KIT and gastrointestinal stromal tumor: Our GIST PDX models, GIST-RX1, GIST-RX2, and GIST-RX4, harbored secondary mutations in KIT exon 17 (p.D816E), exon 14 (p.T670I), and exon 17 (p.D820E), respectively, which have not been reported in prior studies.