Myc oncogene expression and nude mouse tumorigenicity and metastasis formation are higher in alveolar than embryonal rhabdomyosarcoma cell lines

Accumulated clinical evidence suggests that alveolar rhabdomyosarcoma (ARMS ) is more aggressive than embryonal rhabdomyosarcoma (ERMS). Here, we study six childhood rhabdomyosarcoma cell lines, three ERMS and three ARMS. We h ave assayed the ability of the tumor cells to grow in culture and in nude m ice as well as their propensity for pulmonary metastasis formation by tail vein injection. We also compared levels of c- and N-myc oncogene expression and DNA copy number. We iind no correlation of histologic tumor type (i.e. ERMS versus ARMS with growth rate in culture, but we do find suggestive co rrelations of histologic type with tumorigenicity (mean tumor diameter in m illimeters at 6 wk: ARMS 30, ERMS 10; p(1) = 0.1) and metastasis formation (ARMS 12, ERMS 0; p(1) = 0.1). These properties also correlate with uniform greater overexpression of c-myc in ARMS (mean 39.3-fold. range 16-83) comp ared with ERMS (mean 5.3, range 4-8) (p(1) = 0.05, control fibroblasts = 1) . Although c-myc was often amplified in vitro (four of six lines), there wa s no correlation with histologic type (2/3 ARMS, 2/3 ERMS). These data on r habdomyosarcoma cell lines derived from verified ERMS and ARMS tumors suppo rt the impression from previous clinicopathologic observations that ARMS is a more malignant form of rhabdomyosarcoma than ERMS.