Increased phenotypic depth for automated visual identification of biomarkers on circulating tumor cells by cocktailing epithelial markers EpCAM and cytokeratin
Canonical circulating tumor cell identification spends two of six fluorescence channels proving a cell is epithelial, leaving only two for the biomarkers under investigation; this AACR 2018 poster cocktails EpCAM and cytokeratin into a single channel, reads up to three investigational biomarkers at once in model CTCs, and applies the 4-parameter CTC-3 + AR assay to blood from one prostate cancer patient.
Presented by RareCyte / University of Washington.
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- Cocktailing the two epithelial markers into one channel turns two biomarker channels into three. The CTC-4 panel spends channel 3 on cytokeratin and channel 4 on EpCAM, leaving channels 5 and 6 for biomarkers; the CTC-3 panel places CK/EpCAM together in channel 3 of the same 6-channel imaging, opening channels 4, 5 and 6 to investigational markers.
- In one prostate cancer patient sample, 114 of the 160 CTCs identified per mL carried the androgen receptor. The 4-parameter CTC-3 + AR assay first demonstrated AR expression in LNCaP and 22RV1 model CTCs but not in PC3, which does not express AR, confirming staining specificity; applied to blood from a patient with a known high CTC count, it read 160 CTCs per mL and scored 114 of them (71%) AR-positive.
- In spike-in model CTCs, the freed channels carried up to three investigational biomarkers at once. A 5-parameter CTC-3 + AR / AR-V7 assay used 2 of them to separate the splice variant from full-length AR, with 22RV1 expressing both, LNCaP AR only and PC3 neither; a 6-parameter CTC-3 + ER / Her2 / Ki-67 assay used all 3 and returned ER and Her2 patterns consistent with the reported phenotypes of BT474, MCF-7, SKBR3 and MDA-MB-231 cells.
