The Sda Synthase B4GALNT2 Reduces Malignancy and Stemness in Colon Cancer Cell Lines Independently of Sialyl Lewis X Inhibition

Background: The Sd^a antigen and its biosynthetic enzyme B4GALNT2 are highly expressed in healthy colon but undergo a variable down-regulation in colon cancer. The biosynthesis of the malignancy-associated sialyl Lewis x (sLe^x) antigen in normal and cancerous colon is mediated by fucosyltransferase 6 (FUT6) and is mutually exclusive from that of Sd^a. It is thought that the reduced malignancy associated with high B4GALNT2 was due to sLe^x inhibition. Methods: We transfected the cell lines SW480 and SW620, derived respectively from a primary tumor and a metastasis of the same patient, with the cDNAs of FUT6 or B4GALNT2, generating cell variants expressing either the sLe^x or the Sd^a antigens. Transfectants were analyzed for growth in poor adherence, wound healing, stemness and gene expression profile. Results: B4GALNT2/Sd^a expression down-regulated all malignancy-associated phenotypes in SW620 but only those associated with stemness in SW480. FUT6/sLe^x enhanced some malignancy-associated phenotypes in SW620, but had little effect in SW480. The impact on the transcriptome was stronger for FUT6 than for B4GALNT2 and only partially overlapping between SW480 and SW620. Conclusions: B4GALNT2/Sd^a inhibits the stemness-associated malignant phenotype, independently of sLe^x inhibition. The impact of glycosyltransferases on the phenotype and the transcriptome is highly cell-line specific.

Reduced expression of E-cadherin and increased sialylation level in clear cell renal cell carcinoma

Cancer cells are characterized by an aberrant increase in protein N-glycosylation and by disruption of E-cadherin-mediated adherens junctions. However, the relationship between alterations in N-glycosylation process and loss of E-cadherin adhesion in cancer remains unclear. The mechanisms of altered expression of adhesive glycoproteins in cancer cells have not been fully elucidated. Thus, the aim of this study was to examine the expression of E-cadherin and sialyl Lewis^a/^x, NeuAcα2-3Gal, NeuAcα2-6Gal/GalNAc structures in the normal renal tissue and intermediate and cancerous tissues from patients with clear cell RCC. Moreover, we attempted to correlate the E-cadherin expression with some specific sugar residues of renal cancer tissue glycoproteins. The expression of E-cadherin was analysed using ELISA test and immunoblotting. Oligosaccharide structures and sialylation level were detected with ELISA test using specific biotinylated lectins or antibodies. A significant decrease of E-cadherin expression as well as a significant increase in sialylated oligosaccharides level in intermediate zone and renal cancer tissue in comparison to normal renal tissue are reported. Significant decrease in expression of cadherins and increase in sialylation of oligosaccharide structures in renal cancer tissue in comparison to normal renal tissue, and in renal cancer tissue in comparison to intermediate zone of renal tissue, are important for the future research concerning detection and quantification of cadherins and sialylated oligosaccharide structures in urine and cells of urinary sediment as possible non-invasive marker of early RCC.

Glycosyltransferases involved in the synthesis of MUC-associated metastasis-promoting selectin ligands

The sialyl Lewis a and x (sLe(a/x)) antigens frequently displayed on the surface of tumor cells are involved in metastasis. Their synthesis has been attributed to altered expression of selective glycosyltransferases. Identification of these glycosyltransferases and the glycoproteins that carry these carbohydrate antigens should help advance our understanding of selectin-mediated cancer metastasis. In this study, quantitative real-time polymerase chain reaction analysis coupled with in situ proximity ligation assay and small interference RNA treatment shows involvement of β3galactosyltransferase-V in the synthesis of MUC16-associated sLe(a) in H292 cells. Also, α3fucosyltransferase-V, which is absent in BEAS-2B human immortalized bronchial epithelial cells and A549 lung carcinoma cells, participates in the synthesis of MUC1-associated sLe(x) in CFT1 human immortalized bronchial epithelial cells and H292 lung carcinoma cells. Neither selectin ligand is found on MUC1 in BEAS-2B and A549 cells. Knockdown of either enzyme suppresses migration, and selectin tethering and rolling properties of H292 cells under dynamic flow as determined by wound healing and parallel plate flow chamber assays, respectively. These results provide insights into how the synthesis of mucin-associated selectin ligands and the metastatic properties of cancer cells can be regulated by selective glycosyltransferases that work on mucins. They may help develop novel anticancer drugs.