Tumor necrosis factor α stimulates invasion of Src-activated intestinal cells

Background & Aims: Src activation is correlated with progression of colorectal cancer (CRC). CRCs accompanied by ulcerative colitis, chronic inflammation in the colon, often have elevated Src activity, and ulcerative colitis-related CRCs are more likely to become invasive, whereas Ras activation is rarely associated with this disease. The aim of this study was to investigate the effects of a proinflammatory cytokine, tumor necrosis factor α (TNF-α), on the invasive properties of epithelial cells constitutively expressing activated Ras or Src. Methods: A cell line derived from intestinal epithelia was transfected with a v-src- or v-H-ras-expressing vector. The effect of TNF-α on morphologic changes in colonies cultured in soft agar was determined. Src protein kinase activity, peroxide production, E-cadherin expression levels, and the phosphorylation status of β-catenin and E-cadherin were determined. The invasive potential of these cells was determined by measuring cell motility and using an in vitro invasion assay. Results: TNF-α altered the colony morphology of src-, but not ras-expressing cells. TNF-α increased peroxide production, leading to Src protein expression as well as Src activity in src transfectants. Activation of Src by TNF-α led to reduced E-cadherin levels and enhanced invasion of src transfectants. Pyrrolidine dithiocarbamate and herbimycin A inhibited these effects. Conclusion: These results indicate that Src kinase activation enhances the response of epithelial cells to TNF-α leading to increased invasion through mechanisms that involve production of reactive oxygen intermediates.