Functional Characterization of Circulating Tumour Cell (CTC) Clusters in Breast Cancer

Abstract

Breast cancer (BC) is the most common malignancy in women and the second leading cause of cancer-related deaths. Most cancer-related deaths are due to metastasis, a process by which tumour cells spread to secondary sites. Circulating tumour cells (CTCs) are those tumour cells that are released into the bloodstream, and they are the responsible for the formation of metastases. CTCs can be found as individual cells, or as small groups of cells, called CTC clusters. CTC clusters have a higher metastatic potential than individual CTCs. However, there is little knowledge about the biology of CTC clusters due to their low frequency in the blood of BC patients. The objective of this thesis project is to conduct a comparative study between individual CTCs and CTC clusters, to further study the biology of CTC clusters and to determine the differential characteristics that provide them with greater metastatic potential. The isolation of CTC clusters from samples of BC patients not only allowed us to confirm the prognostic value of CTC clusters but also to optimize workflows that maximise the detection of CTC clusters. The development of in vitro models of CTC clusters and their later functional/molecular characterization showed that these models properly recapitulated the phenotypic features of the CTC clusters isolated from patient samples. The combination of the tools presented in this thesis can contribute to overcome the restrictions derived from the low frequency of CTC clusters in patient samples and allow a deeper understanding about the role of CTC clusters during metastasis.