Cariporide Enhances the DNA Damage and Apoptosis in Acid-tolerable Malignant Mesothelioma H-2452 Cells

Our plain-English summary of Cariporide Enhances the DNA Damage and Apoptosis in Acid-tolerable Malignant Mesothelioma H-2452 Cells, by Y.J. Lee, J.H. Bae, S.A. Kim, et al (Molecules and Cells, 2017).

The study

• Authors: Y.J. Lee, J.H. Bae, S.A. Kim, S.H. Kim, K.M. Woo, H.S. Nam, M.K. Cho, S.H. Lee
• Journal: Molecules and Cells
• Published: 2017;40(8):567-576
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The Na+/H+ exchanger is responsible for maintaining the acidic tumor microenvironment through its promotion of the reabsorption of extracellular Na+ and the extrusion of intracellular H+. The resultant increase in the extracellular acidity contributes to the chemoresistance of malignant tumors. In this study, the chemosensitizing effects of cariporide, a potent Na+/H+-exchange inhibitor, were evaluated in human malignant mesothelioma H-2452 cells preadapted with lactic acid. A higher basal level of phosphorylated (p)-AKT protein was found in the acid-tolerable H-2452AcT cells compared with their parental acid-sensitive H-2452 cells. When introduced in H-2452AcT cells with a concentration that shows only a slight toxicity in H-2452 cells, cariporide exhibited growth-suppressive and apoptosis-promoting activities, as demonstrated by an increase in the cells with pyknotic and fragmented nuclei, annexin V-PE(+) staining, a sub-G0/G1 peak, and a G2/M phase-transition delay in the cell cycle. Preceding these changes, a cariporide-induced p-AKT down-regulation, a p53 up-regulation, an ROS accumulation, and the depolarization of the mitochondrial-membrane potential were observed. A pretreatment with the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 markedly augmented the DNA damage caused by the cariporide, as indicated by a much greater extent of comet tails and a tail moment with increased levels of the p-histone H2A.X, p-ATMSer1981, p-ATRSer428, p-CHK1Ser345, and p-CHK2Thr68, as well as a series of pro-apoptotic events. The data suggest that an inhibition of the PI3K/AKT signaling is necessary to enhance the cytotoxicity toward the acid-tolerable H-2452AcT cells, and it underlines the significance of proton-pump targeting as a potential therapeutic strategy to overcome the acidic-microenvironment-associated chemotherapeutic resistance.

In plain English

This was a laboratory study of human malignant mesothelioma cells grown in culture. It did not study people or asbestos exposure. The authors made an acid-tolerant version of the H-2452 mesothelioma cell line, called H-2452AcT, by repeatedly growing the cells in lactic acid. They compared it with the original cells. The acid-tolerant cells kept a higher level of an activated survival protein, p-AKT. The authors then treated both cell types with cariporide, which blocks the sodium-hydrogen exchanger NHE1, and LY294002, which blocks the enzyme PI3K, alone or together. After 48 hours of the combination, cell viability was 38.7% in the acid-tolerant cells and 57.9% in the original cells. These figures were measured relative to solvent-treated control cells of the same type, set at 100%. With the combination, 67.98% of acid-tolerant cells and 48.37% of original cells stained as apoptotic, meaning dying in a programmed way. The treatments also increased markers of DNA damage, reactive oxygen species, and loss of mitochondrial membrane potential. The authors concluded that their data suggest blocking PI3K/AKT signaling with cariporide and LY294002 is necessary to increase killing of the acid-tolerant cells.

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) cell-culture experiment testing drug effects on a mesothelioma cell line
• Who was studied: The human malignant mesothelioma cell line H-2452, obtained from the American Type Culture Collection, and an acid-tolerant subline (H-2452AcT) derived from it by continued exposure to lactic acid. No human subjects were studied.
• Exposure: No asbestos exposure was studied. The cells were exposed to cariporide, an inhibitor of the NHE1 sodium-hydrogen exchanger, and LY294002, a PI3K inhibitor, alone or in combination. The main combination concentrations were printed as 160 (cariporide) and 5 (LY294002), with the unit symbol damaged in the text.
• Main results:
  • The acid-tolerant H-2452AcT cells had a higher level of phosphorylated AKT (p-AKT) than the original H-2452 cells. It stayed higher even after the cells were switched to medium without lactic acid.
  • Cell viability was measured by MTT assay as a percentage of the vehicle-treated control cells, set at 100%. After 48 hours of the cariporide plus LY294002 combination, it was 38.7% in H-2452AcT cells and 57.9% in H-2452 cells. With cariporide alone it was 76.9% and 91.1%, and with LY294002 alone 64.4% and 70.5%, respectively.
  • With the combination treatment, the proportion of annexin-V-PE positive (apoptotic) cells was 67.98% in H-2452AcT cells compared with 48.37% in H-2452 cells.
  • In the comet assay (a test of DNA damage), the tail-moment value with the combination was 53.08% in H-2452AcT cells compared with 43.22% in H-2452 cells.
  • Levels of phosphorylated DNA-damage-sensing proteins increased in both cell types after treatment. So did phospho-H2A.X, a marker of DNA double-strand breaks.
  • The combination treatment increased the reactive oxygen species (ROS) level to approximately 66.45% in H-2452AcT cells and 47.46% in H-2452 cells.
  • Loss of mitochondrial membrane potential occurred in 26.86% of H-2452AcT cells with cariporide alone and 67.05% with the combination. In H-2452 cells the figures were 9.37% and 37.12%, respectively.
  • Knocking down the p53 protein increased the growth of both cell types.
• The authors' conclusion: The authors concluded that their data suggest inhibition of PI3K/AKT signaling by cariporide and LY294002 is necessary to enhance cytotoxicity toward the acid-tolerant H-2452AcT mesothelioma cells. They also suggested that ROS-dependent mechanisms and p53 may contribute.

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: Apoptosis, Mesothelioma, Tumor Microenvironment.

Related studies

• Pro-oxidant activity of sulforaphane and cisplatin potentiates apoptosis and simultaneously promotes autophagy in malignant mesothelioma cells — Y.J. Lee, S.H. Lee (2017)
• Asbestos-induced pulmonary toxicity: role of DNA damage and apoptosis — D. Upadhyay, D.W. Kamp (2003)
• Knockdown of Bcl-xL enhances growth-inhibiting and apoptosis-inducing effects of resveratrol and clofarabine in malignant mesothelioma H-2452 cells — Y.J. Lee, I.S. Hwang, et al. (2014)
• Synergistic anti-cancer effects of resveratrol and chemotherapeutic agent clofarabine against human malignant mesothelioma MSTO-211H cells — Y.J. Lee, Y.J. Lee, et al. (2013)
• Phagocytosis of crocidolite asbestos induces oxidative stress, DNA damage, and apoptosis in mesothelial cells — W. Liu, J.D. Ernst, et al. (2000)
• Connexin 43 enhances Bax activation via JNK activation in sunitinib-induced apoptosis in mesothelioma cells — M. Uzu, H. Sato, et al. (2017)

Browse return to medical research.