Potential of fluoropyrimidine to be an immunologically optimal partner of immune checkpoint inhibitors through inducing immunogenic cell death for thoracic malignancies

Our plain-English summary of Potential of fluoropyrimidine to be an immunologically optimal partner of immune checkpoint inhibitors through inducing immunogenic cell death for thoracic malignancies, by H. Kozai, H. Ogino, A. Mitsuhashi, et al (Thoracic Cancer, 2024).

The study

• Authors: H. Kozai, H. Ogino, A. Mitsuhashi, N.T. Nguyen, Y. Tsukazaki, Y. Yabuki, R. Ozaki, H. Yoneda, S. Sato, M. Hanibuchi, T. Shinohara, H. Nokihara, Y. Nishioka
• Journal: Thoracic Cancer
• Published: 2024;15(5):369-378
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Immune checkpoint inhibitors (ICIs) are a revolutionary paradigm in the treatment of thoracic malignancies and chemoimmunotherapy is a current standard care in this field. Chemotherapeutic agents are known to induce not only direct cytotoxic effects on tumor cells but also immune modulating effects, such as stimulating immunogenic cell death (ICD). Currently, either pemetrexed (PEM) or taxane plus platinum are combined with ICIs for patients with non-small cell lung cancer (NSCLC); however, it is still unknown whether these agents are immunologically optimal partners for ICIs.

Methods: To determine the immunologically optimal chemotherapeutic agent, we first evaluated the ability of several chemotherapeutic agents, including platinum, PEM, taxane, and 5-fluorouracil (5-FU) to induce ICD using several thoracic tumor cell lines in vitro. ICD was evaluated by the cell surface expression of calreticulin (CRT) and adenosine-triphosphate (ATP) secretion. We further performed an antitumor vaccination assay in vivo.

Results: 5-FU induced cell surface expression of CRT and ATP secretion most efficiently among the several chemotherapeutic agents. This effect was enhanced when it was combined with platinum. In the antitumor vaccination assay in vivo, we found that vaccination with dying-AB1-HA (a murine malignant mesothelioma cell line) cells treated with 5-FU, but neither PEM nor PTX, reduced the tumor growth of living-AB1-HA cells inoculated 1 week after vaccination by recruiting CD3+ CD8+ T cells into the tumor microenvironment.

Conclusion: Our findings indicate that fluoropyrimidine can be an immunologically optimal partner of ICIs through the induction of ICD for thoracic malignancies.

© 2023 The Authors. Thoracic Cancer published by John Wiley & Sons Australia, Ltd.

In plain English

This laboratory study tested whether chemotherapy drugs make tumor cells die in a way that alerts the immune system, which the authors call immunogenic cell death. It did not study asbestos exposure or human patients. The authors treated four human non-small cell lung cancer cell lines with drugs including 5-fluorouracil (5-FU), pemetrexed, taxanes and platinum drugs. They treated one mouse malignant mesothelioma cell line (AB1-HA) with 5-FU, pemetrexed or paclitaxel. They measured surface calreticulin and ATP release. 5-FU raised surface calreticulin in all four lung cancer lines and raised ATP release in both lines tested. Pemetrexed and taxanes showed weaker or inconsistent effects. Low-dose 5-FU combined with platinum raised calreticulin when low-dose 5-FU or platinum alone did not. In mice (7 per group), vaccination with dying mesothelioma cells treated with 5-FU, but not pemetrexed or paclitaxel, reduced the growth of tumors injected a week later. Tumors in 5-FU-vaccinated mice had significantly more CD3+CD8+ T cells. The authors concluded that fluoropyrimidine may be a better immune checkpoint inhibitor partner than pemetrexed or taxane, and they called for a clinical trial. They noted that only a few cell lines were used.

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) experiments on tumor cell lines plus an animal experiment (antitumor vaccination assay in mice)
• Who was studied: Human lung cancer cell lines A549 and PC9 (adenocarcinoma) and H226 and H2170 (squamous cell carcinoma); the murine malignant mesothelioma cell line AB1-HA; six-week-old male BALB/c mice, 7 per group, with the animal experiments repeated twice; Tokushima University, Japan
• Exposure: Chemotherapy drugs: pemetrexed (PEM), 5-fluorouracil (5-FU), vinorelbine, paclitaxel (PTX), docetaxel, gemcitabine, cisplatin and carboplatin were used on human lung cancer cells, at concentrations scaled to each drug's median inhibitory concentration (IC50). The mouse mesothelioma cells (AB1-HA) were treated with 5-FU, PEM or PTX. No asbestos or fiber exposure was studied.
• Main results:
  • In the lung adenocarcinoma cell lines, 5-FU induced cell-surface calreticulin in both A549 and PC9 cells, even after 48 hours. PEM induced it in A549 but not PC9 cells, and only at 24 hours. Taxanes and other agents had little effect.
  • In both lung squamous cell carcinoma cell lines tested, 5-FU induced cell-surface calreticulin more efficiently than taxane.
  • 5-FU increased ATP secretion from PC9 and H226 cells in a dose-dependent way. In PC9 cells it was more efficient than PEM.
  • 5-FU did not increase MHC class I expression on PC9 or H226 cells.
  • In human lung cancer cells, low-dose 5-FU or low-dose platinum alone did not induce surface calreticulin, but low-dose 5-FU combined with platinum did.
  • In AB1-HA mouse mesothelioma cells, a high dose of 5-FU induced surface calreticulin. Neither PEM nor PTX did.
  • Mice (7 per group) vaccinated with dying AB1-HA cells treated with 5-FU, but not with PEM or PTX, had reduced growth of living AB1-HA tumors injected 1 week later. Dying cells induced by freeze-thawing gave tumor growth comparable to saline.
  • CD3+CD8+ T cells were significantly increased (p less than 0.05) in rechallenged tumors from mice vaccinated with 5-FU-treated cells. This was counted in 9 fields from 3 mice per group.
• The authors' conclusion: The authors concluded that fluoropyrimidine may produce synergistic antitumor immune responses and be a better agent than PEM or taxane to combine with immune checkpoint inhibitors for thoracic cancer. They said a clinical trial should be organized to test this.
• Limitations the authors state:
  • The study looked mainly at immunogenic cell death, not at other immune regulators such as PD-L1 on tumor cells or IFN-gamma from immune cells.
  • Immunogenic cell death was defined mainly by surface calreticulin and partly by ATP secretion. HMGB1 release was below the limit of detection.
  • Only a limited number of cell lines were used, so the results may not generalize to NSCLC and malignant pleural mesothelioma. The mouse experiments used an HA antigen-transduced mesothelioma line.
  • AB1-HA cells were treated at 10 times the IC50 to make the vaccine, a higher dose than used in the human cell experiments, because 1 times the IC50 did not induce surface calreticulin on AB1-HA cells.
  • The combined effect of 5-FU and platinum was not tested in mice.

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: checkpoint inhibitors, Pemetrexed (Alimta), Non-Small Cell Lung Cancer, Fluorouracil (5-FU), Mesothelioma, Tumor Microenvironment.

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• Ecteinascidin synthetic analogues: a new class of selective inhibitors of transcription, exerting immunogenic cell death in refractory malignant pleural mesothelioma — I.C. Salaroglio, P. Aviles, et al. (2024)
• Leveraging Immunogenic Cell Death to Enhance the Immune Response against Malignant Pleural Mesothelioma Tumors — M.R. Chang, E.M. Matnurov, et al. (2025)
• Immunogenic cell death and immunogenic surrender: related but distinct mechanisms of immune surveillance — R. Mezzapelle, M.E. Bianchi, et al. (2021)
• Pre-treatment soluble PD-L1 as a predictor of overall survival for immune checkpoint inhibitor therapy: a systematic review and meta-analysis — Á. Széles, T. Fazekas, et al. (2023)
• The clinical utility of comprehensive measurement of autoimmune disease-related antibodies in patients with advanced solid tumors receiving immune checkpoint inhibitors: a retrospective study — N. Izawa, H. Shiokawa, et al. (2022)

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