Tumour Necrosis Factor-Alpha (TNF-α)-Induced Metastatic Phenotype in Colorectal Cancer Epithelial Cells: Mechanistic Support for the Role of MicroRNA-21

SIMPLE SUMMARY: The progression of colorectal cancer is promoted by changes in the genetic makeup of tumour cells giving them potential to leave the site of their origin to seed new metastatic tumours in other tissue; inflammation at the tumour site is a driver of these changes. Tumour necrosis factor-alpha is a pro-inflammatory molecule that is associated with the progression of metastatic cancer. Small biologically active RNAs, microRNAs, target the production of specific proteins and are proposed as agents of tumour change. One agent, microRNA-21, shown to be present in colorectal cancer, is known to target the formation of proteins involved in metastatic changes in cells. We investigated the relationship between TNF-α and microRNA-21 in colorectal cancer cells and show their involvement in promoting cell changes indicative of the metastatic state. In summary, we provide mechanistic support for a role of microRNA-21 in tumour necrosis factor-alpha promotion of cancer cell metastatic change. ABSTRACT: Colorectal cancer is driven by genetic and epigenetic changes in cells to confer phenotypes that promote metastatic transformation and development. Tumour necrosis factor-alpha (TNF-α), a pro-inflammatory mediator, regulates cellular communication within the tumour microenvironment and is associated with the progression of the metastatic phenotype. Oncogenic miR-21 has been shown to be overexpressed in most solid tumours, including colorectal cancer, and is known to target proteins involved in metastatic transformation. In this study, we investigated the relationship between TNF-α and miR-21 regulation in colorectal cancer epithelial cells (SW480 and HCT116). We observed that TNF-α, at concentrations reported to be present in serum and tumour tissue from colorectal cancer patients, upregulated miR-21 expression in both cell lines. TNF-α treatment also promoted cell migration, downregulation of the expression of E-cadherin, a marker of epithelial to mesenchymal transition, and anti-apoptotic BCL-2 (a validated target for miR-21). Knockdown of miR-21 had the opposite effect on each of these TNF-a induced phenotypic changes. Additionally, in the SW480 cell line, although TNF-α treatment selectively induced expression of a marker of metastatic progression VEGF-A, it failed to affect MMP2 expression or invasion activity. Our data indicate that exposing colorectal cancer epithelial cells to TNF-α, at concentrations occurring in the serum and tumour microenvironment of colorectal cancer patients, upregulated miR-21 expression and promoted the metastatic phenotype.