Biomedical subjects

M A Nelson

Publications and source records attributed to M A Nelson.

At least 37 records · Page 2Linked to original sources

PubMed1999

Relationship of p53 mutations to epidermal cell proliferation and apoptosis in human UV-induced skin carcinogenesis.

Human skin is continually subjected to UV-irradiation with the p53 gene playing a pivotal role in repair of UV-induced DNA damage and apoptosis. Consequently, p53 alterations are early events in human UV-induced skin carcinogenesis. We studied 13 squamous cell carcinomas (SCC), 16 actinic keratoses (AK), 13 samples adjacent to an AK (chronically sun-damaged), and 14 normal-appearing skin samples for p53 mutation, p53 immunostaining (IHC), apoptosis (in situ TUNEL and morphology), and proliferation (PCNA). The frequency of p53 mutation increased from 14% in normal skin, to 38.5% in sun-damaged skin, 63% in AK, and 54% in SCC. p53 IHC increased similarly. Apoptosis (TUNEL) increased from 0.06 +/- 0.02%, to 0.1 +/- 0.2, 0.3 +/- 0.3, and 0.4 +/- 0.3 in normal skin, sun-damaged skin, AK, and SCC, respectively. Apoptosis was strongly correlated with proliferation (i.e., TUNEL and PCNA, r = 0.7, P < 0.0001), and proliferation was significantly increased in the progression from normal skin to SCC. Bax was significantly increased in SCC compared to AK. These data imply that apoptosis in samples with a high frequency of p53 mutation may not necessarily be p53-dependent. We suggest that there is a mechanism for apoptosis in response to increased cellular proliferation that is p53-independent.

Aged↗

PubMed1999

Selenium and prostate cancer prevention.

Prostate cancer is the second leading cause of cancer deaths in men, therefore it is increasingly important to understand its biology and epidemiology. New approaches for the primary and secondary prevention of prostate cancer are needed, including innovative uses of chemoprevention. This review provides an overview of the epidemiological data suggesting that higher intakes of selenium may reduce the risk of prostate cancer. In addition, a discussion of preclinical data is presented. Special emphasis is placed on the following areas: (1) chemical forms of selenium and antitumorigenic activity, (2) in vitro effects of selenite versus monomethylated selenium, and (3) current clinical intervention trials with selenium in prostate cancer. Chemoprevention, especially with dietary forms of selenium, is a promising new approach that presently is undergoing intensive investigation.

Cell Division↗

PubMed1998

Inhibitory effect of selenomethionine on the growth of three selected human tumor cell lines.

Selenium supplementation has been shown for many years to work as an anticarcinogenic agent both in epidemiology and in in vitro studies. Selenium supplementation has recently been shown to decrease total cancer incidence. However, the mechanism of action of selenium as an anticarcinogenic agent has yet to be elucidated. Selenomethionine was the predominant form of selenium in the dietary supplement in the study by Clark et al. (Clark, L.C., Combs, G.F., Turnbull, W.B., Slate, E.H., Chalker, D.K., Chow, J., Davis, L.S., Glover, R.A., Graham, G.F., Gross, E.G., Krongrad, A., Lesher, J.L., Park, H.K., Sanders, B.B., Smith, C.L., Taylor, J.R. and The Nutritional Prevention of Cancer Study Group (1996) Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin: a randomized controlled trial. J. Am. Med. Assoc., 276 (24), 1957-1963) and therefore we evaluated the growth inhibitory effects of selenomethionine against human tumor cells. Selenomethionine was tested against each of three human tumor cell lines (MCF-7/S breast carcinoma, DU-145 prostate cancer cells and UACC-375 melanoma) and against normal human diploid fibroblasts. All cell lines demonstrated a dose-dependent manner of growth inhibition by selenomethionine. Selenomethionine inhibited the growth of all of the human tumor cell lines in the micromolar (microM) range (ranging from 45 to 130 microM) while growth inhibition of normal diploid fibroblasts required 1 mM selenomethionine, approximately 1000-fold higher than for the cancer cell lines. In short, normal diploid fibroblasts were less sensitive than the cancer cell lines to the growth inhibitory effects of selenomethionine. Furthermore, we show that selenomethionine administration to these cancer cell lines results in apoptotic cell death and aberrant mitoses. These results demonstrate the differential sensitivity of tumor cells and normal cells to selenomethionine.

Antineoplastic Agents↗

PubMed1998

Identification of the first fungal annexin: analysis of annexin gene duplications and implications for eukaryotic evolution.

Annexin homologues have been found in animals, plants, and distinct protist lineages. We report the identification of the first fungal annexin, encoded by the anx14 gene of the filamentous ascomycete Neurospora crassa. Annexins have a complex evolutionary history and exhibit a large number of gene duplications and gene losses in various taxa, including the complete loss of annexin sequences from another ascomycete, the budding yeast Saccharomyces cerevisiae. Surprisingly, the N. crassa annexin homologue is most closely related to the annexin homologue of the slime mold Dictyostelium discoideum, suggesting a phylogenetic link between cellular slime molds and true fungi. Both of these annexin homologues are closely related to the family of annexin homologues present in animals, an observation consistent with the existence of the animal-fungal clade. These data further suggest that the gene duplications that generated the family of annexin sequences present in animals, fungi, and slime molds began prior to the divergence of these taxa.

Amino Acid Sequence↗

PubMed1997

Band 1p36 abnormalities and t(1;17) in ovarian carcinoma.

In a series of 128 karyotyped ovarian carcinomas, 42% of cases with chromosome 1 clonal structural abnormalities had breaks at band 1p36 (usually involving translocations of unknown material). Fluorescent in situ hybridization (FISH) studies using combinations of 1 centromere and 1p36.3-specific probes (16 cases) or 1 centromeric and 17 whole-chromosome paint probes (11 cases with 1p+) revealed a trend toward deletion of 1pter relative to 1 centromere (63%); intratumor heterogeneity; and the origin of 1p+ in 3/11 cases (27%) from chromosome 17 [t(1;17)(p36;?)]. The frequency of this specific breakpoint and its involvement in recurrent translocations suggest that these regions are loci for genes important in the pathogenesis of a subset of sporadic ovarian carcinomas.

Adenocarcinoma↗

PubMed1997

Expressed sequences from conidial, mycelial, and sexual stages of Neurospora crassa.

In the Neurospora Genome Project at the University of New Mexico, expressed sequence tags (ESTs) corresponding to three stages of the life cycle of the filamentous fungus Neurospora crassa are being analyzed. The results of a pilot project to identify expressed genes and determine their patterns of expression are presented. 1,865 partial complementary DNA (cDNA) sequences for 1,409 clones were determined using single-pass sequencing. Contig analysis allowed the identification of 838 unique ESTs and 156 ESTs present in multiple cDNA clones. For about 34% of the sequences, highly or moderately significant matches to sequences (of known and unknown function) in the NCBI database were detected. Approximately 56% of the ESTs showed no similarity to previously identified genes. Among genes with assigned function, about 43.3% were involved in metabolism, 32.9% in protein synthesis and 8.4% in RNA synthesis. Fewer were involved in defense (6%), cell signalling (3.4%), cell structure (3.4%) and cell division (2.6%).

Amino Acid Sequence↗

PubMed1997

Involvement of polyamines in selenomethionine induced apoptosis and mitotic alterations in human tumor cells.

The efficacy of dietary selenium supplementation is currently being evaluated in intervention trials. However, the biological mechanisms underlying the cancer chemopreventive effects of selenium supplementation have yet to be elucidated. Selenium metabolism and polyamine biosynthesis are linked in their common requirement for S-adenosylmethionine. Selenomethionine was the predominant form of selenium in the dietary supplement, therefore we evaluated the anti-tumorigenic effects of selenomethionine. We found that selenomethionine inhibited tumor growth (both in A549 lung and HT29 colon cancer cells) in a dose-dependent manner. At 24 and 72 h, polyamine content of A549 and HT29 cancer cell lines was decreased at doses that inhibited 50% of normal growth. Selenomethionine treatment induced apoptosis in both cancer cell lines. Exogenous spermine administration, which replenishes intracellular polyamine levels, prevented selenomethionine induced apoptosis. Selenomethionine administration to the cancer cell lines increased the number of cells in metaphase. This cell cycle effect appeared to be reversed with the co-administration of selenomethionine and spermine. These data suggested that at least part of the anti-carcinogenic effects of selenium supplementation might be due to a depletion in polyamine levels. This depletion of polyamines leads to an induction in apoptosis and perturbations in the cell cycle.

Antineoplastic Agents↗

PubMed1997

A putative rhamnogalacturonase required for sexual development of Neurospora crassa.

In previous work, the asd-I (ascus development) gene of the filamentous fingus Neurospora crassa was identified as a gene expressed preferentially during the sexual cycle and shown to be essential for normal sexual development. The asd-I gene has been sequenced and further characterized. It contains two introns, the first of which is in-frame and inefficiently or differentially spliced. The predicted ASD-I protein has extensive homology with rhamnogalacturonase B of Aspergillus aculeatus, which cleaves the backbone within the ramified hairy regions of pectin. In homozygous asd-I crosses, sexual development is initiated and large numbers of normal-sized asci are formed. Ascospore delineation does not occur, however, and no sexual progeny are produced. As most asd-I asci contain eight nuclei, the two meiotic divisions and subsequent mitotic division typical of normal crosses seem to occur, but the haploid nuclei are not partitioned into ascospores. In wild-type crosses, the ASD-I protein is present in large amounts in croziers and young asci, but it is only faintly detectable in more mature asci containing developing ascospores. Models to explain the possible role of a rhamnogalacturonase in sexual development are presented.

Amino Acid Sequence↗

PubMed1997

Increased chromosome 20 copy number detected by fluorescence in situ hybridization (FISH) in malignant melanoma.

DNA amplification is an important mechanism of tumor progression that allows cancer cells to up-regulate the expression of critical genes such as oncogenes and genes conferring drug resistance. Recent studies using comparative genomic hybridization (CGH) revealed increased DNA copies of 20q sequences in 7 melanoma cell lines and B archival metastatic melanoma lesions. To evaluate chromosome 20 abnormalities in more detail and to resolve discrepancies between karyotype and CGH findings, we performed FISH analysis of metaphase cells in 13 melanoma cell lines (including the 7 lines used for CGH) and 9 primary melanoma specimens by using a whole chromosome paint specific for chromosome 20. All 13 cell lines (100%) and 8/9 primary tumors (89%) showed extra copies of chromosome 20 relative to tumor ploidy. Additionally, 6/14 cell lines (43%) and 2/8 primary tumors (25%) showed translocated chromosome 20 material previously undetected by standard cytogenetics. Cytologic evidence for gene amplification was also found in one cell line, which contained an add(20)(p13), with additional DNA being derived from 20q sequences. These data suggest that overrepresentation of a gene or genes important for melanoma pathogenesis resides on the long arm of chromosome 20.

Chromosome Aberrations↗

PubMed1996

Detection of K-ras gene mutations in non-neoplastic lung tissue and lung cancers.

Oncogene and tumor suppressor gene mutations are candidate biomarkers for cancer risk assessment and lesion detection. The K-ras oncogene has previously been associated with non-small cell lung cancer (NSCLC), particularly adenocarcinomas in which reported rates of mutation have approached 30-40%. We have analyzed non-malignant lung tissue from patients with lung cancer and primary lung cancers for K-ras gene mutations. Mutations were detected in 32% cancers and 29% non-malignant lung tissue from patients with cancer. The majority of tumors testing positive were adenocarcinoma of the lung. Normal DNA controls, including peripheral blood lymphocytes and normal lung from non-smokers, were negative. The ability to detect genetic alterations in non-malignant lung tissues is consistent with the concept that genetic alterations are involved in field cancerization of the aerodigestive tract.

Adenocarcinoma↗

PubMed1996

Amplification of 19q13.1-q13.2 sequences in ovarian cancer. G-band, FISH, and molecular studies.

In this study of ovarian carcinoma, we extended previous findings by performing FISH using chromosome 19 paint and microFISH probes and patient samples with and without abnormalities of chromosome 19 identified by G-banding. Karyotype interpretations of der(19) were confirmed, while additional 19 translocations were also detected by FISH with 19WCP in some cases. Similar FISH studies of ovarian carcinoma cell lines found chromosome 19 abnormalities even after extensive in vitro culture. MicroFISH probes were generated by chromosome microdissection from two cases with hsr(19) and mapped to 19q13.2 and 19q13.1-.2, respectively. FISH with these microFISH probes alone or in combination with a 19WCP probe to four patient samples and seven cell lines showed that 65% of chromosome 19 structural abnormalities contained 19q13.1-q13.2 sequences, sometimes as large hsrs. Ovarian cancer cell lines showed amplification and overexpression of the AKT2 putative oncogene, but not the ERCC-2 DNA repair gene in this chromosomal region. In addition to AKT2, amplification and overexpression of other yet-unidentified genes in the 19q13.1-q13.2 region may contribute to ovarian carcinoma pathogenesis or progression.

Chromosome Aberrations↗

PubMed1996

Mating systems in ascomycetes: a romp in the sac.

The ascomycetous fungi choose between sexual and asexual reproduction; it is only when appropriately stressed that most resort to sexual development. Many of the proteins known to regulate development in animals (homeodomain proteins, HMG-box proteins) are also central to the control of sexual differentiation in the ascomycetes. Most ascomycete mating-type loci are structurally complex idiomorphs (large regions of nonhomologous DNA), in that they encode multiple products of probable independent evolutionary origin. The products of the mating-type genes are the master regulators of sexual development; we are just beginning our search for factors involved in the signal transduction pathway downstream from these master regulators.

Ascomycota↗

PubMed1996

Clinical implications of cytogenetic abnormalities in melanoma.

Unlike leukemia, in which specific reciprocal translocations are frequently observed, melanomas involve complex recurring chromosome anomalies. Analysis of the constituted genome of melanoma patients should identify cancer susceptibility genes and at-risk individuals in families with a history of melanoma. The first of these genes to be cloned is the cell cycle regulatory protein inhibitor--the p16 gene-- and a second gene locus for melanoma predisposition has been linked to the chromosome 1p36 band region. Detection of the most common somatic genetic alterations in melanoma enhances our understanding of molecular mechanisms of melanoma development and may lead to genetic markers in melanoma. Some alterations may be used to identify interesting subpopulations. Others may be of prognostic value when they are considered in tandem with clinical data.

Apc6 Subunit, Anaphase-Promoting Complex-Cyclosome↗

PubMed1996

Pseudohomothallism and evolution of the mating-type chromosome in Neurospora tetrasperma.

Ascospores of Neurospora tetrasperma normally contain nuclei of both mating-type idiomorphs (a and A), resulting in self-fertile heterokaryons (a type of sexual reproduction termed pseudohomothallism). Occasional homokaryotic self-sterile strains (either a or A) behave as heterothallics and, in principle, provide N. tetrasperma with a means for facultative outcrossing. This study was conceived as an investigation of the population biology of N. tetrasperma to assess levels of intrastrain heterokaryosis (heterozygosity). The unexpected result was that the mating-type chromosome and autosomes exhibited very different patterns of evolution, apparently because of suppressed recombination between mating-type chromosomes. Analysis of sequences on the mating-type chromosomes of wild-collected self-fertile strains revealed high levels of genetic variability between sibling A and a nuclei. In contrast, sequences on autosomes of sibling A and a nuclei exhibited nearly complete homogeneity. Conservation of distinct haplotype combinations on A and a mating-type chromosomes in strains from diverse locations further suggested an absence of recombination over substantial periods of evolutionary time. The suppression of recombination on the N. tetrasperma mating-type chromosome, expected to ensure a high frequency of self fertility, presents an interesting parallel with, and possible model for studying aspects of, the evolution of mammalian sex chromosomes.

Chromosome Mapping↗

PubMed1996

Sharing patient care among disciplines: mandates and pitfalls.

Patient-focused care has been used to help cut health care costs. This model changes the way work is done, with a focus on processes rather than individual functions of distinct professions, and it implies shared responsibility for patient outcomes. It also requires that different disciplines share patient care. The goal of sharing patient care among disciplines can be quite challenging to accomplish and sustain. This article describes the difficulties encountered when multiple disciplines share patient care, explores in some depth the causes of these difficulties, and gives suggestions on how this aspect of redesign can be proactively managed.

Decision Making, Organizational↗

PubMed1995

Leiomyosarcoma of the superior vena cava and azygos vein.

A 40-year-old woman presented with facial swelling and pressure sensation of the ears and sinuses. Chest roentgenography revealed a right paratracheal mass, which was confirmed by a venogram, and transjugular biopsy showed low-grade leiomyosarcoma. The superior vena cava was resected and reconstructed using a spiral vein graft. Pathologic evaluation revealed a low-grade leiomyosarcoma arising from both the superior vena cava and the azygos vein with clear margins.

Adult↗

PubMed1995

Cytogenetics of 158 patients with regional or disseminated melanoma. Subset analysis of near-diploid and simple karyotypes.

We report on the cytogenetic analyses of 158 cases of metastatic malignant melanoma, comprised of 63 cases with regional disease (RD) and 95 cases with distant (metastatic) disease (DD). Clonal structural abnormalities were identified in 126 (80%) cases and were significantly increased ( < 0.01 after adjusting for multiple comparisons) on chromosomes (in order of frequency of involvement) 1, 6, 7, 11, 9, and 3. Clustering of breakpoints occurred at 1p36, 1p22-q21, 6p11-q21, 9p, 11q23-qter, 13p (especially for cases with DD), and 19q13. The most common clonal numerical abnormalities, in a subset of 49 near-diploid cases were -10, -22, -9, +7, -19, and -Y. Analysis of chromosome segment gains and losses (CSRP) showed frequent loss of chromosomes 6 and 10, followed by equal rates of involvement of chromosomes 1, 7, and 9. Whole or segmental losses of chromosome 9 (especially 9p) correlate well with recent molecular genetic studies identifying putative suppressor genes, and are also likely important genetic abnormalities. However, based on the frequency of abnormalities in this large series of metastatic melanomas, it is likely that structural abnormalities of 1 and 6, and 10 are important in the pathogenesis of sporadic advanced melanoma.

Adult↗

PubMed1995

Analysis of K-ras gene mutations in malignant and nonmalignant endobronchial tissue obtained by fiberoptic bronchoscopy.

Using polymerase chain reaction DNA amplification, we identified K-ras oncogene mutations in bronchial biopsies obtained from patients undergoing bronchoscopy for clinical indications. We hypothesized that these mutations would be found in a field encompassing malignant and nonmalignant tissues in patients with pulmonary carcinomas, and also possibly in tissue from some patients who smoked but did not have pulmonary malignancy. We found K-ras mutations in endobronchial biopsies from nine of 22 patients (41%) with carcinoma of the lung. In five of these patients, mutations were found in both malignant and nonmalignant specimens. In two instances, mutations were found only in the neoplastic tissue, and in two cases mutations were present only in the nonmalignant tissue. Furthermore, we identified two patients with K-ras mutations among seven patients in whom no clinical malignancy was apparent. Our data suggest that some oncogene activations may occur over a broad area in smokers with and without malignancy, and they imply that K-ras mutations may serve as surrogate markers for malignant potential.

Aged↗