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T Soussi

Publications and source records attributed to T Soussi.

At least 109 records · Page 6Linked to original sources
PubMed1995

Serum p53 antibodies as early markers of lung cancer.

The p53 alteration is the most common alteration found in human cancer. It usually involves missense mutations that stabilize the p53 protein, which in turn accumulates, reaching levels detectable by immunohistochemistry. We and others have demonstrated that this overexpression of mutant p53 protein can induce a specific humoral response in cancer patients. This result was assessed by the presence of p53 antibodies in sera of patients with various types of cancers, whereas normal populations do not exhibit such antibodies. In lung cancer, the prevalence of p53 antibodies is high (30%) and is correlated with a very high rate of p53 mutations in this cancer (60-70%). We show that these antibodies are always present at the time of diagnosis, but never appear during tumour development, an observation strengthened by the fact that these antibodies are mostly IgG, corresponding to a secondary immune response. These results suggest that the humoral response is an early event and that p53 antibodies can be used as a precocious marker of p53 alteration before clinical manifestation of the disease.

Adult↗
PubMed1995

Antibodies against p53 protein in serum of patients with benign or malignant pancreatic and biliary diseases.

Specific markers for pancreatic or biliary cancer have been developed in the past few years. Ca 19-9 has a good sensitivity but it is also increased in benign cholestasis. Mutations in the p53 gene are commonly reported in pancreatic cancer and can be detected by a serological analysis. The aim of this work was to find out the sensitivity and specificity of this new assay in diagnosing cancer of the pancreas or of the bile ducts. The presence of antibodies against p53 was determined by an enzyme linked immunosorbent assay (ELISA) in 29 patients with pancreatic cancer, 33 with biliary tract cancer, and 33 with benign biliary or pancreatic diseases as controls. p53 Antibodies were detected in eight of 29 patients with pancreatic cancer (28%), in five of 33 patients with biliary tract (15%), and in one patient (3%) with stones of the common bile duct. The sensitivity and the specificity for the diagnosis of malignant biliary or pancreatic diseases were 21% and 96% respectively. It is concluded that the presence of p53 antibodies in the serum of patients with pancreatic and biliary diseases is specific for malignancy and independent from the presence of cholestatic disease.

Aged↗
PubMed1995

[Genetic alterations in localized cancers of the prostate: identification of a common region of deletion on the chromosome 18q].

Prostate cancer is one of the most common malignancies in men. Few authors have attempted to identify consistent genetic alterations at the molecular level in adenocarcinoma of the prostate, but those most frequently reported are loss of heterozygosity (LOH) involving chromosome arms 8p, 10q, 16q, and 18q and inactivation of the TP53 tumor suppressor gene. In order to determine if alterations frequently found in other adenocarcinomas (breast, ovarian, colorectal), including losses of genetic material from chromosome arms 1p, 3p, 7q, 8p, 11p, 17p, 17q, and 18q, are also involved in prostate cancer, we examined 20 localized early-stage prostate tumors. We detected no mutations of the TP53 gene. Allelic losses were found from 7q (33%), 8p (50%), 10q (20%), and 18q (33%). Furthermore, as the first step toward isolating tumor suppressor genes on 18q, we used six polymorphic markers and identified a small common deleted region between the chromosome 18 centromere and the D18S19 locus.

Aged↗
PubMed1994

Database and software for the analysis of mutations in the human p53 gene.

Mutations of the human p53 gene are of importance in the development of cancer. Perhaps 50% of all human cancers contain a mutation in the p53 oncogene and many laboratories are investigating mutations at this locus. In an effort to centralize and standardize the information regarding human p53 mutations, we have created a computerized database that contains information about DNA sequence alterations for > 3000 p53 mutants. Information on the cancer type, the origin of the cells, the specific mutation, the amino acid change, the literature citation, and other data are provided for each mutant. We have also produced a software package for the analysis of the p53 database. Routines have been developed for the analysis of single-base substitutions, including programs to (a) determine whether two mutational spectra are different, (b) display the number of mutations and mutable sites in each exon, (c) determine whether mutations show a DNA strand bias, (d) determine the frequency of transitions and transversions, (e) display the number and kind of mutations observed at each base in the coding region, (f) perform nearest neighbor analysis, and (g) display mutable amino acids in the p53 protein. The software runs only on IBM-compatible machines with MS-DOS. The software and p53 database are freely available via the Internet, using the remote file transfer protocol. These programs simplify the analysis of the rapidly increasing body of information about p53 mutations. The programs permit facile comparison between different p53 data sets, as well as the identification of mutational patterns that may be of importance to experimenters studying the mechanisms of mutation and the etiology of cancers.

Base Sequence↗
PubMed1994

3-Methylcholanthrene inactivates the p53 gene in Syrian hamster embryo fibroblasts by inducing a specific intronic point mutation.

The expression of the tumor suppressor gene p53 was studied in Syrian hamster embryo cells neoplastically initiated with a single dose of 3-methylcholanthrene. Ten randomly selected individual 3-methylcholanthrene-transformed colonies were established in culture independently. Eight of these cell lines contained levels of p53 mRNA similar to those in primary embryo cells (p53+ cell lines), as measured by Northern blot analysis of total RNA, whereas two of them (81C43 and 81C47) showed no detectable levels of p53 mRNA (p53- cell lines). However, Southern blot and karyotype analyses did not reveal any significant changes in copy number or gross rearrangements of the p53 gene in any of the p53- cell lines. A 3-kilobase genomic fragment cloned from p53- cells (81C47) containing both upstream and downstream promoters of the p53 gene was able to drive the expression of a CAT reporter gene when transfected into either p53+ or p53- cells. Furthermore, run-on assays performed on nuclei of p53- cells showed that the p53 gene was transcriptionally active, demonstrating that the genetic defect leading to the lack of p53 expression was not due to alterations in the promoter region. Detection of mRNA species corresponding to p53 mRNA precursors in Northern blot analysis of polyadenylated RNA from both p53+ and p53- cells indicated that the lack of p53 expression was not caused by mutations in the 3' regulatory region of the p53 gene affecting transcription termination and/or polyadenylation of p53 precursor mRNA. PCR amplification and nucleotide sequence analysis of extensive internal regions of the gene revealed that both p53- cell lines were homozygous for the same unique point mutation on the splice acceptor site of the fifth intron, a G to C transversion in the last nucleotide of the intron. The presence of this mutation in both p53- cell lines strongly suggests that it was induced specifically by 3-methyl-cholanthrene treatment and indicates that the resulting splicing malfunction may account for the lack of p53 gene expression.

Animals↗
PubMed1994

Analysis of the most representative tumour-derived p53 mutants reveals that changes in protein conformation are not correlated with loss of transactivation or inhibition of cell proliferation.

In an effort to correlate the biological activity of the p53 protein with its conformation, we analysed 14 p53 mutants representative of the most frequently observed protein alterations in human cancers, at codons 175, 248 and 273 (22% of all mutations thus far reported), all three of which contained a CpG dinucleotide. Strikingly, most of the mutants at codons 248 and 273 did not display any change in their conformation, as probed by monoclonal antibodies PAb240 and PAb1620 or by binding to hsp70 protein. For all 14 mutants tested, we found a strict correlation between the transactivation properties of p53, tested either on RGC sequences or using the WAF-1 promoter, and inhibition of cell proliferation. All these mutants showed nuclear localization. Several mutants, present at a low incidence in human tumours, displayed wild-type activity in all our assays, suggesting that the presence of a mutation is not strictly correlated with p53 protein inactivation in tumours. Further analysis of nine thus far undescribed p53 mutants at codon 175 revealed a wild-type or mutant behaviour. All these results suggest that the occurrence of a mutation is dependent on two criteria: (i) the mutability of a given codon, such as those containing a CpG dinucleotide; (ii) the resulting amino acids, eventually leading to synthesis of a p53 conferring a growth advantage on the cell.

Animals↗
PubMed1994

Can we predict solar ultraviolet radiation as the causal event in human tumours by analysing the mutation spectra of the p53 gene?

The tumour suppressor gene, p53, has proved to be one of the genes most often modified in human cancers. These alterations consist mainly of point mutations located in the evolutionarily conserved sequences which render the protein inactive for its normal biological functions. In fact the p53 gene presents nearly 300 potential mutation sites whose analysis should enable the correlation of specific mutation spectra with different causal agents in cancer development. In this study we have analysed the mutation spectrum of the p53 gene in skin tumours from normal individuals and repair-deficient xeroderma pigmentosum (XP) patients in comparison with mutations found in internal cancers. Point mutations are mainly GC-->AT transitions in skin tumours (74% in non-XP, 87% in XP), and also to a lesser extent in internal tumours (47%) where, however, they are mainly located at CpG (63%) sequences probably due to the deamination of the unstable 5-MeC. Moreover, mutations are targeted at py-py sequences in over 90% of skin tumours whereas the distribution of mutations in internal malignancies is proportional to the frequency of py-py sites (61%) and other sequences (39%) at mutable sites. Indeed, in XP skin tumours 100% of the mutations are targeted at py-py sequences and 55% of these are tandem CC-->TT transitions considered as a signature of UV-induced lesions. In skin tumours from normal individuals, 14% of the p53 mutations are double mutations and as in XP skin tumours all these are CC-->TT transitions. In contrast, internal tumours rarely contain tandem mutations (0.8%), and of these only 2/14 were CC-->TT transitions. Finally, nearly all (95%) of the mutations in XP are located on the non-transcribed strand while internal or non-XP skin tumours do not show this strand bias. Hence, the mutation spectrum analysed in XP skin tumours also demonstrates for the first time the existence of preferential repair in humans. In conclusion, the specificity of UV-induced p53 mutation spectra in skin tumours shows that this gene is a particularly appropriate candidate for the correlation of mutation spectra with specific damaging agents.

DNA↗
PubMed1994

Genetic alterations in localized prostate cancer: identification of a common region of deletion on chromosome arm 18q.

Accumulation of mutations in oncogenes and tumor suppressor genes transforms a normal cell into a malignant cell by allowing it to escape from normal control of growth. In prostate tumorigenesis, the current model envisages specific mutations of the TP53 tumor suppressor gene and loss of loci, detected by loss of heterozygosity (LOH), on chromosome arms 8p, 10q, 16q, and 18q. In order to determine if alterations frequently found in other adenocarcinomas (breast, ovarian, gastric, colorectal), including losses of genetic material from chromosome arms 1p, 3p, 7q, 8p, 11p, 17p, 17q, and 18q, are also involved in prostate cancer, we examined 20 localized early-stage prostate tumors. We detected no mutations of the TP53 gene. Allelic losses were found from 7q (33%), 8p (50%), 10q (20%), and 18q (33%). Furthermore, as the first step toward isolating tumor suppressor genes on 18q, we used six polymorphic markers and identified a small common deleted region between the chromosome 18 centromere and the D18S19 locus.

Alleles↗
PubMed1994

Analyses of p53 antibodies in sera of patients with lung carcinoma define immunodominant regions in the p53 protein.

Antibodies specific for human p53 were analysed in sera of lung cancer patients. We detected p53 antibodies in the sera of 24% (10/42) of patients with lung carcinoma. The distribution was as follows: 4/9 small-cell lung carcinomas (SCLCs), 2/18 squamous cell lung carcinomas (SCCs), 2/10 adenocarcinomas (ADCs) and 2/5 large-cell lung carcinomas (LCCs). p53 antibodies were always present at the time of diagnosis and did not appear during progression of the disease. Using an original peptide-mapping procedure, we precisely localised the p53 epitopes recognised by p53 antibodies. Immunodominant epitopes reacting with antibodies were localised in the amino and carboxy termini of the protein, similar to those found in breast carcinoma patients or in animals immunised with p53. In light of these data, we suggest that p53 antibodies occur via a self-immunisation process that is the consequence of p53 accumulation in tumour cells. p53 antibodies were also detected in two patients without detected malignant disease. One of these patients died 6 months later of lung carcinoma, suggesting that p53 antibodies may be a precocious marker of p53 alteration.

Adenocarcinoma↗
PubMed1994

Functional characterization of Xenopus laevis p53: evidence of temperature-sensitive transactivation but not of repression.

We have investigated the effect of Xenopus laevis p53 (Xp53) on transcription from a variety of promoters which are regulated by mouse p53 using a chloramphenicol acetyltransferase reporter system. Although Xp53 transactivated promoters that are up-regulated by mouse p53, it was unable to cause repression. This ability to transactivate gene expression was dependent on a temperature of 32 degrees C, and activity was lost at 37 degrees C. Temperature-sensitive transactivation was correlated with temperature-dependent binding of Xp53 to the adenovirus E1B58K protein. Despite the marked loss of transcriptional activation and binding to E1B58K at 37 degrees C, Xp53 was still capable of binding simian virus 40 large T antigen and inhibiting simian virus 40 origin-dependent DNA replication. These data show that Xp53 is temperature sensitive for N-terminal activities and suggest that the transactivation and repression "domains" of p53 are distinct.

Adenovirus E1B Proteins↗
PubMed1994

Effects of electrical brainstem stimulation on tinnitus.

The primary aim of the auditory brainstem implant (ABI), an investigational device, is to restore auditory sensations in neurofibromatosis-2 patients deafened by bilateral acoustic neuroma surgery. An electrode is placed on the dorsal cochlear nucleus after the tumor is removed through the translabyrinthine approach. This procedure was performed on 18 patients: 13 were completely deafferentated after bilateral tumor removal and had received the ABI during surgery on the second-sided tumor; 5 were implanted at first-sided tumor removal. Three of these 5 patients had usable hearing remaining on the side of the second acoustic neuroma and were stimulated only during laboratory sessions. All patients had tinnitus. We used a questionnaire to assess the effects of brainstem stimulation on this symptom. Of the 18 patients, one early patient deceased, and one patient with no follow-up was not included in this study. Six patients who were unable to use the ABI because of temporary hardware problems or side effects from electrical stimulation were also excluded. Thus, we studied 10 patients. Of 7 patients who used their implant daily, 6 reported noticeable tinnitus reduction; the ABI had no effect in the remaining case. Of 3 recently implanted patients who used this implant only during laboratory testing, one patient reported complete suppression of tinnitus, one described worse tinnitus, and one reported no effect.

Adolescent↗
PubMed1994

Mutations in p53 produce a common conformational effect that can be detected with a panel of monoclonal antibodies directed toward the central part of the p53 protein.

Human p53 displays two immunodominant regions localized in the amino and carboxy termini of the protein. Using a truncated p53 (residues 66 to 361), we selected eight new monoclonal antibodies directed to the central part of the protein. We identified the epitopes recognized by seven out of eight antibodies with a set of overlapping peptides. One of these antibodies had an epitope similar to PAb240, whereas the others recognized novel and diverse antigenic determinants. Using a series of 19 p53 mutants, we show that the behavior of several of the new monoclonal antibodies is similar to that of PAb240 despite their various epitope localizations. This suggests that different mutations in the p53 protein induce an overall conformational change that can be detected by various monoclonal antibodies directed toward the central part of the protein.

Amino Acid Sequence↗
PubMed1994

p53 immunolabeling in archival paraffin-embedded tissues: optimal protocol based on microwave heating for eight antibodies on lung carcinomas.

The prognostic value of p53 gene mutations is dealt with by several recent reports. However, retrospective assessment of p53 tumor status on archived samples has been prevented by p53 epitope alteration during routine fixation and embedding procedures. This study aimed at establishing a reproducible low-cost protocol to retrieve not only N-terminal, but also midregion and C-terminal, epitopes, with special attention to possible artifacts induced by epitope retrieval procedures. Using microwave heating, we compared the epitope retrieval efficiency of five solutions with eight commercial antibodies on 21 lung carcinomas for which frozen tissue and samples fixed with formalin and Bouin's liquid were available. All eight epitopes were retrieved, citrate buffer proving efficient for seven. PAb 240 epitope was restored by target unmasking fluid only. No false positivity was observed. Fixation-induced loss of p53 immunoreactivity was minimal for formalin (two of 10 tumors for one antibody each), more significant for Bouin (six of 10 tumors for one to five antibodies). On the other hand, staining intensity was maintained or even improved, and nonspecific staining reduced, through fixation. We conclude that p53 stabilization can be detected on routinely processed archival tumor samples with a reliability similar to that of frozen tissue by means of a microwave-based procedure and a panel of at least three antibodies, with epitopes on the N-terminal, C-terminal, and midpart of the molecule.

Antibodies, Monoclonal↗
PubMed1994

[The p53 gene and protein in bronchial carcinogenesis:from biological to clinical aspects].

The p53 gene codes for a nuclear phosphoprotein which is capable of modulating the expression of certain genes implicated in the regulation of cell division. The mutation of an allele on the p53 gene with loss of the healthy allele, in different tissues such as lung, larynx, bladder, liver, skin, colon and breast, which may or may not be exposed to chemical or physical carcinogens (tobacco, radon, ultraviolet, aflatoxin B1), is associated with the occurrence of cancer. Indeed, the mutated p53 protein loses its anti-proliferative properties favouring a de-regulation of cellular multiplication with the accumulation of genetic aberrations. The homozygous deletion of the p53 gene in germ cells in the members of certain family cancers (Li-Fraumeni syndrome) leads to an increased incidence of cancers in the child or young adult. The most frequent mutations of the p53 gene end in a stabilisation of the mutated protein with immuno-histochemical nuclear marking of the cells carrying such an alteration. In certain patients this stabilisation of the mutated protein ends in auto-immunisation with anti-p53 serum antibodies. Bronchial cancer is a cancer of which the mutations of p53 are the most frequent (45-65% of bronchial cancer) as result of the mutagenic effect of tobacco smoke. These mutations seem to be associated with a bad prognosis and indeed to chemo-and radiotherapeutic resistance. The early diagnosis of p53 alterations (in dysplastic lesions or tumours which are only slightly developed) would enable new therapeutic interventions in bronchial cancer such as gene therapy or radio-immunotherapy to either restore the p53 gene to normality or to eliminate the cells expressing the mutated p53 protein respectively.

Alleles↗