Expression of eIF4E relevant biomarkers detected in circulating tumor cells from metastatic NSCLC and prostate cancer patients using antibody-independent ApoStream technology.

Abstract

e13562 Background: Enumeration of circulating tumor cells (CTCs) is used clinically to monitor disease progression and has previously been shown to be an independent biomarker for predicting survival of metastatic breast, prostate, and colorectal cancer patients. Molecular characterization of CTCs is rapidly emerging as a minimally invasive approach to interrogate the genotype and phenotype of cancers. However, the use of EpCAM-based enrichment platforms relies on the expression of EpCAM thus limiting the type of tumor cells that can be recovered. ApoStream, is a novel, antibody-independent, dielectrophoretic field-flow fractionation based technology that recovers CTCs from cancer patient blood samples. Methods: A side-by-side comparison of EpCAM dependent CellSearch and ApoStream was performed for CTC enumeration in NSCLC and prostate cancer patients. A multiplexed immunofluorescent assay was developed for CTC (cytokeratin+/CD45-/DAPI+ cells) enumeration. CTCs recovered by ApoStream were evaluated for the expression of multiple eIF4E pathway biomarkers using quantitative laser scanning cytometry (LSC). Results: ApoStream isolated a significantly greater number of CTCs in both NSCLC and prostate cancer patients (NSCLC: range 9-1037, mean=407 by ApoStream versus a range of 30-340, mean=118 by CellSearch , p<0.05; prostate cancer: range 12-3490, mean=1472 by ApoStream versus a range of 16-2155, mean=502 by CellSearch , p<0.05). The eIF4E protein expression in CTCs was positively correlated with the CTC count. A trend toward correlation between the eIF4E protein expression level and the expression levels of Cyclin D1, Survivin and Bcl-2 was observed. Conclusions: The ApoStream platform recovers higher numbers of CTCs from the blood of metastatic NSCLC and prostate cancer patients compared to the EpCAM-dependent CellSearch platform. CTCs recovered by ApoStream are suitable for downstream molecular analyses paving the way for broader applications in translational cancer research.