Killers in the blood: Circulating Tumors Cells (CTCs)

A typical cancerous tumor contains millions or even billions of cells harboring genetic mutations which drive them to grow, divide, and invade the tissue in which they are embedded. However, as the cells proliferate, they don’t all remain in the neighborhood. Some cells escape off the edges of a tumor and are swept away by the bloodstream or lymphatic system. These cells take the name of Circulating Tumor Cells (CTCs) and may colonize distant sites to form metastases.

A sensitive and reliable detection and enumeration of cancer cells in blood could provide a powerful diagnostic tool for early detection of tumor invasion and early assessment of treatment efficacy. 

However CTCs are:

  1. Very heterogeneous: they may significantly vary from each other in size, shape, and immunophenotyping profile.
  2. Fragile: they may be damaged and fragmented during the standard multi-step preparation processes, with coinsequent inaccurate detection and misinterpretation.

Available microscopy techniques require the sample to be fixed and stained with a clear loss of sample quality and increased risk of results falsification (Figure 1, flow below). In this blog post, are presented the advantages brought by Nanolive’s 3D Cell Explorer microscope in detecting and analyzing CTCs in a totally new, marker-free and ultra-rapid fashion.

Work flow of CTCs enrichment, detection and characterization

Figure 1. CTCs extraction, enrichment and analysis obtained with the 3D Cell Explorer (above) as opposed to traditional fluorescence microscopy (below).

Digital staining of the cell compartments based on their specific Refractive Index (RI) enables identification and analysis of CTCs A549 morphological features (Figure 2).

Figure 2. A549 (p5) circulating lung cancer cells in PBS.

In Figure 3 a whole blood sample after enrichment was analyzed in order to demonstrate how to distinguish CTCs from other normal Blood Cells with the 3D Cell Explorer.
On the image we can observe a few actors:

A549 (Red arrows): characterized by big round shape cells (diameter > 20 microns) they are generally multinucleated (2-3 nuclei).

Peripheral Blood Mononuclear Cells (PBMCs): they can be of two different types: round & flat shape and attached to the bottom of the dish (around 15 micron of diameter, Green arrows) or small floating spherical cells (less than 10 micron diameter), characterized by very high and homogeneous RI typical of nuclear region (Blue arrows). They possess only one, well defined nucleus.

Figure 3. Whole blood sample spiked with A549 lung cancer cells and processed on the Parsortix instrument in order to enrich for CTCs. The output of the Parsortix instrument (A549 and Periferical Blood Mononucleated Cells PBMCs) was resuspended in PBS and imaged.

For the sample granting and the kind permission to reproduce the images on this blog post we thank Stefan Peter, Ph.D. (R&D Manager at ANGLE Europe Limited, Guildford, United Kingdom)