GOLGI PHOSPHOPROTEIN 3 EXPRESSION IS ASSOCIATED WITH GLYCOSPHINGOLIPID COMPOSITION OF HUMAN BREAST CANCER CELL LINES

MARIA NATALIA MARTINEZ; RUGGIERO, FERNANDO ; FIDELIO, GERARDO; VILCAES, ALEJANDRO

Congreso; Congreso conjunto SAIB-SAMIGE 2021; 2021

Glycosphingolipids (GSLs) are mainly concentrated at the cell surface of eukaryotic cell. The expression levels of selective species of GSLs can dynamically change during different cellular processes. Aberrant and elevated expression of gangliosidesat cell surface has been also shown on different types of cancer cells. Golgi phosphoprotein 3 (GOLPH3), a peripheral membrane protein mainly localized at the trans-Golgi network, has been associated with poor prognosis in many cancers; however, its precise function in cancer is not fully understood. In addition, it has been proposed that GOLPH3 is required for the localization of glycosyltransferases in Golgi, mediating the synthesis of glycolipids, a feature that may contribute to its oncogenic trait. In order to explore the role of GOLPH3 in the metabolism of GSLs, we first analyzed the effect of knockingdown GOLPH3 expression on the mRNA levels of glycosyltransferases in tumorigenic and non-tumorigenic human breast cells with different patterns of GSLs. The results showed that the expression of GOLPH3 did not have a remarkable effect on transcription of glycosyltransferases. Next, immunofluorescence studies in two breast cancer cell lines (MDA-MB-231 and MCF7, with high levels of GOLPH3), revealed that both cell lines expressed the glycolipid GM1, while GD1a was detected in MCF7 but not in MDA-MB-231 cell line. In addition, the globoside SSEA-4 was present in MDA-MB-231 cells but not in MCF7 cells. In GOLPH3 knockdown MCF7 cells, there was a reduction in the levels of GD1a ganglioside with a concomitant increment of GM1 ganglioside, indicating a specific effect of GOLPH3 in the expression of GD1a. Of note, synthesis of SSEA-4 and GD1a is carried out by the same glycosyltransferase, ST3Gal-II. Moreover, SSEA-4 positive cells have increased mesenchymal markers and reduced epithelial markers expression, suggesting a participation of SSEA-4 in the acquisition of a migratory phenotype. Therefore, we studied the effect of GOLPH3 on the process of epithelial mesenchymal transition (EMT) induced by transforming growth factor-β (TGF-β) in MCF7 and MDA-MB-231 cells. Preliminary results showed that TGF-β treatment induced an increase in the expression of GOLPH3 in both cell lines. In addition, SSEA-4 globoside levels were also increased in MDA-MB-231 cells after TGF-β treatment. Future experiments are required to confirm the concomitant increasement of GM1 and GD1a levels with SSEA-4 and GOLPH3 expression. In GOLPH3 knockdown cells, the treatment with TGF-β did not induce EMT. Also, wound-healing assays in MDA-MB-231 cells indicated that the expression of GOLPH3 impairs the migration capacity. Taken together, these results support the idea that GOLPH3 expression is involved in the expression pattern of GSLs of breast cancer cellular lines.