The development of biomimetic, human tissue models is recognized as being an important step for transitioning in vitro research findings to the native in vivo response. Oftentimes, 2D models lack the necessary complexity to truly recapitulate cellular responses. The introduction of physiological features into 3D models informs us of how each component feature alters specific cellular response. We conducted a systematic review of research papers where the focus was the introduction of key biomimetic features into in vitro models of cancer, including 3D culture and hypoxia. We analysed outcomes from these and compiled our findings into distinct groupings to ascertain which biomimetic parameters correlated with specific responses. We found a number of biomimetic features which primed cancer cells to respond in a manner which matched in vivo response.

Epithelial to mesenchymal transition (EMT) in cancer is the process described where cancer epithelial cells acquire mesenchymal properties which can lead to enhanced invasiveness. Three-dimensional cancer models often lack the relevant and biomimetic microenvironment parameters appropriate to the native tumour microenvironment thought to drive EMT. In this study, HT-29 epithelial colorectal cells were cultivated in different oxygen and collagen concentrations to investigate how these biophysical parameters influenced invasion patterns and EMT. Colorectal HT-29 cells were grown in physiological hypoxia (5% O2) and normoxia (21% O2) in 2D, 3D soft (60 Pa), and 3D stiff (4 kPa) collagen matrices. Physiological hypoxia was sufficient to trigger expression of markers of EMT in the HT-29 cells in 2D by day 7. This is in contrast to a control breast cancer cell line, MDA-MB-231, which expresses a mesenchymal phenotype regardless of the oxygen concentration. In 3D, HT-29 cells invaded more extensively in a stiff matrix environment with corresponding increases in the invasive genes MMP2 and RAE1. This demonstrates that the physiological environment can directly impact HT-29 cells in terms of EMT marker expression and invasion, compared to an established cell line, MDA-MB-231, which has already undergone EMT. This study highlights the importance of the biophysical microenvironment to cancer epithelial cells and how these factors can direct cell behaviour. In particular, that stiffness of the 3D matrix drives greater invasion in HT-29 cells regardless of hypoxia. It is also pertinent that some cell lines (already having undergone EMT) are not as sensitive to the biophysical features of their microenvironment.