Tu1679 Role of ST2 and Its Ligand, IL-33, in Colon Cancer

The importance of inflammation in cancer is now well established, with cytokines produced by both immune cells and tumor cells affecting neoplastic progression. The role of the cytokine, IL-33, in cancer is unclear. IL-33 was recently identified as the ligand for ST2. ST2 is a member of the toll-like receptor/IL-1 receptor family. Three isoforms of ST2 exist: a trans-membrane receptor (ST2L), a secreted soluble form (sST2), and a variant form (ST2V). The IL-33/ST2 pathway has been implicated in inflammatory bowel disease, a major risk factor for colon cancer. Aim(s): To investigate the role of IL-33 and ST2 in colon cancer. Method(s): ST2 and IL-33 expression was detected by real-time RT-PCR, Western blotting and immunofluorescence in HT29, SW480 and CT26 colon tumor cells. Chemokine expression was detected by real-time RT-PCR. Formalin fixed paraffin embedded blocks of colorectal cancer were retrieved from the archives of Cork University Hospital, and ST2V and ST2L expression characterized by immunohistochemistry. Cell proliferation was assessed by resazurin reduction, while cell migration towards 10% serum was detected using a transwell migration assay. Result(s): Colon cancer cells express ST2 and IL-33 in vitro, with expression increased by the inflammatory mediators (LPS, TNFalpha and PGE2). Characterization of human colon tumours in vivo revealed that both normal and neoplastic cells expressed ST2V, with no difference in the intensity or pattern of expression. However, neoplastic cells showed increased cytoplasmic staining of ST2L (16/24) as compared to adjacent non-tumor cells which had negligible ST2L expression. Functional analyses showed that stimulation with IL-33 induced the expression of CXCL-1, a murine IL-8 homologue, by CT26 cells in a dose dependent manner. IL-33 also induced IL-8 expression by HT29 cells. Cell proliferation was not affected by IL-33. In contrast, stimulation with IL-33 increased migration of HT29 and CT26 cells towards 10% serum. Conclusion(s): Our results indicate that the IL-33/ST2 signalling axis may play an important role in colon carcinogenesis. Whether manipulation of this pathway represents a potential therapeutic target merits further investigation.