Melatonin Through DNA Methylation Constricts Breast Cancer Growth Accelerated By Blue LED Light-At-Night In 4T1 Tumor-Bearing Mice

In an attempt to reduce Carbon Dioxide production, lighting technologies are aiming toward the developing of energetically efficient illumination sources as light-emitting diodes (LEDs). LED lamps emit light at short-wavelengths close to the sensitivity peak of melatonin suppression and expected to further exacerbate circadian disruption and cancer risk from increasing exposure to artificial light-at-night (ALAN). We report the effect of ALAN (1x30 min per night) emitted from yellow incandescent or blue-white LED bulbs and melatonin on urinary 6-sulfatoxymelatonin (6-SMT), tumor growth, and global DNA methylation in 4T1 inoculated Balb/c female mice. Blue ALAN significantly decreased 6-SMT, increased tumor growths, and promoted metastasis formation verses yellow exposure. In blue-treated mice, DNA methylation levels were decreased in tumor and liver cells but not in lung and spleen cells compared with yellow-treated mice. Melatonin treatment inhibited tumor growth, reduced metastasis formation, and equally induced hypermethylation under the two spectral compositions. 6-SMTshowed strong inverse and direct correlations with tumor volume and methylation level, respectively. Finally, melatonin treatment increased relative spleen mass with no spectral differences compared with controls