PDIA3 Reduce Glioma-associated Macrophage/microglia Pro-tumor Activation trough IL-6-STAT3-PDIA3 Pathway.

Abstract

Background: Glioblastoma (GB - grade IV glioma) is the most aggressive and common cancer of central nervous system with an overall survival of 14-16 months. The GB tumor microenvironment includes cells of the innate immune system identified as glioma-associated microglia/macrophages (GAMs). It is known that between GAMs and GB cells there is a double interaction, but the role of GAMs is still poorly characterized. The endoplasmic reticulum (ER) protein ERp57, also known as PDIA3, is a thiol oxidoreductase with main function related on glycoprotein folding in endoplasmic reticulum. However, PDIA3 shows different functions. In fact, the various subcellular localizations and binding partners of PDIA3 affect numerous physiological processes and diseases: different regulation and modulation of PDIA3 has been reported in multiple pathologies including neurodegenerative diseases and cancer. Methods: In the present work, we evaluated in both GB cells and microglia-macrophage cells the expression of PDIA3 using specimens collected after surgical from 18 GB patients. In addition, we studied in vitro microglia-glioma interaction to determine the role of PDIA3 in viability and the activation of both GB and microglia cells. The study was carried using PDIA3-silenced T98G cells and/or using a pharmacological inhibitor of PDIA3 activity (Punicalagin-PUN).Results: We initially investigated the role of the PDIA3 in GB survival by inquiring The Cancer Genome Atlas dataset. The results indicated that 352 out of 690 patients reported over-expression of PDIA3, which significantly correlated with a ~55% reduction of overall survival. Subsequently, for the first time, we investigated the PDIA3 expression in the tumor and the nearby parenchyma of 18 GB patients and our data showed a significant upregulation (15% vs 10%) of ERp57/PDIA3 in GAMs of tumor specimens respect the microglia present in parenchyma. In addition, we show that conditioned medium (CMs) obtained from both wild type T98G and PDIA3 silenced T98G induced an activation of microglia cells, but the PDIA3 silenced-T98G CMs significant limited the microglia pro-tumor activation probably through a IL-6-STAT3-PDIA3 dependent mechanism. Conclusion: Our data support the relevant role of PDIA3 expression in GB pathology and link the different activation of microglia to a mechanism a IL-6-STAT3-PDIA3 dependent.