Fasting regimens, like intermittent or periodic fasting, and caloric restriction have been shown to ameliorate a number of disease symptoms and to increase health span and even longevity in many model organisms from bacteria to non-human primates (Longo, Mattson, Cell Metabolism, 2014). While the first clinical trials are underway, the molecular mechanisms underlying these beneficial effects remain largely elusive. In our lab we investigate the impact of fasting on transcription factor networks in different cellular contexts. Our current projects focus on the transcription factor and tumor suppressor p53 as key player in the systemic fasting response. We study p53 action under fasting in liver and adipose tissues using novel mouse models and genome-wide methods. In another project we test the hypothesis that p53 is involved in the chemotherapy-supporting effect of fasting in hepatocellular carcinoma.