We observed syndecan-4 to be a dominant HSPG on DCs, especially upon stimulation with LPS (Figure 3A). Human monocyte-derived DCs express a complex array of syndecans and glypicans that change with their degree of maturation [52]. Increased maturation of human monocyte-derived DCs (including Langerhans cells) has been noted to occur with a shift from dominant syndecan-1 expression to that of syndecan-4 [25]. In our expression studies, syndecan-4 along with syndecan-1 (to a lesser degree) was significantly increased in association with exposure to maturation stimuli, including LPS (Figure 3A) as well as TNFα (Supplemental Figure S4). Interestingly, when we looked specifically at DCs deficient in syndecan-4, we also noted a significant increase in maturation markers MHCII, CD86, and CCR7 along with a decrease in antigen uptake. These findings emphasize that both HS and major HS core proteins on DCs play important roles in the regulation of DC maturation (Figures 2 and 3). Intriguingly, a recent report examines the effect of genetic deficiency in syndecan-4 on reduced pathologic DC migration associated with an asthma model [24]. This is consistent with our findings of slowed lymphatic-directed DC trafficking with a DC-directed mutation in the HS chain itself (Figures 1, A and B, and 5B). In our studies following discovery that Sdc4 was strongly expressed (especially upon LPS stimulation) in marrow-derived DCs, we found relative hypermaturation in DCs isolated from the the mutants, a phenotype which may be causally associated with altered migration. In this regard, by genetically targeting sulfation of the glycan “business end” of proteoglycans on DCs (i.e., moiety that directly interacts with chemokines and/or receptor ternary complexes), the result is both slowed lymphatic-directed DC migration as well as increased DC maturation. It is possible that exposure of classic DCs to maturation stimuli, including some that are expressed in tumor microenvironment, is associated with a regulatory rise in Sdc4 expression (Figure 3A and Supplemental Figure S4) as a secondary or homeostatic response. Regardless, genetic ablation in Sdc4 expression appears to be sufficient to promote maturation independent of a key DC-maturation ligand such as LPS (Figure 3B). Moreover, our findings also point to the likelihood that the DC phenotype resulting from such glycan targeting may inhibit pathologic immunosuppressive effects of tolerogenic-DC migration and immaturity on tumor growth (Figure 5).