Light at night and breast cancer risk: results from a population-based case-control study in Connecticut, USA.
ABSTRACT To investigate the potential association between domestic exposure to light at night (LAN) and the risk of human breast cancer.
A case-control study of female breast cancer was conducted in Connecticut. A total of 363 incident breast cancer cases and 356 age frequency-matched controls were interviewed using a standardized, structured questionnaire to obtain information on sleeping patterns and bedroom light environment. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by unconditional multivariate logistic regression.
A non-significantly increased risk of breast cancer was observed among postmenopausal women for those keeping lights on while sleeping (OR = 1.4, 95% CI 0.7, 2.7), those who reported mainly sleeping in the daytime (OR = 1.4, 95% CI 0.5, 4.3), and those not drawing the curtains/window shades while sleeping at night (OR = 1.2, 95% CI 0.8, 1.9).
The results from this study suggest a potential increased risk of breast cancer associated with domestic exposure to LAN. Further studies with larger sample size are needed to confirm the results.
Article: Identification of an estrogen-regulated circadian mechanism necessary for breast acinar morphogenesis.[show abstract] [hide abstract]
ABSTRACT: Altered estrogen receptor α (ERA) signaling and altered circadian rhythms are both features of breast cancer. By using a method to entrain circadian oscillations in human cultured cells, we recently reported that the expression of key clock genes oscillates in a circadian fashion in ERA-positive breast epithelial cells but not in breast cancer cells, regardless of their ERA status. Moreover, we reported that ERA mRNA oscillates in a circadian fashion in ERA-positive breast epithelial cells, but not in ERA-positive breast cancer cells. By using ERA-positive HME1 breast epithelial cells, which can be both entrained in vitro and can form mammary gland-like acinar structures in three-dimensional (3D) culture, first we identified a circuit encompassing ERA and an estrogen-regulated loop consisting of two circadian clock genes, PER2 and BMAL1. Further, we demonstrated that this estrogen-regulated circuit is necessary for breast epithelial acinar morphogenesis. Disruption of this circuit due to ERA-knockdown, negatively affects the estrogen-sustained circadian PER2-BMAL1 mechanism as well as the formation of 3D HME1 acini. Conversely, knockdown of either PER2 or BMAL1, by hampering the PER2-BMAL1 loop of the circadian clock, negatively affects ERA circadian oscillations and 3D breast acinar morphogenesis. To our knowledge, this study provides the first evidence of the implication of an ERA-circadian clock mechanism in the breast acinar morphogenetic process.Cell cycle (Georgetown, Tex.) 08/2012; 11(19):3691-700. · 5.36 Impact Factor