COX7A1 and rhabdomyosarcoma: COX7A1, previously described as being highly expressed in skeletal and cardiac myocytes [30], was expressed at high levels in the adult-derived myoblasts, but was not expressed in the embryonic myoblast progenitor line, SK5, nor was it expressed in 4 out of 5 of the rhabdomyosarcoma cell lines (Figure 4A).