Conditional ablation of heparan sulfate expression in stromal fibroblasts promotes tumor growth in vivo

Abstract

Heparan sulfate (HS) is a glycocalyx component present in the extracellular matrix and cell-surface HS proteoglycans (HSPGs). Although HSPGs are known to play functional roles in multiple aspects of tumor development and progression, the effect of HS expression in the tumor stroma on tumor growth in vivo remains unclear. We conditionally deleted Ext1, which encodes a glycosyltransferase essential for the biosynthesis of HS chains, using S100a4-Cre (S100a4-Cre; Ext1f/f) to investigate the role of HS in cancer-associated fibroblasts, which is the main component of the tumor microenvironment. Subcutaneous transplantation experiments with murine MC38 colon cancer and Pan02 pancreatic cancer cells demonstrated substantially larger subcutaneous tumors in S100a4-Cre; Ext1f/f mice. Additionally, the number of myofibroblasts observed in MC38 and Pan02 subcutaneous tumors of S100a4-Cre; Ext1f/f mice decreased. Furthermore, the number of intratumoral macrophages decreased in MC38 subcutaneous tumors in S100a4-Cre; Ext1f/f mice. Finally, the expression of matrix metalloproteinase-7 (MMP-7) markedly increased in Pan02 subcutaneous tumors in S100a4-Cre; Ext1f/f mice, suggesting that it may contribute to rapid growth. Therefore, our study demonstrates that the tumor microenvironment with HS-reduced fibroblasts provides a favorable environment for tumor growth by affecting the function and properties of cancer-associated fibroblasts, macrophages, and cancer cells.

Classification and Molecular Functions of Heparan Sulfate Proteoglycans and Their Molecular Mechanisms with the Receptor

“…After the initial N-deacetylation/N-sulfation, all modification reactions are incompletely accomplished, resulting in various sulfation states of HS, in which HS chain composition determines HSPG-mediated cellular responses [23]. Due to the exostosis glycosyltransferase 1 (Ext1) gene mutation, primary fibroblasts express a smaller amount and shorter chain of HS than the wild-type (Wt) fibroblasts and are unable to form vinculin-containing focal adhesions compared to the Wt, which is consistent with the known role of Syndecan-4 in promoting focal adhesion formation through interaction with the fibronectin Hep II domain [25]. N-sulfation is essential for focal adhesion formation in primary rat fibroblasts plated on fibronectin in the presence of competitive heparin oligomers or variably desulfated heparin oligomers or in the absence of oligomers, and 6-O-sulfate is the next most important.…”