AMPK activation induced in pemetrexed-treated cells is associated with development of drug resistance independently of target enzyme expression

Our plain-English summary of AMPK activation induced in pemetrexed-treated cells is associated with development of drug resistance independently of target enzyme expression, by Y. Qin, I. Sekine, M. Hanazono, et al (Molecular Oncology, 2019).

The study

• Authors: Y. Qin, I. Sekine, M. Hanazono, T. Morinaga, M. Fan, Y. Takiguchi, Y. Tada, M. Shingyoji, N. Yamaguchi, M. Tagawa
• Journal: Molecular Oncology
• Published: 2019;13(6):1419-1432
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Pemetrexed (PEM) inhibits DNA and RNA synthesis and is currently one of the first-line agents for mesothelioma. PEM suppresses the activities of several enzymes involved in purine and pyrimidine synthesis, and elevated activity of these enzymes in tumors is often linked with resistance to PEM. The agent also stimulates AMP-activated protein kinase (AMPK) and consequently influences the mammalian target of rapamycin complex 1 (mTORC1) pathways. Nevertheless, it remains unclear whether PEM resistance is linked to the AMPK or mTORC1 pathways. Here, we established two independent PEM-resistant mesothelioma cell lines in which expression of the PEM-target enzymes was not elevated, and found that levels of phosphorylated AMPK and p70S6K and, to a lesser extent, levels of phosphorylated AKT and p53, were increased in these cells as compared with the respective parent cells. PEM stimulation also augmented phosphorylation of AMPK, p70S6K, AKT and p53 in most cases. An AMPK activator increased phosphorylation and PEM resistance in parental cells, and the inhibitor decreased the resistance of PEM-resistant cells. In contrast, inhibitors for p70S6K and AKT did not influence PEM resistance; furthermore, increased levels of endogenous p53 did not affect PEM sensitivity. These data collectively indicate that constitutive activation of AMPK is associated with PEM resistance, and that this is unconnected with elevated DNA and RNA synthesis.

© 2019 The Authors. Published by FEBS Press and John Wiley & Sons Ltd.

In plain English

This was a laboratory study of human mesothelioma cells grown in culture. No patients were studied and asbestos exposure was not examined. The authors used mesothelioma cell lines that had earlier been made resistant to pemetrexed, a first-line chemotherapy drug for mesothelioma, by raising the drug dose step by step. They focused on two resistant lines, H28-PEM and H226-PEM, in which the drug's main target enzymes were not raised. Compared with their parent cells, these resistant cells had higher levels of activated (phosphorylated) AMPK, a cell energy sensor, and of phosphorylated p70S6K. A chemical that activates AMPK made the parent cells more resistant to pemetrexed. An AMPK inhibitor, compound C, made the resistant cells more sensitive to it. Inhibitors of p70S6K and AKT, and raising p53 levels with nutlin-3a, were reported not to influence pemetrexed sensitivity, apart from isolated exceptions; rapamycin increased resistance in H226-PEM cells. The authors concluded that pemetrexed resistance was linked to raised AMPK activity, and they suggested a possible use of an AMPK inhibitor in patients who became resistant. They noted that resistance was not solely attributable to AMPK and that the mechanism remained uncharacterized.

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 and drug-resistant derivatives, using cell viability assays and Western blot analysis
• Who was studied: Human mesothelioma cell lines NCI-H28, NCI-H226, MSTO-211H and NCI-H2452 and their pemetrexed-resistant derivatives, with a focus on H28-PEM and H226-PEM. Also used were cisplatin-resistant lines, mesothelioma cells with mutated p53 (EHMES-1, JMN-1B) and immortalized mesothelium-derived Met-5A cells. No human subjects were studied.
• Exposure: The chemotherapy drug pemetrexed, alone and combined with an AMPK activator (A769662), an AMPK inhibitor (compound C), p70S6K inhibitors (rapamycin, PF4708671), an AKT inhibitor (MK-2206) and the p53-raising agent nutlin-3a. Asbestos exposure was not studied.
• Main results:
  • The pemetrexed-resistant cell lines were less sensitive to pemetrexed than their parent cells in the viability test.
  • Phosphorylated AMPK was higher in H28-PEM and H226-PEM cells than in their parent cells. It was also higher in H2452-PEM cells, but lower in 211H-PEM cells.
  • H28-PEM and H226-PEM cells had higher phosphorylated p70S6K levels than their parent cells.
  • In cisplatin-resistant cells, AMPK and phosphorylated AMPK did not differ from parent cells, except in cisplatin-resistant NCI-H2452 cells, where phosphorylated AMPK decreased.
  • In parent NCI-H28 and NCI-H226 cells, the AMPK activator A769662 increased resistance to pemetrexed.
  • In H28-PEM and H226-PEM cells, the AMPK inhibitor compound C increased pemetrexed sensitivity.
  • In the resistant cells, rapamycin did not affect pemetrexed sensitivity of H28-PEM cells and increased resistance in H226-PEM cells. The authors concluded that p70S6K activation was unrelated to pemetrexed resistance.
  • The AKT inhibitor MK-2206 did not influence pemetrexed sensitivity in H28-PEM cells, or in H226-PEM cells except at one concentration.
  • Raising p53 with nutlin-3a did not affect pemetrexed resistance, except in NCI-H28 cells at one concentration.
  • Pemetrexed increased AMPK phosphorylation in cells with mutated or non-functional p53, which the authors took to show that AMPK activation was not linked to p53 genotype or DNA damage.
• The authors' conclusion: The authors concluded that pemetrexed resistance was linked to raised AMPK activity with an uninhibited mTORC1 pathway, and could be attributable to constant activation of AMPK. They suggested a possible use of an AMPK inhibitor in patients who became pemetrexed-resistant.
• Limitations the authors state:
  • The authors stated that pemetrexed resistance was not solely attributable to constant AMPK activation.
  • The authors stated that the mechanism by which raised AMPK leads to pemetrexed resistance remained uncharacterized.
  • The authors stated that a role for molecules other than AMPK could not be ruled out.
  • The authors noted that the molecular responses seen in pemetrexed-treated cells were not direct evidence of a link with resistance.

Topics

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

Medical terms in this study, explained in our Lexicon: Pemetrexed (Alimta), Mesothelioma.

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