Hsp70 in Liquid Biopsies—A Tumor-Specific Biomarker for Detection and Response Monitoring in Cancer

In contrast to normal cells, tumor cells of multiple entities overexpress the Heat shock protein 70 (Hsp70) not only in cytosol, but also present it on their plasma membrane a tumor-specific manner. Furthermore, Hsp70-positive actively release Hsp70 small extracellular vesicles with biophysical characteristics exosomes. Due conformational changes lipid environment, most commercially available antibodies fail detect membrane-bound and vesicular Hsp70. To fill this gap assess role circulation as potential biomarker, we established novel complete (comp)Hsp70 sandwich ELISA, using two monoclonal (mAbs), that is able recognize both free lipid-associated cell surface viable vesicles. The epitopes mAbs cmHsp70.1 (aa 451–461) cmHsp70.2 614–623) are conserved among different species reside substrate-binding domain measured affinities 0.42 nM 0.44 nM, respectively. Validation compHsp70 ELISA revealed high intra- inter-assay precision, linearity concentration range 1.56 25 ng/mL, recovery rates spiked liposomal (>84%), comparable values between human serum samples no interference by food intake or age donors. concentrations patients glioblastoma, squamous adeno non-small lung carcinoma (NSCLC) at diagnosis were significantly higher than those healthy dropped concomitantly decrease mass upon irradiation approximately 20 Gy (range 18–22.5 Gy) after completion radiotherapy (60–70 Gy). summary, presented herein provides sensitive reliable tool for measuring liquid biopsies patients, levels which can be used risk assessment (i.e., differentiation grade III vs. IV NSCLC) monitoring therapeutic outcomes.