Examination of effects of daylight on melatonin hormone, kisspeptin protein, skin cancer formation and metastasis in mice

Melatonin is a hormone whose blood level changes inversely proportional to daylight during day cycle. Relationship of skin and breast cancer with constant redundancy of melatonin (i.e. blindness, living in territories that constantly take less sunlight) is already known. Kisspeptin's cellular level is inversely proportional with melatonin level in blood and it is mostly synthesized by the hypothalamus cells of the brain. Kisspeptin functions as a metastasis suppressor in melanomas and breast cancers. With this study, it is aimed to determine the relationship between daylight and melatonin level in blood, relationship between daylight, blood melatonin level and kisspeptin level in cells which are located at the hypothalamus region of brain. In addition, skin cancer is formed on mice to examine the relationship between cancer formation, metastasis, daylight, melatonin levels and kisspeptin levels. For this purpose, new born mice are separated as blind group and daylight group such that blind group is raised in dark and daylight group is raised in 12 hours light/12 hours dark for 17 weeks. At the end of 11th week, melanoma cell lines are inoculated to mice and tumor growth is observed for 6 weeks. At the end of the experiment, melatonin levels are measured from blood serum and kisspeptin levels are measured from hypothalamus. In addition, transcription levels of KISS1 gene in hypothalamus tissue is also detected. At the end of this study, blind group is found have higher melatonin levels and lower KISS1 expression levels with respect to daylight group. Also, melatonin levels are found to be inversely proportional and KISS1 levels are found to be directly proportional with tumor volumes. Moreover, tumor growth speed is found to be lower in blind group than in daylight group. In the light of these results, melatonin and kisspeptin are shown to be important tumor suppressors and these two important elements are highly affected by daylight. In addition, these two tumor suppressors are also found to be affected by the levels of each other, however, this relationship is speculated to be complicated and affected by other factors too instead of being simple and direct.