Cancer and other disease biomarkers and targets may provide key diagnostic, prognostic and therapeutic opportunities including clinical trial surrogates and screens for patient treatment assignment. Blood and tissues are complex with extensive molecular diversity over a wide concentration range that creates discovery challenges for proteomic analysis. Candidate biomarkers require strict validation that is laborious and expensive. Noninvasive imaging provides objective validation for diagnostic and therapeutic targets in vivo. Drugs, gene vectors, and nanoparticles may benefit greatly from improved in vivo delivery through homing to specific disease biomarkers. Yet in vivo barriers limit access to most disease targets including cancer. Our evolving discovery and validation strategies that are intended to overcome these hurdles will be discussed.

We have developed novel systems biology approaches that integrate nanotechnology-based subcellular fractionation, quantitative organellar & subtractive proteomics, bioinformatic interrogation, antibody generation, expression profiling, and various in vivo imaging modalities to quickly identify and validate candidates for pre-clinical and clinical testing. Analysis of rodent and human tumor samples have been compared to focus on clinical meaningful targets and to understand model relevance to human disease. Tissue and tumor microenvironmental influences on endothelial cell expression are extensive. We have developed quantitative proteomic analysis using a new spectral intensity index to identify 300+ proteins concentrated in caveolae; many of which are confirmed by immuno-electron microscopy. Bioinformatic analysis of this subproteome ascribes new functional attributes to the caveolae.

Examples of new targets will be presented along with validation studies using antibodies and molecular imaging to demonstrate specific targeting in vivo. Novel targets in caveolae enable antibodies to penetrate deep into solid tumors and single organs and were utilized to improve tissue-specific imaging and treatment. Our recent findings reveal that caveolae not only express tissue-specific proteins but also function to rapidly and actively pump specifically targeted antibodies and nanoparticles across the endothelial cell barrier and into the tissue interstitium. Such pervasive access improves the efficacy of radioimmunotherapy in destroying both stromal and tumor cells and in treating a wide variety of solid tumors. Lastly, functional knockout of newly identified tumor-induced endothelial proteins can greatly affect tumor growth, metastasis, and angiogenesis. These studies illustrate the benefit and power of focused organellar proteomic mapping in vivo. This type of "proteomic imaging of the vascular biomarker space including its in vivo accessible target space and transvascular pumping space" may bode well for application to cancer and many other diseases.

Dr. Jan E. Schnitzer is the Scientific Director of the Sidney Kimmel Cancer Center, located in San Diego. The Sidney Kimmel Cancer Center is an independent, nonprofit research institution dedicated to the development and advancement of biomedical research to eliminate cancer. The SKCC was recently awarded a $14.4 million Program Project Grant, over five years, from the National Cancer Institute, with Dr. Schnitzer as the Principal Investigator of this grant.

Dr. Schnitzer's research has identified "zip code" molecules for cancer that allow drugs to be "mailed" directly to solid tumors via their blood vessels. His lab discovered several years ago techniques to purify specific small parts of cells and tissue that are directly in contact with circulating blood and mediate transport into the tissue.

More information available at
http://nano.cancer.gov/about_alliance/bios_partnerships.asp#Schnitzer.

WALS.