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Biomedical subjects

N Janin

Publications and source records attributed to N Janin.

At least 19 recordsLinked to original sources

[20 years of progress in dissecting mechanisms of oncogenesis. Relations between magic of science and requirements of medicine].

In the last twenty years, our understanding of carcinogenesis has evolved from a description of the natural history of cancer development, a conception inherited from Darwin, to the dissection of the underlying molecular mechanisms leading to phenotypic changes in cells, a neodarwinian interpretation. Most scientists agree that random germ cell mutations enhancing cell survival and reproduction capacities play a major role in the evolution of species and that carcinogenesis progresses from acquisition of genetic anomalies which alter the normal function of oncogens or antioncogens. Since the discovery of src, the first oncogen to be identified twenty years ago, and more recently the discovery of antioncogens such as p53, hopes and expectations have grown steadily, and passionately, often far beyond reason dietated by the real world of clinical medicine. Yet curiously, many clinicians hesitate to express one essential point: advances in science and technology, is not equivalent to advances in medicine. It is our responsibility to resist the illusion of progress, for this illusion turns out to have a negative impact in our patients. To paraphrase the French philosopher André Comte-Sponville, the power conferred by the exercise of medicine is not based solely on scientific knowledge, but also on human compassion.

Humans

Circulating anti-p53 antibodies in esophageal cancer patients are found predominantly in individuals with p53 core domain mutations in their tumors.

Serum antibodies reacting with the tumor suppressor protein p53 have been detected previously in cancer patients with a variety of neoplasms. Two initial (although insufficient) prerequisites for a B-cell response to occur have been proposed: p53 protein accumulation in the tumor or a mutant p53 gene, or both. We have examined 65 esophageal cancer cases (42 from Guangzhou and Shenyang, People's Republic of China, and 23 from Paris, France) to obtain a prevalence estimate of anti-p53 antibodies for this type of cancer and to define the relationship of p53 tumor status to B-cell immune response. Sera were analyzed in a triplicate assay (enzyme-linked immunoassay, immunoprecipitation, and immunoblot) for anti-p53 antibodies. Tumor DNA was screened for mutations in exons 5-8, and tumor tissue was examined by immunohistochemistry for abnormal p53 protein accumulation. p53 mutations were found in 36 (58%) of 62 cases analyzed. Sixteen patients (25%) had circulating antibodies to the tumor suppressor protein. All but two (88%) of the tumors from seropositive cases had a mutation in the DNA binding region of the p53 gene, and with one exception, these tumors also showed nuclear accumulation of the p53 protein. In contrast, tumor mutations were found in just 22 (46%) of the 48 individuals in whom we did not detect anti-p53 antibodies. Among the 22 seronegative cases for which we found no tumor mutations, 11 revealed p53 protein accumulation by immunohistochemical analysis. Thus, circulating anti-p53 antibodies may be present in one-fourth of esophageal cancer patients, most of whom also would be expected to have a p53 gene mutation in their tumors. Patients without such mutations appear considerably less likely to mount a B-cell response to the p53 tumor suppressor protein than those that do (P < 0.01).

Adult

Truncation at conserved terminal regions of BRCA1 protein is associated with highly proliferating hereditary breast cancers.

The existence of two subgroups of BRCA1-associated breast cancer (BC) families has been recently posited: the first with highly proliferating tumors, and the second composed of cases with a low proliferation rate. Our aim was to test whether the proliferation rate of BRCA1-associated breast cancers was affected by the site of the germ line mutation in the BRCA1 gene. We analyzed the distribution of the mitotic index, a histoprognostic grade component shown to segregate in families, matching for germ line mutation location in a series of 28 breast cancers from 20 kindreds. We observed a prevalence of highly proliferating tumors when the mutation occurs in the two terminal conserved domains of the BRCA1 protein, ie., in the amino and carboxyl termini (P = 0.0024). Our data provide evidence for a genotype-phenotype correlation and along with their strong conservation during evolution argue for the importance of these two regions in the control of mammary cell growth.

Alleles

Deregulated apoptosis in ataxia telangiectasia: association with clinical stigmata and radiosensitivity.

Ataxia telangiectasia (AT) is a recessive genetic disease featuring neurodegeneration, immunodeficiency, chromosomal instability, radiation hypersensitivity, and increased predisposition to cancer. Reduced or delayed induction of the tumor suppressor protein p53 after gamma -irradiation was reported. These characteristics may be compatible with an inability to correctly regulate apoptosis. We show here that AT lymphocytes and EBV-transformed lymphoblasts demonstrate a significantly higher level of spontaneous apoptosis, whereas ionizing radiation-induced apoptosis is reduced compared to normal cells. However, neither AT nor normal primary fibroblasts undergo apoptosis after irradiation. Consequently, we conclude that the radiosensitivity of the AT cells is not related to an increased apoptotic response. Finally, we show that SV40-transformed AT fibroblasts undergo gamma- ray-induced apoptosis, while SV40-transformed normal cells do not. This result raises the question of the physiological relevance of the latter cellular model with respect to the AT phenotype.

Apoptosis

Primary proliferative T cell response to wild-type p53 protein in patients with breast cancer.

Mutations in the p53 tumor suppressor gene are the most frequent genetic alterations found in human tumors. There are mainly point mutations that lead to single amino acid substitutions. The mutated proteins have a longer half-life than wild-type p53 and accumulate in the nucleus of tumor cells. Anti-p53 antibodies have been found in sera of patients with several types of cancers including breast cancer. This report describes a T cell immune response in three patients with breast tumors who had mutated p53 gene and accumulated p53 protein. All showed a humoral response to p53 protein and the T cells of these patients recognized the wild-type p53 protein and proliferated in response to it. The data reported here are relevant to the immune processes leading to autoimmunity and have a bearing on anti-p53 vaccine development in tumor immunology.

Antibodies

[Genetic predisposition to cancer].

This review focuses on the genetics of inborn predisposition to the development of cancer. The gene defects responsible for the majority of the most common syndromes of inherited predisposition to cancer have been deciphered during the last five years. These discoveries have shown that the genetics of most of these inherited forms of cancer is remarkably simple: the mechanism underlying the risk of cancer is precisely the one proposed by Knudson to explain the inherited forms of retinoblastoma. Only a small minority of the cancers are imputable to inherited mutations causing a very high risk of cancer. However, low penetrance susceptibility genes, mainly acting as environmental risk modifiers, are probably involved in the development of the majority of cancers. As much as possible, we will consider the immediate and long term possible repercussions on everyday medical practice of these advances in basic understanding of genetic cancer risks.

Genetic Counseling

High-dose ifosfamide: circumvention of resistance to standard-dose ifosfamide in advanced soft tissue sarcomas.

PURPOSE: The study was designed to assess the toxicity and activity of high-dose ifosfamide (HDI) administered by continuous infusion at a dose of 4 g/m2/d over 3 days every 4 weeks in adult patients with advanced soft tissue sarcomas (ASTS) pretreated with doxorubicin and/or a standard-dose ifosfamide (SDI)-containing regimen. PATIENTS AND METHODS: Between January 1991 and November 1993, 40 patients with progressive ASTS were entered onto the study. Twenty-eight patients had been pretreated with a multidrug regimen that contained SDI and were classified as follows: SDI-refractory (n = 21), SDI-resistant (n = 2), and indeterminate SDI-sensitive (n = 5). Patients were treated until progression or major toxicity. RESULTS: One hundred forty-seven cycles of HDI were administered. Neutropenia was dose-limiting, with 100% of patients experiencing grade 3 to 4 toxicity and 12 admissions for febrile neutropenia (30% of patients). Neurotoxicity (17% of patients) was significantly associated with acute renal failure (n = 4) (P < .001), grade 4 thrombocytopenia (P < .01) and febrile neutropenia (P = .048). Chronic renal toxicity (n = 4) was significantly associated with retroperitoneal masses and/or prior nephrectomy (P = .008). Partial responses (PRs) were observed in 12 of 36 assessable patients (33%) and eight patients (22%) experienced disease stabilization. All but one response occurred in patients pretreated with SDI, with five PRs among SDI-refractory patients. Leiomyosarcomas appear resistant to HDI. The median response duration was 8 months (range, 6 to 13+) and the median overall survival time was 12 months. CONCLUSION: The activity of HDI in these pretreated ASTS patients and the apparent circumvention of SDI resistance suggest a real dose-response relationship for ifosfamide and deserve further evaluation. Although toxic, this treatment appears feasible and manageable using routine clinical support. Since prophylaxis of ifosfamide-induced renal damage remains unknown, frequent monitoring of renal and tubular functions during therapy is highly recommended.

Adult

Correlation between p53 gene expression and tumor-cell proliferation in oropharyngeal cancer.

The aim of our study was to analyze the correlation between tumor-cell kinetics measured in vivo and p53 gene expression in a series of 49 oropharyngeal cancers. The duration of the S phase (TS), the labelling index (LI) and the potential doubling time (Tpot) were obtained by flow-cytometry measurements of a tumor biopsy obtained after i.v. injection of 200 mg bromodeoxyuridine into patients. An adjacent section of the same samples was studied by immunohistochemistry for the detection of p53 protein. Over-expression of the p53 protein, as defined by strong p53 immunostaining of tumor nuclei, was found in 23/49 of the samples. Aneuploid tumors showed a higher LI, a shorter Tpot and a higher proportion of p53 gene over-expression. A significant correlation was seen between p53 over-expression and short Tpots. Indeed 87.5% of the tumors with a very short Tpot (< or = 3 days) had p53 over-expression, as compared with 27% of tumors with a longer Tpot (> 3 days). Our data strongly suggest that over-expression of the p53 gene is associated with rapid tumor-cell proliferation in this type of cancer.

Aged

[Introduction to the process of oncogenesis: cancers are somatic genetic diseases].

Cancers are the most frequent and at the same time the most complicated of somatic genetic diseases. Technical progress in the last fifteen years has enabled to analyse the acquired genetic abnormalities found in the vast majority of cancers. This molecular dissection of cancer has led to an understanding of this disease that can basically be viewed as a rupture of the balance between two class of genes, the oncogenes and the antioncogenes. This article defines the properties of these cancer genes and gives through a few examples an insight into the various mechanisms of cancerogenesis.

Genes, Tumor Suppressor

Epidermolytic palmoplantar keratoderma cosegregates with a keratin 9 mutation in a pedigree with breast and ovarian cancer.

Epidermolytic palmoplantar keratosis (EPPK) cosegregates with breast and ovarian cancers in a large French pedigree, raising the possibility that a single genetic mutation might cause these conditions and offering a potential lead to the identification of a hereditary breast/ovarian cancer gene. We have performed linkage analysis and show that the EPPK locus lies on the long arm of chromosome 17 near the type I keratin gene cluster and the proposed breast cancer gene (BRCA1). The type I keratin 9 gene has been partially sequenced in four affected individuals. A single base mutation within the rod domain of the protein cosegregates with EPPK in all affected individuals tested. Although inheritance of this mutation is likely responsible for EPPK, it is unlikely to be the cause of the breast and ovarian cancer.

Adolescent

Stargardt's disease is not allelic to the genes for neuronal ceroid lipofuscinoses.

Stargardt's disease is an autosomal recessive condition characterised by a rapid and bilateral loss of central vision at around 7 to 12 years, with typical changes in the macular and perimacular region. It is one of the most frequent causes of macular degeneration in childhood and accounts for 7% of all retinal dystrophies. Considering that inclusions of lipofuscin-like substances are observed in retinal pigmentary cells of patients with Stargardt's disease on the one hand, and that the early symptoms of neuronal ceroid lipofuscinosis (CLN3) are suggestive of Stargardt's disease on the other hand (age of loss of visual acuity, appearance of the fundus), we decided to test allelism of Stargardt's disease with the infantile (CLN1) and juvenile forms of neuronal ceroid lipofuscinosis (CLN3), which map to chromosomes 1p32 and 16p12-p11 respectively. Using highly informative microsatellite DNA markers in eight multiplex families, we were able to exclude Stargardt's disease from the vicinity of the CLN1 and CLN3 loci. These results strongly reject the hypothesis of allelism of Stargardt's disease with the neuronal forms of ceroid lipofuscinosis.

Alleles

Analysis of p53 antibodies in patients with various cancers define B-cell epitopes of human p53: distribution on primary structure and exposure on protein surface.

p53 antibodies have been found in sera of patients with breast and lung carcinomas and in children with B-lymphomas. We report here the presence of p53 antibodies in sera of patients with 11 different types of cancer. The frequency of seropositives for p53 varied among the different types of cancer, but a correlation with the frequency of p53 gene alteration was established. Using a powerful peptide enzyme-linked immunosorbent assay, we demonstrated that the immune response of patients with p53 antibodies was restricted to a small subset of peptides localized in the amino and carboxy termini of p53, whatever the type of cancer. Given the similarities of the patterns of immune responses in patients with p53 antibodies and animals hyperimmunized with human p53, we propose that the p53 humoral response is the result of a self-immunization process which is itself the consequence of p53 protein accumulation in tumor cells.

Amino Acid Sequence

A gene for Stargardt's disease (fundus flavimaculatus) maps to the short arm of chromosome 1.

Stargardt's disease (fundus flavimaculatus) is one of the most frequent causes of macular degeneration in childhood and accounts for 7% of all retinal dystrophies. It is an autosomal recessive condition characterized by a bilateral loss of central vision occurring at age 7-12 years. Genetic linkage analysis of eight families has assigned the disease locus to chromosome 1p21-p13. Multipoint linkage analysis and haplotype analysis has allowed us to establish the best estimate for location of the gene over the locus D1S435 (maximum lod score of 12.66). Our results are consistent with the genetic homogeneity of this condition.

Child

Simple sequence repeat polymorphism within the p53 gene.

This report describes a new polymorphism, in intron 3 of the p53 gene, which consists of a single repeat of 16 nucleotides, absent in the published wild-type p53 gene sequence. In the Caucasian population tested (n = 82), 28% of individuals were heterozygotes for this polymorphism. Using PCR-based analysis, we were able to demonstrate p53 allelic losses in three of six breast tumors from heterozygote patients tested.

Base Sequence

PCR-assisted localization of the human SRPR gene.

A polymerase chain reaction (PCR)-based assay has been designed that detects the presence of the human signal recognition particle receptor (SRPR) gene in inter-species somatic cell hybrids. By using hybrids containing various fragments of chromosome 11q, SRPR has been mapped to a chromosomal region flanked by the 11q23 and 11q24 breakpoints associated with the constitutional and neuroepithelioma (11;22) translocations, respectively.

Base Sequence

Recovery of pefloxacin in saliva and feces and its action on oral and fecal floras of healthy volunteers.

Pefloxacin, a new fluoroquinolone, was given to 10 volunteers in single 400-mg oral doses repeated at 12-h intervals during 7 days. Serum, saliva, and feces samples were collected before and at appropriate intervals after the initiation of treatment. Drug concentrations were determined by bioassay. Qualitative and quantitative analyses of the saliva and fecal floras were performed. Mean concentrations in saliva (3.46 micrograms/ml on day 1 and 7.54 micrograms/ml on day 7) were closely related to levels in serum. High concentrations of pefloxacin were found in the feces (645 micrograms/g on day 8). No modification of oral flora was observed. In the fecal flora, members of the family Enterobacteriaceae were eliminated between days 2 and 8. The alterations in streptococci and anaerobic flora were not significant; Bacteroides fragilis was more resistant to pefloxacin after treatment. Clostridium difficile was not detected, and there was no overgrowth by yeasts. No side effects were observed.

Bacteria

Prevalence of anti-Legionella antibodies in a healthy population and in patients with tuberculosis or pneumonia.

The prevalence of antibodies to 13 antigens of Legionellaceae were compared in three populations: 583 blood donors, 140 tuberculosis patients and 66 patients with acute non Legionellosis pneumonia. Antibody levels were determined by indirect immunofluorescence (IFA) using formalized antigens prepared from bacteria developed in embryonated hen yolk sac. The very weak prevalence of anti L. pneumophila antibodies in a healthy population [almost nil for serogroups 2, 3, 4 and 5; 1.5% for serogroup 6, maximum of 2.5% for serogroup 1 (titres of 16)] confirms the positive and presumptive criteria that have been recommended by Centers for Disease Control (CDC). But as regards the other Legionellae studied, these criteria cannot be applied owing to the prevalences that are higher in healthy populations (until 14.5% with levels of 16-32 and 1% with levels of 64-128 for L. bozemanii) and clearly amplified in tuberculosis patients and in acute pneumonia. Although the significance of these antibodies remains to be discussed, with formalized antigens, it seems reasonable as regards these species to assign a threshold of 256 for the presumptive and positive criteria following seroconversion.

Adult