ARID1A is part of the large ATP-dependent chromatin remodelling complex SWI/SNF, which is required for transcriptional activation of genes normally repressed by chromatin. It is thought that the protein confers specificity to the SWI/SNF complex and may recruit the complex to its targets through either protein-DNA or protein-protein interactions. ARID1A has been commonly found mutated in gastric cancers, ovarian clear cell carcinoma,[9] and pancreatic cancer. In breast cancer distant metastases acquire inactivation mutations in ARID1A not seen in the primary tumor, and reduced ARID1A expression confers resistance to different drugs such as trastuzumab and mTOR inhibitors.