Abstract 1467: Development of a HER2-based GEDI microfluidic device for the molecular characterization of CTCs from metastatic breast cancer patients.

Microtubule targeting drugs (MTDs) constitute the mainstay of the most active chemotherapy regimens against breast cancer (BC) and have been standard therapy for locally advanced and metastatic disease for the last 20 years. However, metastatic BC (MBC) is still incurable mainly because of acquired drug resistance. The molecular basis of clinical drug resistance is not well understood which together with the lack of predictive biomarkers in the clinical setting prevents us from personalizing MTD-based therapy. Isolation of Circulating Tumor Cells (CTCs) from the blood of metastatic patients has emerged as a valid source of tumor tissue in the form of liquid biopsy that is being used as prognostic biomarker based on CTC enumeration. To be able to perform molecular CTC analyses we have developed a BC specific microfluidic device that operates on the principle of geometrically enhanced differential immunocapture (GEDI), using antibody-coated microposts. We selected HER2 as BC selective surface antigen to isolate CTCs from MBC patients as it is expressed in 90% of breast tumors and overexpressed in 30%, while it is minimally affected by epithelial-to-mesenchymal transition (EMT) often occurring in metastasis. We previously demonstrated that the ability of the HER2 GEDI microfluidic device to capture BC cells expressing high and intermediate to low levels of HER2 expression confirming its suitability for BC patients with highly heterogeneous HER2 levels. We have tested the HER2-based GEDI in MBC patients and have confirmed CTC capture. To test the performance of our device we are currently comparing it to the FDA approved CellSearch using blood from the same patient where CTCs are enumerated by both Cell Search and our device. Importantly, the retained viability of GEDI-captured CTCs provides us the opportunity to functionally test CTC response to chemotherapy directly on the device, in an effort to develop an assay predictive of clinical response so that we can tailor chemotherapy to the individual. In this assay, we are treating the GEDI-captured CTCs with physiologically relevant concentrations of MTDs and are subsequently assaying drug-induced target modifications. As a proof of principle, we have demonstrated that taxane sensitive BC cell lines captured on the GEDI device showed evidence of effective drug-target engagement by the presence of microtubule bundling following Docetaxel treatment. We are currently evaluating the response of GEDI-captured BC taxane-resistant cells to ex-vivo drug treatment to evaluate the dynamic range of our assay. We are currently conducting a clinical trial that characterizes GEDI-captured CTCs isolated from MTD treated MBC patients where we will monitor the molecular characteristics of the CTCs during chemotherapy treatment and at disease relapse. This approach will give us significant insight of the mechanisms of resistance of MTDs. Citation Format: Giuseppe Galletti, Brian Kirby, Linda T. Vahdat, Paraskevi Giannakakou. Development of a HER2-based GEDI microfluidic device for the molecular characterization of CTCs from metastatic breast cancer patients. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1467. doi:10.1158/1538-7445.AM2013-1467