"Prostate cancer is the most life-threatening cancer for men with high incident and mortality rates, accounting for 1.4 million cases worldwide in 2020 with around 52,000 new cases in the UK every year. The progression and malignancy of prostate cancer have been linked with enhanced fatty acid utilisation that may be driven by the need of the cancer cells for energy to support growth and metastasis. The development of new early-detection biomarkers and therapeutics for prostate cancer has been hindered by the lack of preclinical systems able to model the human tumour microenvironment. Growing cells in traditional two-dimensional (2D) cultures, cannot recapitulate essential tumour characteristics such as cell-cell and cell-matrix interactions that are observed in tissues’ three-dimensional (3D) organization. Additionally, 2D cultures cannot model the stiffness of prostate tissue, a property linked to disease development. To overcome these challenges 3D culture models have been developed with a view to enhance the complexity of in vitro models and provide a more realistic cell culture system.
In this project, we have used alginate-based hydrogels and formulated them to match the physical and chemical properties of the prostate tumour microenvironment, in particular the stiffness and extracellular matrix (ECM) composition. To develop this model, we used three prostate cell lines: the prostate epithelial cells PNT-2, the bone-metastatic prostate cancer cells PC-3, and the lymph node-metastatic prostate cancer cells LNCaP. Cells were encapsulated in alginate-gelatin-laminin hydrogel beads, formulated to have different physical properties. Soft hydrogels containing alginate (0.25% w/v), gelatin (3% w/v), and laminin (10 µg/mL) were designed to mimic physical properties of normal prostate microenvironment, whereas stiff hydrogels containing alginate (0.75% w/v), gelatin (3% w/v), and laminin (10 µg/mL) mimicked physical properties of prostate tumour microenvironment. The stiffness of the hydrogels was tested at different crosslinking density and set to 1.4 kPa for soft hydrogels and 6.9 kPa for the stiff ones. Prostate cells were encapsulated into hydrogel beads at an initial density of 1x106 cells/mL; proliferation and metabolic activity were measured up to 7 days. Whilst the metabolic activity of the prostate cancer PC-3 and LNCaP cells was reduced when encapsulated in stiff hydrogels, it was found to continuously increase in soft hydrogels. Conversely, the prostate epithelial PNT-2 cells did not show any change in their metabolic activity as function of hydrogel stiffness.
Our results show that prostate cancer cells behave differently in soft and stiff 3D microenvironments and this could be indicative of cellular adaptation. Detailed characterisation of relevant cellular biomarkers is needed to further understand the cells’ response to the altered microenvironment. The results of this study would provide novel insight into the prostate cancer cell adaptation to normal and tumour microenvironments. Further development and validation of this 3D in vitro model would help to understand the biochemical changes that occur during prostate cancer progression and could support the discovery of novel biomarkers and therapeutics."