Compared with the K14CreERβF/Fp53F/F mice, the median mammary tumor-free survival period of K14CreERβF/+p53F/F mice was noticeably shorter than that of K14Crep53F/F animals; however, the difference did not reach statistical significance, indicating that loss of both ERβ alleles might be necessary to enhance tumorigenesis in these mice (Fig 2c, d; P = 0.06). The gene discussed is ESR2; the disease is breast cancer.