Abstract 1458: Efficient isolation of circulating tumor cells in small cell lung cancer patients using size- and geometry-controlled microcavity array system.
Authors: Hosokawa Masahito , Kenmotsu Hirotsugu , Koh Yasuhiro , Yoshino Tomoko , Tanaka Tsuyoshi , Naito Tateaki , Takahashi Toshiaki , Murakami Haruyasu , Nakamura Yukiko , Tsuya Asuka , Shukuya Takehito , Ono Akira , Akamatsu Hiroaki , Watanabe Reiko , Ono Sachiyo , Kanbara Hisashige , Matsunaga Tadashi , Yamamoto Nobuyuki 
Published: August 2014

Background: We have developed a microcavity array (MCA) system integrated with a miniaturized device for the isolation of circulating tumor cells (CTC) without relying on EpCAM expression. The MCA system allows the filtration of tumor cells from whole blood on the basis of differences in the size between tumor and blood cells. The previous study has shown that the MCA system is potentially superior to the conventional epithelial antigen-based method for detecting CTCs in non-small cell lung cancer. Recently, we further optimized the shape and porosity of MCA to efficiently isolate smaller tumor cells as in small cell lung cancer (SCLC). Here we report the results of clinical study in SCLC patients comparing MCA system to CellSearch system and exploratory study of novel rectangular-shaped MCA system.

Methods: The MCA is made of nickel by electroforming and circular MCA is fabricated with 8-9 μm diameter pores. Meanwhile, novel rectangular-shaped MCA is fabricated with 5-9 μm-wide and 30-60 μm-long pores. NCI-H69 (12 μm in diameter) SCLC cells were used for spike-in experiments. CTCs were defined as cells with round to oval morphology, a visible nucleus, positive for cytokeratin and negative for CD45. For the clinical evaluation, paired peripheral blood samples were collected from 18 SCLC patients to compare the performance of the CellSearch system and the MCA system for CTC detection.

Results: The recovery rate of spiked NCI-H69 cells with the rectangular-shaped MCA (80 ± 2%) was significantly higher than that with the circular MCA (67 ± 4%) (p=0.01, t-test). In addition, the carryover of leukocytes on the rectangular-shaped MCA was 7-fold lower than that on the circular MCA in the experiment using healthy donor blood. The fluctuation of flow resistance during filtration with the rectangular-shaped MCA (&lt;1.5 kPa) was smaller than that with the circular MCA (2 kPa); the rectangular-shaped MCA enabled recovery of small tumor cells with high efficiency. In clinical study, compared to the CellSearch, the circular and rectangular-shaped MCA system identified significantly more SCLC patients (9 of 18 vs. 18 of 18 vs. 17 of 18, respectively) as CTC positive. No significant difference was observed in the CTC counts between the rectangular-shaped MCA (median 16, range 0-545 cells/7.5 mL) and the circular MCA (median 23, range 2-2329 cells/7.5 mL) (p=0.77, Wilcoxon test). In contrast, the number of captured leukocytes on the rectangular-shaped MCA was significantly lower than that on the circular MCA (p&lt;0.0001, Wilcoxon test), suggesting that implementing the rectangular-shaped MCA diminishes a considerable number of carryover leukocytes.

Conclusion: The MCA system has a potential as a tool for the efficient recovery of CTCs in small cell type tumors with high purity, while offering the additional advantages in cost, portability, and capacity to perform more detailed analyses of CTCs.

Citation Format: Masahito Hosokawa, Hirotsugu Kenmotsu, Yasuhiro Koh, Tomoko Yoshino, Tsuyoshi Tanaka, Tateaki Naito, Toshiaki Takahashi, Haruyasu Murakami, Yukiko Nakamura, Asuka Tsuya, Takehito Shukuya, Akira Ono, Hiroaki Akamatsu, Reiko Watanabe, Sachiyo Ono, Hisashige Kanbara, Tadashi Matsunaga, Nobuyuki Yamamoto. Efficient isolation of circulating tumor cells in small cell lung cancer patients using size- and geometry-controlled microcavity array system. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1458. doi:10.1158/1538-7445.AM2013-1458