A 5-aza-2'-deoxycytidine/valproate combination induces cytotoxic T-cell response against mesothelioma

Our plain-English summary of A 5-aza-2'-deoxycytidine/valproate combination induces cytotoxic T-cell response against mesothelioma, by S. Leclercq, F. Gueugnon, B. Boutin, et al (The European Respiratory Journal, 2011).

The study

• Authors: S. Leclercq, F. Gueugnon, B. Boutin, F. Guillot, C. Blanquart, A. Rogel, M. Padieu, D. Pouliquen, J.F. Fonteneau, M. Grégoire
• Journal: The European Respiratory Journal
• Published: 2011;38(5):1105-16
• Cited by: 34 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Malignant pleural mesothelioma (MPM) is an aggressive tumour with a limited response to conventional therapy. The aim of this study was to evaluate the anticancer effect of a DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (5-azaCdR), and two histone deacetylase inhibitors, valproic acid (VPA) and suberoylanilide hydroxamic acid (SAHA). Human mesothelioma cells were treated with each epigenetic drug, either alone or in combinations. The cytotoxic effects on treated cells and the expression of specific tumour antigens were evaluated. The recognition of treated cells by a specific CD8+ T-cell clone was also measured. Additionally, the effect of combined treatments was tested in a murine model of mesothelioma. We showed that VPA and SAHA synergised with 5-azaCdR to kill MPM cells and induce tumour antigen expression in the remaining living tumour cells. As a consequence, tumour cells expressing these antigens were recognised and lysed by specific CD8+ cytotoxic T-cells. In vivo, treatment with 5-azaCdR/VPA inhibited tumour growth, and promoted lymphocyte infiltration and an immune response against tumour cells. Appropriate epigenetic drug combinations, in addition to inducing mesothelioma cell death, also affect the immunogenic status of these cells. This property could be exploited in clinical investigations to develop MPM treatments combining chemotherapeutic and immunotherapeutic approaches.

In plain English

This was a laboratory study of drugs that change how genes are switched on, tested against malignant pleural mesothelioma. It did not study asbestos exposure. The authors treated human mesothelioma cell lines with 5-aza-2'-deoxycytidine (5-azaCdR), valproic acid (VPA) and SAHA, alone and in sequence. VPA and SAHA killed mesothelioma cells. 5-azaCdR did not, but it switched on the tumour marker NY-ESO-1, which was absent from all untreated lines. It also induced or increased MAGE-A1 and MAGE-A3, which were absent from half of the untreated lines. Giving 5-azaCdR before VPA produced the highest NY-ESO-1 levels. Normal mesothelial cells did not express NY-ESO-1 after treatment. NY-ESO-1-specific immune T-cells recognised treated cell lines of the matching tissue type, and killed one treated line. Mice were injected in the abdomen with mouse mesothelioma cells. Average tumour mass was 261.7 mg in 10 untreated mice and 99.8 mg in 6 mice given both drugs (p less than 0.05). The authors concluded that these sequential combinations are potential new strategies to kill mesothelioma cells and to change the immune response to surviving, drug-resistant cells.

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 using human mesothelioma cell lines (in vitro) and a mouse model of mesothelioma (animal experiment)
• Who was studied: Human epithelioid mesothelioma cell lines, established from pleural effusions in the authors' laboratory in Nantes, France (four to six cell lines depending on the experiment). Also two primary cultures of normal mesothelial cells from pleural biopsies of cardiac surgery patients. Also C57BL/6 mice injected intraperitoneally with AK7 mouse mesothelioma cells (10 untreated mice; 6 mice in each treated group).
• Exposure: No asbestos exposure was studied. The exposures were three drugs, given alone and in sequential combinations: 5-aza-2'-deoxycytidine (5-azaCdR, a DNA methyltransferase inhibitor), and two histone deacetylase inhibitors, valproic acid (VPA) and suberoylanilide hydroxamic acid (SAHA). Mice received three injections of 5-azaCdR (4 mg per kg), VPA in their drinking water, or both.
• Main results:
  • In mesothelioma cell lines, VPA or SAHA alone triggered tumour cell death after 48 hours. The median inhibitory concentration was printed as 10 for each drug, but the concentration unit is damaged by scanning.
  • 5-azaCdR alone showed no toxicity and no obvious effect on proliferation of mesothelioma cells.
  • Before treatment, NY-ESO-1 was undetectable in all mesothelioma cell lines, and MAGE-A1 and MAGE-A3 were undetectable in half of the tested cell lines.
  • In mesothelioma cell lines, 5-azaCdR induced or increased expression of NY-ESO-1, MAGE-A1 and MAGE-A3 in a dose-dependent manner. VPA or SAHA alone had no effect on expression of these antigens.
  • Giving 5-azaCdR first and then VPA was associated with much higher NY-ESO-1 expression than the reverse order, in all mesothelioma cell lines tested.
  • In two primary cultures of normal mesothelial cells, NY-ESO-1 was not detected either before or after 5-azaCdR/VPA treatment.
  • In mesothelioma cell lines, combining 5-azaCdR with VPA or with SAHA led to 50% inhibition of cell proliferation, compared with 40% when the HDAC inhibitor was used alone.
  • The NY-ESO-1-specific CD8+ T-cell clone recognised all 5-azaCdR/VPA-treated HLA-A2-positive mesothelioma cell lines, but at lower levels than the melanoma cell line M117. Untreated tumour cells drew no response.
  • The T-cell clone did not kill untreated mesothelioma cells. It did kill mesothelioma cells treated with 5-azaCdR/VPA or pulsed with NY-ESO-1 peptide.
  • In mice with AK7 mesothelioma tumours, mean tumour mass (plus or minus SEM) was: 261.7 plus or minus 43.5 mg untreated (n=10); 199.2 plus or minus 32.5 mg with 5-azaCdR alone (n=6); 135 plus or minus 18.7 mg with VPA alone (n=6); and 99.8 plus or minus 22.1 mg with the 5-azaCdR/VPA combination (n=6). Only the combination was marked significant (p less than 0.05).
  • Tumours from mice given the combination had more lymphocyte aggregates: an average of 6 per tumour section, versus 0 in untreated mice.
  • Against AK7 tumour cells, CD8a+ spleen T-cells from treated mice (n=5) gave more interferon-gamma-secreting cells than those from untreated mice (n=5): 80 plus or minus 6 versus 18 plus or minus 4 spots per 5 x 10^5 cells. Against AK7 cells that had themselves been treated with the drugs, the count was 154 plus or minus 9.
  • CD8a+ lymphocytes could be isolated from the tumours of treated mice but not from untreated mice. These cells responded more to treated AK7 cells (28 plus or minus 2 spots per 1 x 10^5 cells) than to untreated AK7 cells (10 plus or minus 2).
• The authors' conclusion: The authors concluded that sequential 5-azaCdR/VPA or 5-azaCdR/SAHA treatments represent potential new strategies to induce mesothelioma cell death and to modulate the immunogenicity of the remaining, drug-resistant tumour cells. They said combining such drugs with immunotherapy should be evaluated in the future.
• Limitations the authors state:
  • The authors noted that in clinical studies, patients received 5-azaCdR, SAHA or VPA at doses below those used in this study.

Topics

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

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

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