Top: The role of circulating tumour cells (CTCs) in metastasis (Source: Rostami, Peyman & Kashaninejad, Navid & Moshksayan, Khashayar & Saidi, Mohammad & Firoozabadi, B. & Nguyen, Nam-Trung. (2019). Novel approaches in cancer management with circulating tumor cell clusters. 10.1016/j.jsamd.2019.01.006.)

Bottom: 10-day cultured CTC stained using NucBlueTM (Kolostova et al, 2015)

One of the main reasons of death in cancer patients is the spread of cancer cells from the primary tumour to distant sites; what is referred to as metastasis, according to researchers Seyfried and Huysentruyt in Critical reviews in oncogenesis. The details of metastasis are the subject of research across many labs with several aspects of this phenomenon is yet to be unravelled in detail. One aspect of metastasis is circulating tumour cells (CTCs) defined as viable solid-tumour cells that break off from the primary tumour to be carried through the circulatory system to other regions (Eliasova et al, 2013).

These cells can not only serve as tools to understand how the major cause of cancer-related death, metastasis occurs but also allow one to monitor the spread of the disease and treatment options. This becomes important given that 2014-published research in Pharmacology & Therapeutics by Friedlander reported that the presence of circulating tumour cells is linked to poor prognosis in patients. This can open up the avenue of developing drugs that target metastasis and hence, guide personalized therapies. The development of approaches to isolate circulating tumour cells can drive this goal.

The presence of circulating tumour cells in the blood is considered “low”- one tumour cell per 10⁷ blood cells (Mostert et al, 2009). This isolation and assessment of these cells referred to as “liquid biopsy” thus, becomes a challenge. Right now, most methods involve studying these cells using peripheral blood stabilized earlier. Such fixed samples cannot represent what the cells represent in terms of their functions or response to drugs. This has inspired many labs to take up approaches to isolate these cells. Apart from isolation, culturing circulating tumour cells in vitro can serve as the first step to assess their role in metastasis and their sensitivity to therapeutic molecules.

An interesting article published in the American Journal of translational research by scientists Kolostova and team in 2015 discussed the isolation and culture of circulating tumour cells from patients with ovarian, cervical and endometrial cancers. The collected peripheral blood was filtered through a porous polycarbonate membrane after which the membrane was placed on culture plates. The medium used was RPMI with 10% FBS under culture conditions for Cancer Cell Lines.

The cells could be cultured and visualized using staining. The cells were also analyzed for changes in important genes to reveal changes in EPCAM, MUC1 and KRT19, showing the suitability of cultured cells to check for biomarkers. The cultures of disseminated tumour cells (DTCs) can be tested for the effect of chemotherapeutic molecules using vital stains. This is important to target these cells to control metastasis.

Targeted cancer therapy is aimed at the metastatic cells. The analysis of CTCs from cultures can allow the identification of molecular patterns that can be targeted using therapeutic molecules. The enrichment and culture of CTCs followed by sensitive techniques such as RT-PCR (qPCR) can highlight important biomarkers. This can hence guide the development of “tailor-made” medicine or personalized medicine aimed at curing deadly diseases like cancer by targeting CTCs-the “fugitives on the run”.

References:

Seyfried TN, Huysentruyt LC. On the origin of cancer metastasis. Critical reviews in oncogenesis 2013; 18(1-2):43-73.

Eliasova P, Kolostova K, Kobierzycki C, Bobek V. Preclinical studies monitoring circulating and disseminated tumor cells in gastrointestinal cancers. Folia Histochemica et Cytobiologica (FHC). 2013; 51(4):265-77.

Friedlander TW, Premasekharan G, Paris PL. Looking back, to the future of circulating tumor cells. Pharmacology & Therapeutics 2014; 142:271–280.

Mostert B, Sleijfer S, Foekens JA, Gratama JW. Circulating tumor cells (CTCs): detection methods and their clinical relevance in breast cancer. Cancer Treatment Reviews 2009; 35(5):463-74.

Kolostova K, Spicka J, Matkowski R,  Bobek V. Isolation, primary culture, morphological and molecular characterization of circulating tumor cells in gynecological cancers. American journal of translational research 2015; 7(7), 1203–1213.