Cancer metastasis leads to the transport and widespread of malignant cells from the primary tumor to other parts of the body by exploiting body fluids (lymphatic fluid, bloodstream, and interstitial fluid). While the transport of a single cancer cell in fluid flow has been studied in the past, it is unclear how a group of cancer cells (tumor) migrate under the impact of hydrodynamic force in vasculature. In this work, we address this knowledge gap by investigating the migration process of a cancer spheroid tumor in a micro-channel with a constriction using both experimental and computational methods. The Dissipative Particle Dynamics method was employed to simulate the mechanical components of the spheroid tumor and immersed boundary method is used for interaction of spheroid with the surrounding fluid. Our results suggest that the mechanical response of the spheroid tumor differs from a single cell. Our computational framework provides new capabilities for designing bioengineering devices for cell manipulation.

Collagen networks form the structural backbone of the extracellular matrix in both healthy and cancerous tissues, exhibiting nonlinear mechanical properties that crucially regulate tissue mechanics and cell behavior. Here, we investigate how the presence of invasive breast cancer cells (MDA-MB-231) influences the polymerization kinetics and mechanics of collagen networks using bulk shear rheology and rheo-confocal microscopy. We show that embedded cancer cells delay the onset of collagen polymerization due to volume exclusion effects. During polymerization, the cells (at 4% volume fraction) cause an unexpected time-dependent softening of the network. We show that this softening effect arises from active remodeling via adhesion and contractility rather than from proteolytic degradation. At higher cell volume fractions, the dominant effect of the cells shifts to volume exclusion, causing a two-fold reduction of network stiffness. Additionally, we demonstrate that cancer cells suppress the characteristic stress-stiffening response of collagen. This effect (partially) disappears when cell adhesion and contractility are inhibited, and it is absent when the cells are replaced by passive hydrogel particles. These findings provide new insights into how active inclusions modify the mechanics of fibrous networks, contributing to a better understanding of the role of cells in the mechanics of healthy and diseased tissues like invasive tumors. Statement of significance: Understanding how cells influence tissue mechanics is crucial to unravel disease progression. While fibroblasts are known to stiffen tissues, the role of invasive cancer cells is less clear. Using collagen-based tissue models, we reveal that cancer cells unexpectedly soften the collagen matrix and disrupt its stress-stiffening response. By comparing active cells to passive particles and selectively blocking cell functions, we show that volume exclusion, adhesion, and contractility each play distinct roles in shaping tissue mechanics. This work sheds light on the physical impact of cancer cells on their environment, advancing our understanding on how cells dynamically alter the mechanical properties of tissues.

The growth and invasion of solid tumors are associated with changes in their viscoelastic properties, influenced by both internal cellular factors and physical forces in the tumor microenvironment. Due to the lack of a comprehensive investigation of tumor tissue viscoelasticity, the relationship between such physical properties and cancer malignancy remains poorly understood. Here, the viscoelastic properties of breast cancer spheroids, 3D (in vitro) tumor models, are studied in relation to their metastatic potentials by imposing controlled, dynamic compression within a microfluidic constriction, and subsequently monitoring the relaxation of the imposed deformation. By adopting a modified Maxwell model to extract viscoelastic properties from the compression data, the benign (MCF-10A) spheroids are found to have higher bulk elastic modulus and viscosity compared to malignant spheroids (MCF-7 and MDA-MB-231). The relaxation is characterized by two timescales, captured by a double exponential fitting function, which reveals a similar fast rebound for MCF-7 and MCF-10A. Both the malignant spheroids exhibit similar long-term relaxation and display residual deformation. However, they differ significantly in morphology, particularly in intercellular movements. These differences between malignant spheroids are demonstrated to be linked to their cytoskeletal organization, by microscopic imaging of F-actin within the spheroids, together with cell-cell adhesion strength.