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BackgroundTargeted and effective treatment options are needed for solid tumors, including glioblastoma (GBM), where survival rates with standard treatments are typically less than 2 years from diagnosis. Solid tumors pose many barriers to immunotherapies, including therapy half-life and persistence, tumor penetrance, and targeting. Therapeutics delivered systemically may not traffic to the tumor site. If cellular therapies or drugs are able to access the tumor site, or can be delivered directly within the tumor, treatments may not persist for the duration necessary to reduce or eliminate tumor burden. An approach that allows durable and titratable local therapeutic protein delivery could improve antitumor efficacy while minimizing toxicities or unwanted on-target, off-tissue effects.MethodsIn this study, human monocyte-derived macrophages were genetically engineered to secrete a bispecific T cell engager (BiTE) specific to the mutated epidermal growth factor variant III (EGFRvIII) expressed by some GBM tumors. We investigated the ability of lentivirally modified macrophages to secrete a functional BiTE that can bind target tumor antigen and activate T cells. Secreted BiTE protein was assayed in a range of T cell functional assays in vitro and in subcutaneous and intracranial GBM xenograft models. Finally, we tested genetically engineered macrophages (GEMs) secreting BiTE and the proinflammatory cytokine interleukin (IL)-12 to amplify T cell responses in vitro and in vivo.ResultsTransduced human macrophages secreted a lentivirally encoded functional EGFRvIII-targeted BiTE protein capable of inducing T cell activation, proliferation, degranulation, and killing of antigen-specific tumor cells. Furthermore, BiTE secreting macrophages reduced early tumor burden in both subcutaneous and intracranial mouse models of GBM, a response which was enhanced using macrophages that were dual transduced to secrete both the BiTE protein and single chain IL-12, preventing tumor growth in an aggressive GBM model.ConclusionsThe ability of macrophages to infiltrate and persist in solid tumor tissue could overcome many of the obstacles associated with systemic delivery of immunotherapies. We have found that human GEMs can locally and constitutively express one or more therapeutic proteins, which may help recruit T cells and transform the immunosuppressive tumor microenvironment to better support antitumor immunity.

Background Interleukin-10 (IL-10) is an immunosuppressive cytokine that inhibits innate and adaptive antitumor immune responses in the tumor microenvironment (TME). Antibody neutralization of IL-10 in organotypic tumor slice cultures (TSC) in colorectal cancer liver metastases (CRCLM) leads to cancer cell death through. To target IL-10 blockade to the TME, we genetically engineered macrophages (GEM) to produce an IL-10 neutralizing antibody which we hypothesized would reactivate tumor infiltrating immune cells and increase cancer cell death in TSC. Methods We created a lentiviral construct to transduce GEMs with a publicly available neutralizing IL-10 antibody sequence (BT-063). CD14+ monocytes were isolated from healthy donor peripheral blood mononuclear cells and differentiated into macrophages, which were transduced with lentivirus to create control (cGEMs) and anti-IL-10 GEMs (αIL10 GEMs). To test the efficacy of αIL10 GEMs, punch biopsies (6 mm) were obtained from resected CRCLM, sliced to 250 um thickness with a vibratome and placed in individual culture wells. Slices were treated in triplicates with either 20ug/mL of human monoclonal αIL10 (αIL10), 1e5 cGEMs or αIL10 GEMs + 20ug/mL αIL10. GEMs and tumor cells were visualized with a Leica SP8X confocal microscope and apoptosis was measured with SR-FLICA fluorescent poly-caspase assay kit. Supernatant interferon-gamma (IFN-γ) levels were measured with Bioplex immunoassay and IL-10 neutralizing antibody was quantified with an enzyme-linked immunosorbent assay. Results Allogenic GEMs were transduced with BT-063-T2A-CD19t at 31% efficiency. cGEMs and αIL10 GEMs persisted in tumor slice culture for at least 6 days. αIL10 GEM-treated slice cultures contained 6.6ng/mL and 6.5ng/mL of αIL10 antibody after 3 and 6 days, respectively. At day 6 in culture, cancer cell apoptosis was increased in the αIL10 treated groups with 7%, 15%, 25%, 31% and 39% of cells were apoptotic in the no treatment control, cGEM, αIL10, cGEM + αIL10 and αIL10 GEM groups, respectively (One-way ANOVA, p = 0.0004). Elevation in IFN-γ was observed on day 6 in slices treated cGEMs (7.2ng/mL+4.3) and αIL10 GEMs (9.2ng/mL+5) compared to isotype control. Conclusion GEMs transduced with lentivirus encoding IL-10 neutralizing antibody maintain its production and are associated with increased cancer cell apoptosis. Citation Format: Kevin P. Labadie, Shannon A. Kreuser, Katherine J. Brempelis, Xiuyun Jiang, Sara K. Daniel, Courtney A. Crane, Venu G. Pillarisetty. Neutralization of interleukin-10 by genetically engineered macrophages increase cancer cell death in metastatic colorectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5545.

Efforts to reduce immunosuppression in the solid tumor microenvironment by blocking the recruitment or polarization of tumor associated macrophages (TAM), or myeloid derived suppressor cells (MDSCs), have gained momentum in recent years. Expanding our knowledge of the immune cell types, cytokines, or recruitment factors that are associated with high-grade disease, both within the tumor and in circulation, is critical to identifying novel targets for immunotherapy. Furthermore, a better understanding of how therapeutic regimens, such as Dexamethasone (Dex), chemotherapy, and radiation, impact these factors will facilitate the design of therapies that can be targeted to the appropriate populations and retain efficacy when administered in combination with standard of care regimens. Here we perform quantitative analysis of tissue microarrays made of samples taken from grades I-III astrocytoma and glioblastoma (GBM, grade IV astrocytoma) to evaluate infiltration of myeloid markers CD163, CD68, CD33, and S100A9. Serum, flow cytometric, and Nanostring analysis allowed us to further elucidate the impact of Dex treatment on systemic biomarkers, circulating cells, and functional markers within tumor tissue. We found that common myeloid markers were elevated in Dex-treated grade I astrocytoma and GBM compared to non-neoplastic brain tissue and grade II-III astrocytomas. Cell frequencies in these samples differed significantly from those in Dex-naïve patients in a pattern that depended on tumor grade. In contrast, observed changes in serum chemokines or circulating monocytes were independent of disease state and were due to Dex treatment alone. Furthermore, these changes seen in blood were often not reflected within the tumor tissue. Conclusions: Our findings highlight the importance of considering perioperative treatment as well as disease grade when assessing novel therapeutic targets or biomarkers of disease.