Exploring the effects of tissue structural cell and tumor cell heparan sulfate on immune system trafficking, activation, and intercommunication via amphiregulin

Abstract

Abstract Heparan sulfate (HS), a glycan subtype, is ubiquitously present on the surface of structural tissue cells and tumor cells during homeostasis, disease, and cancer, but how it affects immune cell trafficking, activation, and signal transmission in these tissue contexts is poorly understood. Furthermore, amphiregulin (Areg), a growth factor used by immune cells for intercommunication with structural tissue and tumor cells, contains a HS binding domain. We investigated the downstream signaling modalities of Areg-mediated cell activation in the context of HS inhibition. Areg signaling is qualitatively altered, but still present, upon exogenous inhibition or genetic ablation of HS. We further probed the consequences of HS-dependent vs. -independent Areg signaling at the transcriptional level. Next, we used a panel of CRISPR-Cas9-mediated knockout Lewis Lung Carcinoma (LLC) cell lines to interrogate how various aspects of HS (core proteoglycan, HS chain extension, sulfation status) contribute to Areg signaling. We found that the presence of the glypican family of HS-harboring proteoglycans on the surface of cells is critical for Areg signaling. Lastly, we explored the effects of cancer cell HS on immune system trafficking to and activation within tumors. HS-deficient tumors experience similar levels of lymphoid cell trafficking and activation, but show a significant increase in the presence of certain myeloid cell type (neutrophils, monocytes, and macrophages). Additionally, tumor-associated macrophages within HS-deficient tumors show an altered phenotype, with increased maturation markers. Overall, our work has illuminated previously understudied aspects of the relationships between HS, Areg, and the immune system. Supported by a grant from NIH (R21-AI149657)