In cancer, liquid biopsies such as plasma are an extremely attractive resource for the discovery of novel biomarkers. In contrast to tissue biopsies, plasma can be collected in a minimally invasive manner, enabling serial sample collection throughout treatment and follow-up of cancer patients. Cancer biomarkers in plasma could therefore be exploited for diagnosis, therapy response monitoring or relapse detection. In the context of potential biomarker identification, this project will focus on circulating RNAs (mRNAs, circular RNAs and long non-coding RNAs) in plasma. The aim is to evaluate to what extent changes in tumor- and tissue-derived RNA signals in plasma correlate with disease state, response to treatment and relapse of cancer patients. More than 200 plasma samples from patients with metastasized cancer will be used to look at the impact of different cancer types on the plasma RNA profile (samples cover 25 different cancer types in total). Moreover, for two cancer types, results will be validated in murine cancer models and larger cohorts of cancer patients. Additionally, longitudinal plasma samples from cancer patients will be used to study changes in RNA profiles during treatment and disease progression.