We have made four key discoveries shedding new light on the biology of CTCs, and identified promising biomarkers for the development of an assay to predict and guide treatment of BMBC in the clinic:
- Found that CTCs recovered from clinical BMBC specimens rarely express epithelial cell adhesion molecule (EpCAM) and could not be detected by CellSearchTM (Veridex, LLC), a FDA-cleared prognostic CTC test which evaluates only CTCs which are positive for EpCAM.
- Isolated subsets of CTCs from patients with BMBC by combining technologies alternative to CellSearchTM, such as FICTION (BioViewTM) along with flow cytometry, and a highly sensitive RT-PCR employing a thermodynamically-matched primer design to identify wild type and variant gene expression. We were able to visualize, isolate, and study CTCs that CellSearchTM would never capture. These EpCAM-negative CTCs express a multitude of tumor cell traits, including markers of stemness.
- Established procedures retrieving viable CTC subsets via fluorescence-activated cell sorting which were amenable to growth in vitro and subsequent analyses.
- Defined EpCAM-negative CTCs to possess the known markers HER2/neu, EGFR, uPAR, ALDH1, cytokeratins, and CD44high/CD24low. However, and of note, we found two additional markers that are highly expressed on EpCAM-negative CTCs: Heparanase and Notch.
Our approaches are cutting-edge and include unique in vitro and in vivo models of BMBC, lentiviral delivery targeting heparanase with microRNA, small molecule HPSE inhibitors, and innovative study designs of the biology of CTCs. They emphasize the strong translational component of our programs which hold a great potential for new understandings of BMBC onset and regulation. They will provide the essential groundwork to introduce heparanase-based therapies in patients with brain metastases in general, breast cancer brain metastasis in particular. We are fully dedicated to this goal.