Effect of alpha 2,6 sialylation on integrin-mediated adhesion of breast cancer cells to fibronectin and collagen IV

Aims: To determine the role of sialylation on alpha 5 beta 1 and alpha 2 beta 1 integrins in the regulation of adhesion between breast cancer cells and extracellular matrix (ECM). Main methods: Static cell adhesion assays were performed to quantify avidity of breast cancer cells to ECM. The effects of sialiclases on alpha 2,6 sialylation was assessed by flow cytometry using biotin conjugated Sambucus nigra lectin. Lectin affinity assays were used to determine expression of alpha 2,6 sialylated integrins. Cell migration and invasion were investigated by wound healing and transwell invasion assays. Key findings: alpha 2, alpha 5 and beta 1 integrins had considerable alpha 2,6 sialylation on MDA-MB-231 cells, whereas signals from MCF-7 cells were undetectable. Cleavage of alpha 2,6 sialylation increased adhesion of MDA-MB-231 cells to ECM, while adhesion of MCF-7 cells was unaffected, consistent with the latter's lack of endogenous alpha 2,6 sialylated surface integrins. Neither surface expression of alpha 2 beta 1 and alpha 5 beta 1 integrins, nor activated beta 1 integrin, changed in MDA-MB-231 cells after sialidase treatment. However, sialidase treatment did not have significant impact on migration or invasion of MDA-MB-231 cells. Significance:Cell adhesion is an important early step of cancer metastasis, yet the roles of sialylation in regulating integrin-mediated breast cancer cell adhesion in comparison to migration and invasion are not well-understood. Our data suggest desialylation of alpha 2,6-sialylated integrins increases adhesion, but not migration or invasion, of MDA-MB-231 cells to ECM without altering integrin expression. It should be considered that alpha 2,6 sialylation may play different roles in regulating cell adhesion of different cancer cells when developing potential therapeutics targeting alpha 2,6 sialylation. Published by Elsevier Inc.