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D H Gutmann

Publications and source records attributed to D H Gutmann.

At least 37 records · Page 2Linked to original sources
PubMed2001

The NF2 interactor, hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), associates with merlin in the "open" conformation and suppresses cell growth and motility.

The neurofibromatosis 2 tumor suppressor protein, merlin or schwannomin, functions as a negative growth regulator; however, its mechanism of action is not known. In an effort to determine how merlin regulates cell growth, we analyzed a recently identified novel merlin interactor, hepatocyte growth factor-regulated tyrosine kinase substrate (HRS). We demonstrate that regulated overexpression of HRS in rat schwannoma cells results in similar effects as overexpression of merlin, including growth inhibition, decreased motility and abnormalities in cell spreading. Previously, we showed that merlin forms an intramolecular association between the N- and C-termini and exists in "open" and "closed" conformations. Merlin interacts with HRS in the unfolded, or open, conformation. This HRS binding domain maps to merlin residues 453-557. Overexpression of C-terminal merlin has no effect on HRS function, arguing that merlin binding to HRS does not negatively regulate HRS growth suppressor activity. These results suggest the possibility that merlin and HRS may regulate cell growth in schwannoma cells through interacting pathways.

Animals↗
PubMed2001

Neurofibromatosis 1 (NF1) heterozygosity results in a cell-autonomous growth advantage for astrocytes.

Individuals with neurofibromatosis 1 (NF1) develop low-grade astrocytomas at an increased frequency. To gain insight into the function of the Nf1 gene product as a growth regulator for astrocytes, we examined mice heterozygous for a targeted Nf1 mutation. In our previous studies, we demonstrated increased numbers of proliferating astrocytes in Nf1 heterozygote (Nf1+/-) mice in vivo. We now show that cultured Nf1+/- astrocytes exhibit a cell-autonomous growth advantage in vitro associated with increased p21-ras pathway activation. Furthermore, we demonstrate that Nf1+/-;wild-type N-ras mice have a similar astrocyte growth advantage in vitro and in vivo as either oncogenic N-ras or Nf1+/-; oncogenic N-ras mice. Lastly, mice heterozygous for targeted defects in both Nf1 and p53 as well as Nf1 and Rb exhibit 3- and 2.5-fold increases in astrocyte proliferation in vivo, respectively, suggesting that abnormalities in Nf1- and p53/Rb-regulated pathways cooperate in the heterozygous state to confer a growth advantage for brain astrocytes. Collectively, these results provide evidence for a cell-autonomous growth advantage in Nf1+/- astrocytes and suggest that some of the brain pathology in individuals with NF1 might result from reduced, but not absent, NF1 gene function.

Animals↗
PubMed2001

The protein 4.1 tumor suppressor, DAL-1, impairs cell motility, but regulates proliferation in a cell-type-specific fashion.

The neurofibromatosis 2 (NF2) tumor suppressor belongs to the Protein 4.1 family of molecules that link the actin cytoskeleton to cell surface glycoproteins. We have previously demonstrated that the NF2 protein, merlin, can suppress cell growth in vitro and in vivo as well as impair actin cytoskeleton-associated processes, such as cell spreading, attachment, and motility. Recently, we determined that expression of a second Protein 4.1 tumor suppressor, DAL-1, was lost in 60% of sporadic meningiomas, but not schwannomas. In this report, we demonstrate that DAL-1 suppresses cell proliferation in meningioma, but not schwannoma cells. Similar to merlin, DAL-1 interacts with other ERM proteins and betaII-spectrin, but not the merlin interactor protein, SCHIP-1. In addition, we report the identification of the full-length DAL-1 tumor suppressor, termed KIAA0987. Collectively, these results suggest that the two Protein 4.1 meningioma tumor suppressors, merlin and DAL-1, may be functionally distinct proteins with different mechanisms of action.

Actin Cytoskeleton↗
PubMed2001

NF1 deletions in S-100 protein-positive and negative cells of sporadic and neurofibromatosis 1 (NF1)-associated plexiform neurofibromas and malignant peripheral nerve sheath tumors.

Although plexiform neurofibroma (PN) is thought to represent a benign neoplasm with the potential for malignant transformation (malignant peripheral nerve sheath tumor; MPNST), its neoplastic nature has been difficult to prove due to cellular heterogeneity, which hampers standard molecular genetic analysis. Its mixed composition typically includes Schwann cells, fibroblasts, perineurial-like cells, and mast cells. Although NF1 loss of heterozygosity has been reported in subsets of PNs, it remains uncertain which cell type(s) harbor these alterations. Using a dual-color fluorescence in situ hybridization and immunohistochemistry technique, we studied NF1 gene status in S-100 protein-positive and -negative cell subpopulations in archival paraffin-embedded specimens from seven PNs, two atypical PNs, one cellular/atypical PN, and eight MPNSTs derived from 13 patients, seven of which had neurofibromatosis type 1 (NF1). NF1 loss was detected in four of seven PNs and one atypical PN, with deletions entirely restricted to S-100 protein-immunoreactive Schwann cells. In contrast, all eight MPNSTs harbored NF1 deletions, regardless of S-100 protein expression or NF1 clinical status. Our results suggest that the Schwann cell is the primary neoplastic component in PNs and that S-100 protein-negative cells in MPNST represent dedifferentiated Schwann cells, which harbor NF1 deletions in both NF1-associated and sporadic tumors.

Adolescent↗
PubMed2001

The generation and characterization of a cell line derived from a sporadic renal angiomyolipoma: use of telomerase to obtain stable populations of cells from benign neoplasms.

Angiomyolipomas are benign tumors of the kidney derived from putative perivascular epithelioid cells, that may undergo differentiation into cells with features of melanocytes, smooth muscle, and fat. To gain further insight into angiomyolipomas, we have generated the first human angiomyolipoma cell line by sequential introduction of SV40 large T antigen and human telomerase into human angiomyolipoma cells. These cells show phenotypic characteristics of angiomyolipomas, namely differentiation markers of smooth muscle (smooth muscle actin), adipose tissue (peroxisome proliferator-activator receptor gamma, PPARgamma), and melanocytes (microophthalmia, MITF), thus demonstrating that a single cell type can exhibit all of these phenotypes. These cells should serve as a valuable tool to elucidate signal transduction pathways underlying renal angiomyolipomas.

Actins↗
PubMed2001

Merlin: hanging tumor suppression on the Rac.

Cancer can result from any number of abnormalities in the control of cell-cycle progression, intracellular signaling and transduction of extracellular cues. Many insights into the crucial events that govern the regulation of cell growth have derived from studies of the gene products mutated in inherited cancer syndromes. Recent work on the neurofibromatosis 2 (NF2) tumor suppressor gene suggests that this negative growth regulator might function by modulating growth factor and extracellular matrix (ECM) signals that trigger Rac1-dependent cytoskeleton-associated processes. In this article, we propose a molecular model for NF2 protein (merlin) function in the light of these and related new findings.

Cell Division↗
PubMed2001

Tumorigenesis in neurofibromatosis: new insights and potential therapies.

The neurofibromatoses NF1 and NF2 are inherited cancer predisposition syndromes in which affected individuals are prone to development of mostly benign, but occasionally malignant, tumors. The NF1 and NF2 genes function as tumor suppressor genes (negative growth regulators), such that their loss of expression predisposes to tumor formation. Neurofibromin, the protein product of the NF1 gene, acts as a negative regulator of the ras proto-oncogene, to reduce cell growth. Merlin, the NF2 gene product, is involved in regulating cell proliferation and motility, and probably plays a role in integrating multiple cell-signaling pathways. By understanding the function of these tumor suppressors, we have a unique opportunity to develop targeted pharmacotherapeutic interventions for these disorders.

Cell Division↗
PubMed2001

The neurofibromatoses: when less is more.

The study of cancer predisposition syndromes presents unique opportunities to gain insights into the genetic events associated with tumor pathogenesis. Individuals with two inherited cancer syndromes, neurofibromatosis 1 (NF1) and neurofibromatosis 2 (NF2), develop both benign and malignant tumors. The corresponding genes mutated in these two disorders encode tumor suppressor proteins, termed neurofibromin (NF1) and merlin (NF2), which function in novel ways to regulate cell growth and differentiation. Neurofibromin inhibits cell proliferation, at least in part, by modulating mitogenic pathway signaling through inactivation of p21-ras. In contrast, merlin may act as a membrane-associated molecular switch that regulates cell-cell and cell-matrix signals transduced by cell surface receptors. Significant progress in our understanding of the genetics and biology of NF1 and NF2 has elucidated the roles of these genes in tumor initiation and progression.

Animals↗
PubMed2001

Aggressive phenotypic and genotypic features in pediatric and NF2-associated meningiomas: a clinicopathologic study of 53 cases.

Pediatric and NF2-associated meningiomas are uncommon and poorly characterized in comparison to sporadic adult cases. In order to elucidate their molecular features, we analyzed MIB-1, progesterone receptor (PR), NF2, merlin, DAL-1, DAL-1 protein, and chromosomal arms 1p and 14q in 53 meningiomas from 40 pediatric/NF2 patients using immunohistochemistry and dual-color fluorescence in situ hybridization (FISH). Fourteen pediatric (42%) patients, including 5 previously undiagnosed patients, had NF2. The remaining 19 (58%) did not qualify. All 7 of the adult patients had NF2. Meningioma grading revealed 21 benign (40%), 26 atypical (49%), and 6 anaplastic (11%) examples. Other aggressive findings included high mitotic index (32%), high MIB-1 LI (37%), aggressive variant histology (e.g. papillary, clear cell) (25%), brain invasion (17%), recurrence (39%), and patient death (17%). FISH analysis demonstrated deletions of NF2 in 82%, DAL-1 in 82%, 1p in 60%, and 14q in 66%. NF2-associated meningiomas did not differ from sporadic pediatric tumors except for a higher frequency of merlin loss in the former (p = 0.020) and a higher frequency of brain invasion in the latter (p = 0.007). Thus, although pediatric and NF2-associated meningiomas share the common molecular alterations of their adult, sporadic counterparts, a higher fraction are genotypically and phenotypically aggressive. Given the high frequency of undiagnosed NF2 in the pediatric cases, a careful search for other features of this disease is warranted in any child presenting with a meningioma.

Adolescent↗
PubMed2001

Tumor suppressor gene regulation of cell growth: recent insights into neurofibromatosis 1 and 2 gene function.

The development of cancer involves a myriad of genetic changes that impact on multiple processes important for the orderly regulation of cell growth and differentiation. Genes whose protein products are disrupted during neoplastic transformation are termed "tumor suppressor genes" (TSGs). Many of these TSGs are associated with familial cancer predisposition syndromes, in which affected individuals have an increased risk of certain malignancies. Studies on the mechanism of action for known TSGs have revealed three intracellular loci of critical importance: environmental sensing and signal initiation, signal propagation and transduction, and cell cycle control. The neurofibromatosis 1 and neurofibromatosis 2 genes are discussed as illustrative examples of tumor suppressors that function at the levels of signal transduction and environmental sensing, respectively.

Animals↗
PubMed2000

Malignant peripheral nerve sheath tumors in neurofibromatosis 1.

One of the most clinically aggressive cancers associated with neurofibromatosis 1 (NF1) is the malignant peripheral nerve sheath tumor (MPNST). To determine the incidence and relative risk (RR) of MPNSTs in individuals with NF1, 1,475 individuals with NF1 were included from a cohort of patients examined by a single experienced geneticist from 1977 to 1996. The end points were incidence of MPNST, relative risk of MPNST, and relative risk associated with specific NF1 physical findings. Thirty-four individuals were identified with MPNST (2%). The relative risk of MPNST was higher than expected with an RR value of 113 (95% confidence interval [CI] = 78-158). The average 10-year annual incidence of MPNST between the second and fifth decade of life was roughly the same with a range of 0.0013 and 0.0068 MPNST per patient year. Most lesions occurred in the limbs (n = 18; 53%), and those with limb lesions survived longer than those with nonlimb MPNSTs. Pain associated with a mass was the greatest risk factor associated with MPNST development (RR = 31.4; 95% CI = 13.2-75.1). Further biological and epidemiological studies are needed to determine other factors that influence the risk of MPNST development in individuals affected with NF1. Am. J. Med. Genet. 93:388-392, 2000. Published 2000 Wiley-Liss, Inc.

Adolescent↗
PubMed2000

The neurofibromatosis 2 tumor suppressor protein interacts with hepatocyte growth factor-regulated tyrosine kinase substrate.

The neurofibromatosis 2 tumor suppressor protein schwannomin/merlin is commonly mutated in schwannomas and meningiomas. Schwannomin, a member of the 4.1 family of proteins, which are known to link the cytoskeleton to the plasma membrane, has little known function other than its ability to suppress tumor growth. Using yeast two-hybrid interaction cloning, we identified the HGF-regulated tyrosine kinase substrate (HRS) as a schwannomin interactor. We verified the interaction by both immunoprecipitation of endogenous HRS with endogenous schwannomin in vivo as well as by using bacterially purified HRS and schwannomin in vitro. We narrowed the regions of interaction to include schwannomin residues 256-579 and HRS residues from 480 to the end of either of two HRS isoforms. Schwannomin molecules with a L46R, L360P, L535P or Q538P missense mutation demonstrated reduced affinity for HRS binding. As HRS is associated with early endosomes and may mediate receptor translocation to the lysosome, we demonstrated that schwannomin and HRS co-localize at endosomes using the early endosome antigen 1 in STS26T Schwann cells by indirect immunofluorescence. The identification of schwannomin as a HRS interactor implicates schwannomin in HRS-mediated cell signaling.

Adult↗
PubMed2000

Loss of DAL-1, a protein 4.1-related tumor suppressor, is an important early event in the pathogenesis of meningiomas.

Meningiomas are common nervous system tumors, whose molecular pathogenesis is poorly understood. To date, the most frequent genetic alteration detected in these tumors is loss of heterozygosity (LOH) on chromosome 22q. This finding led to the identification of the neurofibromatosis 2 (NF2) tumor suppressor gene on 22q12, which is inactivated in 40% of sporadic meningiomas. The NF2 gene product, merlin (or schwannomin), is a member of the protein 4.1 family of membrane-associated proteins, which also includes ezrin, radixin and moesin. Recently, we identified another protein 4.1 gene, DAL-1 (differentially expressed in adenocarcinoma of the lung) located on chromosome 18p11.3, which is lost in approximately 60% of non-small cell lung carcinomas, and exhibits growth-suppressing properties in lung cancer cell lines. Given the homology between DAL-1 and NF2 and the identification of significant LOH in the region of DAL-1 in lung, breast and brain tumors, we investigated the possibility that loss of expression of DAL-1 was important for meningioma development. In this report, we demonstrate DAL-1 loss in 60% of sporadic meningiomas using LOH, RT-PCR, western blot and immunohistochemistry analyses. Analogous to merlin, we show that DAL-1 loss is an early event in meningioma tumorigenesis, suggesting that these two protein 4.1 family members are critical growth regulators in the pathogenesis of meningiomas. Furthermore, our work supports the emerging notion that membrane-associated alterations are important in the early stages of neoplastic transformation and the study of such alterations may elucidate the mechanism of tumorigenesis shared by other tumor types.

Animals↗
PubMed2000

Clinic-based study of plexiform neurofibromas in neurofibromatosis 1.

Individuals with neurofibromatosis 1 (NF1) develop both benign and malignant tumors at an increased frequency. One of the most common benign tumors in NF1 is the plexiform neurofibroma. These tumors cause significant morbidity and mortality on account of their propensity to grow and affect adjacent normal tissues. To determine the clinical profile of plexiform neurofibromas in NF1, we conducted a retrospective review of 68 NF1 patients with plexiform neurofibroma. In our series, 44% of tumors were detected by 5 years of age and most were located in the trunk and extremities. Only two patients developed malignant peripheral nerve sheath tumors in their preexisting plexiform neurofibromas. Lastly, we demonstrate that there were no specific clinical features of NF1 associated with the presence of plexiform neurofibroma. These results underscore the importance of careful serial examinations in the evaluation of patients with NF1.

Adolescent↗
PubMed2000

Genetic and cellular defects contributing to benign tumor formation in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is a common inherited cancer predisposition syndrome. The NF1 gene product, neurofibromin, is hypothesized to function as a tumor suppressor and nearly all NF1 patients develop benign peripheral nerve tumors. These neurofibromas presumably arise from NF1 inactivation in S100(+)Schwann cells, but there is no formal proof for this mechanism. We demonstrate that fibro-blasts isolated from neurofibromas carried at least one normal NF1 allele and expressed both NF1 mRNA and protein, whereas the S100(+)cells typically lacked the NF1 transcript. Our findings further indicate that additional molecular events aside from NF1 inactivation in Schwann cells and/or other neural crest derivatives contribute to neurofibroma formation.

Adult↗
PubMed2000

Expression of the tuberous sclerosis complex gene products, hamartin and tuberin, in central nervous system tissues.

Tuberous sclerosis complex (TSC) is a common genetic disorder in which affected individuals can develop mental retardation, developmental brain defects, and seizures. Two genetic loci are responsible for TSC: TSC1 on chromosome 9q and TSC2 on chromosome 16p. Here, we report our analysis of TSC1 (hamartin) and TSC2 (tuberin) protein expression in the central nervous system (CNS). Both tuberin and hamartin are expressed in neurons and astrocytes where they physically interact. In the mouse cerebellum in vivo, tuberin predominantly localizes to the perinuclear region of the Purkinje cell, whereas hamartin is distributed along neuronal or astrocytic processes. In contrast, both hamartin and tuberin demonstrate similar neuronal expression patterns in pure neuronal cultures in vitro. Additionally, hamartin is highly expressed in astrocytes in mixed neuron-glia cultures in vitro, suggesting that hamartin may be important for astrocyte growth control. Unlike tuberin, loss of hamartin expression was not observed in sporadic astrocytomas. These results suggest that tuberin and hamartin may differentially contribute to the CNS pathology in TSC.

Animals↗
PubMed2000

Loss of neurofibromatosis 1 (NF1) gene expression in NF1-associated pilocytic astrocytomas.

The critical role of the neurofibromatosis 1 (NF1) gene as a tumour suppressor has been clearly demonstrated for malignancies arising in NF1 patients. However, little is known about the more common benign tumours, such as the pilocytic astrocytoma. Most NF1-associated astrocytomas are benign and clinically non-progressive, though aggressive tumours are occasionally encountered. In this study, eight pilocytic astrocytomas from six individuals affected with NF1 were analysed for NF1 expression. All eight tumours demonstrated loss of neurofibromin expression by immunohistochemistry, which was confirmed in one case using Western blot analysis. Microsatellite analysis showed loss of a single NF1 allele (LOH) in two of four NF1-associated tumours. These results demonstrate that, in contrast to sporadic astrocytomas, loss of NF1 expression is an important primary genetic event in the pathogenesis of NF1-associated pilocytic astrocytomas.

Adolescent↗