Activation of Nrf2 pathways correlates with resistance of NSCLC cell lines to CBP501 in vitro

Our plain-English summary of Activation of Nrf2 pathways correlates with resistance of NSCLC cell lines to CBP501 in vitro, by N. Mine, S. Yamamoto, D.W. Kufe, et al (Molecular Cancer Therapeutics, 2014).

The study

• Authors: N. Mine, S. Yamamoto, D.W. Kufe, D.D. Von Hoff, T. Kawabe
• Journal: Molecular Cancer Therapeutics
• Published: 2014;13(9):2215-25
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

CBP501 is an anticancer drug candidate that was investigated in two randomized phase II clinical trials for patients with nonsquamous non-small cell lung cancer (NSCLC) and malignant pleural mesothelioma (MPM). CBP501 has been shown to have two mechanisms of action, namely calmodulin modulation and G2 checkpoint abrogation. Here, we searched for a biomarker to predict sensitivity to CBP501. Twenty-eight NSCLC cell lines were classified into two subgroups, CBP501-sensitive and -insensitive, by quantitatively analyzing the cis-diamminedichloro-platinum (II) (CDDP)-enhancing activity of CBP501 through treatments with short-term (1 hour) coexposure to CDDP and CBP501 or to either alone. Microarray analysis was performed on these cell lines to identify gene expression patterns that correlated with CBP501 sensitivity. We found that multiple nuclear factor erythroid-2-related factor 2 (Nrf2) target genes showed high expression in CBP501-insensitive cell lines. Western blot and immunocytochemical analysis for Nrf2 in NSCLC cell lines also indicated higher protein level in CBP501-insensitive cell lines. Moreover, CBP501 sensitivity is modulated by silencing or sulforaphane-induced overexpression of Nrf2. These results indicate that Nrf2 transcription factor is a potential candidate as a biomarker for resistance to CBP501. This study might help to identify those subpopulations of patients who would respond well to the CBP501 and CDDP combination treatment of NSCLC.

©2014 American Association for Cancer Research.

In plain English

This was a laboratory study of human non-small cell lung cancer (NSCLC) cell lines, not of people, and it did not study asbestos. CBP501 is an experimental drug given with the chemotherapy drug CDDP (cisplatin). The authors note it had been tested in trials that included malignant pleural mesothelioma, but this study used only lung cancer cells. The authors exposed 28 cell lines to CDDP with or without CBP501 for 1 hour. They classed a line as sensitive if CBP501 boosted CDDP's effect 2-fold or more: 16 lines were sensitive and 12 insensitive. Insensitive lines had higher levels of a protein called Nrf2 and of several genes Nrf2 controls. Across the 28 lines, three such genes had prediction rates of 85.7% (GSR), 85.7% (G6PD) and 75% (AKR1C3). Reducing Nrf2 levels with a gene knockdown made one insensitive line, H1437, respond to CBP501. Raising Nrf2 with sulforaphane weakened CBP501's effect in a sensitive line. The authors concluded that Nrf2 and its target molecules could be reliable markers for predicting resistance to CBP501, at least in vitro, and called for further testing in tumor biopsy samples.

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 cancer cell lines: drug-response testing, gene-expression microarray, Western blot, immunocytochemistry and gene knockdown experiments
• Who was studied: 28 human non-small cell lung cancer (NSCLC) cell lines bought from ATCC: an initial set of 12, then 16 additional lines. No patients were studied.
• Exposure: Laboratory drug exposure, not asbestos: 1-hour treatment with CDDP (cisplatin) with or without the experimental drug CBP501. Some experiments also used sulforaphane, a known Nrf2 activator.
• Main results:
  • In the NCI-H1703 cell line, CBP501 increased the effectiveness of CDDP about 8-fold. The NCI-H1437 line showed no detectable shift.
  • Lines were classed as sensitive if CBP501 shifted the CDDP response 2-fold or more. Tables 1 and 2 list 16 of the 28 lines as sensitive and 12 as insensitive.
  • In the first 12 cell lines, 40 genes showed more than 70% correlation with CBP501 sensitivity.
  • In the first 12 cell lines, the level of Nrf2 protein, but not Nrf2 mRNA, correlated with CBP501 sensitivity.
  • In the sensitive line H1703, sulforaphane weakened CBP501's effect in cells given a control shRNA. This effect of sulforaphane was abolished in cells where Nrf2 had been knocked down.
  • In the insensitive line H1437, knocking down Nrf2 reduced levels of AKR1C3, G6PD and GSR and allowed CBP501 to increase the effects of CDDP.
  • Across all 28 cell lines, seven genes predicted sensitivity with more than 70% accuracy. They included three Nrf2 target genes: GSR (85.7%), AKR1C3 (75%) and G6PD (85.7%).
  • Immunocytochemistry detected higher AKR1C3 levels in insensitive cell lines than in sensitive ones.
  • Keap1 mutations tended to occur in the CBP501-insensitive cell lines.
• The authors' conclusion: The authors concluded that immunohistochemical detection of Nrf2 and a series of its target molecules can be reliable markers for predicting resistance to CBP501, at least in vitro.
• Limitations the authors state:
  • It is not known which Nrf2 target gene or process directly affects sensitivity to CBP501.
  • Platinum accumulation in the NSCLC cell lines was not demonstrated.
  • Microarray analysis has technical limits that may hide direct effects.
  • The general reliability of these predictive markers remains to be established.
  • Detection of these proteins in tumor biopsy samples, and their correlation with CBP501 sensitivity, still need further validation.
  • The role of each Keap1 mutation type needs further verification.

Topics

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

Medical terms in this study, explained in our Lexicon: Clinical Trial, Non-Small Cell Lung Cancer, Pleural Mesothelioma, Biomarker.

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