Src kinase pathway is involved in NFAT5-mediated S100A4 induction by hyperosmotic stress in colon cancer cells.

S100A4 is associated with the progression of many types of cancers as well as several nonmalignant conditions. However, how it is regulated by intracellular signaling and/or at the transcriptional level has not been extensively studied. We recently demonstrated that S100A4 is partially regulated by nuclear factor in activated T cell 5 (NFAT5) downstream of integrin α6β4. NFAT5 is a mammalian osmotic regulator. To study the regulation of S100A4 by NFAT5 in a more readily inducible model, colon cancer cells were subjected to hyperosmotic stress. We found that S100A4 is induced in a subset of colon cancer cell lines, and the ability to induce S100A4 depends on the methylation status of S100A4. The osmotic stress response elements were identified in the first intron region of S100A4 by S100A4 luciferase reporter assays. Depletion of NFAT5 by small interfering RNA abolished S100A4 induction. Furthermore, chromatin immunoprecipitation assays showed that NFAT5 is induced to bind to the first intron region. Inhibition of Src kinase pathways reduced S100A4 induction by affecting NFAT5 transactivation and protein levels. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to study the function of S100A4 induction in colon cancer cells under the condition of hyperosmotic stress; the results suggest that S100A4 induction contributes to cell survival. In conclusion, this study demonstrates that hyperosmotic stress induces S100A4 through NFAT5, and Src and chromatin remodeling are involved. In addition, the induction of S100A4 contributes to cell survival. Given that the gastrointestinal tract is periodically exposed to hyperosmotic stress, this study may uncover a novel signaling pathway that could contribute to GI cancer progression.