Breast Cancer Cell Binding to the Endothelium

Institution: Scripps Research Institute
Investigator(s): Brunhilde Felding, Ph.D. -
Award Cycle: 1999 (Cycle V) Grant #: 5JB-0143 Award: $326,892
Award Type: IDEAS II
Research Priorities
Biology of the Breast Cell>Pathogenesis: understanding the disease

Initial Award Abstract (1999)
The existing paradigm is that breast cancer spreads primarily via lymphatic routes. However, in advanced stages of this disease, the colonization of preferred target organs such as bone, lungs, liver and brain evidently involves the blood stream. This contributes considerably to the morbidity and mortality in human breast cancer. Therefore, this study addresses mechanisms of hematogenous (via the blood) spread of breast cancer. We plan to investigate the adhesion receptors that support attachment of breast cancer cells to the endothelium of target organs under conditions that occur in the vasculature. Our approach is unique in that it addresses critical questions of tumor spread using conditions of actual blood flow in the body combined with metastatic tumor cells isolated from patients, and it is focused on specific candidate adhesion receptors on both endothelial cells and breast cancer cells.

The specific aims of this project are to (1) analyze the attachment of human breast cancer cells to endothelial cells of target organs (e.g., lung and bone) under blood flow conditions in vitro, (2) challenge our ideas in the intact vasculature in a living mouse, and (3) focus on the adhesion receptors integrin avb3 and ICAM-1 for their combined ability to support tumor cell arrest at the endothelium using specific monoclonal antibodies as neutralizing agents. To mimic the conditions in the vasculature as closely as possible, our experimental approach uses a novel in vitro flow system, based on fluorescence and confocal microscopy. We will then use intravital microscopy to examine these processes in an intact animal. For the isolation of circulating tumor cells from breast cancer patient blood, we will use special magnetic beads for cell concentration. Our experimental hypothesis is that fibrinogen, the major clotting protein in blood, may serve to mediate breast cancer cell attachment to the endothelium by virtue of its ability to cross-link avb3 present on tumor cells with ICAM-1 present on endothelial cells.

If the planned studies are successful, we will obtain definitive information about a role of avb3 and the ICAM-1 in the arrest of metastatic breast cancer cells at the endothelium of target organs. This information may impact potential new therapeutic strategies aimed at preventing breast cancer metastasis to organs that are involved in the majority of deaths from this disease.

Final Report (2001)
The goal of this project is to understand how breast cancer spreads to organs such as bone, lungs, liver and brain. Spreading of cancer cells from the original tumor in the breast to other organs occurs through the lymph system and the blood stream. Our thinking was that breast cancer cell spreading in the blood depends is limited by the ability of the tumor cells to anchor to the lining endothelial cells in vessels of target organs. If the critical mechanisms of tumor cell-endothelial cell adhesion could be explained, then breast cancer cell spreading could ultimately be targeted and prevented.

During the funding period, we made four key observations:

1. Breast cancer cells can express a certain adhesion receptor, called integrin v 3, in both 'activated' or a 'non-activated' forms. The activated, but not the non-activated receptor strongly supports human breast cancer metastasis in a mouse model;
2. Circulating metastatic tumor cells from blood samples of breast cancer patients carry the activated form of the adhesion receptor, documenting that activated v 3 is relevant in clinical breast cancer;
3. Only the activated adhesion receptor, integrin v 3, helps breast cancer cells to anchor on layers of stimulated blood vessel cells; and
4. The activated receptor cooperates with a metalloproteinase, an enzyme that the breast cancer cells produce and which can digest matrix and tissue. Working together, the activated adhesion receptor and the enzyme help breast cancer cells to move on special matrix proteins and to digest these matrix proteins, which are found in breast tumors and target organs of breast cancer metastasis.

From these findings, we conclude that breast cancer cells, which carry integrin v 3 in a functionally activated form are malignant and capable of spreading from primary tumors to distant target organs, where they establish metastases. This identifies activated integrin v 3 as a functional marker of metastatic breast cancer cells. In future studies, we plan to generate reagents that will specifically bind to activated v 3. These may be useful diagnostics that detect metastatic cells in tissue or blood samples from breast cancer patients. Our final goal is develop the information and approach to help prevent or eradicate breast cancer metastasis.

Tumor cell-platelet interactions in metastatic disease
Index Medicus: HAEM
Authors: Felding-Habermann B
Yr: 2001 Vol: 31(Suppl) Nbr: Abs: Pg:55-58