Phosphatidylethanolamine targeting for cell death imaging in early treatment response evaluation and disease diagnosis.

Phosphatidylethanolamine (PE) is one of the most abundant phospholipids in mammalian plasma membranes. In healthy cells, PE resides predominantly in the inner leaflet of the cell membrane. In dead or dying cells on the other hand, PE is externalized to the outer leaflet of the plasma membrane. The exposure of PE on the cell surface has therefore become an attractive target for the molecular imaging of cell death using single-photon emission computed tomography (SPECT) and positron emission tomography (PET). This has motivated the development of PE-specific probes to measure cell death in vitro and non-invasively in vivo. In this review, we highlight the biological roles of PE on cell membranes, and PE exposure as a biomarker of cell death in disease processes, along with the use of PE-binding molecular probes to target PE for the characterization of cell death on a cellular and tissue level. We specifically emphasize the preclinical applications of radiolabeled duramycin for the non-invasive imaging of cell death in animal models of disease and in tumors after therapy. In addition, we discuss the clinical relevance, limitations and future perspectives of this imaging approach of cell death.