3D bioprinted colon model for anticancer drug testing

Colorectal adenocarcinoma (CRAC) is the third most commonly diagnosed form of cancer in the world and the second leading cause of cancer deaths. This type of cancer originates from the epithelial cells of the colorectal mucosa, it usually starts from the inner lining and afterwards spreads to other layers and it is normally characterized by glandular formation. The recommended treatment typically consists of resection if the tumor is at an early-stage and chemotherapy or radiotherapy in case the cancer is at a more advanced stage. However, most therapeutic approaches appear challenging because of the molecular and functional heterogeneity shown by these tumors, making it difficult for clinicians to come up with an adequate treatment plan. Moreover, the absence of reliable cellular models mimicking the disease make drug screening very costly and time-consuming. The lack of consistency and prediction capability of 2D models and animal models have made the enhancement of effective drug screening methods of paramount importance. In this regard, the development of a 3D model would allow to reproduce cell morphology and cell-matrix interactions and are more physiologically suitable to predict drug response in the case of complex heterogenic cancers. On top of that, the use of bioprinting and microfluidic technology further eases the creation of truly biomimetic tissue models leading to a more appropriate prediction of drug interactions. The aim of this work is to create a more biomimetic in vitro model of colorectal tissue adenocarcinoma by means of bioprinting. The fabrication of a high-content in vitro CRAC model was obtained through a multichannel coaxial extrusion bioprinting method for printing hollow tubes where calcium chloride and a bio-ink consisting of gelatin and sodium alginate flow coaxially. The hollow tubes were then used to seed CACO-2 cells, a cell-line used to mimic the small intestine by forming epithelial monolayers. It was shown that not only patient-derived CACO-2 cells can be maintained in a 3D bioprinted microenvironment for over 7 days, but they proliferated and aggregated properly, showing spontaneous 3D morphogenesis of the human intestinal epithelium without any external stimuli. In addition, functional biomarker expression was shown through immunostaining assays. Finally, the bioprinted 3D constructs were used for testing some of the most common chemotherapeutic drugs in order to assess the reliability of the model as far as reproducing human colorectal adenocarcinoma tissue.