Figure 2. The rare-cell scWB measures 12 unique protein targets in single cells from three cancer subtypes.

(a) Fluorescence micrographs and intensity plots from rare-cell scWB handling and analysis of healthy blood samples, each spiked with a cancer subtype: EGFR+(BT-20), ER+(MCF7) and HER2+(SK-BR-3). Negative controls include analysis of WBCs only and blank microwells (that is, devoid of a cancer cell). Protein panel comprises the following: control and housekeeping proteins (GAPDH and β-tubulin), oncoproteins (HER2, ER and EGFR), signalling proteins (ERK, eIF4E and mTOR), common CTC classifiers (EpCAM, panCK and CK8) and a WBC indicator (CD45). Scale bar, 50 μm. (b) Comparative protein expression for each cancer cell (BT-20: n=27; SK-BR-3: n=27; MCF7: n=35), with mean and CV noted for each marker. Protein expression is graphed using a log-scale. Ranked oncoprotein expression for each cell line agrees with cancer subtype. Less than 1% of total protein signal is attributable to CD45.