Cell surface heparan sulfate proteoglycans control adhesion and invasion of breast carcinoma cells

Abstract

BackgroundCell surface proteoglycans interact with numerous regulators of cell behavior through their glycosaminoglycan chains. The syndecan family of transmembrane proteoglycans are virtually ubiquitous cell surface receptors that are implicated in the progression of some tumors, including breast carcinoma. This may derive from their regulation of cell adhesion, but roles for specific syndecans are unresolved.MethodsThe MDA-MB231 human breast carcinoma cell line was exposed to exogenous glycosaminoglycans and changes in cell behavior monitored by western blotting, immunocytochemistry, invasion and collagen degradation assays. Selected receptors including PAR-1 and syndecans were depleted by siRNA treatments to assess cell morphology and behavior. Immunohistochemistry for syndecan-2 and its interacting partner, caveolin-2 was performed on human breast tumor tissue arrays. Two-tailed paired t-test and one-way ANOVA with Tukey’s post-hoc test were used in the analysis of data.ResultsMDA-MB231 cells were shown to be highly sensitive to exogenous heparan sulfate or heparin, promoting increased spreading, focal adhesion and adherens junction formation with concomitantly reduced invasion and matrix degradation. The molecular basis for this effect was revealed to have two components. First, thrombin inhibition contributed to enhanced cell adhesion and reduced invasion. Second, a specific loss of cell surface syndecan-2 was noted. The ensuing junction formation was dependent on syndecan-4, whose role in promoting actin cytoskeletal organization is known. Syndecan-2 interacts with, and may regulate, caveolin-2. Depletion of either molecule had the same adhesion-promoting influence, along with reduced invasion, confirming a role for this complex in maintaining the invasive phenotype of mammary carcinoma cells. Finally, both syndecan-2 and caveolin-2 were upregulated in tissue arrays from breast cancer patients compared to normal mammary tissue. Moreover their expression levels were correlated in triple negative breast cancers.ConclusionCell surface proteoglycans, notably syndecan-2, may be important regulators of breast carcinoma progression through regulation of cytoskeleton, cell adhesion and invasion.

Insights into the key roles of proteoglycans in breast cancer biology and translational medicine

“…A number of previous studies have indicated that syndecan-2 and -4 may have some overlapping roles since they are closely related in structure [189, 249]. However, in breast carcinoma, we found that syndecan-2 suppressed syndecan-4-induced focal adhesion formation [238] and cell surface levels of syndecan-4, on the other hand, were elevated by syndecan-2 depletion, suggesting that a compensatory up-regulation had occurred. However, further experiments are required to provide an answer on how syndecan-2 controls syndecan-4 leading to downstream effects on cytoskeletal rearrangement.…”

“…Our recent data from human tissue arrays suggest that syndecan-2 is up-regulated in breast tumors and in cases where the primary tumor and metastases from the same patient could be compared, syndecan-2 was expressed at higher levels in the latter [238]. Corresponding work in tissue culture suggested that syndecan-2 has an important role in regulating breast carcinoma cell morphology and invasive behavior [238]. A single report failed to correlate syndecan-3 expression mammary carcinoma outcome.…”

“…Recent data has unveiled novel roles for syndecan-2, which is more widely known as a mesenchymal HSPG, in breast cancer progression [30, 238]. Depletion of syndecan-2 in MDA-MB-231 cells led to profound impact on cytoskeletal organization in these cells.…”

“…3D). Concomitantly, type I collagen invasion and degradation were blocked in the absence of syndecan-2 [238]. Mechanistically, syndecan-2 may signal through caveolin-2 to modulate breast carcinoma cell behavior since caveolin-2 formed a complex with syndecan-2 (but not syndecan-4).…”

Enhancing the Tumor Selectivity of a Picornavirus Virotherapy Promotes Tumor Regression and the Accumulation of Infiltrating CD8+ T Cells

“…Variations in cell surface glycosylation are observed in various cell types, providing unique functions to cells and potentially making them more or less susceptible to virus infection (31, 32). Cancer metastasis and progression are often associated with altered regulation of post-translational modifications including glycosylation (33, 34). This provides an opportunity for designing therapeutics to target these patterns, including viruses that preferentially target human cancers through their dysregulated glycosylation.…”