Abstract 4816: Circulating tumor cell monitoring, isolation, and culture from a patient with metastatic triple-negative breast cancer for drug screening and creation of a patient-derived xenograft model
Authors: Ramirez Arturo B. , Blau C Anthony , Martins Timothy J. , Mahen Elisabeth , Dobrolecki Lacey E. , Lewis Michael T. , Stilwell Jackie L. , Kaldjian Eric P. 
Published: July 2017

Background.  Enumeration, phenotyping and single cell genomics of circulating tumor cells (CTCs) provide three types of information to guide cancer therapy. In some instances, a fourth type is possible: functional analysis in vitro, or in in vivo patient-derived xenografts (PDXs). We used a density-based rare cell separation and analysis system to collect CTCs from the blood of a patient with metastatic triple-negative breast cancer (TNBC) for in vitro culture and high-throughput drug screening and to generate a PDX model.

Methods: The patient was enrolled in the ITOMIC-001 study (University of Washington) and after informed consent, CTCs were evaluated prior to initial cisplatin treatment and tracked longitudinally using the AccuCyte – CyteFinder system (RareCyte). Samples containing high numbers of CTCs were placed into 3 different culture media. Cells grown in culture were tested against a panel of anti-cancer drugs and injected into mice to form a PDX model.

Results: Nine CTC evaluations were performed over 9.5 months. CTCs were verified by expression of epithelial (cytokeratin and/or EpCAM) and nuclear stains without CD45 expression. After initial treatment with cisplatin, the CTC count per 7.5 mL rose from 4 to 19 cells at 3 months, consistent with the lack of a clinical response, and decreased after LE 011 (CDK4/6 inhibitor) and then glembatumumab vedotin (anti-gpNMB) to 8 and 4 cells at 5 and 7 months respectively. At 9 months the CTC count rose to &gt; 13,000 and 5 days later to &gt; 80,000 shortly before her death. At autopsy there was massive infiltration of the liver and pulmonary vasculature by tumor cells. Cultures in all media showed initial growth, but only one (RPMI + 10% serum) was sustained, forming semi-adherent 3D tumor clusters. 6 million cells were harvested and a drug screen using 160 anti-cancer agents was performed. The CTC line showed sensitivity to several agents. Cells were also injected into the mammary fat pad of immunodeficient mice. In at least one mouse, macroscopic tumors were observed. The CTC cell line has grown continually in culture for over a year. Aliquots of this cell line have been frozen and thawed with no noticeable effect on cell growth.

Conclusions: Using a density-based rare cell collection system, we have established a CTC cell line from a TNBC patient with extremely high CTC counts. The line was used to perform a screen for agents active against the tumor cells and to create a PDX model. As in vitro techniques advance, smaller number of CTCs may be effectively cultured and thus allow this approach to be used in real time to find effective drug regiments for individualized cancer therapy.

Citation Format: Arturo B. Ramirez, C Anthony Blau, Timothy J. Martins, Elisabeth Mahen, Lacey E. Dobrolecki, Michael T. Lewis, Jackie L. Stilwell, Eric P. Kaldjian. Circulating tumor cell monitoring, isolation, and culture from a patient with metastatic triple-negative breast cancer for drug screening and creation of a patient-derived xenograft model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4816. doi:10.1158/1538-7445.AM2017-4816