No abstract

Hypoxia is a well-known component of many tumors and acts in an immunosuppressive manner through multiple distinct pathways. 18 F-FMISO PET imaging has been demonstrated to accurately quantify hypoxia in a clinical setting, although it has not been investigated for immunotherapy. Our work demonstrates that effective immunotherapy prevents tumor hypoxia and that uptake of 18 F-FMISO was predictive of subsequent changes in anatomical tumor size. We further demonstrate that PET imaging of hypoxia is correlated with phenotypic characteristics of inflammation through transcriptomics, immune cell spatial correlation, and direct measurement of secreted inflammatory proteins. The upregulation of damage associated molecular pattern signaling in responding tumors warranted investigation of the addition of the hypoxia targeted pro-drug to non-responding tumors in order to enhance checkpoint blockade efficacy. The addition of evofosfamide improved tumor oxygenation and response, providing rationale for immediate clinical investigation of both 18 F-FMISO PET imaging and combination evofosfamide therapy for improved cancer immunotherapy.Research.

Supplementary Data from ¹⁸F-FMISO PET Imaging Identifies Hypoxia and Immunosuppressive Tumor Microenvironments and Guides Targeted Evofosfamide Therapy in Tumors Refractory to PD-1 and CTLA-4 Inhibition

<div>AbstractPurpose:<p>Hypoxia is a common characteristic of many tumor microenvironments, and it has been shown to promote suppression of antitumor immunity. Despite strong biological rationale, longitudinal correlation of hypoxia and response to immunotherapy has not been investigated.</p>Experimental Design:<p>In this study, we probed the tumor and its surrounding microenvironment with ¹⁸F-FMISO PET imaging to noninvasively quantify tumor hypoxia <i>in vivo</i> prior to and during PD-1 and CTLA-4 checkpoint blockade in preclinical models of breast and colon cancer.</p>Results:<p>Longitudinal imaging identified hypoxia as an early predictive biomarker of therapeutic response (prior to anatomic changes in tumor volume) with a decreasing standard uptake value (SUV) ratio in tumors that effectively respond to therapy. PET signal correlated with <i>ex vivo</i> markers of tumor immune response including cytokines (IFNγ, GZMB, and TNF), damage-associated molecular pattern receptors (TLR2/4), and immune cell populations (macrophages, dendritic cells, and cytotoxic T cells). Responding tumors were marked by increased inflammation that were spatially distinct from hypoxic regions, providing a mechanistic understanding of the immune signaling pathways activated. To exploit image-guided combination therapy, hypoxia signal from PET imaging was used to guide the addition of a hypoxia targeted treatment to nonresponsive tumors, which ultimately provided therapeutic synergy and rescued response as determined by longitudinal changes in tumor volume.</p>Conclusions:<p>The results generated from this work provide an immediately translatable paradigm for measuring and targeting hypoxia to increase response to immune checkpoint therapy and using hypoxia imaging to guide combinatory therapies.</p></div>

Supplementary Data from ¹⁸F-FMISO PET Imaging Identifies Hypoxia and Immunosuppressive Tumor Microenvironments and Guides Targeted Evofosfamide Therapy in Tumors Refractory to PD-1 and CTLA-4 Inhibition