Carbohydrate-to-carbohydrate interactions between α2,3-linked sialic acids on α2 integrin subunits and asialo-GM1 underlie the bone metastatic behaviour of LNCAP-derivative C4-2B prostate cancer cells

Complex interplays among proteins, lipids and carbohydrates can alter the phenotype and are suggested to have a crucial role in tumour metastasis. Our previous studies indicated that a complex of the GSLs (glycosphingolipids), AsGM1 (asialo-GM1), which lacks α2,3-linked sialic acid, and α2β1 integrin receptors is responsible for the metastatic behaviour of C4-2B prostate cancer cells. Herein, we identified and addressed the functional significance of changes in sialylation during prostate cancer progression. We observed an increase in α2,3-linked sialic acid residues on α2 subunits of α2β1 integrin receptors, correlating with increased gene expression of α2,3-STs (sialyltransferases), particularly ST3GAL3. Cell surface α2,3-sialylation of α2 subunits was required for the integrin α2β1-dependent cell adhesion to collagen type I and the same α2,3-linked sialic acid residues on the integrin receptor were responsible for the interaction with the carbohydrate moiety of AsGM1, explaining the complex formation between AsGM1 and α2β1 integrin receptors. These results provide novel insights into the role of sialic acids in the organization and function of important membrane components in invasion and metastatic processes

8-Prenylnaringenin, the phytoestrogen in hops and beer, upregulates the function of the E-cadherin/catenin complex in human mammary carcinoma cells

The E-cadherin/catenin complex is a powerful invasion suppressor in epithelial cells. It is expressed in the human MCF-7 breast cancer cell line family, but functionally defective in the invasive MCF-7/6 variant. Previous experiments have shown that IGF-I, tamoxifen, retinoic acid and tangeretin are able to upregulate the function of this complex in MCF-7/6 cells. We investigated the effect of 8-prenylnaringenin (8-PN), the phytoestrogen present in hops and beer, on aggregation, growth and invasion in MCF-7/6 cells. 8-PN was found to stimulate E-cadherin-dependent aggregation and growth of MCF-7/6 cells in suspension. These effects could be inhibited by the pure antiestrogen ICI 182,780.8-PN did not affect invasion of MCF-7/6 cells in the chick heart assay in vitro. In all these aspects 8-PN mimics the effects of 17 beta -estradiol on MCF-7/6 cells