Co-Targeting the Notch and EphB4 Receptors in Breast Cancer

Institution: University of Southern California
Investigator(s): Debasish Tripathy, M.D. -
Award Cycle: 2012 (Cycle 18) Grant #: 18IB-0048 Award: $243,362
Award Type: IDEA
Research Priorities
Detection, Prognosis and Treatment>Innovative Treatment Modalities: search for a cure

Initial Award Abstract (2012)

Currently available breast cancer therapies do not prevent all recurrences after surgery for early stage breast cancer and are not curative in advanced breast cancer, with virtually all patients developing resistance and relapsing over time. Residual breast cancer cells that are resistant to standard therapy are responsible for this problem and we are beginning to understand more about the biological pathways that promote these residual breast cancer cells and the environment within the body that supports them.

Two types of cell receptors, called EphB4 and Notch, “drive” resistant residual cells and their supportive microenvironment. EphB4 and Notch can be targeted with novel biological agents that we have developed. The ephrin family of receptor kinases appears to be involved in the development of the nervous and vascular systems as well as in the regulation of cell shape and movement. The Notch receptor pathway is a key mediator of stem cell maintenance, with several known ligands, of which at least two are tumor and tumor vasculature specific. Interruption of Notch inhibits growth and stromal/tumor interactions in several tumor types and various Notch inhibitors are in early clinical trials. In this project we will test the effect of blocking each and both of the EphB4 and Notch receptor pathways. These pathways are involved in tumor blood vessel formation and the maintenance of immature cancer stem cells that have the ability to repopulate a tumor after response to standard therapy. The EphB4 pathway inhibitor is a fragment of the EphB4 receptor linked to albumin (sEph4-HSA) so that it can block the activation of EphB4 when it binds to stimulator binding proteins call the ligands. The Notch pathway inhibitor is an antibody to two of the ligands (Dll-1 and Dll-4) (MAb61B) that bind and activate Notch, that essentially shuts down the activity of Notch and inhibits both blood vessel formation and the signal to keep stem cells in their undifferentiated state. Human breast cancer cell lines that represent the estrogen and HER2 receptor spectrum will be tested with either of the inhibitors alone and then in combination with both inhibitors and finally, with the addition of chemotherapy. This will be carried out with breast cells in plastic dishes as well as tumors grown in mice. Specific biomarkers will be analyzed on tumor cells and animal tumors to verify that the targets are being modulated and growth is suppressed.

This project is based on elegant and rather new findings on the biology of stem cells and the tumor microenvironment, particularly tumor-related blood vessels. The ultimate of this line of investigation is to develop a new class of therapies that targets residual resistant breast cancer and lead to much better results, possibly even cures in the metastatic setting, when added to standard breast cancer medical treatments.

Final Report (2014)

Patients with breast cancer are not curable in advanced disease, and triple receptor negative (estrogen, progesterone and HER2) cases are particularly aggressive and only response transiently to chemotherapy. Our proposal is focusing on the concept of co-targeting two pathways, EphB4 and Notch, that are critical to the survival and proliferation of breast cancer with the hypothesis that single pathway or pathway component blockade even when initially successful, is followed by biological and clinical resistance due to redundant pathways in genomically complex cancer centers. Simultaneous blockade of dual (or more than two) pathways may result in a “synthetic lethal” effect, whereby a much smaller fraction of residual cells after such therapy could eventually lead to a cure of metastatic disease, as it has in other malignancies such as testicular cancer and lymphoma. In these other neoplasms, however, the lesser degree genomic aberrations has allowed for chemotherapy regimens to be curative, whereas in much heartier solid epithelial cancers such as breast cancer, therapy will also need to include biologically targeted treatments along with chemotherapy.

Over the course of this project, we developed dose response curves for of several chemotherapeutic agents with diverse receptor subtype breast cancer cell lines and in combination with HER2 and EphB4 inhibition. After testing several cell lines and chemotherapy agents as proposed, we focused on triple negative cell lines and cisplatin, given the benefit of this agent seen clinically in TNBC. We demonstrated synergy of EphB4 blockade using the EphB4 targeting soluble human serum albumin-stabilized peptide, sEphB4-HSA (sB4) in combination with cisplatin. These findings are being presented at the upcoming 2014 AACR meeting in San Diego (Yang- Kolodji G, et al, AACR Abstract #2601). One barrier that was appreciated with our in vitro experiments was that the lack of stromal interactions involved with both the EphB4 and Notch pathways (to a greater extent with Notch) may not inform us properly of co-targeting, so we completed the EphB4 and Notch experiments in an orthotopic mouse model as proposed using MDA-MB-231 triple negative breast cancer cell lines. We showed that both EphB4 and Notch targeting show inhibit TNBC (MDA-MB-231) xenografts growth, but this did not appear synergistic. Studies co-targeting EphB4 and Notch with chemotherapy are ongoing using sEphB4-HSA and an antibody to tumor and tumor-vascular specific Notch ligands DLL1 and DLL4 as well as Notch receptor antibody.