Showing papers by "Myriad Genetics published in 1997"

Identification of a candidate tumour suppressor gene, MMAC1 , at chromosome 10q23.3 that is mutated in multiple advanced cancers

Abstract: Deletions involving regions of chromosome 10 occur in the vast majority (> 90%) of human glioblastoma multiformes. A region at chromosome 10q23-24 was implicated to contain a tumour suppressor gene and the identification of homozygous deletions in four glioma cell lines further refined the location. We have identified a gene, designated MMAC1, that spans these deletions and encodes a widely expressed 5.5-kb mRNA. The predicted MMAC1 protein contains sequence motifs with significant homology to the catalytic domain of protein phosphatases and to the cytoskeletal proteins, tensin and auxilin. MMAC1 coding-region mutations were observed in a number of glioma, prostate, kidney and breast carcinoma cell lines or tumour specimens. Our results identify a strong candidate tumour suppressor gene at chromosome 10q23.3, whose loss of function appears to be associated with the oncogenesis of multiple human cancers.

MMAC1/PTEN mutations in primary tumor specimens and tumor cell lines.

Abstract: A candidate tumor suppressor gene, MMAC1/PTEN , located in human chromosome band 10q23, was recently identified based on sequence alterations observed in several glioma, breast, prostate, and kidney tumor specimens or cell lines. To further investigate the mutational profile of this gene in human cancers, we examined a large set of human tumor specimens and cancer cell lines of many types for 10q23 allelic losses and MMAC1 sequence alterations. Loss of heterozygosity (LOH) at the MMAC1 locus was observed in approximately one-half of the samples examined, consistent with the high frequency of 10q allelic loss reported for many cancers. Of 124 tumor specimens exhibiting LOH that have been screened for MMAC1 alterations to date, we have detected variants in 13 (∼10%) of these primary tumors; the highest frequency of variants was found in glioblastoma specimens (∼23%). Novel alterations identified in this gene include a missense variant in a melanoma sample and a splicing variant and a nonsense mutation in pediatric glioblastomas. Of 76 tumor cell lines prescreened for probable LOH, microsequence alterations of MMAC1 were detected in 12 (∼16%) of the lines, including those derived from astrocytoma, leukemia, and melanoma tumors, as well as bladder, breast, lung, prostate, submaxillary gland, and testis carcinomas. In addition, in this set of tumor cell lines, we detected 11 (∼14%) homozygous deletions that eliminated coding portions of MMAC1 , a class of abnormality not detected by our methods in primary tumors. These data support the occurrence of inactivating MMAC1 alterations in multiple human cancer types. In addition, we report the discovery of a putative pseudogene of MMAC1 localized on chromosome 9.

BRCA1 Sequence Analysis in Women at High Risk for Susceptibility Mutations: Risk Factor Analysis and Implications for Genetic Testing

Abstract: Octext. —A mutation in theBRCA1gene may confer substantial risk for breast and/or ovarian cancer. However, knowledge regarding all possible mutations and the relationship between risk factors and mutations is incomplete. Objectives. —To identifyBRCA1mutations and to determine factors that best predict presence of a deleteriousBRCA1mutation in patients with breast and/or ovarian cancer. Design. —A complete sequence analysis of theBRCA1coding sequence and flanking intronic regions was performed in 798 women in a collaborative effort involving institutions from the United States, Italy, Germany, Finland, and Switzerland. Participanta. —Institutions selected 798 persons representing families (1 person for each family) thought to be at elevated a priori risk ofBRCA1mutation due to potential risk factors, such as multiple cases of breast cancer, early age of breast cancer diagnosis, and cases of ovarian cancer. No participant was from a family in which genetic markers showed linkage to theBRCA1locus. Major Outcome Measures. —Sequence variants detected in this sample are presented along with analyses designed to determine predictive characteristics of those testing positive forBRCA1mutations. Results. —In 102 women (12.8%), clearly deleterious mutations were detected. Fifty new genetic alterations were found including 24 deleterious mutations, 24 variants of unknown significance, and 2 rare polymorphisms. In a subset of 71 Ashkenazi Jewish women, only 2 distinct deleterious mutations were found: 185delAG in 17 cases and 5382insC in 7 cases. A bias in prior reports for mutations in exon 11 was revealed. Characteristics of a patient's specific diagnosis (unilateral or bilateral breast cancer, with or without ovarian cancer), early age at diagnosis, Ashkenazi Jewish ethnicity, and family history of cancer were positively associated with the probability of her carrying a deleteriousBRCA1mutation. Conclusions. —Using logistic regression analysis, we provide a method for evaluating the probability of a woman's carrying a deleteriousBRCA1mutation for a wide range of cases, which can be an important tool for clinicians as they incorporate genetic susceptibility testing into their medical practice.

Human Mitogen-activated Protein Kinase Kinase 4 as a Candidate Tumor Suppressor

Abstract: Mitogen-activated protein kinases function in signal transduction pathways that are involved in controlling key cellular processes in many organisms. A mammalian member of this kinase family, MKK4/JNKK1/SEK1, has been reported to link upstream MEKK1 to downstream stress-activated protein kinase/JNK1 and p38 mitogen-activated protein kinase. This mitogen-activated protein kinase pathway has been implicated in the signal transduction of cytokine- and stress-induced apoptosis in a variety of cell types. Here, we report that two human tumor cell lines, derived from pancreatic carcinoma and lung carcinoma, harbor homozygous deletions that eliminate coding portions of the MKK4 locus at 17p, located approximately 10 cM centromeric of p53. In addition, in a set of 88 human cancer cell lines prescreened for loss of heterozygosity, we detected two nonsense and three missense sequence variants of MKK4 in cancer cell lines derived from human pancreatic, breast, colon, and testis cells. In vitro biochemical assays revealed that, when stimulated by MEKK1, four of the five altered MKK4 proteins lacked the ability to phosphorylate stress-activated protein kinase. Thus, the incidence of coding mutations of MKK4 in the set of cell lines is 6 of 213 (∼3%). These findings suggest that MKK4 may function as a suppressor of tumorigenesis or metastasis in certain types of cells.

Identification of a 14 kb Deletion Involving the Promoter Region of BRCA1 in a Breast Cancer Family

Abstract: BRCA1 is a breast and ovarian cancer susceptibility gene. An inferred germline regulatory mutation was previously reported in the BRCA1-linked kindred K2035, based on the absence of transcripts from the BRCA1 allele associated with the cancer susceptibility haplotype. In this study, the promoter region of BRCA1 was examined in individuals from K2035 for evidence of a mutation which could halt transcription. Evaluation of a polymorphism located within intron 2 of BRCA1 gave results consistent with the presence of a large deletion in K2035 mutation carriers. Southern blot analysis identified unique restriction fragments which occurred as a result of a 14 kb deletion that removed both of BRCA1's transcription start sites (exons 1a and 1b) as well as exon 2. Sequencing indicated that unequal crossover between Alu repeats was the likely cause of the deletion. Similar deletions may be responsible for other reported inferred regulatory mutations, as well as unidentified mutations in families linked to BRCA1.

The Role of MMAC1 Mutations in Early-Onset Breast Cancer: Causative in Association with Cowden Syndrome and Excluded in BRCA1-Negative Cases

Abstract: Summary Cowden syndrome (CS) is an autosomal dominant disorder associated with the development of hamartomas and benign tumors in a variety of tissues, including the skin, thyroid, breast, endometrium, and brain. It has been suggested that women with CS are at increased risk for breast cancer. A locus for CS was recently defined on chromosome 10 in 12 families, resulting in the identification of the CS critical interval, between the markers D10S215 and D10S541. More recently, affected individuals in four families with CS have been shown to have germ-line mutations in a gene known as " PTEN, " or " MMAC1, " which is located in the CS critical interval on chromosome 10. In this study, we report three novel MMAC1 mutations in CS and demonstrate that MMAC1 mutations are associated with CS and breast cancer. Furthermore, we also show that certain families and individuals with CS do not have mutations in the coding sequence of MMAC1. Finally, we did not detect MMAC1 mutations in a subpopulation of individuals with early-onset breast cancer, suggesting that germ-line mutations in this gene do not appear to be common in this group.

Phenotypic expression of disease in families that have mutations in the 5' region of the adenomatous polyposis coli gene

Abstract: Background: Germline mutation in a gene on chromosome 5 (the adenomatous polyposis coli gene) causes familial adenomatous polyposis of the colorectum. Phenotypic manifestations of this condition va...

Method for sequencing both strands of a double stranded DNA in a single sequencing reaction

Abstract: A method is presented which uses a unique opposite strand joining strategy during PCR of an original DNA to generate a product which, when sequenced with a single sequencing primer yields the sequence of both strands of the original DNA. The PCR primers include 1) a modified oligomer corresponding to the 5' end of a first strand of the DNA to be amplified wherein said modified oligomer includes the reverse complementary sequence to a sequence within said first strand of DNA and a specific PCR priming sequence which will specifically hybridize to a portion of the DNA to be amplified and 2) a second oligomer corresponding to the 5' end of the second strand of the DNA to be amplified and which contains the priming sequence for the second strand of the DNA and will specifically hybridize to a portion of the DNA to be amplified. During PCR an intermediate product is formed where one end of one strand loops around to hybridize to its complement on the same strand. This results in a hairpin structure which elongates using its own strand as a template to form a double sized product that contains the sequence of both original strands. Upon denaturation this yields single strands with the single strands having the sequence of both of the original strands included in tandem. Sequencing these single strands using a single primer, e.g., a primer complementary to the second oligomer, yields the sequences of both strands of the DNA of interest.

Methods for detecting predisposition to cancer at the MTS gene

Abstract: The present invention relates to somatic mutations in the Multiple Tumor Suppressor (MTS) gene in human cancers and their use in the diagnosis and prognosis of human cancer. The invention further relates to germ line mutations in the MTS gene and their use in the diagnosis of predisposition to melanoma, leukemia, astrocytoma, glioblastoma, lymphoma, glioma, Hodgkin's lymphoma, CLL, and cancers of the pancreas, breast, thyroid, ovary, uterus, testis, kidney, stomach and rectum. The invention also relates to the therapy of human cancers which have a mutation in the MTS gene, including gene therapy, protein replacement therapy and protein mimetics. Finally, the invention relates to the screening of drugs for cancer therapy.

Rare mutations and no hypermethylation at the CDKN2A locus in epithelial ovarian tumours

Abstract: The tumour-suppressor gene CDKN2A (p16, MTS1, CDK4I) encodes a cell cycle-regulatory protein and is located on chromosome 9p21, a region deleted in a wide variety of human cancers. To determine the role of the CDKN2A gene in the development of ovarian adenocarcinomas, we examined a large series of benign, low malignant potential (LMP) and invasive ovarian neoplasms for evidence of loss of heterozygosity (LOH), homozygous deletions, point mutations and hypermethylation of the CDKN2A locus. We have previously reported LOH on 9p in 45% of malignant ovarian neoplasms and a smaller percentage of benign and LMP tumours. In the current study, 6 malignant tumours were identified with partial deletions of 9p21. In 5 of these, the CDKN2A gene lays within the minimal deleted region. Homozygous deletions of CDKN2A were observed in only 2/88 invasive ovarian tumours and in 5/11 ovarian cancer cell lines. Of 15 primary ovarian tumours analyzed, one nonsense mutation was identified in a mucinous LMP tumour. No evidence of hypermethylation of the CDKN2A gene was found in 50 primary ovarian adenocarcinomas nor in 3 ovarian cancer cell lines. In conclusion, homozygous deletions, mutations and the de novo methylation of 5' CpG island are not frequent modes of inactivation of the CDKN2A gene in ovarian cancer. The target of 9p LOH in ovarian adenocarcinomas is therefore unknown.

Localization of SMAD5 and its evaluation as a candidate myeloid tumor suppressor.

Abstract: Acquired interstitial or complete losses of chromosome 5 are recurring anomalies associated with preleukemic myelodysplasia and acute myelogenous leukemia with a poor prognosis. Previous studies have delineated a potential myeloid tumor suppressor locus to a <2.4-Mb interval between the genes for IL9 and EGR1 on 5q31. In this report, we have localized the SMAD5 gene, a homologue of the tumor suppressor genes SMAD4/DPC-4 and SMAD2/JV18.1, to the minimal myeloid tumor suppressor locus and characterized its open reading frame and genomic organization. SMAD5 transcripts are readily detectable in hematolymphoid tissues and leukemic blasts. Absence of intragenic mutations in the remaining SMAD5 allele of leukemic patients and multiple solid tumor cell lines prescreened for loss of heterozygosity suggests that SMAD5 may not be a common target of somatic inactivation in malignancy.

Use of beta-sheet mimetics as protease and kinase inhibitors and as inhibitors of transcription factors

Abstract: β-sheet mimetics and methods relating to the same are disclosed. The β-sheet mimetics have utility as protease and kinase inhibitors, as well as inhibitors of transcription factors. Methods of the invention include administration of a β-sheet mimetic, or use of the same for the manufacture of a medicament for treatment of a variety of conditions associated with the targeted protease, kinase and/or transcription factor.

Specific mutations of map kinase 4 (MKK4) in human tumor cell lines identify it as a tumor suppressor in various types of cancer

Abstract: The present invention relates to mutations in the MKK4 gene in human cancers and their use in the diagnosis and prognosis of human cancer. Specific mutations in the MKK4 gene which are associated with breast, pancreatic, colorectal and testicular cancers have been identified. The invention also relates to the therapy of human cancers which have a mutation in the MKK4 gene, including gene therapy, protein replacement therapy and protein mimetics. Finally, the invention relates to the screening of drugs for cancer therapy.

Carboxy-terminal BRCA1 interacting protein

Abstract: Recent evidence indicates that the carboxy-terminal region of the tumor suppressor protein BRCA1 is a functionally significant domain. Using the yeast two-hybrid assay and an in vitro biochemical assay, it is here shown that a protein, B112, interacts specifically with the carboxy-terminal segment of human BRCA1 from residue 1602 to 1863. A germ line truncation mutation, 1853ter, that removes the last 11 amino acids from the carboxy-terminus of BRCA1 abolishes not only the transcription activation function, but also binding to B112. The B112 protein is apparently the same as an uncharacterized protein known as CtIP, the sequence of which was previously deposited in GenBank. Screenings of a panel of 92 tumor cell lines for mutations in the B112/CtIP sequence have identified a number of missense variants, including a non-conserved lysine to glutamic acid change at codon 337 in the pancreatic cancer line, BxPC3. Taken together, these results indicate that B112/CtIP participates in a common biochemical pathway as BRCA1 and that the interaction of these two proteins may be required for the tumor suppressor function of BRCA1.