CYTOGENETIC AND CELLULAR CHARACTERISTICS OF A HUMAN EMBRYONAL RHABDOMYOSARCOMA CELL-LINE, RMS-YM

A human tumour cell line, designated RMS-YM, was established from a childhood rhabdomyosarcoma. The monolayer cells were polygonal, round or spindle-shaped. The cells became multilayered and formed many focal piles when confluent. RMS-YM became stable with a doubling time of about 30 h and has been maintained for 104 passages to date. Tumourigenicity of the cells was confirmed by heterotransplantation into nude mice. Morphological features were similar to those of the primary tumour, and myofibrils were found by electron microscopy. The expression of desmin and human myoglobin, and high levels of striated muscle system specific enzymes were recognised. Chromosomal analysis revealed possible gene amplification in the form of homogeneously staining regions. Oncogene analysis was performed on the primary tumour and the cell line, but neither N-myc nor N-ras genes were amplified, nor were Ki-ras, Ha-ras or N-ras genes mutated at the 12th, 13th and 61st codons. The RMS-YM cell line may provide a system to identify novel genes which are amplified in rhabdomyosarcoma.