Night shift worker’s clock genes can affect risk of breast cancer
03 Jul 2013
Specific variations in clock genes are involved in the increased risk of breast cancer seen in women who work nights, suggests research in BioMed Central’s open access journal Breast Cancer Research. By looking at naturally occurring variations in the genes responsible for the circadian rhythm, known as clock genes, researchers from National Institute of Occupational Health in Norway found that nurses with particular variants had a lower or higher risk of breast cancer.
Night shift workers seem to have an elevated risk of breast cancer compared to the general population, but the reason behind this is unclear. This risk is so striking that the International Agency for Research on Cancer classifies night work as a probable carcinogen. Working at night is thought to disrupt the body’s natural circadian rhythms and impacts the production of hormones, including melatonin, which normally has its peak production at night.
Nurses with at least five years of work, including six or more consecutive night shifts per month, had an approximately two-fold increased risk of breast cancer, compared to nurses on the day shifts. This study links this increase to two specific variations in the gene (AANAT), coding for Serotonin N-acetyltransferase, which is involved in the manufacture of melatonin. Decreased risk was associated with a specific variant of a clock gene called CLOCK, which controls circadian rhythms, and BMAL1, whose protein binds to the protein made by CLOCK.
The effect of these genetic variations depended on the number of nights worked at a time. Dr Shanbeh Zienolddiny, who led this study, explained, “We found another variant of CLOCK that was associated with a reduced risk of breast cancer for women who worked three successive nights, but an increased risk at four or more nights. This indicates that the role of these genes are complex, and we do not yet know the full story. Understanding clock genes, and the processes they control, is likely to be important in understanding the mechanisms of cancer risk.”
- ENDS –
Dr Hilary Glover
Scientific Press Officer, BioMed Central
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Notes to Editors
1. Analysis of polymorphisms in the circadian-related genes and breast cancer risk in the Norwegian nurses working night shifts
Shanbeh Zienolddiny, Aage Haugen, Jenny-Anne Sigstad Lie, Helge Kjuus, Kristine Haugen Anmarkrud and Kristina Kjærheim
Breast Cancer Research 2013, 15:R52
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2. Breast Cancer Research is an international, peer-reviewed online journal, publishing original research, reviews, commentaries and reports. Research articles of exceptional interest are published in all areas of biology and medicine relevant to breast cancer, including normal mammary gland biology, with special emphasis on the genetic, biochemical, and cellular basis of breast cancer. In addition, the journal publishes clinical studies with a biological basis, including Phase I and Phase II trials.
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