Sialylation of cell surface glycoproteins facilitates formation of 3D multicellular prostate cancer spheroids
Prostate cancer spheroid based three-dimensional culture models (referred to as prostaspheres) have provided insight into prostate cancer biology by highlighting the importance of cell–cell interactions and the extracellular matrix in the tumor microenvironment. The prostasphere model have particular advantages over 2D monolayer culture models in terms of 3D structure and having cell-cell and cell-ECM adhesion instead of cell-culture plate adhesion. The cyclo-RGDfK(TPP) peptide-based biochemical method is a simple, reproducible and cost-effective method of spheroid formation. The cyclo-RGDfK(TPP) peptide method of spheroid formation depends on the cell surface glycoproteins, integrins and cadherins. The terminal monosaccharide of these glycoproteins is sialic acid. Using human metastatic androgen independent prostate carcinoma PC3 and DU145 cell lines and their respective gemcitabine resistant (GemR) variants, prostaspheres were generated by using cyclic Arg-Gly-Asp-D-Phe-Lys peptide modified with 4-carboxybutyl-triphenylphosphonium bromide (cyclo-RGDfK(TPP)). By using cyclo-RGDfK(TPP) peptide in a dose- and time-dependent manner, both DU145 and DU145GemR cells formed prostaspheres. In contrast, PC3 and PC3GemR cells formed irregular cell aggregates at all concentrations of cyclo-RGDfK(TPP) peptide. The formation of prostaspheres was not dependent on the level of E-cadherin expression by the prostate cancer cell lines. Using lectin cytochemistry and flow cytometry, it was found that DU145 and PC3 cells and their drug resistant variants expressed different levels of α2,3 sialic acid (SA) and α2,6 SA residues on the cell surface which correlated with the ability to form prostaspheres. Prostasphere volume was dose-dependently reduced following pretreatment with α2,6 SA specific neuraminidase (Vibrio Cholerae). Oseltamivir phosphate (OP), a neuraminidase1 inhibitor, did not have any effect on the level of sialic acid and therefore in the formation of spheroids. These results suggest that the relative levels of specific sialoglycan structures on the cell surface glycoproteins correlate with the ability of prostate cancer cells to form prostaspheres.
URI for this recordhttp://hdl.handle.net/1974/15918
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