Drug-repositioning screening identified fludarabine and risedronic acid as potential therapeutic compounds for malignant pleural mesothelioma

Our plain-English summary of Drug-repositioning screening identified fludarabine and risedronic acid as potential therapeutic compounds for malignant pleural mesothelioma, by I. Dell'Anno, S.A. Martin, M. Barbarino, et al (Investigational New Drugs, 2021).

The study

• Authors: I. Dell'Anno, S.A. Martin, M. Barbarino, A. Melani, R. Silvestri, M. Bottaro, E. Paolicchi, A. Corrado, M. Cipollini, O. Melaiu, A. Giordano, L. Luzzi, F. Gemignani, S. Landi
• Journal: Investigational New Drugs
• Published: 2021;39(3):644-657
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives Malignant pleural mesothelioma (MPM) is an occupational disease mainly due to asbestos exposure. Effective therapies for MPM are lacking, making this tumour type a fatal disease. Materials and Methods In order to meet this need and in view of a future "drug repositioning" approach, here we screened five MPM (Mero-14, Mero-25, IST-Mes2, NCI-H28 and MSTO-211H) and one SV40-immortalized mesothelial cell line (MeT-5A) as a non-malignant model, with a library of 1170 FDA-approved drugs. Results Among several potential compounds, we found that fludarabine (F-araA) and, to a lesser extent, risedronic acid (RIS) were cytotoxic in MPM cells, in comparison to the non-malignant Met-5A cells. In particular, F-araA reduced the proliferation and the colony formation ability of the MPM malignant cells, in comparison to the non-malignant control cells, as demonstrated by proliferation and colony formation assays, in addition to measurement of the phospho-ERK/total-ERK ratio. We have shown that the response to F-araA was not dependent upon the expression of DCK and NT5E enzymes, nor upon their functional polymorphisms (rs11544786 and rs2295890, respectively). Conclusion This drug repositioning screening approach has identified that F-araA could be therapeutically active against MPM cells, in addition to other tumour types, by inhibiting STAT1 expression and nucleic acids synthesis. Further experiments are required to fully investigate this.

In plain English

This was a laboratory study on cells grown in dishes. No patients or animals were treated. The authors tested 1170 US FDA-approved drugs, each at 10 μM, on five malignant pleural mesothelioma (MPM) cell lines and one non-malignant mesothelial line, MeT-5A. Of 28 drugs that harmed at least three MPM lines but not MeT-5A, the authors focused on fludarabine (F-araA) and risedronic acid (RIS). Fludarabine reduced MPM cell viability at much lower concentrations than MeT-5A needed, and slowed MPM cell growth. Fludarabine at 1 μM and RIS at 10 μM did not affect the growth of two other non-malignant mesothelial cell models, LP-9 and HMC7. At 10 μM, fludarabine also affected MeT-5A in a colony test. RIS was weaker. Its mild activity on MPM cells came at a dose about 300-fold above peak blood levels in people taking it for osteoporosis, so the authors did not study it further. Fludarabine lowered STAT1 protein in three MPM lines (two others had too little STAT1 to judge), and adding ATP restored MPM cell viability. The authors concluded that fludarabine is a candidate drug deserving further investigation, following experiments in living organisms (in vivo).

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) drug-repositioning screen of approved drugs on cell lines, followed by validation experiments on cells
• Who was studied: Cell lines, not people. Nine commercially available cell lines: seven malignant (Mero-14, Mero-25, IST-Mes2, NCI-H28, MSTO-211H, Mero-41, Ren) and two non-malignant (MeT-5A, LP-9). Three primary cultures grown from surgical specimens: MMP1 and MMP2 from pleural mesothelioma patients operated on in Siena, Italy, and HMC7 from a pneumothorax patient. The main screen used five MPM lines and MeT-5A.
• Exposure: Asbestos exposure was not studied. The cells were exposed to a library of 1170 FDA-approved drugs (average concentration 10 μM). Fludarabine (F-araA) and risedronic acid (RIS) were then tested at 0.1 to 100 μM, alongside related drugs and cisplatin.
• Main results:
  • In the screen, 28 compounds were cytotoxic on at least three MPM cell lines and not active on MeT-5A. Drugs already tested in MPM clinical trials were excluded, and the authors focused on F-araA and RIS.
  • F-araA concentrations giving half-maximal effect (EC50) were 20.31 μM for non-malignant MeT-5A. For the MPM lines they were 0.39, 0.03, 0.13, 0.38 and 0.20 μM (Mero-14, Mero-25, IST-Mes-2, NCI-H28, MSTO-211H).
  • RIS EC50s were 46.26 μM for MeT-5A and 5.01, 5.46, 9.30 and 7.12 μM for Mero-14, Mero-25, IST-Mes-2 and MSTO-211H. NCI-H28 was resistant to RIS.
  • In two further MPM lines (Mero-41 and Ren), only F-araA confirmed its activity at 1 μM. RIS was cytotoxic only at 100 μM, and only in Ren cells.
  • In the patient-derived MMP1 cells, F-araA at 12.5 μM reduced cell viability by 60%. RIS at 25 μM reduced it by about 20%.
  • In a 72-hour growth assay, F-araA reduced proliferation of the MPM lines (up to about 90% at 1 μM) but not of MeT-5A.
  • Proliferation of the non-malignant mesothelial models LP-9 and HMC7 was not affected by F-araA at 1 μM or RIS at 10 μM.
  • In the colony formation test, F-araA at 10 μM was toxic to all cell lines, including non-malignant MeT-5A.
  • Cisplatin at 0.625 μM combined with F-araA at 6.25 μM gave a combination index of 0.968, which the authors interpreted as synergy. No synergy was seen for RIS.
  • At 1 μM F-araA, activation of caspases 3 and 7 (markers of cell death) was weak in all cell lines except IST-Mes2. The authors judged that this kind of cell death was not the main mechanism.
  • Response to F-araA did not correlate with levels of the enzymes NT5E and DCK. All cell lines carried the common form of the two genetic variants tested.
  • F-araA lowered STAT1 protein in three MPM lines (Mero-14, Mero-25, NCI-H28) but not in MeT-5A. IST-Mes2 and MSTO-211H had too little STAT1 to be informative.
  • Adding 50 μM ATP together with 1 μM F-araA restored MPM cell viability to the level of untreated cells.
  • RIS showed mild activity on MPM cells at a dose about 300-fold higher than peak blood levels in humans treated for osteoporosis, so the authors did not study RIS further.
• The authors' conclusion: The authors concluded that fludarabine (F-araA) is a candidate drug deserving further investigation, following in vivo experiments. They also wrote that clinical trials of F-araA would be justified and that it might be used in combination with current chemotherapy.
• Limitations the authors state:
  • Few non-malignant mesothelial cell models were available to compare against.
  • Two MPM lines had too little STAT1 to show whether F-araA affected it.
  • The patient-derived MPM cells appeared more resistant to both drugs than the commercial cell lines.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Occupational Disease, Asbestos Exposure, SV40, Mesothelial Cells, MeT-5A Cells.

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