Receptor tyrosine kinase and downstream signalling analysis in diffuse malignant peritoneal mesothelioma

Our plain-English summary of Receptor tyrosine kinase and downstream signalling analysis in diffuse malignant peritoneal mesothelioma, by F. Perrone, G. Jocollè, M. Pennati, et al (European Journal of Cancer, 2010).

The study

• Authors: F. Perrone, G. Jocollè, M. Pennati, M. Deraco, D. Baratti, S. Brich, M. Orsenigo, E. Tarantino, C. De Marco, C. Bertan, A. Cabras, R. Bertulli, M.A. Pierotti, N. Zaffaroni, S. Pilotti
• Journal: European Journal of Cancer
• Published: 2010;46(15):2837-48
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Our aim was to assess the activation profile of EGFR, PDGFRB and PDGFRA receptor tyrosine kinases (RTK) and their downstream effectors in a series of cryopreserved diffuse malignant peritoneal mesothelioma (DMPM) surgical specimens to discover the targets for drug inhibition. We also made a complementary analysis of the cytotoxic effects of some kinase inhibitors on the proliferation of the human peritoneal mesothelioma STO cell line. We found the expression/phosphorylation of EGFR and PDGFRB in most of the tumours, and PDGFRA activation in half. The expression of the cognate ligands TGF-α, PDGFB and PDGFA in the absence of RTK mutation and amplification suggested the presence of an autocrine/paracrine loop. There was also evidence of EGFR and PDGFRB co-activation. RTK downstream signalling analysis demonstrated the activation/expression of ERK1/2, AKT and mTOR, together with S6 and 4EBP1, in almost all the DMPMs. No KRAS/BRAF mutations, PI3KCA mutations/amplifications or PTEN inactivation were observed. Real-time polymerase chain reaction revealed the decreased expression of TSC1 c-DNA in half of the tumours. In vitro cytotoxicity studies showed the STO cell line to be resistant to gefitinib and sensitive to sequential treatment with RAD001 and sorafenib; these findings were consistent with the presence of the KRAS mutation G12D in these cells although it was not detectable in the original tumour. Our results highlight the ligand-dependent activation and co-activation of EGFR and PDGFRB, as well as a connection between these activated RTKs and the downstream mTOR pathway, thus supporting the role of combined treatment with RTK and mTOR inhibitors in DMPM.

Copyright © 2010 Elsevier Ltd. All rights reserved.

In plain English

This laboratory study examined tumour tissue from 20 patients with diffuse malignant peritoneal mesothelioma (DMPM). The patients had cytoreductive surgery and hyperthermic intraperitoneal chemotherapy at the Istituto Nazionale dei Tumori in Milan, Italy, between 2007 and 2008. The study did not examine asbestos exposure. The authors measured whether three growth-signal receptors (EGFR, PDGFRB, PDGFRA) and their downstream pathways were activated. EGFR and PDGFRB activation at or above control levels was found in 90% and 75% of tumours. All tumours expressed transcripts for the matching signal molecules; no mutations in the receptor gene regions tested, and no receptor gene amplifications, were found. mTOR itself was activated in all but one tumour. They also tested drugs on a peritoneal mesothelioma cell line, STO. Gefitinib slowed growth only at very high concentrations, and these cells carried a KRAS mutation not detected in the original tumour. RAD001 (everolimus) followed by sorafenib inhibited growth more than expected from simple additive effects. The authors concluded that the findings support combining receptor and mTOR inhibitors in DMPM. Other mechanisms may also drive these tumours, they noted.

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 (molecular pathology) study of surgical tumour specimens, combined with in vitro drug tests on a human peritoneal mesothelioma cell line
• Who was studied: Diffuse malignant peritoneal mesothelioma specimens from 20 patients treated by cytoreductive surgery and HIPEC at Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy, between 2007 and 2008 (17 epithelioid, one biphasic, one sarcomatoid, one papillary), plus the STO cell line
• Exposure: No asbestos exposure was studied. The study measured receptor tyrosine kinases (EGFR, PDGFRB, PDGFRA) and downstream signalling in tumour tissue, and tested the drugs gefitinib, RAD001 (everolimus) and sorafenib on the STO cell line
• Main results:
  • In the 20 tumours, EGFR and PDGFRB phosphorylation (activation) at levels similar to or higher than controls was found in 90% and 75% respectively
  • PDGFRA expression was found in 17 tumours (85%), and only 45% of these showed low levels of activation
  • Real-time PCR showed that all tumours expressed c-DNAs (transcripts) encoding the three matching ligands (TGF-alpha, PDGFB, PDGFA); ligand protein was not measured
  • EGFR–PDGFRB paired receptors (heterodimers) were found in all six tumours tested for them
  • No mutations were found in the regions of the EGFR, PDGFRB and PDGFRA genes that were sequenced, and none of the tumours showed receptor gene amplification
  • 12 of the 20 tumours (60%) lacked p16 protein on immunohistochemistry; two of these had a 9p21 homozygous deletion or monosomy of chromosome 9
  • No KRAS or BRAF activating mutations were found in the tumours
  • mTOR was expressed and phosphorylated in all but one tumour
  • TSC1 expression was lower than in matched non-tumour tissue in seven cases (54%)
  • STO cells were resistant to gefitinib (IC50 40.1 plus or minus 1.3 micromolar) and carried a KRAS G12D mutation; the original tumour was KRAS wild-type
  • In STO cells, sorafenib alone had an IC50 of 0.55 plus or minus 0.07 micromolar and RAD001 alone had an IC50 of 15.2 plus or minus 0.8 micromolar; RAD001 for 24 hours followed by sorafenib for 48 hours inhibited growth more than expected from additive effects
  • The share of STO cells undergoing apoptosis after sequential RAD001 then sorafenib reached a peak of 23.5 plus or minus 3.6% at the highest concentrations, compared with 8.6 plus or minus 1.4% with 0.6 micromolar sorafenib alone and under 5% with RAD001 alone
• The authors' conclusion: The authors concluded that EGFR and PDGFRB are activated by their ligands and interact with each other, that they are connected to the downstream mTOR pathway, and that the findings support combined treatment with RTK and mTOR inhibitors in DMPM
• Limitations the authors state:
  • Immunohistochemistry and biochemical results disagreed in eight cases, which the authors suggest may reflect different antibody sensitivity
  • The authors note DMPMs may not be driven only by EGFR and PDGFRB activation, and other escape mechanisms may co-exist
  • Unlike the surgical specimens, the STO cell line carries a KRAS mutation, so the drug results differed from what was originally hypothesised

Topics

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

Medical terms in this study, explained in our Lexicon: Peritoneal Mesothelioma, EGFR, Sorafenib (Nexavar).

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