C12412: New Reporter System for CEST MRI
Novelty: Novel reporter system for chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) without paramagnetic metal substrates.
Value Proposition: Among the clinically applied 3D imaging modalities, MRI has the highest resolution and is therefore the preferred method for detection of cellular gene expression. However, because of the low sensitivity of MRI, few reporter gene systems exist. This invention comprises a new class of reporter genes for MRI that does not employ paramagnetic metal substrates but rather relies on the contrast mechanism of CEST. CEST is a new approach for generating MRI contrast that allows monitoring of cell properties in vivo. Other advantages include:
• Allows unlimited real-time monitoring of rapidly dividing cells
• Dead cells don’t produce confounding artifacts
• Monitor and evaluate the efficiency of gene and cell therapy
• Used to label and track the biodistribution and migration of mammalian cells, including hematopoietic cells, stem cells, and tumor cells
• Can be applied in developmental studies of transgenic mice
• Act as a reporter for activation of a specific promoter
Technical Details: Johns Hopkins researchers have developed two reporter genes systems using synthetic nucleosides that generate high CEST contrast upon phosphorylation by either (1) the herpes simplex virus type 1 thymidine kinase (HSV1-TK) or (2) the Drosophila deoxyribonucleoside kinase (Dm-Dm-dNK). The formation of phosphorylated probe by the recombinant kinase enzyme results in accumulation of the probe selectively in the cytoplasm of the kinase expressing cells, since its negative charge prevents cellular export. The NH proton from the nucleoside probe generates CEST contrast when irradiated at a specific off resonance radio-frequency (RF). Thus, the synthetic fluorescent probe can be used for monitoring the reporter gene expression with CEST MRI. Each system has a distinctive advantage: (1) The HSV1-TK is already under evaluation for gene therapy as well as imaging in the clinic. (2) The imaging probe for the Dm-dNK is also fluorescent, thus allows Fluorescence Activated Cell Sorting (FACS) of enzyme expressing cells prior to cell transplantation. This feature is highly important for therapeutic/stem cell transplantation where enrichment of specific cell population is desired.
Looking for Partners: To develop & commercialize the technology as a reporter gene system for MRI.
Patent Status: Pending US Application US-2016-0082133
Data Availability: Proof-of-concept in mammalian cells
Publications/Associated Cases: Molecular & Cellular Imaging Poster 1852 C04616 J Am Chem Soc. 2013 Jan 30;135(4):1617-24 Nat Protoc. 2013 Dec;8(12):2380-91
