PTEN and gastrointestinal stromal tumor: We have previously reported the establishment of 3 separate GIST PDX models - GIST-RX1 (mutations in KIT exons 11, 17, and PTEN from a patient with resistance to imatinib, sunitinib, and sorafenib), GIST-RX2 (mutations in KIT exons 11 and 14 from a patient with resistance to imatinib), and GIST-RX4 (mutations in KIT exons 9 and 17 from a patient with resistance to imatinib and sunitinib)17.