Circadian dysrhythm and advanced prostate cancer.

Abstract

199 Background: The circadian rhythm regulates diverse biologic pathways including tumor oncogenes, metabolism, and cell proliferation. Dysregulation of the circadian rhythm arises from faulty input signals such as exposure to light at night, variability in core circadian rhythm genes, and variation in outputs that regulate circadian behavior including melatonin. There is compelling biologic rationale, but little human data, on circadian dysrhythm and advanced prostate cancer. Methods: We undertook an integrative molecular epidemiology study of circadian dysrhythm and advanced prostate cancer among men in the Icelandic AGES-Reykjavik cohort and the U.S. Health Professionals Follow-up Study, which allowed integration of questionnaire data, biorepositories, and long-term follow-up. We characterized circadian dysrhythm using complimentary approaches: information on sleep problems from questionnaires, prediagnostic melatonin (6-sulfatoxymelatonin) measured on first morning void urine samples, and genetic variation across twelve circadian clock genes. We used multivariable regression models to estimate relative risks (RR) and 95% confidence intervals (CI) of associations with advanced prostate cancer, adjusted for potential confounders. Results: Twenty percent of men reported sleep problems. Men who had trouble falling asleep (RR = 2.1; 95% CI 0.7-6.2) and staying asleep (RR=3.2, 95% CI 1.1-9.7) had an increased risk of developing advanced prostate cancer. Men with sleep problems had significantly lower melatonin levels compared to those without. Low melatonin levels were associated with a statistically significant 4-fold higher risk of advanced prostate cancer compared to those with high levels (95% CI: 1.25-10.0). Variant alleles in two SNPs in cryptochrome (CRY1), involved in generating and maintaining circadian rhythms, were significantly associated with risk of advanced prostate cancer in both cohorts, with a gene-level p-value<0.01. Conclusions: Our results suggest there are multiple nodes in the circadian rhythm that are associated with an increased risk of advanced prostate cancer. As such, there is the potential for complimentary strategies to target circadian disruption and reduce the risk of advanced prostate cancer.