Gastric Cancer Cell Glycosylation as a Modulator od the ErbB2 Oncogenic Receptor

Cell surface receptor tyrosine kinases (RTKs) play a central role in the initiation, promotion and progression of multiple human cancers, by triggering the aberrant activation of downstream signaling pathways implicated in malignant cell phenotype and behavior. In particular, overexpression of the human epidermal growth factor 2 (ErbB2) RTK constitutes a well-established molecular driver of carcinogenesis. RTK maturation is tightly regulated by protein N-linked glycosylation. However, ErbB2’s detailed glycosylation landscape, and the molecular role mechanism through which it actively shifts receptor’s signaling functions towards malignancy in GC cells, require further elucidation. In this publication, the authors characterized ErbB2 glycosylation profile in an in vitro model system of ErbB2-positive GC, and identified this RTK as a previously unreported protein carrier of the tumor-associated endothelial selectin ligand sialyl Lewis a (SLe^a) antigen. Additionally, the authors show that specifically blocking this glycan epitope in ErbB2 overexpressing cells abruptly disrupts ErbB2 expression and activation.

Authors and Affiliations:

Henrique O. Duarte^1,2,3, Meritxell Balmaña^1,2, Stefan Mereiter^1,2, Hugo Osório^1,2,4, Joana Gomes^1,2 and Celso A. Reis^1,2,3,4

¹Institute for Research and Innovation in Health (i3S), University of Porto, 4200-135 Porto, Portugal

²Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), 4200-135 Porto, Portugal

³Instituto de Ciências Biomédicas Abel Salazar (ICBAS), University of Porto, 4050-313 Porto, Portugal

⁴Faculty of Medicine of the University of Porto, 4200-319 Porto, Portugal

Abstract:

Aberrant expression and hyperactivation of the human epidermal growth factor receptor 2 (ErbB2) constitute crucial molecular events underpinning gastric neoplastic transformation. Despite ErbB2 extracellular domain being a well-known target for glycosylation, its glycosylation profile and the molecular mechanisms through which it actively tunes tumorigenesis in gastric cancer (GC) cells remain elusive. We aimed at disclosing relevant ErbB2 glycan signatures and their functional impact on receptor’s biology in GC cells. The transcriptomic profile of cancer-relevant glycosylation enzymes, and the expression and activation of the ErbB receptors were characterized in four GC cell lines. Cellular- and receptor-specific glycan profiling of ErbB2-overexpressing NCI-N87 cells unveiled a heterogeneous glycosylation pattern harboring the tumor-associated sialyl Lewis a (SLe^a) antigen. The expression of SLe^a and key enzymes integrating its biosynthetic pathway were strongly upregulated in this GC cell line. An association between the expression of ERBB2 and FUT3, a central gene in SLe^a biosynthesis, was disclosed in GC patients, further highlighting the crosstalk between ErbB2 and SLe^a expression. Moreover, cellular deglycosylation and CA 19.9 antibody-mediated blocking of SLea drastically altered ErbB2 expression and activation in NCI-N87 cells. Altogether, NCI-N87 cell line constitutes an appealing in vitro model to address glycan-mediated regulation of ErbB2 in GC.

Journal: International Journal of Molecular Sciences, Volume 18, Issue 11

Link: http://www.mdpi.com/1422-0067/18/11/2262