Circ-Ccnb1, which is downregulated in BC, binds H2AX and wild-type p53, thus preventing the induction of cell death; however, in p53 mutant cells, circ-Ccnb1 forms a complex with H2AX and Bclaf1 and induces cancer cell death and inhibition of tumor progression151. Here, CCNB1 is linked to breast cancer.