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.

Cancer progression is driven by complex interactions between tumor cells and their surrounding microenvironment, which together undergo profound physical and biological changes. A key aspect of this crosstalk is the alteration of biophysical properties in both cells and the extracellular matrix (ECM), influencing processes such as invasion and metastasis. This dissertation investigates these biophysical changes with a focus on rheology, which describes how materials deform and flow under stress.

We developed a microfluidic platform to dynamically compress breast cancer spheroids of varying malignancy, extracting their viscoelastic properties and linking them to cytoskeletal organization and cell–cell adhesion. The results show that malignant spheroids are softer, more deformable, and prone to fragmentation compared to benign ones, facilitating invasion under physical stress. Expanding the scope to the ECM, we studied collagen I matrices embedded with invasive breast cancer cells. Bulk rheology and rheoconfocal microscopy revealed that cancer cells actively remodel collagen networks, suppressing the typical stress-stiffening response and inducing time-dependent softening, in contrast to fibroblasts or passive inclusions.

Together, these findings provide new insights into how cancer cells and the ECM dynamically influence each other’s rheological properties. This dissertation highlights the importance of viscoelasticity in tumor progression and suggests future opportunities for translating such biophysical insights into diagnostic or therapeutic approaches.

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.

Within the tumor microenvironment (TME), cancer cells use mechanotransduction pathways to convert biophysical forces to biochemical signals. However, the underlying mechanisms and functional significance of these pathways remain largely unclear. The upregulation of mechanosensitive pathways from biophysical forces such as interstitial flow (IF), leads to the activation of various cytokines, including transforming growth factor-β (TGF-β). TGF-β promotes in part via a Smad-dependent signaling pathway the epithelial–mesenchymal transition (EMT) in cancer cells. The latter process is linked to increased cancer cell motility and invasion. Current research models have limited ability to investigate the combined effects of biophysical forces (such as IF) and cytokines (TGF-β) in a 3D microenvironment. We used a 3D-matrix based microfluidic platform to demonstrate the potentiating effect of IF on exogenous TGF-β induced upregulation of the Smad-signaling activity and the expression of mesenchymal marker vimentin in A549 lung cancer spheroids. To monitor this, we used stably integrated fluorescent based reporters into the A549 cancer cell genome. Our results demonstrate that IF enhances exogenous TGF-β induced Smad-signaling activity in lung cancer spheroids embedded in a matrix microenvironment. In addition, we observed an increased cell motility for A549 spheroids when exposed to IF and TGF-β. Our 3D-microfluidic model integrated with real-time imaging provides a powerful tool for investigating cancer cell signaling and motility associated with invasion characteristics in a physiologically relevant TME.