Description
Breast cancer is the most common cancer, accounting for 22.8 % of the total number of the incident cancer cases worldwide (Globocan, 2008). In spite of growing body of evidence suggesting link between night shift work and breast cancer risk, the mechanisms underlying this association remain to be elucidated. We predict that promoters of the circadian rhythm genes and cell cycle regulatory genes are differently methylated in night shift nurses versus nurses working during the days. The results of our study will be disseminated to research community, interested parties, and to stakeholders. During this project we will continue close cooperation with society of nurses and midwives in Poland and Norway and other policy making and regulatory authorities. From the Norwegian National Institute of Occupational Health two Departments will participate: Section for Toxicology and Department of Occupational Medicine and Epidemiology, with cooperation of Cancer Registry of Norway with researchers having experience in conducting studies in the area of cancer, occupational and molecular epidemiology. The analyses will be performed using equipment at the lab.
Summary of project results
The influence of the night shift work on cancers incidence risk has drawn much attention of researchers and stakeholders over the last years worldwide, including Norway and Poland. Through common initiative of Polish and Norwegian researchers we were able to test mechanistic hypotheses addressing a number of key issues potentially relevant to breast carcinogenesis in women with night shift exposure. The primary focus of the proposal was to investigate the association between night shift work and epigenetic changes. We analyzed DNA samples and determined global methylation and methylation status of the promoters of core circadian genes, melatonin receptors, estrogen and progesterone receptors, cell cycle regulatory genes, and tumour suppressor genes. The samples were from two populations, i.e. Polish nurses (n=710), and Norwegian nurses (n=354 breast cancer cases, and n=356 controls). In addition effects of the night shift on lifestyle, sex hormones, sleep quality, and further interrelationships with methylation pattern were investigated. Our study did not revealed any strong associations between night work and epigenetic changes in form of DNA methylation within circadian rhythm or cancer suppressor genes. However, we found that methylation levels of progesterone receptor are different between day and shift working nurses. The study confirmed previously observed unhealthy lifestyle among night workers, such as smoking cigarettes, lower recreational physical activity and obesity. In addition our study suggested that smoking may be one of the environmental determinants of methylation of the promoter region within the BRCA1 gene and TP53. Moreover our study implied that prolonged night shift work may be associated with increased estradiol levels among postmenopausal women. Interesting finding of our study was also that shorter sleep(
Summary of bilateral results
The researchers from the Nofer Institute of Occupational Medicine (Lodz, Poland ) and the National Institute of Occupational Health (Oslo, Norway) had already undertaken a common efforts to investigate the mechanisms underlying the increased breast cancer risk among night shift working nurses and midwives in the run of a previous Polish Norwegian Research Fund Program ( in the years 2008-2011). The current granting allowed us to continue the cooperation in this field. During the project formal meetings of the whole research team were held (kick-off, mid-term and final), providing the opportunity to share knowledge and experiences. In addition WP leaders contacted regularly on a daily basis through e-mail exchanges. The collaboration resulted with common publications and poster presentations during the international conferences. The webpage presenting the project has been elaborated by beneficiary and partner (3 versions: Polish, Norwegian and English). The grant proposal was prepared during the run of the project and submitted to the Polish national granting system. The topic of this proposal is coherent with the current project, and future sustainable cooperation is envisaged.