Abstract
Cancer metastasis initiates by invasion of subsets of cells away from the primary tumour into the surrounding stroma. Cells interact with surrounding extracellular matrix (ECM) through integrin adhesion receptors that are coupled indirectly to the cell cytoskeleton. Extracellular signal-regulated kinase 1/2 (ERK1/2) is a key signalling protein that responds to growth factors such as epidermal growth factor (EGF) via the EGF receptor (EGFR) and ECM engagement through integrin receptors, leading to tumour cell growth, invasion and metastasis. The organisation and local changes to mechanical properties of the tumour microenvironment are known to influence cell behaviour. Recent evidence suggests that surrounding stiffness of ECM in solid tumours can influence cell growth and invasion. However, it remains unclear whether these mechanical changes influence spatiotemporal patterns of activity of key oncogenic pathways such as ERK1/2. Moreover, the way in which mechanics feed into ERK1/2 signalling to specify an invasive versus proliferative tumour cell remain poorly defined.We hypothesised that the stiffness of the surrounding ECM can regulate the activity of a key pro-tumorigenic signalling protein ERK1/2 and dictate whether cells proliferate or invade. The goal of this project was to determine whether the ECM stiffness changes the patterns and dynamics of ERK activity, how this contributes to tumour growth and invasion and to define mechano-sensing receptors contributing to ERK-dependent tumorigenesis. Data demonstrated that ERK activity in MCF7 breast cancer cells (non-invasive, very low EGFR expression) reduced in response to increased stiffness on 2D surfaces but there was no change in ERK activity levels in HCC1954 breast cancer cells (invasive, high EGFR expression). Dynamics of ERK activation as measured using live cell imaging were also altered in response to substrate stiffness. Conversely, spheroid cultures of both cell lines showed enhanced ERK activity in 3D collagen gels with increasing stiffness, indicating key mechanosensing differences in physiologically relevant environments. Interestingly, ERK activity was higher in cells at the outer edges of MCF7 and HCC1954 spheroids compared to the core in all stiffness 3D scaffolds suggesting cell-ECM adhesion plays a key role in this response. These changes anti-correlated with proliferation and invasion, which were instead higher in lower stiffness 3D matrices. Further analysis revealed that EGFR and α2β1 integrins both played key roles as mechano-sensing receptors contributing to ERK1/2 activity and dynamics.
These data combined demonstrate that the 3D mechanical environment surrounding cancer cells can play a role in dictating spatiotemporal changes to ERK1/2 activation dynamics resulting in altered growth and invasive properties. This insight highlights the importance of the relationship between external stiffness and internal biochemical signals and may aide in defining therapeutic regimens for treatment.
| Date of Award | 1 Jun 2023 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Supervisor | Madeline Parsons (Supervisor) |