Mineralized Cryogel/Hydrogel Constructs to Recapitulate Early Breast Cancer Bone Metastasis In Vitro

Initial stages of bone colonization by breast cancer cells are critical for metastasis, but current in vitro models cannot decipher the microenvironmental cues involved. Therefore, a biphasic hydrogel model system is designed that recapitulates structural, biophysical, and biochemical components of the bone microenvironment to replicate early metastasis events. Breast cancer cells embedded within a glycosaminoglycan-based nanoporous hydrogel phase are traced as they colonize a directly adjacent macroporous cryogel compartment, precisely and selectively equipped with specific bone-like biomolecular signals and/or solution-deposited mineral crystals. Microscopic monitoring of the spatiotemporal cancer cell distributions yields colonization profiles that display the correlated effects of cell invasion, matrix interaction, and proliferation. MDA-MB-231 cells, but not MCF-7 cells, rapidly infiltrate the cryogel compartment at rates depending on the cross-linking degree of the hydrogel phase. Cryogel functionalization with adhesion-mediating peptide ligands enhances matrix interactions and survival/proliferation of the MDA-MB-231 cells. When combined with cryogel-released stromal cell-derived factor 1 (SDF-1), survival/proliferation are further amplified and additionally MDA-MB-231 cell invasion is promoted. The presence of deposited bone-like mineral strongly impedes these responses and is accompanied by characteristic alterations in distinct cellular gene-expression programs. The reported methodology may not only provide further mechanistic insights into early bone metastasis, but also facilitate the screening of anti-metastatic drugs.