Circulating nucleic acids and protease activities in blood of tumor patients

Introduction: Carcinogenesis is accompanied by deregulated tumor cell death and changes in proliferative processes. Apoptotic cells release different components, such as nucleosomes and caspases, into the blood circulation that can be detected by minimally invasive assays. Caspases belong to a large family of proteases, which are frequently overexpressed in various cancer entities and involved in metastases. One critical event of tumor invasion that signals the initiation of the metastatic cascade is the degradation of basement membrane components by protease supporting invasive cell migration and the dissemination of tumor cells. Areas covered: In consideration of PubMed publications, the current review article specifically focuses on the clinical utility of circulating nucleosomes along with protease and caspase activities and discusses the quantification of these parameters as potential, minimally invasive assay. Expert opinion: The quantification of these circulating cell death products is a promising marker for the pathogenesis of malignant diseases and monitoring of anticancer therapies. The measurement of circulating protease activities and tumor cells in the blood may provide additional information on tumor progression and metastases.