Restoring Anticancer Immune Response by Targeting Tumor-Derived Exosomes With a HSP70 Peptide Aptamer

Gobbo J, et al., 108(3). pii: djv330, J Natl Cancer Inst, 2015

According to recent studies, myeloid-derived suppressor cells (MDSCs) suppress tumor immunity of cancer patients. Exosomes are cell-derived nanovesicles that are discharged into the extracellular environment. Exosomes, through heat shock protein 70 (HSP70) on their membrane, binds to the toll-like receptor 2 (TLR2) on MDSCs, in order to modulate antitumor immune responses. Described herein is the analysis of exosomes isolated from mouse (C57Bl/6), breast/lung/ovarian cancer patient samples, and cultured cancer cells, using various methods such as the Nanoparticle tracking analysis, Bio-Layer Interferometry, FACS, and electron microscopy. Bio-Layer Interferometry (BLI) was used to study protein-protein binding interactions. A Pall ForteBio Octet RED instrument equipped with Streptavidin Biosensor probes were used to perform BLI assays. Biosensor tips were allowed to capture biotinylated peptide aptamer ligand (A8) or TLR2. The sensor tips were then incubated with exosomes (from cancer cell lines, normal cells, mice blood, or human urine) or HSP70 or cmHSP70. The KD values were determined for each binding interaction. Overall results of this investigation demonstrate that the peptide aptamer A8 tightly binds to HSP70 present in Tumor-derived exosomes (TDEs) and in turn blocks the MDSCs stimulation. By using an in vivo study, authors report that, associating A8 with a chemotherapeutic drug such as cisplatin or 5-fluorouracil, anticancer immune response can be restored. Finally, the potential of using A8 to quantify TDEs in human samples was also demonstrated.

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