Fibrin Stiffness Regulates Phenotypic Plasticity of Metastatic Breast Cancer Cells

The extracellular matrix (ECM)-regulated phenotypic plasticity is crucial for metastatic progression of triple negative breast Cancer (TNBC). While ECM faithful cell-based models are available for in situ and invasive tumors, such as cell aggregate cultures in reconstituted basement membrane and in collagenous gels, there are no ECM faithful models for metastatic circulating tumor cells (CTCs). Such models are essential to represent the stage of metastasis where clinical relevance and therapeutic opportunities are significant. Here, we cultured CTC-like DU4475 TNBC cells in mechanically tunable 3D fibrin hydrogel scaffolds. This is motivated as in circulation, fibrin aids CTC survival by forming a protective coating reducing shear stress and immune cell-mediated cytotoxicity and promotes several stages of late metastatic process at the interface between circulation and tissue. We show that fibrin hydrogels support DU4475 cell growth, resulting in spheroid formation. Furthermore, increasing fibrin stiffness from 57 to 175 Pa led to highly motile, actin and tubulin containing cellular protrusions, which associated with specific cell morphology and gene expression patterns that markedly differed from basement membrane or suspension cultures. Thus, mechanically tunable fibrin gels reveal specific matrix-based regulation of TNBC cell phenotype and offer scaffolds for CTC-like cells with better mechano-biological properties than liquid. This article is protected by copyright. All rights reserved.

3D cell culture; circulating tumor cells; fibrin hydrogel; metastasis; phenotypic plasticity; triple negative breast cancer.