cell lines. However, the underlying mechanisms have yet to be elucidated. The present study aimed to investigate the anticancer effects of curcumol in the human p53 mutant TNBC MDA-MB-231 cell line and its underlying mechanisms. Cell viability and growth were determined by MTT and a mice xenograft model assay, respectively. Cell cycle distribution was examined by flow cytometry. Apoptosis was evaluated by apoptotic morphology analysis with DAPI staining and flow cytometric analysis following Annexin V/propidium iodide staining. The protein expression in cells was evaluated by immunoblotting. Treatment of MDA-MB-231 cells with curcumol resulted in a significant inhibition of cell proliferation in vitro [half maximal inhibitory concentration (IC50)=240.7±85.0 µg/ml for 48 h and IC50=100.2±13.5 µg/ml for 72 h]. Curcumol treatment also resulted in the suppression of xenograft growth in vivo (100 or 200 µg/kg for 21 days), as well as G1 phase arrest and an apoptotic response, which were accompanied by the upregulation of p73 expression and the activation of the expression of p53 upregulated modulator of apoptosis (PUMA) and Bcl-2 antagonistic killer (Bak). No cleavage of poly (ADP-ribose) polymerase was detected. To the best of our knowledge, the present data demonstrate for the first time that curcumol inhibits the growth of MDA-MB-231 cells and triggers p53-independent apoptosis, which may be mediated by the p73-PUMA/Bak signaling pathway. Curcumol may, therefore, be a potential compound for use in the development of novel TNBC therapeutics.

Identification of P53 Tumor Suppressor Gene Alterations in Human Glioma Using Sscp-Pcr Technique

The P53 is the most commonly altered gene in cancers, which is located on chromosome 17p. Because of it is important role in the cell cycle it considered as the guardian of the genome that maintains genome integrity. In this study we analyzed DNA from 15 surgical specimens of human glioma for mutations in the p53 gene along exons 6-9 using single-strand conformation polymorphism analysis of polymerase chain reaction product (PCR-SSCP). The frequency of P53 gene mutation in gliomas examined was 26.6% (4 of 15). All 4 mutated cases were in exon 6 and no mutation was observed in exon 7,8 and 9. The results suggest the involvement of P53 gene mutation in Glioma and it might play an important role in the tumorigenesis process of patients with brain tumor in preliminary study in Duhok province.

Frequency of p53 gene mutation and protein expression in oral squamous cell carcinoma.

To determine the frequency of p53 gene mutation and protein expression in Oral Squamous Cell Carcinoma (OSCC) and to establish correlation between the two. Analytical study. Histopathology Department and Molecular Biology Laboratory, Armed Forces Institute of Pathology (AFIP), Rawalpindi, from May 2010 to May 2011. Thirty diagnosed cases of OSCC were selected by consecutive sampling. Seventeen were retrieved from the record files of the AFIP, and 13 fresh/frozen sections were selected from patients reporting to the Oral Surgery Department, Armed Forces Institute of Dentistry (AFID). Gene p53 mutation was analyzed in all the cases using PCRSSCP analysis. DNA was extracted from the formalin-fixed and paraffin-embedded tissue sections and fresh/frozen sections. DNA thus extracted was amplified by polymerase chain reaction. The amplified products were denatured and finally analyzed by gel electrophoresis. Gene mutation was detected as electrophoretic mobility shift. The immunohistochemical marker p53 was applied to the same 30 cases and overexpression of protein p53 was recorded. Immunohistochemical expression of marker p53 was positive in 67% [95% Confidence Interval (CI) 48.7-80.9] of the cases. Mutations of the p53 gene were detected in 23% (95% CI 11.5-41.2) of the OSCC. No statistically significant correlation was found between p53 gene mutation and protein p53 expression (rs=-0.057, p=0.765). A substantial number of patients have p53 gene mutation (23%) and protein p53 expression (67%) in oral squamous cell carcinoma (OSCC).

UV-Independent p53 Mutations in Sebaceous Carcinoma of the Eyelid

Sebaceous carcinoma of the eyelid is a potentially fatal malignancy that has been associated with p53 gene mutations. The purpose of this study is to determine the frequency of p53 mutations in sebaceous carcinoma of the eyelid and to determine whether there is any relationship between the presence of p53 mutations and tumor invasiveness. Retrospective case series. Fourteen samples of sebaceous carcinoma that had been resected from Caucasian patients between 1994 and 2010 were analyzed for p53 gene mutations with PCR and Sequencher software. Patient charts were reviewed to draw clinicopathologic correlations in relation with the presence of p53 gene mutations. Seven of 14 (50%) sebaceous carcinoma samples were found to have p53 gene mutations. None of the samples had tandem mutations, which are caused by UV exposure. No statistically significant trend was found between the presence of p53 mutations and metastasis, recurrence, tumor size, TNM stage, and pagetoid spread. There was a similar frequency of p53 gene mutations found in stage T1, T2, and T3 tumors. p53 Mutations are found in a high percentage of sebaceous carcinomas in the Caucasian population. The absence of tandem mutations is consistent with the belief that sebaceous carcinoma develops as a UV-independent process. There does not appear to be a significant correlation between the presence of p53 mutations and tumor size, recurrence, metastasis, pagetoid spread, or location. The similar frequency of p53 mutations in both low- and high-stage tumors implies that p53 gene mutations may be involved in early stages of carcinogenesis of sebaceous carcinoma.

Loss of p53 in esophageal squamous cell carcinoma and the correlation with survival: Analyses of gene mutations, protein expression, and loss of heterozygosity in Japanese patients

A high frequency of p53 protein expression or gene mutation has been reported in the early stages of esophageal squamous cell carcinoma (ESCC), and thus loss of p53 function is thought to be very important in esophageal carcinogenesis. However, there is controversy surrounding the correlation between p53 dysfunction and ESCC tumor progression. The complexity arises from the different modalities, such as mutation analysis, immunohistochemistry, and the detection of loss of heterozygosity (LOH) at the p53 genomic locus. In this study, we comprehensively analyzed p53 gene mutation, p53 protein expression, and LOH at 17p13 in 94 surgically resected Japanese cases of ESCC. The frequency of p53 gene mutation was 60.6%. The rate of positive p53 protein expression was 56.4%. The frequency of LOH at 17p13 was 67.5%. There was a statistically significant correlation between the presence of a gene mutation and LOH, whereas, there was no significant correlation between gene mutation and protein expression. Despite the importance of loss of p53 function in esophageal carcinogenesis, none of the examined parameters, either singly or combined, correlated with overall survival. Taken together, p53 function is a primary target for esophageal carcinogenesis but there is no apparent correlation with the malignant phenotype in ESCC.

Cancer genes alterations and HPV infection in oral squamous cell carcinoma

The aim of this study was to gain a better understanding of cancer genes contributing to oral squamous cell (OSCC) development and progression and correlate genetic changes to clinical parameters. Human papilloma virus (HPV) 16 detection is also included in the study. 60 samples of OSCC were analysed for c-erbB2 and c-myc amplification by dPCR, H-ras and p53 point mutations by PCR/SSCP. HPV was detected via amplification of its E1 and E6 genes. c-erbB2 was altered in 45%, c-myc in 35%, H-ras in 22% and p53 in 60% of samples. HPV was detected in 10% of cases. The frequency of p53 gene mutations showed a statistically significant association with tumour stage. Patients with c-erbB2 and H-ras alterations had lower survival than patients without these alterations. The number of detected genetic changes was remarkable but statistical association with tumour natural history was poor, indicating high clonal heterogeneity and multiple pathways of carcinogenesis.

Quantitative Analysis of mRNA for 10 Different Drug Resistance Factors in Dogs with Lymphoma

Expression levels of ABCB1, ABCC1, Lung resistance-associated protein (LRP), ABCG2, p53, p21(waf1), Bcl-2, CD40L, glutathione S-transferase alpha (GSTα), and O⁶-methylguanine-DNA-methyltransferase (MGMT) genes, and mutation of p53 gene were examined in 23 dogs with multicentric high-grade lymphoma to explore their association with drug resistance of the tumor cells. Dogs were divided into chemotherapy-sensitive (n=13) and -resistant (n=10) groups according to the response to a 6-month modified version of the University of Wisconsin (UW)-Madison chemotherapy protocol (UW-25), and expression levels of these factors and frequency of p53 gene mutation were compared between groups. No significant differences were observed in expression levels of each factor between groups. However, 4 dogs in the chemotherapy-resistant group showed high expression of ABCB1. No significant difference was observed in the frequency of p53 mutation between groups. A possible association of ABCB1 with resistance to UW-25 was shown, but no uniform mechanism associated with drug resistance could be identified in dogs with lymphoma.

Molecular gate keepers succumb to gene aberrations in colorectal cancer in Kashmiri population, revealing a high incidence area

Background/Aim:Colorectal cancer (CRC) is one of the leading malignancies worldwide and has been reported to show geographical variation in its incidence, even within areas of ethnic homogeneity. The aim of this study was to identify p53 and K-ras gene mutations in CRC patients in a Kashmiri population, and to assess whether these mutations are linked with clinicopathological parameters.Materials and Methods:Paired tumor and normal tissue samples from a consecutive series of 53 patients undergoing resective surgery for CRC were prospectively studied for p53 and K-ras gene mutations by PCR/single strand conformation polymorphism (SSCP).Results:Less than half (45%, 19/42) of the patients presented mutations in the p53 gene. Twenty eight mutations were found in the p53 gene, which comprised of 23 substitutions (17 transitions + 6 transversions), and five insertions. The 23 substitutions constituted 18 missense mutations, two nonsense mutations, and three silent mutations. Of the 28 mutations (7.14%) observed in this study, 2 were not previously reported for CRC samples and were identified as novel p53 mutations. A few patients (22.64%, 12/53) presented with mutations in K-ras, constituting 13 missense mutations, out of which 11 were G→A transitions, one was a G→C transversion, and one a G→T transversion. More than half (61.5%) of the mutations occurred in codon 12 whereas a few (38.5%) occurred in codon 13. One tumor contained missense mutations in both codons. Comparison of the mutation profiles of our patients with those of other ethnic populations and regions reflected both differences and similarities, indicating co-exposure to a unique set of risk factors.Conclusion:Mutations of the p53 and K-ras genes are some of the most common genetic changes in the development of human CRC. The high frequency of p53 gene mutations implicates p53 as a predominant factor for CRC in the high-risk ethnic Kashmiri population.

Early development of histiocytic sarcomas in p53 knockout mice treated with N-bis(2-hydroxypropyl)nitrosamine

p53 knockout mice have been utilized for the functional analysis of p53 in carcinogenic processes and for the evaluation of the carcinogenic potential of chemicals. In this study, we established that p53 knockout mice have an elevated susceptibility to the induction of histiocytic sarcoma (HS) by N-bis(2-hydroxy-propyl)nitrosamine (BHP). p53 heterozygous (+/-) and wild-type (+/+) mice were treated with 20 or 200 ppm BHP in their drinking water for 15 weeks or with 20 ppm BHP for 40 weeks. An additional group of p53 nullizygous (-/-) mice were treated with 20 ppm BHP for 15 weeks. In a 15-week experiment, hepatic HSs were unexpectedly observed in BHP-treated p53 (-/-) mice (30.8%) but not in p53 (+/-) and (+/+) mice and untreated (-/-) mice, indicating that a complete loss of p53 dramatically accelerates the genesis of HS. In a 40-week experiment, HSs were significantly increased in female p53 (+/-) mice (37.5%) as compared with female (+/+) mice (5.0%). Additionally, PCR-SSCP and sequencing analysis revealed a high frequency of p53 gene mutations in HSs, demonstrating the involvement of p53 gene mutations in HS development. Our data add to the understanding of the carcinogenic susceptibility of p53 knockout mice, and may help to elucidate the pathogenesis of HS development.

P53 Gene mutations in esophageal squamous cell carcinoma and their relevance to etiology and pathogenesis: Results in Japan and comparisons with other countries

Esophageal squamous cell carcinoma is a form of cancer that has varying incidence rates among different countries, distinct geographic areas and different ethnic groups. According to previous reports, p53 gene mutations have been identified in 20-80% of these tumors, and these mutations have occurred at an early stage. These findings suggest that such mutations play an important role in esophageal carcinogenesis, and highlight the importance of mutagens, which cause sequence alterations in the p53 gene. In order to clarify the environmental factors and the molecular mechanisms that may be responsible for the occurrence and prevention of a specific mutation in the process of esophageal carcinogenesis, we analyzed p53 gene mutations in 95 samples of esophageal squamous cell carcinoma. We further reviewed published reports investigating the frequency of p53 gene mutations in esophageal cancer from high-risk areas to normal-risk areas and compared these findings to our results in Japan. The frequency of p53 gene mutations in Japanese esophageal cancer is 47.4% and there are three prominent features: (1) a predominance of transversions, in particular the G:C to T:A transversion; (2) a relatively low frequency of transitions; and (3) a relatively high percentage of frameshift mutations. These results indicate the possible importance of the benzo[a]pyrene metabolite and oxidative DNA damage in esophageal carcinogenesis and scarcely correlate with DNA replication errors or alkylation in comparison to other gastrointestinal cancers. In addition, we observed a peculiar sequence of frameshift mutations. Taken together, these data suggest that this tumor suppressor gene plays a critical role in the multistep carcinogenesis process for esophageal squamous cell cancer.

Severity of atrophic gastritis related to antiparietal cell antibody and gastric carcinogenesis, including p53 mutations

Infection with Helicobacter pylori (Hp) has been linked to atrophic gastritis, an inflammatory precursor of non-cardia gastric carcinoma. Mutations in the p53 gene are one of the most frequent genetic alterations in gastric carcinoma. In a subgroup of atrophic gastritis, antiparietal cell antibody (APCA) has been detected. This study was aimed to clarify the role of APCA in the progression of atrophic gastritis and gastric carcinogenesis, and to determine the relationship of the severity of atrophic gastritis to gastric carcinoma and to p53 mutations. In 494 control subjects and 284 gastric carcinoma patients, serum APCA was evaluated and all subjects and patients were classified into four groups using serologic markers (anti-Hp IgG antibody and pepsinogen (PG) test: positive; PG I < 70 microg/L and PG I/II ratio < 3.0) as follows: A, HP- PG-; B, HP+ PG-; C, HP+ PG+ and D, HP- PG+. p53 mutations were analyzed in 174 of 284 patients. Antiparietal cell antibody seropositivity increased from group B to D, however, no difference in its positivity was found between controls and patients. The incidence of gastric carcinoma increased from A to D, especially the intestinal subtype. The frequency of p53 gene mutations was higher in PG+ than in PG- gastric carcinoma. Antiparietal cell antibody seropositivity is involved in the progression of a subgroup of atrophic gastritis, but not associated with gastric carcinogenesis. Severe atrophic gastritis is associated with susceptibility to gastric carcinoma, especially the intestinal subtype, and p53 mutations.

Quantification of MDM2 Gene Expression Level by RQ-PCR Is Predictive of the First Complete Remission in Adulte Acute Myeloid Leukaemia.

The overall survival of patients with p 53 mutated gene acute myeloid leukaemia (AML) is significantly shorter than those of patients without mutations. The frequency of p53 gene mutations in AML ranges from 4 to 15% in populations from USA and Europe, thus this is not a useful criteria in the vast majority of patients with a poor prognosis. Mdm2 is the natural functional inhibitor of p53, but very few studies have assessed its prognosis value in AML, and this was done only at the protein level, suffering major lacking of precision.In this study, we have quantified gene expression levels of both MDM2 and p53 by RQ-PCR in a series of 18 patients with more that 50% blast cell in the bone marrow: 4 AML1, 6 AML2 (one with multilineage dysplasia), 4 AML4 (one AML4 Eos), 4 AML5. Median age was 57 years, ranging 39–84. Eight patients had a white cell blood count over 30 G/L. Eleven patients had a normal karyotype, 3 had a complex caryotype, 2 had an inv(16). FLT3 amplification was found in 2 cases. Two patients died immediately following the diagnosis because of an immediate massive global failure of vital functions. Three patients were treated with low doses of Aracytine because of the performance status. Thirteen patients were treated with intensive chemotherapy according classical scheme, and complete remission was obtained in 6 cases.After total RNA extraction of bone marrow mononuclear cells, assessment of MDM2 and p53 gene expression levels was done in duplicate on an ABI PRISM 7000 automat using the TaqManR Assay on demandTM gene expression reference system. The Abl1 gene was used as a reference gene for the control of amplification. The relative expression levels of the genes were calculated as follow: briefly, for each gene, the cycle threshold (CT) was defined for a delta Rn of 10−1. Then, the delta CT (DCT) was calculated as the CT of the gene minus the CT of Abl1 (expected CT for Abl1 ranged from 22 to 24). For each experimental condition, the delta delta CT (DDCT) was calculated as the DCT of the given condition minus the DCT of the RNA pool. For each gene and in each experimental condition, the calculated relative gene expression level was equal to 2−DDCT.No correlation was found between p53 gene expression levels and any of the other clinical, biological or genetic prognosis marker. By contrast, complete remission was obtained for all patients with low levels MDM2 expression and MDM2 expression was markedly increased in 5 out the 7 patient without remission (t-test, p=0,01). It is noteworthy that, among the 3 patients treated with low doses of Aracytine, the patient with the shortest survival was the only one with increased levels of MDM2. No correlation was found between MDM2 gene expression levels and other biological prognosis markers. This suggests that quantification of MDM2 mRNA by RQ-PCR could be an interesting prognosis factor in AML.

Relationship between genetic polymorphisms of drug-metabolizing enzymes ( CYP1A1 , CYP2E1 , GSTM1 , and NAT2 ), drinking habits, histological subtypes, and p53 gene point mutations in Japanese patients with gastric cancer

Genetic polymorphisms of drug-metabolizing enzymes have recently been shown to affect susceptibility to chemical carcinogenesis. However, the molecular mechanisms of individual susceptibility to gastric cancer have not been fully understood. Therefore, we studied the relationship between the genetic polymorphisms of drug-metabolizing enzymes, drinking habits, histological subtypes, and p53 gene point mutations in Japanese patients with gastric cancer. The genotypes of cytochromes P450 ( CYP) 1A1 and 2E1, glutathione S-transferase ( GST) M1, and N-acetyltransferase ( NAT) were investigated by polymerase chain reaction (PCR), allele-specific PCR, or restriction fragment length polymorphism (RFLP) following PCR in 146 Japanese patients with gastric cancer (67 intestinal-type and 79 diffuse-type carcinomas) and 177 autopsied controls. In addition, p53 gene point mutations of exons 5 through 9 in gastric cancer tissues were determined. The frequency of either being a habitual drinker or having a CYP2E1(*) 1A/(*) 1A genotype was significantly higher in patients with intestinal-type gastric cancer than in control subjects. The difference between the frequencies of habitual drinkers with the CYP2E1(*) 1A/(*) 1A genotype and non-drinkers with the CYP2E1(*) 5B allele was much more significant in the intestinal-type cancer versus the control group. Among intestinal-type cancer patients with the CYP2E1(*) 1A/(*) 1A genotype, p53 point mutations were significantly more frequent in the group of habitual drinkers than in that of non-drinkers. On the other hand, the combination of GSTM1 null and CYP2E1(*) 1A/(*) 1A genotypes increased the risk for diffuse-type gastric cancer, but had no influence on the frequency of p53 gene mutations. The present study suggests that individuals with both the CYP2E1(*) 1A/(*) 1A genotype and a history of habitual drinking have an increased risk of intestinal-type gastric cancer with a high frequency of p53 gene point mutations in the gastric mucosa.

Analysis of Ki-ras and p53 gene mutations in laterally spreading tumors of the colorectum.

A laterally spreading tumor (LST) is considered to be a specific subtype of superficial colorectal tumors, in view of its characteristic clinicopathological features. We attempted to compare genetic alterations found in LST (>10 mm) with those found in IIa-type adenomas (10 mm or less (small superficial elevated lesion)) and conventional polypoid adenomas (>10 mm). In addition, multiple sampling by microdissection was performed for 14 LST to examine genetic heterogeneity in the Ki-ras and p53 gene mutation patterns. Polymerase chain reaction, single-strand conformation polymorphism and direct sequencing were used to analyze Ki-ras and p53 gene mutations in 73 sporadic colorectal adenomas: 28 LST; 22 IIa-type adenomas; and 23 polypoid adenomas. Ki-ras gene mutations were found more frequently in LST (6/28 tumors) and polypoid adenomas (6/23 tumors) than in IIa-type adenomas (2/22 tumors), although this difference was not statistically significant. The frequency of p53 gene mutations in the 28 LST was 25% (7/28), which was significantly higher than that found in IIa-type adenomas (P < 0.05). However, although p53 gene mutations were found more frequently in LST than in polypoid adenomas, this difference was not statistically significant. Seven LST exhibited a combination of wild-type and mutant-type tumor cells having the p53 gene mutation pattern, whereas a pattern of different Ki-ras gene mutations was found in two of three LST that exhibited Ki-ras gene mutation heterogeneity. We suggest that the LST exhibited a characteristic pattern in terms of the Ki-ras as well as the p53 gene mutation pattern, thereby supporting the hypothesis that LST is a specific subtype of colorectal tumors.

Analysis of p53, K-ras, c-kit, and beta-catenin gene mutations in sinonasal NK/T cell lymphoma in northeast district of China.

Recently we reported the different frequencies of p53 and c-kit gene mutations among sinonasal NK/T cell lymphoma (NKTCL) in Korea, north China (Beijing), and Japan, suggesting some racial, environmental, or life-style differences as a possible cause of nasal tumorigenesis. In this study, gene mutations in p53, c-kit, K-ras, and beta-catenin gene were analyzed by polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) followed by direct sequencing in 20 cases of sinonasal NKTCL from northeast China (Shen Yang). Age of patients ranged from 5 to 63 (median, 40.0) years. p53 gene mutations were found in eight of 20 cases (40%), with exon 4 involvement in 10% of cases. The majority was missense mutations and G:C to A:T transition was predominant. The frequency of the c-kit and K-ras gene mutations was low (5%), while that of the beta-catenin gene was six of 20 cases (30%). From these findings, it is concluded that nasal NKTCL in northeast China shared common features with that in Korea in the younger onset of disease compared to that in Japan and lower frequency of p53 gene mutations with infrequent exon 4 involvement compared to that in Japan and north China. These differences might be caused by migration of susceptible populations or some environmental confounding factors.

Increased Frequency of p53 Mutation in Sporadic Colorectal Cancer from Cigarette Smokers

Cigarette smoking has been shown to increase the risk of colorectal cancer. However, the relation between smoking and genetic alterations has not been clarified in this type of cancer. Mutations of p53, APC, beta-catenin and K-ras-2 genes were analyzed in colorectal carcinomas from 28 smokers and 33 non-smokers. Frequencies and types of mutations were compared between smokers and non-smokers. The frequency of carcinomas with p53 mutation was higher in smokers (20/28, 71%) than in non-smokers (15/33, 45%) (P = 0.037). The common type of mutation was single-base substitution including G:C to A:T transition in both groups (68% in smokers and 67% in non-smokers). With respect to G:C to A:T transitions, mutation at CpG sites was less frequent in smokers (9/15, 60%) than in non-smokers (10/10, 100%), whereas mutation at non-CpG sites was more frequent in smokers (6/16, 40%) than in non-smokers (0/10, 0%) (P = 0.028). The frequency of APC mutation was not significantly different between smokers (14/28, 50%) and non-smokers (15/33, 45%). No beta-catenin mutation was detected in carcinomas from smokers. K-ras-2 mutation occurred in smokers at a similar frequency (9/28, 32%) to that in non-smokers (13/33, 39%). Concerning pathological aspects, Dukes' A carcinomas were less frequent in smokers (11%) than in non-smokers (33%), whereas Dukes' D carcinomas were more frequent in smokers (25%) than in non-smokers (15%). The present results suggest that an increased frequency of p53 gene mutation, including G:C to A:T transitions at non-CpG sites, is associated with an increased risk of colorectal carcinogenesis in cigarette smokers.

Low Frequency of p53 Gene Mutations in Breast Cancers of Japanese-American Women

Differences in frequencies and patterns of somatic p53 gene mutations among racially and geographically diverse populations presumably reflect exposure to different mutagens or different responses to certain mutagens. On emigration to the United States, Japanese women experience, over several generations, a four- to fivefold increase in the incidence of breast cancer. To determine whether this increased incidence is associated with a change in the frequency and/or type of p53 mutation in their tumors, we examined paraffin-embedded samples of primary breast cancers from Japanese-American women in Los Angeles County, CA. Mutations in exons 5-9 and adjacent intronic regions of the p53 gene were identified and confirmed by direct sequencing. Seven mutations, including 5 missense, were detected in 44 primary breast carcinomas, a frequency of 16%. There were six transitions and one transversion. As expected, overexpression of p53 protein, detected by immunohistochemistry, occurred in tumors with missense mutations; tumors with nonsense or splice junction mutations had no detectable p53 protein. The frequency of p53 gene mutations showed no increase over that previously found in breast cancers of native Japanese women. The increased incidence of breast cancer in Japanese-American women is likely to be multifactorial in nature and warrants further studies.

Mutación del gen p53 en el cáncer de la vesícula biliar

Gallbladder cancer frequency and mortality renders it one of the most important neoplastic diseases in Chile. P53 tumor suppressor gene has been studied in most types of cancer, but there is scarce information about it in gallbladder cancer. To study the frequency of P53 gene mutation in gallbladder cancer in the ninth region of Chile. In 25 pathological samples of gallbladder cancer, the direct amplification and sequencing of p53 gene exons 5,6,7,8-8 was possible. Seventeen punctual mutations were observed in 13 cases (52%). There were 10 transitions, 5 transversions, one insertion (codon 194) and one deletion (codon 186). Eight cases had mutations in exon 5, six had mutations in exon 6, two had mutations in exon 7 and one had mutations in exons 8-9. In 14 of 25 cases, gene p53 protein was positive. When immunohistochemical expression of gene p53 protein was positive in more than 20% of cells, there was a high correlation between genetic alterations and immunohistochemical expression of the protein, with a specificity, sensitivity, positive and negative predictive values over 80%. P53 gene mutation is observed in a high proportion of gallbladder cancers at it can be accurately detected with conventional immunohistochemical techniques. The importance of this gene in the genesis of this carcinoma should be determined studying preneoplastic lesions and early carcinomas.

P53 gene mutation, tumor p53 protein overexpression, and serum p53 autoantibody generation in patients with breast cancer

Objectives: Autoantibodies against the p53 tumor suppressor protein have been detected in the serum of a proportion of patients with various cancers. The generation of such antibodies has been proposed to be due to either tumor p53 protein accumulation or to the type of p53 gene mutation. These hypotheses are examined in the present study. Design and methods: Using immunofluorometric assays, we studied 195 patients with primary breast cancer for the presence of p53 antibodies in serum and p53 protein accumulation in the corresponding tumor. Seventeen patients (9%) were p53 antibody-positive and 77 (40%) overexpressed p53. Ten of the 17 p53 antibody-positive patients had tumor p53 accumulation and 7 were negative for p53. Statistical analysis revealed a weak association between the presence of p53 antibodies and p53 protein accumulation (p = 0.05). Direct DNA sequencing of exons 1–11 of the p53 gene was performed for 16 p53 antibody-positive and 16 p53 antibody-negative patients. Results: Five of the seropositive and eight of the seronegative patients had a p53 gene mutation. Four of the five mutations in the p53 antibody-positive patients affected a Tyr residue, whereas none of the gene abnormalities in the seronegative patients had such an effect. Conclusions: We conclude that p53 antibodies tend to develop in patients with tumor p53 accumulation, but p53 accumulation is neither sufficient nor necessary for the generation of the immune response. Further, p53 antibody-positive patients do not have higher frequency of p53 gene mutations than p53 antibody-negative patients, but the former patient group is associated with a Tyr substitution in the protein product.

Immunohistochemical studies of colorectal cancers that developed following pelvic irradiation.

Radiation therapy is believed to be a predisposing factor in the development of carcinoma. During the period from 1974 to 1997, we treated five colorectal cancers in four patients who had undergone pelvic irradiation for cervical cancer. Radiation-induced changes in the remaining bowel were recognized in all of these patients. Of the five tumors, two were histologically diagnosed as mucinous adenocarcinoma, demonstrating a higher distribution than usual: To clarify the characteristics of the tumors, we examined the frequency of mutation in K-ras and p53 genes, and the proliferating cell nuclear antigen (PCNA) proliferation activity. The K-ras and PCNA stains did not show any clear characteristics of radiation-induced colorectal cancers in comparison with ordinary colorectal cancers; however, it was of interest that strongly positive staining was observed in our mucinous adenocarcinomas, even though a low frequency of p53 gene mutation has been reported in ordinary mucinous adenocarcinomas.