Bioengineering The Tumour Microenvironment In Vitro: Insights into Tumour Progression, and Therapy Response

In solid tumours, cells reside within a highly dynamic and heterogeneous microenvironment shaped by various physicochemical gradients. This environment significantly influences tumour cell behaviour, including metabolism, proliferation, invasion, and therapy response. In this thesis, we developed advanced in vitro models designed to recapitulate key features of the tumour microenvironment (TME), including oxygen, nutrient gradients, as well as physical cues. By leveraging novel fabrication techniques, such as micromilling and melt electrowriting, these models offer physiologically relevant platforms for investigating tumour progression and response to therapy. Three distinct models were developed, each designed to capture key aspects of the TME: a spheroid-on-a-chip system for studying tumour recovery and repopulation after repeated exposure to chemotherapy, a microfluidic device for simulating oxygen gradients, and a hybrid 3D scaffold system for examining tumour cell migration. Results provide key insights into tumour behaviour during recovery from chemotherapy, demonstrating that tumour cells undergo distinct adaptive mechanisms, with molecular responses varying depending on exposure duration and recovery time. This suggests that chemotherapy induces tumour cell plasticity, a critical factor in treatment resistance. In the microfluidic device where oxygen gradients were simulated, tumour cells were able to create an oxygen gradient, although challenges such as vertical oxygen gradients and delayed gradient formation were encountered. In this model, collagen concentrations and cell density impacted oxygen distribution, particularly with higher matrix densities could induce hypoxia-like conditions, complicating oxygen diffusion and cellular responses. The scaffold based system, revealed distinct differences in the migration pattern of breast cancer cell lines in response to physical cues. MDA-MB-231 cells exhibited rapid and directional migration, characterised by leader-follower movement, while T47D cells displayed collective movement with strong cell-cell adhesion and limited migration. This model demonstrated that scaffold architecture facilitated tumour cell motility, highlighting the role of matrix stiffness and the physical properties of the TME on tumour cell migration. Together, these models not only enhance our understanding of tumour cell behaviour but also offer a promising platform for investigating cancer progression, therapeutic resistance, and the development of more effective, targeted treatment strategies. By accurately mimicking critical features of the TME, this work lays the foundation for future research aimed at improving cancer therapies that exploit tumour adaptation to their microenvironment or therapeutic stress.