Chimeric antigen receptor (CAR) T cell therapies have demonstrated remarkable efficacy for the treatment of hematological malignancies. However, in patients with solid tumors, objective responses to ...CAR-T cell therapy remain sporadic and transient. A major obstacle for CAR-T cells is the intrinsic ability of tumors to evade immune responses. Advanced solid tumors are largely composed of desmoplastic stroma and immunosuppressive modulators, and characterized by aberrant cell proliferation and vascularization, resulting in hypoxia and altered nutrient availability. To mount a curative response after infusion, CAR-T cells must infiltrate the tumor, recognize their cognate antigen and perform their effector function in this hostile tumor microenvironment, to then differentiate and persist as memory T cells that confer long-term protection. Fortunately, recent advances in synthetic biology provide a wide set of tools to genetically modify CAR-T cells to overcome some of these obstacles. In this review, we provide a comprehensive overview of the key tumor intrinsic mechanisms that prevent an effective CAR-T cell antitumor response and we discuss the most promising strategies to prevent tumor escape to CAR-T cell therapy.
The rough morphotypes of non-tuberculous mycobacteria have been associated with the most severe illnesses in humans. This idea is consistent with the fact that
presents a stable rough morphotype. ...Unlike smooth morphotypes, the bacilli of rough morphotypes grow close together, leaving no spaces among them and forming large aggregates (clumps). Currently, the initial interaction of macrophages with clumps remains unclear. Thus, we infected J774 macrophages with bacterial suspensions of rough morphotypes of
containing clumps and suspensions of smooth morphotypes, primarily containing isolated bacilli. Using confocal laser scanning microscopy and electron microscopy, we observed clumps of at least five rough-morphotype bacilli inside the phagocytic vesicles of macrophages at 3 h post-infection. These clumps grew within the phagocytic vesicles, killing 100% of the macrophages at 72 h post-infection, whereas the proliferation of macrophages infected with smooth morphotypes remained unaltered at 96 h post-infection. Thus, macrophages phagocytose large clumps, exceeding the bactericidal capacities of these cells. Furthermore, proinflammatory cytokines and granuloma-like structures were only produced by macrophages infected with rough morphotypes. Thus, the present study provides a foundation for further studies that consider mycobacterial clumps as virulence factors.
The arsenal against different types of cancers has increased impressively in the last decade. The detailed knowledge of the tumor microenvironment enables it to be manipulated in order to help the ...immune system fight against tumor cells by using specific checkpoint inhibitors, cell-based treatments, targeted antibodies, and immune stimulants. In fact, it is widely known that the first immunotherapeutic tools as immune stimulants for cancer treatment were bacteria and still are; specifically, the use of Mycobacterium bovis bacillus Calmette-Guérin (BCG) continues to be the treatment of choice for preventing cancer recurrence and progression in non-invasive bladder cancer. BCG and also other mycobacteria or their components are currently under study for the immunotherapeutic treatment of different malignancies. This review focuses on the preclinical and clinical assays using mycobacteria to treat non-urological cancers, providing a wide knowledge of the beneficial applications of these microorganisms to manipulate the tumor microenvironment aiming at tumor clearance.
The standard treatment for high-risk non-muscle invasive bladder cancer (BC) is the intravesical administration of live Mycobacterium bovis BCG. Previous studies suggest improving this therapy by ...implementing non-pathogenic mycobacteria, such as Mycobacterium brumae, and/or different vehicles for mycobacteria delivery, such as an olive oil (OO)-in-water emulsion. While it has been established that BCG treatment activates the immune system, the immune effects of altering the mycobacterium and/or the preparation remain unknown. In an orthotopic murine BC model, local immune responses were assessed by measuring immune cells into the bladder and macromolecules in the urine by flow cytometry and multiplexing, respectively. Systemic immune responses were analyzed by quantifying sera anti-mycobacteria antibody levels and recall responses of ex vivo splenocytes cultured with mycobacteria antigens. In both BCG- and M. brumae-treated mice, T, NK, and NKT cell infiltration in the bladder was significantly increased. Notably, T cell infiltration was enhanced in OO-in-water emulsified mycobacteria-treated mice, and urine IL-6 and KC concentrations were elevated. Furthermore, mycobacteria treatment augmented IgG antibody production and splenocyte proliferation, especially in mice receiving OO-in-water emulsified mycobacteria. Our data demonstrate that intravesical mycobacterial treatment triggers local and systemic immune responses, which are most significant when OO-in-water emulsified mycobacteria are used.
The hydrophobic composition of mycobacterial cell walls leads to the formation of clumps when attempting to resuspend mycobacteria in aqueous solutions. Such aggregation may interfere in the ...mycobacteria-host cells interaction and, consequently, influence their antitumor effect. To improve the immunotherapeutic activity of Mycobacterium brumae, we designed different emulsions and demonstrated their efficacy. The best formulation was initially selected based on homogeneity and stability. Both olive oil (OO)- and mineral oil-in-water emulsions better preserved the mycobacteria viability and provided higher disaggregation rates compared to the others. But, among both emulsions, the OO emulsion increased the mycobacteria capacity to induce cytokines' production in bladder tumor cell cultures. The OO-mycobacteria emulsion properties: less hydrophobic, lower pH, more neutralized zeta potential, and increased affinity to fibronectin than non-emulsified mycobacteria, indicated favorable conditions for reaching the bladder epithelium in vivo. Finally, intravesical OO-M. brumae-treated mice showed a significantly higher systemic immune response, together with a trend toward increased tumor-bearing mouse survival rates compared to the rest of the treated mice. The physicochemical characteristics and the induction of a robust immune response in vitro and in vivo highlight the potential of the OO emulsion as a good delivery vehicle for the mycobacterial treatment of bladder cancer.
The mechanism of action of intravesical Mycobacterium bovis BCG immunotherapy treatment for bladder cancer is not completely known, leading to misinterpretation of BCG-unresponsive patients, who have ...scarce further therapeutic options. BCG is grown under diverse culture conditions worldwide, which can impact the antitumor effect of BCG strains and could be a key parameter of treatment success. Here, BCG and the nonpathogenic Mycobacterium brumae were grown in four culture media currently used by research laboratories and BCG manufacturers: Sauton-A60, -G15 and -G60 and Middlebrook 7H10, and used as therapies in the orthotopic murine BC model. Our data reveal that each mycobacterium requires specific culture conditions to induce an effective antitumor response. since higher survival rates of tumor-bearing mice were achieved using M. brumae-A60 and BCG-G15 than the rest of the treatments. M. brumae-A60 was the most efficacious among all tested treatments in terms of mouse survival, cytotoxic activity of splenocytes against tumor cells, higher systemic production of IL-17 and IFN-ɣ, and bladder infiltration of selected immune cells such as ILCs and CD4
TEM
. BCG-G15 triggered an antitumor activity based on a massive infiltration of immune cells, mainly CD3
+
(CD4
+
and CD8
+
) T cells, together with high systemic IFN-ɣ release. Finally, a reduced variety of lipids was strikingly observed in the outermost layer of M. brumae-A60 and BCG-G15 compared to the rest of the cultures, suggesting an influence on the antitumor immune response triggered. These findings contribute to understand how mycobacteria create an adequate niche to help the host subvert immunosuppressive tumor actions.
New strategies are needed to enhance the efficacy of anti-programmed cell death protein antibody (anti-PD-1 Ab) in cancer. Here, we report that inhibiting palmitoyl-protein thioesterase 1 (PPT1), a ...target of chloroquine derivatives like hydroxychloroquine (HCQ), enhances the antitumor efficacy of anti-PD-1 Ab in melanoma. The combination resulted in tumor growth impairment and improved survival in mouse models. Genetic suppression of core autophagy genes, but not Ppt1, in cancer cells reduced priming and cytotoxic capacity of primed T cells. Exposure of antigen-primed T cells to macrophage-conditioned medium derived from macrophages treated with PPT1 inhibitors enhanced melanoma-specific killing. Genetic or chemical Ppt1 inhibition resulted in M2 to M1 phenotype switching in macrophages. The combination was associated with a reduction in myeloid-derived suppressor cells in the tumor. Ppt1 inhibition by HCQ, or DC661, induced cyclic GMP-AMP synthase/stimulator of interferon genes/TANK binding kinase 1 pathway activation and the secretion of interferon-β in macrophages, the latter being a key component for augmented T cell-mediated cytotoxicity. Genetic Ppt1 inhibition produced similar findings. These data provide the rationale for this combination in melanoma clinical trials and further investigation in other cancers.
BackgroundChimeric Antigen Receptor T cells (CARTs) are a powerful anti-cancer therapy, demonstrating success in hematologic malignancies. The development of targeted lipid nanoparticle-mRNA ...(tLNP-mRNA) therapeutics has allowed for the generation of CARTs in situ and may resolve several challenges of conventional ex vivo viral-engineered CAR T cell products including scalability, access and mulitplexing. The in situ T cell transfection rate achieved by tLNP-mRNA varies from 4–20% of T cells expressing the protein of interest. As tLNP-mRNA platform efficacy may critically depend on the number, metabolic state, and localization of engineered T cells, we investigated whether cytokines could enhance protein expression.MethodsWe used tLNPs that target CD5, a marker expressed highly on mouse and human T cells. These tLNPs carried the mRNA for the reporter protein mCherry or encoded a fibroblast activated protein (FAP) targeted CAR. Mouse and human T cells were cultured with IL2, IL7, IL15 or activated using αCD3/CD28. CD5-mCherry-tLNPs or CD5-FAPCAR-tLNPs were added and protein expression was detected using flow cytometry. For in vivo studies, C57BL/6 mice were pretreated with IL7, injected with tLNPs and sacrificed 24 hours later. To analyze the T cell transcriptome, CD8+ T cells were isolated from mouse spleens and cultured with IL2, IL7 or IL15 for 48 hours before being sequenced.ResultsWe found that CD5-mCherry-tLNPs induced protein expression on 10% of resting T cells in vivo and ~15% of T cells in vivo. Culturing mouse and human T cells with IL7 significantly improved CD5-mCherry-tLNPs protein expression in vitro. This also occurred in the in vivo setting as pre-treating mice with IL7 elevated both the proportion and total number of mCherry expressing T cells. FAPCAR expression was also increased by combining CD5-FAPCAR-tLNPs with recombinant IL7. Transcriptomic analysis showed IL7 selectively increased pathways associated with protein translation. The significance of these transcriptomic changes was demonstrated by showing that after electroporation with mRNA, T cells cultured in IL7 produced more protein compared to IL2 or IL15.ConclusionsT cells can be engineered in situ using CD5-targeted tLNPs and IL7 increases the protein expression induced by tLNPs. Our data suggests that the upregulation of translation-associated pathways in T cells by IL7 could be exploited to improve the expression of proteins in situ after tLNP administration. This provides a novel paradigm through which a T cell activating cytokine, instead of lymphodepletion, can potentiate in situ CAR T cell therapy.Ethics ApprovalThis study was approved by The University of Pennsylvania’s Ethics Board; approval number 806099.
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