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Rationale for Combining Radiotherapy and Immune Checkpoint Inhibition for Patients With Hypoxic Tumors.

ABSTRACT: In order to compensate for the increased oxygen consumption in growing tumors, tumors need angiogenesis and vasculogenesis to increase the supply. Insufficiency in this process or in the microcirculation leads to hypoxic tumor areas with a significantly reduced pO2, which in turn leads to alterations in the biology of cancer cells as well as in the tumor microenvironment. Cancer cells develop more aggressive phenotypes, stem cell features and are more prone to metastasis formation and migration. In addition, intratumoral hypoxia confers therapy resistance, specifically radioresistance. Reactive oxygen species are crucial in fixing DNA breaks after ionizing radiation. Thus, hypoxic tumor cells show a two- to threefold increase in radioresistance. The microenvironment is enriched with chemokines (e.g., SDF-1) and growth factors (e.g., TGF?) additionally reducing radiosensitivity. During recent years hypoxia has also been identified as a major factor for immune suppression in the tumor microenvironment. Hypoxic tumors show increased numbers of myeloid derived suppressor cells (MDSCs) as well as regulatory T cells (Tregs) and decreased infiltration and activation of cytotoxic T cells. The combination of radiotherapy with immune checkpoint inhibition is on the rise in the treatment of metastatic cancer patients, but is also tested in multiple curative treatment settings. There is a strong rationale for synergistic effects, such as increased T cell infiltration in irradiated tumors and mitigation of radiation-induced immunosuppressive mechanisms such as PD-L1 upregulation by immune checkpoint inhibition. Given the worse prognosis of patients with hypoxic tumors due to local therapy resistance but also increased rate of distant metastases and the strong immune suppression induced by hypoxia, we hypothesize that the subgroup of patients with hypoxic tumors might be of special interest for combining immune checkpoint inhibition with radiotherapy.

SUBMITTER: Eckert F

PROVIDER: S-EPMC6423917 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Rationale for Combining Radiotherapy and Immune Checkpoint Inhibition for Patients With Hypoxic Tumors.

Eckert Franziska F Zwirner Kerstin K Boeke Simon S Thorwarth Daniela D Zips Daniel D Huber Stephan M SM

Frontiers in immunology 20190312

In order to compensate for the increased oxygen consumption in growing tumors, tumors need angiogenesis and vasculogenesis to increase the supply. Insufficiency in this process or in the microcirculation leads to hypoxic tumor areas with a significantly reduced pO2, which in turn leads to alterations in the biology of cancer cells as well as in the tumor microenvironment. Cancer cells develop more aggressive phenotypes, stem cell features and are more prone to metastasis formation and migration. ...[more]

PMID: 30930892

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Project description:BackgroundImmune checkpoint inhibitors (ICIs) for solid tumors, including those targeting programmed cell death 1 (PD-1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), have shown impressive clinical efficacy, however, most patients do not achieve durable responses. One major therapeutic obstacle is the immunosuppressive tumor immune microenvironment (TIME). Thus, we hypothesized that a strategy combining tumor-directed radiation with TIME immunomodulation could improve ICI response rates in established solid tumors.MethodsUsing a syngeneic mouse model of human papillomavirus (HPV)-associated head and neck cancer, mEER, we developed a maximally effective regimen combining PD-1 and CTLA-4 inhibition, tumor-directed radiation, and two existing immunomodulatory drugs: cyclophosphamide (CTX) and a small-molecule inducible nitric oxide synthase (iNOS) inhibitor, L-n6-(1-iminoethyl)-lysine (L-NIL). We compared the effects of the various combinations of this regimen on tumor growth, overall survival, establishment of immunologic memory, and immunologic changes with flow cytometry and quantitative multiplex immunofluorescence.ResultsWe found PD-1 and CTLA-4 blockade, and radiotherapy alone or in combination, incapable of clearing established tumors or reversing the unfavorable balance of effector to suppressor cells in the TIME. However, modulation of the TIME with cyclophosphamide (CTX) and L-NIL in combination with dual checkpoint inhibition and radiation led to rejection of over 70% of established mEER tumors and doubled median survival in the B16 melanoma model. Anti-tumor activity was CD8+ T cell-dependent and led to development of immunologic memory against tumor-associated HPV antigens. Immune profiling revealed that CTX/L-NIL induced remodeling of myeloid cell populations in the TIME and tumor-draining lymph node and drove subsequent activation and intratumoral infiltration of CD8+ effector T cells.ConclusionsOverall, this study demonstrates that modulation of the immunosuppressive TIME is required to unlock the benefits of ICIs and radiotherapy to induce immunologic rejection of treatment-refractory established solid tumors.

Project description:BackgroundImmune checkpoint inhibitors and vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors are the most commonly used medications in metastatic renal cell carcinoma (mRCC). Recently, large clinical trials have shown favorable outcomes in patients treated with combined immune checkpoint plus VEGFR inhibition compared with VEGFR inhibition alone. However, the benefit among favorable risk (based on International Metastatic Renal Cell Carcinoma Database Consortium score) and elderly (age > 65 years) patients was not clear, leading to a discrepancy between United States Food and Drug Administration and European Association of Urology recommendations.Materials and methodsWe searched available literature for phase III randomized clinical trials evaluating the efficacy of combining immunotherapy plus VEGF/VEGFR inhibitors versus standard of care in patients with previously untreated mRCC. Combinations that were included in United States Food and Drug Administration recommendations or European Association of Urology guidelines were used for analysis. We performed a meta-analysis with a random effects model to evaluate the efficacy of immunotherapy-VEGFR inhibitor combinations compared with sunitinib in favorable risk and elderly patients.ResultsOur analysis demonstrated that progression-free survival (PFS) was significantly prolonged with combination therapy compared with sunitinib in patients with age > 65 years (hazard ratio, 0.66; 95% confidence interval, 0.52-0.84; P = .001). The PFS in favorable risk disease was improved with combination therapy compared with sunitinib, but the difference was not statistically significant (hazard ratio, 0.68; 95% confidence interval, 0.46-1.01; P = .055).ConclusionOur meta-analysis strengthens the trend of beneficial effect in prolonging PFS in both subgroups compared with each trial alone, indicating that favorable risk and elderly patients with mRCC likely benefit from combining programmed cell death 1 or programmed cell death-ligand 1 and VEGFR inhibition.

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Rationale for Combining Radiotherapy and Immune Checkpoint Inhibition for Patients With Hypoxic Tumors.

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Rationale for Combining Radiotherapy and Immune Checkpoint Inhibition for Patients With Hypoxic Tumors.

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