Brain metastases of triple-negative breast cancer (TNBC) rapidly progress, causing severe neurological decline with a median survival of less than 6 months. This tragic disease is often difficult to identify with sufficient time for treatment and is exacerbated by a lack of effective pharmacological intervention. Replicating the biochemical and mechanical properties of the premetastatic niche in vitro is a critical step in expediting the development of new therapeutics. However, a high-fidelity and reproducible model system is needed. To quantify the influence of a brain-mimetic microenvironment on brain metastatic TNBC, we encapsulated and cultured the TNBC cell line, MDA-MB-231 (P231), and its braintropic subline, MDA-MB-231-BrM2a-831 (BrM2a), in three premetastatic niches: a highly cell-adhesive and highly cell-degradable permissive niche, a highly adhesive but less degradable niche, and a nonadhesive but highly degradable niche. To mimic brain extracellular matrix, we functionalized the adhesive formulations with a brain-mimetic peptide cocktail and compared the cell responses to a “generic” RGDS-functionalization. This suite of conditions allowed us to investigate the influences of integrin-mediated adhesion, cell-mediated degradation, and cell type on the fate of P231s and BrM2as. Our data demonstrate that brain-mimetic adhesion has little to no impact on P231 phenotype, but the BrM2as display reduced viable cell density, reduced proliferation, and a higher proportion of both spherical clusters and spherical individual cells compared with the “generic” RGDS-functionalized niches. This suggests that brain-mimetic adhesion signaling encourages a rounded, less invasive phenotype in BrM2as. Modeling pathological processes usingadvanced, biomimetic in vitro models that better replicate in vivo cell phenotype have the potentialtoenhanceimprove the outcome of preclinical therapeutic testing.
Freeman et al. (2026) studied this question.