Association among p53 gene mutation, nuclear accumulation of the p53 protein and aggressive phenotypes in breast cancer

In order to reveal whether differences in the type and site of p53 gene mutations influence the function of the gene and tumor phenotype, we examined nuclear accumulation of the p53 protein immunohistochemically, loss of the other p53 allele by restriction-fragment-length polymorphism analysis, and histological grade of atypia in 52 breast-cancer tissue specimens in which the position and pattern of the mutation were identified. When mis-sense point mutations or deletions of 3n bases (n = 1, 2, ...), which did not cause a frameshift downstream, occurred within codons 110-180 or 234-285, containing highly conserved regions, the p53 protein was almost always (92%) accumulated in nuclei in a majority of the cancer cells. When these mutations occurred outside these regions, only 46% of the cases showed nuclear accumulation of the protein in a majority of cancer cells. In tumors with non-sense point mutations or deletion of 3n + 1 or 3n + 2 bases (n = 0, 1, 2, ...), which caused a downstream frameshift, nuclear accumulation of the p53 protein was absent in 93% of cases. Irrespective of the mutation site or pattern, a majority of cases showing p53 mutation revealed loss of heterozygosity on 17p13 (83%), which suggested they do not carry wild-type p53 allele, and the highest histological grade of atypia (90%). Regardless of differences in their protein-expression pattern, a majority of the p53 gene mutations were suggested to function in a recessive mode and to be involved in the development of histologically aggressive breast cancer.     

p53 mutation and tamoxifen resistance in breast cancer

A substantial portion of patients with estrogen receptor-positive breast cancer fail to respond to estrogen depletion or to the antiestrogen tamoxifen. The molecular changes that lead to tamoxifen resistance and estrogen-independent growth are unknown. To test the hypothesis that a p53 mutation could result in tamoxifen resistance and estrogen-independent growth, the MCF-7 cell line was transfected with p53 cDNA which was mutated at codon 179 (histidine to glutamine). MCF-7 is an estrogen receptor-positive, estrogen-dependent, tamoxifen-sensitive cell line with only wild-type p53. The presence of transfected mutant p53 cDNA was verified by the PCR, and overexpression of p53 protein was assessed by Western blotting. Five separate mutant-transfected clones were selected and tested in subsequent growth experiments. In monolayer culture, there was no consistent evidence of estrogen-independent growth or tamoxifen resistance in the mutant transfectants compared with vector-only controls or the parental cell line. In soft agar growth experiments, four of five mutant transfectants remained sensitive to tamoxifen in a dose-dependent manner. In the presence of wild-type p53, mutant 179 p53 protein does not result in estrogen-independent growth or tamoxifen resistance. These results do not exclude the possibility that other p53 mutational types could result in tamoxifen resistance, or that loss of the remaining wild-type allele may be necessary to result in this phenotype.     

p53 mutations and overexpressions in Japanese breast cancer

In this paper, we explore the use of a variety of familial transmission tests (and case-control analyses) to screen for allelic associations in simulated marker data of a quality (2 cM map) that will feasibly arise from genomic scans within the next 5-10 years. We demonstrate a form of the transmission-disequilibrium test extended to multiallele systems. The methods used were log-linear and related models implemented largely using standard statistical packages.     

Racial disparity in the association of p53 gene alterations with breast cancer survival

A significant black/white difference in breast cancer prognosis has been observed in the United States. Alterations of p53 tumor suppressor gene in breast cancer have been associated with poor prognosis. This study was designed to test the hypothesis that p53 gene alterations are related to the difference in prognosis between black and white breast cancer patients. Formalin-fixed paraffin-embedded breast tissue blocks were available from 45 black and 47 white patients for PCR-single strand conformation polymorphism analysis and DNA sequencing. The types of p53 gene alterations were compared between blacks and whites. Associations between p53 gene alterations and survival were also evaluated. Three missense, 2 nonsense, 1 microdeletion, 1 intron, and 4 silent mutations were detected in blacks, while 7 missense, 1 microdeletion, 1 silent mutation, and 3 polymorphisms were observed in whites. Among the point mutations, G:C to A:T transitions at non-CpG sites were found in 80.0% of blacks (8 of 10) and 62.5% of whites (5 of 8). Significantly poorer survival associated with p53 gene alterations was observed for blacks (P = 0.012), but not for whites. Black patients with p53 alterations had a significant 4-5-fold excess risk of death from breast cancer than those without p53 alterations. Adjustment for stage, age, tumor histopathology, receptor status, and adjuvant treatment did not change the excess risk. The findings suggest that the types of p53 gene alterations may contribute to the racial difference in breast cancer survival.     

p53 expression in breast cancer related to prognostic factors

In this article the results of molecular marker p53 examinations were presented in relation to the following established breast cancer prognostic factors: age, histologic type, histologic grade, lymph node involvement, tumor size as well as estrogen a progesterone receptor status. Twenty one percent of these primary breast cancer specimens exhibited the overexpression of p53 protein. Significant associations were found between p53 overexpression and younger age, high histologic grade and low content of estrogen and progesterone receptors. Identification of p53-positive breast carcinomas potentially represents a clinically useful indicator of breast cancer aggressiveness.     

Comparison of p53 gene mutation and protein overexpression in colorectal carcinomas

Immunocytochemistry (ICC) has been used routinely to stain for p53 overexpression in a range of human tumours. The underlying assumption has been that positive staining indicates a mutation in the p53 coding sequence. Recently, however, discordancy has been observed and the accuracy of ICC as a marker of p53 gene mutation has been questioned. In this study of 109 colorectal adenocarcinomas, we compared ICC staining with p53 gene mutations detected by single-strand conformation polymorphism (SSCP) analysis. Concordancy between the two techniques was found in 69% of tumours. ICC-positive/SSCP-negative cases accounted for 20% of tumours and ICC-negative/SSCP-positive cases for the remaining 11%. These results caution against the assumption that p53 protein overexpression is always associated with a gene mutation. Epigenetic phenomena may account for a significant proportion of ICC-positive tumours.     

Immunohistochemical detection of c-erbB-2 and p53 in benign breast disease and breast cancer risk

BACKGROUND: We studied the associations between c-erbB-2 protein overexpression and p53 protein accumulation in benign breast tissue and the risk of subsequent breast cancer. METHODS: We conducted a case-control study nested within the cohort of 4888 women in the National Breast Screening Study (NBSS) who were diagnosed with benign breast disease during active follow-up. Case subjects were the women who subsequently developed breast cancer (ductal carcinoma in situ [DCIS] or invasive carcinoma). Control subjects were matched to each case subject on NBSS study arm, screening center, year of birth, and age at diagnosis of benign breast disease. Histologic sections of benign and cancerous breast tissues were analyzed immunohistochemically. Information on potential confounding factors was obtained by use of a self-administered lifestyle questionnaire. RESULTS: Accumulation of p53 protein was associated with an increased risk of progression to breast cancer (adjusted odds ratio [OR] = 2.55; 95% confidence interval [CI] = 1.01-6.40), whereas c-erbB-2 protein overexpression was not (adjusted OR = 0.65; 95% CI = 0.27-1.53). The findings for c-erbB-2 and p53 did not differ among strata defined by menopausal status, allocation within the NBSS, history of breast disease, and whether the benign breast disease was detected at a scheduled screen or between screens. The results were also similar after exclusion of case subjects whose diagnosis of breast cancer occurred within 1 year of their diagnosis of benign breast disease and after exclusion of subjects with DCIS. CONCLUSIONS: p53 protein accumulation, but not c-erbB-2 protein overexpression, appears to be associated with an increased risk of progression to breast cancer in women with benign breast disease.     

High-frequency developmental abnormalities in p53-deficient mice

BACKGROUND: Several strains of mice carrying null mutations of the tumour suppressor gene p53 have been developed. It has been reported that homozygous mice from all of these strains develop normally to birth, but then succumb rapidly to neoplasia. RESULTS: Here, we report that a significant proportion of female p53-/- mice die during embryogenesis or in the period between birth and weaning, being subject to a spectrum of abnormalities. In a significant proportion (23%) of p53-/- female embryos, the normal process of neural tube closure failed, leading to exencephaly and subsequent anencephaly. Although this phenomenon was predominantly associated with females, we observed one affected male embryo. In addition to a spectrum of neural tube defects, many of these embryos exhibited a range of craniofacial malformations, including ocular abnormalities and defects in upper incisor tooth formation. We observed a significant reduction in the number of p53-/- female progeny of p53+/- x p53+/- matings, and also in an in utero analysis of the p53+/- female progeny of p53-/- x p53+/+ matings. When male mice were exposed to irradiation prior to mating, a significant increase in the rate of abnormality was seen in the progeny, which was specifically associated with p53 deficiency. CONCLUSIONS: We have identified a high rate of developmental abnormalities associated with p53 deficiency. This manifests itself as a spectrum of lesions, predominantly female-associated defects in neural tube closure. These defects may arise either because p53 plays a physiological role at the time of neural tube closure, or because of an abnormally high frequency of mutation within the haploid gametes of p53-null parents.     

p53 and colorectal cancer

Mutations of the p53 gene have been found in 380 of the 768 tumors (49.5%) included in the eight largest published series of colorectal cancer. Most point mutations of p53 change the conformation of the gene, and by stabilizing it make it detectable by immunohistochemistry. However, studies using both tests for p53 mutations and immunohistochemical methods found that the results of these two approaches were concordant in only 68% of cases. Conflicting data have been reported regarding the prognostic significance of positive p53 staining. Presence of a mutation is generally believed to indicate a poor prognosis.     

p53 gene therapy in vivo of herpatocellular and liver metastatic colorectal cancer

Tumor suppressor genes such as p53 contribute to the oncogenic process via loss-of-function mechanisms such as genetic mutation or complex formation with other cellular or viral proteins. p53 is mutated in approximately 50% of human tumors and has an important role in the genesis or progression of both colorectal and hepatocellular cancers. Colorectal cancer is leading cause of cancer mortality in the United States, whereas hepatocellular cancer is the leading worldwide cause of cancer death; the liver is a primary site of morbidity in both diseases. Because systemic tumor suppressor gene therapy is currently not feasible, we have chosen to develop a regional form of such therapy directed at primary or metastatic liver neoplasms. Gene replacement therapy with p53 is a promising new strategy to treat advanced human cancers.     

Expression of p53 protein has no independent prognostic value in breast cancer

A series of 392 female breast carcinomas was analysed immunohistochemically for expression of p53 protein with special emphasis on the role of p53 as an independent prognostic factor. Altogether, 54.8 per cent of the carcinomas expressed p53 protein, with the mean [standard error (SE)] fraction of positive nuclei being 17.1 per cent (1.2 per cent). Expression of p53 protein was independent of tumour metastasis at diagnosis, axillary lymph node status, tumour diameter, histological type, tubule formation, proportion of intraductal growth, margin formation, necrosis, DNA ploidy, and S-phase fraction. A high fraction of p53-positive nuclei was significantly related to patient age under 70 years, high grade, severe nuclear pleomorphism, dense infiltration of tumour by lymphocytes, high mitotic index, and high apoptotic index (for all, P < 0.05). Impaired survival probability in the entire cohort (P = 0.05) and in the axillary lymph node-positive (ANP) tumours (P = 0.015) was associated with a fraction of p53-positive nuclei less than 25 per cent, while in the axillary lymph node-negative (ANN) tumours, expression of p53 had no prognostic value. In multivariate analysis, independent prognostic predictors included axillary lymph node status, tumour diameter, and mitotic index. In the ANN tumours, tumour diameter, fraction of p53-positive nuclei, and tumour grade were independent prognostic factors, whereas in the ANP tumours, diameter and mitotic index were the two independent prognostic factors. The results suggest that abnormal expression of p53 protein is only a weak independent prognostic factor in female breast cancer.     

Detection of p53 gene mutation in paraffin-embedded asbestos-related lung cancer tissue

The rearrangement of immunoglobulin heavy chain gene (IgH) and T cell receptor gamma gene (TcR gamma) was studied in 30 patients with acute lymphoblastic leukemia (ALL) by the polymerase chain reaction (PCR). 19 cases was found to have rearrangement of IgH gene, 12 of TcR gamma. Most of IgH rearrangement was characterized by one or two specific bands while some had more than two. Rearrangement of TcR gamma gene appeared as one specific band. A slight difference in number, size and lightness of bands was found among the patients. 4 different kinds of rearrangement were observed in the detection of IgH rearrangement in combination with TcR gamma gene. The rearranged patterns of IgH and TcR gamma gene as well as the clinical significance were discussed.     

p53 tumour suppressor gene mutations in benign prostatic hyperplasia and prostate cancer

OBJECTIVE: Seminal vesicle cysts combined with ipsilateral renal agenesis represent a rare urological anomaly. We searched the literature to review the clinical presentation, diagnosis and therapeutic treatment options of this anomaly. METHODS: A pooled analysis was performed of 52 cases of seminal vesicle cysts combined with ipsilateral renal agenesis, including our own observation. The evaluation included: patient age at diagnosis, race, laterality (R/L), presence of ureteral remnant in the cyst, presenting symptoms, diagnostic examinations, treatment and outcome. RESULTS: The mean age at diagnosis was 30.2 years. The majority presented in the 2nd, 3rd and 4th decade of their lives. Only 2 patients (4%) were of African origin, all others were Caucasians. The distribution R:L was 2:1. Ureteral remnants were present in 14 patients (27%). The most common symptoms were: dysuria (37%), frequency (33%), perineal pain (29%), epididymitis (27%), pain following ejaculation (21%) and scrotal pain (13%). Infertility was found in 9 patients (17%). The cyst was palpable by digital rectal examination in 79%. All patients underwent intravenous urography, and 88% underwent cystoscopy. Other frequently performed investigations are: ultrasonography (27%), CT scanning (27%), vasovesiculography (46%) and urethrocystography (23%). The final treatment was open surgery in 74%, aspiration in 6%, transurethral deroofing of the cyst in 6% and spontaneous rupture in 4%. In 6% no treatment was given and in 4% the treatment is unknown. All patients were free of symptoms after open exploration. The success rates after transurethral deroofing and aspiration were 75 and 30% respectively. CONCLUSION: Seminal vesicle cysts combined with ipsilateral renal agenesis are a rare urological anomaly, occurring in men in the 2nd to 4th decade of their life. They present with symptoms of bladder irritation and obstruction and with pain in the perineum and scrotum. Epididymitis is frequently found. The diagnostic work-up consists of a digital rectal examination, transrectal and abdominal ultrasonography, CT scan and a cystoscopy. Open surgery and transurethral deroofing of the cyst give excellent results (100 and 75% cure respectively). Aspiration of the cyst should only be used for diagnostic purposes.     

p53 protein expression in breast cancer as related to histopathological characteristics and prognosis

Reaction of Klebsiella aerogenes urease with diethylpyrocarbonate (DEP) led to a pseudo-first-order loss of enzyme activity by a reaction that exhibited saturation kinetics. The rate of urease inactivation by DEP decreased in the presence of active site ligands (urea, phosphate, and boric acid), consistent with the essential reactive residue being located proximal to the catalytic center. The pH dependence for the rate of inactivation indicated that the reactive residue possessed a pKa of 6.5, identical to that of a group that must be deprotonated for catalysis. Full activity was restored when the inactivated enzyme was treated with hydroxylamine, compatible with histidinyl or tyrosinyl reactivity. Spectrophotometric studies were consistent with DEP derivatization of 12 mol of histidine/mol of native enzyme. In the presence of active site ligands, however, approximately 4 mol of histidine/mol of protein were protected from reaction. Each protein molecule is known to possess two catalytic units; hence, we propose that urease possesses at least one essential histidine per catalytic unit.     

Relationship of p53 molecular abnormalities with flow cytometry and growth factor receptor content in lung cancer

The nucleotide sequence of the 3.5-kb right junction fragment of the streptococcal conjugative transposon Tn5252 was obtained. The DNA fragment was found to carry four putative genes one of which displayed a high degree of similarity to prokaryotic 5C-cytosine methyltransferases carrying multiple sequence specificities. No cognate endonuclease gene was detected in the sequenced DNA. Purified methylase polypeptide synthesized in a T7 promoter-controlled overexpression system was found to lack methylase activity while the cell extracts of host cells containing the recombinant plasmid carrying the methylase gene were active. In vivo mutations in the methylase gene did not seem to affect the transferability of the element.     

p53 and prognosis in colorectal cancer

Treatment of rat liver arginase with N-bromosuccinimide results in modification of six tryptophan residues per enzyme molecule and is accompanied by loss of catalytic activity (E. Ber and G. Muzynska (1979) Acta Biochim. Pol. 26, 103-114). In order to probe the chemistry of N-bromosuccinimide inactivation and the role of tryptophan residues in catalysis, the two tryptophan residues of rat liver arginase, Trp122 and Trp164, have been separately mutated to phenylalanine using site-directed mutagenesis of the protein expressed in Escherichia coli. Both single Trp -> Phe mutant enzymes have kinetic parameters nearly identical to those for the wild-type enzyme. Treatment of native, wild-type, and each of the Trp -> Phe mutant enzymes with N-bromosuccinimide results in loss of absorbance at 280 nm and is accompanied by a loss of catalytic activity. However, treatment of the wild-type enzyme with N-bromosuccinimide in the presence of the arginase inhibitors NG-hydroxy-L-arginine or the combination of L-ornithine and borate protects against inactivation, even though tryptophan residues are modified. Treatment of the H101N and H126N mutant arginases with N-bromosuccinimide also results in loss of catalytic activity and modification of tryptophan residues. In contrast, the H141N mutant arginase is not inactivated by N-bromosuccinimide, indicating that His141 is the critical target for the N-bromosuccinimide inactivation of the enzyme.