New study increases the precision of the detection of circulating tumor cells

Circulating tumour cells, commonly known as CTCs, are live tumour cells released by the active tumour into blood circulation, which allows them to travel through the body and potentially form new tumour in other organs, or metastases. The enumeration of CTCs holds prognostic information but, most importantly, CTCs can serve to evaluate the presence of druggable targets, enabling the oncologist to continuously monitor the patients non-invasively and adjust their treatment in a personalised manner. The study of CTCs is also crucial to better understand their role in the metastatic cascade. However, CTCs are rare and heterogeneous, which makes their isolation and identification complicated. Currently, the identification of CTCs is primarily achieved through immunocytochemistry, using markers such as cytokeratin and CD45. Cytokeratin identifies epithelial cells and is used as a positive marker, while CD45 is a haematopoietic marker and is used to identify and exclude white blood cells. Yet, the granulocyte sub-population of white blood cells may express low or no levels of CD45, and can show non-specific affinity to cytokeratin, which can lead to the misclassification of granulocytes as CTCs. This highlights the need for more sensitive, specific, and robust classification criteria to reliably identify CTCs. The present study demonstrated that adding a second exclusion marker, CD15, enabled a proper identification of granulocytes, which proved essential for the accurate detection and identification of CTCs. Having more accurate and robust CTC classification criteria will allow to harness the true diagnostic potential of liquid biopsies to predict response to treatment and, ultimately, guide clinical decision making.

Authors and Affiliations:

Adriana Carneiro ^{1 2 3} , Paulina Piairo ^{1 4} , Beatriz Matos ^{1 5} , Daniela A.R. Santos ^{2 6} , Carlos Palmeira ^{1 7 8} , Lúcio Lara Santos ^{1 9} , Luís Lima ² , Lorena Diéguez ^{1 4}

¹ International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga s/n, 4715-330, Braga, Portugal

² Experimental Pathology and Therapeutics Group, Research Center of IPO Porto (CI IPOP) / RISE @ CI-IPOP (Health Research Network), Portuguese Oncology Institute of Porto (IPO Porto), Porto Comprehensive Cancer Center (Porto.CCC), 4200-072, Porto, Portugal

³ Instituto de Ciências Biomédicas Abel Salazar (ICBAS) da Universidade do Porto, Porto, Portugal

⁴ RUBYnanomed Lda, Praça Conde de Agrolongo 123, 4700-312, Braga, Portugal

⁵ NOVA School of Science and Technology, Caparica, 2829-516, Portugal

⁶ School of Health, Polytechnic Institute of Porto, Rua Dr. António Bernardino de Almeida, 400, 4200-072, Porto, Portugal

⁷ Department of Immunology, Portuguese Oncology Institute of Porto (IPO-Porto), Porto, 4200-072, Portugal

⁸ Biomedical Research Center (CEBIMED, Faculty of Health Sciences, Fernando Pessoa University (UFP), Porto, 4249-004, Portugal

⁹ Department of Surgical Oncology, Portuguese Institute of Oncology (IPO-Porto), 4200-072, Porto, Portugal

Abstract:

Cancer is a leading cause of death worldwide, with metastasis playing a significant role. Circulating Tumour Cells (CTCs) can provide important real-time insights into tumour heterogeneity and clonal evolution, making them an important tool for early diagnosis and patient monitoring. Isolated CTCs are typically identified by immunocytochemistry using positive biomarkers (cytokeratin) and exclusion biomarkers (CD45). However, some white blood cell (WBC) populations can express low levels of CD45 and stain non-specifically for cytokeratin, increasing their risk of misclassification as CTCs. There is a clear need to improve CTC detection and enumeration criteria to unequivocally eliminate interfering WBC populations.

Journal: Analytica Chimica Acta

Link: https://www.sciencedirect.com/science/article/pii/S0003267023013867?via%3Dihub