A specific inhibitor of lactate dehydrogenase overcame the resistance toward gemcitabine in hypoxic mesothelioma cells, and modulated the expression of the human equilibrative transporter-1

Our plain-English summary of A specific inhibitor of lactate dehydrogenase overcame the resistance toward gemcitabine in hypoxic mesothelioma cells, and modulated the expression of the human equilibrative transporter-1, by E. Giovannetti, L.G. Leon, V.E. Gómez, et al (Nucleosides, Nucleotides & Nucleic Acids, 2016).

The study

• Authors: E. Giovannetti, L.G. Leon, V.E. Gómez, P.A. Zucali, F. Minutolo, G.J. Peters
• Journal: Nucleosides, Nucleotides & Nucleic Acids
• Published: 2016;35(10-12):643-651
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Malignant pleural mesothelioma (MPM) is a very hypoxic malignancy, and hypoxia has been associated with resistance towards gemcitabine. The muscle-isoform of lactate dehydrogenase (LDH-A) constitutes a major checkpoint for the switch to anaerobic glycolysis. Therefore we investigated the combination of a new LDH-A inhibitor (NHI-1) with gemcitabine in MPM cell lines. Under hypoxia (O2 tension of 1%) the cell growth inhibitory effects of gemcitabine, were reduced, as demonstrated by a 5- to 10-fold increase in IC50s. However, the simultaneous addition of NHI-1 was synergistic (combination index < 1). Flow cytometry demonstrated that hypoxia caused a G1 arrest, whereas the combination of NHI-1 significantly increased gemcitabine-induced cell death. Finally, the mRNA expression levels of the human equilibrative transporter-1 (hENT1) were significantly down-regulated under hypoxia, but treatment with NHI-1 was associated with a recovery of hENT1 expression. In conclusion, our data show that hypoxia increased MPM resistance to gemcitabine. However, cell death induction and modulation of the key transporter in gemcitabine uptake may contribute to the synergistic interaction of gemcitabine with the LDH-A inhibitor NHI-1 and support further studies for the rational development of this combination.

In plain English

This was a laboratory study of cancer cells in culture, not of patients. The authors tested the chemotherapy drug gemcitabine alone and with NHI-1, an experimental compound that blocks the enzyme lactate dehydrogenase A (LDH-A). They used four human malignant pleural mesothelioma cell lines in normal or low (1%) oxygen. The gemcitabine concentration halving cell growth ranged from 43.6 nM (MSTO-211H) to 103.5 nM (H28) and rose up to 5- and 10-fold under low oxygen. Under low oxygen, adding NHI-1 to gemcitabine was synergistic against growth in all four lines. In H28 and H2052, the two lines used for further tests, the combination markedly increased cell death compared with gemcitabine alone. NHI-1 at 50 micromolar caused no appreciable growth inhibition in one normal immortalized mesothelial cell line, AG07086. In both lines, low oxygen lowered the mRNA of hENT1, a protein that carries gemcitabine into cells, by almost 50%. In H28 cells, NHI-1 brought it back to a level comparable to normal oxygen. The authors concluded the combination should be tested in further in vivo studies. They noted that two cell lines cannot represent human mesothelioma's diversity.

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) study of human mesothelioma cell lines treated with drugs under normal and low oxygen
• Who was studied: Four human malignant pleural mesothelioma (MPM) cell lines from ATCC: NCI-H28 and NCI-H2052 (sarcomatoid), NCI-H2452 (epithelioid) and MSTO-211H (biphasic). One normal immortalized mesothelial cell line (AG07086) was also used for growth-inhibition tests. Mechanistic studies (cell cycle, cell death, gene expression) used H28 and H2052 cells. No patients were studied.
• Exposure: Drug treatments, not asbestos: gemcitabine (0.001 to 1 μM for 72 hours), alone or with the LDH-A inhibitor NHI-1 (1 μM in hypoxia, 10 μM in normoxia). Cells were kept in normal oxygen or hypoxia (1% oxygen).
• Main results:
  • Gemcitabine IC50 values (concentration halving cell growth) were 55.1, 43.6, 61.2 and 103.5 nM in H2052, MSTO-211H, H2452 and H28 cells, respectively.
  • Under hypoxia, gemcitabine IC50 values increased up to 5- and 10-fold.
  • Under hypoxia, gemcitabine given together with NHI-1 was synergistic against cell growth (combination index below 0.8) in all the cell lines.
  • NHI-1 at 50 μM caused no appreciable growth inhibition in the normal immortalized mesothelial cells (AG07086).
  • The H28 and H2052 cells, both sarcomatoid, were selected for the mechanistic studies.
  • In the two mesothelioma cell lines studied, hypoxia inhibited the G1/S transition of the cell cycle and reduced gemcitabine-induced cell death.
  • In these two cell lines under hypoxia, NHI-1 alone minimally affected the cell cycle, but with gemcitabine it markedly increased cell death compared with gemcitabine alone.
  • Under hypoxia, hENT1 mRNA fell by almost 50% in both cell lines tested (p less than 0.05). dCK mRNA was only slightly reduced (data not shown).
  • In H28 cells, NHI-1 restored hENT1 expression to a level comparable to normoxia.
• The authors' conclusion: The authors concluded that gemcitabine plus the LDH-A inhibitor increased cell death and favorably modulated gemcitabine transport. They proposed testing the combination in further in vivo studies toward new regimens against MPM.
• Limitations the authors state:
  • The mechanistic studies used only two cell lines, which the authors state cannot represent the heterogeneity and complexity of human MPM.

Topics

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

Medical terms in this study, explained in our Lexicon: Lactate Dehydrogenase (LDH), Gemcitabine, Mesothelioma, Pleural Mesothelioma, Hypoxia.

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