HRR (Rad51 as a marker) was activated in p53+/+;ErbB2, p53−/+;ErbB2, p53H/+;ErbB2 and p53−/−;ErbB2 but was suppressed in p53H/−;ErbB2 and p53H/H;ErbB2 mammary tumors (Fig. 4a and Supplementary Fig. 3a). The gene discussed is TP53; the disease is breast cancer.