Glycobiology Advance Access published online on March 17, 2009
Glycobiology, doi:10.1093/glycob/cwp040
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Compensation of loss of protein function in microsatellite-unstable colon cancer cells (HCT116): gene-dependent effect on cell surface glycan profile
1 Department of Applied Tumor Biology, Institute of Pathology, University Hospital Heidelberg, D-69120 Heidelberg, Germany
2 Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwigs-Maximilians-University Munich, D-80539 Munich, Germany
3 To whom correspondence should be adressed: Tel.: +49 6221 562683, Fax: +49 6221 562683, Email: juergen.kopitz{at}med.uni-heidelberg.de
Received on November 25, 2008; accepted on March 12, 2009
Tumors that display high level of microsatellite instability (MSI-H) accumulate somatic frameshift mutations in several genes. The compensation of this loss-of-function by transfection represents a suitable approach to tie respective gene deficiency to alterations in cellular characteristics. In view of the emerging significance of cell surface glycans as biochemical signals for presentation/activity of various receptors/integrins and for susceptibility to adhesion/growth-regulatory tissue lectins we examined the glycophenotype in the MSI-H colon cancer cell line HCT116 for activin type 2 receptor (ACVR2), absent in melanoma 2 (AIM2) and transforming growth factor β-type 2 receptor (TGFBR2) known to be associated with MSI colorectal carcinogenesis. A panel of probes specific for functional carbohydrate epitopes including human lectins was used to trace changes in cell surface levels, thereby initiating glycan analysis related to MSI. In particular, presence of core substitutions and branching in N-glycans, the sialylation status of N- and O-glycans and the presence of Lea/x-epitopes was profiled. Transient transfection affected the glycophenotype, depending on the nature of the gene and the probe. TGFBR2 presence reduced binding of probes for core substitutions and branch length in N-glycosylation, even reaching a p-value of 0.0016, ACVR2/AIM2 influenced core 1 mucin-type O-glycosylation differentially, upregulation by ACVR2 and downregulation by AIM2. These alterations of cell surface glycosylation by gene products, which are not directly associated with the machinery for glycan generation, direct attention to pursue analysis of glycosylation in MSI tumor cells on the level of target glycoproteins and open the way for functional studies.
Key words: carcinogenesis / glycosylation / lectins / malignancy / microsatellite