MST1R and Ewing sarcoma: Interestingly, all Ewing sarcoma and RH-41 rhabdomyosarcoma cells expressed a single phosphorylated protein band of similar weight as the 125 kDa Δ160E5E6 β-chain, while RH-18 and RH-30 showed a second band corresponding in weight to the 150 kDa β-chain of wild-type RON.