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

MARTINEZ, NATALIA; FERNANDO M. RUGGIERO; FIDELIO, GERARDO; A. ALEJANDRO VILCAES

Congreso; LVII SAIB Meeting - XVI SAMIGE Meeting; 2021

SAIB - SAMIGE

Glycosphingolipids(GSLs) are mainly concentrated at the cell surface of eukaryotic cell. The expression levels of selectivespecies of GSLs can dynamically change during different cellular processes. Aberrantand elevated expression of gangliosides at cell surface has been also shown ondifferent types of cancer cells. Golgi phosphoprotein 3 (GOLPH3), a peripheral membrane protein mainlylocalized at the trans-Golgi network, has been associated with poor prognosisin many cancers; however, its precise function in cancer is not fullyunderstood. In addition, it has been proposedthat GOLPH3 is required for the localization of glycosyltransferases in Golgi,mediating the synthesis of glycolipids, a feature that may contribute to itsoncogenic trait. In order to explore the role of GOLPH3 in the metabolism of GSLs, we first analyzed the effect of knocking-down GOLPH3expression on the mRNA levels of glycosyltransferases in tumorigenic andnon-tumorigenic human breast cells with different patterns of GSLs. The resultsshowed that the expression of GOLPH3 did not have a remarkable effect ontranscription of glycosyltransferases. Next, immunofluorescence studies in twobreast cancer cell lines (MDA-MB-231 and MCF7, with high levels of GOLPH3), revealedthat both cell lines expressed the glycolipid GM1, while GD1a was detected inMCF7 but not in MDA-MB-231 cell line. In addition, the globoside SSEA-4 waspresent in MDA-MB-231 cells but not in MCF7 cells. In GOLPH3 knockdown MCF7cells, there was a reduction in the levels of GD1a ganglioside with aconcomitant increment of GM1 ganglioside, indicating a specific effect ofGOLPH3 in the expression of GD1a. Of note, synthesis of SSEA-4 and GD1a iscarried out by the same glycosyltransferase, ST3Gal-II. Moreover, SSEA-4positive cells have increased mesenchymal markers and reduced epithelialmarkers expression, suggesting a participation of SSEA-4 in the acquisition ofa migratory phenotype. Therefore, we studied the effect of GOLPH3 on theprocess of epithelial mesenchymal transition (EMT) induced by transforminggrowth factor-β (TGF-β) in MCF7 and MDA-MB-231 cells. Preliminary resultsshowed that TGF-β treatment induced an increase in the expression of GOLPH3 inboth cell lines. In addition, SSEA-4 globoside levels were also increased inMDA-MB-231 cells after TGF-β treatment. Future experiments are required toconfirm the concomitant increasement of GM1 and GD1a levels with SSEA-4 andGOLPH3 expression. In GOLPH3 knockdown cells, the treatment with TGF-β did not induceEMT. Also, wound-healing assays in MDA-MB-231 cells indicated that theexpression of GOLPH3 impairs the migration capacity. Taken together, theseresults support the idea that GOLPH3 expression is involved in the expression patternof GSLs of breast cancer cellular lines.