(489g) Substrate Stiffness Affects Cancer Cell Responsiveness to Cytotoxic Drugs

Biomaterial-based in-vitro tissue models are the bridge between conventional tissue culture, which does not capture the complexity of human tissue, and animal models, which are costly, time consuming, and raise ethical concerns. One area in which in-vitro models are underrepresented, but where they can have an immediate impact, is the development of platforms for toxicity screening. Such in-vitro models have the potential to address the growing concerns about drug failures in clinical trials due to lack of efficacy or unexpected side effects, by providing an in-vivo-like cell microenvironment early in the drug discovery and preclinical development stage. In particular, current research suggests that cancer cells grown on standard tissue culture plastic as opposed to a biomaterial-based matrix have different susceptibilities to cytotoxic drugs, with matrix-seeding being more predictive of an in-vivo outcome, yet, the underlying reasons are largely unknown. Our overall goal is to determine key environmental cues that affect cancer cell responsiveness to cytotoxic drugs. The project presented here will outline the effect of matrix stiffness, which has been shown to play an important role in tumorogenesis, on cancer cell drug responsiveness. Our hypothesis is that matrix stiffness is a key factor in drug resistance and thus an assay emulating physiological stiffness would be a significantly better predictor of in-vivo toxicity than standard tissue culture plastic.

Towards testing this hypothesis, we have developed a high-throughput stiffness assay that utilizes extracellular matrix (ECM) protein-coated polyacrylamide (PA) gels that span a physiologically-relevant stiffness range (Young’s modulus of 1 – 100 kPa). To determine whether the matrix stiffness affects cancer cell responsiveness to cytotoxic drugs, we cultured cancer cells on collagen-coated PA gels and treated them with known drugs, such as Paclitaxel, of varying concentrations. Cell fate, including cell viability, proliferation, morphology, apoptosis, and cell cycle were measured quantitatively and drug IC₅₀ was determined. Our data indicates that cell responsiveness to drugs is strongly influenced by the matrix stiffness and that it is dependent on the cell and drug type.

In summary, current drug screening assays mostly are performed in rigid tissue culture plates but our findings suggest that physiological stiffness context might be more appropriate, which has implications for building predictive biomaterial-based in-vitro assays for drug screening.