BRCA1 and BRCA2 Gene Expression: Diurnal Variability and Influence of Shift Work

Cancers 201911(8), 1146;
Received: 10 July 2019 / Revised: 5 August 2019 / Accepted: 7 August 2019 / Published: 9 August 2019

(This article belongs to the Special Issue 3rd Etnean Occupational Medicine Workshop—Breast Cancer and Work)


BRCA1 and BRCA2 genes are involved in DNA double-strand break repair and related to breast cancer. Shift work is associated with biological clock alterations and with a higher risk of breast cancer. The aim of this study was to investigate the variability of expression of BRCA genes through the day in healthy subjects and to measure BRCA expression levels in shift workers. The study was approached in two ways. First, we examined diurnal variation of BRCA1 and BRCA2 genes in lymphocytes of 15 volunteers over a 24-hour period. Second, we measured the expression of these genes in lymphocytes from a group of shift and daytime workers. The change in 24-hour expression levels of BRCA1 and BRCA2 genes was statistically significant, decreasing from the peak at midday to the lowest level at midnight. Lower levels for both genes were found in shift workers compared to daytime workers. Diurnal variability of BRCA1 and BRCA2 expression suggests a relation of DNA double-strand break repair system with biological clock. Lower levels of BRCA1 and BRCA2 found in shift workers may be one of the potential factors related to the higher risk of breast cancer.

Added note by EMFSA:
Smj Mortazavi:
Screen time or the amount of time a person uses digital screens (displays) of smartphones, laptop computers, and tablets (e.g. iPads) can be a risk factor that should be taken into account because it can cause circadian disruption in BRCA mutation carriers. Since heterozygous mutation of BRCA genes increases the risk of breast cancer, precautionary attention should be taken for factors able to cause circadian disruption in BRCA mutation carriers [68]. Occupational Physicians should carefully evaluate the exposure to shift work, in particular to shift schedules that have frequent, long-term or a large number of night shifts over a lifetime, in BRCA mutation carriers“.
68. Mortazavi, S.A.R.; Mortazavi, S.M.J. Women with hereditary breast cancer predispositions should avoid using their smartphones, tablets, and laptops at night. Iran. J. Basic Med. Sci. 201821, 112–115. [Google Scholar] [PubMed]

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