FTY720 inhibits mesothelioma growth in vitro and in a syngeneic mouse model

Our plain-English summary of FTY720 inhibits mesothelioma growth in vitro and in a syngeneic mouse model, by A. Szymiczek, S. Pastorino, D. Larson, et al (Journal of Translational Medicine, 2017).

The study

• Authors: A. Szymiczek, S. Pastorino, D. Larson, M. Tanji, L. Pellegrini, J. Xue, S. Li, C. Giorgi, P. Pinton, Y. Takinishi, H.I. Pass, H. Furuya, G. Gaudino, A. Napolitano, M. Carbone, H. Yang
• Journal: Journal of Translational Medicine
• Published: 2017;15(1):58
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant mesothelioma (MM) is a very aggressive type of cancer, with a dismal prognosis and inherent resistance to chemotherapeutics. Development and evaluation of new therapeutic approaches is highly needed. Immunosuppressant FTY720, approved for multiple sclerosis treatment, has recently raised attention for its anti-tumor activity in a variety of cancers. However, its therapeutic potential in MM has not been evaluated yet.

Methods: Cell viability and anchorage-independent growth were evaluated in a panel of MM cell lines and human mesothelial cells (HM) upon FTY720 treatment to assess in vitro anti-tumor efficacy. The mechanism of action of FTY720 in MM was assessed by measuring the activity of phosphatase protein 2A (PP2A)-a major target of FTY720. The binding of the endogenous inhibitor SET to PP2A in presence of FTY720 was evaluated by immunoblotting and immunoprecipitation. Signaling and activation of programmed cell death were evaluated by immunoblotting and flow cytometry. A syngeneic mouse model was used to evaluate anti-tumor efficacy and toxicity profile of FTY720 in vivo.

Results: We show that FTY720 significantly suppressed MM cell viability and anchorage-independent growth without affecting normal HM cells. FTY720 inhibited the phosphatase activity of PP2A by displacement of SET protein, which appeared overexpressed in MM, as compared to HM cells. FTY720 promoted AKT dephosphorylation and Bcl-2 degradation, leading to induction of programmed cell death, as demonstrated by caspase-3 and PARP activation, as well as by cytochrome c and AIF intracellular translocation. Moreover, FTY720 administration in vivo effectively reduced tumor burden in mice without apparent toxicity.

Conclusions: Our preclinical data indicate that FTY720 is a potentially promising therapeutic agent for MM treatment.

In plain English

This was a laboratory study of a drug, not a study of people or of asbestos exposure. The authors tested FTY720 (fingolimod), a multiple sclerosis drug, on malignant mesothelioma cells in the lab and on mesothelioma tumors in mice. In human mesothelioma cell lines, FTY720 lowered cell viability, and the effect grew with the dose. Normal mesothelial cells from three non-cancer patients showed no significant change. Treated REN and PHI cells formed fewer and smaller colonies in soft agar, but migration of MILL and PHI cells did not change. The mesothelioma cells had lower activity of an enzyme called PP2A than normal cells, and higher levels of its inhibitors SET and CIP2A. FTY720 raised PP2A activity, pulled SET away from PP2A, and reduced the activity of another enzyme, SphK1. Treated cells showed signs of programmed cell death. In Balb/c mice with mouse mesothelioma tumors (15 per group), FTY720 at 10 mg/kg reduced average tumor volume by 60% compared with vehicle. The mice showed no significant weight loss and no visible organ abnormalities. The authors concluded that their data were a proof of principle for FTY720 in mesothelioma therapy.

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 (preclinical) study: experiments on cells grown in the lab plus an animal experiment in a syngeneic mouse model
• Who was studied: A panel of human malignant mesothelioma cell lines (PPM-MILL, PHI, HMESO, REN, NCI-H226, NCI-H2052, NCI-H2452); normal human mesothelial cells from pleural effusions of three non-cancer patients; AB1 mouse mesothelioma cells; and eight-week-old Balb/c mice, 15 per group
• Exposure: The drug FTY720 (not asbestos). In cells it was given at 0.5 to 10 µM, 2 µM in colony and migration assays, and 6 µM in mechanism experiments. Mice received 10 mg/kg FTY720 or vehicle by injection into the abdomen, 5 days on and 2 days off.
• Main results:
  • After 48 hours, FTY720 caused a significant, dose-dependent decrease in viability of all mesothelioma cell lines tested. No significant change was seen in normal mesothelial cells.
  • In soft agar, REN and PHI mesothelioma cells treated with FTY720 formed significantly fewer colonies than vehicle-treated cells (P = 0.0145 for REN; P = 0.0006 for PHI).
  • The colonies of FTY720-treated REN and PHI cells were also significantly smaller (P less than 0.0001 for both cell lines).
  • A 3-hour treatment with 2 µM FTY720 did not change migration of MILL and PHI mesothelioma cells.
  • The phosphorylated form of the drug, FTY720-P, did not suppress mesothelioma cell viability.
  • PP2A activity was significantly lower in mesothelioma cells than in normal mesothelial cells.
  • All six mesothelioma cell lines tested had significantly higher levels of the PP2A inhibitors SET and CIP2A than normal mesothelial cells.
  • FTY720 separated SET from PP2A in mesothelioma cells.
  • FTY720 significantly reduced SphK1 activity in mesothelioma cells.
  • After FTY720 treatment, the share of early and late apoptotic (dying) cells rose by an average of about 9% and 11% respectively.
  • FTY720 reduced viability of AB1 mouse mesothelioma cells in the lab, with a GI50 (the dose that halves growth) of 5 µM.
  • In mice, FTY720 at 10 mg/kg reduced tumor volume by an average of 60% at the end of treatment compared with vehicle (P = 0.0009).
  • Average tumor weight was significantly lower in FTY720-treated mice (P = 0.0065).
  • Treated mice showed no significant weight loss and no observed changes in grooming, posture, hydration, stools or social behavior.
  • No spleen enlargement, discoloration or other abnormalities of internal organs were seen in treated mice.
• The authors' conclusion: The authors concluded that their data were a proof of principle for the efficacy of FTY720 in mesothelioma therapy, with no apparent toxicity in their mouse model.

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, Prognosis, Mesothelial Cells, Translocation, Tumor Burden.

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