ABL1 and gastrointestinal stromal tumor: To determine whether ABL1 is expressed in GISTs, we stained imatinib-sensitive (GIST882, GIST-T1) and imatinib-resistant (GIST430, GIST48, GIST48B) GIST cell lines for ABL1 by immunoblotting in comparison to untransformed normal human fibroblasts (NHF; Figure 1A).