Abstract A51: Improved efficacy in capturing EpCAM-negative tumor cells using a universal CTC-chip
Authors: Yoneda Kazue , Chikaishi Yasuhiro , Kawashima Eri , Ohnaga Takashi , Tanaka Fumihiro 
Published: May 2019

Background: Circulating tumor cells (CTCs) are tumor cells shed from primary tumor and circulate in the peripheral blood. CTCs, as a surrogate of distant metastasis, can be potentially useful in diagnosis and monitoring therapeutic effects in malignant tumors. Among a variety of systems for detection of CTCs, the Cellsearch is the only system approved for clinical use. However, EpCAM-negative tumor cells, such as those originating from non-epithelial cells and those undergoing epithelial-mesenchymal transition, cannot be captured using the CellSearch that is an EpCAM-based immuno-magnetic separation system. Therefore, we have developed a novel polymeric microfluidic device system Universal CTC-chip that can capture a variety of CTCs with or without EpCAM expression (AACR 2015). In the present study, we further optimized its performance of capturing CTCs, especially EpCAM-negative CTCs.

Methods: The CTC-chip was used after two-step coating, first with a goat anti-mouse IgG antibody as base-antibody and then with a capture-antibody, either a mouse anti-EpCAM antibody to capture EpCAM-positive cells (EpCAM-chip) or a mouse anti-podoplanin antibody to capture podoplanin-positive cells (podoplanin chip). An EpCAM-positive cells (PC-9: lung cancer cell line) or an EpCAM-negative and podoplanin-positive cells (ACC-MESO-4: mesothelioma cell line) were suspended in phosphate-buffered saline (PBS) or in blood, and tumor cells were captured using the CTC-chip coated with a base-antibody and a capture-antibody at different concentrations.

Results: EpCAM-positive PC-9 cells were effectively captured using the EpCAM-chip coated with the base-antibody and the capture-antibody even at a lower concentration of 20μg/mL (capture rates, 101% for PBS-suspension and 88% for blood-suspension, respectively). EpCAM-negative MESO-4 cells were captured using the podoplanin-chip coated with antibodies at the lower concentration (20μg/mL), but the capture rates were lower especially for blood-suspension (78% for PBS-suspension and 38% for blood suspension, respectively). When the base-antibody was used at a higher concentration (200 or 500μg/mL) for coating the podoplanin-chip, capture efficiencies were improved for PBS-suspension (capture rates, 91% for 200μg/mL and 101% for 500μg/mL) and for blood-suspension (capture rates, 84% for 200μg/mL and 81% for 500μg/mL); even when the capture-antibody was used at a higher concentration (200μg/mL) in combination with the highest concentration of the base-antibody (500μg/mL), capture efficiencies were not further improved (capture rates, 97% for PBS-suspension and 82% for blood-suspension, respectively).

Conclusion: The efficiency in capturing CTCs using the Universal CTC-chip was improved by optimizing conditions of coating the chip.

Citation Format: Kazue Yoneda, Yasuhiro Chikaishi, Eri Kawashima, Takashi Ohnaga, Fumihiro Tanaka. Improved efficacy in capturing EpCAM-negative tumor cells using a universal CTC-chip. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr A51.