Identification of Metastasis Competent Breast Cancer Cells

Institution: La Jolla Institute for Molecular Medicine
Investigator(s): Barbara Mueller, Ph.D. - Barbara Mueller, Ph.D. -
Award Cycle: 2006 (Cycle 12) Grant #: 12IB-0096 Award: $267,567
Award Type: IDEA
Research Priorities
Biology of the Breast Cell>Pathogenesis: understanding the disease

This is a collaboration with: 12IB-0096A -

Initial Award Abstract (2006)
Metastasis to distant organs is a critical treatment challenge and a major cause of death for breast cancer patients. Yet, paradoxically, metastasis is an inefficient process and most cells in primary tumors, and even most tumor cells that disseminate from primary tumors, fail to complete the metastatic process. Tumor cells with metastatic competence are a distinct subset that expresses specific cell surface molecules/receptors involved in the multi-step process of metastasis. We hypothesize that these cell surface molecules, while critical for metastasis, are not necessarily expressed in the cells in established metastases, reminiscent of temporal, selective gene expression in other cellular differentiation processes that occur during normal development.

We propose a novel “phage display” methodology to identify the phenotype of breast cancer cells with metastatic competence. It is based on the observation that phage can enter mammalian cells by receptor-mediated processes and that phage DNA persists in infected cells for weeks. A heterogeneous cell population can be labeled at t=0 with phage displaying appropriate peptide sequence. After the cells have completed a complex multi-step process of metastasis, phage DNA encoding the ligand that enabled the phage to enter the original cell can be recovered and analyzed. The extraordinary power of this genetic tagging approach that we termed “Reaching Back in Time” (RBT) resides in its ability to capture biomarker signatures of the original cells, irrespective of whether these biomarkers are lost in differentiation. Current state-of-the-art approaches can only determine the molecular profiles of cells in established metastases.

This project will test whether the RBT approach can be used to identify a unique biomarker signature of metastasis competent breast cancer cells. Our aims are to:
• demonstrate that human breast cancer cells in culture can be tagged with phage and that subsequently phage DNA can be recovered from established metastases using phage that display a single ligand .
• use a phage-displayed peptide library to identify a panel of peptides that marks cells with metastatic competence
• validate the peptide signature identified by RBT.
This feasibility study will use human breast cancer cell lines, phage that display a single ligand (EGF) or a random peptide library, and tail vein injection as metastasis assay as well as standard cell biology and molecular biology methods.

Our goals are to understand metastasis, to discover new prognostic markers and ultimately to develop novel biological therapies that can replace or be used in less toxic combinations with existing cytotoxic therapies. This will impact breast cancer because the lack of good prognostic markers for metastatic disease leads to unnecessary treatment and the lack of effective therapies for early or established metastasis is a major challenge to the cure of patients with a poor prognosis.

Final Report (2008)
Even with recent improvements in chemo-, radio- and antibody therapies thousands of women still die each year from metastatic breast cancer. Because it is not possible to diagnose the earliest stages of metastasis, many women undergo extremely uncomfortable post surgical treatments to kill metastatic cells, should they exist. These post surgical treatments undoubtedly save lives, however, they are harmful in and of themselves, and have no medical benefit in cases in which the cancer has not spread. This research is intended to develop tools to measure a cancer cell’s ability to cause metastasis before metastasis actually occurs. Once developed these tools should prove useful in developing new more effective and less harsh treatments for early stage metastatic disease. In the near term, however, the ability to accurately assess an individuals patient’s risk for metastasis could lead to more effective use of existing treatment options.

We completed the three aims of the proposed study. Specifically, we first demonstrated the feasibility of the proposed technology in breast cancer. We then genetically labeled breast cancer cells using millions of different molecular tags using a so-called “phage peptide library.” These unique tags can enter the cancer cells; create a record of what biological molecules were present at the time of labeling, and copy that record into the cells progeny. Labeled breast cancer cells were used to generate metastasis in a well-established breast cancer model. After metastasis had occurred, we looked for markers in metastatic tumors and recovered the markers that labeled the cells that were able to give rise to these metastatic tumors. In this way we isolated 4 specific peptide markers. We are currently seeking NIH funding to validate these peptide signature as marking metastasis competent breast cancer cells.