Dim Light at Night Accelerates Mammary Tumor Development and Progression

Madison M. Sites*, William H. Walker II, Raegan Kvadas*, A. Courtney DeVries, and Randy J. Nelson

Department of Neuroscience, Rockefeller Neuroscience Institute, and Department of Medicine, West Virginia University, Morgantown, WV 26505

Presentation Category: Biological & Biochemical Sciences (Poster Presentation #104)

Student’s Major: Biology

Physiology and behavior are optimally regulated via circadian rhythms that are set to precisely 24-hours by daily exposure to bright sunlight. Wide-spread adoption of electric lighting has dramatically affected the circadian organization of individuals. Artificial light at night alters circadian rhythms and negatively affects recovery and progression of medical conditions such as cancer, stroke, cardiac arrest, and mood disorders. This study investigated the effects of exposure to dim light at night (DLAN) on tumor progression and depressive-like behaviors in mice. Adult, female C3H mice received a 100 μl orthotopic injection of the breast cancer cell line FM3A into the 4th mammary gland. Tumor size and body mass were measured over 20 days in five-day intervals following tumor induction. At the end of tumor development (days 19 and 20), depressive-like (sucrose preference test and induced swim tests) and anxiety-like behaviors (open-field test) were assessed. Mice housed in DLAN displayed significantly accelerated mammary tumor development, significantly larger tumors, and gained significantly more body mass than mice housed in dark nights (LD). Tumor bearing mice housed in LD demonstrated increased anxiety-like behaviors. However, housing tumor bearing mice in DLAN normalized this behavior, suggesting DLAN may play an anxiolytic role in tumor bearing mice. There were no significant differences in depressive-like behaviors. Because 99% of the population in North America and Europe are exposed to light at night, these findings and those from future replications may prove useful in managing environmental light conditions in a way that will improve patient outcomes.

Funding: The authors were supported by grants from NINDS (R01NS092388 to R.J.N.), NCI (R01CA194024 to A.C.D.), and NIGMS award number 5U54GM104942-03.

Program/mechanism supporting research/creative efforts: a WVU 297-level course