DETECTION OF THE MYOD1 TRANSCRIPT IN RHABDOMYOSARCOMA CELL-LINES AND TUMOR SAMPLES BY REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma of child hood. Diagnosis of RMS can be difficult when it appears as a small rou nd-cell tumor without evidence of differentiation. Recently, a set of regulatory proteins expressed during skeletal muscle development has b een described. Among them, MyoD1 has been detected by Northern blot an d immunohistochemical analyses in normal skeletal muscle and RMS. Give n the relevance of this marker in the diagnosis of RMS, we developed a n assay to evaluate the expression of MyoD1 mRNA in small tissue speci mens by reverse transcription polymerase chain reaction. Specificity a nd sensitivity of the assay was determined in a series of 25 tumor cel l lines and 39 pediatric tumor samples, including 35 RMSs. Subsequentl y, we studied the expression of MyoD1 in bone marrow and peripheral bl ood stem cell specimens. We detected the MyoD1 transcript in normal sk eletal muscle and in almost all RMSs, whereas no expression was found in non-RMS samples or in normal hematopoietic tissues. This assay show ed high sensitivity and specificity, and it could be a useful molecula r tool for the diagnosis of RMS within small round-cell tumors of chil dhood and for the detection of minimal bone marrow and peripheral bloo d stem cell involvement in children with RMS, regardless of the histol ogical subtype.