PO-506 Targeting membrane-bound Hsp70 on cancer cells with functionalized superparamagnetic nanoparticles: new perspectives for early diagnosis and therapy

Abstract

IntroductionThe stress-inducible 72 kDa heat shock protein (mHsp70) is known to be expressed on the plasma membrane of tumour cells, but not on the corresponding normal cells. Targeting of the mHsp70 might provide a promising strategy for theranostics. Functionalized superparamagnetic iron oxide nanoparticles (SPIONs) have emerged as a promising contrast agents for the molecular magnetic resonance imagning (MRI). Coating of nanoparticles surface with therapeutic ligands could provide an anti-cancer activity.Material and methodsSynthesised nanocomplexes were conjugated with anti-Hsp70 tools (including monoclonal cmHsp70.1 antibodies (cmHsp70.1-SPIONs), granzyme B (GrB-SPIONs), tumour penetrating peptide TPP (TPP-SPIONs)) and in vitroanalysed for specific targeting of mHsp70 in cancer cells. Diagnostic potential of nanoparticles for MRI was assessed in the orthotopic models of U87 glioblastoma in NMRI nu/nu mice, C6 glioma in rats, orthotopic H1339 lung cancer in immunodeficient nu/nu mice, GL261 glioma in C57/Bl6 mice. To increase the tumour accumulation of particles additionally an external magnetic field was applied. Theranostic potential of GrB-SPIONs (that have a pro-apoptotic activity) was assessed as a monotherapy or in combination with radiotherapy.Results and discussionsSuperparamagentic conjugates had a high contrast enhancing properties (NMR relaxivity studies) and specifically targeted Hsp70-positive tumour cells (as shown by confocal and electron microscopies, flow cytometry) in a dose-dependent manner. High-resolution MRI (11 T) on T2-weighted images demonstrated the retention of conjugates in the tumour site. Biodistribution analysis employing highly sensitive non-linear magnetic response measurements (NLR-M2) confirmed the retention of particles in the tumour (that was further confirmed by histological studies). Application of the external magnetic field further enhanced accumulation of the nanocarriers in the tumour. Due to the pro-apoptotic potency of GrB-SPIONs conjugates the latter, when being systemically administered in tumor-bearing animals, not only targeted the Hsp70-positive tumours but also induced the delay of cancer progression (MRI volumometry) and increased the survival. Combination of GrB-SPIONs with radiotherapy further enhanced the anti-cancer activity of the conjugates.ConclusionOverall, the data showed that Hsp70-targeted superparamagnetic nanoparticles have a potential to be used for the early detection and therapy of the tumours.