Our proprietary ApoStream technology was developed as part of a National Cancer Institute (NCI) initiative to support the development of a rare cell enrichment device for the isolation of circulating tumor cells (CTCs) from whole blood.
ApoStream is the only CTC technology co-developed and co-funded by the NCI and is currently being used by laboratories at the NCI to enable biomarker detection using liquid biopsies for oncology therapeutic development.
Theory of Operation
The ApoStream® technology leverages differences in the dielectric properties (polarizability) of any cell to isolate target cells using a process called dielectrophoresis (DEP) field-flow assist. A target cell’s dielectric properties are dependent upon several biophysical characteristics, including:
- Cell diameter and volume
- Surface area of the cell membrane
- Cellular density
- Chromatin density / ratio of nuclear to cytoplasmic volume
- Proteins present within in the cell and cell membrane
- Conductivity
The primary driver of ApoStream® enrichment is a charged electrode at the bottom of the chamber; when it is activated, a combination of forces, dominated by the electrophoretic charge, either attracts rare cells towards the electrode, or repels them. Differential flow rates relative to distance from the electrode aid in the fractionation of different cell types. The key advantages of ApoStream are the ability to isolate rare cells that are present in less frequency (1 in a billion) and in a viable state.
ApoStream CTC Isolation and Enrichment
CTCs have inherent differences from peripheral blood mononuclear cells (PBMCs) in morphology and dielectric properties. Following automated injection of a sample into the microfluidic chamber, the dielectrophoretic forces pull CTCs towards the interdigitated electrode on the chamber floor and repel blood cells into the proprietary eluant. Cancer cells are collected through a port located in the floor of the chamber while normal blood cells are carried away by the eluant and collected in a separate port.
Data collected from the NCI-60 cell lines has shown that cancer cells exhibit distinctly different dielectric properties, also known as cross over frequencies, as compared to PBMCs. These cross over frequencies have been applied to capture human CTCs from the blood of most advanced, and some early stage, solid tumors including breast, sarcoma, prostate, colorectal, pancreatic, bladder, renal cell carcinoma, head and neck carcinoma, ovarian, non-small cell lung cancer, small cell lung cancer, hepatocellular carcinoma and melanoma. We have demonstrated that ApoStream enriched CTCs from these various types of cancer carry genetic aberrations and are viable after collection.
Precision for Medicine (formerly ApoCell) offers the ApoStream technology as part of our suite of ‘liquid biopsy’ services to capture and enrich CTCs for further downstream characterization using a variety of platform technologies including quantitative image analysis, FISH, ISH and genomics including transcriptomics at the single cell level. Our clinical trial experience in using CTCs has identified cancer-type specific panels for detecting both epithelial and mesenchymal subtypes at any time point during therapy. We offer ApoStream services for isolating rare cells including circulating tumor cells (CTCs), stem cells, progenitor cells and differentiated immune cells including CAR-T cells, activated T cells, and other difficult to identify immune cell populations for immuno-oncology applications.
Other ApoStream Applications
The ApoStream® technology exploits dissimilarities of different target particles that arise from morphological and electrical properties to be separated in a microfluidic flow channel from any biofluid. Alternative ApoStream applications include isolating rare target particles from fluidic sources including infectious disease, bacterial, capsids, fetal cells, regenerative medicine and hematological cancers.
ApoStream® Key Benefits:
- Antibody-independent target cell capture
- Enriches target cells/particles present in low frequencies from biofluids
- Parameters to control high recovery and high purity
- Isolated cells are intact, viable, and can be cultured or used in animal models
- Small starting volume to continuous infusion
- No binding with target cells during processing
- Minimal cell loss during processing steps