Role of protein kinase C β and vascular endothelial growth factor receptor in malignant pleural mesothelioma: Therapeutic implications and the usefulness of Caenorhabditis elegans model organism

Our plain-English summary of Role of protein kinase C β and vascular endothelial growth factor receptor in malignant pleural mesothelioma: Therapeutic implications and the usefulness of Caenorhabditis elegans model organism, by S. Loganathan, R. Kanteti, S.S. Siddiqui, et al (Journal of Carcinogenesis, 2011).

The study

• Authors: S. Loganathan, R. Kanteti, S.S. Siddiqui, E. El-Hashani, M. Tretiakova, H. Vigneswaran, G. Cervantes, V. Natarajan, A.N. Husain, E.E. Vokes, H.L. Kindler, R. Salgia
• Journal: Journal of Carcinogenesis
• Published: 2011;10:4
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Purpose: To examine the role of both protein kinase C (PKC)-β and vascular endothelial growth factor receptor (VEGFR)-2 in malignant pleural mesothelioma (MPM) using respective inhibitors, enzastaurin and KRN633.

Materials And Methods: MPM cell lines, control cells, and a variety of archived MPM tumor samples were used to determine the protein expression levels of PKC-β, VEGFR-2, VEGF, and p-AKT. Effects of enzastaurin and KRN633 on phosphorylation status of key signaling molecules and viability of the mesothelioma cells were determined. The common soil nematode, Caenorhabditis elegans, was treated with enzastaurin to determine its suitability to screen for highly potent kinase inhibitors.

Results: PKC-β1, PKC-β2 and VEGFR-2/KDR were overexpressed in MPM cell lines and MPM tumor tissues. Enzastaurin treatment resulted in significant loss in viability of VEGF induced cell proliferation; however, the effect of KRN633 was much less. Enzastaurin also dramatically decreased the phosphorylation of PKC-β, its downstream target p-AKT, and surprisingly, the upstream VEGFR-2. The combination of the two drugs at best was additive and similar results were obtained with respect to cell viability. Treatment of C. elegans with enzastaurin resulted in clear phenotypic changes and the worms were hypermotile with abnormal pattern and shape of eggs, suggesting altered fecundity.

Conclusions: PKC-β1 and VEGFR-2 are both excellent therapeutic targets in MPM. Enzastaurin was better at killing MPM cells than KRN633 and the combination lacked synergy. In addition, we show here that C. elegans can be used to screen for the next generation inhibitors as treatment with enzastaurin resulted in clear phenotypic changes that could be assayed.

In plain English

This laboratory study examined two signaling proteins, PKC-β and VEGFR-2, in malignant pleural mesothelioma (MPM). It tested two drugs that block them: enzastaurin, which blocks PKC-β, and KRN633, which blocks VEGFR-2. The authors used mesothelioma cell lines, non-cancerous mesothelial cells (Met5A), 42 archived MPM tumor samples with 10 non-tumor control tissues, and a small worm, Caenorhabditis elegans. VEGFR-2 and PKC-β proteins were generally higher in MPM cell lines than in Met5A cells. Strong VEGF, VEGFR-2 and PKC-β1 expression was much more frequent in epithelioid than in sarcomatoid tumors. Enzastaurin reduced mesothelioma cell growth in a dose-dependent way, while Met5A cells survived. In one cell line, H2461, each drug reduced VEGF-triggered protein activation, and the two together had an additive effect. Higher enzastaurin doses caused hyperactive movement, body defects and abnormal egg arrangement in the worms. The authors concluded that this pathway is highly active in MPM and essential for MPM cell survival, and that enzastaurin killed MPM cells better than KRN633. They also concluded that the worm could be used for drug screening. In the discussion, they reported a preliminary experiment in which chrysotile fibers reduced worm survival and caused movement defects.

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 study: protein measurements in mesothelioma cell lines and archived tumor tissue (tissue microarray), drug tests on cultured cells, and drug exposure experiments in the nematode C. elegans
• Who was studied: 42 archived MPM tumor samples (29 epithelioid, 9 sarcomatoid) and 10 non-tumor lung and pleura control tissues, University of Chicago. Also nine MPM cell lines, non-malignant mesothelial cells (Met5A), human umbilical vein endothelial cells (HUVEC), and wild-type C. elegans N2 worms.
• Exposure: Drug exposures: enzastaurin (PKC-β inhibitor, 1 to 6 µM in cell growth tests, 2.5 µM in combination tests) and KRN633 (VEGFR-2 inhibitor, 1 µg/ml). Worms were exposed to enzastaurin. Asbestos exposure was not studied in the patients or tumor samples.
• Main results:
  • In cell lines, VEGFR-2, PKC-β1 and PKC-β2 levels were generally higher in the MPM cell lines than in non-malignant Met5A cells.
  • In tumor tissue, strong expression of VEGF, VEGFR-2 and PKC-β1 was much more frequent in epithelioid samples than in sarcomatoid samples.
  • Enzastaurin (1 to 6 µM) reduced growth of mesothelioma cell lines in a dose-dependent way. H2461 was the most sensitive line and H2052 the least sensitive. Met5A control cells survived across a wide range of concentrations (data not shown).
  • Enzastaurin and KRN633, alone or combined, had no discernable effect on Met5A cell survival. Viability of the mesothelioma cell lines was significantly lower than in controls.
  • In H2461 mesothelioma cells, each drug alone considerably inhibited VEGF-induced phosphorylation of VEGFR-2, PKC-β2 and AKT. The combination gave additive inhibition in H2461 cells but not in Met5A cells.
  • In C. elegans, enzastaurin at 1 to 5 µM caused no behavioral or body changes. At higher concentrations, worms showed uncoordinated hyperactive movement, body defects and abnormal arrangement of eggs.
  • In the discussion, the authors reported a preliminary experiment, with no numbers given, in which worms cultured for 2 weeks with chrysotile fibers had reduced survival and locomotion defects.
• The authors' conclusion: The authors concluded that the signaling pathway linking VEGFR, PKC and AKT is highly active in MPM and essential for MPM cell survival. They concluded that enzastaurin was more effective than KRN633 at killing MPM cells, that the combination was additive, and that C. elegans can be used to study PKC signaling for drug screening.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Mesothelioma.

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