Abstract B20: EpCAM-independent ApoStream™ technology isolates circulating tumor cells from blood of patients with various types of cancer.
Authors: Davis Darren , Gupta Vishal , Garza Miguel , Pace Margaret , Wu Weiguo , Neal Chris , Sukumaran Sujita , Woo Jacky , Melnikova Vladislava O. , Hasegawa Dave 
Published: June 2012

Introduction: Referred to as a “liquid tumor biopsy”, the ability to enrich Circulating Tumor Cells (CTCs) from blood samples allows for the analysis of cancer cells undergoing metastatic dissemination and has been a hallmark of biomarker discovery. However, the use of EpCAM-based enrichment platforms limits the type of tumor cells that can be recovered, which subsequently limits the use of CTCs as surrogates for the classical tumor biopsy. Therefore an EpCAM-independent enrichment platform is critically needed.

Specific Aims: The performance of a novel antibody-independent dielectrophoretic field-flow fractionation based CTC isolation technology ApoStream was demonstrated in spiked cell model and cancer patient blood.

Experimental Procedures: We used ApoStream, a novel antibody-independent technology, to enrich CTCs from prostate and breast cancer patient blood (high EpCAM expression), non-small cell lung cancer patient blood (NSCLC, low EpCAM expression) and melanoma (no EpCAM expression). Cells isolated from ApoStream were stained for cytokeratin (CK), CD45, and DAPI, and melanoma CTCs with tumor marker S100, CD45 and DAPI. Imaging and CTC enumeration were done using laser scanning cytometry (LSC). CTC morphology in lung cancer specimens was confirmed with H&E staining. To further demonstrate performance of ApoStream platform, EpCAM-negative ovarian cancer cells SKOV3 were spiked into peripheral blood mononuclear cells (PBMCs) from normal donor blood and isolated using the ApoStream device.

Results: High CTC recovery from cancer patient blood samples was achieved with counts ranging from 0 − 2104 (lung, n=33), 0 − 3490 (prostate, n=15), 176 − 968 (breast, n=3), and 4 − 3120 (melanoma, n=11) CTCs per 7.5 ml blood. Positive CTC counts were obtained in ninety percent of NSCLC samples, 93% of prostate cancer samples, 100% breast cancer and melanoma specimens. There were no false-positive CTCs from normal donor blood controls demonstrating ApoStream's specificity. In cell spiking experiments, 80 ± 3% cells were recovered by ApoStream after spiking of EpCAM-negative ovarian cancer cells (SKOV3) into human peripheral blood mononuclear cells (PBMCs). EpCAM-negative CTCs were also recovered in all tested breast cancer patient specimens, confirming that ApoStream isolates cancer cells independent on their EpCAM status.

Conclusions: Our data demonstrate that the ApoStream platform recovers large numbers of CTCs from the blood of patients with metastatic NSCLC, prostate, breast cancer and melanoma. Thus, the ApoStream CTCisolation platform provides a new effective tool with broad applications in cancer biomarker discovery and personalization of cancer therapies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B20.