The clinical performance of the therapeutic monoclonal antibody trastuzumab in the treatment of ErbB2-positive unresectable gastric cancer (GC) is severely hampered by the emergence of molecular... Show moreThe clinical performance of the therapeutic monoclonal antibody trastuzumab in the treatment of ErbB2-positive unresectable gastric cancer (GC) is severely hampered by the emergence of molecular resistance. Trastuzumab's target epitope is localized within the extracellular domain of the oncogenic cell surface receptor tyrosine kinase (RTK) ErbB2, which is known to undergo extensive N-linked glycosylation. However, the site-specific glycan repertoire of ErbB2, as well as the detailed molecular mechanisms through which specific aberrant glycan signatures functionally impact the malignant features of ErbB2-addicted GC cells, including the acquisition of trastuzumab resistance, remain elusive. Here, we demonstrate that ErbB2 is modified with both alpha 2,6- and alpha 2,3-sialylated glycan structures in GC clinical specimens. In-depth mass spectrometry-based glycomic and glycoproteomic analysis of ErbB2's ectodomain disclosed a site-specific glycosylation profile in GC cells, in which the ST6Gal1 sialyltransferase specifically targets ErbB2 N-glycosylation sites occurring within the receptor's trastuzumab-binding domain. Abrogation of ST6Gal1 expression reshaped the cellular and ErbB2-specific glycomes, expanded the cellular half-life of the ErbB2 receptor, and sensitized ErbB2-dependent GC cells to trastuzumab-induced cytotoxicity through the stabilization of ErbB dimers at the cell membrane, and the decreased activation of both ErbB2 and EGFR RTKs. Overall, our data demonstrates that ST6Gal1-mediated aberrant alpha 2,6-sialylation actively tunes the resistance of ErbB2-driven GC cells to trastuzumab. Show less
Background The epidermal growth factor receptor (EGFR) is a key protein involved in cancer development. Monoclonal antibodies targeting EGFR are approved for the treatment of metastatic colorectal... Show moreBackground The epidermal growth factor receptor (EGFR) is a key protein involved in cancer development. Monoclonal antibodies targeting EGFR are approved for the treatment of metastatic colorectal cancer (CRC). Despite the beneficial clinical effects observed in subgroups of patients, the acquisition of resistance to treatment remains a major concern. Protein N-glycosylation of cellular receptors is known to regulate physiological processes leading to activation of downstream signaling pathways. In the present study, the role of EGFR-specific terminal alpha 2,6-sialylation was analyzed in modulation of the malignant phenotype of CRC cells and their resistance to monoclonal antibody Cetuximab-based therapy.Methods Glycoengineered CRC cell models with specific sialyltransferase ST6GAL1 expression levels were applied to evaluate EGFR activation, cell surface glycosylation and therapeutic response to Cetuximab.Results Glycoproteomic analysis revealed EGFR as a major target of ST6Gal1-mediated alpha 2,6-sialylation in a glycosite-specific manner. Mechanistically, CRC cells with increased ST6Gal1 expression and displaying terminal alpha 2,6-sialylation showed a marked resistance to Cetuximab-induced cytotoxicity. Moreover, we found that this resistance was accompanied by downregulation of EGFR expression and its activation.Conclusions Our data indicate that EGFR alpha 2,6-sialylation is a key factor in modulating the susceptibility of CRC cells to antibody targeted therapy, thereby disclosing a potential novel biomarker and providing key molecular information for tailor made anti-cancer strategies. Show less
We compared and contrasted 11 European case studies to identify challenges and opportunities toward the operationalization of marine and coastal ecosystem service (MCES) assessments in Europe. This... Show moreWe compared and contrasted 11 European case studies to identify challenges and opportunities toward the operationalization of marine and coastal ecosystem service (MCES) assessments in Europe. This work is the output of a panel convened by the Marine Working Group of the Ecosystem Services Partnership in September 2016. The MCES assessments were used to (1) address multiple policy objectives simultaneously, (2) interpret EU-wide policies to smaller scales and (3) inform local decision-making. Most of the studies did inform decision makers, but only in a few cases, the outputs were applied or informed decision-making. Significant limitations among the 11 assessments were the absence of shared understanding of the ES concept, data and knowledge gaps, difficulties in accounting for marine social–ecological systems complexity and partial stakeholder involvement. The findings of the expert panel call for continuous involvement of MCES ‘end users’, integrated knowledge on marine social–ecological systems, defining thresholds to MCES use and raising awareness to the general public. Such improvements at the intersection of science, policy and practice are essential starting points toward building a stronger science foundation supporting management of European marine ecosystems. Show less
