Gefitinib targets EGFR dimerization and ERK1/2 phosphorylation to inhibit pleural mesothelioma cell proliferation

Our plain-English summary of Gefitinib targets EGFR dimerization and ERK1/2 phosphorylation to inhibit pleural mesothelioma cell proliferation, by R.E. Favoni, A. Pattarozzi, M. Lo Casto, et al (Current Cancer Drug Targets, 2010).

The study

• Authors: R.E. Favoni, A. Pattarozzi, M. Lo Casto, F. Barbieri, M. Gatti, L. Paleari, A. Bajetto, C. Porcile, G. Gaudino, L. Mutti, G. Corte, T. Florio
• Journal: Current Cancer Drug Targets
• Published: 2010;10(2):176-91
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Altered EGFR activity is a causal factor for human tumor development, including malignant pleural mesotheliomas. The aim of the present study was the evaluation of the effects of Gefitinib on EGF-induced mesothelioma cell proliferation and the intracellular mechanisms involved. Cell proliferation, DNA synthesis and apoptosis were measured by MTT, thymidine incorporation and FACS analysis; EGFR, ERK1/2 and Akt expression and phosphorylation by Western blot, whereas receptor sites were analyzed by binding studies. Gefitinib inhibited EGF-induced proliferation in two mesothelioma cell lines, derived from pleural effusion (IST-Mes2) or tumor biopsy (ZL55). The treatment with Gefitinib induced cell cycle arrest in both cell lines, while apoptosis was observed only for high concentrations and prolonged drug exposure. EGF-dependent mesothelioma cell proliferation was mediated by EGFR and ERK1/2 phosphorylation, while Akt was not affected. Gefitinib inhibited both EGFR and ERK1/2 activation, being maximal at drug concentrations that induce cytostatic effects, suggesting that the proapoptotic activity of Gefitinib is independent from EGFR inhibition. Gefitinib treatment increased EGFR Bmax, possibly through membrane stabilization of inactive receptor dimers that we show to be induced by the drug also in the absence of EGF. EGFR activation of ERK1/2 represents a key pathway for pleural mesothelioma cell proliferation. Low concentrations of Gefitinib cause mesothelioma cell cycle arrest through the blockade of EGFR activity while high concentrations induce apoptosis. Finally, we propose that the formation of inactive EGFR dimers may contribute to the antitumoral activity of Gefitinib.

In plain English

This was a laboratory study of cancer cells, not of people. The authors tested gefitinib, a drug that blocks a growth-signal receptor called EGFR, on two malignant pleural mesothelioma cell lines, IST-Mes2 and ZL55. The cell lines came from previously untreated, asbestos-exposed men aged 65 and 52. Treatment for 24 to 48 hours had no statistically significant effect. From 72 hours on, gefitinib slowed growth. The concentration that halved growth ranged from 17.3 to 22.6 μM for IST-Mes2 and from 7.6 to 12.9 μM for ZL55. Up to that concentration the effect was cytostatic: growth was inhibited and resumed after the drug was removed. Higher concentrations began to kill cells in both lines; IST-Mes2 was more prone to apoptosis (programmed cell death). Gefitinib blocked EGF-triggered activation of EGFR and reduced activation of a downstream signal, ERK1/2. It also increased measured EGF binding sites per cell. In IST-Mes2 cells it caused EGFR molecules to pair into inactive dimers. The authors proposed that trapping EGFR in inactive dimers blocks ERK1/2 signalling. They noted that some of the mechanisms remain unproven.

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 malignant pleural mesothelioma cell lines: IST-Mes2 (from pleural effusion) and ZL55 (from tumor biopsy). They were derived from asbestos-exposed, pharmacologically untreated male patients aged 65 and 52, respectively. A panel of six mesothelioma cell lines plus Met5A mesothelial cells was screened first.
• Exposure: The drug gefitinib (ZD1839, Iressa), tested at 5-30 μM on IST-Mes2 and 1-30 μM on ZL55, with or without the growth factor EGF. Asbestos exposure was not studied, and no fiber type is named.
• Main results:
  • Short-term treatment (24 to 48 h) had no statistically significant effect on either cell line, and 50% growth inhibition was not reached.
  • After 72 h or more, the concentration giving 50% growth inhibition ranged from 17.3 to 22.6 μM for IST-Mes2 and from 7.6 to 12.9 μM for ZL55.
  • In both cell lines, growth inhibition was cytostatic up to the 50%-inhibition concentration, meaning growth recovered after drug removal. At higher concentrations it began to become cytotoxic.
  • Apoptosis peaked at 72 h in both cell lines at concentrations above the 50%-inhibition concentration. IST-Mes2 cells were more prone to apoptosis than ZL55.
  • In IST-Mes2 cells at 1x the 50%-inhibition concentration, apoptotic cells rose from 6-7% at 12-24 h to 19% at 72 h.
  • In IST-Mes2 cells, double the 50%-inhibition concentration increased apoptotic cells about 2-fold at 12-48 h and 4.5-fold at 72 h compared with 1x.
  • In ZL55 cells at 1x the 50%-inhibition concentration there was no significant pro-apoptotic activity (range 0.68 - 0.94%).
  • In ZL55 cells at double the 50%-inhibition concentration, a significant amount of apoptotic cells appeared only at 72 h.
  • In both cell lines, gefitinib given before and during EGF reversed EGF-induced EGFR phosphorylation and significantly reduced ERK1/2 activation.
  • EGF did not activate Akt in either cell line.
  • In IST-Mes2 cells, the ERK1/2-pathway blocker PD98059 completely abolished EGF-driven proliferation.
  • Gefitinib at 0.5-1x the 50%-inhibition concentration increased the calculated EGF binding sites per cell by 150% in IST-Mes2 and 230% in ZL55.
  • In IST-Mes2 cells, gefitinib induced EGFR dimers that were not active, whether or not EGF was present.
• The authors' conclusion: The authors proposed that gefitinib sequesters EGFR in inactive dimers at the cell membrane, preventing activation of downstream signals, in particular the ERK1/2 pathway.
• Limitations the authors state:
  • The authors could not provide definitive proof that persistent nuclear ERK1/2 protects ZL55 cells from apoptosis, and said further studies are needed.
  • The exact molecular mechanism linking the inactive EGFR dimers to the increase in EGF binding was not identified.
  • Biological and biochemical results in the two cell lines did not fully agree. The authors attributed this to the patients' different and unknown clinical histories.

Topics

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

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

Related studies

• Decrease in phosphorylation of ERK following decreased expression of NK cell-activating receptors in human NK cell line exposed to asbestos — Y. Nishimura, M. Maeda, et al. (2009)
• Asbestos-mediated CREB phosphorylation is regulated by protein kinase A and extracellular signal-regulated kinases 1/2 — C.A. Barlow, T.F. Barrett, et al. (2007)
• Synergistic anticancer activity of arsenic trioxide with erlotinib is based on inhibition of EGFR-mediated DNA double-strand break repair — K. Kryeziu, U. Jungwirth, et al. (2013)
• Perifosine as a potential novel anti-cancer agent inhibits EGFR/MET-AKT axis in malignant pleural mesothelioma — G. Pinton, A.G. Manente, et al. (2012)
• The duration of nuclear extracellular signal-regulated kinase 1 and 2 signaling during cell cycle reentry distinguishes proliferation from apoptosis in response to asbestos — Z. Yuan, D.J. Taatjes, et al. (2004)
• ERK2 is essential for the growth of human epithelioid malignant mesotheliomas — A. Shukla, J.M. Hillegass, et al. (2011)

Browse return to medical research.