P01.40.B СONDITION MEDIUM OF GLIOBLASTOMA CELLS INDUCES THE EXPRESSION OF A MEMBRANE-BOUND HEAT SHOCK PROTEIN MHSP70 IN MESENCHYMAL STEM CELLS

Abstract BACKGROUND Glioblastoma multiforme (GBM) is the most aggressive form of gliomas and is characterized by increased levels of heat-shock proteins (HSPs) expression (including membrane-bound forms of HSP70, HSP90), which play a pivotal role in tumor progression. The aim of this work was to evaluate the effect of cell-conditioned medium of primary cultures of GBM on the transformation of normal mesenchymal cells which do present in the GBM microenvironment. MATERIAL AND METHODS The experiments were performed using a three-dimensional model of cell culture in a spheroidal state, since this is considered the closest approximation to the in vivo environment. FetMSC (human embryonic bone marrow mesenchymal stromal cell line) and primary culture GBM cells isolated from adult patients (n = 4) with newly diagnosed GBM without treatment were employed. The effect of three days of GBM cell-conditioned medium on changes in mHsp70 expression levels was evaluated. GBM cell culture medium and standard culture conditions for the FetMSC cell line were used as controls. The obtained data were analyzed using ImageJ software. Statistical analysis was performed using GraphPad Prism software (GraphPad Software Inc., USA). RESULTS The expression of mHsp70 on FetMSCs as detected using confocal microscopy (Olympus FV3000 system, Japan) and CytoFLEX flow cytofluorometry (CytoFLEX, Beckman Coulter, USA) revealed a more than 50% increase of mHsp70 expression by normal FetMSC cells exposed to GBM cell conditioning medium compared to the control. On stem cells the mHsp70 was located on the surface of plasma membrane in dotted patterns indicating its localization in lipid rafts (which was further proved by co-staining with anti-CD77 antibodies). CONCLUSION The obtained results demonstrate the influence of the secretome of primary GBM cell culture on the change in the level of mHsp70 expression by the normal mesenchymal cell line FetMSC, which may indicate their acquisition of a pro-tumorigenic phenotype.