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J K Cowell

Publications and source records attributed to J K Cowell.

At least 37 records · Page 2Linked to original sources
PubMed1999

Expression of oligodendrocyte progenitor cell antigens by gliomas: implications for the histogenesis of brain tumors.

The early events in neoplastic transformation can be understood only by comparison of the neoplastic cell with its nontransformed counterpart. The most common central nervous system gliomas traditionally are thought to arise from mature astrocytes and oligodendrocytes. We examined the possibility that gliomas arise from a population of glia that has properties of oligodendrocyte progenitors. These glial cells express the NG2 chondroitin sulfate proteoglycan and the alpha receptor of platelet-derived growth factor in vivo. We identified NG2 and the alpha receptor of platelet-derived growth factor expression in tissue from seven of seven oligodendrogliomas, three of three pilocytic astrocytomas, and one of five glioblastoma multiforme. These data provide evidence that glial tumors arise from glial progenitor cells. Molecules expressed by these progenitor cells should be considered as targets for novel therapeutics.

Antibodies, Monoclonal↗
PubMed1999

Cloning of TACC1, an embryonically expressed, potentially transforming coiled coil containing gene, from the 8p11 breast cancer amplicon.

Amplification of several chromosomal regions have been observed in human breast carcinomas. One such region, 8p11, is amplified in 10-15% of tumor samples. Although the FGFR1 gene is located close to this region, and is often included within the amplicon, the observation that tumors exhibiting 8p11 amplification do not always overexpress FGFR1 suggests that another gene located close to FGFR1 is involved in the tumorigenic process. We now report the precise location of four expressed sequence tags (ESTs) within this region and the cloning of a novel gene, designated TACC1 (transforming acidic coiled coil gene 1), which encodes an 8 kb transcript and which is expressed at high levels during early embryogenesis. Constitutive expression of this gene under the control of the cytomegalovirus (CMV) promoter in mouse fibroblasts, results in cellular transformation and anchorage independent growth, suggesting that inappropriate expression can impart a proliferative advantage. This observation raises the possibility that amplification of TACC1 could promote malignant growth, thereby making TACC1 an attractive candidate for the gene promoting tumorigenicity as a result of the 8p11 amplification in human breast cancers.

Adult↗
PubMed1999

The third member of the transforming acidic coiled coil-containing gene family, TACC3, maps in 4p16, close to translocation breakpoints in multiple myeloma, and is upregulated in various cancer cell lines.

We have recently identified a novel gene, TACC1 (transforming acidic coiled coil-containing gene 1), which is located close to FGFR1 within a region amplified in breast cancer on human chromosome 8p11. The coiled coil domain of this gene identified a series of cDNAs in the expressed sequence tag database, which suggested the existence of a family of TACC genes comprising at least three family members. We have now characterized the human and mouse TACC3 cDNAs, and demonstrate that this gene is upregulated in various cancer cell lines, and at Embryonic Day 15 in mice, suggesting that the TACC3 protein is involved in the control of cell growth and differentiation. The TACC3 gene maps telomeric to the FGFR3 gene in 4p16.3, close to a region disrupted by translocation breakpoints associated with multiple myeloma. Thus, TACC1, TACC2, and TACC3 map close to the corresponding FGFR1, FGFR2, and FGFR3 genes. The phylogenetic relationship among the three TACC genes is similar to that of the three FGFR family members. These relationships suggest that the FGFR and TACC genes arose from a physically linked ancestral gene pair. Subsequently, this gene pair has undergone two successive rounds of gene duplication to give rise to the three FGFR/TACC gene pairs on chromosomes 4, 8, and 10.

Animals↗
PubMed1999

TTC4, a novel human gene containing the tetratricopeptide repeat and mapping to the region of chromosome 1p31 that is frequently deleted in sporadic breast cancer.

The 1p31 region shows loss of heterozygosity in up to 50% of human breast cancers, indicating the presence of a tumor suppressor gene in this location. We have mapped six novel ESTs to a 15-Mb contig of yeast artificial chromosomes spanning the critical region of 1p31. One of these ESTs was localized within the contig to the region most commonly undergoing loss of heterozygosity in breast cancer. The corresponding gene sequence for this EST was established by cDNA cloning and RACE procedures. This gene is 2 kb long and contains a tetratricopeptide repeat motif and a coiled-coil domain. This family of genes has been implicated in a wide variety of functions, including tumorigenesis. This is the fourth member of the human gene family, and so we have named this gene TTC4. Northern blot analysis demonstrates a ubiquitous pattern of gene expression that includes breast tissue. A preliminary screen of human breast cancer cell lines shows that TTC4 is expressed in all cases, but SSCP analysis of the coding region of this gene following RT-PCR failed to reveal any mutations. Clearly, because of its map location, a more extensive analysis is warranted to establish whether subtle mutations are present in breast cancers.

Amino Acid Sequence↗
PubMed1998

A novel gene, LGI1, from 10q24 is rearranged and downregulated in malignant brain tumors.

Loss of heterozygosity for 10q23-26 is seen in over 80% of glioblastoma multiforme tumors. We have used a positional cloning strategy to isolate a novel gene, LGI1 (Leucine-rich gene-Glioma Inactivated), which is rearranged as a result of the t(10;19)(q24;q13) balanced translocation in the T98G glioblastoma cell line lacking any normal chromosome 10. Rearrangement of the LGI1 gene was also detected in the A172 glioblastoma cell line and several glioblastoma tumors. These rearrangements lead to a complete absence of LGI1 expression in glioblastoma cells. The LGI1 gene encodes a protein with a calculated molecular mass of 60 kD and contains 3.5 leucine-rich repeats (LRR) with conserved flanking sequences. In the LRR domain, LGI1 has the highest homology with a number of transmembrane and extracellular proteins which function as receptors and adhesion proteins. LGI1 is predominantly expressed in neural tissues, especially in brain; its expression is reduced in low grade brain tumors and it is significantly reduced or absent in malignant gliomas. Its localization to the 10q24 region, and rearrangements or inactivation in malignant brain tumors, suggest that LGI1 is a candidate tumor suppressor gene involved in progression of glial tumors.

Amino Acid Sequence↗
PubMed1998

Molecular analysis of two putative tumour suppressor genes, PTEN and DMBT, which have been implicated in glioblastoma multiforme disease progression.

The transition from low grade astrocytoma to glioblastoma multiforme is almost always accompanied by the loss of genetic markers from chromosome 10. Recently two genes, PTEN/MMAC1/TEP1 and DMBT, have been isolated from chromosome 10q. We have analysed these two genes for mutations in 21 primary glioblastomas. An exon by exon screen of the PTEN gene using SSCP failed to identify any mutations in this tumour series. In contrast, 38% of tumours showed intragenic homozygous deletions in the DMBT gene. The fact that the majority of gliomas do not carry mutations in either of these genes suggests that there may still be other genes on chromosome 10 which are important in the development of glioblastoma multiforme.

Agglutinins↗
PubMed1998

Loss of heterozygosity for the short arm of chromosome 7 in sporadic Wilms tumour.

Cytogenetic analysis of Wilms tumours (WT) have shown that abnormalities involving chromosome 7 occur in approximately 25% of tumours. In some cases, these abnormalities involve deletions of the short arm, and are seen as the sole cytogenetic change, strongly suggesting the presence of a tumour suppressor gene in this location. Since loss of heterozygosity (LOH) studies have been crucial in defining chromosomal regions involved in Wilms tumorigenesis, we have analysed 40 sporadic Wilms tumours using a panel of 10 microsatellite polymorphic markers distributed along the length of the chromosome arm. In our series, four tumours (10%) showed allelic loss for 7p markers which is twice the background rate of LOH in WT. The shortest common region of overlap of LOH was located between markers D7S517-D7S503 in band 7p21-15. In one tumour there was evidence for a homozygous, interstitial deletion at a locus within this region. These findings provide strong evidence for the existence of a tumour suppressor gene involved in Wilms tumorigenesis and defines the critical region of the chromosome involved.

Base Sequence↗
PubMed1998

Targeted therapy of human malignant glioma in a mouse model by 2-5A antisense directed against telomerase RNA.

Telomerase is the RNA-protein complex which elongates telomeric DNA (TTAGGG)n and appears to play an important role in cellular immortalization. The almost exclusive expression of telomerase in tumor cells, and not in most normal cells, offers an exciting opportunity for therapy by inhibiting its function. Here, we have investigated the effect of inhibition of telomerase on the growth and survival of human malignant glioma cells in vitro and in vivo by using a 19-mer antisense oligonucleotide against human telomerase RNA linked to a 2',5'-oligoadenylate (2-5A). 2-5A antisense functions by activating the endoribonuclease, RNase L, resulting in the degradation of single stranded, targeted RNA. We have shown that the 2-5A antisense treatment effectively suppressed tumor cell growth and survival in vitro. Furthermore, treatment of tumors grown in nude mice with the antisense oligonucleotide inhibited survival of the tumor cells. TUNEL assays suggest that this effect is mediated through the induction of apoptosis. Targeting telomerase RNA with 2-5A antisense, therefore, may represent an effective and novel approach for treatment of a broad range of cancers.

Animals↗
PubMed1998

A novel missense mutation in patients from a retinoblastoma pedigree showing only mild expression of the tumor phenotype.

We have used single strand conformation polymorphism analysis to study the 27 exons of the RB1 gene in individuals from a family showing 'mild' expression of the retinoblastoma phenotype. In this family affected individuals developed unilateral tumors and, as a result of linkage analysis, unaffected mutation carriers were also identified within the pedigree. A single band shift using SSCP was identified in exon 21 which resulted in a missense mutation converting a cys-->arg at nucleotide position 28 in the exon. The mutation destroyed an NdeI restriction enzyme site. Analysis of all family members demonstrated that the missense mutation co-segregated with patients with tumors or who, as a result of linkage analysis had been predicted to carry the predisposing mutation. These observations point to another region of the RB1 gene where mutations only modify the function of the gene and raise important questions for genetic counseling in families with these distinctive phenotypes.

Female↗
PubMed1998

Inhibition of telomerase increases the susceptibility of human malignant glioblastoma cells to cisplatin-induced apoptosis.

Malignant glioblastomas grow very rapidly and are generally resistant to either DNA-damaging drugs or gamma-irradiation. If tumor cells could be made more susceptible to cell death with treatments, this would clearly represent a significant improvement in the success of treatment. Recently, telomerase has become a focus of interest among oncologists as a target for treating cancer cells. Telomerase elongates telomeric DNA repeats (TTAGGG)n and is important in protecting and replicating DNA. The vast majority of tumor cells, indeed, express telomerase activity whereas normal somatic cells, except for a few cells, do not. Since telomerase is essential for protecting DNA, we may be able to make tumors more sensitive to treatments with DNA-damaging drugs by inhibiting telomerase activity. In this study, we used cis-diamminedichloroplatinum (cisplatin)-sensitive U87-MG cells and cisplatin-resistant U251-MG of human malignant glioblastoma cell lines. U87-MG cells did not express telomerase activity, whereas telomerase was highly detected in U251-MG cells. Interestingly, inhibition of telomerase with an antisense telomerase expression vector not only decreased telomerase activity but also increased susceptibility to cisplatin-induced apoptotic cell death in U251-MG cells. These findings suggest that treatment with antisense telomerase may represent a new chemosensitisation for tumors resistant to anticancer drugs.

Apoptosis↗
PubMed1998

Molecular characterization of the 1p22 breakpoint region spanning the constitutional translocation breakpoint in a neuroblastoma patient with a t(1;10)(p22;q21).

To characterize the breakpoint in a neuroblastoma patient with a constitutional rearrangement we have constructed a yeast artificial chromosome (YAC) contig extending approximately 6 Mbp in the chromosome 1p22 region that spans the D1S435 and D1S236 loci. This contig has been confirmed by the coincidence of a number of markers in different overlapping YACs. For several of these YACs the overlap was demonstrated following the isolation and sequencing of end clones from which STS markers were generated. The majority of the YACs have been shown not to be chimeric either through the analysis of somatic cell hybrids or fluorescence in situ hybridization. Following the establishment of the contig we have been able to construct a physical map of the region that incorporates six STS and three newly assigned eSTS markers. The generation of this physical map has allowed the reordering of markers in the genetic linkage map for 1p. The physical order is; tel-D1S435-D1S188-D1S424-D1S236-D1D415- D1S420. With the reordering of D1S435 we have been able to join this contig with another reported previously, thereby generating a well characterized 15 Mbp YAC contig in the 1p22-31 region. The 6 Mbp contig described here spans the chromosome 1 constitutional translocation break-point seen in a patient with a t(1;10)(p22;q21) and who had a stage 4S neuroblastoma. YAC fragmentation has been used to define a 200 Kb region within this contig containing the 1p22 breakpoint. Restriction enzyme analysis demonstrates that there are three NotI sites in this region, one of which lies close to the translocation breakpoint site.

Chromosomes, Artificial, Yeast↗
PubMed1998

Characterization of the breakpoints in a t(8;13)(p11;q12) translocation from a patient with myeloproliferative disease using fluorescence in situ hybridization.

We used fluorescence in situ hybridization to characterize the molecular position of the breakpoints in a t(8;13)(p11;q12) reciprocal translocation from a patient with an atypical myeloproliferative disorder. This structural chromosome abnormality is characteristic of this specific disease and occurs often as the only chromosome abnormality in the malignant cells. Yeast artificial chromosome (YAC) analysis has demonstrated that the 8p11 breakpoint lies within a region defined by YAC 959A4 and that the 13q12 breakpoint is spanned by YAC 769F9. Identifying the position of the breakpoints in this rearrangement provides the means to search for candidate genes rearranged by this highly specific structural chromosome abnormality.

Adult↗
PubMed1998

Molecular definition of chromosome translocations involving 10q24 and 19q13 in human malignant glioma cells.

Loss of heterozygosity (LOH) analysis has repeatedly implicated the 10q24-26 region as the site of tumor suppressor genes involved in the development of malignant human gliomas. However, deletions of this kind are generally too big to pinpoint the critical genes involved. On the other hand, chromosome translocations frequently interrupt genes important in the development of the phenotype. We have screened a series of cell lines and cultures from primary human brain tumors for translocations involving chromosomes 10 and 19 by using fluorescence in situ hybridization (FISH) and chromosome-specific paints. The T98G cell line carries an apparently reciprocal t(10;19)(q24;q13) translocation, the breakpoints on chromosomes 10 and 19 occurring in a region frequently showing LOH in gliomas as well as oligodendrogliomas and astrocytomas. One glioblastoma tumor, CCF 4, also showed a subtle translocation of chromosome 10 material into the long arm of chromosome 11. FISH analysis of these rearrangements showed that the chromosome 10-specific yeast artificial chromosome (YAC) 912C7 spans the translocation breakpoint in T98G cells and is also present in the material translocated from chromosome 10 in tumor CCF 4. The translocation breakpoint in 19q13 in T98G occurs within a 500-kb region of YAC 751E12. These translocation breakpoints are within the regions showing frequent LOH in brain tumors and provide a more refined tool for the identification of genes in this region involved in tumorigenesis.

Brain Neoplasms↗
PubMed1998

Loss of heterozygosity on chromosome 16 in sporadic Wilms' tumour.

To establish whether loss of heterozygosity (LOH) for chromosome 16q in Wilms' tumours confers an adverse prognosis, DNA from 40 Wilms' tumour/normal pairs were analysed using highly polymorphic microsatellite markers along the length of 16q. Fifteen per cent of tumours showed LOH for 16q. Although the common region of allele loss spanned the 16q24-qter region, a second distinct region of LOH was identified in 16q21. Five out of six tumours showing LOH were either (1) high stage or (2) low stage with unfavourable histology. In addition, there was a higher mortality rate in patients showing LOH for 16q than those that did not. These data strongly support the suggestion that LOH for 16q is associated with an adverse prognosis.

Alleles↗
PubMed1998

Construction of a bacterial artificial chromosome (BAC) contig across the minimally deleted region in 13q14.3 in B-cell chronic lymphocytic leukemia.

Loss of heterozygosity (LOH) analysis in B-cell chronic lymphocytic leukemia (BCLL) has indicated that a frequent genetic event is loss of alleles from an approximately 500 kb region in 13q14.3, distal to the retinoblastoma gene. We have used DNA markers from this region to isolate and characterize a series of bacterial artificial chromosomes (BACs) which span the region between markers D13S319 and D13S25, which represents the common region of LOH. This entire region appears to be contained within only two minimally overlapping BACs, representing a maximum distance of approximately 350 kb. This BAC contig has been used to position known STS, EST and gene markers within the region. We have also used a modified differential display/RNA fingerprinting procedure designed to isolated transcribed sequences from YACs to isolate two transcribed units from the region which have also been positioned within the contig. The construction of a BAC contig with minimal redundancy provides the ideal resources from which to begin to identify candidate genes related to BCLL.

Blotting, Southern↗
PubMed1998

NB4S, a member of the TBC1 domain family of genes, is truncated as a result of a constitutional t(1;10)(p22;q21) chromosome translocation in a patient with stage 4S neuroblastoma.

Molecular cloning of the breakpoints of a t(1;10)(p22q21) constitutional translocation breakpoint in a patient with stage 4S neuroblastoma has identified two genes which are fused in-frame to generate a novel gene. The 1p22 gene, which we have called NB4S , encodes a 7.5 kb transcript with an 810 amino acid open reading frame and is expressed in a wide variety of tissues. NB4S has >88% homology with the mouse EVI -5 gene within the coding region and shows strong homology over a 200 amino acid region with TBC1 box motif genes involved in cell growth and differentiation. The C-teminal end of the protein contains a number of coiled coil domains, indicating a possible protein-protein binding function. The chromosome 10 breakpoint interrupts a novel transcript (TRNG10) which could only be detected in tumor cells. This transcript has no exon/intron structure or significant open reading frame, suggesting that it is a structural RNA which is transcribed but not translated. The chromosome rearrangement creates a fusion gene product which combines the TBC1 motif of NB4S with a polyadenylation signal from TRNG10 , potentially generating a truncated protein with oncogenic properties.

Animals↗