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Molecular Diagnostics

Potentiation of immune checkpoint blockade with a pH-sensitizer as monitored in two pre-clinical tumor models with acidoCEST MRI

British Journal of Cancer volume 132, pages 744–753 (2025)Cite this article

Subjects

Abstract

Background

Tumor acidosis causes resistance to immune checkpoint blockade (ICB). We hypothesized that a “pH-sensitizer” can increase tumor extracellular pH (pHe) and improve tumor control following ICB. We also hypothesized that pHe measured with acidoCEST MRI can predict improved tumor control with ICB.

Methods

We tested the effects of pH-sensitizers on proton efflux rate (PER), cytotoxicity, T cell activation, tumor immunogenicity, tumor growth and survival using 4T1 and B16-F10 tumor cells. We measured in vivo tumor pHe of 4T1 and B16-F10 models with acidoCEST MRI.

Results

Among the pH-sensitizers tested, someprazole caused the greatest reduction in PER without exhibiting cytotoxicity or reducing T cell activation. Esomeprazole improved 4T1 tumor control with ICB administered one day after the pH-sensitizer. Tumor pHe positively correlated with TCF-1 + CD4 effector and CD8 T cell intratumoral frequencies and predicted improved 4T1 tumor control with ICB. For comparison, esomeprazole had a mild effect on B16-F10 tumor pHe, and worsened tumor control with ICB and increased intratumoral myeloid and dendritic cell (DC) frequencies.

Conclusions

A pH-sensitizer can improve tumor control with ICB, and acidoCEST MRI can be used to measure pHe and predict tumor control, but only in the 4T1 model and not the B16-F10 model.

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Fig. 1: Esomeprazole shows the most promise as a pH-sensitizer.
Fig. 2: 4T1 and B16-F10 tumors increase tumor immunogenicity differently when primed with esomeprazole.
Fig. 3: Effects of combination treatment of esomeprazole and ICB injected one day later on tumor growth for 4T1 and B16-F10 tumors.
Fig. 4: Baseline pHe reflects tumor growth rate.
Fig. 5: pHe response to esomeprazole predicts tumor control by esomeprazole treatment followed by ICB.
Fig. 6: AcidoCEST MRI measurements of pHe correlates with intratumoral immune cell frequencies.

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Data availability

All data is available upon reasonable request to the corresponding author. The AcidoCEST code for Matlab 2022b is available on GitHub at https://github.com/CAMEL-MartyPagel/acidoCEST_MRI_Matlab.

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Acknowledgements

The authors thank the MD Anderson Cancer Center Small Animal Imaging Facility and the MD Anderson Cancer Center Advanced Cytometry & Sorting Facility for use of their resources.

Funding

This work was supported by a CPRIT grant (RP220270).

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Author notes

  1. Tianzhe Li

    Present address: Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA

Authors and Affiliations

  1. Department of Cancer Systems Imaging, MD Anderson Cancer Center, Houston, TX, USA

    Renee L. Tran, Tianzhe Li, Jorge de la Cerda, F. William Schuler, Alia S. Khaled, Shivanand Pudakalakatti, Pratip K. Bhattacharya & Mark D. Pagel

  2. Centre for Biosystems Science & Engineering, Indian Institute of Science, Bangalore, India

    Sanhita Sinharay

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Contributions

RLT, SS, and MDP developed the experimental design. RLT and SS performed Seahorse studies. RLT and FWS developed the in vitro cell cultures and tumor models. RLT performed tumor growth and immunogeneicity studies. RLT and JDLC performed acidoCEST MRI studies. RLT, TL, and ASK performed image analyses. RLT, SP, PKB, SS, and MDP interpreted the results. RLC and MDP wrote the manuscript and all co-authors approved the manuscript.

Corresponding author

Correspondence to Mark D. Pagel.

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The authors declare no competing interests.

Ethics approval

All experiments involving mice were conducted according to Protocol 00001998 approved by the Institutional Animal Care and Use Committee at the UT MD Anderson Cancer Center. All mice were housed in a pathogen-free facility fully accredited by the Association for Assessment and Accreditation of Laboratory Animal Care.

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Tran, R.L., Li, T., de la Cerda, J. et al. Potentiation of immune checkpoint blockade with a pH-sensitizer as monitored in two pre-clinical tumor models with acidoCEST MRI. Br J Cancer 132, 744–753 (2025). https://doi.org/10.1038/s41416-025-02962-1

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