Measuring antigen expression of cancer cell lines and circulating tumour cells

Abstract

When evaluating EpCAM-based enrichment technologies for circulating tumour cells (CTCs), the cell lines used should closely resemble real CTCs, meaning the EpCAM expression of CTCs needs to be known, but also the EpCAM expression of cell lines at different institutions and times is important. As the number of CTCs in the blood is low, we enriched CTCs through the depletion of leukocytes from diagnostic leukapheresis products of 13 prostate cancer patients and measured EpCAM expression using quantitative flow cytometry. Antigen expression was compared between multiple institutions by measuring cultures from each institution. Capture efficiency was also measured for one of the used cell lines. Results show CTCs derived from castration-sensitive prostate cancer patients have varying but relatively low EpCAM expression, with median expression per patient ranging from 35 to 89,534 (mean 24,993) molecules per cell. A large variation in the antigen expression of identical cell lines cultured at different institutions was found, resulting in recoveries when using the CellSearch system ranging from 12 up to 83% for the same cell line. We conclude that large differences in capture efficiency can occur while using the same cell line. To closely resemble real CTCs from castration-sensitive prostate cancer patients, a cell line with a relatively low EpCAM expression should be used, and its expression should be monitored frequently.

A Novel Method for Real-Time Quantification of Radioligand Binding to Living Tumor Cells In Vitro

“…For SKBR-3 cells, a cell line with a high HER2-expression level (similar to SKOV-3), a variability in the antigen expression has been observed over a 6-month period, corresponding to a threefold change in the number of antigens per cell and a coefficient of variation of up to 58%. 17 Another mechanism that could affect the simulated number of antigens is internalization of the antibody. Internalization of trastuzumab and antigen recycling (i.e., relocation of the HER2 antigen to the cell membrane) has been observed.…”

Assessment of Different Circulating Tumor Cell Platforms for Uveal Melanoma: Potential Impact for Future Routine Clinical Practice

“…According to us, the variable and heterogeneous expression of CD146 could explain the low recovery rate and the discrepancies found in the literature. Furthermore, a highly variable expression of the antigen in identical cell lines cultured in different institutions has already been reported, resulting in recovery rates ranging between 12 and up to 83% for a given epithelial cell line when the CellSearch system was used [ 56 ]. This finding highlights a limitation of the label-dependent Cellsearch platform.…”

Prostate cancer-derived small extracellular vesicle proteins: the hope in diagnosis, prognosis, and therapeutics

“…For example, cold tumors like PCa have a unique tumor immune-suppressive microenvironment, making them insensitive to immunotherapy [ 163 ]. Additionally, they exhibit different antigen expression patterns [ 164 ], raising concerns about whether sEV-based vaccines can effectively cover antigen variations. Furthermore, there are difficulties in production, optimization of delivery, and determining the therapeutic efficacy and dosage, all of which are inevitable obstacles.…”