Abstract 439: Interleukin-6 induces SPINK1 in colorectal cancer

Abstract

Abstract Inflammation is known to promote colorectal cancer (CRC) tumorigenesis, but the underlying molecular mechanisms are still being uncovered. Proinflammatory cytokine interleukin-6 (IL-6) stimulates growth and survival signaling in CRC cells. Inflammatory signals regulate also the production and activity of proteases and their inhibitors. Serine protease inhibitor Kazal type1 (SPINK1, aka tumor-associated trypsin inhibitor, TATI) is expressed in several tissues and over-expression of SPINK1 predicts an unfavorable outcome in many cancers, including colon cancer. The SPINK1 gene contains an IL-6 responsive element and in addition to being a protease inhibitor, it also acts as an acute phase reactant and a growth factor. The aim of this study was to assess the connection between IL-6 and SPINK1 and the effect of this signaling to growth and invasion of CRC cells. The following expression analyses and functional assays were used: quantitative PCR, immunohistochemistry, immunofluorometric assays, Western blotting, cell proliferation and migration assays. The results of this study show that CRC cell lines Colo205 and HT-29 express SPINK1 and secrete it into the culture medium. In Colo205 and HT-29 cells IL-6 dose-dependently increased the mRNA expression and protein levels of SPINK1. The baseline secretion was lower in the Colo205 cells, and significantly more IL-6 was required for the dose-dependent induction of SPINK1 expression in these cells as compared to HT-29 cells. Interestingly, in Colo205 the baseline levels of secreted tumor-associated trypsinogen-1 and -2 (TAT-1 and -2), the key targets of SPINK1 protease inhibitory action, were much higher than in HT-29 cells. In these cells IL-6 led to concomitant increase in the secretion of TAT-1 and -2, whereas in HT-29 cells the TAT-1 and -2 levels remained constantly low. IL-6 at concentrations giving the maximum SPINK1 induction did not increase the proliferation of Colo205 or HT-29 cells; however the motility of these cells was increased in response to this proinflammatory cytokine. Mechanistically, addition of IL-6 led to activation of the canonical signal transducer and activator of transcription 3 (Stat3) pathway, as indicated by Stat3 phosphorylation in both Colo205 and HT-29 cells. Taken together, our results indicate a connection between inflammatory response and increased SPINK1 levels. Elevated serum SPINK1 has been shown to be an independent prognostic factor in colon cancer. As SPINK1 acts as a growth factor in some cancers, it has also been suggested as a therapeutic target. Therefore assessment of SPINK1 expression and function has several potentially important clinical applications in colorectal and other cancers. Citation Format: Kati A. Räsänen, Laura Hautala, Ulf-Håkan Stenman, Hannu Koistinen. Interleukin-6 induces SPINK1 in colorectal cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 439. doi:10.1158/1538-7445.AM2015-439