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Low-dose targeted radionuclide therapy renders immunologically cold tumors responsive to immune checkpoint blockade.

ABSTRACT: Molecular and cellular effects of radiotherapy on tumor microenvironment (TME) can help prime and propagate antitumor immunity. We hypothesized that delivering radiation to all tumor sites could augment response to immunotherapies. We tested an approach to enhance response to immune checkpoint inhibitors (ICIs) by using targeted radionuclide therapy (TRT) to deliver radiation semiselectively to tumors. NM600, an alkylphosphocholine analog that preferentially accumulates in most tumor types, chelates a radioisotope and semiselectively delivers it to the TME for therapeutic or diagnostic applications. Using serial ⁸⁶Y-NM600 positron emission tomography (PET) imaging, we estimated the dosimetry of ⁹⁰Y-NM600 in immunologically cold syngeneic murine models that do not respond to ICIs alone. We observed strong therapeutic efficacy and reported optimal dose (2.5 to 5 gray) and sequence for ⁹⁰Y-NM600 in combination with ICIs. After combined treatment, 45 to 66% of mice exhibited complete response and tumor-specific T cell memory, compared to 0% with ⁹⁰Y-NM600 or ICI alone. This required expression of STING in tumor cells. Combined TRT and ICI activated production of proinflammatory cytokines in the TME, promoted tumor infiltration by and clonal expansion of CD8⁺ T cells, and reduced metastases. In mice bearing multiple tumors, combining TRT with moderate-dose (12 gray) external beam radiotherapy (EBRT) targeting a single tumor augmented response to ICIs compared to combination of ICIs with either TRT or EBRT alone. The safety of TRT was confirmed in a companion canine study. Low-dose TRT represents a translatable approach to promote response to ICIs for many tumor types, regardless of location.

SUBMITTER: Patel RB

PROVIDER: S-EPMC8449934 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Immunotherapeutics represent highly promising agents with the potential to improve patient outcomes in a variety of cancer types. Unfortunately, single-agent immunotherapy has achieved limited clinical benefit to date in patients suffering from pancreatic ductal adenocarcinoma (PDAC). This may be due to the presence of a uniquely immunosuppressive tumor microenvironment (TME) present in PDACs, which creates a barrier to effective immune surveillance. Critical obstacles to immunotherapy in PDAC tumors include the dense desmoplastic stroma that acts as a barrier to T-cell infiltration and the high numbers of tumor-associated immunosuppressive cells. We have identified hyperactivated focal adhesion kinase (FAK) activity in neoplastic PDAC cells as a significant regulator of the fibrotic and immunosuppressive TME. We found that FAK activity was elevated in human PDAC tissues and correlates with high levels of fibrosis and poor CD8+ cytotoxic T-cell infiltration. Single-agent FAK inhibition (VS-4718) dramatically limited tumor progression, resulting in a doubling of survival in the p48-Cre/LSL-KrasG12D/p53Flox/+ (KPC) mouse model of human PDAC. This alteration in tumor progression was associated with dramatically reduced tumor fibrosis, decreased numbers of tumor-infiltrating immature myeloid cells and immunosuppressive macrophages. We postulated that these desirable effects of FAK inhibition on the TME might render PDAC tumors more sensitive to immunotherapy. Accordingly, we found that VS-4718 rendered the previously unresponsive KPC mouse model responsive to anti-PD1 and anti-CTLA4 antagonists leading to a nearly tripling of survival times. These data suggest that FAK inhibition increases immune surveillance by overcoming the fibrotic and immunosuppressive PDAC TME thus rendering tumors more responsive to immunotherapy. We treated KP orthotopic tumor-bearing mice with vehicle and FAK inhibitor (FAKi) for 14 days, then extracted total RNA from tumor tissues.

Project description:BACKGROUND:Unlike some adult cancers, most pediatric cancers are considered immunologically cold and generally less responsive to immunotherapy. While immunotherapy has already been incorporated into standard of care treatment for pediatric patients with high-risk neuroblastoma, overall survival remains poor. In a mouse melanoma model, we found that radiation and tumor-specific immunocytokine generate an in situ vaccination response in syngeneic mice bearing large tumors. Here, we tested whether a novel immunotherapeutic approach utilizing radiation and immunocytokine together with innate immune stimulation could generate a potent antitumor response with immunologic memory against syngeneic murine neuroblastoma. METHODS:Mice bearing disialoganglioside (GD2)-expressing neuroblastoma tumors (either NXS2 or 9464D-GD2) were treated with radiation and immunotherapy (including anti-GD2 immunocytokine with or without anti-CTLA-4, CpG and anti-CD40 monoclonal antibody). Tumor growth, animal survival and immune cell infiltrate were analyzed in the tumor microenvironment in response to various treatment regimens. RESULTS:NXS2 had a moderate tumor mutation burden (TMB) while N-MYC driven 9464D-GD2 had a low TMB, therefore the latter served as a better model for high-risk neuroblastoma (an immunologically cold tumor). Radiation and immunocytokine induced a potent in situ vaccination response against NXS2 tumors, but not in the 9464D-GD2 tumor model. Addition of checkpoint blockade with anti-CTLA-4 was not effective alone against 9464D-GD2 tumors; inclusion of CpG and anti-CD40 achieved a potent antitumor response with decreased T regulatory cells within the tumors and induction of immunologic memory. CONCLUSIONS:These data suggest that a combined innate and adaptive immunotherapeutic approach can be effective against immunologically cold syngeneic murine neuroblastoma. Further testing is needed to determine how these concepts might translate into development of more effective immunotherapeutic approaches for the treatment of clinically high-risk neuroblastoma.

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Low-dose targeted radionuclide therapy renders immunologically cold tumors responsive to immune checkpoint blockade.

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