title: Filter characteristics influencing circulating tumor cell enrichment from whole blood.
abstract: A variety of filters assays have been described to enrich circulating tumor cells (CTC) based on differences in physical characteristics of blood cells and CTC. In this study we evaluate different filter types to derive the properties of the ideal filter for CTC enrichment. Between 0.1 and 10 mL of whole blood spiked with cells from tumor cell lines were passed through silicon nitride microsieves, polymer track-etched filters and metal TEM grids with various pore sizes. The recovery and size of 9 different culture cell lines was determined and compared to the size of EpCAM+CK+CD45-DNA+ CTC from patients with metastatic breast, colorectal and prostate cancer. The 8 µm track-etched filter and the 5 µm microsieve had the best performance on MDA-231, PC3-9 and SKBR-3 cells, enriching >80% of cells from whole blood. TEM grids had poor recovery of ∼25%. Median diameter of cell lines ranged from 10.9-19.0 µm, compared to 13.1, 10.7, and 11.0 µm for breast, prostate and colorectal CTC, respectively. The 11.4 µm COLO-320 cell line had the lowest recovery of 17%. The ideal filter for CTC enrichment is constructed of a stiff, flat material, is inert to blood cells, has at least 100,000 regularly spaced 5 µm pores for 1 ml of blood with a ≤10% porosity. While cell size is an important factor in determining recovery, other factors must be involved as well. To evaluate a filtration procedure, cell lines with a median size of 11-13 µm should be used to challenge the system.
authors.affiliation: Medical Cell BioPhysics, MIRA Institute, University of Twente, Enschede, The Netherlands.
authors.forename: Frank A W
authors.initials: FA
authors.lastname: Coumans
authors.forename: Guus
authors.initials: G
authors.lastname: van Dalum
authors.forename: Markus
authors.initials: M
authors.lastname: Beck
authors.forename: Leon W M M
authors.initials: LW
authors.lastname: Terstappen
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000473:pathology; D002452:Cell Count; D045744:Cell Line, Tumor; D002469:Cell Separation / Q000295:instrumentation* / Q000379:methods*; D048429:Cell Size; D015179:Colorectal Neoplasms / Q000473:pathology; D005260:Female; D005374:Filtration / Q000592:standards*; D006801:Humans; D008297:Male; D008422:Materials Testing / Q000592:standards; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009360:Neoplastic Cells, Circulating / Q000473:pathology*; D011076:Polycarboxylate Cement; D016062:Porosity; D011471:Prostatic Neoplasms / Q000473:pathology; D017655:Silicon Compounds
chemical_list: D011076:Polycarboxylate Cement; D017655:Silicon Compounds; C005506:polycarbonate; C032734:silicon nitride