Pro-oxidant activity of sulforaphane and cisplatin potentiates apoptosis and simultaneously promotes autophagy in malignant mesothelioma cells

Our plain-English summary of Pro-oxidant activity of sulforaphane and cisplatin potentiates apoptosis and simultaneously promotes autophagy in malignant mesothelioma cells, by Y.J. Lee, S.H. Lee (Molecular Medicine Reports, 2017).

The study

• Authors: Y.J. Lee, S.H. Lee
• Journal: Molecular Medicine Reports
• Published: 2017;16(2):2133-2141
• Cited by: 23 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Sulforaphane (SFN) is an isothiocyanate compound derived from glucoraphanin, which is found in cruciferous vegetables, and has been heralded as a chemopreventive and/or chemotherapeutic agent. The present study investigated the effects of SFN on enhancing the anticancer role of cisplatin (cis-dichlorodiammineplatinum; CDDP) in H‑28 malignant mesothelioma cells. At concentrations demonstrating limited toxicity in MeT‑5A normal human mesothelial cells, combination treatment with the two compounds exhibited synergistic growth‑inhibiting and apoptosis‑promoting activities, as demonstrated by a series of proapoptotic events, including reactive oxygen species accumulation, loss of mitochondrial membrane potential, upregulation of p53 expression, increased B‑cell lymphoma 2 (Bcl‑2) associated X protein/Bcl‑2 ratio, activation of caspase‑3, the occurrence of a sub‑G0/G1 peak and an increase in cells with pyknotic and fragmented nuclei, Annexin V‑phycoerythrin‑positive staining and G2/M phase‑transition delay in the cell cycle. The phosphorylation levels of Akt and mammalian target of rapamycin were reduced by the combination treatment, which was accompanied by a significant increase in the level of autophagosomal marker protein microtubule‑associated protein 1 light chain 3B‑II and the accumulation of acidic vesicular organelles. Pretreatment with the antioxidant N‑acetylcysteine attenuated both apoptosis and autophagy, whereas inhibition of autophagy by bafilomycin A1 potentiated apoptotic cell death following the combination treatment with SFN and CDDP. Considering the pro‑oxidant‑based combinational approach, the results of the present study provide a rationale for targeting cytoprotective autophagy as a potential therapeutic strategy for malignant mesothelioma.

In plain English

This was a laboratory study of cells grown in dishes, not of patients, and it did not study asbestos exposure. The authors tested whether sulforaphane, a compound from cruciferous vegetables, increased the effect of the chemotherapy drug cisplatin on H-28 malignant mesothelioma cells. They compared these with MeT-5A normal human mesothelial cells. After 48 hours, 20 µM sulforaphane plus 40 µM cisplatin left 62.5% of H-28 cells viable, compared with 85.3% for sulforaphane alone and 96.7% for cisplatin alone. The authors judged the combined effect synergistic. In normal MeT-5A cells, the combination (88.3% viable) did not significantly reduce viability compared with either drug alone. With the combination, 33.05% of H-28 cells stained as apoptotic (programmed cell death), against 12.62% with sulforaphane and 3.01% with cisplatin. The combination also raised reactive oxygen species and triggered autophagy, a cellular recycling process. The antioxidant N-acetylcysteine reduced both effects. Blocking autophagy with bafilomycin A1 significantly increased cell killing. The authors concluded that targeting autophagy may be an attractive therapeutic strategy for mesothelioma, and said more detailed mechanistic 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) cell culture experiment
• Who was studied: Two commercially obtained human cell lines: H-28 malignant mesothelioma cells and MeT-5A normal mesothelial cells (no patients or animals)
• Exposure: Laboratory treatment with sulforaphane (SFN, 20 µM) and cisplatin (CDDP, 40 µM), alone or combined, for 48 hours. Some cells were pretreated with N-acetylcysteine (5 mM) or bafilomycin A1 (50 nM). No asbestos exposure was studied.
• Main results:
  • In H-28 mesothelioma cells, viability after the combination was 62.5%, compared with 85.3% for sulforaphane alone and 96.7% for cisplatin alone
  • In MeT-5A normal mesothelial cells, the combination (88.3% viable) did not significantly reduce viability compared with sulforaphane (91.6%) or cisplatin (98.5%) alone
  • The combined effect on H-28 cells was judged synergistic (combination index 0.454)
  • In H-28 cells, 33.05% of combination-treated cells were apoptotic by Annexin V staining, compared with 12.62% for sulforaphane alone and 3.01% for cisplatin alone
  • In H-28 cells, the combination raised reactive oxygen species to 38.78% and loss of mitochondrial membrane potential to 31.69% of cells. N-acetylcysteine pretreatment lowered these to 16.37% and 16.10%.
  • In H-28 cells, the combination increased the autophagy marker LC3B-II and reduced phosphorylation of Akt and mTOR, compared with either drug alone
  • Blocking autophagy with bafilomycin A1 significantly increased the combination's toxicity to H-28 cells
• The authors' conclusion: The authors concluded that targeting autophagy may be an attractive therapeutic strategy for improving clinical outcomes in malignant mesothelioma
• Limitations the authors state:
  • The authors stated that detailed mechanistic studies are needed to understand the protective role of autophagy
  • The authors stated that further research is needed on the dual role of Bcl-2 in apoptosis and autophagy

Topics

Medical terms in this study, explained in our Lexicon: Cisplatin, Apoptosis, Malignant Mesothelioma, Mesothelial Cells, Reactive Oxygen Species (ROS).

Related studies

• Cisplatin and resveratrol induce apoptosis and autophagy following oxidative stress in malignant mesothelioma cells — Y.J. Lee, G.J. Lee, et al. (2016)
• ADP sensitizes ZL55 cells to the activity of cisplatin — A. Muscella, L.G. Cossa, et al. (2019)
• Reactive oxygen species and PI3K/Akt signaling play key roles in the induction of Nrf2-driven heme oxygenase-1 expression in sulforaphane-treated human mesothelioma MSTO-211H cells — Y.J. Lee, H.Y. Jeong, et al. (2012)
• Sulforaphane inhibits PRMT5 and MEP50 function to suppress the mesothelioma cancer cell phenotype — G. Ezeka, G. Adhikary, et al. (2021)
• Distinct autophagy-apoptosis related pathways activated by Multi-walled (NM 400) and Single-walled carbon nanotubes (NIST-SRM2483) in human bronchial epithelial (16HBE14o-) cells — M. Ghosh, S. Murugadoss, et al. (2020)
• Berberine induces mitochondrial‑mediated apoptosis and protective autophagy in human malignant pleural mesothelioma NCI‑H2452 cells — Z. Yao, Y. Wan, et al. (2018)

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