A yeast-one-hybrid (Y1H) four-finger ZFN was designed to replace mutant p53 with wild-type p53 in several cancer cell lines (from glioblastoma, leukemia and breast cancer) via ZFN-induced HR.70 Although the HR events were not particularly effective in this case, modifications at p53 loci still provided a framework for further investigation. The gene discussed is TP53; the disease is breast cancer.