Gene alterations and apoptosis in rhabdomyosarcoma

The aim of the study is to look retrospectively for gene alterations and evaluate apoptosis in rhabdomyosarcomas (RMSs) from 40 children including 24 patients not previously treated. Histological subtype was botryoid in 1 case, spindle cell in 2 cases, embryonal in 22 cases, alveolar in 10 cases, and undetermined in 5 cases. Gene expression was evaluated immunohistochemically for p53 tumor suppressor gene, MDM2 oncogene, and bcl-2 gene. N-myc amplification was detected by in situ hybridization. Apoptotic cells and bodies were recognized morphologically and stained by 3-OH end labeling. Intranuclear accumulation of p53 protein was obvious (> 25% of tumor cells) in two recurrent embryonal RMSs. Expression of the MDM2 gene was intense (80% of tumor cells) in a recurrent and metastatic embryonal RMS. Amplification of the N-myc gene was obvious (about 20% of tumor cells) in an alveolar RMS metastatic at diagnosis. Expression of the bcl-2 gene was intermediate (25-75% of tumor cells) in 26% of cases and high (> 75% of tumor cells) in 10% of cases either embryonal or alveolar. The percentage of tumor cells showing morphologically recognizable apoptosis was 0.2-7.5% (mean 2.9%). There was no correlation between apoptosis and histological subtype, bcl-2 expression, or previous treatment.