CLOCK and breast cancer: Zienolddiny et al. found that TT carriers in CLOCK rs3749474 had a reduced risk of breast cancer [OR (95%CI) = 0.64 (0.45, 0.92)] among 563 breast cancer cases and 619 controls (Zienolddiny et al. 2013), while Hoffman et al. did not find the significant association between CLOCK rs3749474 and breast cancer risk (Hoffman et al. 2010).