Inhibition of autophagy potentiates pemetrexed and simvastatin-induced apoptotic cell death in malignant mesothelioma and non-small cell lung cancer cells

Our plain-English summary of Inhibition of autophagy potentiates pemetrexed and simvastatin-induced apoptotic cell death in malignant mesothelioma and non-small cell lung cancer cells, by K.E. Hwang, Y.S. Kim, J.W. Jung, et al (Oncotarget, 2015).

The study

• Authors: K.E. Hwang, Y.S. Kim, J.W. Jung, S.J. Kwon, D.S. Park, B.K. Cha, S.H. Oh, K.H. Yoon, E.T. Jeong, H.R. Kim
• Journal: Oncotarget
• Published: 2015;6(30):29482-96
• Cited by: 42 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Pemetrexed, a multitarget antifolate used to treat malignant mesothelioma and non-small cell lung cancer (NSCLC), has been shown to stimulate autophagy. In this study, we determined whether autophagy could be induced by pemetrexed and simvastatin cotreatment in malignant mesothelioma and NSCLC cells. Furthermore, we determined whether inhibition of autophagy drives apoptosis in malignant mesothelioma and NSCLC cells. Malignant mesothelioma MSTO-211H and A549 NSCLC cells were treated with pemetrexed and simvastatin alone and in combination to evaluate their effect on autophagy and apoptosis. Cotreatment with pemetrexed and simvastatin induced greater caspase-dependent apoptosis and autophagy than either drug alone in malignant mesothelioma and NSCLC cells. 3-Methyladenine (3-MA), ATG5 siRNA, bafilomycin A, and E64D/pepstatin A enhanced the apoptotic potential of pemetrexed and simvastatin, whereas rapamycin and LY294002 attenuated their induction of caspase-dependent apoptosis. Our data indicate that pemetrexed and simvastatin cotreatment augmented apoptosis and autophagy in malignant mesothelioma and NSCLC cells. Inhibition of pemetrexed and simvastatin-induced autophagy was shown to enhance apoptosis, suggesting that this could be a novel therapeutic strategy against malignant mesothelioma and NSCLC.

In plain English

This was a laboratory study of cancer cells and mice. It did not study asbestos exposure or human patients. The authors treated MSTO-211H malignant mesothelioma cells and A549 non-small cell lung cancer cells with the cancer drug pemetrexed and the drug simvastatin, alone and together. The combination caused more apoptosis (programmed cell death) and more autophagy (a process in which cells break down their own contents) than either drug alone. Blocking autophagy with 3-MA, bafilomycin A or E64D/pepstatin A, or by silencing the ATG5 gene, increased cell death. Boosting autophagy with rapamycin or LY294002 reduced it. All animal experiments used A549 lung cancer cells, not mesothelioma cells. In mice with tumors under the skin (5 per group), the combination gave significantly smaller tumors than either drug alone. In mice with tumors in the chest, the authors reported that at 2 weeks tumors grew by about 200 mm2 untreated, 175 mm2 with 3-MA and 75 mm2 with the combination, and remained 45 mm2 with 3-MA plus the combination. The authors concluded that blocking autophagy could enhance the anticancer effects of the drug combination.

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 experiments on human cancer cell lines, plus animal experiments in nude mice (subcutaneous xenografts and an orthotopic chest tumor model)
• Who was studied: MSTO-211H malignant mesothelioma cells (from ATCC, USA) and A549 human lung cancer cells (from the Korean Cell Line Bank). Athymic nude mice: 4 groups of 5 in the xenograft study, and 20 mice in the orthotopic study. The mice were given A549 cells only.
• Exposure: No asbestos exposure was studied. In cells, the treatments were 1 μM pemetrexed and/or 5 μM simvastatin, with or without autophagy inhibitors (3-MA, ATG5 siRNA, bafilomycin A, E64D/pepstatin A) or activators (rapamycin, LY294002). Mice received pemetrexed 100 mg/kg weekly and simvastatin 20 mg/kg daily.
• Main results:
  • In MSTO-211H and A549 cells, the combination significantly increased apoptosis compared with either drug alone.
  • In both cell lines, the combination produced a greater autophagy marker signal (LC3-I to LC3-II conversion) than either drug alone.
  • In MSTO-211H and A549 cells, adding the autophagy activators rapamycin or LY294002 significantly reduced apoptosis compared with the combination alone.
  • In MSTO-211H and A549 cells, blocking autophagy with 3-MA significantly increased apoptosis compared with the combination alone. Silencing ATG5, bafilomycin A and E64D/pepstatin A also increased the proportion of apoptotic cells.
  • In mice with A549 xenografts, the combination group had significantly smaller tumor volumes than groups given either drug alone. Body weights did not differ significantly among the 4 groups.
  • In the orthotopic A549 mouse model, at 2 weeks tumors grew by about 200 mm2 in controls and 175 mm2 with 3-MA alone, and by 75 mm2 with the combination. Tumors with 3-MA plus the combination remained 45 mm2.
• The authors' conclusion: The authors concluded that autophagy served a pro-survival function in the treated cells, and that inhibiting autophagy can enhance the anticancer effects of pemetrexed and simvastatin and could be targeted to improve the combination's efficacy.
• Limitations the authors state:
  • The authors stated that cross talk between the AKT/mTOR and AMPK/mTOR signaling pathways is not entirely clear and needs further investigation.
  • In the micro-CT analysis, small tumors were excluded because they could not be measured.

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: Pemetrexed (Alimta), Mesothelioma, Non-Small Cell Lung Cancer, Antifolate, Apoptosis.

Related studies

• Enhanced apoptosis by pemetrexed and simvastatin in malignant mesothelioma and lung cancer cells by reactive oxygen species-dependent mitochondrial dysfunction and Bim induction — K.E. Hwang, Y.S. Kim, et al. (2014)
• Pemetrexed induces apoptosis in malignant mesothelioma and lung cancer cells through activation of reactive oxygen species and inhibition of sirtuin 1 — K.E. Hwang, Y.S. Kim, et al. (2015)
• Pro-oxidant activity of sulforaphane and cisplatin potentiates apoptosis and simultaneously promotes autophagy in malignant mesothelioma cells — Y.J. Lee, S.H. Lee (2017)
• Dexamethasone alleviates pemetrexed-induced senescence in Non-Small-Cell Lung Cancer — H. Ge, J. Ke, et al. (2018)
• Curcumin induces autophagy in ACC-MESO-1 cells — Y. Yamauchi, Y. Izumi, et al. (2012)
• Combination of onconase and dihydroartemisinin synergistically suppresses growth and angiogenesis of non-small-cell lung carcinoma and malignant mesothelioma — R. Shen, J. Li, et al. (2016)

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