Inhibition of hedgehog signaling reduces the side population in human malignant mesothelioma cell lines

Our plain-English summary of Inhibition of hedgehog signaling reduces the side population in human malignant mesothelioma cell lines, by H.A. Kim, M.C. Kim, N.Y. Kim, et al (Cancer Gene Therapy, 2015).

The study

• Authors: H.A. Kim, M.C. Kim, N.Y. Kim, Y. Kim
• Journal: Cancer Gene Therapy
• Published: 2015;22(8):387-95
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Deregulation of crucial embryonic pathways, including hedgehog signaling, has been frequently implicated in a variety of human cancers and is emerging as an important target for anticancer therapy. This study evaluated the potential anticancer effects of cyclopamine, a chemical inhibitor of hedgehog signaling, in human malignant mesothelioma (HMM) cell lines. Cyclopamine treatment significantly decreased the proliferation of HMM cells by promoting apoptosis and shifting the cell cycle toward dormant phase. The clonogenicity and mobility of HMM cells were significantly decreased by cyclopamine treatment. Treatment of HMM cells with cyclopamine significantly reduced the abundance of side population cells, which were measured using an assay composed of Hoechst 33342 dye staining and subsequent flow cytometry. Furthermore, the expression levels of stemness-related genes were significantly affected by cyclopamine treatment. Taken together, the present study showed that targeting hedgehog signaling could reduce a more aggressive subpopulation of the cancer cells, suggesting an alternative approach for HMM therapy.

In plain English

This laboratory study tested cyclopamine, a chemical that blocks a cell-signaling pathway called hedgehog, on human malignant mesothelioma cell lines grown in dishes. It did not study people or asbestos exposure. The authors first measured hedgehog pathway proteins in seven mesothelioma cell lines and one non-malignant mesothelial cell line. They then ran most tests on one line, MS1, using tomatidine, a chemical of similar structure, as a comparison. In MS1 cells, cyclopamine reduced cell growth and cell movement. At 20 micromolar it raised the share of cells in resting phases (G0 and G1) from 47.55 to 59.9%, and early programmed cell death (apoptosis) rose from 1.5 to 2.8%. Cyclopamine did not change the total number of colonies the cells formed but shifted them toward smaller colonies. It significantly reduced the 'side population', a small group of cells with stem-cell-like features, while tomatidine did not. The authors concluded this supports future clinical investigation of hedgehog signaling as a treatment target. They said the reason the side population shrank is unclear.

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) cell-line experiment
• Who was studied: Seven human malignant mesothelioma cell lines (epithelioid, biphasic and sarcomatoid types) and one SV40-transformed non-malignant mesothelial cell line (Met5A); most treatment experiments used the MS1 cell line
• Exposure: No asbestos exposure was studied. Cells were treated with cyclopamine, a hedgehog signaling inhibitor, usually at 10 and 20 micromolar. Tomatidine was used as a comparison chemical and DMSO (the solvent) as the untreated control.
• Main results:
  • Compared with solvent-treated cells, 20 micromolar cyclopamine for 48 hours reduced cell proliferation by about 21% in MS1 cells and 43% in H513 cells. The data for this finding were not shown.
  • Migration of MS1 cells was reduced by 10 and 20 micromolar cyclopamine compared with untreated cells.
  • With 10 micromolar cyclopamine, the total number of MS1 colonies was similar to untreated cells, but there were more small colonies and fewer medium and large colonies.
  • The side population fraction of MS1 cells was significantly decreased by 10 and 20 micromolar cyclopamine for 24 hours. It was not significantly changed by tomatidine.
  • In MS1 cells treated with 20 micromolar cyclopamine, cells in the G0 and G1 phases increased from 47.55 to 59.9%, and cells in the G2 and M phases fell from 29.9 to 19.1%.
  • In MS1 cells, cyclopamine increased early apoptotic cells from 1.5 to 2.8% and late apoptotic cells from 1.2 to 1.6%.
  • In MS1 cells, cyclopamine increased expression of the stemness gene SOX2, decreased OCT4, and did not significantly alter NANOG.
• The authors' conclusion: The authors concluded that inhibiting the hedgehog pathway markedly reduced the side population in mesothelioma cell lines. They said this supports future clinical investigation of hedgehog signaling as a target for mesothelioma therapy.
• Limitations the authors state:
  • The authors stated that the mechanism behind the reduction of the side population is unclear.
  • The authors noted that ABCG2 was measured in the whole cell population, which may not reflect changes in the small side population.
  • The authors stated that interactions between the hedgehog and Akt pathways in these cell lines need further study.

Topics

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

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

Related studies

• Targeting of the Hedgehog signal transduction pathway suppresses survival of malignant pleural mesothelioma cells in vitro — M. You, J. Varona-Santos, et al. (2014)
• Characterization of side population cells in human malignant mesothelioma cell lines — K. Kai, S. D'Costa, et al. (2010)
• Antagonizing the Hedgehog Pathway with Vismodegib Impairs Malignant Pleural Mesothelioma Growth In Vivo by Affecting Stroma — M. Meerang, K. Bérard, et al. (2016)
• Targeted proteasome inhibition by Velcade induces apoptosis in human mesothelioma and breast cancer cell lines — Y. Wang, A.K. Rishi, et al. (2010)
• Gli as a novel therapeutic target in malignant pleural mesothelioma — H. Li, N. Lui, et al. (2013)
• Modulation of Calretinin Expression in Human Mesothelioma Cells Reveals the Implication of the FAK and Wnt Signaling Pathways in Conferring Chemoresistance towards Cisplatin — J. Wörthmüller, V. Salicio, et al. (2019)

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