After ageing, high mammographic density is the second largest risk factor for breast cancer. Although the biological basis for high mammographic density remains unclear, increased mammographic density has been linked to an elevated mechanical stiffness of the extracellular matrix surrounding mammary epithelial cells. Despite the well-known link between mechanical stress and cell fate, and the potential influence on breast cancer susceptibility, little is known about how mammary epithelial cells sense and respond to the mechanical properties of their environment. Understanding the link between elevated mechanical stiffness and cancer initiation is crucial to developing preventive strategies for breast cancer. Much of our understanding of mechanotransduction comes from studying cells seeded on two-dimensional substrates of varying stiffness. However, single-cell studies cannot incorporate the microenvironmental cues, signalling networks, or cellâcell interactions present in vivo. Organoid cultures can recapitulate the architecture and phenotypical behaviour of mammary epithelial cells with reasonable fidelity, providing a more physiologically relevant model for studying mechanotransduction in glandular structures. This work aimed to understand the forces experienced by mammary epithelial cell organoids cultured in three-dimensional microenvironments of varying stiffness and to explore the initial cellular response to mechanical stress. A mechanically tuneable culture model was used to study the effect of force on cell behaviour in the context of an organised mammary organoid. Although we aimed to disentangle the early effects of elevated stiffness from downstream signalling cascades, we found evidence of altered signalling after 1 d culture in a stiff microenvironment. Organoid phenotypes diverged strikingly depending on microenvironmental stiffness. A computational simulation of acinar growth was built to investigate interactions between cells and their microenvironment and understand the mechanisms driving these altered phenotypes. The model was refined iteratively through the incorporation of wet lab results and was used to generate new testable hypotheses. Biological and computational results led us to hypothesise that the transformed phenotype adopted by organoids in stiff microenvironments was caused partly by changes in their apoptotic signalling. We found that increasing mitochondrial priming in these organoids was sufficient to restore a normal phenotype. However, reducing apoptosis by overexpressing the anti-apoptotic protein Bcl-xL was insufficient to induce the "stiff" phenotype in acini cultured in soft microenvironments.
- cancer
- mcf10a
- computation modelling
- mammary epithelial cell
- organoid
- mechanotransduction
- systems biology
- stiffness
- breast cancer
Modelling the Impact of Extracellular Matrix Stiffness on Mammary Epithelial Cells
Taylor-Hearn, I. (Author). 1 Aug 2025
Student thesis: Phd