ARID1A and neoplasm: For ARID1A (a subunit of SWI/SNF complex), which is immunohistochemically negative when it is mutated36, and the mismatch repair proteins PMS2 and MSH6, the rate of positivity observed in the parental tumor tissues was almost maintained in the PDXs (Fig. 2B, Supplementary Figs. S2B, S2C, S3B, and S3C).