Identification of new genes related to the myogenic differentiation arrestof human rhabdomyosarcoma cells

Rhabdomyosarcoma is a soft tissue tumor committed to the myogenic Lineage b ut arrested prior to terminal differentiation. To identify new genes implic ated 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 h uman embryonal rhabdomyosarcoma cell line RD with different myogenic potent ials: RD/12, which is unable to differentiate, and RD/18, which shows eleme nts able to terminally differentiate, as defined by the expression of myosi n heavy chain (up to 50% of the population) and the formation of multinucle ated myotube-like structures. We identified 80 genes differentially express ed by the two clones. Differentiating RD/18 cells overexpressed the myogeni c transcription factor myogenin along with known myogenic markers; myogenin transfection into undifferentiated RD/12 cells was able to revert the phen otype giving rise to 94% of clones displaying a differentiated morphology. RD/18 cells also expressed several genes not known to be expressed in rhabd omyosarcoma or muscle cells, such as pigment-epithelium derived factor and endothelin-3. Poorly differentiated RD/12 cells, along with genes related t o mesenchymal lineage or early myogenic commitment, also expressed genes no t previously known to be related to the differentiation block of human rhab domyosarcoma, such as monocyte chemotactic protein-1, connective tissue gro wth factor and insulin-like growth factor binding protein-5. Differential e xpression of these genes in a time course of differentiation suggested thei r potential roles as either new myogenic markers or repressors of different iation. These results identify a cluster of new genes related to the aberra nt myogenic differentiation program of human rhabdomyosarcoma cells. (C) 20 01 Elsevier Science B.V. All rights reserved.