CTC Isolation from a Whole Blood Sample: A Method to Obtain CTCs from Murine Colorectal Cancer Model

- Circulating Tumor Cells, or CTCs, are the cancer cells that stem from the primary tumor and enter the blood circulation. Most CTCs can survive in the bloodstream without attaching to the surface; therefore, we can detect them directly from the blood of most cancer patients.

CTCs in the blood can indicate the tumor's spread inside the body, hence identifying them helps understand cancer progression. Begin by taking an anesthetized colorectal cancer mouse model and obtain blood by cardiac puncture. Transfer the blood into a conical tube containing density gradient medium and centrifuge to separate blood components.

Discard the topmost layer containing plasma and collect the peripheral blood mononuclear cell fraction, or PBMC, present at the interface in a separate tube. Next, add the anti-EpCAM antibody to PBMC cells and observe under a fluorescent microscope. Circulating CTCs express a cell marker known as Epithelial Cell Adhesion Molecule or EpCAM. Therefore, anti-EpCAM antibodies can help identify EpCAM positive CTCs.

Collect the CTCs and store them for further downstream analysis. In the following protocol, we will identify the EpCAM-expressing CTCs from the peripheral mononucl