Expression and secretion of the pro-inflammatory cytokine IL-8 is increased in colorectal cancer cells following the knockdown of non-erythroid spectrin αII

Abstract

Non-erythroid spectrin αII (SPTAN1) expression is decreased in ~40% of cases of MLH1-deficient colorectal cancer (CRC). SPTAN1 knockdown reduces cell viability, cellular mobility and cell-cell contact formation, indicating that the SPTAN1 plays an important role in tumour growth, attachment and in regulating the tumour microenvironment. Changes in the tumour microenvironment can affect the immune response. Therefore, in the present study, proteome arrays were used to analyse the expression of 119 different chemokines and soluble receptors in CRC cell lines in which mutL homologue 1 (MLH1) or SPTAN1 were knocked down. The levels of interleukin (IL)-8 were significantly increased in the cells in which SPTAN1 was knocked down, both at the mRNA and protein level. ELISA demonstrated that the cells in which SPTAN1 was knocked down secreted increased quantities of IL-8, and chemotaxis assays revealed the enhanced trafficking of neutrophils, which was induced by media containing higher levels of IL-8. The IL-8 receptors, CRCX1 and CRCX2, were expressed in all the cell lines examined; however, their expression was not directly associated with IL-8 expression. The results of the present study thus demonstrated that CRC cells in which SPTAN1 was knocked down secreted significantly higher levels of IL-8, which in-turn increased the migration of neutrophilic granulocytes. As MLH1-deficient CRC exhibits an increased infiltration of cytotoxic T-cells and is associated with a decreased SPTAN1 expression, it can thus be hypothesized that CRC with a low SPTAN1 expression may release increased quantities of IL-8, resulting in increased immune cell infiltration.