PROJECT 1: The broad, long-term objectives of this research plan are to develop an integrated opticalmolecular imaging strategy that uses fluorescence peptides as probes to target the presence of premalignant(dysplastic) tissue in vivo. Macroscopic and microscopic fluorescence instruments are developedas complementary imaging methods for peptide detection. This methodology can be used for monitoringbiomarker expression in small animal models and for the early detection of cancer in human patients undergoingscreening. In this application, the colonic adenoma is used as a model for dysplasia.
The specific aims are to1) identify 5 candidate peptides using techniques of phage display for biopanning against cultured cells andfreshly excised specimens of human colonic mucosa, 2) develop new optical imaging instrumentation using thedual axes confocal architecture to visualize the tissue microarchitecture relevant to peptide binding, and 3)validate preferential peptide binding to dysplasia in vivo in a genetically engineered mouse that forms polyps inthe distal colon by somatic activation of Cre-recombinase and in human subjects undergoing routine screeningcolonoscopy. Peptides are chosen for development as probes because their high diversity and small sizecan provide high affinity binding with deep tissue penetration, and their low risk of immunogenicity andtoxicity facilitate translation for use in the clinic. Phage display is a powerful combinatorial technique thatprovides an unbiased approach for identifying unique peptides that exhibit affinity binding to dysplasticmucosa as is well suited to accommodate subtle changes associated with the in vivo microenvironment. Thedual axes confocal architecture provides an instrument that can achieve sub-cellular resolution with longworking distance and overcomes the effects of tissue scattering using off-axis fluorescence collection.Moreover, this design can be scaled down in size for endoscope compatibility. A 5 mm diameter instrumentpackage is sufficiently small to pass through a 6 mm diameter instrument channel in a therapeutic endoscope.High speed scanning is performed with a tiny MEMS (micro-electro-mechanical systems) mirror that collectsoptical sections at a sufficient frame rate for generating 3D volumetric images. The candidate peptides will betopically applied to colonic adenomas and surrounding normal appearing mucosa followed by macroscopicfluorescence imaging to localize regions of increased peptide binding for subsequent microscopic fluorescenceimaging to assess the spatial distribution of peptide binding within the dysplastic crypt microarchitecture.Public Health: The proposed studies will result in the development of novel optical imaging probes andinstruments that can be evaluated in pre-clinical models as well as translated to the clinic as practicalscreening tool for the early detection of cancer in hollow organs.
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