Harnessing the Circadian Clock to Alleviate Ionizing Radiation-Induced Toxicity During Melanoma Therapy

It is known that radiation therapy (RT) targeted to tumors especially melanomas can generate an in-situ tumor vaccine. In other words, inducing the release of antigens during cancer cell death, in association with proinflammatory signals, trigger the adaptive immune system to activate tumor-specific T cells and enhance tumor cell killing. The immune response of RT is especially pronounced in combination with immunotherapy. In our first year funding cycle, with our vivo experiments, we have used genetically mutant circadian clock disrupted PER1/2 mutant mice and rotating shift mice showed a decreased adaptive immune response compared to their wild-type counterparts as an indication of 2-3-fold reduced CD4+ T lymphocytes in blood. In conclusion, these results suggest that circadian clock plays an important role in protecting host adaptive immune response which is important for efficient tumor cell killing against RT. In addition, we have established a circadian synchronization protocol in vitro using B16-F10 melanoma cell lines. During previous year funding cycle, our data suggest that a significantly reduced growth rate in untreated tumors in PER1/2 mutant mice vs. untreated wild-type mice, and a significantly reduced growth rate of wild-type AM immunotherapy treated mice vs. wild-type untreated mice. In addition, there were significantly fewer percent gated CD4 (P=0.023872) and CD8 (P=0.004634) cells in the blood sample of AM immunotherapy treated wild-type mice relative to untreated mice. There were also significantly fewer percent gated CD4 cells (P=0.034883) in the blood of PM immunotherapy treated wild-type mice. For this funding cycle, our results from figures 1-3 demonstrate that a healthy circadian clock protects mice from an aggressive tumor growth pattern, tumor mass, and further induces a more robust immune response against melanoma.