title: Ara-C treatment leads to differentiation and reverses the transformed phenotype in a human rhabdomyosarcoma cell line.
abstract: Rhabdomyosarcoma (RMS) is an embryonal tumor of childhood that arises from primitive skeletal muscle-forming cells (rhabdomyoblasts) probably arrested and transformed along the normal myogenic pathway to maturation. Since Ara-C is an antitumor agent known to induce differentiation in human acute myelogenous leukemia, also presumably a disorder of cellular maturation, we treated RD, a human embryonal RMS cell line, with Ara-C and evaluated its effect on growth and differentiation. Ara-C treatment of RD cells in vitro caused a dose-dependent growth inhibition in the absence of cytotoxicity. Interestingly, RD cells treated with 5 x 10(-7) M Ara-C for 4 days were able to recover logarithmic growth after the removal of the drug from the media. A reexposure of these cells to Ara-C led to morphological and biochemical changes related to differentiation, including the appearance of an increased number of multinucleated cells that expressed muscle-specific actin and skeletal muscle myosin heavy chain (MHC) (fast). In vivo studies demonstrated that RD cells pretreated with 5 x 10(-7) M Ara-C lost their ability to form tumors in nude mice. We conclude that treatment of this human embryonal RMS cell line with Ara-C results in marked growth inhibition in vitro, loss of tumorigenicity in vivo, and the expression of biochemical markers present in a more differentiated phenotype. These data suggest a potential role for differentiation therapy as a therapeutic approach in RMS.
authors.affiliation: Pediatric Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: G D
authors.initials: GD
authors.lastname: Crouch
authors.forename: T
authors.initials: T
authors.lastname: Kalebic
authors.forename: M
authors.initials: M
authors.lastname: Tsokos
authors.forename: L J
authors.initials: LJ
authors.lastname: Helman
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects*; D002461:Cell Line, Transformed / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D012208:Rhabdomyosarcoma / Q000188:drug therapy*
chemical_list: D003561:Cytarabine