Project description:Various cancers such as colorectal cancer (CRC) are associated with alterations in protein glycosylation. CRC cell lines are frequently used to study these (glyco)biological changes and their mechanisms. However, differences between CRC cell lines with regard to their glycosylation have hitherto been largely neglected. Here, we comprehensively characterized the N-glycan profiles of 25 different CRC cell lines, derived from primary tumors and metastatic sites, in order to investigate their potential as glycobiological tumor model systems and to reveal glycans associated with cell line phenotypes. We applied an optimized, high-throughput membrane-based enzymatic glycan release for small sample amounts. Released glycans were derivatized to stabilize and differentiate between a2,3- and a2,6-linked N-acetylneuraminic acids, followed by N-glycosylation analysis by MALDI-TOF(/TOF)-MS. Our results showed pronounced differences between the N-glycosylation patterns of CRC cell lines. CRC cell line profiles differed from tissue-derived N-glycan profiles with regard to their high-mannose N-glycan content but showed a large overlap for complex type N-glycans, supporting their use as a glycobiological cancer model system. Importantly, we could show that the high-mannose N-glycans did not only occur as intracellular precursors but were also present at the cell surface. The obtained CRC cell line N-glycan features were not clearly correlated with mRNA expression levels of glycosyltransferases, demonstrating the usefulness of performing the structural analysis of glycans. Finally, correlation of CRC cell line glycosylation features with cancer cell markers and phenotypes revealed an association between highly fucosylated glycans and CDX1 and/or villin mRNA expression that both correlate with cell differentiation. Together, our findings provide new insights into CRC-associated glycan changes and setting the basis for more in-depth experiments on glycan function and regulation.

Project description:In collaboration with Professor Anne Dell at the South Kensington Campus of Imperial College London, we have conducted preliminary glycomic surveys of C57BL/6 CD25+ and CD25- CD4+ T cells. Cells selected in serum-containing culture medium demonstrated unusual N-glycan profiles compared to those prepared in phosphate buffered saline (PBS). These profiles were subsequently shown to result from cellular sequestration of glycoproteins present in fetal calf serum (FCS) used to supplement the medium (1). Analysis of the N-glycan profile of murine CD4+CD25+ Tregs prepared in PBS revealed distinct differences from CD4+CD25- T cells – namely, a reduction in sialic acid capping and loss of core fucose. Preliminary studies are underway to ascertain the minimum medium required to sustain general T cell survival, whilst maintaining ‘clean’ glycomic profiles. The effect of glycoprotein withdrawal on CD25+ and CD25- CD4+ T cells in culture was investigated by selecting the cells in FCS-free medium and incubating them for six hours with either FCS-containing medium, or PBS supplemented with FCS, fetuin or fetuin-derived glycans. Early apoptosis was measured using Annexin-V (BD Biosciences, Heidelberg, Germany) and late apoptosis using 7-aminoactinomycin D (7-AAD) (BD Biosciences), in parallel with a complementary apoptosis detection method – measurement of the mitochondrial membrane potential using the BD™ Mitoscreen Kit (BD Biosciences). This apoptosis staining study demonstrated that there was a remarkably higher percentage of death in both CD25+ and CD25- CD4+ T cells cultured in PBS versus cells cultured in RPMI-1640 or medium containing FCS. Both CD25+ and CD25- CD4+ T cells were highly susceptible to apoptosis in glycoprotein-free medium, demonstrating their exquisite sensitivity to the lack of glycoprotein survival factors. Continuing studies are addressing the minimum medium required to sustain cells undergoing polyclonal activation in vitro and the impact of activation on the N-glycan profiles of Tregs versus conventional T cells. To complement this work, we used Core E resources to investigate glycosyltransferase gene expression in freshly isolated versus activated C57BL/6 CD25+ and CD25- CD4+ T cells.

Dataset Information

Activation of murine CD4+ and CD8+ T lymphocytes leads to dramatic remodeling of N-linked glycans

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Activation of murine CD4+ and CD8+ T lymphocytes leads to dramatic remodeling of N-linked glycans.

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