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

In vitro cultures and clonal derivatives have been established from rat rhabdomyosarcomas induced by Moloney-Murine Sarcoma Virus (MSV) or by nickel sulfide; differentiation ability has been studied as expression of desmin, embryonic and adult myosin isoforms, alpha-actin isoforms and cellular fusion. The two rhabdomyosarcoma models showed different levels of myogenic differentiation. Multinucleated myotube-like structures were frequently observed in cultures derived from nickel-induced tumours. Desmin was present in 50-80% of cells and embryonic myosin in up to 10%. In MSV-tumour-derived cultures and in their metastases or clonal derivatives two cell types are present in different ratios: spindle-shaped cells, adherent to plastic surfaces, and rounded cells, loosely attached or floating free in the medium. These cultures showed features of myogenic differentiation (10-80% desmin-positive cells), but embryonic myosin expression and production of multinucleated myotube-like structures were very rare events. Cultures from autochthonous lymph node and lung metastatic cells showed similar patterns of differentiation. Retinoic acid increased differentiated features (myotube formation and embryonic myosin expression) only in nickel-induced rhabdomyosarcoma cells. The two models described here mimic the heterogeneity in differentiation pattern found among human rhabdomyosarcomas. Myogenic differentiation ability was retained at a good level by nickel-induced tumours, whereas it was strongly impaired in MSV-induced tumours.
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PMID:In vitro differentiation of rhabdomyosarcomas induced by nickel or by Moloney murine sarcoma virus. 203 98

A series of 15 rhabdomyosarcomas was examined by light microscopy, transmission electron microscopy, two-dimensional gel electrophoresis (2D-GE) and indirect immunofluorescence, the latter using monoclonal or affinity-purified polyclonal antibodies to desmin, vimentin, alpha-smooth muscle and alpha-sarcomeric (alpha-sr) actins. By light microscopy, the authors diagnosed 1 botrioid, 1 alveolar, and 7 embryonal rhabdomyosarcomas, 4 pleomorphic spindle cell sarcomas, and 2 spindle cell sarcomas, one nondistinct, the other with a hemangiopericytomatous pattern. By transmission electron microscopy, 13 neoplasms disclosed rhabdomyoblastic differentiation; the remaining 2, myogenic differentiation. By immunofluorescence microscopy, all neoplasms expressed vimentin and alpha-sr actin, 12 expressed, in addition, desmin, and 1 expressed alpha-smooth muscle actin. Among the 11 neoplasms studied by means of 2D-GE, 7 demonstrated an alpha-actin spot, while 4 showed only beta and gamma spots. One tumor disclosed, in addition to alpha, beta, and gamma spots, a spot with a molecular weight corresponding to actin, but more acidic than alpha-actins. This study demonstrates that alpha-sr actin antibody represents a valuable marker for the diagnosis of rhabdomyosarcoma, because it was present in all neoplasms, including the one negative for desmin. This antibody further allowed the recognition of pleomorphic variants and morphologically atypical forms of rhabdomyosarcomas. The presence of alpha-smooth muscle actin in 1 case of rhabdomyosarcoma suggests that this actin isoform may be expressed during skeletal muscle differentiation.
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PMID:Intermediate filament proteins and actin isoforms as markers for soft tissue tumor differentiation and origin. II. Rhabdomyosarcomas. 327 94

Human rhabdomyosarcoma RD cells express the myogenic regulatory factors MyoD and myogenin but differentiate spontaneously very poorly. Prolonged treatment of RD cells with the protein kinase C (PKC) activator 12-O-tetradecanoylphorbol-13-acetate (TPA) induces growth arrest and myogenic differentiation as shown by the accumulation of alpha-actin and myosin light and heavy chains, without affecting the expression of MyoD and myogenin. In this study, we show that short-term phorbol ester treatment of the cultures is sufficient to trigger myogenic differentiation but not growth arrest. Furthermore, PKC inhibitors, such as staurosporine or calphostin C, prevent TPA-induced differentiation but not cell growth arrest. These data suggest that the two events are mediated by different pathways; a possible interpretation is that the activation of one or more PKC isoforms mediates the induction of differentiation, whereas the down-regulation of the same or different isoforms mediates the growth arrest. To address the mechanism whereby TPA affects cell growth and differentiation in RD cells, we first analyzed PKC isoenzyme distribution. We found that RD cells express the alpha, beta 1, gamma, and sigma PKC isoenzymes. Only the alpha isoform is exclusively found in the soluble fraction, but it translocates to the membrane fraction within 5 min of TPA treatment and is completely down-regulated after 6 h. The other isoenzymes are found associated to both the soluble and the particulate fractions and are down-regulated after long-term TPA treatment. By immunofluorescence analysis, we show that the PKC alpha down-regulation is specific for those cells that respond to TPA by activating the muscle phenotype. We propose that TPA-induced differentiation in RD cells is mediated by the transient activation of PKC alpha, which activates some of the intracellular events that are necessary for MyoD and myogenin transacting activity and for the induction of terminal differentiation of RD cells. By contrast, the constitutively active beta 1 and sigma are responsible for the maintenance of cell growth, and their down-regulation is responsible for long-term TPA-induced cell growth arrest.
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PMID:Rapid activation and down-regulation of protein kinase C alpha in 12-O-Tetradecanoylphorbol-13-acetate-induced differentiation of human rhabdomyosarcoma cells. 754 6

Development of primary cultured chicken myogenic cells were studied using living cell micro-morphoanalysis, muscle specific protein immunofluorescent double staining, image projection analysis and 3H-TdR incorporation autoradiography methods. Changes in single, normal newborn myoblasts from the time of their last mitosis until 22 hr old were followed. All +/- 4 hr myoblasts were desmin+ and most were positive for alpha-actinin, zeugmatin, troponin-I (TnI), alpha-actin. titin, nebulin and myosin heavy chain (MHC). There was no obligatory temporal or spatial sequence in the order of the appearance of the major myofibrillar proteins. Nascent sister myoblasts assumed an exceptionally elongated bipolar morphology that is as singular to mononucleated postmitotic myoblasts as is their capacity to transcribe myofibrillar genes. The assembly of non-striated myofibrils (NSMFs) was evident in all 6-8 hr cells and was initiated in the absence of myomesin and C-protein. Myomesin first appeared along NSMFs in 10-14 hr old cells. C-protein was only found localized to transverse doublets bisecting 1.6 microns wide A-bands of assembled sarcomeres. Each newly assembled sarcomere presented the same invariant distribution of proteins that is found in adult sarcomeres. There is a lag of 16 or more hours between the first appearance of most of the major myofibrillar proteins and their assembly into NSMFs and the first appearance of striated myofibrils (SMFs). The observations indicated that the majority of normal myoblasts up-regulate the synthesis of myofibrillar proteins prior to, not after, fusion. In brief, new-born +/- 4 hr myoblasts expressed their differentiation program in the process as (1) withdrawal from the cell cycle: (2) initiation of synthesis and accumulation of desmin and 7 early myofibrillar proteins: (3) cellular elongation and assembly of NSMFs and SMFs: (4) acquisition of a fusion-competent sarcolemma. The expression of this cell autonomous myogenic differentiation program is distorted or blocked in rhabdomyosarcoma RD cells. The majority of RD cells expressed desmin (50-90%): among these desmin+ cells, 10-20% incorporated 3H-TdR. In addition, 60-78% of the mitotic cells were desmin+. Most desmin+ cells were myofibrillar protein negative. Only a small number of tumor cells (5-10%) expressed MHC, titin, alpha-actinin and s-alpha-actin. 3H-TdR positive nuclei were observed in these myofibrillar protein+ cells: 11-12% in titin+ or nebulin+ cells and 4% in MHC+ cells. But none of the mitotic cells were myofibrillar protein+.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Expression of myogenic differentiation program in cultured normal postmitotic mononucleated myoblasts and the aberrant differentiation in rhabdomyosarcoma cells]. 804 10