title: RasGRF1 regulates proliferation and metastatic behavior of human alveolar             rhabdomyosarcomas.
abstract: The involvement of the Ras superfamily of GTPases in the pathogenesis of rhabdomysarcoma (RMS) is not well understood. While mutant H-Ras leads to embryonal RMS (ERMS) formation in experimental animals and in Costello syndrome patients, no data exists on the potential role of Ras GTPases in the pathogenesis of alveolar RMS (ARMS). To address this issue better, we focused on the role of the GTP exchange factor RasGRF1 in this process. We observed that, in comparison to normal skeletal muscle cells, RasGRF1 mRNA is upregulated in the majority of human ARMS cell lines and subsequently confirmed its high expression in patient samples. By employing confocal microscopy analysis, we observed RasGRF1 accumulation in cell filopodia, which suggests its involvement in ARMS cell migration. Furthermore, we observed that RasGRF1 becomes phosphorylated in ARMS after stimulation by several pro-metastatic factors, such as SDF-1 and HGF/SF, as well as after exposure to growth-promoting Igf-2 and insulin. More importantly, activation of RasGRF1 expression correlated with activation of p42/44 MAPK and AKT. When the expression of RasGRF1 was down-regulated in ARMS cells by an shRNA strategy, these RasGRF1-kd RMS cells did not respond to stimulation by SDF-1, HGF/SF, Igf-2 or insulin by phosphorylation of p42/44 MAPK and AKT and lost their chemotactic responsiveness; however, their adhesion was not affected. We also observed that RasGRF1-kd ARMS cells proliferated at a very low rate in vitro, and, more importantly, after inoculation into immunodeficient SCID/beige inbred mice they formed significantly smaller tumors. We conclude that RasGRF1 plays an important role in ARMS pathogenesis and is a new potential therapeutic target to inhibit ARMS growth.
authors: Stem Cell Institute at James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA.
authors: Maciej
authors: M
authors: Tarnowski
authors: Gabriela
authors: G
authors: Schneider
authors: Gabriele
authors: G
authors: Amann
authors: Geoffrey
authors: G
authors: Clark
authors: Peter
authors: P
authors: Houghton
authors: Frederic G
authors: FG
authors: Barr
authors: Lukas
authors: L
authors: Kenner
authors: Mariusz Z
authors: MZ
authors: Ratajczak
authors: Magda
authors: M
authors: Kucia
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D054377:Chemokine CXCL12 / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017228:Hepatocyte Growth Factor / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D008715:Methionine / Q000031:analogs & derivatives / Q000494:pharmacology; D051379:Mice; D016513:Mice, SCID; D019950:Mitogen-Activated Protein Kinase 1 / Q000096:biosynthesis / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000096:biosynthesis / Q000378:metabolism; D009362:Neoplasm Metastasis; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011554:Pseudopodia / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering; D018232:Rhabdomyosarcoma, Alveolar / Q000235:genetics / Q000378:metabolism* / Q000473:pathology* / Q000556:secondary; D015854:Up-Regulation; D020666:ras-GRF1 / Q000235:genetics / Q000378:metabolism*
chemical_list: C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D004791:Enzyme Inhibitors; C096856:FTI 277; C066855:HGF protein, human; D007328:Insulin; C513039:RASGRF1 protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D020666:ras-GRF1; D017228:Hepatocyte Growth Factor; D007335:Insulin-Like Growth Factor II; D008715:Methionine; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3