Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P43146 (tumour suppressor)
 5,935 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Malignant rhabdoid tumours (MRTs) are extremely aggressive cancers of early childhood. They can occur in various locations, mainly the kidney, brain and soft tissues. Cytogenetic and molecular analyses have shown that the deletion of region 11.2 of the long arm of chromosome 22 (22q11.2) is a recurrent genetic characteristic of MRTs, indicating that this locus may encode a tumour suppressor gene. Here we map the most frequently deleted part of chromosome 22q11.2 from a panel of 13 MRT cell lines. We observed six homozygous deletions that delineate the smallest region of overlap between the cell lines. This region is found in the hSNF5/INI1 gene, which encodes a member of the chromatin-remodelling SWI/SNF multiprotein complexes. We analysed the sequence of hSNF5/INI1 and found frameshift or nonsense mutations of this gene in six other cell lines. These truncating mutations of one allele were associated with the loss of the other allele. Identical alterations were observed in corresponding primary tumour DNAs but not in matched constitutional DNAs, indicating that they had been acquired somatically. The observation of bi-allelic alterations of hSNF5/INI1 in MRTs suggests that loss-of-function mutations of hSNF5/INI1 contribute to oncogenesis.
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PMID:Truncating mutations of hSNF5/INI1 in aggressive paediatric cancer. 967 7

Chromatin organization plays a key role in the regulation of gene expression. The evolutionarily conserved SWI/SNF complex is one of several multiprotein complexes that activate transcription by remodelling chromatin in an ATP-dependent manner. SWI2/SNF2 is an ATPase whose homologues, BRG1 and hBRM, mediate cell-cycle arrest; the SNF5 homologue, INI1/hSNF5, appears to be a tumour suppressor. A search for INI1-interacting proteins using the two-hybrid system led to the isolation of c-MYC, a transactivator. The c-MYC-INI1 interaction was observed both in vitro and in vivo. The c-MYC basic helix-loop-helix (bHLH) and leucine zipper (Zip) domains and the INI1 repeat 1 (Rpt1) region were required for this interaction. c-MYC-mediated transactivation was inhibited by a deletion fragment of INI1 and the ATPase mutant of BRG1/hSNF2 in a dominant-negative manner contingent upon the presence of the c-MYC bHLH-Zip domain. Our results suggest that the SWI/SNF complex is necessary for c-MYC-mediated transactivation and that the c-MYC-INI1 interaction helps recruit the complex.
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PMID:c-MYC interacts with INI1/hSNF5 and requires the SWI/SNF complex for transactivation function. 1031 72

The mammalian SWI/SNF complex is a chromatin remodelling complex that uses the energy of ATP hydrolysis to facilitate access of transcription factors to regulatory DNA sequences. This complex, that was initially described as a co-factor for nuclear receptors, has recently been associated with the control of cell growth. Two of the subunits known as BRG-1 and brm can associate with the Retinoblastoma tumour suppressor gene product and co-operate with this protein for repression of E2F activity. In addition, expression of brm is frequently down-regulated upon cellular transformation and re-introduction of this protein into fibroblasts transformed by activated ras induces partial reversion of the transformed phenotype. Finally, the hSNF5/INI1 gene, encoding another subunit of the SWI/SNF complex, is subject to bi-allelic mutations in rhabdoid tumours, a very aggressive form of paediatric cancers. These observations provide a novel link between malignant transformation and chromatin remodelling machineries.
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PMID:The mammalian SWI/SNF complex and the control of cell growth. 1044 Oct 69

Rhabdoid tumours have been shown to carry somatic mutations in the INI1 (SMARCB1/hSNF5) gene. A considerable fraction of these tumours exhibit allelic losses on chromosome 22. Allelic loss on 22q also is characteristic for meningiomas, however most of these alterations are considered to be associated with mutations of the NF2 gene. We examined a series of 126 meningiomas for alterations in the INI1 gene. Four identical somatic mutations in exon 9 were detected resulting in an exchange of Arg to His in position 377 of INI1. Our observations were reproduced both by using DNA from a new round of extraction and by employing overlapping primers. This mutational hotspot therefore appears to be an important target in the formation of a fraction of meningiomas. In addition, 4 novel polymorphisms of INI1 were characterized. Our data indicate that the INI1 is a second tumour suppressor gene on chromosome 22 that may be important for the genesis of meningiomas.
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PMID:INI1 mutations in meningiomas at a potential hotspot in exon 9. 1116 77

Medulloblastomas (MBs) are malignant primitive neuroectodermal tumours (PNETs) of the cerebellum occurring predominantly in childhood. The association of monosomy of chromosome 22 with MB is controversial. Atypical teratoid/rhabdoid tumours (AT/RTs) of the brain share clinical and histological features with MBs and supratentorial PNETs (sPNETs). In particular, AT/RTs can be misdiagnosed as MBs and sPNETs because AT/RTs frequently contain areas of primitive neuroepithelial cells similar to PNETs. Recently, mutations of the tumour suppressor gene hSNF5/INI1, located on 22q11.23, have been described in AT/RTs, MBs and sPNETs, with conflicting data on the prevalence of hSNF5/INI1 mutations in the latter entities. Therefore, we screened MBs for point mutations and homozygous deletions of the hSNF5/INI1 tumour suppressor gene. In 90 MBs, no mutations of the hSNF5/INI1 gene were identified. Thus, our study virtually rules out hSNF5/INI1 as a tumour suppressor gene involved in the pathogenesis of medulloblastoma.
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PMID:Human medulloblastomas lack point mutations and homozygous deletions of the hSNF5/INI1 tumour suppressor gene. 1197

The hSNF5/INI1 gene encodes a member of the SWI/SNF chromatin remodelling complexes. It was recently identified as a tumour suppressor gene mutated in sporadic and hereditary Malignant Rhabdoid Tumours (MRT). However, the role of hSNF5/INI1 loss-of-function in tumour development is still unknown. Here, we show that the ectopic expression of wild-type hSNF5/INI1, but not that of truncated versions, leads to a cell cycle arrest by inhibiting the entry into S phase of MRT cells. This G1 arrest is associated with down-regulation of a subset of E2F targets including cyclin A, E2F1 and CDC6. This arrest can be reverted by coexpression of cyclin D1, cyclin E or viral E1A, whereas it cannot be counteracted by pRB-binding deficient E1A mutants. Moreover, hSNF5/INI1 is not able to arrest cells lacking a functional pRB. These observations suggest that the hSNF5/INI1-induced G1 arrest is dependent upon the presence of a functional pRB. However, the observation that a constitutively active pRB can efficiently arrest MRT cells indicates that hSNF5/INI1, at the difference of the ATPase subunits of the SWI/SNF complex, is dispensable for pRB function. Altogether, these data show that hSNF5/INI1 is a potent regulator of the entry into S phase, an effect that may account for its tumour suppressor role.
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PMID:A key role of the hSNF5/INI1 tumour suppressor in the control of the G1-S transition of the cell cycle. 1222 44

Preimplantation genetic diagnosis (PGD) has recently been offered for couples with an inherited predisposition for late onset disorders. This paper presents the results of PGD for a group of couples at risk for producing children with cancer predisposition. Using a standard IVF procedure, oocytes or embryos were tested for different mutations predisposing to cancer, preselecting and transferring only mutation-free embryos back to the patients. The procedure was performed for patients with predisposition to familial adenomatous polyposis coli (FAP), Von Hippel-Lindau syndrome (VHL), retinoblastoma, Li-Fraumeni syndrome, determined by p53 tumour suppressor gene mutations, neurofibromatosis types I and II and familial posterior fossa brain tumour (hSNF5). Overall, 20 PGD cycles were performed for 10 couples, resulting in preselection and transfer of 40 mutation-free embryos, which resulted in five unaffected clinical pregnancies and four healthy children born by the present time. Despite the controversy of PGD use for late onset disorders, the data demonstrate the usefulness of this approach as the only acceptable option for at-risk couples to avoid the birth of children with an inherited predisposition to cancer, and to have a healthy child.
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PMID:Preimplantation genetic diagnosis for cancer predisposition. 1241 39

Choroid plexus carcinomas (CPC) have been shown to carry mutations in the hSNF5/INI1 gene on chromosomal arm 22q11.2. A recent study on choroid plexus papillomas (CPP) and CPC revealed frequent losses of chromosomal portions on the long arm of chromosome 22 (-22q). The region harbouring hSNF5/INI1 was affected in 47% of the CPP and 73% of the CPC, respectively. -22q occurred more frequently in adult than in infantile CPP suggesting different pathogenetic pathways for these tumours. These findings may indicate a potential tumour suppressor gene function of hSNF5/INI1 in a subset of choroid plexus tumours. In order to examine its potential role in the pathogenesis of choroid plexus tumours, we analysed exons 1-9 of hSNF5/INI1 by SSCP analysis in a series of 21 formalin-fixed and paraffin-embedded CPP. No alterations in migratory patterns were detected. These data indicate that somatic point mutations of hSNF5/INI1 do not play a role in the pathogenesis of CPP and that CPP and CPC may arise by two different molecular pathways.
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PMID:No evidence of hSNF5/INI1 point mutations in choroid plexus papilloma. 1517 83

Malignant rhabdoid tumours (MRT) are highly aggressive cancers of early childhood that arise in different organs or tissues. The unifying criterion for these tumours is the presence of inactivating mutations of the hSNF5/INI1 tumour suppressor gene which encodes a core subunit of the chromatin remodelling SWI/SNF complex. Using a variety of markers we analysed the phenotypic traits of MON and DEV cell lines derived respectively from an undifferentiated abdominal MRT and from a brain MRT. DEV cells express spontaneously a wide range of neural and glial markers. It can be induced to differentiate into the neural lineage following hSNF5/INI1 expression with appearance of neurite processes, strong increase of neural markers and decrease of glial markers. A less pronounced neural differentiation is also observed with MON cells, which possess more primitive polyphenotypic features with positivity for markers from the three embryonic layers. Finally, we show that the neural differentiation of rat PC12 cells in the presence of nerve growth factor (NGF) is strongly impaired when hSNF5/INI1 expression is inhibited by RNA interference. Altogether these results indicate that hSNF5/INI1 is an essential subunit for SWI/SNF-dependant induction of neural differentiation programs. Further experiments should enable documentation of whether it provides instructive or permissive signals for differentiation.
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PMID:The tumour suppressor hSNF5/INI1 controls the differentiation potential of malignant rhabdoid cells. 1690 31

Rhabdoid tumours (RTs) are rare but highly aggressive tumours of childhood. Their rarity and their miscellaneous locations make the diagnosis particularly challenging for pathologists. Central nervous system and peripheral RTs have been associated with biallelic inactivation of the hSNF5/INI1/SMARCB1 (hSNF5/INI1) tumour suppressor gene. Immunohistochemistry (IHC) with a monoclonal anti-hSNF5/INI1 antibody has recently been proposed as an efficient diagnostic tool for RTs. We have conducted a retrospective study of 55 tumours referred to our institution with a suspicion of RT. This analysis included pathological review, IHC with anti-hSNF5/INI1 antibody, and molecular investigation using quantitative DNA fluorescent analysis and sequencing of the nine exons of hSNF5/INI1. The molecular lesion could be detected in 37 of the 39 cases exhibiting negative staining for hSNF5/INI1. In the two discrepant cases, the lack of detection of genetic abnormality was probably owing to the presence of a high number of non-tumour cells in the samples. This indicates that hSNF5/INI1 IHC is very sensitive and highly specific for the detection of hSNF5/INI1 loss-of-function. Among the 38 cases with typical RT histological features, six failed to exhibit hSNF5/INI1 mutation and stained positive for hSNF5/INI1. This strongly supports the evidence of a second genetic locus, distinct from hSNF5/INI1, associated with RT. Conversely, seven tumours with histological features poorly compatible with RT stained negative for hSNF5/INI1; they nevertheless exhibited an age of onset and a clinical behaviour similar to RT. This suggests that hSNF5/INI1 inactivation is not strictly limited to typical RT but characterizes a wider family of hSNF5/INI1-deficient tumours. Consequently, we believe that anti-hSNF5/INI1 IHC should be performed widely, even when the pathological characteristics are not typical. The molecular investigation should be performed in infants when a rhabdoid predisposition syndrome is suspected.
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PMID:hSNF5/INI1-deficient tumours and rhabdoid tumours are convergent but not fully overlapping entities. 1715 49


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