GNAS and in situ carcinoma: Validation with whole genome data of the PRISM GC cell lines confirmed negative correlation between CIS/ETP sensitivity and KIT copy number (Fig. 2F), and further identified several gains and losses correlated with CIS sensitivity, such as proximal 1p32-33 gains (CDKN2C, CMPK1, and TAL1) and 20q13 losses (GNAS, AURKA, TOP1, PLCG1, MAFB, and PTPRT) (Supplemental Fig. S2A).