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Jonathan A Fletcher

Publications and source records attributed to Jonathan A Fletcher.

At least 37 records · Page 2Linked to original sources
PubMed2004

Overexpression, amplification, and androgen regulation of TPD52 in prostate cancer.

Gains in the long arm of chromosome 8 (8q) are believed to be associated with poor outcome and the development of hormone-refractory prostate cancer. Based on a meta-analysis of gene expression microarray data from multiple prostate cancer studies (D. R. Rhodes et al., Cancer Res 2002;62:4427-33), a candidate oncogene, Tumor Protein D52 (TPD52), was identified in the 8q21 amplicon. TPD52 is a coiled-coil motif-bearing protein, potentially involved in vesicle trafficking. Both mRNA and protein levels of TPD52 were highly elevated in prostate cancer tissues. Array comparative genomic hybridization and amplification analysis using single nucleotide polymorphism arrays demonstrated increased DNA copy number in the region encompassing TPD52. Fluorescence in situ hybridization on tissue microarrays confirmed TPD52 amplification in prostate cancer epithelia. Furthermore, our studies suggest that TPD52 protein levels may be regulated by androgens, consistent with the presence of androgen response elements in the upstream promoter of TPD52. In summary, these findings suggest that dysregulation of TPD52 by genomic amplification and androgen induction may play a role in prostate cancer progression.

Adult↗
PubMed2004

Mechanisms of oncogenic KIT signal transduction in primary gastrointestinal stromal tumors (GISTs).

Most gastrointestinal stromal tumors (GISTs) express constitutively activated forms of the KIT receptor tyrosine kinase protein, resulting from oncogenic mutations in the extracellular, juxtamembrane, or kinase domains. KIT oncoproteins are detected early in GIST tumorigenesis, and most GIST patients respond well to treatment with the KIT kinase inhibitor imatinib mesylate (STI571, Gleevec). However, GISTs can develop resistance to imatinib, and additional therapeutic strategies are needed. Little is known about oncogenic KIT signal transduction in GISTs, and whether the type of KIT mutation accounts for selective activation of downstream signaling intermediates. We therefore evaluated KIT downstream signaling profiles in 15 primary GISTs with mutations in KIT exons 9, 11, 13, and 17, and in two human GIST cell lines. All GISTs showed constitutive phosphorylation at KIT tyrosine residues Y703 and Y721. Additionally, most GISTs showed activation of MAPK p42/44, AKT, S6K, STAT1, and STAT3. STAT5 and JNK were not demonstrably activated in any GIST. Using GIST in vitro models, we showed that activation of MAPK p42/44, AKT, and S6K was KIT dependent, whereas STAT1 and STAT3 phosphorylation was only partially dependent on KIT activation. Correlation of activated signaling pathways with the type of KIT mutation revealed low levels of AKT phosphorylation in exon 9 mutant GISTs in contrast to a subset of GISTs with exon 11 mutations. However, additional factors are likely to modify the engagement of signaling pathways in GISTs as suggested by the fact that four GISTs with identical KIT exon 9 mutations had differential activation of MAPK p42/44 and STAT proteins. In summary, in this first report on KIT signal transduction in primary GISTs and GIST cell lines, we identified pathways that are constitutively activated in a KIT-dependent manner and therefore warrant further study as molecular targets in GISTs.

Apoptosis↗
PubMed2004

USP6 (Tre2) fusion oncogenes in aneurysmal bone cyst.

Aneurysmal bone cyst (ABC) is a locally aggressive osseous lesion that typically occurs during the first two decades of life. ABC was regarded historically as a nonneoplastic process, but recent cytogenetic data have shown clonal rearrangements of chromosomal bands 16q22 and 17p13, indicating a neoplastic basis in at least some ABCs. Herein we show that a recurring ABC chromosomal translocation t(16;17)(q22;p13) creates a fusion gene in which the osteoblast cadherin 11 gene (CDH11) promoter region on 16q22 is juxtaposed to the entire ubiquitin-specific protease USP6 (Tre2) coding sequence on 17p13. CDH11-USP6 fusion transcripts were demonstrated only in ABC with t(16;17) but other ABCs had CDH11 or USP6 rearrangements resulting from alternate cytogenetic mechanisms. CDH11 is expressed strongly in bone, and our findings implicate a novel oncogenic mechanism in which deregulated USP6 transcription results from juxtaposition to the highly active CDH11 promoter.

Adolescent↗
PubMed2004

Targeted therapy in breast cancer: the HER-2/neu gene and protein.

The HER-2/neu oncogene, a member of the epidermal growth factor receptor or erb gene family, encodes a transmembrane tyrosine kinase receptor that has been linked to prognosis and response to therapy with the anti-HER-2-humanized monoclonal antibody, trastuzumab (Herceptin, Genentech, South San Francisco, CA) in patients with advanced metastatic breast cancer. HER-2/neu status has also been tested for its ability to predict the response of breast cancer to other therapies including hormonal therapies, topoisomerase inhibitors, and anthracyclines. This review includes an analysis of 80 published studies encompassing more than 25,000 patients designed to consider the relative advantages and disadvantages of the various methods of measuring HER-2/neu in clinical breast cancer specimens. Southern blotting, PCR amplification detection, and fluorescence in situ hybridization assays designed to detect HER-2/neu gene amplification are compared with HER-2/neu protein overexpression assays performed by immunohistochemical techniques applied to frozen and paraffin-embedded tissues and enzyme immunoassays performed on tumor cytosols. The significance of HER-2/neu overexpression in ductal carcinoma in situ and the HER-2/neu status in uncommon female breast conditions and male breast cancer are also considered. The role of HER-2/neu testing for the prediction of response to trastuzumab therapy in breast cancer is reviewed along with the current studies designed to test whether HER-2/neu status can predict the response to standard and newer hormonal therapies, cytotoxic chemotherapy, and radiation. The review will also evaluate the status of serum-based testing for circulating HER-2/neu receptor protein and its ability to predict disease outcome and therapy response.

Antineoplastic Agents↗
PubMed2004

The chimeric FUS/CREB3l2 gene is specific for low-grade fibromyxoid sarcoma.

Low-grade fibromyxoid sarcoma (LGFMS) is a variant of fibrosarcoma that was recognized as a distinct tumor entity only quite recently. We previously described a translocation, t(7;16)(q33;p11), that resulted in a fusion of the FUS and CREB3L2 (also known as BBF2H7) genes in two soft tissue tumors that fulfilled morphologic criteria for LGFMS. To delineate the spectrum of tumors that may harbor the FUS/CREB3L2 gene, we selected 45 low-grade spindle cell sarcomas for reverse transcriptase polymerase chain reaction (RT-PCR) and/or fluorescence in situ hybridization (FISH) analyses; none of these tumors had originally been diagnosed as LGFMS. Furthermore, also included were two benign soft tissue tumors and nine high-grade sarcomas with supernumerary ring chromosomes or 7q3 rearrangement and three tumors diagnosed as LGFMS prior to the genetic analysis. Of the 59 tumors analyzed, 12 were FUS/CREB3L2-positive, all of which were diagnosed at histopathologic re-examination as being LGFMS, of both the classical subtype and the subtype with giant collagen rosettes. The breakpoints in the fusion transcripts were always in exons 6 or 7 of FUS and exon 5 of CREB3L2. The results indicated that FUS/CREB3L2 is specifically associated with LGFMS and that RT-PCR or FISH analysis may be useful for the differential diagnosis.

Adolescent↗
PubMed2004

KIT mutations are common in testicular seminomas.

Expression of KIT tyrosine kinase is critical for normal germ cell development and is observed in the majority of seminomas. Activating mutations in KIT are common in gastrointestinal stromal tumors and mastocytosis. In this study we examined the frequency and spectrum of KIT mutations in 54 testicular seminomas, 1 ovarian dysgerminoma and 37 non-seminomatous germ cell tumors (NSGCT). Fourteen seminomas (25.9%) contained exon 17 point mutations including D816V (6 cases), D816H (3 cases), Y823D (2 cases), and single examples of Y823C, N822K, and T801I. No KIT mutations were found in the ovarian dysgerminoma or the NSGCTs. In transient transfection assays, mutant isoforms D816V, D816H, Y823D, and N822K were constitutively phosphorylated in the absence of the natural ligand for KIT, stem cell factor (SCF). In contrast, activation of T801I and wild-type KIT required SCF. Mutants N822K and Y823D were inhibited by imatinib mesylate (Gleevec, previously STI571) whereas D816V and D816H were both resistant to imatinib mesylate. Biochemical evidence of KIT activation, as assessed by KIT phosphorylation and KIT association with phosphatidylinositol (PI) 3-kinase in tumor cell lysates, was largely confined to seminomas with a genomic KIT mutation. These findings suggest that activating KIT mutations may contribute to tumorigenesis in a subset of seminomas, but are not involved in NSGCT.

Animals↗
PubMed2004

USP6 and CDH11 oncogenes identify the neoplastic cell in primary aneurysmal bone cysts and are absent in so-called secondary aneurysmal bone cysts.

Aneurysmal bone cyst (ABC) is a locally recurrent bone lesion that has been regarded as a reactive process. Recently, a neoplastic basis in primary ABC was evidenced by demonstration of clonal chromosome band 17p13 translocations that place the USP6 (TRE2 or TRE17) oncogene under the regulatory influence of the highly active CDH11 promoter. Herein, we report CDH11 and/or USP6 rearrangements in 36 of 52 primary ABCs (69%), of which 10 had CDH11-USP6 fusion, 23 had variant USP6 rearrangements without CDH11 rearrangement, and three had variant CDH11 rearrangements without USP6 rearrangement. USP6 and CDH11 rearrangements were restricted to spindle cells in the ABC and were not found in multinucleated giant cells, inflammatory cells, endothelial cells, or osteoblasts. CDH11 and USP6 rearrangements did not correlate with recurrence-free survival, or with other clinicopathological features. CDH11 and USP6 rearrangements were not found in any of 17 secondary ABC associated with giant cell tumor, chondroblastoma, osteoblastoma, and fibrous dysplasia. These findings demonstrate that primary ABC are mesenchymal neoplasms exhibiting USP6 and/or CDH11 oncogenic rearrangements. By contrast, secondary ABC lack CDH11 and USP6 rearrangements, and although morphological mimics of primary ABC, appear to represent a non-specific morphological pattern of a diverse group of non-ABC neoplasms.

Adolescent↗
PubMed2004

Activation of the GLI oncogene through fusion with the beta-actin gene (ACTB) in a group of distinctive pericytic neoplasms: pericytoma with t(7;12).

Activation of the GLI oncogene is an important step in the sonic hedgehog signaling pathway, and leads to, eg, tissue-specific cell proliferation during embryogenesis. GLI activity in adult tissues is restricted, but has been identified in various neoplasms, as a result of mutations in the PTCH (patched) or SMOH (smoothened) genes, encoding components of the sonic hedgehog pathway, or by amplification of GLI. Herein, we present a new mechanism of GLI activation through fusion with the beta-actin gene (ACTB) in five histologically distinctive soft tissue tumors showing a t(7;12)(p21-22;q13-15) and a pericytic phenotype. Each was composed of a perivascular proliferation of monomorphic short spindle cells that stained positively for smooth muscle actin and laminin and that showed pericytic features by electron microscopy. To date, with a median follow-up of 24 months, none has behaved in an aggressive manner. Molecular genetic analysis showed that the translocation in all cases resulted in a fusion transcript including the 5'-part of ACTB and the 3'-part of GLI. The DNA-binding zinc finger domains of GLI were retained in the fusion transcripts and it is likely that the replacement of the promoter region of GLI with that of the ubiquitously expressed ACTB gene leads to deregulation of GLI expression and its downstream target genes.

Actins↗
PubMed2004

KIT gene deletions at the intron 10-exon 11 boundary in GI stromal tumors.

Most gastrointestinal stromal tumors (GISTs) harbor oncogenic mutations in the KIT gene, and the majority of these mutations affect the juxtamembrane domain of the kinase encoded by exon 11. Screening GISTs for KIT gene mutations is important for translational research studies and for providing prognostic information on the likelihood of tumor response to treatment with the kinase inhibitor imatinib mesylate (Gleevec). In a series of GISTs analyzed in our laboratory by a combination of denaturing HPLC and direct DNA sequencing, we identified 19 cases with KIT exon 11 deletions that included from 1 to 14 bp of intron 10 sequence and resulted in loss of the normal splice acceptor site at the beginning of exon 11. Predicted use of the next potential splice-acceptor site was confirmed by cDNA sequencing in 4 cases. Thus, the resulting mutant isoform, deletion KPMYEVQWK 550-558, was the same in all 19 cases. Only two other examples of deletions across the intron 10-exon 11 boundary have been reported, yet among 722 GISTs analyzed in our laboratories these deletions were not uncommon, accounting for 3.9% of exon 11 mutations and 2.6% of all tumors. Loss of KIT intron 10 sequences may be under-recognized if the forward primer is too close to exon 11, or if cases are examined exclusively at the cDNA level. Laboratories that offer clinical screening for KIT mutations in GI stromal tumors should be aware of this class of mutations.

Amino Acid Sequence↗
PubMed2004

Role of KIT and platelet-derived growth factor receptors as oncoproteins.

KIT and platelet-derived growth factor receptors (PDGFRs) play critical oncogenic roles in a broad spectrum of hematologic and solid tumors. These receptor tyrosine kinases, as well as ABL and BCR-ABL, are inhibited by imatinib. Tumors caused by chromosomal translocations that lead to overexpression of PDGFR ligand, resulting in continuous activation of wild-type PDGFRs, are likely to respond to imatinib, as are malignancies caused by gene amplification and overexpression of wild-type PDGFR or KIT receptors. Malignancies linked to chromosomal translocations that express PDGFR or KIT fusion protein-tyrosine kinases are also likely to respond to imatinib. Malignant cell responses to imatinib depend on whether any of these tyrosine kinase activities play essential roles in the oncogenesis of a given tumor, as well as the precise molecular mechanism underlying oncogenesis. For example, imatinib efficacy for malignancies arising from constitutively activating point mutations in tyrosine kinases depends on the exact location of the mutation in the kinase molecule.

Antineoplastic Agents↗
PubMed2004

Biology of gastrointestinal stromal tumors: KIT mutations and beyond.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the digestive tract. Aspects of the morphology and immunophenotype in GISTs resemble those in the interstitial cells of Cajal (ICC), which are a specialized cell type responsible for coordinating peristaltic activity throughout the gastrointestinal tract. Therefore, it is possible that GISTs result from transformation of nonneoplastic progenitor cells that would normally differentiate towards an ICC endpoint. Activation of the KIT receptor tyrosine kinase is required for differentiation and proliferation of nonneoplastic ICC, and oncogenic KIT mutations are a crucial event in the development of most GISTs. These mutations can involve either the extracellular or intracellular domains of the KIT receptor, giving rise to conformational changes that enable constitutive, ligand-independent, activation of the KIT protein. Oncogenic KIT activation leads to phosphorylation of various substrate proteins and, in turn, to activation of signal transduction cascades regulating cell proliferation, apoptosis, chemotaxis, and adhesion. Recently, a small molecule tyrosine kinase inhibitor (STI571, imatinib mesylate, Gleevec) directed against the enzymatic (kinase) domain of the KIT protein was found to produce dramatic clinical responses as monotherapy for metastatic GISTs. This review focuses on the biological and molecular genetic principles of GISTs, and particularly the role of mutant KIT as a therapeutic target.

Benzamides↗
PubMed2004

KIT-negative gastrointestinal stromal tumors: proof of concept and therapeutic implications.

The diagnosis of gastrointestinal stromal tumor (GIST) is currently based on morphologic features and immunohistochemical demonstration of KIT (CD117). However, some tumors (in our estimation approximately 4%) have clinicopathologic features of GIST but do not express KIT. To determine if these lesions are truly GISTs, we evaluated 25 tumors with clinical and histologic features typical of GIST, but with negative KIT immunohistochemistry, for KIT and PDGFRA mutations using DNA extracted from paraffin-embedded tissue. Most tumors originated in the stomach (N = 14) or omentum/mesentery (N = 5). The neoplasms were composed of epithelioid cells (13 cases), admixed epithelioid and spindle cells (8 cases), or spindle cells (4 cases). Absence of KIT expression was confirmed by immunoblotting in 5 cases. Tumor karyotypes performed in 4 cases were noncomplex with monosomy 14 or 14q deletion, typical of GIST. Mutational analysis revealed PDGFRA and KIT mutations in 18 and 4 tumors, respectively, whereas 3 tumors did not have apparent KIT or PDGFRA mutations. The PDGFRA mutations primarily involved exon 18 (N = 15) and included 11 tumors with missense mutation in codon 842 (PDGFRA D842V or D842Y). In conclusion, a small subset of GISTs with otherwise typical clinicopathologic and cytogenetic features do not express detectable KIT protein. When compared with KIT-positive GISTs, these KIT-negative GISTs are more likely to have epithelioid cell morphology, contain PDGFRA oncogenic mutations, and arise in the omentum/peritoneal surface. Notably, some KIT-negative GISTs contain imatinib-sensitive KIT or PDGFRA mutations; therefore, patients with KIT-negative GISTs should not, a priori, be denied imatinib therapy.

Adult↗
PubMed2004

Gastrointestinal stromal tumours: etiology, pathology and clinical management.

Investigation of the regulation of cell growth, differentiation and death by signalling pathways has led to a greater understanding of how alterations in these pathways play a critical role in the development of some cancers, and has opened new opportunities for their treatment. In the present review, results with the prototype drug of this class, imatinib (Gleevec, Glivec [formerly STI571]; Novartis, Switzerland), in metastatic gastrointestinal stromal tumours are presented. The present review originated from a conference of the authors held in Montreal, Quebec in June 2003, under the sponsorship of Novartis.

Antineoplastic Agents↗
PubMed2004

Cavernous sinus and leptomeningeal metastases arising from a squamous cell carcinoma of the face: case report.

OBJECTIVE AND IMPORTANCE: Invasion of trigeminal and facial perineural spaces is a recognized complication of cutaneous malignancies. Centripetal spread along the trigeminal nerve axis and into the cavernous sinus and the gasserian ganglion is rare. Metastasis to the leptomeninges and cauda equina has not been reported. We report a unique case of perineural spread and central dissemination from an epithelial squamous cell carcinoma (SCC) associated with a tumor biomarker. CLINICAL PRESENTATION: After excision of multiple cutaneous SCCs and basal cell carcinomas of the head and neck, a 70-year-old male patient developed successive, right-side, V1 and V2 trigeminal neuropathies and complete right cavernous sinus syndrome during a 5-year period. Concurrently, the right face became paralyzed. Left facial paresis developed during the latter half of this period. Two months before admission, subacute left lower-extremity radicular weakness resulted in falls. Serial magnetic resonance imaging scans obtained in the previous 4 years were unrevealing. At the time of admission, enhancing masses were found in the 1) right cavernous sinus and dura, foramina ovale and rotundum, and Meckel's cave, 2) right subtemporal region and orbital rectus muscles, and 3) cauda equina. Cerebrospinal fluid analysis demonstrated mild pleocytosis and rare carcinoma cells. INTERVENTION: Biopsy of the right cavernous sinus mass confirmed moderately differentiated, metastatic SCC. Immunohistochemical staining and fluorescence in situ hybridization revealed epidermal growth factor receptor overexpression and genomic amplification. CONCLUSION: The indolent progression of cranial nerve palsy among patients with resected cutaneous SCCs of the head and neck must raise clinical suspicion of perineural spread, even in the absence of radiological changes. Biomarkers predicting aggressive SCC behavior, illustrated here by epidermal growth factor receptor amplification and central invasion, have the potential to guide early therapy.

Aged↗
PubMed2003

Kinase mutations and imatinib response in patients with metastatic gastrointestinal stromal tumor.

PURPOSE: Most gastrointestinal stromal tumors (GISTs) express constitutively activated mutant isoforms of KIT or kinase platelet-derived growth factor receptor alpha (PDGFRA) that are potential therapeutic targets for imatinib mesylate. The relationship between mutations in these kinases and clinical response to imatinib was examined in a group of patients with advanced GIST. PATIENTS AND METHODS: GISTs from 127 patients enrolled onto a phase II clinical study of imatinib were examined for mutations of KIT or PDGFRA. Mutation types were correlated with clinical outcome. RESULTS: Activating mutations of KIT or PDGFRA were found in 112 (88.2%) and six (4.7%) GISTs, respectively. Most KIT mutations involved exon 9 (n = 23) or exon 11 (n = 85). All KIT mutant isoforms, but only a subset of PDGFRA mutant isoforms, were sensitive to imatinib, in vitro. In patients with GISTs harboring exon 11 KIT mutations, the partial response rate (PR) was 83.5%, whereas patients with tumors containing an exon 9 KIT mutation or no detectable mutation of KIT or PDGFRA had PR rates of 47.8% (P =.0006) and 0.0% (P <.0001), respectively. Patients whose tumors contained exon 11 KIT mutations had a longer event-free and overall survival than those whose tumors expressed either exon 9 KIT mutations or had no detectable kinase mutation. CONCLUSION: Activating mutations of KIT or PDGFRA are found in the vast majority of GISTs, and the mutational status of these oncoproteins is predictive of clinical response to imatinib. PDGFRA mutations can explain response and sensitivity to imatinib in some GISTs lacking KIT mutations.

Animals↗
PubMed2003

Cloning of an Alpha-TFEB fusion in renal tumors harboring the t(6;11)(p21;q13) chromosome translocation.

MITF, TFE3, TFEB, and TFEC comprise a transcription factor family (MiT) that regulates key developmental pathways in several cell lineages. Like MYC, MiT members are basic helix-loop-helix-leucine zipper transcription factors. MiT members share virtually perfect homology in their DNA binding domains and bind a common DNA motif. Translocations of TFE3 occur in specific subsets of human renal cell carcinomas and in alveolar soft part sarcomas. Although multiple translocation partners are fused to TFE3, each translocation product retains TFE3's basic helix-loop-helix leucine zipper. We have identified the genes fused by the chromosomal translocation t(6;11)(p21.1;q13), characteristic of another subset of renal neoplasms. In two primary tumors we found that Alpha, an intronless gene, rearranges with the first intron of TFEB, just upstream of TFEB's initiation ATG, preserving the entire TFEB coding sequence. Fluorescence in situ hybridization confirmed the involvement of both TFEB and Alpha in this translocation. Although the Alpha promoter drives expression of this fusion gene, the Alpha gene does not contribute to the ORF. Whereas TFE3 is typically fused to partner proteins in subsets of renal tumors, we found that wild-type, unfused TFE3 stimulates clonogenic growth in a cell-based assay, suggesting that dysregulated expression, rather than altered function of TFEB or TFE3 fusions, may confer neoplastic properties, a mechanism reminiscent of MYC activation by promoter substitution in Burkitt's lymphoma. Alpha-TFEB is thus identified as a fusion gene in a subset of pediatric renal neoplasms.

Base Sequence↗
PubMed2003

BRD4-NUT fusion oncogene: a novel mechanism in aggressive carcinoma.

The poorly differentiated carcinoma with t(15;19)(q13, p13.1) is characterized by its highly aggressive, invariably lethal clinical course. The chromosome 19 translocation breakpoint targets the BRD4 double bromodomain-containing gene, which functions in regulation of cell cycle progression. Herein we demonstrate that BRD4 is fused with nearly the entire transcript of the novel 15q13 gene, NUT (nuclear protein in testis), forming a 6.4-kb fusion oncogene, BRD4-NUT. NUT, like BRD4, is predicted to encode a nuclear protein but, unlike the ubiquitous BRD4 transcript, is expressed only in testis. These findings establish a model to elucidate the oncogenic consequences of unscheduled NUT expression and altered BRD4 function. Very few fusion oncogenes have been identified in epithelial tumors, and BRD4-NUT is the first fusion oncogene mechanism identified in a highly lethal form of carcinoma.

Amino Acid Sequence↗