PubMed Health⌕ Search

Biomedical subjects

D N Louis

Publications and source records attributed to D N Louis.

At least 55 records · Page 3Linked to original sources
PubMed1999

The human glia maturation factor-gamma gene: genomic structure and mutation analysis in gliomas with chromosome 19q loss.

Human glia maturation factor-gamma (hGMF-gamma) is a recently identified gene that may be involved in glial differentiation, neural regeneration, and inhibition of tumor cell proliferation. The gene maps to the long arm of chromosome 19 at band q13.2, a region that is frequently deleted in human malignant gliomas and is thus suspected to harbor a glioma tumor suppressor gene. Given the putative role of hGMF-gamma in cell differentiation and proliferation and its localization to chromosome 19q13, this gene is an interesting candidate for the chromosome 19q glioma tumor suppressor gene. To evaluate this possibility, we determined the genomic structure of human hGMF-gamma and performed mutation screening in a series of 41 gliomas with and without allelic loss of chromosome 19q. Mutations were not detected, which suggests that hGMF-gamma is not the chromosome 19q glioma suppressor gene. However, the elucidation of the genomic structure of hGMF-gamma may prove useful in future investigations of hGMF-gamma in the normal adult and developing human nervous system.

Adult↗
PubMed1999

Malignant transformation of neurofibromas in neurofibromatosis 1 is associated with CDKN2A/p16 inactivation.

Patients with neurofibromatosis 1 (NF1) are predisposed to develop multiple neurofibromas (NFs) and are at risk for transformation of NFs to malignant peripheral nerve sheath tumors (MPNSTs). Little is known, however, about the biological events involved in the malignant transformation of NFs. We examined the CDKN2A/p16 gene and p16 protein in NFs and MPNSTs from patients with NF1. On immunohistochemical analysis, all NFs expressed p16 protein. The MPNSTs, however, were essentially immunonegative for p16, with striking transitions in cases that contained both benign and malignant elements. None of the benign tumors had CDKN2A/p16 deletions, whereas three of six MPNSTs appeared to have homozygous CDKN2A/p16 deletions. Methylation analysis and mutation analysis of CDKN2A/p16 in MPNSTs did not reveal any abnormalities. These results show that malignant transformation of NF is associated with loss of p16 expression, which is often secondary to homozygous deletion of the CDKN2A/p16 gene. The findings suggest that CDKN2A/p16 inactivation occurs during the malignant transformation of NFs in NF1 patients and raises the possibility that p16 immunohistochemistry may provide ancillary information in the distinction of NF from MPNST.

Adolescent↗
PubMed1999

Mapping of a target region of allelic loss to a 0.5-cM interval on chromosome 22q13 in human colorectal cancer.

BACKGROUND & AIMS: Chromosomal allelic losses have a varying frequency in colorectal cancer. The aim of this study was to define the target region of allelic loss on chromosome 22q in human colorectal carcinogenesis. METHODS: Fifty-seven pairs of matched normal colonic mucosa and tumor specimens from patients with colorectal cancer, as well as 15 colon cancer-derived cell lines, were genotyped using 15 microsatellite markers spanning chromosome 22q. A potential candidate gene was analyzed by a single-strand conformation polymorphism (SSCP)/direct DNA sequencing approach. RESULTS: After excluding 7 tumors with evidence of microsatellite instability, allelic loss was observed in 11 of the informative tumors (22%), 5 of which exhibited losses in all informative loci. The remaining 6 tumors showed variable patterns of partial allelic loss on chromosome 22q, thereby localizing a minimal region of allelic deletion between markers D22S1171 and D22S928. Physical mapping showed that this interval was 0.57 cM consisting of approximately 425 kilobases. Database searches identified the NBK/BIK gene, a proapoptotic BCL-2 family member, as a candidate gene in that region. However, SSCP/sequencing analysis excluded mutations of this gene. CONCLUSIONS: This study provides evidence for the involvement of putative tumor-suppressor gene(s) on chromosome 22q in human colorectal carcinogenesis. The identification of a 0.5-cM interval serves as the basis for the isolation of such a gene by positional cloning.

Alleles↗
PubMed1999

Oncolytic virus therapy of multiple tumors in the brain requires suppression of innate and elicited antiviral responses.

The occurrence of multiple tumors in an organ heralds a rapidly fatal course. Although intravascular administration may deliver oncolytic viruses/vectors to each of these tumors, its efficiency is impeded by an antiviral activity present in complement-depleted plasma of rodents and humans. Here, this activity was shown to interact with complement in a calcium-dependent fashion, and antibody neutralization studies indicated preimmune IgM has a contributing role. Short-term exposure to cyclophosphamide (CPA) partially suppressed this activity in rodents and humans. At longer time points, cyclophosphamide also abrogated neutralizing antibody responses. Cyclophosphamide treatment of rats with large single or multiple intracerebral tumors substantially increased viral survival and propagation, leading to neoplastic regression.

Animals↗
PubMed1999

Aberrations of the p53 pathway components p53, MDM2 and CDKN2A appear independent in diffuse large B cell lymphoma.

The two gene products of the CDKN2A gene, p16 and p19ARF, have recently been linked to each of two major tumour suppressor pathways in human carcinogenesis, the RB1 pathway and the p53 pathway. p16 inhibits the phosphorylation of the retinoblastoma gene product by cyclin D-dependent kinases, whereas p19ARF targets MDM2, a p53 inhibitory protein, for degradation. A deletion of CDKN2A would therefore disturb both pathways. To explore the p53 pathway genes as a functional unit in diffuse large B cell non-Hodgkin's lymphomas (DLCL), we wanted to see whether there exists mutually exclusiveness of aberrations of CDKN2A, MDM2 and p53, since this has not been analysed previously. We investigated 37 DLCL for aberrations of p15, p16, p19ARF, MDM2, and p53 at the epigenetic, genetic and/or protein levels. Homozygous deletion of CDKN2A was detected in seven (19%) of 37 tumours, and another three cases were hypermethylated at the 5' CpG island of p16. No point mutations were found in CDKN2B or CDKN2A. Immunohistochemical staining of formalin-fixed, paraffin-embedded tissue for p16 confirmed these results, as all tumours with alterations of CDKN2A were p16 immunonegative. We found p53 mutations in eight (22%) cases and MDM2 overexpression in 16 (43%) tumours. Twenty-three (62%) tumours had alterations of one or more p53 pathway components (p53, p19ARF and MDM2). Furthermore, 7/9 (78%) p16-immunonegative tumours showed co-aberration of p53 and/or MDM2. The lack of correlation between these aberrations suggests that DLCL acquire additional growth advantage by inactivating both of these critical regulatory pathways.

Cyclin-Dependent Kinase Inhibitor p16↗
PubMed1999

Mutations in the gene encoding KRIT1, a Krev-1/rap1a binding protein, cause cerebral cavernous malformations (CCM1).

Cerebral cavernous malformations (CCM) are congenital vascular anomalies of the brain that can cause significant neurological disabilities, including intractable seizures and hemorrhagic stroke. One locus for autosomal dominant CCM ( CCM1 ) maps to chromosome 7q21-q22. Recombination events in linked family members define a critical region of approximately 2 Mb and a shared disease haplotype associated with a presumed founder effect in families of Mexican-American descent points to a potentially smaller region of interest. Using a genomic sequence-based positional cloning strategy, we have identified KRIT1, encoding a protein that interacts with the Krev-1/rap1a tumor suppressor, as the CCM1 gene. Seven different KRIT1 mutations have been identified in 23 distinct CCM1 families. The identical mutation is present in 16 of 21 Mexican-American families analyzed, substantiating a founder effect in this population. Other Mexican-American and non-Hispanic Caucasian CCM1 kindreds harbor other KRIT1 mutations. Identification of a common Mexican-American mutation has potential clinical significance for presymptomatic diagnosis of CCM in this population. In addition, these data point to a key role for the Krev-1/rap1a signaling pathway in angiogenesis and cerebrovascular disease.

Blood Vessels↗
PubMed1999

Common regions of deletion on chromosome 22q12.3-q13.1 and 22q13.2 in human astrocytomas appear related to malignancy grade.

Approximately 30% of human astrocytomas have been reported to display allelic loss of the long arm of chromosome 22, suggesting the presence of a chromosome 22q astrocytoma suppressor gene. To define the most likely location for this putative tumor suppressor, we performed deletion mapping on 141 tumors using 16 chromosome 22q microsatellite markers. Allelic loss of 22q was observed in 2/12 (17%) of astrocytomas, 9/29 (31%) of anaplastic astrocytomas, and 38/100 (38%) of glioblastomas, consistent with a role for chromosome 22q loss in astrocytoma progression as well as formation. Twenty-two tumors exhibited allelic loss at every informative locus, consistent with loss of the entire arm of 22q. Twenty-seven tumors showed partial deletions, with one common region of deletion at 22q12.3-q13.1 between markers D22S280 and D22S282, and a second candidate region at 22q13.2 near the marker D22S1170. For the proximal candidate region, the incidence of allelic loss was similar between grades; for the distal locus, the incidence increased with grade, raising the possibility that the distal locus is involved in a later stage of astrocytoma tumorigenesis.

Alleles↗
PubMed1999

Homozygous deletions of the CDKN2C/p18INK4C gene on the short arm of chromosome 1 in anaplastic oligodendrogliomas.

Allelic deletions of the short arm of chromosome 1 are common in oligodendrogliomas and have been correlated with chemosensitivity and better prognosis in patients with high-grade oligodendrogliomas. In these tumors, 1p loss is also inversely related to deletions of the CDKN2A gene on 9p, which encodes the key cell cycle regulatory molecule p16INK4A. Because the CDKN2C gene, which encodes the homologous p18INK4C cell cycle regulatory protein, maps to chromosomal band 1p32, CDKN2C is an attractive candidate for the oligodendroglioma suppressor gene on chromosome 1. To evaluate this possibility, we studied 39 high-grade oligodendrogliomas for homozygous deletions and point mutations of the CDKN2C gene, as well as for allelic loss of 1p. Although no mutations were detected in the CDKN2C coding region, two tumors had homozygous deletions that involved CDKN2C. Interestingly, these cases did not have CDKN2A gene deletions. Coupled with the recent report of rare point mutations of CDKN2C in oligodendrogliomas, these findings suggest that CDKN2C inactivation may be oncogenic in a small percentage of human oligodendrogliomas.

Anaplasia↗
PubMed1999

The hPMS2 exon 5 mutation and malignant glioma. Case report.

Patients with Turcot syndrome (TS) are predisposed to colon tumors and primary brain tumors, typically glioblastomas or medulloblastomas. The authors describe a patient with TS featuring a known germline mutation of exon 5 of the hPMS2 mismatch repair gene who developed two metachronous glioblastomas, both with distinct oligodendroglial features. Molecular genetic analysis revealed allelic loss of chromosome 19q in the patient's second tumor but no allelic loss of chromosome 1p. Prominent microsatellite instability was also found in this tumor, consistent with a germline mismatch repair defect. Because this patient had an unusual underlying condition and his tumor had a unique histological appearance for TS, it was hypothesized that this genetic defect may predispose to malignant gliomas with oligodendroglial features. The authors therefore evaluated whether sporadic glioblastomas and oligodendrogliomas undergo mutations of this region of the hPMS2 gene. However, single-strand conformation polymorphism analysis of hPMS2 exon 5 failed to reveal mutations in 20 sporadic glioblastomas and 16 sporadic oligodendroglial gliomas. Thus, although it is possible that the germline hPMS2 exon 5 mutation may predispose to glioblastomas with an oligodendroglial component, the same genetic defect is not commonly involved in sporadic oligodendrogliomas or glioblastomas.

Adenomatous Polyposis Coli↗
PubMed1999

Immunohistochemical survey of p16INK4A expression in normal human adult and infant tissues.

p16INK4A is a cell cycle inhibitor that is commonly inactivated in human tumors and tumor cell lines. Despite its importance in human neoplasia, the normal pattern of p16 expression remains largely unknown. Therefore, we analyzed the immunohistochemical localization of p16 in all human organs and demonstrated that cellular p16 expression is highly selective. In adults, proliferative endometrium, breast ductal epithelium, squamous and tubal metaplastic epithelium of the uterine cervix, esophageal squamous epithelium, salivary glands, and antral gastric glands all strongly express the protein. p16 is also widely expressed in endocrine glands, including Langerhans cells in the pancreas and anterior pituicytes and Leydig and Sertoli cells in testis. Within each tissue, however, p16 expression does not correlate with cellular proliferation or maturation. In infants, p16 staining was limited to thymic Hassall's corpuscles, occasional thymic lymphocytes, and only rare pancreatic epithelial cells. Therefore, increased expression of p16 in adult tissues, as in mouse tissues, may reflect a role of p16 in cellular senescence. Restriction of p16 expression in infants to the thymus, the only organ committed to early senescence, is also consistent with such a role. Documentation of the pattern of p16 expression in normal tissues will contribute to our understanding of the normal function of this protein and to interpretation of potentially altered p16 expression in human tumors.

Adult↗
PubMed1998

Specific genetic predictors of chemotherapeutic response and survival in patients with anaplastic oligodendrogliomas.

BACKGROUND/METHODS: Gliomas are common malignant neoplasms of the central nervous system. Among the major subtypes of gliomas, oligodendrogliomas are distinguished by their remarkable sensitivity to chemotherapy, with approximately two thirds of anaplastic (malignant) oligodendrogliomas responding dramatically to combination treatment with procarbazine, lomustine, and vincristine (termed PCV). Unfortunately, no clinical or pathologic feature of these tumors allows accurate prediction of their response to chemotherapy. Anaplastic oligodendrogliomas also are distinguished by a unique constellation of molecular genetic alterations, including coincident loss of chromosomal arms 1p and 19q in 50%-70% of tumors. We have hypothesized that these or other specific genetic changes might predict the response to chemotherapy and prognosis in patients with anaplastic oligodendrogliomas. Therefore, we have analyzed molecular genetic alterations involving chromosomes 1p, 10q, and 19q and the TP53 (on chromosome 17p) and CDKN2A (on chromosome 9p) genes, in addition to clinicopathologic features in 39 patients with anaplastic oligodendrogliomas for whom chemotherapeutic response and survival could be assessed. RESULTS/CONCLUSIONS: Allelic loss (or loss of heterozygosity) of chromosome 1p is a statistically significant predictor of chemosensitivity, and combined loss involving chromosomes 1p and 19q is statistically significantly associated with both chemosensitivity and longer recurrence-free survival after chemotherapy. Moreover, in both univariate and multivariate analyses, losses involving both chromosomes 1p and 19q were strongly associated with longer overall survival, whereas CDKN2A gene deletions and ring enhancement (i.e., contrast enhancement forming a rim around the tumor) on neuroimaging were associated with a significantly worse prognosis. The inverse relationship between CDKN2A gene deletions and losses of chromosomes 1p and 19q further implies that these differential clinical behaviors reflect two independent genetic subtypes of anaplastic oligodendroglioma. These results suggest that molecular genetic analysis may aid therapeutic decisions and predict outcome in patients with anaplastic oligodendrogliomas.

Adult↗
PubMed1998

Correlation of high-resolution magic angle spinning proton magnetic resonance spectroscopy with histopathology of intact human brain tumor specimens.

High-resolution magic angle spinning proton (HRMAS 1H) magnetic resonance spectroscopy produces well-resolved spectra of metabolites from intact tissue specimens. Here we report the results of a preliminary study of 19 human brain tumors obtained by applying this method. Among these 19 cases were 2 low-grade astrocytomas, 1 anaplastic astrocytoma, 8 glioblastomas, 6 meningiomas, and 2 schwannomas. In addition, autopsy human brain tissues from two subjects without any known neurological diseases were used as normal controls. The HRMAS 1H magnetic resonance spectroscopy measurements were performed at 2 degrees C on a 400-MHz NMR spectrometer with a HRMAS speed of 2.5 kHz. From these HRMAS 1H MR spectra, we measured the concentrations of 11 metabolites, the ratios of 15 metabolites (resonances) to creatine (at 3.03 ppm), and the spin-spin relaxation time for these metabolites (resonances). Our results indicate that these parameters have the potential to characterize tumor types and grades with statistical significance as well as identify tumor biochemical characteristics. In particular, we found that compared with metabolite concentrations and metabolite spin-spin relaxation time, the metabolic ratios presented the highest sensitivity in differentiating normal tissue from tumors, as well as in distinguishing between tumor groups. Of 15 analyzed metabolic ratios, 12 showed statistical significance in differentiating normal tissue from low-grade and anaplastic astrocytomas, 13 showed statistical significance in differentiating normal tissue from glioblastomas, 14 showed statistical significance in differentiating normal tissue from schwannomas, and 9 showed statistical significance in differentiating normal tissue from meningiomas. Moreover, our results strongly indicate that the resonance ratio of inositol (at 4.05 ppm) to creatine may help distinguish tumor type. Our results suggest that the HRMAS method for intact tissue measurement may function as an adjunct to histopathology and contribute to improved accuracy for brain tumor diagnoses.

Amino Acids↗
PubMed1998

PTEN mutations in gliomas and glioneuronal tumors.

Cytogenetic and loss of heterozygosity studies have suggested the presence of at least one tumor suppressor gene on chromosome 10 involved in the formation of high grade gliomas. Recently, the PTEN gene, also termed MMAC1 or TEP1, on chromosomal band 10q23 has been identified. Initial studies revealed mutations of PTEN in limited series of glioma cell lines and glioblastomas. In order to systematically evaluate the involvement of PTEN in gliomas, we have analysed the entire PTEN coding sequence by SSCP and direct sequencing in a series of 331 gliomas and glioneuronal tumors. PTEN mutations were detected in 20/142 glioblastomas, 1/7 giant cell glioblastomas, 1/2 gliosarcomas, 1/30 pilocytic astrocytomas and 2/22 oligodendrogliomas. No PTEN mutations were detected in 52 astrocytomas, 37 oligoastrocytomas, three subependymal giant cell astrocytomas, four pleomorphic xanthoastrocytomas, 15 ependymomas, 16 gangliogliomas and one dysembryoplastic neuroepithelial tumor. In addition, all tumors were examined for the presence of homozygous deletions of the PTEN gene; these were detected in 7 glioblastomas that did not have PTEN mutations. Therefore, PTEN mutations occur in approximately 20% of glioblastomas but are rare in lower grade gliomas. These findings confirm that PTEN is one of the chromosome 10 tumor suppressor genes involved in the development of glioblastomas.

Female↗
PubMed1998

Co-expression of Fas and Fas ligand in malignant glial tumors and cell lines.

Fas ligand (FasL) is involved in tumor evasion from the immune system. We analyzed 22 human gliomas for expression of FasL and its receptor, Fas. Positive FasL and Fas immunoreactivity was detected in 13 out of 22 tumors by Western blotting and in 15 out of 22 tumors by immunohistochemistry. Immunohistochemistry also showed that Fas and FasL expression was confined to tumor cells. Co-expression of these molecules was confirmed by Western blotting and immunohistochemistry in 4 of 7 glioma cell lines. Co-expression of FasL and Fas within tumor cells suggests that their contribution in vivo to the process of immune system evasion and tumor cell apoptosis is complex and probably involves additional factors.

Astrocytoma↗
PubMed1998

CDKN2A gene deletions and loss of p16 expression occur in osteosarcomas that lack RB alterations.

Osteosarcomas often suffer mutations of the RB (retinoblastoma) gene, with resultant inactivation of the pRb protein. pRb is one component in a cell-cycle control pathway that includes the p16 (encoded by the CDKN2A gene) and cyclin-dependent kinase 4 (cdk4, encoded by the CDK4 gene) proteins. We therefore sought to determine whether the CDKN2A and CDK4 genes were altered in those osteosarcomas that lacked RB inactivation. Twenty-one osteosarcomas (2 low-grade and 19 high-grade) were evaluated for homozygous deletion of the CDKN2A gene, CDK4 amplification, and allelic loss of the RB gene, as well as for expression of p16 and pRb proteins. Five high-grade osteosarcomas showed loss of p16 expression; four of these had homozygous CDKN2A deletions, and the fifth had a probable deletion obscured by numerous nonneoplastic, p16-immunopositive multinucleated giant cells. Thus, p16 immunohistochemistry may provide a sensitive means for assessing CDKN2A status. Twelve tumors (including the two low-grade osteosarcomas) were immunopositive for pRb, and nine tumors were immunonegative for pRb. Of the five cases with CDKN2A/p16 alterations, none had allelic loss of the RB gene and all expressed pRb, suggesting that each of these tumors had an intact RB gene. None of the tumors showed CDK4 amplification. No alterations were detected in the two low-grade osteosarcomas. This study suggests that CDKN2A is a tumor suppressor inactivated in osteosarcomas that lack RB mutations and that the p16-pRb cell-cycle control pathway is deregulated in a large number of high-grade osteosarcomas.

Adolescent↗
PubMed1998

The von Hippel-Lindau tumor suppressor protein is required for proper assembly of an extracellular fibronectin matrix.

Fibronectin coimmunoprecipitated with wild-type von Hippel-Lindau protein (pVHL) but not tumor-derived pVHL mutants. Immunofluorescence and biochemical fractionation experiments showed that fibronectin colocalized with a fraction of pVHL associated with the endoplasmic reticulum, and cold competition experiments suggested that complexes between fibronectin and pVHL exist in intact cells. Assembly of an extracellular fibronectin matrix by VHL-/- renal carcinoma cells, as determined by immunofluorescence and ELISA assays, was grossly defective compared with VHL+/+ renal carcinoma cells. Reintroduction of wildtype, but not mutant, pVHL into VHL-/- renal carcinoma cells partially corrected this defect. Finally, extracellular fibronectin matrix assembly by VHL-/- mouse embryos and mouse embryo fibroblasts (MEFs), unlike their VHL+/+ counterparts, was grossly impaired. These data support a direct role of pVHL in fibronectin matrix assembly.

Animals↗