Cancer invasion regulates vascular complexity in a three-dimensional biomimetic model.

There is a growing appreciation for including a complex, vascularised stroma in three-dimensional (3D) tumour models to recapitulate the native tumour microenvironment in situ.Using a compartmentalised, biomimetic, 3D cancer model, comprising a central cancer mass surrounded by a vascularised stroma, we have tested the invasive capability of colorectal cancer cells.We show histological analysis of dense collagen I/laminin scaffolds, forming necrotic cores with cellular debris. Furthermore, cancer cells within this 3D matrix form spheroids, which is corroborated with high EpCAM expression. We validate the invasive growth of cancer cells into the stroma through quantitative image analysis and upregulation of known invasive gene markers, including metastasis associated in colon cancer 1, matrix metalloproteinase 7 and heparinase. Tumouroids containing highly invasive HCT116 cancer masses form less complex and less branched vascular networks, recapitulating 'leaky' vasculature associated with highly metastatic cancers. Angiogenic factors regulating this were vascular endothelial growth factor A and hepatocyte growth factor active protein. Where vascular networks were formed with less invasive cancer masses (HT29), higher expression of vascular endothelial cadherin active protein resulted in more complex and branched networks. To eliminate the cell-cell interaction between the cancer mass and stroma, we developed a three-compartment model containing an acellular ring to test the chemoattractant pull from the cancer mass. This resulted in migration of endothelial networks through the acellular ring accompanied by alignment of vascular networks at the cancer/stroma boundary.This work interrogates to the gene and protein level how cancer cells influence the development of a complex stroma, which shows to be directly influenced by the invasive capability of the cancer.