Circulating tumor cell isolation: the assets of filtration methods with polycarbonate track-etched filters

Abstract

Circulating tumor cells (CTCs) arise from primary or secondary tumors and enter the bloodstream by active or passive intravasation. Given the low number of CTCs, enrichment is necessary for detection. Filtration methods are based on selection of CTCs by size using a filter with 6.5 to 8 µm pores. After coloration, collected CTCs are evaluated according to morphological criteria. Immunophenotyping and fluorescence in situ hybridization techniques may be used. Selected CTCs can also be cultivated in vitro to provide more material. Analysis of genomic mutations is difficult because it requires adapted techniques due to limited DNA materials. Filtration-selected CTCs have shown prognostic value in many studies but multicentric validating trials are mandatory to strengthen this assessment. Other clinical applications are promising such as follow-up, therapy response prediction and diagnosis. Microfluidic emerging systems could optimize filtration-selected CTCs by increasing selection accuracy.

Keywords: Circulating tumor cells (CTCs); biological markers; filtration.

Figure 1

Clusters of circulating tumor cells (CTCs) with anisocaryosis, large nuclei and conspicuous nucleoli (Obj. × 40).

Figure 2

Anti-CDX2 nuclear immunostaining: (A) HCT116 cell line (B) circulating tumor cells (CTCs) in a patient with colorectal cancer (Obj. × 40).

Figure 3

Fluorescence in situ hybridization on PANC1 cell line with DNA Vysis EGFR (epidermal growth factor receptor)/CEP 7^® (centromere enumerating probe) (Abbott^®) (Obj. ×40): four spots of each color are present, demonstrating chromosome seven polysomy.