In agreement with the well-established role of epithelial STAT3 in enhanced intestinal epithelial cell proliferation during colitis-associated tumorigenesis [44,47], elevated expression of the oncogene Cyclin D1 (a STAT3 target gene that plays a pivotal role in tumor growth [44] was detected in colonic tumors in Sdc1-KO vs. wt mice (Fig 4A left, 4B and 4C), providing a mechanistic explanation for the increased tumor burden (Fig 1B–1D). Here, STAT3 is linked to colitis.