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F G Barr

Publications and source records attributed to F G Barr.

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

EWS-FLI1 and EWS-ERG gene fusions are associated with similar clinical phenotypes in Ewing's sarcoma.

PURPOSE: There are a variety of solid tumors in which alternative chromosomal translocations generate related fusion products. In alveolar rhabdomyosarcoma and synovial sarcoma, these variant fusions have been found to have major clinical significance. We investigated whether the two alternative gene fusion products, EWS-FLI1 and EWS-ERG, define different clinical subsets within the Ewing's sarcoma family of tumors. PATIENTS AND METHODS: We selected 30 cases of Ewing's sarcoma with the EWS-ERG gene fusion and 106 cases with the EWS-FLI1 fusion. Clinical data were obtained for each case and compared with the molecular diagnostic findings. RESULTS: There were no significant clinical differences observed between the two groups in age of diagnosis, sex, metastasis at diagnosis, primary site, event-free survival, or overall survival. CONCLUSION: Differences in the C-terminal partner in the Ewing's sarcoma family gene fusions are not associated with significant phenotypic differences.

Adolescent↗
PubMed1999

FKHR binds the insulin response element in the insulin-like growth factor binding protein-1 promoter.

The insulin response element (IRE) in the IGFBP-1 promoter, and in other gene promoters, contains a T(A/G)TTT motif essential for insulin inhibition of transcription. Studies presented here test whether FKHR may be the transcription factor that confers insulin inhibition through this IRE motif. Immunoblots using antiserum to the synthetic peptide FKHR413-430, RNase protection, and Northerns blots show that FKHR is expressed in HEP G2 human hepatoma cells. Southwestern blots, electromobility shift assays, and DNase I protection assays show that Escherichia coli-expressed GST-FKHR binds specifically to IREs from the IGFBP-1, PEPCK and TAT genes; however, unlike HNF3beta, another protein proposed to be the insulin regulated factor, GST-FKHR does not bind the insulin unresponsive G/C-A/C mutation of the IGFBP-1 IRE. When HEP G2 cells were cotransfected with FKHR expression vectors and with IGFBP-1 promoter plasmids containing either native or mutant IREs, FKHR expression induced a 5-fold increase in activity of the native IGFBP-1 promoter but no increase in activity of promoter constructs containing insulin unresponsive IRE mutants. These data suggest that FKHR, and/or a related family member, is the important T(G/A)TTT binding protein that confers the inhibitory effect of insulin on gene transcription.

DNA-Binding Proteins↗
PubMed1999

Conservation of an insulin response unit between mouse and human glucose-6-phosphatase catalytic subunit gene promoters: transcription factor FKHR binds the insulin response sequence.

Because overexpression of the glucose-6-phosphatase catalytic subunit (G-6-Pase) in both type 1 and type 2 diabetes may contribute to the characteristic increased rate of hepatic glucose production, we have investigated whether the insulin response unit (IRU) identified in the mouse G-6-Pase promoter is conserved in the human promoter. A series of human G-6-Pase-chloramphenicol acetyltransferase (CAT) fusion genes was transiently transfected into human HepG2 hepatoma cells, and the effect of insulin on basal CAT expression was analyzed. The results suggest that the IRU identified in the mouse promoter is conserved in the human promoter, but that an upstream multimerized insulin response sequence (IRS) motif that is only found in the human promoter appears to be functionally inactive. The G-6-Pase IRU comprises two distinct promoter regions, designated A and B. Region B contains an IRS, whereas region A acts as an accessory element to enhance the effect of insulin, mediated through region B, on basal G-6-Pase gene transcription. We have previously shown that the accessory factor binding region A is hepatocyte nuclear factor-1, and we show here that the forkhead protein FKHR is a candidate for the insulin-responsive transcription factor binding region B.

Animals↗
PubMed1999

Cytokeratin-negative desmoplastic small round cell tumor: a report of two cases emphasizing the utility of reverse transcriptase-polymerase chain reaction.

Desmoplastic small round cell tumor (DSRCT) is a unique, highly aggressive neoplasm that chiefly affects male adolescents and young adults. This tumor is characterized by nests of small undifferentiated cells that show immunohistochemical evidence of epithelial, mesenchymal, and neural differentiation. We report two cases of DSRCT that lacked immunohistochemical evidence of epithelial differentiation, but were found to have the fusion transcripts characteristic of this tumor. Both patients (a 41-year-old male and a 31-year-old female) presented with large intra-abdominal masses. After diagnostic biopsy, both were treated with multi-agent chemotherapy. One patient expired 18 days after diagnosis, and the other is currently alive 28 months later. Histologically, both tumors had the characteristic features of DSRCT and were composed of small round cells with hyperchromatic nuclei and scanty cytoplasm. In one of the cases, perinuclear intracytoplasmic hyaline inclusions were seen. Immunohistochemically, neither case expressed any of the epithelial markers tested, including AE1/AE3, CAM 5.2 and EMA. Both tumors were diffusely immunoreactive for desmin with a prominent globoid "dot-like" pattern of staining in one case. Both tumors stained for vimentin, neuron specific enolase, and synaptophysin, but were negative for CD99, muscle-specific actin, and myogenin. Reverse transcriptase-polymerase chain reaction revealed EWS-WT1 fusion transcripts characteristic of this neoplasm. In conclusion, we describe two cases of DSRCT that lacked immunohistochemical evidence of epithelial differentiation but had histologic and other immunohistochemical features which suggested this diagnosis. The ability to confirm the diagnosis of this rare tumor using molecular genetic techniques is particularly useful in those cases with unusual histologic or immunophenotypic features.

Abdominal Neoplasms↗
PubMed1998

Up-regulation of MET but not neural cell adhesion molecule expression by the PAX3-FKHR fusion protein in alveolar rhabdomyosarcoma.

The 2;13 chromosomal translocation in alveolar rhabdomyosarcoma generates the chimeric protein PAX3-FKHR, which is a powerful transcriptional activator. We hypothesize that PAX3-FKHR regulates downstream effector genes involved in rhabdomyosarcoma tumorigenesis. We evaluated alterations in expression of MET and neural cell adhesion molecule that were proposed previously as downstream targets of wild-type PAX3. We used a myogenic tumor cell culture system and rhabdomyosarcoma tumor specimens to assess candidate gene expression in relationship to various PAX3-FKHR expression levels. We demonstrate that the expression of MET, but not neural cell adhesion molecule, correlates significantly with PAX3-FKHR expression. These findings indicate that MET, which encodes a receptor involved in growth and motility signaling, is a downstream target of PAX3-FKHR in alveolar rhabdomyosarcoma.

Cells, Cultured↗
PubMed1998

Structural analysis of PAX3 genomic rearrangements in alveolar rhabdomyosarcoma.

In the pediatric cancer alveolar rhabdomyosarcoma, the (2;13)(q35;q14) translocation juxtaposes PAX3 and FKHR to produce a chimeric PAX3-FKHR gene. With the use of Southern blot methodology, genomic rearrangements of PAX3 intron 7 were detected in 23 of 23 fusion-positive alveolar rhabdomyosarcomas and were not detected in 19 fusion-negative embryonal rhabdomyosarcomas. Rearrangements corresponding to the reciprocal FKHR-PAX3 fusion were detected in 21 of 23 PAX3-FKHR-positive cases, though FKHR-PAX3 transcripts were detected in only 15 of 23 cases. Mapping experiments demonstrated that breakpoints occurred throughout this 17.5 kb PAX3 intron and, in 12 of 23 cases, breakpoints clustered within a 4.5-kb region at the 3' end of the intron. Chromatin analysis revealed a prominent DNase I hypersensitive site at the 5' end of the intron but did not indicate any other DNA-protein interactions that might have affected the breakpoint distribution. Sequence analysis identified AT-rich regions within the 3' cluster, as well as alternating purine-pyrimidine and homopyrimidine elements at the borders of this cluster. These finding suggest that translocation breakpoints are constrained to PAX3 intron 7 primarily by functional boundaries related to the flanking exons and may be secondarily affected by sequence features within this intron.

Chromosomes, Human, Pair 13↗
PubMed1998

Translocations, cancer and the puzzle of specificity.

The finding of acquired chromosomal translocations that are consistently associated with specific tumour types supports the premise of lineage-specific mechanisms of tumorigenesis. We review the evidence indicating that the specificity of these translocations and the corresponding gene fusions is related to biological constraints at the level of recombination, expression, and protein function. A dynamic relationship between the gene fusion and the cellular environment is proposed in which the environment influences the selection of oncogenic fusions and the oncogenic fusion in turn influences the cellular environment.

Animals↗
PubMed1998

EWS-FLI1 fusion transcript structure is an independent determinant of prognosis in Ewing's sarcoma.

PURPOSE: More than 90% of Ewing's sarcomas (ES) contain a fusion of the EWS and FLI1 genes, due to the t(11;22)(q24;q12) translocation. At the molecular level, the EWS-FLI1 rearrangements show great diversity. Specifically, many different combinations of exons from EWS and FLI1 encode in-frame fusion transcripts and result in differences in the length and composition of the chimeric protein, which functions as an oncogenic aberrant transcription factor. In the most common fusion type (type 1), EWS exon 7 is linked in frame with exon 6 of FLI1. As the fundamental pathogenetic lesion in ES, the molecular heterogeneity of these fusion transcripts may have functional and clinical significance. PATIENTS AND METHODS: We performed a clinical and pathologic analysis of 112 patients with ES in which EWS-FLI1 fusion transcripts were identified by reverse-transcriptase polymerase chain reaction (RT-PCR). Adequate treatment and follow-up data were available in 99 patients treated with curative intent. Median follow-up in these 99 patients was 26 months (range, 1 to 140 months). Univariate and multivariate survival analyses were performed that included other prognostic factors, such as age, tumor location, size, and stage. RESULTS: Among the 99 patients suitable for survival analysis, the tumors in 64 patients contained the type 1 fusion and in 35 patients contained less common fusion types. Stage at presentation was localized in 74 patients and metastatic in 25. Metastases (relative risk [RR] = 2.6; P = .008), and type 1 EWS-FLI1 fusion (RR = 0.37; P = .014) were, respectively, independent negative and positive prognostic factors for overall survival by multivariate analysis. Among 74 patients with localized tumors, the type 1 EWS-FLI1 fusion was also a significant positive predictor of overall survival (RR = 0.32; P = .034) by multivariate analysis. CONCLUSION: EWS-FLI1 fusion type appears to be prognostically relevant in ES, independent of tumor site, stage, and size. Further studies are needed to clarify the biologic basis of this phenomenon.

Adolescent↗
PubMed1997

Regulated expression of the diphtheria toxin A chain by a tumor-specific chimeric transcription factor results in selective toxicity for alveolar rhabdomyosarcoma cells.

Alveolar rhabdomyosarcoma (ARMS) cells often harbor one of two unique chromosomal translocations, either t(2;13)(q35;q14) or t(1;13)(p36;q14). The chimeric proteins expressed from these rearrangements, PAX3-FKHR and PAX7-FKHR, respectively, are potent transcriptional activators. In an effort to exploit these unique cancer-specific molecules to achieve ARMS-specific expression of therapeutic genes, we have studied the expression of a minimal promoter linked to six copies of a PAX3 DNA binding site, prs-9. In transient transfections, expression of the prs-9-regulated reporter genes was approximately 250-fold higher than expression of genes lacking the prs-9 sequences in cell lines derived from ARMS, but remained at or below baseline levels in other cells. High expression of these prs-9-regulated genes was also observed in a cancer cell line that lacks t(2;13) but was stably transfected with a plasmid expressing PAX3-FKHR. Transfection of a plasmid containing the diphtheria toxin A chain gene regulated by prs-9 sequences (pA3-6PED) was selectively cytotoxic for PAX3-FKHR-expressing cells. This was shown by inhibition of gene expression from cotransfected plasmids and by direct cytotoxicity after transfected cells were isolated by cell sorting. Gene transfer of pA3-6PED may thus be useful as a cancer-specific treatment strategy for t(2;13)- or t(1;13)-positive ARMS. Furthermore, gene transfer of fusion protein-regulated toxin genes might also be applied to the treatment of other cancers that harbor cancer-specific chromosomal translocations involving transcription factors.

DNA-Binding Proteins↗
PubMed1997

Translin recognition site sequences flank chromosome translocation breakpoints in alveolar rhabdomyosarcoma cell lines.

Alveolar rhabdomyosarcoma is characterized by a t(2;13)(q35;q14) chromosome translocation, which leads to the fusion of the PAX3 and the FKHR genes. The resulting fusion gene encodes a chimeric protein which has aberrant transcriptional activity. We report the molecular definition of the genomic breakpoints on both derivative chromosomes in one case and the derivative chromosome 13 breakpoints in two other cases. The DNA sequences adjacent to the breakpoints on the derivative chromosome 13 are remarkable for their resemblance to recognition sequences for the protein translin. Gel shift analyses confirm that these sequences bind translin. These findings suggest that translin may not only be important in the genesis of chromosomal translocations in lymphoid malignancy, but also in translocations found in solid tumours.

Base Sequence↗
PubMed1997

Fusion genes resulting from alternative chromosomal translocations are overexpressed by gene-specific mechanisms in alveolar rhabdomyosarcoma.

Chromosomal translocations identified in hematopoietic and solid tumors result in deregulated expression of protooncogenes or creation of chimeric proteins with tumorigenic potential. In the pediatric solid tumor alveolar rhabdomyosarcoma, a consistent t(2;13)(q35;q14) or variant t(1;13)(p36;q14) translocation generates PAX3-FKHR or PAX7-FKHR fusion proteins, respectively. In this report, we demonstrate that in addition to functional alterations these translocations are associated with fusion product overexpression. Furthermore, PAX3-FKHR and PAX7-FKHR overexpression occurs by distinct mechanisms. Transcription of PAX3-FKHR is increased relative to wild-type PAX3 by a copy number-independent process. In contrast, PAX7-FKHR overexpression results from fusion gene amplification. Thus, gene-specific mechanisms were selected to overexpress PAX3-FKHR and PAX7-FKHR in alveolar rhabdomyosarcoma, presumably due to differences in regulation between the wild-type loci. We postulate that these overexpression mechanisms ensure a critical level of gene product for the oncogenic effects of these fusions.

Chromosomes, Human, Pair 1↗
PubMed1997

Radiation-associated synovial sarcoma.

We describe a case of synovial sarcoma occurring in a 36 year-old woman, 8 years after radiation therapy for Hodgkin's disease. The tumor showed histological, immunohistochemical, ultrastructural, and molecular features diagnostic of synovial sarcoma. To our knowledge, this is the first report of a fully documented case of radiation associated synovial sarcoma.

Adult↗
PubMed1997

Chromosomal translocations involving paired box transcription factors in human cancer.

The PAX genes encode a family of transcription factors that control development within the neural, myogenic, lymphoid, and a variety of other lineages. These proteins are postulated to regulate expression of gene products that function in the control of cellular processes are fundamental to the development of cancer, and thus genetic alterations of these genes may contribute to neoplastic development within these lineages. In support of this premise, several PAX genes have been shown to be targets of consistent chromosomal translocations associated with specific tumor types. The t(2;13) and t(1;13) translocations associated with the myogenic soft tissue cancer alveolar rhabdomyosarcoma fuse portions of the PAX3 or PAX7 gene with a portion of the FKHR gene to generate novel fusion proteins. The t(9;14) translocation associated with the B cell tumor lymphoplasmacytoid lymphoma juxtaposes the PAX5 gene into the vicinity of the IGH locus to deregulate PAX5 expression. This review will examine the molecular basis of these translocations and the role of altered function or expression of paired box transcription factors in the process of tumorigenesis.

Cell Transformation, Neoplastic↗
PubMed1997

Detection of gene fusions in rhabdomyosarcoma by reverse transcriptase-polymerase chain reaction assay of archival samples.

Alveolar rhabdomyosarcoma is a pediatric soft-tissue tumor that is often difficult to distinguish from other small round-cell tumors. The PAX3-FKHR and PAX7-FKHR gene fusions that result from chromosomal translocations in this tumor provide potential molecular diagnostic markers. To apply these molecular markers to commonly available archival material, we used reverse transcriptase-polymerase chain reaction and oligonucleotide hybridization methodology to develop an assay capable of identifying PAX3-FKHR and PAX7-FKHR fusion transcripts in formalin-fixed, paraffin-embedded tissue. Use of a control assay for wild-type FKHR mRNA indicated that RNA was successfully isolated, reverse-transcribed, and amplified in 15 of 16 archival cases. Comparison of assay results for the PAX3-FKHR and PAX7-FKHR fusions with standard molecular assays of paired frozen material revealed that all eight cases of known fusion-positive rhabdomyosarcoma were correctly identified and distinguished as PAX3-FKHR or PAX7-FKHR. The seven cases of known fusion-negative rhabdomyosarcoma showed no evidence of either product. These results indicate that we have developed a molecular assay that accurately identifies the fusion transcripts characteristic of alveolar rhabdomyosarcoma in archival samples. This assay will be useful for diagnosis and for retrospective clinicopathologic correlative studies.

Base Sequence↗
PubMed1997

Common and variant gene fusions predict distinct clinical phenotypes in rhabdomyosarcoma.

PURPOSE: We evaluated the clinical features of the common PAX3-FKHR and variant PAX7-FKHR gene fusions observed in rhabdomyosarcoma. PATIENTS AND METHODS: Reverse-transcriptase polymerase chain reaction (RT-PCR) assays were used to detect the gene fusions in 34 cases of rhabdomyosarcoma. Clinical data were obtained retrospectively and compared with the molecular results. RESULTS: The PAX3-FKHR and PAX7-FKHR gene fusions were present in tumors from 18 and 16 patients, respectively. The group with a PAX7-FKHR fusion was younger (P = .01) and presented more often with an extremity lesion (82% v 22%; P = .001). PAX7-FKHR tumors were more often localized than PAX3-FKHR tumors (P = .03). In patients with metastatic disease at diagnosis, the patterns were different: PAX7-FKHR patients had metastatic disease that involved only bone (n = 2) and distant nodes (n = 2), while the PAX3-FKHR group had multiple sites involved, including bone (n = 7), marrow (n = 7), lungs (n = 3), distant nodes (n = 2), skin (n = 1), and brain (n = 1). No significant difference in relapse rate was observed. A trend toward improved overall survival in the PAX7-FKHR group was noted (P = .09). Event-free survival for this PAX7-FKHR group was significantly longer (P = .04). CONCLUSION: Our results suggest that the common PAX3-FKHR and the variant PAX7-FKHR fusions are associated with distinct clinical phenotypes. Identification of fusion gene status may be a useful diagnostic tool in rhabdomyosarcoma.

Adolescent↗
PubMed1996

Minimal disease detection in patients with alveolar rhabdomyosarcoma using a reverse transcriptase-polymerase chain reaction method.

BACKGROUND: Polymerase chain reaction (PCR) assays that detect fusion genes resulting from consistent chromosomal translocations have been used to detect minimal residual disease, primarily in hematologic malignancies. Molecular assays have been developed recently that detect the PAX3-FKHR or PAX7-FKHR fusion transcript resulting from the t(2; 13) or t(1; 13) translocation consistently observed in alveolar rhabdomyosarcoma. Because of the tumor's propensity to disseminate widely, our aim was to determine whether or not reverse transcriptase-PCR assays could detect submicroscopic disease in bone marrow or peripheral blood specimens. METHODS: We analyzed 19 bone marrow samples from 11 patients with a known gene fusion in their primary tumor. Specimens were collected at diagnosis, remission, and relapse. Fourteen peripheral blood samples were obtained serially from 5 of these patients. A reverse transcriptase-PCR assay was used to detect the presence of the PAX3-FKHR or PAX7-FKHR fusion transcript. These results were compared with the results of microscopic examination of the bone marrow. Medical records of all 11 patients were reviewed. RESULTS: Adequate amplifiable RNA was obtained in 17 of 19 marrow samples. The PCR assay detected fusion products in all 4 specimens obtained from 3 patients with histologic evidence of bone marrow involvement. In addition, PAX3-FKHR fusion products were detected in bone marrows from 2 patients for whom there was no histologic evidence of disease. The fusion transcripts were not detected in any of the peripheral blood samples. CONCLUSIONS: The detection of submicroscopic disease is possible in alveolar rhabdomyosarcoma patients using PCR. These assays may have a role in staging, monitoring therapy, purging protocols for autologous bone marrow transplantation, and post therapy follow-up. Larger prospective studies are needed to address the clinical relevance of these results.

Bone Marrow↗
PubMed1996

The hybrid PAX3-FKHR fusion protein of alveolar rhabdomyosarcoma transforms fibroblasts in culture.

Pediatric alveolar rhabdomyosarcoma is characterized by a chromosomal translocation that fuses parts of the PAX3 and FKHR genes. PAX3 codes for a transcriptional regulator that controls developmental programs, and FKHR codes for a forkhead-winged helix protein, also a likely transcription factor. The PAX3-FKHR fusion product retains the DNA binding domains of the PAX3 protein and the putative activator domain of the FKHR protein. The PAX3-FKHR protein has been shown to function as a transcriptional activator. Using the RCAS retroviral vector, we have introduced the PAX3-FKHR gene into chicken embryo fibroblasts. Expression of the PAX3-FKHR protein in these cells leads to transformation: the cells become enlarged, grow tightly packed and in multiple layers, and acquire the ability for anchorage-independent growth. This cellular transformation in vitro will facilitate studies on the mechanism of PAX3-FKHR-induced oncogenesis.

Animals↗