Indolyl-chalcone derivatives trigger apoptosis in cisplatin-resistant mesothelioma cells through aberrant tubulin polymerization and deregulation of microtubule-associated proteins

Our plain-English summary of Indolyl-chalcone derivatives trigger apoptosis in cisplatin-resistant mesothelioma cells through aberrant tubulin polymerization and deregulation of microtubule-associated proteins, by S. Steinlein, F. Essmann, A.F. Ghilardi, et al (Frontiers in Oncology, 2023).

The study

• Authors: S. Steinlein, F. Essmann, A.F. Ghilardi, H. Horn, J. Schüler, A. Hausser, L. Sun, G. Ott, C. Kalla
• Journal: Frontiers in Oncology
• Published: 2023;13:1190988
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: Malignant pleural mesothelioma (MPM) is a neoplasm with dismal prognosis and notorious resistance to the standard therapeutics cisplatin and pemetrexed. Chalcone derivatives are efficacious anti-cancer agents with minimal toxicity and have, therefore, gained pharmaceutical interest. Here, we investigated the efficacy of CIT-026 and CIT-223, two indolyl-chalcones (CITs), to inhibit growth and viability of MPM cells and defined the mechanism by which the compounds induce cell death.

Methods: The effects of CIT-026 and CIT-223 were analyzed in five MPM cell lines, using viability, immunofluorescence, real-time cell death monitoring, and tubulin polymerization assays, along with siRNA knockdown. Phospho-kinase arrays and immunoblotting were used to identify signaling molecules that contribute to cell death.

Results: CIT-026 and CIT-223 were toxic in all cell lines at sub-micromolar concentrations, in particular in MPM cells resistant to cisplatin and pemetrexed, while normal fibroblasts were only modestly affected. Both CITs targeted tubulin polymerization via (1) direct interaction with tubulin and (2) phosphorylation of microtubule regulators STMN1, CRMP2 and WNK1. Formation of aberrant tubulin fibers caused abnormal spindle morphology, mitotic arrest and apoptosis. CIT activity was not reduced in CRMP2-negative and STMN1-silenced MPM cells, indicating that direct tubulin targeting is sufficient for toxic effects of CITs.

Discussion: CIT-026 and CIT-223 are highly effective inducers of tumor cell apoptosis by disrupting microtubule assembly, with only modest effects on non-malignant cells. CITs are potent anti-tumor agents against MPM cells, in particular cells resistant to standard therapeutics, and thus warrant further evaluation as potential small-molecule therapeutics in MPM.

Copyright © 2023 Steinlein, Essmann, Ghilardi, Horn, Schüler, Hausser, Sun, Ott and Kalla.

In plain English

This laboratory study tested two experimental compounds, indolyl-chalcones called CIT-026 and CIT-223, on malignant pleural mesothelioma (MPM) cells grown in culture. No patients were treated, and asbestos exposure was not studied. The authors used five MPM cell lines and normal fibroblasts from two individuals. After 72 hours, both compounds reduced viability in all five cell lines at sub-micromolar concentrations. The IC50 was 0.15 to 0.33 µM for CIT-026 and 0.02 to 0.31 µM for CIT-223. This held for lines that were resistant to cisplatin and partly resistant to pemetrexed. Fibroblasts were not significantly affected at 0.3 µM and were modestly affected at 3 µM. In two lines, PXF698 and PXF1752, the compounds caused abnormal tubulin fibers and mitotic spindles, a 2.8-fold to 5.5-fold increase in mitotic nuclei compared with control cells, and apoptotic cell death. In these two lines they also increased phosphorylation of STMN1 and CRMP2, but knocking down STMN1 did not block the activity of CIT-026. Computer docking placed both compounds in the colchicine binding site of tubulin. The authors concluded that the compounds warrant further in vivo and clinical investigation.

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) study on cell lines, with a cell-free tubulin polymerization assay and computer molecular modeling
• Who was studied: Five malignant pleural mesothelioma cell lines: two conventional lines (NCI-H2052, MSTO-211H) and three patient-derived xenograft cell lines (PXF698, PXF1118, PXF1752). Normal fibroblasts from two individuals served for comparison.
• Exposure: The experimental compounds CIT-026 and CIT-223 (indolyl-chalcones), at 0.01 to 3.0 µM for 72 hours in the viability tests. Asbestos exposure was not studied.
• Main results:
  • Both compounds reduced viability in all five MPM cell lines at sub-micromolar concentrations: IC50 0.15 to 0.33 µM for CIT-026 and 0.02 to 0.31 µM for CIT-223
  • PXF698 and PXF1752 cells, which were resistant to cisplatin and partly resistant to pemetrexed, were sensitive to CIT-026 and responded best to CIT-223 (IC50 0.02 to 0.04 µM)
  • In normal fibroblasts, viability was not significantly affected at 0.3 µM of either compound. The fibroblasts were modestly affected at the higher concentration of 3 µM.
  • The authors estimated that the effect of the compounds on viability was at least ten times stronger on tumor cells than on non-tumor cells
  • At 1 µM, both compounds produced an apoptotic pattern in PXF698 and PXF1752 cells. Membrane integrity was lost 8 to 12 hours after phosphatidylserine exposure.
  • In PXF698 and PXF1752 cells, treatment caused abnormal spindles and a 2.8-fold to 5.5-fold increase in mitotic nuclei compared with control cells
  • With purified tubulin, both compounds sped up tubulin polymerization but did not stabilize microtubules
  • Phosphorylation of STMN1 and CRMP2 rose with dose and time in PXF698 and PXF1752 cells
  • Knocking down STMN1 in MPM cells (PXF698 and PXF1752) did not block the activity of CIT-026
  • According to the Discussion, the compounds had similar efficacy in CRMP2-positive and CRMP2-negative MPM cells
  • In computer modeling, both compounds were docked into the colchicine binding site of tubulin
• The authors' conclusion: The authors concluded that CIT-026 and CIT-223 are promising agents for MPM tumors resistant to standard therapeutics, among others, and warrant further in vivo and clinical investigation

Topics

Medical terms in this study, explained in our Lexicon: Apoptosis, Cisplatin, Mesothelioma, Pleural Mesothelioma, Neoplasm, Prognosis, Pemetrexed (Alimta), Fibroblast.

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