Abstract 31P
Background
Spatial transcriptomic analysis is a powerful tool that can be used to search for tumor cell subpopulations that have the potential to detach from the primary tumor and form organ-specific metastases in integrin-dependent manner.
Methods
FFPE tissues from two triple-negative breast cancer patients (BC) (without distant metastases and with lung metastases) were sectioning to 5 μm and placement on one Capture Area of Visium Spatial Slide. Libraries were loaded at 1.8 pM and sequenced NextSeq 500 System (Illumina, CA, USA). The Space Ranger 1.3.1 software provided by was used to perform sample demultiplexing, alignment, tissue detection, fiducial detection, and UMI counting. The obtained data were analyzed and visualized using the 10x Genomics Loupe Browser 6.0 software.
Results
Comparison of gene expression in spots with tumor cells revealed top 100 significant altered genes in sample with metastasis, which were analyzed using the Enrichr database. Thus, the most significant pathway in tumor cells from metastatic BC sample was epithelial-mesenchymal transition (EMT) (p=6,3e-8). Further, we evaluated gene expression of epithelial marker – EpCam; EMT marker – N-cadherin; and MENA, protein which is associated with invasiveness potential. It turned out that tumor cells co-expressed both molecules were detected only in spots of metastatic BC patient and majority of cells were located at the invasive tumor front. We also assessed expression of specific integrins, which directed metastasis to lung, liver and brain according to Hoshino A. et al. (2015) data, in spots with N-cadherin+/MENA+ tumor cells. 46 spots with EpCam+/N-cadherin+/MENA+ tumor cell expressed integrin aVb5 (to liver), 33 spots – with b4 (to lung), 23 spots - b3 (to brain). While 16 spots contained tumor cells with simultaneous expression of all three types of integrins.
Conclusions
We performed spatial transcriptomics assay which provided visualization of tumor cells with phenotype potentially promote hematogenous metastasis to the lung, liver and brain. The presence of a clinically detected metastasis in the lung probably indicates the existence of an effective pre-metastatic niche in the target organ.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Russian Science Foundation (grant #21-15-00140).
Disclosure
All authors have declared no conflicts of interest.