A biomaterial screening approach reveals microenvironmental mechanisms of drug resistance

Abstract

Traditional drug screening methods lack features of the tumor microenvironment that contribute to resistance. Most studies examine cell response in a single biomaterial platform in depth, leaving a gap in understanding how extracellular signals such as stiffness, dimensionality, and cell-cell contacts act independently or are integrated within a cell to affect either drug sensitivity or resistance. This is critically important, as adaptive resistance is mediated, at least in part, by the extracellular matrix (ECM) of the tumor microenvironment. We developed an approach to screen drug responses in cells cultured on 2D and in 3D biomaterial environments to explore how key features of ECM mediate drug response. This approach uncovered that cells on 2D hydrogels and spheroids encapsulated in 3D hydrogels were less responsive to receptor tyrosine kinase (RTK)-targeting drugs sorafenib and lapatinib, but not cytotoxic drugs, compared to single cells in hydrogels and cells on plastic. We found that transcriptomic differences between these in vitro models and tumor xenografts did not reveal mechanisms of ECM-mediated resistance to sorafenib. However, a systems biology analysis of phospho-kinome data uncovered that variation in MEK phosphorylation was associated with RTK-targeted drug resistance. Using sorafenib as a model drug, we found that co-administration with a MEK inhibitor decreased ECM-mediated resistance in vitro and reduced in vivo tumor burden compared to sorafenib alone. In sum, we provide a novel strategy for identifying and overcoming ECM-mediated resistance mechanisms by performing drug screening, phospho-kinome analysis, and systems biology across multiple biomaterial environments.

Three‐dimensional culture models to study drug resistance in breast cancer

“…The alignment and amount of collagen changes with tumor development and alters drug efficacy (Walsh et al, 2015). Coculture of CAFs within a collagen I hydrogel on top of adherent MDA‐MB‐231 or MCF10A breast cancer cells resulted in a model that allowed Schwartz et al (2017) to investigate the influence Tranilast and DOX have on the cells' ability to remodel their environment, which alters cell proliferation and invasiveness. The hydrogels were micro‐molded via soft lithography.…”

“…This results in a stiffer tumor microenvironment, or desmoplastic stroma, that increases cancer proliferation, invasiveness, and drug resistance via upregulation of FAK. Treatment with Tranilast and DOX together reduced the ability of fibroblasts to stiffen their environment (Schwartz et al, 2017). This observation in synergistic treatment was also made in a similar model with MDA‐MB‐231 and stromal HTB‐125 cells, where without Tranilast, DOX therapy lead to increased fibrosis and thus drug resistance (Saini et al, 2018).…”

“…In contrast with natural hydrogel models, synthetic hydrogels can be reproducibly manufactured with microenvironments still tunable to that of mammary tissue or metastatic site. For instance, MDA‐MB‐231 or SkBr3 spheroids seeded on a 3D PEG‐maleimide (PEG‐MAL) hydrogel was used to compare the cell lines' resistance to RTK inhibitors and cytotoxic agents in 3D versus culture on TPCS and 2D PEG‐phosphorocholine‐coated wells (Schwartz et al, 2017). Spheroid diameters less than 100μm allowed for drug and oxygen diffusion without a necrotic core, therefore isolating the effects of 3D geometry and elastic modulus.…”

“…DOX sensitized both cell lines in 3D. It was determined that the resistance was solely ECM‐driven due to MEK phosphorylation, not gene expression or the stiffness‐dependence of JNK signaling (Schwartz et al, 2017). Using another synthetic polymer, polyacrylamide (PAM) hydrogels of varying stiffnesses/pore sizes, the response of SkBr3 breast cancer cells to Lapatinib was investigated (Liu et al, 2016).…”

Anomalous Diffusion as a Descriptive Model of Cell Migration

“…However, in vivo, cell movement is largely in 3D, with cells surrounded by ECM and other cells. To test the effectiveness of the AD model in describing this type of confined cell movement, we used another PEG-based gel [39][40][41] and measured cell motility in 3D as we exposed them to different pro-migratory chemical stimulations (conditioned medium from patient cell cultures). The gels were crosslinked with MMP-sensitive peptides, but the mesh size was orders of magnitude smaller than a cell (~20-25nm).…”