Inhibition of Differentiation by Transforming Growth Factor β1 in Rhabdomyosarcoma Cells

OBJECTIVE To study the effect of transforming growth factor β1 （TGF-β1） on differentiation of rhabdomyosarcoma （RMS） cells METHODS RD （human embryonal RMS cell line） cells, cultured in differentiation medium containing 9-cis retinoic acid （9CRA）, were treated with TGF-β1. Proliferation of the cells was examined by the MTT assay. The differentiation specific proteins （sarcomeric actin and MyHC） and myogenic transcription factors （MyoD1 and myogenin） in the RD cells were assessed by immunofluorescence staining. RESULTS Compared to control cells, treatment with lower concentrations of TGF-β1 （0.1 and 0.2 ng/ml） induced an increase in OD values after 4 d （P〈0.01）, whereas higher concentrations of TGF-β1 （2 and 5 ng/ml） led to a reduction of cell viability （P〈0.01）. After exposure to 9CRA, the viability of the cells decreased significantly （P〈0.01）, while sarcomeric actin, MyHC and myogenin were induced. These changes were antagonized by TGF-β1 （0.1 ng/ml）. No changes were observed in expression of MyoD1. CONCLUSION The RMS cells, derived from myogenic progenitors are committed to a myogenic fate, but are arrested in the differentiation course by the addition of TGF-β1 which represses some of the myogenic transcription factors.

OBJECTIVE To study the effect of transforming growth factor?1 (TGF-β1)on differentiation of rhabdomyosarcoma(RMS)cells METHODS RD(human embryonal RMS cell line)cells,cultured in differentiation medium containing 9-cis retinoic acid(9CRA),were treated with TGF-β1.Proliferation of the cells was examined by the MTT assay.The differentiation specific proteins(sarcomeric actin and MyHC)and myogenic transcription factors(MyoD1 and myogenin)in the RD cel s were assessed by immunofluorescence staining. RESULTS Compared to control cel s,treatment with lower concentrations of TGF-?1(0.1 and 0.2 ng/ml)induced an increase in OD values after 4 d(P<0.01),whereas higher concentrations of TGF-?1(2 and 5 ng/ml)led to a reduction of cell viability(P<0.01).After exposure to 9CRA,the viability of the cells decreased significantly(P<0.01),while sarcomeric actin,MyHC and myogenin were induced.These changes were antagonized by TGF-β1(0.1 ng/ml).No changes were observed in expression of MyoD1. CONCLUSION The RMS cells,derived from myogenic progenitors are committed to a myogenic fate,but are arrested in the differentiation course by the addition of TGF-?1 which represses some of the myogenic transcription factors.