P02.20.B PLASMA MEMBRANE-ASSOCIATED 70 KDA HEAT SHOCK PROTEIN (HSP70) INVOLVED IN GLIOBLASTOMA CELLS INVASION AS A TARGET FOR TUMOR THERANOSTICS

Abstract BACKGROUND Heat shock proteins (HSPs) represent a large family of highly conserved proteins serving as molecular chaperones that play an important role in intracellular homeostasis. Apart from their intracellular localization, members of various HSPs families such as HSP70 have been reported to be expressed on the plasma membrane of malignant cells, including glioblastoma multiforme (GBM). However, the role of the membrane-bound protein Hsp70 has not yet been investigated in the pathophysiology of GBM. MATERIAL AND METHODS mHsp70 expression as related to GBM cell invasive potential was analyzed in biopsies obtained from neurooncological patients using CellVoyager CQ1 Benchtop High-Content Analysis System (Yokogawa) and inverted confocal microscopy (Leica Microsystems). Application of membrane-associated chaperone for targeted therapies was assessed in the intracranial human NCH644, NCH421k, and U87 GBM models in immunodeficient mice employing various chaperone inhibitors (i.e., JG-98, MKT-077, pifithrin-μ (PES)) as a monotherapy or in combination with a single dose of stereotactic irradiation (10Gy) (SARRP). RESULTS Live-cell imaging of the patient-derived biopsies demonstrated the increased cellular density of mHsp70+ GBM cells particularly in the tissue along the tumor-brain margin. Time-lapse evaluation of the tumor sample further proved the migration of mHsp70+ cells into the surrounding normal brain tissues. Subsequent high-powered multiplex immunofluorescence analysis (Akoya Biosystems) confirmed significantly increased single-cell infiltration of mHsp70+ tumor cells (also positively stained for Nestin, Oct4, and SOX2) in the normal brain tissues. When mHsp70 inhibitors were applied in GBM animal models as a monotherapy or in combination with radiotherapy dramatic inhibition of tumor progression (as shown by MRI) and increased animal survival were observed. CONCLUSION Expression of the mHsp70 on the plasma membrane of GBM cells corresponds to the highly invasive potential of the tumor cells in neuro-oncological patients. Administration of the HSP70 small molecular inhibitors significantly decreased the GBM growth and invasion thus prolonging the overall survival of tumor-bearing mice. Further development of mHsp70-targeted agents represents a promising approach in treatment of multiforme glioblastoma.