SH3BP2 and gastrointestinal stromal tumor: To study SH3BP2 function, we characterized three different cell lines derived from GIST patients: GIST882 (KIT exon 13 K642E), an imatinib‐sensitive cell line; GIST48 (KIT exon 11 D820A plus KIT exon 17 V560D), an imatinib‐resistant cell line; and GIST48B, a subline of GIST48, which, despite retaining the activating KIT mutation, expresses KIT transcript and protein at essentially undetectable levels (Muhlenberg et al., 2009).