Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 110, Issue 36, Pages 14598-14603Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1311333110
Keywords
protein engineering; miniprotein; tumor targeting; Hedgehog pathway
Categories
Funding
- Wallace H. Coulter Foundation
- V Foundation for Cancer Research
- James S. McDonnell Foundation
- Stanford Cancer Institute
- Stanford Center for Children's Brain Tumors at Lucile Packard Children's Hospital
- National Science Foundation
- Stanford Graduate Fellowship
- Siebel Scholars Fellowship
- Gerald J. Lieberman Fellowship
- California Institute of Regenerative Medicine
- Stanford Child Health Research Institute
- Lucile Packard Foundation for Children's Health
- Stanford CTSA [UL1 RR025744]
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Central nervous system tumors carry grave clinical prognoses due to limited effectiveness of surgical resection, radiation, and chemotherapy. Thus, improved strategies for brain tumor visualization and targeted treatment are critically needed. We demonstrate that mouse cerebellar medulloblastoma (MB) can be targeted and illuminated with a fluorescent, engineered cystine knot (knottin) peptide that binds with high affinity to alpha(v)beta(3), alpha(v)beta(5), and alpha(5)beta(1) integrin receptors. This integrin-binding knottin peptide, denoted EETI 2.5F, was evaluated as a molecular imaging probe in both orthotopic and genetic models of MB. Following tail vein injection, fluorescence arising from dye-conjugated EETI 2.5F was localized to the tumor compared with the normal surrounding brain tissue, as measured by optical imaging. The imaging signal intensity correlated with tumor volume. Due to its unique ability to bind to alpha(5)beta(1) integrin, EETI 2.5F showed superior in vivo and ex vivo brain tumor imaging contrast compared with other engineered integrin-binding knottin peptides and with c(RGDfK), a well-studied integrin-binding peptidomimetic. Next, EETI 2.5F was fused to an antibody fragment crystallizable (Fc) domain (EETI 2.5F-Fc) to determine if a larger integrin-binding protein could also target intracranial brain tumors. EETI 2.5F-Fc, conjugated to a fluorescent dye, illuminated MB following i.v. injection and was able to distribute throughout the tumor parenchyma. In contrast, brain tumor imaging signals were not detected in mice injected with EETI 2.5F proteins containing a scrambled integrin-binding sequence, demonstrating the importance of target specificity. These results highlight the potential of using EETI 2.5F and EETI 2.5-Fc as targeted molecular probes for brain tumor imaging.
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