UMLS:C0035412 - FACTA Search

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Query: UMLS:C0035412 (rhabdomyosarcoma)
6,156 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mammalian target of rapamycin (mTOR) has been shown to link growth factor signaling and posttranscriptional control of translation of proteins that are frequently involved in cell cycle progression. However, the role of this pathway in cell survival has not been demonstrated. Here, we report that rapamycin, a specific inhibitor of mTOR kinase, induces G1 cell cycle arrest and apoptosis in two rhabdomyosarcoma cell lines (Rh1 and Rh30) under conditions of autocrine cell growth. To examine the kinetics of rapamycin action, we next determined the rapamycin sensitivity of rhabdomyosarcoma cells exposed briefly (1 h) or continuously (6 days). Results demonstrate that Rh1 and Rh30 cells were equally sensitive to rapamycin-induced growth arrest and apoptosis under either condition. Apoptosis was detected between 24 and 144 h of exposure to rapamycin. Both cell lines have mutant p53; hence, rapamycin-induced apoptosis appears to be a p53-independent process. To determine whether induction of apoptosis by rapamycin was specifically due to inhibition of mTOR signaling, we engineered Rh1 and Rh30 clones to stably express a mutant form of mTOR that was resistant to rapamycin (Ser2035-->Ile; designated mTOR-rr). Rh1 and Rh30 mTOR-rr clones were highly resistant (>3000-fold) to both growth inhibition and apoptosis induced by rapamycin. These results are the first to indicate that rapamycin-induced apoptosis is mediated by inhibition of mTOR. Exogenous insulin-like growth factor (IGF)-I protected both Rh1 and Rh30 from apoptosis, without reactivating ribosomal p70 S6 kinase (p70S6K) downstream of mTOR. However, in rapamycin-treated cultures, the response to IGF-I differed between the cell lines: Rh1 cells proliferated normally, whereas Rh30 cells remained arrested in G1 phase but viable. Rapamycin is known to inhibit synthesis of specific proteins but did not inhibit synthesis or alter the levels of mTOR. To examine the rate at which the mTOR pathway recovered, the ability of IGF-I to stimulate p70S6K activity was followed in cells treated for 1 h with rapamycin and then allowed to recover in medium containing > or =100-fold excess of FK506 (to prevent rapamycin from rebinding to its cytosolic receptor FKBP-12). Our results indicate that, in Rh1 cells, rapamycin dissociates relatively slowly from FKBP-12, with a t1/2 of approximately 17.5 h. in the presence of FK506, whereas there was no recovery of p70S6K activity in the absence of this competitor. This was of interest because rapamycin was relatively unstable under conditions of cell culture having a biological t1/2 of approximately 9.9 h. These results help to explain why cells are sensitive following short exposures to rapamycin and may be useful in guiding the use of rapamycin analogues that are entering clinical trials as novel antitumor agents.
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PMID:Rapamycin causes poorly reversible inhibition of mTOR and induces p53-independent apoptosis in human rhabdomyosarcoma cells. 1002 80

The FKHR gene was first identified from its disruption by the t(2;13) chromosomal translocation seen in the pediatric tumor alveolar rhabdomyosarcoma. It encodes for a member of the forkhead family of transcription factors. Recently, a homolog of FKHR in the nematode Caenorhabditis elegans was identified called DAF-16, which is a downstream target of two Akt homologs in an insulin-related signaling pathway. We have examined the possible role of Akt in the regulation of FKHR. We find that FKHR can bind in vitro to the insulin-responsive sequence (IRS) in the insulin-like growth factor-binding protein 1 promoter and can activate transcription from a reporter plasmid containing multiple copies of the IRS. Expression of active but not inactive Akt can suppress FKHR-mediated transcriptional activation. Akt can phosphorylate FKHR in vitro on three phosphoacceptor sites, at least a subset of which can also be phosphorylated by Akt in vivo. Importantly, mutation of these three sites to alanine residues enhances the transcriptional activity of FKHR and renders it resistant to inhibition by Akt. Expression of an Akt-resistant mutant of FKHR causes apoptosis in 293T cells in a manner dependent on DNA binding. These results suggest that FKHR may be a direct nuclear regulatory target for Akt in both metabolic and cell survival pathways.
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PMID:Negative regulation of the forkhead transcription factor FKHR by Akt. 1035 14

The forkhead rhabdomyosarcoma transcription factor (FKHR) is a promising candidate to be the transcription factor that binds to the insulin response element of the insulin-like growth factor-binding protein-1 (IGFBP-1) promoter and mediates insulin inhibition of IGFBP-1 promoter activity. Cotransfection of mouse FKHR increased IGFBP-1 promoter activity 2-3-fold in H4IIE rat hepatoma cells; insulin inhibited FKHR-stimulated promoter activity approximately 70%. A C-terminal fragment of mouse FKHR (residues 208-652) that contains the transcription activation domain fused to a Gal4 DNA binding domain potently stimulated Gal4 promoter activity. Insulin inhibited FKHR fragment-stimulated promoter activity by approximately 70%. Inhibition was abolished by coincubation with the phosphatidylinositol-3 kinase inhibitor, LY294002. The FKHR 208-652 fragment contains two consensus sites for phosphorylation by protein kinase B (PKB)/Akt, Ser-253 and Ser-316. Neither site is required for insulin inhibition of promoter activity stimulated by the FKHR fragment, and overexpression of Akt does not inhibit FKHR fragment-stimulated Gal4 promoter activity. These results suggest that insulin- and phosphatidylinositol-3 kinase-dependent phosphorylation of another site in the fragment by a kinase different from PKB/Akt inhibits transcription activation by the fragment. Phosphorylation of this site also may be involved in insulin inhibition of transcription activation by full-length FKHR, but only after phosphorylation of Ser-253 by PKB/Akt.
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PMID:Insulin inhibits the activation of transcription by a C-terminal fragment of the forkhead transcription factor FKHR. A mechanism for insulin inhibition of insulin-like growth factor-binding protein-1 transcription. 1070 99

The transcription factor, forkhead in rhabdomyosarcoma (FKHR), is phosphorylated at three amino acid residues (Thr-24, Ser-256 and Ser-319) by protein kinase B (PKB)alpha. In the present study, mutagenesis has been used to study the roles of these phosphorylation events in regulating FKHR function in transfected HEK-293 cells. We find that the overexpression of FKHR[S256A] (where Ser-256-->Ala) blocks PKB activity in cells, preventing phosphorylation of the endogenous substrates FKHRL1 and glycogen synthase kinase-3. Thus some reported effects of overexpression of this and other mutants may be indirect, and result from suppression of the phosphorylation of other sites on FKHR and/or other PKB substrates. For example, we have shown that Thr-24 phosphorylation alone is critical for interaction with 14-3-3 proteins, and that the substitution of Ser-256 with an alanine residue indirectly blocks 14-3-3 protein binding by preventing the phosphorylation of Thr-24. We also found that insulin-like growth factor (IGF)-1 and serum-induced nuclear exclusion of FKHR[S256A] depends on the degree of overexpression of this mutant. Our results indicated that the interaction of FKHR with 14-3-3 proteins was not required for IGF-1-stimulated exclusion of FKHR from the nucleus. We present evidence in support of another mechanism, which depends on the phosphorylation of Ser-256 and may involve the masking of a nuclear localization signal. Finally, we have demonstrated that the failure of IGF-1 to suppress transactivation by FKHR[S256A] is not explained entirely by its failure to bind 14-3-3 proteins or to undergo nuclear exclusion. This result suggests that Ser-256 phosphorylation may also suppress transactivation by FKHR by yet another mechanism, perhaps by disrupting the interaction of FKHR with target DNA binding sites and/or the function of the transactivation domain.
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PMID:Roles of the forkhead in rhabdomyosarcoma (FKHR) phosphorylation sites in regulating 14-3-3 binding, transactivation and nuclear targetting. 1123 65

Rhabdomyosarcoma is a soft tissue tumor committed to the myogenic lineage but arrested prior to terminal differentiation. To identify new genes implicated in the block in myogenic differentiation of rhabdomyosarcoma cells and those responsible for their proceeding along the myogenic pathway we used cDNA microarrays to compare gene expression profiles of two clones of the human embryonal rhabdomyosarcoma cell line RD with different myogenic potentials: RD/12, which is unable to differentiate, and RD/18, which shows elements able to terminally differentiate, as defined by the expression of myosin heavy chain (up to 50% of the population) and the formation of multinucleated myotube-like structures. We identified 80 genes differentially expressed by the two clones. Differentiating RD/18 cells overexpressed the myogenic transcription factor myogenin along with known myogenic markers; myogenin transfection into undifferentiated RD/12 cells was able to revert the phenotype giving rise to 94% of clones displaying a differentiated morphology. RD/18 cells also expressed several genes not known to be expressed in rhabdomyosarcoma or muscle cells, such as pigment-epithelium derived factor and endothelin-3. Poorly differentiated RD/12 cells, along with genes related to mesenchymal lineage or early myogenic commitment, also expressed genes not previously known to be related to the differentiation block of human rhabdomyosarcoma, such as monocyte chemotactic protein-1, connective tissue growth factor and insulin-like growth factor binding protein-5. Differential expression of these genes in a time course of differentiation suggested their potential roles as either new myogenic markers or repressors of differentiation. These results identify a cluster of new genes related to the aberrant myogenic differentiation program of human rhabdomyosarcoma cells.
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PMID:Identification of new genes related to the myogenic differentiation arrest of human rhabdomyosarcoma cells. 1167 6

Rhabdomyosarcoma is the most common soft-tissue sarcoma of childhood. Rhabdomyosarcoma cell lines overexpress insulin-like growth factor-II (IGF-II), an autocrine growth factor that is inhibited by insulin-like growth factor binding protein-6 (IGFBP-6). IGFBP-6 is associated with myoblast quiescence, and expression in rhabdomyosarcoma cells is low. The effect of IGFBP-6 on 2 rhabdomyosarcoma cell lines, RD and Rh30, was studied. IGFBP-6 inhibited anchorage-dependent growth of RD and Rh30 cells in a dose-dependent manner (p < 0.0001). IGFBP-6 also inhibited anchorage-independent growth of RD cells in soft agar in a dose-dependent manner (p < 0.01). Anchorage-independent growth of RD cells on polyhydroxyethylmethacrylate-coated plates was decreased to a minimum of 48% of control after treatment with IGFBP-6 (p < 0.001). In this system, IGFBP-6 increased apoptosis 4-fold (p < 0.001). IGF-II partially reversed the IGFBP-6-induced decrease in growth and increase in apoptosis. Rh30 cells were stably transfected with an IGFBP-6 cDNA and subcutaneous xenografts established in BALB/c nude mice. After 18 days, sizes of 2 independent clones of IGFBP-6-overexpressing Rh30 cells were reduced to 12% and 26% of vector control-transfected tumors (p = 0.0006 and 0.002, respectively). IGFBP-6 therefore inhibits proliferation and promotes apoptosis of rhabdomyosarcoma in vitro and dramatically inhibits xenograft growth in vivo, at least in part by inhibiting IGF-II. Low expression of IGFBP-6 may therefore contribute to rhabdomyosarcoma growth and metastasis.
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PMID:Overexpression of insulin-like growth factor binding protein-6 inhibits rhabdomyosarcoma growth in vivo. 1174 58

In this investigation, we selected PAX3/FKHR and PAX7/FKHR fusion transcript-positive and -negative alveolar rhabdomyosarcomas (ARMSs) and embryonal rhabdomyosarcomas (ERMSs) with and without anaplastic features, to ascertain genomic imbalance differences and/or similarities within these histopathologic and genetic rhabdomyosarcoma (RMS) variants. Comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH) studies were performed on 45 rhabdomyosarcoma specimens consisting of 23 ARMSs and 22 ERMSs (12 ERMS cases were included from an earlier study). The anaplastic variant of RMS has not previously been subjected to CGH analysis. Overall, the most prominent imbalances were gain of chromosomes or chromosomal regions 2/2q (40%), 7/7q (31%), 8/8p (53%), 11/11q (31%), 12q13-15 (49%), 13q14 (22%), and 20/20p (31%), and loss of 1p36 (27%), 3p14-21 (22%), 9q21-22 (33%), 10q22-qter (18%), 16q (27%), 17p (22%), and 22 (22%). These gains and losses were distributed equally between ARMS and ERMS histologic subtypes (excluding 7/7q and 11/11q gain that were observed chiefly in ERMS), demonstrating that these entities are similar with respect to recurrent genomic imbalances. Moreover, genomic imbalances were also evenly distributed among the ARMS fusion transcript subtypes, providing evidence for a genetic kinship despite the absence of a fusion transcript in some cases. Genomic amplification was detected in 26% and 23% of the ARMS and ERMS cases, respectively (with nearly all of the latter subset exhibiting anaplastic features). One amplicon, involving 15q25-26, corresponds to the locus of the insulin-like growth factor type I receptor (IGF1R) gene. Amplification of IGF1R was confirmed molecularly in the cases exhibiting a 15q25-26 amplicon. In summary, these results indicate that genomic gains and losses involve alike chromosomes with similar frequencies within the histopathologic and genetic subtypes of rhabdomyosarcoma, that genomic amplification is frequent not only in the alveolar histologic subtype of rhabdomyosarcoma but also in ERMS with anaplasia, and that amplification of IGF1R possibly plays a role in the development or progression of a subset of rhabdomyosarcomas.
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PMID:Genomic gains and losses are similar in genetic and histologic subsets of rhabdomyosarcoma, whereas amplification predominates in embryonal with anaplasia and alveolar subtypes. 1180 89

Rhabdomyosarcomas derive from the skeletal muscle lineage and harbor a variety of genetic and molecular lesions. However, it is not clear which molecular alterations have a pathogenetic role. We show that activation of the HER-2/neu oncogene coupled with inactivation of the oncosuppressor gene p53 causes rhabdomyosarcoma in mice. At the age of 11-21 weeks, all male mice carrying both genetic lesions developed embryonal rhabdomyosarcomas expressing desmin, myosin, and insulin-like growth factor-II, in the genitourinary tract. Our findings led to the hypothesis that the interaction between HER family genes and the p53 pathway might be involved in the origin of human rhabdomyosarcoma.
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PMID:Development of rhabdomyosarcoma in HER-2/neu transgenic p53 mutant mice. 1278 74

Urokinase-type plasminogen activator (uPA) binds to its receptor, uPAR, on the surface of cancer cells, leading to the formation of plasmin. Rhabdomyosarcoma (RMS) cell lines secrete high levels of insulin-like growth factor II (IGF-II), suggesting autocrine IGFs play a major role in the unregulated growth and metastasis of RMS. In vitro, IGF-II and IGF-I increased migration of RD cells to 124+/-9% (P<0.01) and 131+/-8% (P<0.05) of control, respectively. IGF-II-induced migration was abolished by insulin-like growth factor binding protein-6 (IGFBP-6) (P<0.01), a relatively specific inhibitor of IGF-II, and by plasminogen activator inhibitor type 1 (PAI-1) (P<0.05). Aprotinin, a plasmin inhibitor, and mannosamine, which inhibits the synthesis of glycosylphosphatidylinositol (GPI), thereby preventing anchorage of GPI-linked proteins such as uPAR to the cell membrane, also decreased IGF-II- (P<0.05 for both) but not IGF-I-induced migration. [Arg54,Arg55]IGF-II and [Leu27]IGF-II, which preferentially bind to the IGF-I and IGF-II/mannose-6-phosphate receptors (IGF-II/M6PR), respectively, both induced RD cell migration to 146+/-8% (P<0.01) and 120+/-7% (P<0.05) of control, respectively. An anti-uPAR anti-serum reduced IGF-II- and IGF-I-induced migration (P<0.05 for both). An anti-low density lipoprotein-related protein (LRP) anti-serum reduced IGF-I-induced migration (P<0.05). IGF-I and -II both increased specific 125I-single chain uPA (scuPA) binding to RD cells in a dose-dependent manner (P<0.01). These results suggest involvement of the PA/plasmin system in IGF-induced migration and indicate important roles these systems may have in RMS metastasis.
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PMID:Urokinase type plasminogen activator receptor is involved in insulin-like growth factor-induced migration of rhabdomyosarcoma cells in vitro. 1294 49

Rhabdomyosarcomas secrete high levels of insulin-like growth factor-II, suggesting this autocrine growth factor plays a major role in the unregulated growth of this childhood cancer. Treatment of Rh30 rhabdomyosarcoma cells with insulin-like growth factor binding protein-6 (IGFBP-6; 1000 ng/ml), which binds insulin-like growth factor-II with high affinity, inhibited growth in vitro (p < 0.001). Co-incubation of cells with rapamycin (1.56 ng/ml), an inhibitor of p70 S6 kinase, and IGFBP-6 (200 ng/ml) resulted in a significant reduction in Rh30 cell number compared to rapamycin or IGFBP-6 alone (p < 0.05 for both). Co-treatment of Rh30 cells with CCI-779 (5 and 50 ng/ml), an ester analogue of rapamycin, and IGFBP-6 (200 or 1000 ng/ml) also inhibited growth in vitro relative to CCI-779 alone (p < 0.01 and p < 0.001, respectively). In a nude mouse model, xenografts of Rh30 cells transfected with a recombinant vector encoding IGFBP-6 (phBP6-E3) showed delayed growth relative to vector control xenografts (27 days vs. 19 days to reach an average tumour volume of 0.5 cm (3); p < 0.001). Treatment with CCI-779 (10 mg/kg) of mice inoculated with vector control xenografts, also delayed growth (to 31 days; p = 0.0055) relative to untreated mice with vector control xenografts. Co-treatment with CCI-779 (10 mg/kg) reduced phBP6-E3 transfected xenograft growth even further (to 45 days) compared to vector control xenografts (p < 0.001, day 33). CCI-779 thus acts additively with IGFBP-6 to reduce rhabdomyosarcoma growth both in vitro and in vivo.
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PMID:Insulin-like growth factor binding protein-6 and CCI-779, an ester analogue of rapamycin, additively inhibit rhabdomyosarcoma growth. 1471 Mar 64

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