A rodent model for Wilms tumors: embryonal kidney neoplasms induced by N-nitroso-N'-methylurea.

Embryonal kidney cell tumors develop in rats given the alkylating agent N-nitroso-N'-methylurea as neonates. These tumors resemble the childhood Wilms tumors in their histopathology. Deletions and mutations in the Wilms tumor suppressor gene, WT1, are present in up to 6% of childhood nephroblastomas.

Frequent p53 gene mutations and novel alleles in familial breast cancer.

Mutations in the p53 gene were detected in 58% of tumor DNAs of patients with a family history of breast cancer (FHBC) compared to 13% with sporadic breast cancer. Seven of 18 FHBC tumors contained the same G to C transversion in codon 156. Novel alleles of altered length were seen in one or more loci on chromosome 17 in 15 of 18 patients with FHBC but only in a single locus in 8 of 14 patients with sporadic breast cancer.

Wild-type p53 suppresses the malignant phenotype in breast cancer cells containing mutant p53 alleles.

We have examined the effect of expression of a retrovirally mediated wild-type (wt) p53 allele on the neoplastic properties of five human breast cancer cell lines expressing mutant p53. After infection with the retroviral vector Lhp53RNL expressing both the neomycin phosphotransferase gene and the wt p53 gene, the ability of infected cells to form colonies in G418 selective medium was markedly reduced and their morphology demonstrated changes toward a flattened and enlarged phenotype. Employing a high multiplicity of infection (MOI) with Lhp53RNL without neoR selection, the replication of wt p53-reconstituted cells was greatly reduced.

RNA editing in the Wilms' tumor susceptibility gene, WT1.

Rat kidney WT1 cDNAs contain either a thymidine or a cytosine residue at position 839. Genomic WT1 DNA contains only T839. To explain these results, we propose the WT1 transcript undergoes RNA editing in which U839 is converted to C, resulting in the replacement of leucine 280 in WT1 by proline.

Molecular cloning of rat Wilms' tumor complementary DNA and a study of messenger RNA expression in the urogenital system and the brain.

In an effort to study the molecular basis of kidney development and carcinogenesis, we isolated complementary DNA clones of the rat homologue of the human Wilms' tumor gene, WT-1. When compared to the predicted sequence of the human WT-1 polypeptide, the rat WT-1 amino acid sequence is highly conserved (> 97%), except for the loss of one amino acid. In situ mRNA hybridization experiments localized WT-1 expression to the glomerular cells in the kidney during embryogenesis and the Sertoli cells of the testis.

Mutations in p53 as potential molecular markers for human breast cancer.

Based on the high incidence of loss of heterozygosity for loci on chromosome 17p in the vicinity of the p53 locus in human breast tumors, we investigated the frequency and effects of mutations in the p53 tumor suppressor gene in mammary neoplasia. We examined the p53 gene in 20 breast cancer cell lines and 59 primary breast tumors. Northern blot analysis, immunoprecipitation, and nucleotide sequencing analysis revealed aberrant mRNA expression, over-expression of protein, and point mutations in the p53 gene in 50% of the cell lines tested.

Vector PCR.

A strategy employing PCR technology to facilitate the amplification of DNA segments inserted in plasmid vectors is described. Nine oligonucleotide primers specific for vector sequences bracketing cloning sites in seven commonly used vectors were designed. We used these primers for the amplification of 25 different inserts ranging in size from 0.

Generation of monoclonal antibodies specific for ras p21 Glu-12 oncoproteins: detection in carcinogen-induced mammary carcinomas.

ras genes have been shown to become oncogenes by single point mutations which result in amino acid substitutions that affect either their GTPase activity (positions 12, 13, 59, 61) or their affinity for GTP and GDP. Ras oncogenes and their corresponding proteins have been described in a variety of human cancers as well as in animal tumors induced by physical and chemical carcinogens. One of these animal tumor systems involves the induction of mammary carcinomas in rats by a single dose of N-nitroso-N-methylurea (NMU), a methylating carcinogen.

Multistage prostate carcinogenesis: the role of hormones.

Prostate cancer is the most frequently occurring non-skin cancer in men in the U.S.A.

Frequent activation of the Ki-ras oncogene at codon 12 in N-methyl-N-nitrosourea-induced rat prostate adenocarcinomas and neurogenic sarcomas.

Rat neoplasms induced by methylating carcinogens frequently contain ras genes activated by a single point mutation. Rat prostatic tumors induced by a combination of a single injection of N-methyl-N-nitrosourea (MNU) and long-term treatment with testosterone were examined for the presence of such activating point mutations in ras genes. These tumors, which arose exclusively in the dorsolateral prostate, included both adenocarcinomas and sarcomas.

Activation of H-ras oncogenes in preneoplastic mouse mammary tissues.

The mammary hyperplastic outgrowth (HOG) line C4, resulted from serial transplantation of a hyperplastic alveolar nodule which arose in a dimethylbenz(a)anthracene (DMBA) treated mouse. The immortalized C4 outgrowth line, on transplantation into syngeneic mice, develops as preneoplastic, hyperplastic outgrowths and subsequently into malignant carcinomas after a long latent period (greater than 6 months). Treatment of mice carrying C4 HOG transplants with DMBA resulted in a reduced latent period for tumor development (less than 3 months) and an increased tumor incidence.

An experimental analysis of cancer: role of ras oncogenes in multistep carcinogenesis.

Carcinogen-induced animal tumor models are invaluable resources for studies aimed at understanding the participation of ras oncogenes in multistep carcinogenesis. Mutationally activated ras oncogenes are frequently detected in chemically induced animal tumors. The nature of the mutations in ras oncogenes reflects the chemical specificity of the carcinogen, implying that the carcinogen interacts with ras sequences.

Activation of ras oncogenes preceding the onset of neoplasia.

The identification of ras oncogenes in human and animal cancers including precancerous lesions indicates that these genes participate in the early stages of neoplastic development. Yet, these observations do not define the timing of ras oncogene activation in the multistep process of carcinogenesis. To ascertain the timing of ras oncogene activation, an animal model system was devised that involves the induction of mammary carcinomas in rats exposed at birth to the carcinogen nitrosomethylurea.

Transforming c-Ki-ras mutation is a preneoplastic event in mouse mammary carcinogenesis induced in vitro by N-methyl-N-nitrosourea.

Mouse mammary epithelial cells can be transformed in primary cultures to preneoplastic and neoplastic states when treated with N-methyl-N-nitrosourea (MNU). Mammary carcinomas arising from MNU-induced hyperplastic alveolar nodules (a type of mouse mammary preneoplastic lesion) contained transforming c-Ki-ras genes when examined by the NIH 3T3 focus assay. Hybridization of allele-specific oligonucleotides to c-Ki-ras sequences amplified by the polymerase chain reaction demonstrated the presence of a specific G-35----A-35 point mutation in codon 12 in each of the NIH 3T3 foci as well as the mammary carcinomas.

Specific patterns of oncogene activation in transplacentally induced tumors.

Transplacental exposure of rats to a single dose of the direct acting carcinogen methylnitrosourea (MNU) results in the induction of a variety of neoplasias of neuroectodermal, epithelial, and mesenchymal origin. Molecular analysis of the oncogenes present in these tumors revealed a striking degree of tissue specificity. neu oncogenes were found to be reproducibly activated in tumors derived from the peripheral nervous system (PNS), but not in those arising from the central nervous system (CNS).

Parallel cousin marriages in Madras, Tamil Nadu: new trends in Dravidian kinship.

The frequency distribution of various consanguineous marriages was studied in the city of Madras, Tamil Nadu, South India. Parallel first cousin marriages (PFC) were found to occur in appreciable frequencies in all caste groups of Hindus. While it has been generally believed that PFC marriages among Hindus are mere exceptions and are usually not tolerated, our data show that they can no longer be treated as exceptions.

Independent molecular pathways in initiation and loss of hormone responsiveness of breast carcinomas.

These studies were set up to determine whether those oncogenes participating in the initiation of mammary carcinogenesis (for example, ras oncogenes) play a direct role in the outcome of events associated with the late stages of tumor development such as loss of hormone dependency. Mammary carcinomas induced by a single carcinogenic insult in pubescent rats was selected as an in vivo model system with direct relevance to human breast cancer. Acquisition of hormone-independent growth in these carcinogen-induced tumors was found to be independent of the activation of ras oncogenes during the early stages of carcinogenesis.

Specific activation of the cellular Harvey-ras oncogene in dimethylbenzanthracene-induced mouse mammary tumors.

Genomic DNAs from dimethylbenzanthracene-induced BALB/c mouse mammary tumors arising from the transplantable hyperplastic outgrowth (HPO) line designated DI/UCD transformed NIH 3T3 cells upon transfection. Transforming activity was attributed to the presence of activated Harvey ras-1 oncogenes containing an A----T transversion at the middle adenosine nucleotide in codon 61. DNAs from untreated DI/UCD HPO cells and radiation-induced and spontaneous mammary tumors from the DI/UCD HPO line failed to transform NIH 3T3 cells.

Activated K-ras and N-ras oncogenes in primary renal mesenchymal tumors induced in F344 rats by methyl(methoxymethyl)nitrosamine.

Administration of methyl(methoxymethyl)nitrosamine to newborn Fischer 344 rats results in the preferential induction of renal tumors arising from the mesenchymal component of the kidney. DNA from a significant proportion of these tumors was capable of transforming NIH/3T3 cells. This report describes the renal tumor model, the detection of two different ras transforming genes in the kidney tumors (the N-ras oncogene in 1 and K-ras oncogene in 10 kidney tumors) and the characterization of DNA sequences specifying the transformed phenotype.

Direct mutagenesis of Ha-ras-1 oncogenes by N-nitroso-N-methylurea during initiation of mammary carcinogenesis in rats.

Induction of mammary carcinomas in rats by a single exposure to a carcinogen during sexual development often involves malignant activation of the Ha-ras-1 locus. Each of the Ha-ras-1 oncogenes present in tumours induced by N-nitroso-N-methylurea, but not in those induced by 7,12-dimethylbenz(a)anthracene, became activated by the same G----A transition, the type of mutation induced by N-nitroso-N-methylurea. These results are consistent with the notion that Ha-ras-1 oncogenes are directly activated by the carcinogen during initiation of neoplasia.