Molecular Imaging of Phosphorylation Events for Drug Development

Purpose  Protein phosphorylation mediated by protein kinases controls numerous cellular processes. A genetically encoded, generalizable split firefly luciferase (FL)-assisted complementation system was developed for noninvasive monitoring phosphorylation events and efficacies of kinase inhibitors in cell culture and in small living subjects by optical bioluminescence imaging. Procedures  An Akt sensor (AST) was constructed to monitor Akt phosphorylation and the effect of different PI-3K and Akt inhibitors. Specificity of AST was determined using a non-phosphorylable mutant sensor containing an alanine substitution (ASA). Results  The PI-3K inhibitor LY294002 and Akt kinase inhibitor perifosine led to temporal- and dose-dependent increases in complemented FL activities in 293T human kidney cancer cells stably expressing AST (293T/AST) but not in 293T/ASA cells. Inhibition of endogenous Akt phosphorylation and kinase activities by perifosine also correlated with increase in complemented FL activities in 293T/AST cells but not in 293T/ASA cells. Treatment of nude mice bearing 293T/AST xenografts with perifosine led to a 2-fold increase in complemented FL activities compared to that of 293T/ASA xenografts. Our system was used to screen a small chemical library for novel modulators of Akt kinase activity. Conclusion  This generalizable approach for noninvasive monitoring of phosphorylation events will accelerate the discovery and validation of novel kinase inhibitors and modulators of phosphorylation events.     

Positron Emission Tomography Imaging of Small Animals in Anticancer Drug Development

Positron emission tomography (PET) imaging of small animals enables researchers to bridge the gap between in vitro science and in vivo human studies. The imaging paradigm can be established and refined in animals before implementation in humans and image data related to ex vivo assays of biological activity. Small animal PET (saPET) imaging enables assessment of baseline focal pathophysiology, pharmacokinetics, biological target modulation and the efficacy of novel drugs. The potential and challenge of this technology as applied to anticancer drug development is discussed here.     

Drug Design and Discovery: Translational Biomedical Science Varies Among Countries

Drug design and discovery is an innovation process that translates the outcomes of fundamental biomedical research into therapeutics that are ultimately made available to people with medical disorders in many countries throughout the world. To identify which nations succeed, exceed, or fail at the drug design/discovery endeavor—more specifically, which countries, within the context of their national size and wealth, are “pulling their weight” when it comes to developing medications targeting the myriad of diseases that afflict humankind—we compiled and analyzed a comprehensive survey of all new drugs (small molecular entities and biologics) approved annually throughout the world over the 20‐year period from 1991 to 2010. Based upon this analysis, we have devised prediction algorithms to ascertain which countries are successful (or not) in contributing to the worldwide need for effective new therapeutics.     

超声微泡及其在分子影像诊断和靶向治疗中的应用

超声微泡是一种超声造影剂,利用超声微泡声学特征和靶向功能可提高超声分子诊断的灵敏性和特异性,利用其药物载体和释放功能可进行靶向药物治疗。现对超声微泡及其在分子影像诊断和靶向治疗中的应用进展作一综述。     

Noninvasive Imaging of Cardiac Gene Expression and Its Future Implications for Molecular Therapy

Innovative approaches for cardiovascular molecular therapy are rapidly evolving, and translational efforts from experimental to clinical application are increasing. Gene and cell therapy hold promise for treatment of heart disease, but despite progress, some basic principles are still under development. Open issues are, e.g., related to the optimal method for delivery, to therapeutic efficacy, to time course and magnitude of gene expression, and to the fate of transplanted cells in target and remote areas. The use of reporter genes and labeled reporter probes for noninvasive imaging provides the methodology to address these questions by assessment of location, magnitude, and persistence of transgene expression in the heart and the whole body. Coexpression of a reporter gene allows for indirect imaging of the expression of a therapeutic gene of choice. Furthermore, reporter genes can be transferred to stem cells prior to transplantation for serial monitoring of cell viability using gene product imaging. Additionally, functional effects of therapy on the tissue level can be identified using established imaging approaches to determine blood flow, metabolism, innervation, or cell death. Measures of transgene expression can then be linked to physiologic effects and will refine the understanding of basic therapeutic mechanisms. Noninvasive gene-targeted imaging will thus enhance the determination of therapeutic effects in cardiovascular molecular therapy in the future.