Targeting Breast Cancer Blood Vessels

Institution: Sidney Kimmel Cancer Center
Investigator(s): Jan Schnitzer, M.D. -
Award Cycle: 1999 (Cycle V) Grant #: 5JB-0012 Award: $363,905
Award Type: IDEAS II
Research Priorities
Biology of the Breast Cell>Pathogenesis: understanding the disease



Initial Award Abstract (1999)
Breast cancer cells are 'hidden' behind the normal cells in the body, and it is difficult to directly target them in clinical settings. This thin barrier between the blood and the tumor is composed of endothelial cells, which serve to supply the tumor with nourishment and they later become a convenient avenue to spread in the body. It is appreciated that the tumor endothelial cells are different from normal vascular endothelial cells, but we know little about their specific proteins. Our interest is to gain more information about the tumor blood vessels, and use this information to generate monoclonal antibodies for immunotherapy. This approach would target the luminal surface (i.e., side of the cell facing the blood) of endothelial cells that feed tumor cells. Thus, our eventual strategy for immunotherapy of breast carcinomas is to target cytotoxic agents to the endothelial cells lining the tumor blood vessels, thus removing the tumor's blood supply

Proteins at the luminal surface of the endothelium from normal tissue and from tumors of rat mammary carcinoma cells will be identified and compared by utilizing a novel membrane-isolation scheme that selectively isolates luminal endothelial cell plasma membranes from cancerous tissue. The proteins in these membrane fractions will be comparatively analyzed and characterized to create a very useful molecular map of the vascular endothelial cell surface. So far, in our preliminary studies, we have found several proteins selectively associated with the tumor endothelium. Specific monoclonal antibodies will be produced to these tumor endothelial proteins in order to target the vasculature of the tumor. Proteins of interest will also be purified for amino acid analysis to determine their identity. Our plan is to find numerous tumor-specific endothelial proteins that are not found in normal tissues. We will collect and assemble this information into a vascular endothelial cell proteonomic (VEP) map, which can be likened to either a library or database of potentially useful molecular targets for breast cancer immunotherapy. Finally, those antibodies found to be specific for the tumor endothelium will be tested in animal models to see if they are effective in treating experimental breast cancer.

Our experiments in this study are focused on the primary tumor, but we plan to extend our work to target the critical tumor vessels in distant sites of metastasis (e.g., lung). Thus, the potential of the VEP map and specific targeting antibodies will be the ability to use immunotherapy for advanced metastatic disease, which is usually resistant to current therapy options.


Final Report (2001)
Introduction. One longstanding approach to cancer therapy has been to create antibody probes to direct drug therapy specifically to tumor cells. These "magic bullets" have met with limited success in the treatment patients with solid tumors including breast cancer. When injected into the blood stream, these drugs do not get adequate access to tumor cells because they cannot effectively overcome formidable barriers, including the blood vessel wall. This problem may be solved by altering the "bull's eye" to target the readily accessible endothelial cells lining the tumor blood vessels. The goal of this vascular targeting strategy is destruction of the tumor by rapid and selective destruction of the vasculature supplying the tumor. Unfortunately, the identity of the pathologically induced targets on the tumor endothelium remains unknown. The primary goal of this proposal was to identify accessible tumor vascular targets in breast adenocarcinomas for use as diagnostic probes as well as in targeting therapies specifically to the primary tumor and, possibly, its metastases to increase the drug’s effectiveness while decreasing harmful side effects.

Topics addressed. This project aimed to discover novel breast tumor vascular targets, that may be useful in the treatment of breast cancer, by using a new technology that allows direct analysis of the vascular endothelial cell surface membrane as it exists in its native state in the tumor tissue. To this end, we proposed the following specific aims: 1) To create molecular maps of the vascular endothelial cell surface as it exists in breast adenocarcinoma tumors; 2) To generate and characterize monoclonal antibodies specific for molecules associated with the tumor vascular endothelium; and 3) To test the ability of developed antibodies to target specifically the tumor vascular endothelium in tumors in an animal model.

Progress toward specific aims. Using patented novel techniques to isolate luminal endothelial cell membranes from normal and tumor-bearing tissues, we investigated the molecular heterogeneity between the vasculature of normal and metastatic breast adenocarcinoma tissue. Comparative molecular mapping of these membranes identified differences in protein expression between the normal and diseased tissue. Antibodies made to these proteins showed tumor specificity by a variety of criteria as well as the ability to specifically target tumor tissue when injected into the bloodstream.

Future direction and impact. Once useful target sites are found and antibodies produced that specifically target them, then translation into developing curative immunotherapies is the logical next step. Using the targets identified in this study, the improved vascular targeting strategy described in this proposal may provide both diagnostic and therapeutic tools, especially for inoperable metastatic disease. Such probes may also help in the early detection of these lesions and in assessing disease progression after treatment which will be helpful in determining patient prognosis. Our first experiments examining tumor targeting are encouraging. We plan to continue to characterize and test our new antibodies for their utility in tumor targeting in preclinical animal models and then begin testing promising candidates in humans.

Proteonomic Mapping of Angiogenesis-induced Targets at the Endothelial Cell Surface and Caveolae In Vivo
Periodical:FASEB Journal
Index Medicus: FASEB J
Authors: Kumer JC, Oh P, and Schnitzer JE
Yr: 2000 Vol: 14 Nbr: Abs: A20 Pg:

Tumor Vascular Targeting of Caveolae
Periodical:Proceedings of the American Association for Cancer Research
Index Medicus: Proc Am Assoc Cancer Res
Authors: Oh P, Czarny M, Huflejt M, and Schnitzer JE
Yr: 2001 Vol: 42 Nbr: Abs: 4435 Pg:825

Tumor Angiogenesis Alters Caveolae: Accessible Targets for Therapy
Periodical:Proceedings of the American Association for Cancer Research
Index Medicus: Proc Am Assoc Cancer Res
Authors: Oh P, Kumer JC, and Schitzer JE
Yr: 2000 Vol: 41 Nbr: Abs: 423 Pg:66

Vascular Proteonomics: Molecular Mapping of the Endothelial Cell Surface In Vivo
Periodical:Proceedings of the American Association for Cancer Research
Index Medicus: Proc Am Assoc Cancer Res
Authors: Kumer JC, Oh P, Stevens A, and Schnitzer JE
Yr: 2000 Vol: 14 Nbr: Abs: 423 Pg:86-87

Vascular Proteonomics: Identifying Accessible Tieesu- and Tumor-Specific Vascular Targets In Vivo
Periodical:FASEB Journal
Index Medicus: FASEB J
Authors: Oh P, Kumer J, and Schnitzer JE
Yr: 2001 Vol: 15 Nbr: 4 Abs: A484 Pg:

Angiogenic Vascular Targets in Caveolae of Human and Rat Tumors
Periodical:FASEB Journal
Index Medicus: FASEB J
Authors: Oh P and Schnitzer JE
Yr: 2001 Vol: 15 Nbr: Abs: A583 Pg: