- The proto-oncogene product c-Crk associates with insulin receptor substrate-1 and 4PS. Modulation by insulin growth factor-I (IGF) and enhanced IGF-I signaling. Beitner-Johnson, D., Blakesley, V.A., Shen-Orr, Z., Jimenez, M., Stannard, B., Wang, L.M., Pierce, J., LeRoith, D. J. Biol. Chem. (1996)