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Cancer immunotherapy is accompanied by distinct metabolic patterns in primary and secondary lymphoid organs observed by non-invasive in vivo 18F-FDG-PET
Purpose: Cancer immunotherapy depends on a systemic immune response, but the basic underlying mechanisms are still largely unknown. Despite the very successful and widespread use of checkpoint inhibitors in the clinic, the majority of cancer patients do not benefit from this type of treatment. In th...
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Published in: | Theranostics 2020-01, Vol.10 (2), p.925-937 |
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Main Authors: | , , , , , , , , , , , , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | Purpose: Cancer immunotherapy depends on a systemic immune response, but the basic underlying mechanisms are still largely unknown. Despite the very successful and widespread use of checkpoint inhibitors in the clinic, the majority of cancer patients do not benefit from this type of treatment. In this translational study, we investigated whether noninvasive in vivo positron emission tomography (PET) imaging using 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) is capable of detecting immunotherapy-associated metabolic changes in the primary and secondary lymphoid organs and whether this detection enables the prediction of a successful anti-cancer immune response. Methods: RIP1-Tag2 mice with progressed endogenous insular cell carcinomas underwent a combined cancer immunotherapy consisting of CD4+ T cells plus monoclonal antibodies (mAbs) against programmed death ligand-1 (PD-L1) and lymphocyte activation gene-3 (LAG-3) or a sham treatment after radiation-mediated immune cell depletion. A second cohort of RIP1-Tag2 mice underwent exclusive checkpoint inhibitor therapy (CIT) using anti-PD-L1/LAG-3 mAbs or sham treatment without initial immune cell depletion to mimic the clinical situation. All mice were monitored by 18F-FDG-PET combined with anatomical magnetic resonance imaging (MRI). In addition, we retrospectively analyzed PET / computed tomography (CT) scans (PET/CT) regarding 18F-FDG uptake of CIT-treated metastatic melanoma patients in the spleen (n=23) and bone marrow (BM; n=20) as well as blood parameters (n=17-21). Results: RIP1-Tag2 mice with advanced insular cell carcinomas treated with combination immunotherapy exhibited significantly increased 18F-FDG uptake in the spleen compared to sham-treated mice. Histopathology of the spleens from treated mice revealed atrophy of the white pulp with fewer germinal centers and an expanded red pulp with hyperplasia of neutrophils than those of sham-treated mice. Immunohistochemistry and flow cytometry analyses of the spleens revealed a lower number of T cells and a higher number of neutrophils compared to those in the spleens of sham-treated mice. Flow cytometry of the BM showed enhanced activation of T cells following the treatment schemes that included checkpoint inhibitors. The ratio of 18F-FDG uptake at baseline to the uptake at follow-up in the spleens of exclusively CIT-treated RIP1-Tag2 mice was significantly enhanced, but the ratio was not enhanced in the spleens of the sham-treated littermates. Flow cytom |
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ISSN: | 1838-7640 |
DOI: | 10.7150/thno.35989 |