ARID1A and neoplasm: Since ARID1A genetic or mutation status was not available, we assigned an ARID1A mutant-like signature score to each PDX tumor, and stratified the 132 eRAS/BRAF WT tumors into an ARID1A mutant-like vs. WT-like group based on the top quartile as previously described in Supplementary Fig. 7a.