Myostatin inhibits rhabdomyosarcoma cell proliferation through an Rb-independent pathway.
Rhabdomyosarcoma (RMS) tumors are the most common soft-tissue sarcomas in childhood. In this investigation, we show that myostatin, a skeletal muscle-specific inhibitor of growth and differentiation is expressed and translated in the cultured RMS cell line, RD. The addition of exogenous recombinant myostatin inhibits the proliferation of RD cells cultured in growth media, consistent with the role of myostatin in normal myoblast proliferation inhibition. However, unlike normal myoblasts, upregulation of p21 was not observed. Rather, myostatin signalling resulted in the specific downregulation of both Cdk2 and its cognate partner, cyclin-E. The analysis of Rb reveals that there was no change in its phosphorylation status with myostatin treatment, consistent with D-type-cyclin-Cdk4/6 complexes being active in the absence of p21. Moreover, the activity of Rb appeared to be unchanged between treated and nontreated RD cells, as determined by the ability of Rb to bind E2F1. The examination of NPAT, a substrate of cyclin-E-Cdk2 involved in the transcriptional activation of replication-dependent histone gene expression, revealed that it undergoes a loss of phosphorylation with myostatin treatment. Supporting this, a downregulation in H4-histone gene expression was observed. These results suggest that myostatin could potentially be used as an inhibitor of RMS proliferation and define a previously uncharacterized, Rb-independent mechanism for the inhibition of muscle precursor cell proliferation by myostatin.
Langley
Brett
B
Animal Genomics, AgResearch, Private Bag 3123, East Street, Hamilton, New Zealand.
Thomas
Mark
M
McFarlane
Craig
C
Gilmour
Stewart
S
Sharma
Mridula
M
Kambadur
Ravi
R
D042846:CDC2-CDC28 Kinases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006657:Histones / Q000235:genetics; D006801:Humans; D055435:Myostatin; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein / Q000378:metabolism*; D012208:Rhabdomyosarcoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D018797:Cell Cycle Proteins; D019927:Cyclin E; D006657:Histones; C525911:MSTN protein, human; D055435:Myostatin; C101693:NPAT protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D016212:Transforming Growth Factor beta; D019938:Cyclin D1; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases