IGF1R and Ewing sarcoma: Rhabdomyosarcoma and Ewing sarcoma cell lines used by the PPTPC/C were employed to develop evidence for an alternative mechanism of resistance to anti-IGF1R MABs, that being that both intrinsic and acquired resistance are a consequence of redundant signaling by other receptor tyrosine kinases (Shackleford et al., 2023).