Dissection of N-, O- and glycosphingolipid glycosylation changes in PaTu-S pancreatic adenocarcinoma cells upon TGF-β challenge

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is characterized by poor prognosis and high mortality. Transforming growth factor-β (TGF-β) plays a key role in tumor progression, which is often associated with aberrant glycosylation. How PDAC cells respond to TGF-β and the role of glycosylation therein is, however, not well known. Here, we investigated the TGF-β-mediated response and glycosylation changes in SMAD4-deficient PaTu-8955S (PaTu-S) cell line. PaTu-S cells responded to TGF-β by upregulating SMAD2 phosphorylation and target gene expression. TGF-β induced expression of the mesenchymal marker N-cadherin, but did not significantly affect epithelial marker E-cadherin expression. The differences of N-glycans, O-glycans and glycosphingolipid (GSL) glycans in PaTu-S cells with TGF-β stimulation were examined. TGF-β treatment primarily induced N-glycome aberrations involving elevated levels of branching, core fucosylation, and sialylation in PaTu-S cells, in line with TGF-β-induced changes in the expression of glycosylation-related genes. In addition, we observed differences in O- and GSL-glycosylation profiles after TGF-β treatment, including lower levels of sialylated Tn antigen, and neoexpression of globosides. Furthermore, SOX4 expression was upregulated upon TGF-β stimulation, and its depletion blocked the TGF-β-induced N-glycomic changes. Thus, our study provides a mechanism by which TGF-β-induced N-glycosylation changes in SOX4 dependent and SMAD4 independent manner in pancreatic cancer cells. Our results open up avenues to study the relevance of glycosylation in TGF-β signaling in SMAD4 inactivated PDAC.