Novel experimental model of colorectal cancer tumourigenesis

▸ Chen HJ, Wei Z, Sun J, et al. A recellularized human colon model identifies cancer driver genes. Nat Biotechnol 2016;34:845–51.

Modelling human colonic cancer is challenging. Cell lines, organoids and animal models provide some understanding, but they all have major flaws. This recent paper has described a model of the human colon using recellularised matrix colonised with other native cells to reconstruct the colon and maintain it in viable culture for long enough to perform meaningful experiments. The process of recellularisation began with treating a 5 cm³ piece of resected human colon with powerful detergents to create a matrix containing <5% of original DNA content. The mucosa and submucosa were separated to allow access to the empty crypt space. The authors immortalised normal human colonic epithelial organoids, endothelial cells and myofibroblasts with human telomere reverse transcriptase to prevent senescence. The organoids showed no evidence of cancer driver mutations. The authors then injected the endothelial cells into the matrix and, when they began to proliferate, pipetted the organoids onto the mucosal surface and gravity settled the organoids into the crypt spaces. The myofibroblasts were then added, and the mucosa and submucosa rejoined. The organoids formed viable crypts, where Lgr5⁺ stem cells were located at the base, produced proliferative differentiated progeny and demonstrated homeostatic Wnt signalling. To demonstrate the potential of using this model to study cancer, the authors performed stepwise mutagenesis to reflect the traditional view of tumour development: one mutation at a time, involving APC, KRAS and finally exposing them to a TGFβR1 inhibitor to mimic mutant SMAD4 behaviour. The mutated recellularised crypts were capable of intramucosal growth through the basement membrane and invasion through the muscularis mucosae. There is absence of several cell types (eg, immune cells) that also play an important role in tumourigenesis. …