Abstract 1820P
Background
The CTC (circulating tumor cells) population is heterogeneous, and includes canonical tumor cells (CD45-EpCAM+ and/or cytokeratins+) and cells with a hybrid phenotype (CD45+EpCAM+ and/or cytokeratins+). Hybrid CTCs are very poorly studied. Their molecular characteristics, determining invasive and metastatic properties (stemness and epithelial-mesenchymal transition (EMT)), need to be clarified. The aim of this study was to evaluate phenotypic features and gene expression profile of hybrid CTCs.
Methods
The prospective study included 108 breast cancer patients with stage T1-3N0-3M0, admitted for treatment to Cancer Research Institute, Tomsk NRMC. All patients signed an informed consent for voluntary participation. Flow cytometry was used to analyze the phenotypes of hybrid CTCs (Novocyte 3000, ACEA Biosciences, USA). The gene expression profile of hybrid CTCs was assessed using NGS sequencing (NextSeq500, Illumina, USA).
Results
The population of hybrid CTCs is heterogeneous in breast cancer. It is represented mainly by cells with mono-expression of the epithelial marker EpCAM (96,3%, р=0,0001) and less by cells with mono-expression of the epithelial marker CK7/8 (р=0,001). Сells without stemness and EMT properties predominate among hybrid CTCs with EpCAM mono-expression (94,4%, р=0,006). Stem-like cells without EMT features are more common among hybrid CTCs with co-expression of EpCAM and CK7/8 (78,7%, р=0,039). The subset of hybrid CTCs with CK7/8 mono-expression is dominated by cells without stemness features and with or without EMT properties (72,2%, р=0,0001). The existing hypothesis about the origin of hybrid CTCs by fusion of tumor cells with macrophages of tumor microenvironment is confirmed by the gene expression of macrophage markers CD163 and CD11b in hybrid breast cancer cells. The metastatic potential in hybrid CTCs is evidenced by the activity of TOLL-like receptors, NF-kappa B and MAPK signaling pathways.
Conclusions
Thus, the gene expression of macrophage markers as well as stem and EMT features of hybrid CTCs can determine their chemoresistance and high metastatic potential in breast cancer. The study was supported by The Council for grants of President of Russian Federation (grant SS-2701.2020.7).
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
The Council for Grants of President of the Russian Federation.
Disclosure
All authors have declared no conflicts of interest.