Activation of JNK and IRE1 is critically involved in tanshinone I-induced p62 dependent autophagy in malignant pleural mesothelioma cells: implication of p62 UBA domain

Our plain-English summary of Activation of JNK and IRE1 is critically involved in tanshinone I-induced p62 dependent autophagy in malignant pleural mesothelioma cells: implication of p62 UBA domain, by J. Lee, E.J. Sohn, S. Yoon, et al (Oncotarget, 2017).

The study

• Authors: J. Lee, E.J. Sohn, S. Yoon, G. Won, C.G. Kim, J.H. Jung, S.H. Kim
• Journal: Oncotarget
• Published: 2017;8(15):25032-25045
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The aim of present study is to elucidate autophagic mechanism of tanshinone I (Tan I) in H28 and H2452 mesothelioma cells. Herein, Tan I exerted cytotoxicity with autophagic features of autophagy protein 5 (ATG5)/ microtubule-associated protein 1A/1B-light chain 3II (LC3 II) activation, p62/sequestosome 1 (SQSTM1) accumulation and increased number of LC3II punctae, acridine orange-stained cells and autophagic vacuoles. However, 3-methyladenine (3MA) and NH4Cl increased cytotoxicity in Tan I treated H28 cells. Furthermore, autophagy flux was enhanced in Tan I-treated H28 cells transfected by RFP-GFP-LC3 constructs, with colocalization of GFP-LC3 punctae with LAMP1 or Lysotracker. Interestingly, C-terminal UBA domain is required for Tan 1 induced aggregation of p62 in H28 cells. Notably, Tan I upregulated CCAAT-enhancer-binding protein homologous protein (CHOP), inositol-requiring protein-1 (IRE1) and p-c-Jun N-terminal kinase (p-JNK), but silencing of IRE1 or p62 and JNK inhibitor SP600125 blocked the LC3II accumulation in Tan I-treated H28 cells. Overall, these findings demonstrate that Tan I exerts antitumor activity through a compromise between apoptosis and p62/SQSTM1-dependent autophagy via activation of JNK and IRE 1 in malignant mesothelioma cells.

In plain English

This was a laboratory study of two human mesothelioma cell lines, H28 (sarcomatoid) and H2452 (epithelial subtype). It did not study asbestos exposure or people. The authors treated the cells with tanshinone I, a compound from the plant Salvia miltiorrhiza, at concentrations up to 40 micromolar. They looked at whether it killed the cells and whether it triggered autophagy, a process in which cells digest their own contents. Tanshinone I reduced cell survival as the dose rose and reduced colony formation in both cell lines, and the cells showed signs of autophagy. Blocking autophagy with 3-MA or NH4Cl increased cell killing in H28 cells. In H28 cells, a form of the p62 protein lacking its UBA region did not gather with the autophagy marker LC3II. Tanshinone I raised the stress proteins IRE1 and CHOP and activated JNK. Blocking JNK or silencing IRE1 reduced autophagy markers. The authors concluded that JNK and IRE1 activation is critically involved in this autophagy, and said animal studies are needed.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) experiment on human mesothelioma cell lines
• Who was studied: Two human mesothelioma cell lines bought from the American Type Culture Collection: H28 (sarcomatoid) and H2452 (epithelial subtype). Most mechanism experiments used H28 cells.
• Exposure: Tanshinone I (a compound from Salvia miltiorrhiza) at 0, 5, 10, 20 and 40 micromolar, usually for 24 hours. Asbestos was not studied as an exposure.
• Main results:
  • In both H28 and H2452 cells, tanshinone I was toxic to the cells in a concentration-dependent way and reduced colony formation.
  • Electron microscopy showed more autophagic vacuoles in tanshinone I-treated H28 cells.
  • At 20 micromolar, tanshinone I caused weak PARP cleavage and increased LC3 II in both cell lines.
  • In tanshinone I-treated H28 cells, the early autophagy inhibitor 3-MA reduced LC3 II but increased cytotoxicity.
  • In tanshinone I-treated H28 cells, the late autophagy inhibitor NH4Cl increased LC3II and cytotoxicity.
  • In H28 cells, a p62 mutant lacking the UBA domain did not colocalize with GFP-LC3II punctae. Full-length p62 and the LIR-deleted mutant did colocalize.
  • In both cell lines, tanshinone I increased the ER stress markers IRE1 and CHOP, but not PERK, GRP78 or ATF6.
  • In H28 cells, the JNK inhibitor SP600125 suppressed tanshinone I's activation of p62 and LC3II.
  • In tanshinone I-treated H28 cells, depleting IRE1 lowered p62 and LC3II.
  • In H28 cells, silencing IRE1 or ATG5 increased tanshinone I cytotoxicity. Depleting p62 or Beclin 1 did not.
• The authors' conclusion: The authors concluded that activation of JNK and IRE1 is critically involved in tanshinone I-induced p62/SQSTM1-dependent autophagy in malignant pleural mesothelioma cells.
• Limitations the authors state:
  • The authors stated that animal studies and further mechanistic work are needed to clarify how tanshinone I acts on autophagy and apoptosis.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Mesothelioma, Apoptosis.

Related studies

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• Inhibition of autophagy potentiates pemetrexed and simvastatin-induced apoptotic cell death in malignant mesothelioma and non-small cell lung cancer cells — K.E. Hwang, Y.S. Kim, et al. (2015)
• AKT/mTOR and c-Jun N-terminal kinase signaling pathways are required for chrysotile asbestos-induced autophagy — Z. Lin, T. Liu, et al. (2014)
• Curcumin blocks autophagy and activates apoptosis of malignant mesothelioma cell lines and increases the survival of mice intraperitoneally transplanted with a malignant mesothelioma cell line — L. Masuelli, M. Benvenuto, et al. (2017)
• Pro-oxidant activity of sulforaphane and cisplatin potentiates apoptosis and simultaneously promotes autophagy in malignant mesothelioma cells — Y.J. Lee, S.H. Lee (2017)
• Effects of Autophagy Inhibition by SAR405, a Selective VPS34 Inhibitor, on Pleural Mesothelioma Cells — Y. Kuwabara, K. Sakai, et al. (2026)

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