ARID1B and breast carcinoma: They are mutually exclusive subunits of the BAF complex (i.e., the BAF chromatin remodeling complexes can contain either ARID1A or ARID1B, but not both).[11, 13, 16] It has been previously reported that ARID1A‐ or ARID1B‐containing BAF complexes play opposing roles in regulating cell proliferation and osteoblast differentiation.[13, 15, 16, 31, 32] Given this notion, we sought to determine whether OE of ARID1B has any impact on the composition of the BAF complex in breast cancer cells.