ZSWIM4 and gastrointestinal stromal tumor: However, treatment of KITV558A/WT mice with imatinib, and treatment of GIST cells with imatinib or KIT siRNAs increase the distribution of ZSWIM4 in the cytoplasm (Fig. 5A, B, C), indicating that KIT signaling is important for the entry of ZSWIM4 to the nucleus.