Characterization of a human rhabdomyosarcoma cell strain in tissue culture.

: A new human rhabdomyosarcoma cell strain, designated KYM-1, has been established from a neck tumor found in a 9-month-old infant. The cultured cells were round and mainly free-floating or in a moniliform pattern with a population doubling time of 75 hours. In stained preparations, the cells were pleomorphic and had a single round or oval nucleus in non-striated cytoplasm. However, the intracellular presence of myogenic markers was clearly shown by enzyme-immunochemical stains. An ultrastructural feature of the KYM-1 cells was the presence of numerous intermediate filaments in the perinuclear area and around the Golgi complexes which were associated with abundant cell organelles and aggregates of glycogen granules. High viscosity of the spent culture medium was attributed to hyaluronic acid, identified by electrophoresis and hyaluronidase digestion, and immunological and biochemical analyses revealed that the increased concentration of plasminogen activator activity found in the culture medium was almost wholly of the tissue plasminogen activator type. The KYM-1 cells also contained high concentrations of alkaline phosphatase activity. Tumorigenicity of the cells was confirmed by heterotransplantation into hamsters treated with anti-thymocyte serum.