Effects of chronobiology on prostate cancer cells growth in vivo

Background and objective: The increased risk of developing prostate cancer (PC) observed in recent decades in industrialized countries has showed to be related at least partially to the elevated exposure to artificial light at night and to long photoperiod during all the year. However, the precise effects of light and photoperiod manipulations on prostate cancer cell proliferation in vivo have not been reported to the same extent.Methods: We exposed male C57BL/6 mice to short or long photoperiods (short day, SD, and long day, LD). After inoculation of TRAMP-C2 cells, half of the SD mice were also exposed to light interference at night while half of the LD mice were treated with melatonin. Results: Under LD-acclimation, tumours were significantly larger compared to SD conditions. Melatonin treatment to LD mice reduced tumour size significantly, while light interferences to SD mice tended to increase it. Conclusions: we conclude that exposure to LD and light interference may promote cancer growth via changes in melatonin production and secretion. Our results strongly support a novel link between temporal variables and cancer incidence. Accordingly, we anticipate our findings to increase the awareness of scientists as well as health officials and policy makers to the adverse effects of illumination misuse during the night.