Blood specimens were rocked for 5 minutes before a white blood cell (WBC) count was measured using the Hemocue white blood cell system (HemoCue, Sweden). Based upon the WBC count, a volume of blood was subjected to erythrocyte lysis (ammonium chloride solution). After centrifugation, nucleated cells were re-suspended in PBS and attached as a monolayer on custom made glass slides. The glass slides are the same size as standard microscopy slides but have a proprietary coating that allows maximal retention of live cells. Each slide can hold approximately 3 million nucleated cells, thus the number of cells plated per slide depended on the patients WBC count.
For HD-CTC detection in cancer patients for this study, 4 slides are used as a test. The remaining slides created for each patient are stored at −80°C for future experiments. Four slides were thawed from each patient, then cells were fixed with 2% paraformaldehyde, permeabilized with cold methanol, and non-specific binding sites were blocked with goat serum. Slides were subsequently incubated with monoclonal anti-pan cytokeratin antibody (Sigma) and CD45-Alexa 647 (Serotec) for 40 minutes at 37°C. After PBS washes, slides were incubated with Alexa Fluor 555 goat anti-mouse antibody (Invitrogen) for 20 minutes at 37°C. Cells were counterstained with DAPI for 10 minutes and mounted with an aqueous mounting media.
For HD-CTC detection in cancer patients for this study, 4 slides are used as a test. The remaining slides created for each patient are stored at −80°C for future experiments. Four slides were thawed from each patient, then cells were fixed with 2% paraformaldehyde, permeabilized with cold methanol, and non-specific binding sites were blocked with goat serum. Slides were subsequently incubated with monoclonal anti-pan cytokeratin antibody (Sigma) and CD45-Alexa 647 (Serotec) for 40 minutes at 37°C. After PBS washes, slides were incubated with Alexa Fluor 555 goat anti-mouse antibody (Invitrogen) for 20 minutes at 37°C. Cells were counterstained with DAPI for 10 minutes and mounted with an aqueous mounting media.