Matrix Rigidity Regulates Cancer Cell Growth and Cellular Phenotype

TLDR

Extracellular matrix stiffness influences cell growth and differentiation, but the extent to which cancer cells respond to changes in matrix rigidity remains unclear. This study aimed to determine how variations in extracellular matrix rigidity affect the biological properties of tumor cells. The authors employed a 96‑well plate system with ECM‑conjugated polyacrylamide gels whose stiffness increases at least 50‑fold across the plate to assess these effects. Cell lines segregated into rigidity‑dependent and rigidity‑independent groups, with poor soft‑gel growth linked to reduced spreading, migration, and in vivo tumorigenicity, and A549 cells on soft gels up‑regulated E‑cadherin while down‑regulating Slug, demonstrating that matrix stiffness governs cancer cell proliferation and phenotype.

Abstract

Background The mechanical properties of the extracellular matrix have an important role in cell growth and differentiation. However, it is unclear as to what extent cancer cells respond to changes in the mechanical properties (rigidity/stiffness) of the microenvironment and how this response varies among cancer cell lines. Methodology/Principal Findings In this study we used a recently developed 96-well plate system that arrays extracellular matrix-conjugated polyacrylamide gels that increase in stiffness by at least 50-fold across the plate. This plate was used to determine how changes in the rigidity of the extracellular matrix modulate the biological properties of tumor cells. The cell lines tested fall into one of two categories based on their proliferation on substrates of differing stiffness: “rigidity dependent” (those which show an increase in cell growth as extracellular rigidity is increased), and “rigidity independent” (those which grow equally on both soft and stiff substrates). Cells which grew poorly on soft gels also showed decreased spreading and migration under these conditions. More importantly, seeding the cell lines into the lungs of nude mice revealed that the ability of cells to grow on soft gels in vitro correlated with their ability to grow in a soft tissue environment in vivo. The lung carcinoma line A549 responded to culture on soft gels by expressing the differentiated epithelial marker E-cadherin and decreasing the expression of the mesenchymal transcription factor Slug. Conclusions/Significance These observations suggest that the mechanical properties of the matrix environment play a significant role in regulating the proliferation and the morphological properties of cancer cells. Further, the multiwell format of the soft-plate assay is a useful and effective adjunct to established 3-dimensional cell culture models.