CDKN1B and breast cancer: Indeed, our prior data in women demonstrated that high Ki67+/low p27+ and high Ki67+/low ER+ cell frequencies were significantly associated with a 5-fold higher risk of breast cancer compared to low Ki67+/low p27+ and low Ki67+/low ER+ cell frequencies, respectively, among premenopausal women (Ki67/p27: OR = 5.08, 95% CI = 1.43–18.1; Ki67/ER: OR = 4.68, 95% CI = 1.63–13.5) [50].