- Acquired resistance to imatinib in gastrointestinal stromal tumor occurs through secondary gene mutation. Antonescu, C.R., Besmer, P., Guo, T., Arkun, K., Hom, G., Koryotowski, B., Leversha, M.A., Jeffrey, P.D., Desantis, D., Singer, S., Brennan, M.F., Maki, R.G., DeMatteo, R.P. Clin. Cancer Res. (2005)