Repurposing Quinacrine for Treatment of Malignant Mesothelioma: In-Vitro Therapeutic and Mechanistic Evaluation

Our plain-English summary of Repurposing Quinacrine for Treatment of Malignant Mesothelioma: In-Vitro Therapeutic and Mechanistic Evaluation, by N.S. Kulkarni, B. Vaidya, V. Parvathaneni, et al (International Journal of Molecular Sciences, 2020).

The study

• Authors: N.S. Kulkarni, B. Vaidya, V. Parvathaneni, D. Bhanja, V. Gupta
• Journal: International Journal of Molecular Sciences
• Published: 2020;21(17)
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant mesothelioma (MM) is a rare type of cancer primarily affecting mesothelial cells lining the pleural cavity. In this study, we propose to repurpose quinacrine (QA), a widely approved anti-malarial drug, for Malignant Pleural Mesothelioma (MPM) treatment. QA demonstrates high degree of cytotoxicity against both immortalized and primary patient-derived cell lines with sub-micromolar 50% inhibitory concentration (IC50) values ranging from 1.2 µM (H2452) to 5.03 µM (H28). Further, QA also inhibited cellular migration and colony formation in MPM cells, demonstrated using scratch and clonogenic assays, respectively. A 3D-spheroid cell culture experiment was performed to mimic in-vivo tumor conditions, and QA was reported to be highly effective in this simulated cellular model. Anti-angiogenic properties were also discovered for QA. Autophagy inhibition assay was performed, and results revealed that QA successfully inhibited autophagy process in MPM cells, which has been cited to be one of the survival pathways for MPM. Annexin V real-time apoptosis study revealed significant apoptotic induction in MPM cells following QA treatment. Western blots confirmed inhibition of autophagy and induction of apoptosis. These studies highlight anti-mesothelioma efficacy of QA at low doses, which can be instrumental in developing it as a stand-alone treatment strategy for MPM.

In plain English

This laboratory study used cells grown in dishes: no patients or animals were treated, and asbestos exposure was not studied. The authors tested quinacrine, an anti-malarial drug, on five established mesothelioma cell lines and four patient-derived cell lines. After 72 hours, quinacrine concentrations from 1.1 ± 0.2 µM (H2452) to 5.2 ± 1.3 µM (ORT) cut measured cell viability by half. Cisplatin, tested alone, showed minimal effect. The authors reported that quinacrine was less or similarly toxic to normal kidney cells compared with the cancer cells. Quinacrine reduced colony formation in H2452 cells and cell migration in H226 cells. In three-dimensional clusters of MSTO-211H cells given repeated doses for 15 days, cluster volume was 1.1 ± 0.2 mm3 at 10 µM, against 17.2 ± 1.1 mm3 untreated. The authors read further tests as showing blocked autophagy (a cell recycling process), signs of apoptotic cell death, and less blood-vessel-like tube formation by umbilical vein cells. They concluded this lays groundwork for quinacrine as a standalone treatment, but said further preclinical testing is needed and one apoptosis marker may be misleading.

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 study (cell culture experiments, including 3D spheroid models); no human or animal subjects
• Who was studied: Five immortalized mesothelioma cell lines (MSTO-211H, H2452, H226, H28, H2052) from the American Type Culture Collection. Four primary patient-derived cell lines (ROB, HAY, ORT, YOU) obtained from the National Cancer Institute. Normal human embryonic kidney cells (HEK-293) and human umbilical vein endothelial cells (HUVEC) were also used.
• Exposure: The drug quinacrine at concentrations from 0.39 to 10 µM, compared with cisplatin alone in viability tests. Pemetrexed was not tested. Asbestos exposure was not studied.
• Main results:
  • In the immortalized cell lines, quinacrine IC50 values (the concentration reducing measured viability by half after 72 h) were: MSTO-211H 3.9 ± 0.9 µM, H2452 1.1 ± 0.2 µM, H226 1.6 ± 0.03 µM, H28 5.03 ± 0.2 µM, H2052 3.7 ± 0.8 µM.
  • In the patient-derived cell lines, quinacrine IC50 values were: ORT 5.2 ± 1.3 µM, YOU 3.2 ± 0.9 µM, HAY 4.2 ± 1.4 µM, ROB 3.7 ± 0.6 µM.
  • Cisplatin, tested alone, showed minimal efficacy against all cell lines, for example an IC50 of 81.7 µM in H2052.
  • Quinacrine was less or similarly toxic to normal HEK-293 kidney cells compared with the cancer cells.
  • In H2452 cells (the only cell line tested for colony formation), colony growth relative to untreated control was 25.6 ± 5.5% with 1.5 µM quinacrine and 10.2 ± 4.4% with 5 µM.
  • In the scratch (migration) test, done in H226 cells, untreated cells closed 81.3 ± 10.2% of the scratch at 24 h, while cells given 1.5 µM quinacrine closed 41.0 ± 7.5%.
  • In MSTO-211H spheroids given multiple doses, day-15 volumes were 3.1 ± 0.3 mm3 at 5 µM and 1.1 ± 0.2 mm3 at 10 µM, against 17.2 ± 1.1 mm3 in untreated spheroids.
  • In single-dose MSTO-211H spheroids, viability relative to control was 117.5 ± 10.9% at 5 µM (not significant) and 0.2 ± 0.03% at 10 µM.
  • In H2452 cells, the autophagy marker signal rose 1.3 times with 1.5 µM quinacrine and 1.8 times with 5 µM. The authors interpreted this as inhibition of autophagy.
  • In MSTO-211H cells, Annexin V (an apoptosis marker) was 4.1 ± 0.3 times control at 0.39 µM quinacrine and 4.7 ± 0.4 times control at 0.78 µM, after 3 h.
  • In HUVEC tube-formation tests, branching length was 192 ± 109 units at 2.5 µM and 65.7 ± 65.7 units at 5 µM, against 1517.7 ± 799.4 units in control cells.
  • The share of cells in the G2-M phase of the cell cycle was 13.1 ± 1.2% at 2.5 µM and 8.8 ± 1.1% at 5 µM, against 17.5 ± 1.5% in control cells.
• The authors' conclusion: The authors concluded that their in-vitro experiments lay groundwork for quinacrine as a standalone therapy for MPM. They proposed that the main mechanisms are apoptotic induction and autophagic inhibition, with angiogenesis inhibition as a secondary mechanism.
• Limitations the authors state:
  • Results from flat (2D) cell cultures may not translate to preclinical studies.
  • The 3D spheroid model is not close to replacing animal models.
  • Annexin V as an apoptosis marker may be misleading, so follow-up studies are needed to confirm the effect on apoptosis.
  • Toxicity to normal cells was similar to or less than toxicity to cancer cells, which the authors said points to a need for localized delivery.
  • The patient-derived ORT cells did not form intact spheroids, so they were unsuitable for 3D studies.
  • Quinacrine has oral bioavailability issues, and further preclinical testing is needed to predict therapeutic potential and dosing.

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, Mesothelial Cells, Pleural Cavity, Pleural Mesothelioma, Apoptosis.

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