Strikingly, secondary KIT mutation (D820Y) was found only in two GIST cell sublines that were cultured in the presence of IM for 20 and 52 weeks, respectively, whereas the remaining 2 IM-resistant GIST sublines that were cultured with IM for 45 and 60 weeks did not harbor KIT mutations due to Sanger sequencing data. The gene discussed is KIT; the disease is gastrointestinal stromal tumor.