After the p53 tumor suppressor gene, the genes most frequently found mutated in cancer are those encoding two proteins of the SWI/SNF chromatin remodeling complex. This complex’s function is to ‘accommodate’ the histones that cover the DNA of the chromosomes so that the processes of transcription, DNA repair and replication or chromosome segregation can occur, as appropriate. A group from the University of Seville has demonstrated at CABIMER that the inactivation of BRG1, the factor responsible for the enzymatic activity of the SWI/SNF complexes, leads to high genetic instability, a characteristic common to the vast majority of tumors.