Colorectal cancer (CRC) is one of the most commonly diagnosed cancers and can be deadly if not detected early. The incidence of early- and young-onset CRC is rapidly increasing worldwide. While CRC is characterised by a sequence of genetic events, disease progression is particularly influenced by the inflammatory status of the tissue microenvironment. Activation of Rho-associated protein kinase (ROCK) has been reported in human cancers and our lab demonstrated that conditional activation of ROCK causes tumour-promoting changes within the extracellular matrix (ECM) in cancers of the skin (Samuel et al. Cancer Cell and Kular et al. Dev Cell) and breast (Boyle et al. Nat Cell Biol). To understand the role of ROCK activity in colorectal cancer, we employed a colon-specific chemical carcinogenesis model in mice by administering a tumour initiator, Azoxymethane (AOM) systemically and an inflammation-inducing agent, dextran sodium sulfate (DSS) orally, to act as a tumour promoter. This protocol results in the formation of benign colonic polyps that progress to early carcinomas in the colon and is a well-established and characterised model of sporadic CRC.
Activating ROCK within tumour cells in this model accelerated tumourigenesis and resulted in more and larger tumours in the colon relative to control mice. These tumours had higher cellular proliferation and an altered microenvironmental profile. Within the stroma of ROCK-activated tumours, we observed increased populations of fibroblast and tumour-promoting macrophage, along with higher level of Collagen I, an ECM protein. This data suggests that ROCK activation promotes tumour progression in this sporadic CRC model partly by generating a tumour-permissive environment. To further investigate ROCK-mediated tumour progression, we have established an ex vivo culture of tumour-derived organoids (tumouroid). Initial observations demonstrated that tumouroids established from ROCK activated tumours grew larger and faster than those from the control tumours, even when ROCK is not further activated ex vivo. These suggest that ROCK activation within the tumour cells is also capable of cell-autonomously promoting persistent cellular proliferation, consistent with the in vivo data. We are currently characterising these tumouroids to understand the underlying cellular mechanisms and investigating their secretory profiles to understand how they can influence immune cells and fibroblasts using a tumour and microenvironment co-culture approach.