ARID1A and endometrial endometrioid adenocarcinoma: In contrast, ARID1A facilitates mismatch repair (MMR) via a functional interaction with MSH2, and this may explain why MMR-deficient cancers, such as subsets of endometrioid uterine carcinoma, and gastric and colorectal carcinoma, show greater frequency of ARID1A loss (Figure 5).