The use of Northern blots for alpha-CARD actin as an adjunct to conventional techniques may be helpful for the precise identification of primary RMSs compared to other soft tissue neoplasms.
The present study indicates that both muscle-specific actin and desmin can be expressed in tumors lacking ultrastructural evidence of a rhabdomyoblastic differentiation and that the combined use of monoclonal antibodies to desmin and muscle-specific actin is of value when it comes to recognizing rhabdomyosarcomas within the group of undifferentiated small and dark cell malignancies of soft tissue tumors.
In addition, MAbs to the cytoplasmic protein desmin, myoglobin, muscle actin (alpha and gamma) and alpha-sarcomeric actin reacted with these cell lines, SCMC-RM2 and SCMC-RM2-1 being thus identified as rhabdomyosarcoma.
Taken together with the results of recent reports indicating that the cardiac alpha-actin type is a marker of embryonic and fetal skeletal muscle, our findings indicate that rhabdomyosarcomas express the embryonic sarcomeric actin isoform.