Role of Chemokine Receptors in Breast Cancer Metastasis

Institution: University of California, Los Angeles
Investigator(s): Brett Premack, Ph.D. -
Award Cycle: 1999 (Cycle V) Grant #: 5IB-0061 Award: $41,311
Award Type: IDEA
Research Priorities
Biology of the Breast Cell>Pathogenesis: understanding the disease

Initial Award Abstract (1999)
We need to understand more about how breast cancer cells become motile, particularly the ways that they enter and leave the lymphatic and blood vessels, which are the critical conduits to spread in the body. White blood cells are capable of moving out of the blood and lymph, and much is known of the specific cell surface proteins and soluble factors that regulate this process. These proteins and receptors are called chemokines. Although there is convincing evidence that chemokines and their cell surface receptors are involved in the growth and metastasis of some human tumors, the exact molecular nature of this involvement has yet to be elucidated. In human breast cancers, spreading to bone marrow and lung is characteristic of late stage disease in a large percentage of patients. In order to better understand this pathogenesis we will study the role of chemokines in breast cancer metastasis using molecular biology techniques and cell motility assays. Our basic premise is that because chemokines turn on the cellular machinery that produces directional migration of many cells, these same molecules may contribute to the metastasis of primary breast tumors.

To examine the possible presence and function of chemokines and their receptors in breast cancer, we will use new molecular assays (PCR-based), immunological (ELISA) techniques and physiological tools initially developed in our laboratory for the study of leukocytes. Thus, we will: (1) look for the mRNA expression of chemokines and receptors, (2) determine whether chemokine receptors are functionally coupled to calcium signaling pathways involved in breast cancer cell motility, (3) determine whether expressed chemokine receptors stimulate the migration of breast cancer cells, and (4) determine whether any of the breast cancer cell lines secrete chemokines which may function as autocrine (i.e., locally acting) motility factors. This study could uncover an autocrine motility loop, which might explain the basis for increased metastatic potential.

A real plus to our breast cancer-chemokine survey is that we will make use of a number of new anti-inflammatory and anti-viral chemokine therapeutics currently being developed in immunology research. If chemokine receptors are involved in cancer metastasis, it is quite likely that some of these newly developed drugs would also have anti-metastatic properties. One can envision a potent metastasis inhibitor based on controlling the motility of primary tumors. Such a drug could be a major new tool in the fight against breast cancer.

Final Report (2001)
Note: This grant was extended one year to complete the aims

We examined whether chemokine receptors are expressed in a panel of established human breast cell lines with a standardized RT PCR method. We used 13 receptor-specific PCR primers for both the CC and CxC classes of chemokine receptors. In the 8 cell lines examined to date, 7 express significant mRNA expression of one specific CxC chemokine receptor, namely CXCR4. Two lines also expressed very low levels of CCR1, but only high CXCR4 expression appeared to be correlated win the invading phenotypes of breast carcinoma. This finding is consistent with the recent report that CxCR4 is aIso overexpressed in glioblastoma tumor cells (J Surg Oncol 1998 Dec;69(4):239-48). We examined CxCR4 surface protein expression using two different monoclonal antibody techniques (FACS and spectroscopy). Using the MCF 7 cell line, we could show by FACS analysis that CxCR4 is expressed at the cell surface in approximately 30% of cells. Next, we tested whether the CXCR4 was functional using calcium signaling assays. We did find evidence that the receptor was active. Interestingly the CxC4R ligand, SDF-1, was able to elicit a response, while other ligands (MIP I , RANTES and MCP 1) were not active.

Thus, our preliminary results suggest that beast cancer cell lines comprise a mixed population, with significant proportion of cells expressing CxCR4 at quite high levels. One possibility is that these cells represent a motile founder phenotype with enhanced metastatic potential. We were not able to confirm this with assays, such as Matrigel invasion chambers. Thus, further work will be needed to expand and develop these observations.