The Role of IL-8 and its Receptors in Angiogenesis

Institution: La Jolla Institute for Molecular Medicine
Investigator(s): Ingrid Schraufstatter, M.D. -
Award Cycle: 2000 (Cycle VI) Grant #: 6JB-0060 Award: $149,699
Award Type: IDEAS II
Research Priorities
Biology of the Breast Cell>Pathogenesis: understanding the disease

Initial Award Abstract (2000)
In spite of advancement in the understanding and treatment of breast cancer, the long-term prognosis of metastatic breast cancer still remains poor. Since metastatic micro-tumors of the breast are particularly resistant to current therapies, novel strategies for their treatment are necessary. One promising novel strategy is to target the blood supply of the tumor. Both primary and metastatic breast cancer cells depend on an external blood supply for their survival. Therefore, angiogenesis is a necessary step in the development of both the primary tumor and of all metastasis originating from it. For this reason breast carcinomas produce various angiogenic factors that signal to the endothelial cells that line the blood vessels to migrate toward the tumor cells and sprout new microvessels surrounding the tumor. This proposal seeks to block critical factors involved in the growth of new blood vessels (angiogenesis) into the tumor. Our unique paradigm is that the mediators of the immune, inflammatory response may operate in breast cancer angiogenesis.

It is known that interleukin-8 (IL-8) is produced by breast cancer cells, and that IL-8 is angiogenic. However, IL-8 is better known for its role in inflammatory diseases, where it attracts white blood cells into an area of tissue injury. White blood cells express two kinds of IL-8 receptors, called CXCR1, which mediates white cell migration, and CXCR2, whose function is poorly understood. We recently showed that endothelial cells in culture respond to IL-8, that the CXCR1 is activated briefly, and that CXCR2 for prolonged periods of time. Thus, our BCRP-funded project will study the possible stimulation of breast cancer angiogensis via the IL-8 produced by the cancer cells and its stimulation of nearby endothelial cells. We plan to utilize inhibitory antibodies specific to the two IL-8 receptors and inhibitors to IL-8 itself that interfere with the endothelial cell response. We will gain insight into whether the IL-8 system is present in breast cancer angiogenesis, and which of the two IL-8 receptors is involved.

The role of interleukins, such as IL-8, and chemokine receptors (CXCR1 and 2) has been postulated in cancer growth, but no clear connection has been established. Our results will open the possibility of a novel approach for combating metastatic breast cancer.

Final Report (2001)
Note: The following abstract for this grant was submitted for the cBCRP 2001 Symposium

Novel approaches are needed for the development of therapies that provide better survival and quality of life for those afflicted with advanced metastatic breast cancer. One promising new strategy is the development of anti-angiogenic treatments, which serve to block the blood supply to the tumor and prevent the escape of tumor cells via the blood and lymph. But even with the increased interest in angiogenesis, there remain some known angiogenic factors that have been largely overlooked. Our interest is in the mediators of the immune, inflammatory response that may operate in breast cancer angiogenesis, particularly the IL-8 family of chemokines. In this respect, high concentrations of IL-8 and gro-a have been reported in patient samples and have been associated with poor outcome in various cancers. Furthermore, in animal models blockade of IL-8 was found to inhibit angiogenesis and the growth and metastasis of certain tumors

Since angiogenesis is a key element for breast cancer growth, and since it is known that various breast cancer cells produce IL-8 and gro-a, it is important to determine the effects of IL-8-like chemokines on the angiogenic response in a well-defined in vitro system. However, associations of chemokines and angiogenesis will not be simple, since rodents, the animals of choice, show chemokine and chemokine receptor usage quite different from humans.

We recently found that microvascular endothelial cells (HMECs) which are the primary responding cells in angiogenesis express the two known IL-8 receptors (CXCR1 and CXCR2). During the first 1-2 minutes following the addition of IL-8, actin polymerization in these cells is due to activation of both IL8 receptors. However, only CXCR2 activation lasts for more than 30 min and leads to cell retraction, a behavior shared with several other angiogenic factors. The CXCR1-mediated response was blocked by compounds which inhibit the rho cascade. In contrast the CXCR2 mediated response was blocked by pertussis toxin, which prevents Gi activity, PP2, an inhibitor of src kinase and AG1478, which blocks the epidermal growth factor (EGF)-receptor. Furthermore we could show that stimulation with IL-8 or gro-a induced phosphorylation of the EGF receptor. IL-8 induced migration of HMECs - a prerequisite for angiogenesis in vivo - was almost entirely mediated by the CXCR2 and could similarly be prevented by inhibition of src kinase or of the EGF receptor.

While these experiments are not yet complete, they strongly suggest that blockade of IL-8 signaling steps has therapeutic potential. Importantly, inhibitors of EGF receptor function, which are currently in clinical trials in breast cancer patients, may not only affect the growth of these tumor directly, but may in addition prevent chemokine-dependent angiogenesis by blocking IL-8-mediated transactivation of endothelial cell EGF receptors. Angiogenesis involves many growth factors and processes not yet understood, and cancer cells are quite adept at acquiring alternate processes to circumvent the regulation seen in normal cells. Thus, the role IL-8 deserves more consideration in any combination therapy directed at angiogenesis.