Stability of Nucleosomal DNA Fragments in Serum

Abstract

Circulating DNA is increased in various benign and malignant pathologic conditions, including cancers, sepsis, and graft-vs-host and autoimmune diseases as well as after trauma or ischemia (1)(2)(3)(4)(5)(6)(7)(8). Changes in circulating DNA correlate with the response to antitumor therapy and with tumor recurrence (9)(10)(11). Furthermore, DNA concentration reportedly has predictive and prognostic relevance in cancer (11)(12). Despite the nonspecific nature of circulating DNA, it might have considerable potential for monitoring cancer and management of therapy (9)(10)(11)(12). In serum and plasma, DNA is thought to exist predominantly as mono- and oligonucleosomes (13)(14), which are formed by a core particle of a double set of the histones H2A, H2B, H3, and H4 wrapped by 146 bp of DNA on the outside (15). By this composition they seem to be protected against rapid digestion by endonucleases (16). Circulating nucleosomes can be quantified by real-time PCR of the DNA but also by immunologic assays, which are particularly well suited for serial measurements (17). Achieving reliable results in these immunochemical assays requires adherence to a strict preanalytical protocol that includes careful venipuncture, centrifugation of the sample within 1–2 h after venipuncture, addition of EDTA for stabilization of nucleosomes, and storage at −70 °C …