RB1CC1 forms a complex with p53 and/or hSNF5, a chromatin-remodeling factor, in cell nuclei, and activates the transcription of RB1, p16 and p21. In addition, nuclear RB1CC1 significantly correlates RB1 and p16 expression in breast cancer tissue in vivo. The gene discussed is RB1CC1; the disease is breast cancer.