A novel fusion gene, SYT-SSX4, in synovial sarcoma.
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Amino Acid Sequence↗
Biomedical subjects
O Larsson
Publications and source records attributed to O Larsson.
Glucose decreases Na+,K+-ATPase activity in pancreatic beta-cells. An effect mediated via Ca2+-independent phospholipase A2 and protein kinase C-dependent phosphorylation of the alpha-subunit.
In the pancreatic beta-cell, glucose-induced membrane depolarization promotes opening of voltage-gated L-type Ca2+ channels, an increase in cytoplasmic free Ca2+ concentration ([Ca2+]i), and exocytosis of insulin. Inhibition of Na+,K+-ATPase activity by ouabain leads to beta-cell membrane depolarization and Ca2+ influx. Because glucose-induced beta-cell membrane depolarization cannot be attributed solely to closure of ATP-regulated K+ channels, we investigated whether glucose regulates other transport proteins, such as the Na+,K+-ATPase. Glucose inhibited Na+,K+-ATPase activity in single pancreatic islets and intact beta-cells. This effect was reversible and required glucose metabolism. The inhibitory action of glucose was blocked by pretreatment of the islets with a selective inhibitor of a Ca2+-independent phospholipase A2. Arachidonic acid, the hydrolytic product of this phospholipase A2, also inhibited Na+, K+-ATPase activity. This effect, like that of glucose, was blocked by nordihydroguaiaretic acid, a selective inhibitor of the lipooxygenase metabolic pathway, but not by inhibitors of the cyclooxygenase or cytochrome P450-monooxygenase pathways. The lipooxygenase product 12(S)-HETE (12-S-hydroxyeicosatetranoic acid) inhibited Na+,K+-ATPase activity, and this effect, as well as that of glucose, was blocked by bisindolylmaleimide, a specific protein kinase C inhibitor. Moreover, glucose increased the state of alpha-subunit phosphorylation by a protein kinase C-dependent process. These results demonstrate that glucose inhibits Na+, K+-ATPase activity in beta-cells by activating a distinct intracellular signaling network. Inhibition of Na+,K+-ATPase activity may thus be part of the mechanisms whereby glucose promotes membrane depolarization, an increase in [Ca2+]i, and thereby insulin secretion in the pancreatic beta-cell.
12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
Regulatory role of mevalonate and N-linked glycosylation in proliferation and expression of the EWS/FLI-1 fusion protein in Ewing's sarcoma cells.
The Ewing's sarcoma cell line RD-ES, which carries the EWS/FLI-1 fusion gene, responded to the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor lovastatin with growth arrest. Replenishment of mevalonate (MVA) to the arrested cells restored cell growth. However, if tunicamycin (TM), which is an inhibitor of N-linked glycosylation, was present together with MVA the cells remained arrested, indicating that N-linked glycosylation is of importance for growth of Ewing's sarcoma cells. Inhibition of the biosynthesis of EWS/FLI-1 fusion protein by treatment with antisense oligonucleotides also led to growth arrest, suggesting that this protein is of importance for cell growth. We investigated whether MVA synthesis and N-linked glycosylation could be involved in regulation of the expression of the EWS/FLI-1 fusion protein, which in fact contains four potential sites for N-linked glycosylation. We found that inhibition of both HMG-CoA reductase and N-linked glycosylation drastically decreased the expression of the fusion protein, which mainly appears in the cell nuclei. There was no significant difference in the inhibitory effect on the fusion protein between the cytoplasm and the cell nuclei, indicating that the transport of the fusion protein to the cell nucleus is not affected. The fusion protein did not exhibit any gel electrophoretic mobility shift after treatment of the cells with lovastatin or TM, and it did not incorporate [3H]glucosamine. Therefore we can conclude that the fusion protein is not a glycoprotein. The decreased expression of the fusion protein following lovastatin or TM treatment was found to be due to a lowered stability of de novo-synthesized fusion protein. The down-regulation of the fusion protein was correlated to growth arrest. Furthermore, the kinetics between the expression of EWS/FLI-1 fusion protein and the initiation of DNA synthesis in MVA-stimulated cells were similar. Taken together, our data suggest that the regulatory role of N-linked glycosylation in the expression of the EWS/FLI-1 fusion protein is important for growth of Ewing's sarcoma cells. Possible mechanisms underlying TM-induced decrease in EWS/FLI-1 expression may involve the breaking of growth factor receptor pathways.
Amino Acid Sequence↗
Clinical importance of genomic imbalances in synovial sarcoma evaluated by comparative genomic hybridization.
The t(X;18)(p11.2;q11.2) (SYT/SSX1 or SSX2) is represented in more than 95% of synovial sarcoma. Even if recent data has implicated that the type of fusion gene (SYT/SSX1 or SYT/SSX2) can be of prognostic importance, the cellular and molecular mechanisms underlying the clinical behavior of synovial sarcoma are still poorly understood. To approach this issue, we investigated whether secondary genetic aberrations may influence the clinical outcome of synovial sarcoma. Clinical outcome with reference to comparative genomic hybridization (CGH) findings (losses or gains of genetic material) were analyzed for a uniquely large modern material of 69 synovial sarcomas. Thirty-five of 69 specimens showed DNA sequence copy number changes. The frequency of aberrations/tumor were higher (mean 4.7) for monophasic tumors than for biphasic tumors (mean 2.1). Gains of the whole or parts, including the long arm, of chromosome 8 were significantly overrepresented in large tumors (> 5 cm), suggesting that tumors with this genetic abnormality have an increased growth rate. No difference regarding metastasis-free or overall survival was seen between patients with or without tumors containing secondary copy number changes. No specific copy number change was linked to a significantly improved or impaired metastasis-free survival.
Adolescent↗
Ki-67 is strongly prognostic in synovial sarcoma: analysis based on 86 patients from the Scandinavian Sarcoma group register.
In a study based on formalin-fixed paraffin-embedded material from 86 patients with primary synovial sarcoma located in the extremities or on the trunk wall, the prognostic importance of MIB-1 index, p53-expession and tumour size was analysed. Multivariate analysis identified two metastatic risk factors: increasing tumour size and MIB-1 > 9%. The 5-year metastasis-free survival-rate for patients with tumour size < or = 5 cm + MIB-1 < 10% was 0.83 (95% confidence interval (CI) 0.64-0.92) compared to 0.31 (95% CI 0.11-0.53) in cases with tumour size > 5 cm + MIB-1 > or = 10%. Our study shows that metastatic disease in synovial sarcoma is closely related to MIB-1 index. Using our model based on tumour size and MIB-1 index, cases with good and poor prognosis can easily be discriminated. Therefore our model can be used to identify patients who should be considered for adjuvant chemotherapy.
Antigens, Nuclear↗
Metastatic patterns, clinical outcome, and malignant phenotype in malignant cutaneous melanoma.
The objective of this population-based study was to assess metastatic pathways and outcomes vs. selected clinical and histopathologic features of the primary tumor in patients with recurrent cutaneous malignant melanoma. At a median follow-up time of 11 years, 569/2493 patients with recurrence were identified. We demonstrated a 5-year survival rate of 82% and 30% among those with a primary local or regional recurrence, respectively. Patients with primary distant skin, distant lymph node, or pulmonary metastases had a significantly better survival compared with those with CNS, bone, visceral, liver, or multiple sites of first distant metastases. The metastatic pathways were similar with regard to histogenetic type, primary tumor thickness, Clark's level of invasion, and primary tumor ulceration. Different histogenetic types, as assessed by light microscopy, imply different risks of recurrence. However, once the recurrence is manifest, the metastatic pathways are uniform, as well as prognosis, and survival.
Adult↗
Epidemiological characteristics of cutaneous malignant melanoma of the head and neck--a population-based study.
Since cutaneous malignant melanoma (CMM) and melanoma in situ (MIS) of the head and neck have only partially been differentiated from CMM of other anatomic sites, these lesions are classified in detail in this study. Data from 756 patients derived from the population-based register of the Stockholm-Gotland area were analyzed and the findings showed that the incidence of CMM was 3.4 times higher in the face compared to the skin outside the head-neck area and that lentigo maligna melanoma was 74 times and nodular melanoma 2.3 times more common in the face. Mean age at diagnosis was significantly higher for patients with CMM of the head and neck irrespective of histogenetic type. Tumor site within the head and neck related to age at diagnosis. CMM of the head and neck differs from CMM of other locations. Epidemiological data are in agreement with the hypothesis that UV radiation (chronic or intermittent) may give rise to melanomas with various phenotypic traits.
Adolescent↗
Interferon-induced remission in aggressive fibromatosis of the lower extremity.
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Adult↗
Morphologic review of 1000 soft tissue sarcomas from the Scandinavian Sarcoma Group (SSG) Register. The peer-review committee experience.
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Humans↗
Diagnosis, treatment and prognosis of patients with synovial sarcoma. The Scandinavian Sarcoma Group experience.
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Amputation, Surgical↗
Expression of the insulin-like growth factor 1 receptor (IGF-1R) in breast cancer cells: evidence for a regulatory role of dolichyl phosphate in the transition from an intracellular to an extracellular IGF-1 pathway.
In this study we provide evidence that the low expression of IGF-1R at the cell surface of estrogen-independent breast cancer cells is due to a low rate of de novo synthesis of dolichyl phosphate. The analyses were performed on the estrogen receptor-negative breast cancer cell line MDA231 and, in comparison, the melanoma cell line SK-MEL-2, which expresses a high number of plasma membrane-bound IGF-1R. Whereas the MDA231 cells had little or no surface expression of IGF-1R, they expressed functional (i.e., ligand-binding) intracellular receptors. By measuring the incorporation of [3H]mevalonate into dolichyl phosphate, we could demonstrate that the rate of dolichyl phosphate synthesis was considerably lower in MDA231 cells than in SK-MEL-2 cells. Furthermore, N-linked glycosylation of the alpha-subunit of IGF-1R was 8-fold higher in the melanoma cells. Following addition of dolichyl phosphate to MDA231 cells, N-linked glycosylation of IGF-1R was drastically increased, which in turn was correlated to a substantial translocation of IGF-1R to the plasma membrane, as assayed by IGF-1 binding analysis and by Western blotting of plasma membrane proteins. The dolichyl phosphate-stimulated receptors were proven to be biochemically active since they exhibited autophosphorylation. Under normal conditions MDA231 cells, expressing very few IGF-1R at the cell surface, were not growth-arrested by an antibody (alphaIR-3) blocking the binding of IGF-1 to IGF-1R. However, after treatment with dolichyl phosphate, leading to a high cell surface expression of IGF-1R, alphaIR-3 efficiently blocked MDA231 cell growth. Taken together with the fact that the breast cancer cells produce IGF-1 and exhibit intracellular binding, our data suggest that the level of de novo -synthesized dolichyl phosphate may be critical for whether the cells will use an intracellular or an extracellular autocrine IGF-1 pathway.
Blotting, Western↗
110 subfascial lipomatous tumors. MR and CT findings versus histopathological diagnosis and cytogenetic analysis.
PURPOSE: To evaluate whether liposarcoma, atypical lipomatous tumors and lipoma can be differentiated radiologically. MATERIAL AND METHODS: We have retrospectively analyzed CT and/or MR images of 110 subfascial lipomatous lesions. The amount of fat within the tumors was visually graded from the images as: none, 1-75%, 75-95% or 95-100%. The structure of non-fatty tumor components was compared. The images were compared to histopathology and in 37 cases to cytogenetic findings. RESULTS: Only 4 of 20 liposarcomas contained fat. All 4 lesions, histopathologically diagnosed as atypical lipomatous tumors, contained fat but less than 75% of tumor volume. All lesions with more fat than 75% of tumor volume were histologically diagnosed as lipomas. However, one-third of the karyotyped lipomas had ring chromosomes which are considered typical for atypical lipomatous tumors. CONCLUSION: When a tumor is composed more or less solely of fat, the diagnosis of a lipoma or atypical lipomatous tumor with a phenotype simulating a lipoma can be assumed. When the fat content is less than 75% of the tumor volume or non-fatty nodules are found, biopsies from different tumor components have to be performed to exclude malignancy. When no fat is found, imaging does not help in differentiating lipoma or liposarcoma from other soft tissue tumors.
Adolescent↗
Synovial sarcoma--identification of favorable and unfavorable histologic types: a Scandinavian sarcoma group study of 104 cases.
Synovial sarcoma has traditionally been regarded as a high-grade sarcoma and treated as such. Recently, specific types of poorly differentiated synovial sarcoma have been defined and shown to affect prognosis adversely. We studied 104 primary synovial sarcomas of the extremities and trunk wall without metastasis at diagnosis that were retrieved from the Scandinavian Sarcoma Group Registry (SSG) and the Swedish Cancer Registry from 1986 to 1994. Follow-up was available in all patients, median 6 (3-11) years for the survivors. There were local recurrences in 15% of patients and metastases in 33%. Histologically, the tumors were divided into favorable and unfavorable types. The favorable type had no significant cytologic atypia, and in most instances, no necrosis and a mitotic count of < 10/10 hpf. The unfavorable type included so-called poorly differentiated synovial sarcomas as well as recognizable biphasic and monophasic synovial sarcomas with prominent nuclear atypia, extreme cellularity and nuclear crowding. Designation of a tumor as having favorable vs. unfavorable histology conveyed more prognostic information than any single histologic factor. Kaplan-Meier estimates of metastasis-free survival at 5 years were 83% for patients with histologically favorable tumors and 31% for patients with histologically unfavorable tumors (95% confidence intervals 72-92% and 13-51%, respectively). These findings may influence future treatment protocols for synovial sarcoma.
Adolescent↗
Dolichol-like lipids with stimulatory effect on DNA synthesis: substrates for protein dolichylation?
Substantial evidence has suggested that a nonsterol product of mevalonic acid (MVA) is essential for the initiation of DNA synthesis in mammalian cells. Several possible isoprenoid candidates have been suggested, but the identity of this compound still remains unknown. In this study we have isolated and purified MVA products from SV40-transformed human fibroblasts and identified fractions with a growth-stimulatory effect. The cells were labelled with [14C]MVA in the presence of inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. After lipid extraction, the [14C]MVA-labelled lipids were subjected to high performance liquid chromatography and size-exclusion chromatography, and the effect of the fractionated eluate on the DNA synthesis of arrested MVA-depleted target cells was tested. Thereby we found a fraction of [14C]MVA-labelled lipids with a substantial stimulatory effect on DNA synthesis. The chromatographic behavior suggested that the growth-stimulating fractions contained dolichol-20. This was confirmed by mass spectrometric analysis. Similar results were obtained when lipids from hepatocellular carcinoma cells and a sample from breast tumor were isolated and analyzed by the same procedure. The mechanisms by which these compounds induce DNA synthesis are unknown. Recent data obtained in our laboratory have provided evidence that dolichyl groups are covalently linked to tumor cell proteins, which implicates a new biological function for long-chain polyisoprenoid alcohols (Hjertman et al. [1997] FEBS Lett 416:235-238). In this study we demonstrate that tumor cells containing dolichol-like growth-stimulatory lipids also contained dolichylated proteins. This raises the question whether the growth-stimulatory dolichol-like lipids serve as substrates for the dolichylation reaction.
Cell Division↗
Changes in cytoplasmic ATP concentration parallels changes in ATP-regulated K+-channel activity in insulin-secreting cells.
Changes in cytoplasmic ATP concentration were monitored in intact insulin-producing cells and correlated to changes in the activity of ATP-sensitive K+-channels (KATP channels). Luciferase was introduced into HIT M2.2 cells and whole pancreatic islets by transient expression of firefly (Photinus pyralis) luciferase cDNA. In transfected cells, extracellular addition of luciferin increased the luminescence signal to a maximum within 50-120 s. Addition of 1 microM of the mitochondrial uncoupler FCCP decreased the luminescence, an effect partly reversed upon withdrawal of the compound. High concentrations of glucose increased cytoplasmic free ATP concentration. Changes in the luminescence signal were accompanied by changes in activity of the ATP-sensitive K+-channel. Transfection per se did not deteriorate cell function, as verified by experiments showing similar changes in cytoplasmic free Ca2+-concentration, [Ca2+li, in both transfected and non-transfected cells. By measuring the cytoplasmic ATP concentration and KATP channel activity under similar experimental conditions, it was possible to establish, for the first time, a direct relationship between these two parameters. This indeed suggests that the cytoplasmic ATP concentration has a crucial role in the regulation of KATP channel activity under physiological conditions.
Adenosine Triphosphate↗
Long chain coenzyme A esters activate the pore-forming subunit (Kir6. 2) of the ATP-regulated potassium channel.
The ATP-dependent potassium (KATP) channel in the pancreatic beta-cell is a complex of two proteins, the pore-forming Kir6.2 and the sulfonylurea receptor type 1 (SUR1). Both subunits are required for functional KATP channels because expression of Kir6.2 alone does not result in measurable currents. However, truncation of the last 26 or 36 amino acids of the C terminus of Kir6.2 enables functional expression of the pore-forming protein in the absence of SUR1. Thus, by using the truncated form of Kir6.2, expressed in the absence and presence of SUR1, it has been shown that the site at which ATP mediates channel inhibition is likely to be situated on Kir6.2. We have now examined the effects of long chain acyl-CoA (LC-CoA) esters on the C-terminally truncated mouse Kir6.2Delta365-390 (Kir6. 2DeltaC26) in inside-out patches isolated from Xenopus laevis oocytes. LC-CoA esters, saturated (C14:0, C16:0) and unsaturated (C18:1), increased Kir6.2DeltaC26 currents, whereas short and medium chain CoA esters (C3:0, C8:0, C12:0) were unable to affect channel activity. The LC-CoA esters were also able to counteract the blocking effect of ATP on Kir6.2DeltaC26. The stimulatory effect of the esters could be explained by the induction of a prolonged open state of Kir6.2DeltaC26. In the presence of the esters, channel open time was increased approximately 3-fold, which is identical to what was obtained in the native mouse KATP channel. Coexpression of SUR1 together with Kir6.2DeltaC26 did not further increase the ability of LC-CoA esters to stimulate channel activity. We conclude that Kir6.2 is the primary target for LC-CoA esters to activate the KATP channel and that the esters are likely to induce a conformational change by a direct interference with the pore-forming subunit, leading to openings of long duration.
ATP-Binding Cassette Transporters↗
Cysteine string protein (CSP) is an insulin secretory granule-associated protein regulating beta-cell exocytosis.
Cysteine string proteins (CSPs) are novel synaptic vesicle-associated protein components characterized by an N-terminal J-domain and a central palmitoylated string of cysteine residues. The cellular localization and functional role of CSP was studied in pancreatic endocrine cells. In situ hybridization and RT-PCR analysis demonstrated CSP mRNA expression in insulin-producing cells. CSP1 mRNA was present in pancreatic islets; both CSP1 and CSP2 mRNAs were seen in insulin-secreting cell lines. Punctate CSP-like immunoreactivity (CSP-LI) was demonstrated in most islets of Langerhans cells, acinar cells and nerve fibers of the rat pancreas. Ultrastructural analysis showed CSP-LI in close association with membranes of secretory granules of cells in the endo- and exocrine pancreas. Subcellular fractionation of insulinoma cells showed CSP1 (34/36 kDa) in granular fractions; the membrane and cytosol fractions contained predominantly CSP2 (27 kDa). The fractions also contained proteins of 72 and 70 kDa, presumably CSP dimers. CSP1 overexpression in INS-1 cells or intracellular administration of CSP antibodies into mouse ob/ob beta-cells did not affect voltage-dependent Ca2+-channel activity. Amperometric measurements showed a significant decrease in insulin exocytosis in individual INS-1 cells after CSP1 overexpression. We conclude that CSP is associated with insulin secretory granules and that CSP participates in the molecular regulation of insulin exocytosis by mechanisms not involving changes in the activity of voltage-gated Ca2+-channels.
Animals↗
Direct inhibition of the pancreatic beta-cell ATP-regulated potassium channel by alpha-ketoisocaproate.
The ATP-regulated potassium (KATP) channel plays an essential role in the control of insulin release from the pancreatic beta-cell. In the present study we have used the patch-clamp technique to study the direct effects of alpha-ketoisocaproate on the KATP channel in isolated patches and intact pancreatic beta-cells. In excised inside-out patches, the activity of the KATP channel was dose-dependently inhibited by alpha-ketoisocaproate, half-maximal concentration being approximately 8 mM. The blocking effect of alpha-ketoisocaproate was fully reversible. Stimulation of channel activity by the addition of ATP/ADP (ratio 1) did not counteract the inhibitory effect of alpha-ketoisocaproate. In the presence of the metabolic inhibitor sodium azide, alpha-ketoisocaproate was still able to inhibit single channel activity in excised patches and to block whole cell KATP currents in intact cells. No effect of alpha-ketoisocaproate could be obtained on either the large or the small conductance Ca2+-regulated K+ channel. Enzymatic treatment of the patches with trypsin prevented the inhibitory effect of alpha-ketoisocaproate. Based on these observations, it is unlikely that the blocking effect of alpha-ketoisocaproate is due to an unspecific effect on K+ channel pores. Leucine, the precursor of alpha-ketoisocaproate, did not affect KATP channel activity in excised patches. Our findings are compatible with the view that alpha-ketoisocaproate not only affects the beta-cell stimulus secretion coupling by generation of ATP but also by direct inhibition of the KATP channel.
Adenosine Triphosphate↗