139th National Cancer Advisory Board
than a meter as in commercial spectrometers. Based on such a device, one could build a bench-top kinase evaluator that could yield a diagnosis or drug response profile within 1 hour after obtaining a blood specimen.
IMAT Facilitates Technology Exploration To Advance Clinical Translation—Dr. Jan Schnitzer
Dr. Schnitzer described the use of a large-scale systems biology approach to find new targets that are easily accessible to antibodies for immediate interaction with tumor blood vessels and for penetration into the tumors. Delivery is a key problem in cancer imaging and targeted therapy. Poor delivery can be limiting because of in vivo barriers as well as poor targeting and access to tumor cell surface target proteins. Small molecules present an opposite problem, in that access is easy throughout the whole body, and is not limited to tumors. Imaging provides a way to look noninvasively for biomarkers and determine what is happening with the delivery of therapeutic agents. The need is for accessible new targets and ways to target and penetrate solid tumors.
Many powerful genomic and proteomic technologies exist that can analyze more than 10,000 genes and gene products in a sample all at once. In defining which ones can be targeted, however, there is a dilemma around how to choose and validate the meaningful few accessible targets when there are thousands of candidates. The reduction of data complexity requires new analytical approaches that focus the technology on improving the rapidity of discovery and validation.
A hypothesis-driven analytical approach was used to reduce the complexity by asking key biological questions to focus on the power of global identification technologies. The goal is to identify new targets that are accessible to biological agents for tissue-specific imaging, delivery, and therapy in vivo. The question posed was which part of the tissue is inherently and fully accessible to agents (Abs) in the blood and the answer was the vascular endothelium. Based on this, the working hypothesis was that the tissue and disease microenvironment modulates EC phenotype and molecular expression. It was unclear whether EC proteins with sufficient tissue-specificity existed.
Dr. Schnitzer displayed a picture of an electron micrograph of a red blood cell in a micro vessel and directed attention to the endothelium, which can be isolated with caveolae from the remainder of the tissue through a nanotechnology coding procedure. This process has occurred in multiple species, multiple organs, and solid tumors through the IMAT Program. The first draft of the rat endothelial cell proteome is now complete with about 7,000 total proteins identified, and about 1,800 non-redundant proteins identified in the plasma membranes isolated from each of these tissues. Approximately 3 to 5 percent are unique to the tissue, and about 200 proteins were found to be concentrated in the caveolae. Incorporating a high level of QC analysis on the samples to eliminate false positives, membrane isolations were performed, and both new and known angiogenic marker proteins were discovered.
Dr. Schnitzer mentioned that annexin A1 was found to be expressed as a 34 kilo Dalton protein on the surface of the endothelium in the tumors but not found expressed in other tissues of the body by proteomics as well as by Western analysis. A series of antibodies were made that were specific only to annexin A1 and injected into a rat tail vein, along with very low doses of radioactivity; within 3 to 4 hours after the injection, it was seen through spectrometer imaging to accumulate in the tissues. In addition, 80 to 90 percent of the animals that were injected with the targeting antibody survived, whereas the control animals died within 5 days. This also was found to be expressed in the micro vessels of a variety of human tumors such as breast, lung, liver, gastrointestinal, prostate, brain, and ovary tumors.
Research conducted during the past 2 years, but not yet published, has focused on the caveolae as a means to target transcytosis by the caveolae to cross the normally restricted barrier and penetrate into