ACTIN, TROPOMYOSIN AND ALPHA-ACTININ AS MARKERS OF DIFFERENTIATION INHUMAN RHABDOMYOSARCOMA CELL-LINES INDUCED WITH DIMETHYL-SULFOXIDE

Most rhabdomyosarcomas are poorly differentiated malignant tumors. Dim ethyl sulfoxide has been shown to modulate cell differentiation in cul tured human cells. We induced differentiation in human rhabdomyosarcom a cell lines A-673, RD and A-204 with 1.25% dimethyl sulfoxide, and us ed desmin, the protein most frequently used as a marker of muscle cell differentiation, to trace this process. As alternative markers of the degree of differentiation, we quantified the expression of the protei ns actin, tropomyosin and alpha-actinin in these cell lines, and follo wed the changes in expression of these proteins after induction for 8, 12, 24, 48 and 72 hrs. In the process of differentiation, protein exp ression in both the cytoplasm and cytoskeleton was significantly incre ased by treatments lasting 12 hrs. (Alpha-actinin) and 24 hrs. (actin) . On the basis of our results, alpha-actinin can be considered as an e arlier marker of differentiation than actin in human rhabdomyosarcoma cell lines. However, the earliest indication of differentiation was a modification in desmin expression (8 hrs.). Because changes in tropomy osin expression were less marked, we consider this protein as a poor m arker of rhabdomyosarcoma cell differentiation.