Interpolation method for accurate affinity ranking of arrayed ligand analyte interactions

The values of the affinity constants (kd, ka, and KD) that are determined by label-free interaction analysis methods are affected by the ligand density. This article outlines a surface plasmon resonance (SPR) imaging method that yields high-throughput globally fitted affinity ranking values using a 96-plex array. A kinetic titration experiment without a regeneration step has been applied for various coupled antibodies binding to a single antigen. Globally fitted rate (kd and ka) and dissociation equilibrium (KD) constants for various ligand densities and analyte concentrations are exponentially interpolated to the KD at Rmax = 100 RU response level (KDR100)

EpCAMhigh and EpCAMlow circulating tumour cells in metastatic prostate and breast cancer patients

The presence of high expressing epithelial cell adhesion molecule (EpCAMhigh) circulating tumor cells (CTC) enumerated by CellSearch® in blood of cancer patients is strongly associated with poor prognosis. This raises the question about the presence and relation with clinical outcome of low EpCAM expressing CTC (EpCAMlow CTC). In the EU-FP7 CTC-Trap program, we investigated the presence of EpCAMhigh and EpCAMlow CTC using CellSearch, followed by microfiltration of the EpCAMhigh CTC depleted blood. Blood samples of 108 castration-resistant prostate cancer patients and 22 metastatic breast cancer patients were processed at six participating sites, using protocols and tools developed in the CTC-Trap program. Of the prostate cancer patients, 53% had ≥5 EpCAMhigh CTC and 28% had ≥5 EpCAMlow CTC. For breast cancer patients, 32% had ≥5 EpCAMhigh CTC and 36% had ≥5 EpCAMlow CTC. 70% of prostate cancer patients and 64% of breast cancer patients had in total ≥5 EpCAMhigh and/or EpCAMlow CTC, increasing the number of patients in whom CTC are detected. Castration-resistant prostate cancer patients with ≥5 EpCAMhigh CTC had shorter overall survival versus those with <5 EpCAMhigh CTC (p = 0.000). However, presence of EpCAMlow CTC had no relation with overall survival. This emphasizes the importance to demonstrate the relation with clinical outcome when presence of CTC identified with different technologies are reported, as different CTC subpopulations can have different relations with clinical outcome

Capture of Tumor Cells on Anti-EpCAM-Functionalized Poly(acrylic acid)-Coated Surfaces

The presence of tumor cells in blood is predictive of short survival in several cancers and their isolation and characterization can guide toward the use of more effective treatments. These circulating tumor cells (CTC) are, however, extremely rare and require a technology that is sufficiently sensitive and specific to identify CTC against a background of billions of blood cells. Immuno-capture of cells expressing the epithelial cell adhesion molecule (EpCAM) are frequently used to enrich CTC from blood. The choice of bio conjugation strategy and antibody clone is crucial for adequate cell capture but is poorly understood. In this study, we determined the binding affinity constants and epitope binding of the EpCAM antibodies VU1D-9, HO-3, EpAb3-5, and MJ-37 by surface plasmon resonance imaging (SPRi). Glass surfaces were coated using a poly(acrylic acid) based coating and functionalized with anti-EpCAM antibodies. Binding of cells from the breast carcinoma cell line (SKBR-3) to the functionalized surfaces were compared. Although EpAb3-5 displayed the highest binding affinity HO-3 captured the highest amount of cells. Hence we report differences in the performance of the different antibodies and more importantly that the choice of antibody to capture CTC should be based on multiple assays

EpCAMhigh and EpCAMlow circulating tumor cells in metastatic prostate and breast cancer patients

The presence of high expressing epithelial cell adhesion molecule (EpCAMhigh) circulating tumor cells (CTC) enumerated by CellSearch® in blood of cancer patients is strongly associated with poor prognosis. This raises the question about the presence and relation with clinical outcome of low EpCAM expressing CTC (EpCAMlow CTC). In the EU-FP7 CTC-Trap program, we investigated the presence of EpCAMhigh and EpCAMlow CTC using CellSearch, followed by microfiltration of the EpCAMhigh CTC depleted blood. Blood samples of 108 castration-resistant prostate cancer patients and 22 metastatic breast cancer patients were processed at six participating sites, using protocols and tools developed in the CTC-Trap program. Of the prostate cancer patients, 53% had ≥5 EpCAMhigh CTC and 28% had ≥5 EpCAMlow CTC. For breast cancer patients, 32% had ≥5 EpCAMhigh CTC and 36% had ≥5 EpCAMlow CTC. 70% of prostate cancer patients and 64% of breast cancer patients had in total ≥5 EpCAMhigh and/or EpCAMlow CTC, increasing the number of patients in whom CTC are detected. Castration-resistant prostate cancer patients with ≥5 EpCAMhigh CTC had shorter overall survival versus those with <5 EpCAMhigh CTC (p = 0.000). However, presence of EpCAMlow CTC had no relation with overall survival. This emphasizes the importance to demonstrate the relation with clinical outcome when presence of CTC identified with different technologies are reported, as different CTC subpopulations can have different relations with clinical outcome