Genetically engineered macrophages persist in solid tumors and locally deliver therapeutic proteins to activate immune responses

Abstract

BackgroundThough currently approved immunotherapies, including chimeric antigen receptor T cells and checkpoint blockade antibodies, have been successfully used to treat hematological and some solid tumor cancers, many solid tumors remain resistant to these modes of treatment. In solid tumors, the development of effective antitumor immune responses is hampered by restricted immune cell infiltration and an immunosuppressive tumor microenvironment (TME). An immunotherapy that infiltrates and persists in the solid TME, while providing local, stable levels of therapeutic to activate or reinvigorate antitumor immunity could overcome these challenges faced by current immunotherapies.MethodsUsing lentivirus-driven engineering, we programmed human and murine macrophages to express therapeutic payloads, including Interleukin (IL)-12. In vitro coculture studies were used to evaluate the effect of genetically engineered macrophages (GEMs) secreting IL-12 on T cells and on the GEMs themselves. The effects of IL-12 GEMs on gene expression profiles within the TME and tumor burden were evaluated in syngeneic mouse models of glioblastoma and melanoma and in human tumor slices isolated from patients with advanced gastrointestinal malignancies.ResultsHere, we present a cellular immunotherapy platform using lentivirus-driven genetic engineering of human and mouse macrophages to constitutively express proteins, including secreted cytokines and full-length checkpoint antibodies, as well as cytoplasmic and surface proteins that overcomes these barriers. GEMs traffic to, persist in, and express lentiviral payloads in xenograft mouse models of glioblastoma, and express a non-signaling truncated CD19 surface protein for elimination. IL-12-secreting GEMs activated T cells and induced interferon-gamma (IFNγ) in vitro and slowed tumor growth resulting in extended survival in vivo. In a syngeneic glioblastoma model, IFNγ signaling cascades were also observed in mice treated with mouse bone-marrow-derived GEMs secreting murine IL-12. These findings were reproduced in ex vivo tumor slices comprised of intact MEs. In this setting, IL-12 GEMs induced tumor cell death, chemokines and IFNγ-stimulated genes and proteins.ConclusionsOur data demonstrate that GEMs can precisely deliver titratable doses of therapeutic proteins to the TME to improve safety, tissue penetrance, targeted delivery and pharmacokinetics.

The Role of Macrophages in Cancer Development and Therapy

“…Another promising approach is to induce an anticancer immune response by a genetic modification of macrophages. This approach was used by Brempelis et al, where macrophages were transduced using lentivirus to express IL-12 [ 166 ]. Adoptively transferred engineered macrophages infiltrated experimental tumors and decreased their size, activating T cells and IFNγ production [ 166 ].…”

“…This approach was used by Brempelis et al, where macrophages were transduced using lentivirus to express IL-12 [ 166 ]. Adoptively transferred engineered macrophages infiltrated experimental tumors and decreased their size, activating T cells and IFNγ production [ 166 ]. An alternative approach was executed by Zhang et al using transient genetic modification of TAMs.…”

Protocol for tissue slice cultures from human solid tumors to study therapeutic response

“…The tumor slice culture system can be used to evaluate adoptive cellular therapy. In previously published work ( Brempelis et al., 2020 ) the therapeutic efficacy of genetically engineered macrophages (GEMs) were evaluated in tumor slice culture. The GEMs infiltrate and persist in tumor slice for at least 1 week in culture ( Figure 6 ).…”

“… GEMs are prepared. See previously published work for details ( Brempelis et al., 2020 , Moyes et al., 2017 ). Alternatively, CAR-T cells can be utilized and thawed from frozen aliquots at the time of the experiment.…”

CARs and beyond: tailoring macrophage-based cell therapeutics to combat solid malignancies

“…In the same direction, Brempelis and colleagues transduced murine bone marrow-derived macrophages with a lentiviral vector encoding IL-12. 78 Brempelis and her group also engineered macrophages that secrete a full-length anti-CTLA-4 antibody over 96 hours to enhance the targeted delivery of checkpoint inhibitors. Interferon (IFN)α was chosen as a secretion molecule by Escobar and her group.…”