Magnetic resonance imaging (MRI), the most widely used imaging modality for soft tissues, in general lacks sufficient sensitivity for molecular imaging of biological processes associated with cancer. Although Gd3+based contrast agents are widely used in clinical MRI as non-specific extracellular agents, new approaches need to be developed to bring MRI into competition with optical and nuclear methods for molecular imaging of cancer. A new class of responsive paramagnetic chemical exchange saturation transfer (PARACEST) agent has been designed as highly specific reporters of tumor physiology and metabolism. Although several groups have recognized their potential importance as molecular imaging agents, their practical application to tumor imaging has not been realized at this point largely because of background interference from the inherent magnetization transfer (MT) signal from all tissues. In this project, we propose a practical solution to eliminate this background MT signal so the inherent molecular specificity of these reporter molecules can be fully realized in vivo. A novel molecular design is proposed that will yield a platform of responsive MRI agents for discriminating regions of low pH, hypoxia and reactive oxygen species (ROS) in tumors using standard clinical MRI scanners. These three indices, pH, hypoxia and excess ROS, are all hallmarks of rapidly proliferating cells so having a stable of responsive agents capable of sensing these tissue biomarkers would be extremely valuable for monitoring tumor metabolism. Our objective is to implement all three responsive agents in vivo in animal tumors using agent concentrations that would be considered acceptable for human use and without interference from tissue MT signals by the end of this 5 year project. A second newer class of probes called T2exch agents will be tested and evaluated as reporters of cancer-related protease activities by MRI. If successful, the agents developed in this project will make MRI competitive as an effective molecular imaging tool for cancer diagnosis.
Magnetic resonance imaging (MRI) is widely used to detect tumors but provides little or no information about tumor biology, tumor metabolism or tumor microenvironment. This project involves developing a new class of responsive imaging agents to act as highly specific reporters of tumor physiology and metabolism. A low extracellular pH, hypoxia (low oxygen), and the presence of reactive oxygen species (ROS) are all hallmarks of rapidly proliferating cells so having a stable of responsive MRI agents capable of sensing these tissue biomarkers would be extremely valuable for monitoring tumor biology.
|Fernando, W Shirangi; Martins, AndrÃ© F; Zhao, Piyu et al. (2016) Breaking the Barrier to Slow Water Exchange Rates for Optimal Magnetic Resonance Detection of paraCEST Agents. Inorg Chem 55:3007-14|
|Wu, Yunkou; Zhang, Shanrong; Soesbe, Todd C et al. (2016) pH imaging of mouse kidneys in vivo using a frequency-dependent paraCEST agent. Magn Reson Med 75:2432-41|
|Kumas, Cemile; Fernando, W Shirangi; Zhao, Piyu et al. (2016) Unexpected Changes in the Population of Coordination Isomers for the Lanthanide Ion Complexes of DOTMA-Tetraglycinate. Inorg Chem 55:9297-305|
|Funk, Alexander M; Clavijo Jordan, Veronica; Sherry, A Dean et al. (2016) Oxidative Conversion of a Europium(II)-Based T1 Agent into a Europium(III)-Based paraCEST Agent that can be Detected In Vivo by Magnetic Resonance Imaging. Angew Chem Int Ed Engl 55:5024-7|
|Wang, Xiaojing; Wu, Yunkou; Soesbe, Todd C et al. (2015) A pH-Responsive MRI Agent that Can Be Activated Beyond the Tissue Magnetization Transfer Window. Angew Chem Int Ed Engl 54:8662-4|
|Wu, Yunkou; Hao, Guiyang; Ramezani, Saleh et al. (2015) [(68) Ga]-HP-DO3A-nitroimidazole: a promising agent for PET detection of tumor hypoxia. Contrast Media Mol Imaging 10:465-72|
|Kumar, Amit; Zhang, Shanrong; Hao, Guiyang et al. (2015) Molecular platform for design and synthesis of targeted dual-modality imaging probes. Bioconjug Chem 26:549-58|
|De LeÃ³n-RodrÃguez, Luis M; Martins, AndrÃ© F; Pinho, Marco C et al. (2015) Basic MR relaxation mechanisms and contrast agent design. J Magn Reson Imaging 42:545-65|
|Sagiyama, Koji; Mashimo, Tomoyuki; Togao, Osamu et al. (2014) In vivo chemical exchange saturation transfer imaging allows early detection of a therapeutic response in glioblastoma. Proc Natl Acad Sci U S A 111:4542-7|
|Mani, Tomoyasu; Opina, Ana Christina L; Zhao, Piyu et al. (2014) The stereochemistry of amide side chains containing carboxyl groups influences water exchange rates in EuDOTA-tetraamide complexes. J Biol Inorg Chem 19:161-71|
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