The contribution of proteoglycans to heterogeneity and temozolomide resistance of glioblastoma cells

Aim: Heterogeneity of glioblastoma (GB) cells significantly contributes to tumor resistance against temozolomide (TMZ) and the development of disease relapse. Multiple molecular mechanisms are involved in this process, yet the contribution of proteoglycans (PGs) remains unknown. This study aimed to investigate the potential involvement of PGs (both at core proteins and polysaccharide chains) in the heterogeneity and TMZ resistance of GB cells.Methods: Seven human GB cell lines were characterized for TMZ sensitivity, cell phenotypic traits, gene expression for glucocorticoid receptor (GR, NR3C1), PG core proteins-and heparan sulfate (HS) biosynthesis-related genes and content of their chondroitin sulfate (CS) and HS chains.Results: Although the studied cell lines have similar proliferation rates, they significantly differ in their migration activity, clonogenicity, and TMZ resistance (IC50 8.51-369.59 mu M in the line of U343, LN215, HS683, U87, LN71, LN405, LN18), creating a specific phenotype for each cell line. Some PGs (NG2/CSPG4, CSPG5, and versican) contributed to the molecular heterogeneity of these cells being cell line-specifically expressed in all cell lines, which also differed in terms of the CS/HS content. Transcriptional activity of the HS metabolic system was low in these GB cell lines, expressing mainly EXT1/2 and NDST1/2, while expression levels of sulfotransferases and SULF2 were cell line-specific. TMZ resistance of these cells was correlated with the expression of stem-cell marker CD44 (+3.5-fold, r = 0.73) and GR (-3-fold, r =-0.81). TMZ treatment of the resistant (LN405) and sensitive (LN215) cells resulted in complex changes in cell migration as well as NG2/CSPG4 expression and CS/HS content.Conclusion: Differential expression of PGs and CS/HS content contribute to the heterogeneity of GB cells, and CD44 and NR3C1 might be informative biomarkers for TMZ resistance.