Ex vivo culture of circulating tumor cells using magnetic force-based coculture on a fibroblast feeder layer.

Phenotype-based analysis of circulating tumor cells (CTCs) is a promising approach to identification of new therapeutic targets and to elucidation of the biological properties. Nonetheless, ex vivo culturing of CTCs is still a technical challenge. Here, we develop a novel ex vivo culture method for CTCs using a fibroblast feeder layer and a magnetic coculture protocol. CTCs in the blood of a mouse metastasis model are labeled magnetically with magnetite nanoparticles. The labeled CTCs are isolated by a magnetic capture column and a size-selective capture filter. The isolated CTCs are positioned on a fibroblast feeder layer by the magnetic force. As a result, we observe adhesion and proliferation of the CTCs under the conditions of the fibroblast feeder layer and the magnetic force, whereas no adhesion or proliferation is observed without the feeder layer. After that, we culture the CTCs and obtain three CTC-derived cell lines. Using these cell lines, we perform phenotype-based analyses of invasiveness and drug resistance and find that the CTC-derived cell lines are more malignant than the original cells. Thus, the proposed method would be a promising approach to ex vivo culture of CTCs for phenotype-based analysis, and possibly used in cancer treatment.

Efficient capturing of circulating tumor cells using a magnetic capture column and a size-selective filter.

Detecting and analyzing circulating tumor cells (CTCs) in the blood of cancer patients is a promising approach for the early diagnosis of metastasis. Previously, we developed a size-selective filter for capturing CTCs, but its use was time consuming, particularly for capturing CTCs from large volumes of blood. In the present study, we describe the use of a magnetic capture column for rapid and efficient isolation of CTCs, which were magnetically labeled with magnetite cationic liposomes. In the capturing process, large volumes of blood containing magnetically labeled cancer cells were introduced into the column at a high flow rate to capture the cells, which were then added into the filter at a low flow rate. Our results show that the combined use of the column and filter decreased the required time for the spiked cancer cell capture, and the recovery rate of the spiked cancer cells from blood was significantly higher using the combination process (80.7 %) than that using the filter alone (64.7 %). Moreover, almost twice the number of CTCs could be captured from the blood of metastatic model mice using the combination process. These results suggest that the developed process would be useful for the rapid and efficient isolation of CTCs.