Functional inhibition of heat shock protein 70 by VER‐155008 suppresses pleural mesothelioma cell proliferation via an autophagy mechanism

Abstract

Background: Pleural mesothelioma, a devastating asbestos‐associated malignancy, urgently requires a novel effective therapy. Heat shock protein 70 (HSP70), which is synthesized in the cell response to protein damage, is expected to be a new target for antitumor treatment. In addition to its well‐known protein refolding function, HSP70 regulates cell proliferation through different pathways, including PI3K/AKT/mTOR, and autophagy in malignant cells. In this study, we attempted to clarify the effects of VER‐155008, an HSP70 inhibitor, on pleural mesothelioma. Methods: Human pleural mesothelioma cell lines 211H, H2452 and H28 were cultured with VER‐155008, and protein expression, cell proliferation, colony formation, cell cycle, synergistic effect with cisplatin, and autophagy induction were analyzed. Results: In mesothelioma cell lines, VER‐155008 (5.0 μM or more) inhibited cell growth and colony formation, accompanied by G1 cell cycle arrest. According to western blot analysis, VER‐155008 reduced p‐AKT expression. However, VER‐155008 failed to show a synergistic effect with cisplatin on cell growth. Mesothelioma cells transfected with the novel plasmid pMRX‐IP‐GFP‐LC3‐RFP‐LC3ΔG, which was developed for the quantitative and statistical estimation of macroautophagy, showed enhanced macroautophagy upon treatment with VER‐155008 and gefitinib which is an EGFR‐tyrosine kinase inhibitor. In addition, fetal bovine serum deprivation induced macroautophagy was further enhanced by VER‐155008. Conclusions: On the basis of these results, functional HSP70 inhibition by VER‐155008 suppressed cell growth in pleural mesothelioma cells, accompanied by enhanced macroautophagy. HSP70 inhibition is thus expected to become a new strategy for treating mesothelioma. Key points Significant findings of the study In pleural mesothelioma cells, inhibition of HSP70 function by VER‐155008 suppressed cell proliferation accompanied by induction of autophagy which was synergistically enhanced under the starvation condition, whereas gefitinib, an EGFR‐TKI, did not show the same synergistic effect in autophagy. What this study adds The inhibition of HSP70 induced autophagy and suppressed cell proliferation in mesothelioma cells.

The Epithelial-to-Mesenchymal Transition (EMT) in the Development and Metastasis of Malignant Pleural Mesothelioma

“…In this regard, the inhibition of protein kinase CK-2 by CX-4945 with the use of Ginsenoside 20 (R)-Rg3 in A549 blocked TGFβ-induced EMT [55], along with the use of Galunisertib or Vacosertib (inhibitors of TGFβRI) [86], constituted further potential options in MPM treatment. Moreover, as indicated above, the use of Hsp70 inhibitors or RNA mimics could inhibit EMT and be a potential strategy in MPM treatment [70,75,77].…”

“…In hypoxia, EMT is supported by the nuclear translocation of SNAI1 via the inactivation of GSK-3β and by the long-lasting nuclear translocation of β-catenin [3]. Furthermore, heat shock protein 70 is a critical protein that should be involved in oxidative stress and EMT in cancer cell lines (Hsp70) [70]. Hsp70 is a molecular chaperonine that allows survival in stress conditions, and its expression is enhanced in human tumors in response to environmental insults [71,72].…”

“…Specifically, Hsp70 inhibits EMT in mesothelial cells through the negative regulation of ROS production, phosphorylation and the nuclear translocation of Smad3 and Smad4 [72]. In addition, VER-155008, an Hsp70 inhibitor in human pleural mesothelioma cell lines (211H, H2452 and H28), suppresses cell growth and enhances autophagy [70]. Therefore, Hsp70 inhibition could be a potential strategy in MPM treatment.…”

Advances in the study of HSP70 inhibitors to enhance the sensitivity of tumor cells to radiotherapy

“…Furthermore, in pleural mesothelioma, VER-155008 inhibits HSP70 by inducing G1 cell cycle arrest and disrupting the PI3K/AKT/mTOR pathway, thereby suppressing tumor proliferation ( Sakai et al, 2021 ). In oral squamous cell carcinoma, PES blocked the cell cycle in the G2/M phase and induced apoptosis ( Jiang and Xiao, 2020 ).…”

Nanomaterial-mediated low-temperature photothermal therapy via heat shock protein inhibition

“…Miyagawa, T. et al Investigated 17-DMAG (HSP90 inhibitor) and quercetin (HSP70 inhibitor) with ferromagnetic particle (FMP)-mediated antitumor effects of low-temperature PTT and found that tumor growth was significantly inhibited ( Miyagawa et al, 2014 ). Instead of applying two small molecule inhibitors of HSPs simultaneously, Tang et al applied VER-155008, a small molecule inhibitor of both HSP90 and HSP70, to nanomaterials and established a therapeutic system consisting of methoxy-polyethylene-glycol-coated-gold-nanorods (MPEG-AuNR) and VER-155008 micelles (VER-M), which improved the biocompatibility and boosted permeability and retention (EPR) effects of the nanomaterials and reduced toxicity ( Tang et al, 2018 ; Brünnert et al, 2020 ; Sakai et al, 2021 ).…”