Mechanistic adaptability of cancer cells strongly affects anti-migratory drug efficacy

Abstract

Cancer metastasis involves the dissemination of cancer cells from the primary tumour site and is responsible for the majority of solid tumour-related mortality. Screening of anti-metastasis drugs often includes functional assays that examine cancer cell invasion inside a three-dimensional hydrogel that mimics the extracellular matrix (ECM). Here, we built a mechanically tuneable collagen hydrogel model to recapitulate cancer spreading into heterogeneous tumour stroma and monitored the three-dimensional invasion of highly malignant breast cancer cells, MDA-MB-231. Migration assays were carried out in the presence and the absence of drugs affecting four typical molecular mechanisms involved in cell migration, as well as under five ECMs with different biophysical properties. Strikingly, the effects of the drugs were observed to vary strongly with matrix mechanics and microarchitecture, despite the little dependence of the inherent cancer cell migration on the ECM condition. Specifically, cytoskeletal contractility-targeting drugs reduced migration speed in sparse gels, whereas migration in dense gels was retarded effectively by inhibiting proteolysis. The results corroborate the ability of cancer cells to switch their multiple invasion mechanisms depending on ECM condition, thus suggesting the importance of factoring in the biophysical properties of the ECM in anti-metastasis drug screenings.

Concentric Gel System to Study the Biophysical Role of Matrix Microenvironment on 3D Cell Migration

“…We anticipate that the presence of directional chemotactic stimuli or biochemical gradients will increase the persistence, potentially in collagen concentration-dependent manner. Furthermore, we also observed that the mean speed of cell migration did not significantly change with collagen concentration (Figure 4D), likely because of the interplay between matrix stiffness (which increases with collagen concentration) and pore size (which decreases with collagen concentration) 10 , as well as the spatiotemporal variation of migration characteristics within the cell population 7 . The mean speed varied between 31 µm/hr and 37.5 µm/hr, with a minimum individual cell speed of 7 µm/hr and a maximum individual cell speed of 114 µm/hr.…”

“…It is now possible to obtain spatially-resolved viscoelastic measurements of the local matrices surrounding the cells using microrheological approaches 19 . Furthermore, our recent study 10 reveals that the efficacy of various anti-migratory drugs (administered on the 7 th day of the experiment) can be strongly affected by the architecture and stiffness of the matrix (i.e., outer gel). In the future, we plan to use these experimental frameworks to further understand how such effects can arise from the basic molecular mechanisms of cell migration (e.g., cytoskeletal contractility 20 , extracellular matrix reorganization 21 , and pericellular proteolysis 22 ).…”

“…For cells that do not naturally migrate in groups or clusters, the assay offers a way to analyze the migratory properties in detail from a large number of cells with diverse local microenvironment, which can provide important insights into the biophysical origins of migration efficiency and directional persistence 7,15 . Second, by modifying the gel conditions of the inner and outer gels, one can directly study the effect of matrix mechanics and microstructure on 3D cell migration behavior 10 . This is especially important, as it is known that cell migration and cancer invasion are highly influenced by matrix mechanics and porosity 16,17 , and that soft tissues in our body have a very diverse topology 18 .…”

“…Note: The outer gel condition can be varied in terms of collagen concentration and polymerization pH to obtain networks with different microstructures 10 . In this protocol, focus on a 1.5 -4.0 mg/ml collagen gel polymerized at a pH of 7.4.…”

“…The mean speed varied between 31 µm/hr and 37.5 µm/hr, with a minimum individual cell speed of 7 µm/hr and a maximum individual cell speed of 114 µm/hr. 7,10 . Please click here to view a larger version of this figure.…”