Therapeutic Synergy in Esophageal Cancer and Mesothelioma Is Predicted by Dynamic BH3 Profiling

Our plain-English summary of Therapeutic Synergy in Esophageal Cancer and Mesothelioma Is Predicted by Dynamic BH3 Profiling, by D.R. Surman, Y. Xu, M.J. Lee, et al (Molecular Cancer Therapeutics, 2021).

The study

• Authors: D.R. Surman, Y. Xu, M.J. Lee, J. Trepel, K. Brown, M. Ramineni, T.G. Splawn, L.P. Diggs, H.C. Hodges, J.L. Davis, H.S. Lee, B.M. Burt, R.T. Ripley
• Journal: Molecular Cancer Therapeutics
• Published: 2021;20(8):1469-1480
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Approximately 20,000 patients per year are diagnosed with esophageal adenocarcinoma (EAC) and malignant pleural mesothelioma (MPM); fewer than 20% survive 5 years. Effective therapeutic strategies are limited although patients receive a combination of chemotherapeutics. These tumors harbor thousands of mutations that contribute to tumor development. Downstream of oncogenic driving mutations, altered tumor mitochondria promote resistance to apoptosis. Dynamic Bcl-2 homology-3 profiling (DBP) is a functional assay of live cells that identifies the mitochondrial proteins responsible for resistance to apoptosis. We hypothesized that DBP will predict which protein to target to overcome resistance thereby enhancing combinatorial therapy.DBP predicted that targeting either Mcl-1 or Bcl-xL increases the efficacy of the chemotherapeutic agent, cisplatin, whereas targeting Bcl-2 does not. We performed these assays by treating EAC and MPM cells with a combination of Bcl-2 homology-3 (BH3) mimetics and cisplatin. Following treatments, we performed efficacy assessments including apoptosis assays, IC50 calculations, and generation of a combinatorial index. DBP confirmed that targeting mitochondria with BH3 mimetics alters the threshold of apoptosis. These apoptotic effects were abolished when the mitochondrial pathway was disrupted. We validated our findings by developing knockdown models of antiapoptotic proteins Mcl-1, Bcl-xL, and the mitochondrial effector proteins Bax/Bak. Knockdown of Mcl-1 or Bcl-xL recapitulated the results of BH3 mimetics. In addition, we report an approach for BH3 profiling directly from patient tumor samples. We demonstrate that the DBP assay on living tumor cells measures the dynamic changes of resistance mechanisms, assesses response to combinatorial therapy, and provides results in a clinically feasible time frame.

©2021 The Authors; Published by the American Association for Cancer Research.

In plain English

This was a laboratory study of cancer cells. It did not study asbestos exposure; asbestos is mentioned only as background in the introduction. The authors tested whether a live-cell test called dynamic BH3 profiling could predict which added drug would make the chemotherapy drug cisplatin work better against esophageal adenocarcinoma and malignant pleural mesothelioma. They used laboratory-grown cancer cell lines, tissue slides from 40 esophageal tumors and 100 mesothelioma tumors, and fresh tumor samples from patients. In the cell lines, drugs that block the proteins Mcl-1 or Bcl-xL changed the test result and increased cancer-cell death when combined with cisplatin. A drug that blocks Bcl-2 did neither. In esophageal cancer cells with Bax and Bak reduced by knockdown, the treatment-induced cell death was lost. Test results from patients' tumors differed from patient to patient. Irradiated esophageal tumor samples could get a basic BH3 profile but did not survive 48 hours of laboratory culture, so the dynamic test could not be done on them. The authors concluded that the test can predict which protein to target to overcome treatment resistance.

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 using cancer cell lines, tissue microarrays and fresh patient tumor samples tested outside the body; described by the authors as a proof-of-concept model
• Who was studied: Esophageal adenocarcinoma cell lines (FLO-1, Eso26, OE33) and mesothelioma cell lines (H28, H226, H2052, H2452). Tissue microarrays of 10 normal esophageal mucosa samples, 40 esophageal adenocarcinoma tumors, eight normal pleural samples and 100 malignant pleural mesothelioma tumors. Fresh tumor samples from patients: BH3 profiles in seven mesothelioma and three esophageal adenocarcinoma patients, and dynamic profiling in four mesothelioma tumors plus one esophageal adenocarcinoma that had spread to the pleura.
• Exposure: Not asbestos. Cells were treated with drugs that block anti-cell-death proteins: ABT-199 (blocks Bcl-2), A1155463 (blocks Bcl-xL), S63845 and AZD-5991 (block Mcl-1). These were given alone and combined with cisplatin (CDDP). Asbestos appears only in the introduction, as background on the causes of mesothelioma.
• Main results:
  • In tissue microarrays, more than 90% of tumor specimens showed more than 50% Mcl-1 expression, in both esophageal adenocarcinoma and mesothelioma.
  • In esophageal adenocarcinoma cell lines, dynamic BH3 profiling showed that blocking Mcl-1 or Bcl-xL, but not Bcl-2, primed the mitochondria (the cell structures that trigger cell death).
  • In esophageal adenocarcinoma cells, adding the Bcl-2 blocker ABT-199 to cisplatin gave no more cell death than cisplatin alone. The Mcl-1 or Bcl-xL blockers combined with cisplatin significantly increased cell death compared with cisplatin alone.
  • A combination-index analysis showed synergy between the Mcl-1 blocker S63845 and cisplatin at most doses in two cell lines. Only one of eight doses showed synergy between ABT-199 and cisplatin.
  • In the mesothelioma cell lines H28 and H2452, the results resembled those in esophageal cells: the cisplatin IC50 (the dose needed to reduce cell growth by half) fell and cell death rose with the Mcl-1 or Bcl-xL blockers, but not with ABT-199.
  • In esophageal cells in which Bax and Bak had been knocked down (their levels reduced), treatment with S63845 and cisplatin, alone or combined, produced a complete loss of apoptosis compared with controls.
  • Genetically reducing Mcl-1 or Bcl-xL had effects similar to drug treatment.
  • In fresh mesothelioma tumor samples, dynamic BH3 profiling could be performed, and the patterns differed between patients. In one patient (patient K), combining the Bcl-xL blocker or the Mcl-1 blocker AZD-5991 with cisplatin significantly increased cell death compared with ABT-199 or the control.
  • Basic BH3 profiles were obtained from three esophageal adenocarcinoma patients and showed varying patterns.
  • The irradiated esophageal adenocarcinoma specimens did not survive 48 hours of culture outside the body, so dynamic profiling could not be done on them. Dynamic profiling was done on one non-irradiated esophageal tumor that had spread to the pleura.
• The authors' conclusion: The authors concluded that dynamic BH3 profiling can predict which anti-cell-death protein to target to overcome treatment resistance. They also concluded that it can produce results in a clinically feasible time frame.
• Limitations the authors state:
  • The testing was done on a small number of patients: BH3 profiles in 10 patients and dynamic profiling in four patients. The authors acknowledged that several limitations exist.
  • A high-throughput version of the test performed directly on patient samples has not yet been developed.
  • The test could not be done on tumor cells after radiation, so samples taken before treatment would be needed.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma, Throat and laryngeal cancer.

Medical terms in this study, explained in our Lexicon: Esophageal Cancer, Mesothelioma, Adenocarcinoma, Pleural Mesothelioma, Apoptosis, Cisplatin.

Related studies

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• Vorinostat eliminates multicellular resistance of mesothelioma 3D spheroids via restoration of Noxa expression — D. Barbone, P. Cheung, et al. (2012)
• The Wnt regulator SFRP4 inhibits mesothelioma cell proliferation, migration, and antagonizes Wnt3a via its netrin-like domain — V. Perumal, A.M. Dharmarajan, et al. (2017)
• SORORIN and PLK1 as potential therapeutic targets in malignant pleural mesothelioma — T. Kato, D. Lee, et al. (2016)
• Gene expression profiling of homologous recombination repair pathway indicates susceptibility for olaparib treatment in malignant pleural mesothelioma in vitro — S. Borchert, M. Wessolly, et al. (2019)
• An RNAi-based screen reveals PLK1, CDK1 and NDC80 as potential therapeutic targets in malignant pleural mesothelioma — A. Linton, Y.Y. Cheng, et al. (2014)

Browse more research in Molecular Cancer Therapeutics, or return to medical research.