Figure 1. Factors that affect colorectal cancer metastasis.
The tumor microenvironment (TME) consists of tumor cells, resident host cells (the colonic epithelium), immune cells, endothelial cells, neurons, adipocytes, secreted factors, and the extracellular matrix (ECM). The interplay between the cells within the TME and the tumor cells, as well as the interplay between the gut microbiome and the tumor cells, regulate tumor invasion and metastasis (namely, intravasation into blood vessels). Changes in the expression of epithelial-mesenchymal transition (EMT) genes occur within the subset of tumor cells that acquire metastatic properties. Abbreviations: MIC, metastasis-initiating cell; HRC, high-relapse cell; EMP1, epithelial membrane protein 1; MMP, matrix metalloproteinase; CAF, cancer-associated fibroblast; TAM, tumor-associated macrophage; T-reg, regulatory T-cell; TGF-β, transforming growth factor-β. Arrows pointing to the tumor indicate tumor-promoting effect.
