Editorial [Hot topic: Imaging Agents for Apoptosis (Guest Editor: Wenbin Zeng)]

A number of evidences indicate apoptosis plays an important role in the pathogenesis, etiology, cancers and numerous medical disorders. Molecular imaging of apoptosis may therefore be very useful in clinical practice, assisting in diagnosis, staging and monitoring of disease, monitoring of the course of disease, or assessment of efficacy of the treatment. Several review articles, including the journal papers and books, published within last few years provide good illustration how broad these efforts made [1-7]. However, there are increasing interests and demands for the development of non-invasive imaging methodologies and strategies for the quantification of apoptosis. To quantitatively assess apoptosis would facilitate pre-clinical and clinical evaluation of novel diagnosis and therapeutics. In this regards, to design, evaluate and develop a biomarker for imaging apoptosis with corresponding molecular imaging modality will be of great challenges. Despite both the diagnosis and treatment of varied diseases benefiting from imaging of apoptosis, most new drugs are thought to induce apoptotic tumor cells or their supportive vasculatures. Therefore, imaging agents that can noninvasively monitor apoptosis in response to these new drugs could help streamline the drug development process. The opening paper of this issue by Dr. Blankenberg discusses about the existing imaging agents and modalities that are currently undergoing clinical testing and those that could be rapidly translated into humans. Dr. Cho and coauthors describe the apoptosis mechanisms and altered apoptosis regulators expression and gene mutation in lung cancer. Next three papers discuss the key aspects on the development of probes for molecular imaging of apoptosis. Dr. Aboagye and coauthors summarize the development of new apoptosis detecting probes that have the potential for bridging different stages of the evaluation process. Dr. Faust and coauthors describe recent progresses in tracer development for the molecular imaging techniques PET, SPECT and optical imaging and highlight the discussion of breakthroughs, drawbacks and methodological issues of apoptosis imaging. Dr. Zeng and coauthor concentrate the recent advance of small molecular based probes for detecting apoptosis. Followed by two papers are dealing with imaging apoptosis with Annexin V and its application in preclinical and clinical research. Dr. Wang RF provides the progresses on the studies with Annexin V on preclinical and clinical application in nuclear medicine. Dr. Yuji and coauthors are considering the apoptosis imaging with annexin A5 radio-probes, focusing on its application to the evaluation of the tumor response to chemotherapy. Dr. Wang HW and coauthors provide the updated information in cell death detection using the NADH/FAD fluorescence spectroscopy and imaging based on measurement of the intensity or lifetime of NADH or FAD fluorescence. The last paper of this issue by Dr. Zhao brings tremendous progress which has been made in applying the concept of apoptosis imaging toward diagnostic needs. I believe that this issue will successfully introduce the readers to exciting and challenging area of apoptosis imaging.