This disclosure provides compositions and methods of treating cancer by inhibiting histone methyltransferases alone or in combination by synergistically inhibiting a histone demethylase, or a histone deacetylase (HDAC), or a bromodomain (BRD)-containing protein, or a B-Raf kinase. In particular, the cancers have deficient of SWI/SNF chromatin remodeling complexes because of mutations in one or more of the complex's subunit members.