Professor and Department Chair University of California San Diego La Jolla, California, United States
Introduction: : Breast cancer has high rates of early-stage detection, but when metastasis occurs from the primary tumor, there is a significant reduction in the 5-year survival rate. Furthermore, 20% of women that are initially categorized as having less severe disease, e.g., ductal carcinoma in situ (DCIS), will eventually develop more aggressive cancer. The absence of a universal molecular marker, coupled with the heterogeneity within the tumor microenvironment, makes it difficult to accurately assess the metastatic potential of some breast cancer types. However, biophysical properties such as adhesion strength could be an alternative means of assessing metastatic potential. We have previously shown that weakly adherent cells form more secondary disease in lung [1], but where during the metastatic process is there a competitive advantage for weakly adherent cells is not clear. We hypothesize that early parts of this process, which involve tumor dissemination, proliferation, and migration across the endothelium, afford significant advantages to weakly adherent cells.
Materials and
Methods: : Triple-negative breast cancer cells were seeded on extracellular matrix (ECM)-coated plates prior to sorting. Cells were separated into weakly adherent (WA) and strongly adherent (SA) populations using an patented microfluidic device known, i.e., parallel-plate flow chamber (PPFC). After sorting, the cells were maintained in selection conditions consistent with tumor stroma, e.g., low cation media. To evaluate their ability to proliferate and disseminate as well as migrate through confined spaces, cells were either cultured as spheroids and embedded in collagen hydrogels to assess dissemination and proliferation or seeded into a trans well assay as a surrogate for transendothelial migration.
Results, Conclusions, and Discussions:: To assess where the competitive advantage occurs to enable weakly adherent cells to metastasize faster and at a higher rate than strongly adherent cells [1], we first performed a 3D invasion assay by embedding tumor spheroids in collagen hydrogels. We found that WA cells proliferate more and survive at higher rates than SA cells immediately post sort. When embedded as spheroids in low cation media, WA cells may be more migratory and directionally migratory than SA cells; similarly on 2D hydrogels, WA cells migrate faster than WA cells. Once approaching the endothelium, cells must traverse this barrier, which affords another opportunity for selection. When seeding our adhesion-sorted cells (weakly adherent and strongly adherent cells) in a trans well assay, we found that WA cells migrate through transwell pores at higher rates than their SA counterparts (Figure 1). These data support the notion that weakly adherent cells form more secondary disease in part because of migration and proliferation advantages early in the metastatic process.
Acknowledgements and/or References (Optional):: [1] Kane et al, Cell Reports, 2025.
