Background:

Liquid biopsy has been reported as a potential surrogate for detection of cancer biomarkers with minimally invasive procedures. Particularly, numerical, phenotypical and genetical information of circulating tumor cells (CTCs), one of critical liquid biopsy materials, is well known to have clinical significances predicting and monitoring of disease progression, drug response and metastasis. However, a number of technical challenges for isolating CTCs and appropriate downstream analysis are still to be addressed.

Methods:

Here we designed high-throughput CTC enrichment device, GenoCTC, which adopted microfluidic magnetophoresis and CTC isolation chip with optimized ferromagnetic wire patterned on it. CTCs were enriched either by Anti-human EpCAM beads, a marker for mesenchymal-epithelial transition (MET), or Anti-human Vimentin beads, a marker for epithelial-mesenchymal transition (EMT). After immuno-magnetic based separation for EpCAM positive or Vimentin positive cells, CTCs are characterized by immunocytochemistry with Cytokeratin 18 and CD45, and then enumerated. Furthermore, MET amplification was investigated with isolated CTCs by ddPCR.

Results:

GenoCTC performance was optimized using the EpCAM positive cancer cell line, MCF7; 63% of recovery, 88% of separation rate and 93% of purity in whole blood spiking test. Analyzing 16 clinical blood samples from 10 non-small cell lung cancer (NSCLC) patients receiving drug treatment, the number of CTCs ranged from 2 to 112 CTCs per 7.5 mL. In serial CTC assessment of 5 NSCLC patients, transient changes in CTC numbers were observed which was positively correlated with the clinical course of disease progression. Moreover, c-MET amplification was confirmed only in CTCs, but not in ctDNA or tissue biopsy, at the point of progressive disease (PD) status in NSCLC patient with stable disease (SD). We also investigated the different CTCs counts between EpCAM and Vimentin based isolation in breast cancer patients. Interestingly, in patient with triple negative breast cancer, we observed only 1 CTC in case of separation based on EpCAM, but when separated by Vimentin, 26 CTCs were found. This result suggests CTCs may show the MET or EMT status of cancer in each patient.

Conclusion:

A newly developed GenoCTC can isolate CTCs sensitively and precisely and enable to reveal the clinical significance of CTCs. We expect this novel microfluidic device may facilitate the use of CTCs on diagnostic and prognostic criteria.

Citation Format: Miso Lee, Jiyeon Ryu, Hyeon Jin Kim, Dohyeong Kim, Mi Young Kim, Jin-Soo Kim, Seok-Woo Shin, Young Kee Shin, Seokbum Ko, Hun Seok Lee. GENOCTC, a highly efficient system for enrichment of circulating tumor cells and its clinical application [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1356.