Investigation of custom biomarkers on circulating tumor cells from clinical samples using RarePlex Developer Kits
Cancer-specific biomarkers are emerging faster than CTC assays can be built to measure them — this AACR 2020 poster adds up to 2 user-selected antibodies to a validated three-channel CTC detection assay with RarePlex Developer Kits, then reads them on model CTCs and on prostate and breast cancer patient samples.
Presented by RareCyte / University of Washington.
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- Developer Kits add two open channels to a validated three-channel CTC assay. The RarePlex CTC Panel Kit identifies CTCs with a nuclear dye, anti-CD45 to exclude white blood cells, and cocktailed cytokeratin and EpCAM antibodies, leaving Developer Kits to carry up to 2 user-selected markers — tested here across HER2, ER, PR, Vimentin, SYP, EGFR, Ki67, AR, ARv7 and PSMA, each with the expected localization on model CTC control cells under default antigen retrieval and fixation.
- Marker-positive and marker-negative cell lines separated cleanly on median cell intensity. In spiked model CTCs, ARv7 read a median MFI of 403.0 on 22Rv1 against 36.8 on the negative BT474 line, and PSMA read 161.0 on LNCaP against 12.2 on MCF7; fluorescence intensity cut-offs segregating the negative and positive lines were then defined statistically for each biomarker.
- A breast cancer patient's two tumor phenotypes both appeared among the CTCs. That patient carried both ER+/HER2- and ER+/HER2+ tumors, and the same heterogeneity showed in the CTCs: 13 scored ER+/HER2+ and 3 ER+/HER2-, alongside 3 ER-/HER2+ and 2 ER-/HER2-; in a prostate cancer patient, 26 CTCs scored AR+/ARv7- and 4 AR+/ARv7+, against 13 AR-/ARv7- and 0 AR-/ARv7+.
