Stromal heparan sulfate differentiates neuroblasts to suppress neuroblastoma growth.

Neuroblastoma prognosis is dependent on both the differentiation state and stromal content of the tumor. Neuroblastoma tumor stroma is thought to suppress neuroblast growth via release of soluble differentiating factors. Here, we identified critical growth-limiting components of the differentiating stroma secretome and designed a potential therapeutic strategy based on their central mechanism of action. We demonstrated that expression of heparan sulfate proteoglycans (HSPGs), including TßRIII, GPC1, GPC3, SDC3, and SDC4, is low in neuroblasts and high in the Schwannian stroma. Evaluation of neuroblastoma patient microarray data revealed an association between TGFBR3, GPC1, and SDC3 expression and improved prognosis. Treatment of neuroblastoma cell lines with soluble HSPGs promoted neuroblast differentiation via FGFR1 and ERK phosphorylation, leading to upregulation of the transcription factor inhibitor of DNA binding 1 (ID1). HSPGs also enhanced FGF2-dependent differentiation, and the anticoagulant heparin had a similar effect, leading to decreased neuroblast proliferation. Dissection of individual sulfation sites identified 2-O, 3-O-desulfated heparin (ODSH) as a differentiating agent, and treatment of orthotopic xenograft models with ODSH suppressed tumor growth and metastasis without anticoagulation. These studies support heparan sulfate signaling intermediates as prognostic and therapeutic neuroblastoma biomarkers and demonstrate that tumor stroma biology can inform the design of targeted molecular therapeutics.

Heparan sulfate signaling in cancer.

Heparan sulfate (HS) is a biopolymer consisting of variably sulfated repeating disaccharide units. The anticoagulant heparin is a highly sulfated intracellular variant of HS. HS has demonstrated roles in embryonic development, homeostasis, and human disease via non-covalent interactions with numerous cellular proteins, including growth factors and their receptors. HS can function as a co-receptor by enhancing receptor-complex formation. In other contexts, HS disrupts signaling complexes or serves as a ligand sink. The effects of HS on growth factor signaling are tightly regulated by the actions of sulfyltransferases, sulfatases, and heparanases. HS has important emerging roles in oncogenesis, and heparin derivatives represent potential therapeutic strategies for human cancers. Here we review recent insights into HS signaling in tumor proliferation, angiogenesis, metastasis, and differentiation. A cancer-specific understanding of HS signaling could uncover potential therapeutic targets in this highly actionable signaling network.