Abstract 380: Capture of EpCAM-negative circulating tumor cells (CTCs) with a “Universal CTC-Chip”

Abstract

Abstract Background: Circulating tumor cell (CTC) can be a potentially useful clinical marker in early diagnosis and monitoring therapeutic effects for patients with malignant tumors. Our previous study showed that CTC detected by an EpCAM (epithelial cell adhesion molecule) based immuno-magnetic separation system “CellSearch” was useful in the diagnosis of malignant pleural mesothelioma (MPM), and also useful in the prognosis of epithelioid type MPM (Yoneda K, et al. Ann Surg Oncol. 2013). However, EpCAM-negative tumor cells cannot be principally captured with the system. Therefore, we have developed EpCAM-independent “Universal CTC-Chip System”, and assessed its capture capability. Methods: PC-9 (lung cancer cell line) was employed as EpCAM-positive cells, ACC-MESO-1 and ACC-MESO-4 (mesothelioma cell lines) were employed as EpCAM-negative cells. The expression of cell surface antigen was confirmed by flow cytometry. A microfluidic devices made of resin was coated in two steps with bridging antibody and capture antibody. It is possible to use any antibody to capture. In this study, we use anti-EpCAM antibody, anti-podoplain antibody, anti-mesothelin antibody, and isotype control. First, we verified capture capability of this system using samples which were spiked tumor cells labeled with CFSE in PBS containing 5% BSA. Then, we measured in the same manner by adding the cells to the blood of healthy donor, and calculated capture rate. Results: The expression analysis of cell surface antigens, PC-9 was EpCAM-positive, podoplanin, mesothelin were negative. On the other hand, MESO-1, 4 was EpCAM negative, podoplanin, mesothelin were positive. The capture efficiency in PBS containing 5% BSA with each cell using anti-EpCAM antibody, anti-podoplanin antibody and anti-mesothelin were PC-9: 101.1% / 2.3% / 2.9%, MESO-1: 3.5% / 52.7% / 4.3%, MESO-4: 3.0% / 78.3% / 5.4%, respectively. In the study of blood, each of the capture rate using anti-EpCAM antibody and anti-podoplanin antibody were PC-9: 88.0/ 6.9%, MESO-1: 4.0%/ 12.7%, MESO-4: 2.2%/ 38.4%, respectively. Conclusions: The capture efficiency using this device depends on the expression intensity of cell surface antigens. In experiments with PBS samples, it was possible to capture targeting specific cell surface antigen. Mesothelioma cells in the blood ware captured with combination of this CTC-Chip system and anti-podoplanin antibody. Citation Format: Kazue Yoneda, Yasuhiro Chikaishi, Eri Kawashima, Tomoko So, Hidetaka Uramoto, Takashi Ohnaga, Fumihiro Tanaka. Capture of EpCAM-negative circulating tumor cells (CTCs) with a “Universal CTC-Chip”. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 380. doi:10.1158/1538-7445.AM2015-380