In vitro anti-mesothelioma activity of cisplatin-gemcitabine combinations: evidence for sequence-dependent effects

Our plain-English summary of In vitro anti-mesothelioma activity of cisplatin-gemcitabine combinations: evidence for sequence-dependent effects, by I. Zanellato, C.D. Boidi, G. Lingua, et al (Cancer Chemotherapy and Pharmacology, 2011).

The study

• Authors: I. Zanellato, C.D. Boidi, G. Lingua, P.G. Betta, S. Orecchia, E. Monti, D. Osella
• Journal: Cancer Chemotherapy and Pharmacology
• Published: 2011;67(2):265-73
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: The present study addresses the optimization of gemcitabine-cisplatin protocols currently adopted in the clinical management of malignant pleural mesothelioma (MPM), using cell lines derived from different histological subtypes of MPM as an in vitro model.

Methods: MPM cell lines were exposed either to single drugs or to their combinations, using a fixed dose ratio. Possible mechanisms for synergistic interactions were investigated by cell cycle analysis, western blot analysis of p53 phosphorylation status, and neutral comet assay to detect double strand breaks.

Results: Four-hour pre-treatment with gemcitabine followed by 68-h exposure to cisplatin was found to exert synergistic activity in both epithelioid and sarcomatoid MPM subtypes, inducing a strong S-phase arrest that correlated with accumulation of double-strand breaks (DSBs).

Conclusion: The antiproliferative effects of the gemcitabine/cisplatin combination in mesothelioma cells can be maximized by pre-treatment with gemcitabine, suggesting that this drug increases cisplatin-induced DSBs by inhibiting DNA adduct repair.

In plain English

This was a laboratory study of human malignant pleural mesothelioma cells grown in dishes. It did not study patients or asbestos exposure. The authors used four cell lines taken from the pleural fluid of untreated patients: two from epithelioid tumours, one sarcomatoid and one mixed. All the patients came from an area with residual pollution from a large asbestos factory. The cells were treated with two chemotherapy drugs, cisplatin and gemcitabine, given together or one after the other. Giving both drugs together for 72 hours produced slight antagonism in the epithelioid lines, an additive trend in the mixed line and synergism (a stronger combined effect than expected) in the sarcomatoid line. Cisplatin first produced strong antagonism in the sarcomatoid line. Gemcitabine for 4 hours followed by cisplatin for 68 hours produced synergism in both an epithelioid and the sarcomatoid line, along with cells piling up in the S phase of the cell cycle. A cisplatin-resistant variant line showed a 3.5-fold higher cisplatin IC50 but no cross-resistance to gemcitabine. The authors concluded that pre-treatment with gemcitabine can maximize the combination's effect.

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: In vitro laboratory experiment on human malignant pleural mesothelioma cell lines
• Who was studied: Four human malignant pleural mesothelioma cell lines from pleural effusions of untreated patients: BR95 and MG06 (epithelioid), MM98 (sarcomatoid) and DE05 (mixed or biphasic, about 80% epithelioid). All the patients came from one geographic area with residual environmental pollution from a large asbestos factory that had been active for over 60 years. The authors also selected a cisplatin-resistant variant, MM98-R, from MM98 in their own laboratory.
• Exposure: The study did not test asbestos exposure. Cells were exposed to the chemotherapy drugs cisplatin and gemcitabine, either alone or in combination at fixed dose ratios. Schedules were: 72-hour continuous treatment; 4-hour treatment followed by 68-hour recovery; or 4 hours of one drug followed by 68 hours of the other.
• Main results:
  • Giving both drugs together for 72 hours produced slight antagonism in the epithelioid BR95 and MG06 lines.
  • With the same 72-hour simultaneous treatment, the mixed DE05 line showed an additive trend and the sarcomatoid MM98 line showed consistent and significant synergism.
  • Giving both drugs together for 4 hours, followed by 68 hours in drug-free medium, produced additive effects in BR95 and MM98 cells.
  • Cisplatin for 4 hours followed by gemcitabine for 68 hours produced a strong antagonistic effect in MM98 and a variable effect in BR95.
  • Gemcitabine for 4 hours followed by cisplatin for 68 hours produced a smooth synergism in the epithelioid BR95 line and a strong synergism in the sarcomatoid MM98 line.
  • In BR95 and MM98 cells treated with gemcitabine followed by cisplatin, a TUNEL assay showed a marked reduction in cell numbers and the presence of apoptotic (dying) cells.
  • Schedules that gave synergism were linked to a strong build-up of cells in the S phase of the cell cycle, with a decrease in the G2/M phase. In the non-synergistic combinations, the G2/M fraction increased or stayed the same.
  • In MM98 cells, cisplatin caused DNA double-strand breaks only after prolonged exposure: 72 hours alone, or after gemcitabine pre-treatment. In BR95 cells, double-strand breaks increased after cisplatin exposure for 4 and 72 hours.
  • The cisplatin-resistant MM98-R cells had a 3.5-fold higher cisplatin IC50 (the dose that halves cell growth) than MM98 cells after 72 hours of continuous exposure (p less than 0.05).
  • MM98-R cells did not show cross-resistance to gemcitabine.
• The authors' conclusion: The authors concluded that the antiproliferative effects of the gemcitabine/cisplatin combination in mesothelioma cells can be maximized by pre-treatment with gemcitabine. They suggested this happens because gemcitabine increases cisplatin-induced double-strand breaks by blocking the repair of DNA adducts.
• Limitations the authors state:
  • The authors stated that further studies are planned using more realistic three-dimensional models alongside the conventional monolayer cultures used here, and using reliable animal models.

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, Cisplatin, Gemcitabine, Pleural Mesothelioma, Histological Subtype, Comet Assay, Epithelioid, Sarcomatoid.

Related studies

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• Prevalence of in vitro chemotherapeutic drug resistance in primary malignant pleural mesothelioma: result in a cohort of 203 resection specimens — A.A. Mujoomdar, T.R. Tilleman, et al. (2010)
• ADP sensitizes ZL55 cells to the activity of cisplatin — A. Muscella, L.G. Cossa, et al. (2019)

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