Figure 1.

Real circulating tumor cells (CTC) clusters from patients with various types of cancer and “surrogate” CTC clusters from two established lung cancer cell lines (NCI-H187 and NCI-H2122). (A) CTC clusters isolated from individuals with small cell lung cancer [top row—left and middle panels (14)], prostate cancer [top row—right panel (4)], and breast cancer [bottom row (4)]; for staining details see references (images reproduced with permission from publishers*). CTC clusters from Ref. (14) were isolated using the CellSearch CTC Kit (Veridex, Warren, NJ, USA)—based on the co-expression of EpCam and CK-8, -18, and -19 markers, and the exclusion of cells expressing the white blood cell marker CD45 (29), as well as a membrane filtration system using the ISET platform (Metagenex, Paris, France) (30). CTC clusters from Ref. (4) were isolated using the HBCTC-Chip system (which employs biotinylated antibodies against EpCAM, EGFR, and HER2 to trap CTCs in microfluidic chambers) (12, 31) and the negCTC-iChip system (based on the depletion of both leukocytes and erythrocytes, followed by the identification of remaining CTCs) (32). (B) Cell clusters from H2122 (top row) and H187 (bottom row) cell lines (stained with Syto-9). (C) Cell clusters from H2122 (left panel) and H187 (right panel) immunostained for E-cadherin (in green; nuclei stained with DRAQ5 in blue); non-membrane localization of E-cadherin was also observed in real CTC clusters (14). (D) Cell clusters from H187 immunostained for vimentin (in green); vimentin is also heterogeneously expressed in real CTC clusters (14). *Images reprinted from Ref. (4), Copyright (2014), with permission from Elsevier. Images reprinted from Ref. (14), Copyright (2011), with permission from Elsevier.