Differential Regulation of Circadian Clock Genes by UV-B Radiation and 1,25-Dihydroxyvitamin D: A Pilot Study during Different Stages of Skin Photocarcinogenesis.

Background: Increasing evidence points at an important physiological role of the timekeeping system, known as the circadian clock (CC), regulating not only our sleep-awake rhythm but additionally many other cellular processes in peripheral tissues. It was shown in various cell types that environmental stressors, including ultraviolet B radiation (UV-B), modulate the expression of genes that regulate the CC (CCGs) and that these CCGs modulate susceptibility for UV-B-induced cellular damage. It was the aim of this pilot study to gain further insights into the CCs' putative role for UV-B-induced photocarcinogenesis of skin cancer.

Cross-talk of Aryl Hydrocarbon Receptor (AHR)- and Vitamin D Receptor (VDR)-signaling in Human Keratinocytes.

Background/aim: Vitamin D receptor (VDR), activated upon binding of 1,25(OH)D, was described as a tumor suppressor in the skin. New biological functions of non-classical vitamin D derivatives were recently identified, that are mediated via binding to alternate receptors, including the aryl hydrocarbon receptor (AHR) and that indicate functional interaction between AHR and VDR signaling in various human tissues. We aimed to gain further insights into the cross-talk of VDR and AHR signaling in skin photo-carcinogenesis.