Death receptor 5 and cellular FLICE-inhibitory protein regulate pemetrexed-induced apoptosis in human lung cancer cells

Our plain-English summary of Death receptor 5 and cellular FLICE-inhibitory protein regulate pemetrexed-induced apoptosis in human lung cancer cells, by L. Su, G. Liu, X. Hao, et al (European Journal of Cancer, 2011).

The study

• Authors: L. Su, G. Liu, X. Hao, N. Zhong, D. Zhong, X. Liu, S. Singhal
• Journal: European Journal of Cancer
• Published: 2011;47(16):2471-8
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Pemetrexed is a clinically available anti-folate therapeutic agent used in combination with cisplatin for the management of patients with malignant pleural mesothelioma and advanced non-small cell lung cancer. Pemetrexed inhibits three enzymes in purine and pyrimidine synthesis necessary for precursor DNA nucleotides which in turn disrupts growth and survival of normal and cancer cells. The mechanism by which pemetrexed induces apoptosis remains largely uncharacterised. In the current study, we examined the downstream effect of pemetrexed in inducing apoptosis in lung cancer cells. We showed that pemetrexed induced apoptosis via up-regulation of Death Receptor 5 (DR5), an important death receptor for tumour necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL). In addition, we discovered a synergistic effect of combination pemetrexed and recombinant TRAIL in inducing apoptosis. Modulating DR5 induction by small interfering RNA abrogated the ability of pemetrexed to induce apoptosis. In addition, silencing of C/EBP homologous protein (CHOP) expression reduced DR5 expression, demonstrating that the transcriptional factor CHOP has a pivotal role on DR5 up-regulation following pemetrexed treatment. In addition, enforced expression of cellular FLICE-inhibitory protein (c-FLIP), a known inhibitor of caspase 8, protected neoplastic cells from apoptosis despite pemetrexed and/or TRAIL therapy. Thus, our findings demonstrate the efficacy and mechanistic underpinnings of pemetrexed-induced apoptosis, and they suggest pemetrexed may have clinical utility when used in combination with TRAIL for the management of patients with lung cancer.

Copyright © 2011 Elsevier Ltd. All rights reserved.

In plain English

This laboratory study examined how the chemotherapy drug pemetrexed kills human non-small cell lung cancer cells grown in dishes. It did not study asbestos exposure or mesothelioma cells. The authors treated three lung cancer cell lines (H157, A549 and H1792) with pemetrexed, sometimes combined with a protein called TRAIL. Pemetrexed triggered cell death (apoptosis) in all three lines. It also raised levels of a cell-surface 'death receptor' called DR5 and of a protein called CHOP. When DR5 was silenced in A549 cells, the share of dying cells after pemetrexed fell from 29% to 18%. Silencing CHOP lowered it from 32% to 22%. Cells engineered to make extra c-FLIPL, a protein that blocks this death pathway, were protected. With pemetrexed plus TRAIL, 53.2% of control cells died, compared with 29.4% of the c-FLIPL cells. The authors concluded that pemetrexed acts through a CHOP-driven rise in DR5 and a fall in c-FLIP. They said future studies need to clarify how pemetrexed raises CHOP.

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 (cell culture) experiment on human lung cancer cell lines
• Who was studied: three human non-small cell lung cancer cell lines (H157, A549, H1792) purchased from the American Type Culture Collection; most follow-up experiments used A549 cells only
• Exposure: the drug pemetrexed at 2.5 to 10 micromoles per litre (printed as 'lmol/L', a scanning error for µmol/L; the figures read 'µM'), mostly for 48 hours, alone or combined with TRAIL at 40 ng/ml for 24 hours; no asbestos exposure was studied
• Main results:
  • Pemetrexed induced apoptosis in all three lung cancer cell lines
  • DR5 protein levels rose with increasing pemetrexed dose in all three cell lines; in A549 cells the rise began at 36 hours and peaked at 48 hours
  • In A549 cells with DR5 silenced, the percentage of apoptotic cells after pemetrexed fell from 29% to 18%
  • In A549 cells with CHOP silenced, the percentage of apoptotic cells after pemetrexed fell from 32% to 22%
  • In A549 and H157 cells, levels of the endoplasmic reticulum stress markers Bip and IRE1a rose with pemetrexed concentration
  • In A549 cells made to overexpress c-FLIPL, cleavage of caspases and PARP after pemetrexed was reduced compared with control cells
  • With pemetrexed plus TRAIL, 53.2% of control A549-LacZ cells were apoptotic, compared with 29.4% of c-FLIPL-overexpressing A549-FLIPL cells
• The authors' conclusion: The authors concluded that pemetrexed induces a CHOP-mediated increase in DR5 and a decrease in c-FLIP. In their view, this leads to apoptosis and strengthens TRAIL-induced apoptosis in human NSCLC cells.
• Limitations the authors state:
  • The authors state that future studies need to clarify how pemetrexed increases CHOP and whether other factors are involved
  • The authors state that the reason for an early rise in FLIPL levels after pemetrexed is unclear
  • The authors note that PARP cleavage appeared earlier (24 hours) than expected. They suggest this may reflect antibody strength and long exposure time in the assay, or weak necrotic cell death.

Topics

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

Medical terms in this study, explained in our Lexicon: Pemetrexed (Alimta), Apoptosis, Lung Cancer, Cisplatin, Pleural Mesothelioma, Non-Small Cell Lung Cancer, Necrosis, Synergistic Effect.

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)
• Flow cytometric measurement of cellular FLICE-inhibitory protein (c-FLIP) in ovarian carcinoma effusions — H.P. Dong, A.K. Ree Rosnes, et al. (2011)
• Synergistic antitumor activity of recombinant human Apo2L/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in combination with carboplatin and pemetrexed in malignant pleural mesothelioma — G. Pasello, L. Urso, 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)
• COX-2 specific inhibitors enhance the cytotoxic effects of pemetrexed in mesothelioma cell lines — S.L. O'Kane, G.L. Eagle, et al. (2010)
• Pharmacokinetic evaluation of pemetrexed — J.B. Sørensen (2011)

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