Checkpoint inhibitor-expressing lentiviral vaccine suppresses tumor growth in preclinical cancer models

BACKGROUND

While immunotherapy has been highly successful for the treatment of some cancers, for others, the immune response to tumor antigens is weak leading to treatment failure. The resistance of tumors to checkpoint inhibitor therapy may be caused by T cell exhaustion resulting from checkpoint activation.

METHODS

In this study, lentiviral vectors that expressed T cell epitopes of an experimentally introduced tumor antigen, ovalbumin, or the endogenous tumor antigen, Trp1 were developed. The vectors coexpressed CD40 ligand (CD40L), which served to mature the dendritic cells (DCs), and a soluble programmed cell death protein 1 (PD-1) microbody to prevent checkpoint activation. Vaccination of mice bearing B16.OVA melanomas with vector-transduced DCs induced the proliferation and activation of functional, antigen-specific, cytolytic CD8 T cells.

RESULTS

Vaccination induced the expansion of CD8 T cells that infiltrated the tumors to suppress tumor growth. Vector-encoded CD40L and PD-1 microbody increased the extent of tumor growth suppression. Adoptive transfer demonstrated that the effect was mediated by CD8 T cells. Direct injection of the vector, without the need for ex vivo transduction of DCs, was also effective.

CONCLUSIONS

This study suggests that therapeutic vaccination that induces tumor antigen-specific CD8 T cells coupled with a vector-expressed checkpoint inhibitor can be an effective means to suppress the growth of tumors that are resistant to conventional immunotherapy.

Hypofractionated radiotherapy combined with lenalidomide improves systemic antitumor activity in mouse solid tumor models

Background: Hypofractionated radiotherapy (hRT) can induce a T cell-mediated abscopal effect on non-irradiated tumor lesions, especially in combination with immune checkpoint blockade (ICB). However, clinically, this effect is still rare, and ICB-mediated adverse events are common. Lenalidomide (lena) is an anti-angiogenic and immunomodulatory drug used in the treatment of hematologic malignancies. We here investigated in solid tumor models whether lena can enhance the abscopal effect in double combination with hRT. Methods: In two syngeneic bilateral tumor models (B16-CD133 melanoma and MC38 colon carcinoma), the primary tumor was treated with hRT. Lena was given daily for 3 weeks. Besides tumor size and survival, the dependence of the antitumor effects on CD8+ cells, type-I IFN signaling, and T cell costimulation was determined with depleting or blocking antibodies. Tumor-specific CD8+ T cells were quantified, and their differentiation and effector status were characterized by multicolor flow cytometry using MHC-I tetramers and various antibodies. In addition, dendritic cell (DC)-mediated tumor antigen cross-presentation in vitro and directly ex vivo and the composition of tumor-associated vascular endothelial cells were investigated. Results: In both tumor models, the hRT/lena double combination induced a significant abscopal effect. Control of the non-irradiated secondary tumor and survival were considerably better than with the respective monotherapies. The abscopal effect was strongly dependent on CD8+ cells and associated with an increase in tumor-specific CD8+ T cells in the non-irradiated tumor and its draining lymph nodes. Additionally, we found more tumor-specific T cells with a stem-like (TCF1+ TIM3- PD1+) and a transitory (TCF1- TIM3+ CD101- PD1+) exhausted phenotype and more expressing effector molecules such as GzmB, IFNγ, and TNFα. Moreover, in the non-irradiated tumor, hRT/lena treatment also increased DCs cross-presenting a tumor model antigen. Blocking type-I IFN signaling, which is essential for cross-presentation, completely abrogated the abscopal effect. A gene expression analysis of bone marrow-derived DCs revealed that lena augmented the expression of IFN response genes and genes associated with differentiation, maturation (including CD70, CD83, and CD86), migration to lymph nodes, and T cell activation. Flow cytometry confirmed an increase in CD70+ CD83+ CD86+ DCs in both irradiated and abscopal tumors. Moreover, the hRT/lena-induced abscopal effect was diminished when these costimulatory molecules were blocked simultaneously using antibodies. In line with the enhanced infiltration by DCs and tumor-specific CD8+ T cells, including more stem-like cells, hRT/lena also increased tumor-associated high endothelial cells (TA-HECs) in the non-irradiated tumor. Conclusions: We demonstrate that lena can augment the hRT-induced abscopal effect in mouse solid tumor models in a CD8 T cell- and IFN-I-dependent manner, correlating with enhanced anti-tumor CD8 T cell immunity, DC cross-presentation, and TA-HEC numbers. Our findings may be helpful for the planning of clinical trials in (oligo)metastatic patients.

Acellular scaffold-based approach for in situ genetic engineering of host T-cells in solid tumor immunotherapy

BACKGROUND

Targeted T-cell therapy has emerged as a promising strategy for the treatment of hematological malignancies. However, its application to solid tumors presents significant challenges due to the limited accessibility and heterogeneity. Localized delivery of tumor-specific T-cells using biomaterials has shown promise, however, procedures required for genetic modification and generation of a sufficient number of tumor-specific T-cells ex vivo remain major obstacles due to cost and time constraints.

METHODS

Polyethylene glycol (PEG)-based three-dimensional (3D) scaffolds were developed and conjugated with positively charged poly-L-lysine (PLL) using carbamide chemistry for efficient loading of lentiviruses (LVs) carrying tumor antigen-specific T-cell receptors (TCRs). The physical and biological properties of the scaffold were extensively characterized. Further, the scaffold loaded with OVA-TCR LVs was implanted in B16F10 cells expressing ovalbumin (B16-OVA) tumor model to evaluate the anti-tumor response and the presence of transduced T-cells.

RESULTS

Our findings demonstrate that the scaffolds do not induce any systemic inflammation upon subcutaneous implantation and effectively recruit T-cells to the site. In B16-OVA melanoma tumor-bearing mice, the scaffolds efficiently transduce host T-cells with OVA-specific TCRs. These genetically modified T-cells exhibit homing capability towards the tumor and secondary lymphoid organs, resulting in a significant reduction of tumor size and systemic increase in anti-tumor cytokines. Immune cell profiling revealed a significantly high percentage of transduced T-cells and a notable reduction in suppressor immune cells within the tumors of mice implanted with these scaffolds.

CONCLUSION

Our scaffold-based T-cell therapy presents an innovative in situ localized approach for programming T-cells to target solid tumors. This approach offers a viable alternative to in vitro manipulation of T-cells, circumventing the need for large-scale in vitro generation and culture of tumor-specific T-cells. It offers an off-the-shelf alternative that facilitates the use of host cells instead of allogeneic cells, thereby, overcoming a major hurdle.

Development of Recombinant Oncolytic rVSV-mIL12-mGMCSF for Cancer Immunotherapy

Anti-cancer therapy based on oncolytic viruses (OVs) is a targeted approach that takes advantage of OVs' ability to selectively infect and replicate in tumor cells, activate the host immune response, and destroy malignant cells over healthy ones. Vesicular stomatitis virus (VSV) is known for its wide range of advantages: a lack of pre-existing immunity, a genome that is easily amenable to manipulation, and rapid growth to high titers in a broad range of cell lines, to name a few. VSV-induced tumor immunity can be enhanced by the delivery of immunostimulatory cytokines. The targeted cytokine delivery to tumors avoids the significant toxicity associated with systemic delivery while also boosting the immune response. To demonstrate this enhanced effect on both tumor growth and survival, a novel recombinant VSV (rVSV)-mIL12-mGMCSF, co-expressing mouse IL-12 (interleukin-12) and GM-CSF (granulocyte-macrophage colony-stimulating factor), was tested alongside rVSV-dM51-GFP (rVSV-GFP) that was injected intratumorally in a syngeneic in vivo C57BL/6 mouse model infused subcutaneously with B16-F10 melanoma cells. The pilot study tested the effect of two viral injections 4 days apart and demonstrated that treatment with the two rVSVs resulted in partial inhibition of tumor growth (TGII of around 40%) and an increased survival rate in animals from the treatment groups. The effect of the two VSVs on immune cell populations will be investigated in future in vivo studies with an optimized experimental design with multiple higher viral doses, as a lack of this information presents a limitation of this study.

Combination therapy of HIFα inhibitors and Treg depletion strengthen the anti-tumor immunity in mice

Hypoxia-inducible factor 1 alpha (HIF1α), under hypoxic conditions, is known to play an oxygen sensor stabilizing role by exerting context- and cell-dependent stimulatory and inhibitory functions in immune cells. Nevertheless, how HIF1α regulates T cell differentiation and functions in tumor settings has not been elucidated. Herein, we demonstrated that T-cell-specific deletion of HIF1α improves the inflammatory potential and memory phenotype of CD8+ T cells. We validated that T cell-specific HIF1α ablation reduced the B16 melanomas development with the indication of ameliorated antitumor immune response with enhanced IFN-γ+ CD8+ T cells despite the increase in the Foxp3+ regulatory T-cell population. This was further verified by treating tumor-bearing mice with a HIF1α inhibitor. Results indicated that HIF1α inhibitor also recapitulates HIF1α ablation effects by declining tumor growth and enhancing the memory and inflammatory potential of CD8+ T cells. Furthermore, a combination of Treg inhibitor with HIF1α inhibitor can substantially reduce tumor size. Collectively, these findings highlight the notable roles of HIF1α in distinct CD8+ T-cell subsets. This study suggests the significant implications for enhancing the potential of T cell-based antitumor immunity by combining HIF1α and Tregs inhibitors.

Manganese-mineralized cancer cells as immunogenic cancer vaccines for tumor immunotherapy

The strategy of using tumor cells to construct whole-cell cancer vaccines has received widespread attention. However, the limited immunogenicity of inactivated tumor cells and the challenge of overcoming immune suppression in solid tumors have hindered the application of whole-cell-based cancer immune therapy. Inspired by the regulatory effects of MnO2 and spatiotemporal control capability of material layers in cell surface engineering, we developed a manganese (Mn)-mineralized tumor cell, B16F10@MnO2, by inactivating B16F10 melanoma cells with KMnO4 to generate manganese-mineralized tumor cells. The cell-based composite was formed by combining amorphous MnO2 with the membrane structure of cells based on the redox reaction between KMnO4 and tumor cells. The MnO2 layer induced a stronger phagocytosis of ovalbumin (OVA)-expressing tumor cells by antigen presenting cells than formaldehyde-fixed cells did, resulting in specific antigen-presentation in vitro and in vivo and subsequent immune responses. Intratumoral therapy with B16F10@MnO2 inhibited B16F10 tumor growth. Moreover, the infiltration of CD8+ T cells within B16F10 solid tumors and the proportion of central memory T cells both increased in B16F10@MnO2 treated tumor-bearing mice, indicating enhanced adaptive immunity. This study provides a convenient and effective method to improve whole-cell-based anti-tumor therapy.

Small EV-based delivery of CpG ODNs for melanoma postsurgical immunotherapy

Blocking programmed cell death protein 1 (PD-1) is an effective therapeutic strategy for melanoma. However, patients often develop tumor recurrence postoperatively due to the low response rate to the anti-PD-1 antibody (aPD-1). In this study, we developed an in situ sprayable fibrin gel that contains cytosine-guanine oligodeoxynucleotides (CpG ODNs)-modified ovalbumin (OVA) antigen-expressing bone marrow dendritic cell (DC)-derived small extracellular vesicles (DC-sEVs) and aPD-1. CpG ODNs can activate DCs, which have potent immunostimulatory effects, by stimulating both the maturation and activation of tumor-infiltrating dendritic cells (TIDCs) and DCs in tumor-draining lymph nodes (TDLNs). In addition, DC-sEVs can deliver OVA to the same DCs, leading to the specific expression of tumor antigens by antigen-presenting cells (APCs). In brief, the unique synergistic combination of aPD-1 and colocalized delivery of immune adjuvants and tumor antigens enhances antitumor T-cell immunity, not only in the tumor microenvironment (TME) but also in TDLNs. This effectively attenuates local tumor recurrence and metastasis. Our results suggest that dual activation by CpG ODNs prolongs the survival of mice and decreases the recurrence rate in an incomplete tumor resection model, providing a promising approach to prevent B16-F10-OVA melanoma tumor recurrence and metastasis.

Branched hydrophobic tails in lipid nanoparticles enhance mRNA delivery for cancer immunotherapy

Efficient and safe delivery of vulnerable mRNA is a long-standing challenge for the broad application of the emerging mRNA-based therapeutics. Herein, a combinatorial library containing 119 novel lipids was constructed via sequential aza-Michael addition reactions of arylates and varying amines to tackle the ongoing challenge in mRNA delivery. Through in vitro screening of the lipid library on IGROV 1 cells, we identified several synthetic lipids with superior mRNA delivery efficacy. The delivery capability of these lipids was verified by the potent expression of luciferase in BALB/c mice upon intravenous administration of luciferase-encoding mRNA lipid nanoparticles (LNPs). Further investigations on the structure-activity relationship revealed that lipids with branched hydrophobic tails were better at delivering mRNA than those containing linear tails at the similar total number of carbons. In comparison to linear tails, the branched tails endowed LNPs with less inner hydrophobicity, fewer surface charges, and proper stability, which benefits the cellular uptake of LNPs and the intracellular trafficking of mRNA, thus improves the delivery efficacy of mRNA. The therapeutical potential of the lead LNPs was evaluated by delivering ovalbumin (OVA)-encoding mRNA to mice bearing B16-OVA melanoma tumors. The results demonstrated that the administration of OVA mRNA LNPs significantly activated CD8+ T cells in tumor microenvironment and substantially prohibited the growth of the aggressive B16-OVA tumors. The robust antitumor efficacy highlights the great potential of these LNPs in cancer immunotherapy.

Calorie Restriction Impairs Anti-Tumor Immune Responses in an Immunogenic Preclinical Cancer Model

(1) Background: Although the important role of dietary energy intake in regulating both cancer progression and host immunity has been widely recognized, it remains unclear whether dietary calorie restriction (CR) has any impact on anti-tumor immune responses. (2) Methods: Using an immunogenic B16 melanoma cell expressing ovalbumin (B16-OVA), we examined the effect of the CR diet on B16-OVA tumor growth and host immune responses. To further test whether the CR diet affects the efficacy of cancer immunotherapy, we examined the effect of CR against anti-PD-1 monoclonal antibody (anti-PD-1 Ab) treatment. (3) Results: The CR diet significantly slowed down the tumor growth of B16-OVA without affecting both CD4+ and CD8+ T cell infiltration into the tumor. Although in vivo depletion of CD8+ T cells facilitated B16-OVA tumor growth in the control diet group, there was no significant change in the tumor growth in the CR diet group with or without CD8+ T cell-depletion. Anti-PD-1 Ab treatment lost its efficacy to suppress tumor growth along with the activation and metabolic shift of CD8+ T cells under CR condition. (4) Conclusions: Our present results suggest that a physical condition restricted in energy intake in cancer patients may impair CD8+ T cell immune surveillance and the efficacy of immunotherapy.

Experimental Melanoma Immunotherapy Model Using Tumor Vaccination with a Hematopoietic Cytokine

Fms-like tyrosine kinase 3 ligand (Flt3L) is a hematopoietic cytokine that promotes the survival and differentiation of dendritic cells (DCs). It has been used in tumor vaccines to activate innate immunity and enhance antitumor responses. This protocol demonstrates a therapeutic model using cell-based tumor vaccine consisting of Flt3L-expressing B16-F10 melanoma cells along with phenotypic and functional analysis of immune cells in the tumor microenvironment (TME). Procedures for cultured tumor cell preparation, tumor implantation, cell irradiation, tumor size measurement, intratumoral immune cell isolation, and flow cytometry analysis are described. The overall goal of this protocol is to provide a preclinical solid tumor immunotherapy model, and a research platform to study the relationship between tumor cells and infiltrating immune cells. The immunotherapy protocol described here can be combined with other therapeutic modalities, such as immune checkpoint blockade (anti-CTLA-4, anti-PD-1, anti-PD-L1 antibodies) or chemotherapy in order to improve the cancer therapeutic effect of melanoma.

Assessing the Efficiency of Triangular Gold Nanoparticles as NIR Photothermal Agents In Vitro and Melanoma Tumor Model

Photothermal therapy (PTT) is gaining a lot of interest as a cancer treatment option with minimal side effects due to the efficient photothermal agents employed. They are based on nanomaterials that, upon laser irradiation, absorb photon energy and convert it into heat to induce hyperthermia, which destroys the cancer cells. Here, the unique light-to-heat conversion features of three different gold nanotriangular nanoparticles (AuNTs) are evaluated with respect to their absorption properties to select the most efficient nanoheater with the highest potential to operate as an efficient photothermal agent. AuNTs with LSPR response in- and out- of resonance with the 785 nm near-infrared (NIR) excitation wavelength are investigated. Upon 15 min laser exposure, the AuNTs that exhibit a plasmonic response in resonance with the 785 nm laser line show the highest photothermal conversion efficacy of 80%, which correlates with a temperature increase of 22 °C. These photothermal properties are well-preserved in agarose-based skin biological phantoms that mimic the melanoma tumoral tissue and surrounding healthy tissue. Finally, in vitro studies on B16.F10 melanoma cells prove by fluorescence staining and MTT assay that the highest phototoxic effect after NIR laser exposure is induced by AuNTs with LSPR response in resonance with the employed laser line, thus demonstrating their potential implementation as efficient photothermal agents in PTT.

Targeting of palpable B16-F10 melanoma tumors with polyclonal antibodies on white blood cells

BACKGROUND

Antibodies and other recognition molecules direct cancer cell death by multiple types of immune cells. Therapy directed at only one target typically results in tumor regrowth because of tumor heterogeneity. Our goal is to direct therapy to multiple targets simultaneously. Our previous studies showed that multiple antibodies targeting mutated tumor proteins inhibited tumor growth when injected subcutaneously near the time of cancer cell implantation.

METHODS

A cocktail of rabbit antibodies against B16-F10 cell surface related mutated proteins were generated. Implanted B16-F10 cells were allowed to grow to palpable size before treatment. Antibodies were administered using different routes of exposure. Free antibody was compared to antibody armed on mouse splenic white blood cells (WBCs). Binding of the antibody cocktail was determined for mouse and human WBCs.

RESULTS

The antibody cocktail inhibited tumor growth and prolonged survival when administered as free antibody or armed on WBCs. The antibody cocktail armed on WBCs achieved similar tumor inhibition as free antibody but at a dose 1000-fold less. Armed WBCs achieved tumor inhibition by intravenous and subcutaneous administration. The antibody cocktail bound well to human WBCs and saturation dose was defined. Binding was stable under simulated in vivo condition in human plasma at 37 °C.

CONCLUSIONS

Antibodies targeting multiple tumor mutated proteins inhibited tumor growth and prolonged survival. Effective antibody dose was reduced 1000-fold by arming WBCs. Rabbit antibodies saturated human WBCs using <1 mg per billion cells. A phase I trial in cancer patients using this strategy has been approved by the FDA.

Enforcing GLUT3 expression in CD8+ T cells improves fitness and tumor control by promoting glucose uptake and energy storage

Despite the tremendous success of adoptive T-cell therapies (ACT) in fighting certain hematologic malignancies, not all patients respond, a proportion experience relapse, and effective ACT of most solid tumors remains elusive. In order to improve responses to ACT suppressive barriers in the solid tumor microenvironment (TME) including insufficient nutrient availability must be overcome. Here we explored how enforced expression of the high-affinity glucose transporter GLUT3 impacted tumor-directed T cells. Overexpression of GLUT3 in primary murine CD8⁺ T cells enhanced glucose uptake and increased glycogen and fatty acid storage, and was associated with increased mitochondrial fitness, reduced ROS levels, higher abundance of the anti-apoptotic protein Mcl-1, and better resistance to stress. Importantly, GLUT3-OT1 T cells conferred superior control of B16-OVA melanoma tumors and, in this same model, significantly improved survival. Moreover, a proportion of treated mice were cured and protected from re-challenge, indicative of long-term T cell persistence and memory formation. Enforcing expression of GLUT3 is thus a promising strategy to improve metabolic fitness and sustaining CD8⁺ T cell effector function in the context of ACT.

[68Ga]Ga-DOTA-Siglec-9 Detects Pharmacodynamic Changes of FAP-Targeted IL2 Variant Immunotherapy in B16-FAP Melanoma Mice

Vascular adhesion protein-1 (VAP-1) is an inflammation-inducible adhesion molecule, which supports contact between leukocytes and inflamed endothelium. There is evidence that VAP-1 is involved in the recruitment of leukocytes to melanoma tumors. Interleukin-2 (IL-2)-based immunotherapy is an efficient therapy that promotes immune system activity against cancers but is associated with toxicity. In the present study, we evaluated the feasibility of PET/CT imaging using the radiotracer [⁶⁸Ga]Ga-DOTA-Siglec-9, which is targeted to VAP-1, to monitor pharmacodynamic effects of a novel FAP-IL2v immunocytokine (a genetically engineered variant of IL-2 fused with fibroblast activation protein) in the B16-FAP melanoma model. At 9 days after the inoculation of B16-FAP melanoma cells, mice were studied with [⁶⁸Ga]Ga-DOTA-Siglec-9 PET/CT as a baseline measurement. Immediately after baseline imaging, mice were treated with FAP-IL2v or vehicle, and treatment was repeated 3 days later. Subsequent PET/CT imaging was performed 3, 5, and 7 days after baseline imaging. In addition to in vivo PET imaging, ex vivo autoradiography, histology, and immunofluorescence staining were performed on excised tumors. B16-FAP tumors were clearly detected with [⁶⁸Ga]Ga-DOTA-Siglec-9 PET/CT during the follow-up period, without differences in tumor volume between FAP-IL2v-treated and vehicle-treated groups. Tumor-to-muscle uptake of [⁶⁸Ga]Ga-DOTA-Siglec-9 was significantly higher in the FAP-IL2v-treated group than in the vehicle-treated group 7 days after baseline imaging, and this was confirmed by tumor autoradiography analysis. FAP-IL2v treatment did not affect VAP-1 expression on the tumor vasculature. However, FAP-IL2v treatment increased the number of CD8⁺ T cells and natural killer cells in tumors. The present study showed that [⁶⁸Ga]Ga-DOTA-Siglec-9 can detect B16-FAP tumors and allows monitoring of FAP-IL2v treatment.

P2RX7 Enhances Tumor Control by CD8+ T Cells in Adoptive Cell Therapy

Expression of the purinergic receptor P2RX7 by CD8+ T cells promotes the generation of memory populations following acute infections. However, data suggest that P2RX7 may limit the efficacy of antitumor responses. Herein, we show that P2RX7 is beneficial for optimal melanoma control in a mouse CD8+ T-cell adoptive transfer model. Tumor-specific P2rx7-/- CD8+ T cells exhibited impaired mitochondrial maintenance and function but did not display signs of overt exhaustion early in the antitumor response. However, as the tumor burden increased, the relative frequency of P2RX7-deficient CD8+ T cells declined within the tumor; this correlated with reduced proliferation, increased apoptosis, and mitochondrial dysfunction. Extending these studies, we found that the transient in vitro stimulation of P2RX7 using the ATP analogue BzATP led to enhanced B16 melanoma control by CD8+ T cells. These findings are in keeping with the concept that extracellular ATP (eATP) sensing by P2RX7 on CD8+ T cells is required for their ability to efficiently eliminate tumors by promoting mitochondrial fitness and underscore the potential for P2RX7 stimulation as a novel therapeutic treatment to enhance tumor immunotherapy.

Antitumor Properties of Epitope-Specific Engineered Vaccine in Murine Model of Melanoma

Finding new effective compounds of natural origin for composing anti-tumor vaccines is one of the main goals of antitumor research. Promising anti-cancer agents are the gastropodan hemocyanins-multimeric copper-containing glycoproteins used so far for therapy of different tumors. The properties of hemocyanins isolated from the marine snail Rapana thomasiana (RtH) and the terrestrial snail Helix aspersa (HaH) upon their use as carrier-proteins in conjugated vaccines, containing ganglioside mimotope GD3P4 peptide, were studied in the developed murine melanoma model. Murine melanoma cell line B16F10 was used for solid tumor establishment in C57BL/6 mice using various schemes of therapy. Protein engineering, flow cytometry, and cytotoxicity assays were also performed. The administration of the protein-engineered vaccines RtH-GD3P4 or HaH-GD3P4 under the three different regimens of therapy in the B16F10 murine melanoma model suppressed tumor growth, decreased tumor incidence, and prolonged the survival of treated animals. The immunization of experimental mice induced an infiltration of immunocompetent cells into the tumors and generated cytotoxic tumor-specific T cells in the spleen. The treatment also generates significantly higher levels of tumor-infiltrated M1 macrophages, compared to untreated tumor-bearing control mice. This study demonstrated a promising approach for cancer therapy having potential applications for cancer vaccine research.

Antigen epitope-TLR7/8a conjugate as self-assembled carrier-free nanovaccine for personalized immunotherapy

Epitope-based vaccine is a promising personalized cancer immunotherapy; however, a simple and effective approach for its bulk manufacturing is challenging. Current vaccination strategies complicate the process by introducing unnecessary components such as additional delivery carriers, and assembly units. Herein, a type of toll-like receptor 7/8 agonist-epitope conjugate (termed as TLR7/8a-epitope) has been developed as a self-assembled and carrier-free nano vaccine platform, which effectively introduces the antigen and adjuvant with maximum precision, resulting in significantly enhanced dendritic cells (DCs) activation through the MyD88-dependent TLR signaling pathway. TLR7/8a-epitope nanovaccine can prolong the local retention and increase drainage efficiency into the lymph node, eliciting a significantly higher level of CD8 T-cell immunity than those of conventional vaccine formulations. The immunization with TLR7/8a-epitope nanovaccine in mice can not only resist the invasion of B16 cancer cells, but also produce significant therapeutic effects against established B16 melanoma tumors. Therefore, the TLR7/8a-epitope nanovaccine, developed by the direct chemical conjugation of antigen peptide with immunoadjuvant, has great advantages of clear and leanest compositions, controllable and definite preparation process, and remarkable therapeutic effects, representing a new appraoch for personalized cancer immunotherapy. STATEMENT OF SIGNIFICANCE: Herein, a kind of toll-like receptor 7/8 agonist-epitope conjugate was developed and spontaneously self-assemble into nanostructure in aqueous solution without the use of any additional constituents, which can be termed as unique carrier-free nanovaccine platform, providing effectually the leanest vaccine components with maximally and precisely loading of antigen and adjuvant. Significantly, the nanovaccine augmented the immunogenicity of antigenic peptide by increasing DCs activation through MyD88-mediated TLR signaling pathways and promoting T-cell priming. Moreover, nanovaccines could prolong the local retention and further increase the efficiency of drainage into dLNs, which was contributing to efficient initiation of epitope-specific memory and effector T-cell immune responses, leading to effective prophylactic and therapeutic antitumor effects.

Combination Cancer Immunotherapy with Dendritic Cell Vaccine and Nanoparticles Loaded with Interleukin-15 and Anti-beta-catenin siRNA Significantly Inhibits Cancer Growth and Induces Anti-Tumor Immune Response

PURPOSE

The invention and application of new immunotherapeutic methods can compensate for the inefficiency of conventional cancer treatment approaches, partly due to the inhibitory microenvironment of the tumor. In this study, we tried to inhibit the growth of cancer cells and induce anti-tumor immune responses by silencing the expression of the β-catenin in the tumor microenvironment and transmitting interleukin (IL)-15 cytokine to provide optimal conditions for the dendritic cell (DC) vaccine.

METHODS

For this purpose, we used folic acid (FA)-conjugated SPION-carboxymethyl dextran (CMD) chitosan (C) nanoparticles (NPs) to deliver anti-β-catenin siRNA and IL-15 to cancer cells.

RESULTS

The results showed that the codelivery of β-catenin siRNA and IL-15 significantly reduced the growth of cancer cells and increased the immune response. The treatment also considerably stimulated the performance of the DC vaccine in triggering anti-tumor immunity, which inhibited tumor development and increased survival in mice in two different cancer models.

CONCLUSIONS

These findings suggest that the use of new nanocarriers such as SPION-C-CMD-FA could be an effective way to use as a novel combination therapy consisting of β-catenin siRNA, IL-15, and DC vaccine to treat cancer.

Maximizing response to intratumoral immunotherapy in mice by tuning local retention

Direct injection of therapies into tumors has emerged as an administration route capable of achieving high local drug exposure and strong anti-tumor response. A diverse array of immune agonists ranging in size and target are under development as local immunotherapies. However, due to the relatively recent adoption of intratumoral administration, the pharmacokinetics of locally-injected biologics remains poorly defined, limiting rational design of tumor-localized immunotherapies. Here we define a pharmacokinetic framework for biologics injected intratumorally that can predict tumor exposure and effectiveness. We find empirically and computationally that extending the tumor exposure of locally-injected interleukin-2 by increasing molecular size and/or improving matrix-targeting affinity improves therapeutic efficacy in mice. By tracking the distribution of intratumorally-injected proteins using positron emission tomography, we observe size-dependent enhancement in tumor exposure occurs by slowing the rate of diffusive escape from the tumor and by increasing partitioning to an apparent viscous region of the tumor. In elucidating how molecular weight and matrix binding interplay to determine tumor exposure, our model can aid in the design of intratumoral therapies to exert maximal therapeutic effect.

Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response

Gut bacteria modulate the response to immune checkpoint blockade (ICB) treatment in cancer, but the effect of diet and supplements on this interaction is not well studied. We assessed fecal microbiota profiles, dietary habits, and commercially available probiotic supplement use in melanoma patients and performed parallel preclinical studies. Higher dietary fiber was associated with significantly improved progression-free survival in 128 patients on ICB, with the most pronounced benefit observed in patients with sufficient dietary fiber intake and no probiotic use. Findings were recapitulated in preclinical models, which demonstrated impaired treatment response to anti–programmed cell death 1 (anti–PD-1)–based therapy in mice receiving a low-fiber diet or probiotics, with a lower frequency of interferon-γ–positive cytotoxic T cells in the tumor microenvironment. Together, these data have clinical implications for patients receiving ICB for cancer.

Intratumoral expression of IL-12 from lentiviral or RNA vectors acts synergistically with TLR4 agonist (GLA) to generate anti-tumor immunological memory

Systemic interleukin-12 (IL12) anti-tumor therapy is highly potent but has had limited utility in the clinic due to severe toxicity. Here, we present two IL12-expressing vector platforms, both of which can overcome the deficiencies of previous systemic IL12 therapies: 1) an integrating lentiviral vector, and 2) a self-replicating messenger RNA formulated with polyethyleneimine. Intratumoral administration of either IL12 vector platform resulted in recruitment of immune cells, including effector T cells and dendritic cells, and the complete remission of established tumors in multiple murine models. Furthermore, concurrent intratumoral administration of the synthetic TLR4 agonist glucopyranosyl lipid A formulated in a stable emulsion (GLA-SE) induced systemic memory T cell responses that mediated complete protection against tumor rechallenge in all survivor mice (8/8 rechallenged mice), whereas only 2/6 total rechallenged mice treated with intratrumoral IL12 monotherapy rejected the rechallenge. Taken together, expression of vectorized IL12 in combination with a TLR4 agonist represents a varied approach to broaden the applicability of intratumoral immune therapies of solid tumors.

Monocytes mediate Salmonella Typhimurium-induced tumor growth inhibition in a mouse melanoma model

The use of bacteria as an alternative cancer therapy has been reinvestigated in recent years. SL7207: an auxotrophic Salmonella enterica serovar Typhimurium aroA mutant with immune-stimulatory potential has proven a promising strain for this purpose. Here, we show that systemic administration of SL7207 induces melanoma tumor growth arrest in vivo, with greater survival of the SL7207-treated group compared to control PBS-treated mice. Administration of SL7207 is accompanied by a change in the immune phenotype of the tumor-infiltrating cells toward pro-inflammatory, with expression of the TH 1 cytokines IFN-γ, TNF-α, and IL-12 significantly increased. Interestingly, Ly6C+ MHCII+ monocytes were recruited to the tumors following SL7207 treatment and were pro-inflammatory. Accordingly, the abrogation of these infiltrating monocytes using clodronate liposomes prevented SL7207-induced tumor growth inhibition. These data demonstrate a previously unappreciated role for infiltrating inflammatory monocytes underlying bacterial-mediated tumor growth inhibition. This information highlights a possible novel role for monocytes in controlling tumor growth, contributing to our understanding of the immune responses required for successful immunotherapy of cancer.

Disrupting Roquin-1 interaction with Regnase-1 induces autoimmunity and enhances antitumor responses

Roquin and Regnase-1 proteins bind and post-transcriptionally regulate proinflammatory target messenger RNAs to maintain immune homeostasis. Either the sanroque mutation in Roquin-1 or loss of Regnase-1 cause systemic lupus erythematosus-like phenotypes. Analyzing mice with T cells that lack expression of Roquin-1, its paralog Roquin-2 and Regnase-1 proteins, we detect overlapping or unique phenotypes by comparing individual and combined inactivation. These comprised spontaneous activation, metabolic reprogramming and persistence of T cells leading to autoimmunity. Here, we define an interaction surface in Roquin-1 for binding to Regnase-1 that included the sanroque residue. Mutations in Roquin-1 impairing this interaction and cooperative regulation of targets induced T follicular helper cells, germinal center B cells and autoantibody formation. These mutations also improved the functionality of tumor-specific T cells by promoting their accumulation in the tumor and reducing expression of exhaustion markers. Our data reveal the physical interaction of Roquin-1 with Regnase-1 as a hub to control self-reactivity and effector functions in immune cell therapies.

Pharmacological Activation of cGAS for Cancer Immunotherapy

When compartmentally mislocalized within cells, nucleic acids can be exceptionally immunostimulatory and can even trigger the immune-mediated elimination of cancer. Specifically, the accumulation of double-stranded DNA in the cytosol can efficiently promote antitumor immunity by activating the cGAMP synthase (cGAS) / stimulator of interferon genes (STING) cellular signaling pathway. Targeting this cytosolic DNA sensing pathway with interferon stimulatory DNA (ISD) is therefore an attractive immunotherapeutic strategy for the treatment of cancer. However, the therapeutic activity of ISD is limited by several drug delivery barriers, including susceptibility to deoxyribonuclease degradation, poor cellular uptake, and inefficient cytosolic delivery. Here, we describe the development of a nucleic acid immunotherapeutic, NanoISD, which overcomes critical delivery barriers that limit the activity of ISD and thereby promotes antitumor immunity through the pharmacological activation of cGAS at the forefront of the STING pathway. NanoISD is a nanoparticle formulation that has been engineered to confer deoxyribonuclease resistance, enhance cellular uptake, and promote endosomal escape of ISD into the cytosol, resulting in potent activation of the STING pathway via cGAS. NanoISD mediates the local production of proinflammatory cytokines via STING signaling. Accordingly, the intratumoral administration of NanoISD induces the infiltration of natural killer cells and T lymphocytes into murine tumors. The therapeutic efficacy of NanoISD is demonstrated in preclinical tumor models by attenuated tumor growth, prolonged survival, and an improved response to immune checkpoint blockade therapy.

Photothermal nanofibres enable safe engineering of therapeutic cells

Nanoparticle-sensitized photoporation is an upcoming approach for the intracellular delivery of biologics, combining high efficiency and throughput with excellent cell viability. However, as it relies on close contact between nanoparticles and cells, its translation towards clinical applications is hampered by safety and regulatory concerns. Here we show that light-sensitive iron oxide nanoparticles embedded in biocompatible electrospun nanofibres induce membrane permeabilization by photothermal effects without direct cellular contact with the nanoparticles. The photothermal nanofibres have been successfully used to deliver effector molecules, including CRISPR-Cas9 ribonucleoprotein complexes and short interfering RNA, to adherent and suspension cells, including embryonic stem cells and hard-to-transfect T cells, without affecting cell proliferation or phenotype. In vivo experiments furthermore demonstrated successful tumour regression in mice treated with chimeric antibody receptor T cells in which the expression of programmed cell death protein 1 (PD1) is downregulated after nanofibre photoporation with short interfering RNA to PD1. In conclusion, cell membrane permeabilization with photothermal nanofibres is a promising concept towards the safe and more efficient production of engineered cells for therapeutic applications, including stem cell or adoptive T cell therapy.

Effect of immune modulation on the skeletal muscle mitochondrial exercise response: An exploratory study in mice with cancer

Cancer causes mitochondrial alterations in skeletal muscle, which may progress to muscle wasting and, ultimately, to cancer cachexia. Understanding how exercise adaptations are altered by cancer and cancer treatment is important for the effective design of exercise interventions aimed at improving cancer outcomes. We conducted an exploratory study to investigate how tumor burden and cancer immunotherapy treatment (anti-PD-1) modify the skeletal muscle mitochondrial response to exercise training in mice with transplantable tumors (B16-F10 melanoma and EO771 breast cancer). Mice remained sedentary or were provided with running wheels for ~19 days immediately following tumor implant while receiving no treatment (Untreated), isotype control antibody (IgG2a) or anti-PD-1. Exercise and anti-PD-1 did not alter the growth rate of either tumor type, either alone or in combination therapy. Untreated mice with B16-F10 tumors showed increases in most measured markers of skeletal muscle mitochondrial content following exercise training, as did anti-PD-1-treated mice, suggesting increased mitochondrial content following exercise training in these groups. However, mice with B16-F10 tumors receiving the isotype control antibody did not exhibit increased skeletal muscle mitochondrial content following exercise. In untreated mice with EO771 tumors, only citrate synthase activity and complex IV activity were increased following exercise. In contrast, IgG2a and anti-PD-1-treated groups both showed robust increases in most measured markers following exercise. These results indicate that in mice with B16-F10 tumors, IgG2a administration prevents exercise adaptation of skeletal muscle mitochondria, but adaptation remains intact in mice receiving anti-PD-1. In mice with EO771 tumors, both IgG2a and anti-PD-1-treated mice show robust skeletal muscle mitochondrial exercise responses, while untreated mice do not. Taken together, we postulate that immune modulation may enhance skeletal muscle mitochondrial response to exercise in tumor-bearing mice, and suggest this as an exciting new avenue for future research in exercise oncology.

CpG Oligodeoxynucleotide Developed to Activate Primate Immune Responses Promotes Antitumoral Effects in Combination with a Neoantigen-Based mRNA Cancer Vaccine

PURPOSE

The purpose of our research was to identify and evaluate synthetic phosphorothioate-modified CPG oligodeoxynucleotides (CPG-ODNs) activating innate and adaptive immune responses. Furthermore, combined treatment with CpG and an mRNA cancer vaccine was evaluated in melanoma models as a therapeutic approach.

METHODS

A molecular assay was used to screen new CpG molecules; mouse modeling and pathological analysis were used to confirm the antitumor effect of CpG alone or in combination with an mRNA vaccine. Finally, safety was assessed by monitoring blood biochemistry.

RESULTS

We first screened and identified a new CpG-B class ODN (CpG2018B) that effectively stimulated type II interferons in both mouse plasmacytoid dendritic cells (pDCs) and human peripheral blood mononuclear cells (PBMCs). In addition, CpG2018B promoted cytokine production mainly via toll-like receptor 9 (TLR9) pathways. We further demonstrated that intratumoral (IT) injection of CpG2018B inhibited melanoma growth in syngeneic models and could turn "cold" tumors into "hot" tumors. Then, CpG2018B and an mRNA-based neoantigen cancer vaccine were encapsulated in lipid nanoparticles (LNPs) and intratumorally injected into melanoma mouse models. Interestingly, vaccination with CpG or the mRNA vaccine alone could inhibit tumor growth, while combination of CpG with the mRNA vaccine enhanced the antitumor effect. Finally, we described the long-term safety and tolerability of CpG2018B and mRNA therapy in mice model.

CONCLUSION

We identified a novel CpG-B class ODN to promote the immune response, and CpG combined with mRNA cancer vaccines is an attractive candidate approach for immunostimulatory sequence (ISS)-based therapeutic strategies.

IFNβ Is a Potent Adjuvant for Cancer Vaccination Strategies

Cancer vaccination drives the generation of anti-tumor T cell immunity and can be enhanced by the inclusion of effective immune adjuvants such as type I interferons (IFNs). Whilst type I IFNs have been shown to promote cross-priming of T cells, the role of individual subtypes remains unclear. Here we systematically compared the capacity of distinct type I IFN subtypes to enhance T cell responses to a whole-cell vaccination strategy in a pre-clinical murine model. We show that vaccination in combination with IFNβ induces significantly greater expansion of tumor-specific CD8+ T cells than the other type I IFN subtypes tested. Optimal expansion was dependent on the presence of XCR1+ dendritic cells, CD4+ T cells, and CD40/CD40L signaling. Therapeutically, vaccination with IFNβ delayed tumor progression when compared to vaccination without IFN. When vaccinated in combination with anti-PD-L1 checkpoint blockade therapy (CPB), the inclusion of IFNβ associated with more mice experiencing complete regression and a trend in increased overall survival. This work demonstrates the potent adjuvant activity of IFNβ, highlighting its potential to enhance cancer vaccination strategies alone and in combination with CPB.

MnO2-Based Nanomotors with Active Fenton-like Mn2+ Delivery for Enhanced Chemodynamic Therapy

Chemodynamic therapy (CDT) is an emerging strategy for cancer treatment based on Fenton chemistry, which can convert endogenous H₂O₂ into toxic ·OH. However, the limited endocytosis of passive CDT nanoagents with low penetrating capability resulted in unsatisfactory anticancer efficacy. Herein, we propose the successful fabrication of a self-propelled biodegradable nanomotor system based on hollow MnO₂ nanoparticles with catalytic activity for active Fenton-like Mn²⁺ delivery and enhanced CDT. Compared with the passive counterparts, the significantly improved penetration of nanomotors with enhanced diffusion is demonstrated in both the 2D cell culture system and 3D tumor multicellular spheroids. After the intracellular uptake of nanomotors, toxic Fenton-like Mn²⁺ is massively produced by consuming overexpressed intracellular glutathione (GSH), which has a strong scavenging effect on ·OH, thereby leading to enhanced cancer CDT. The as-developed MnO₂-based nanomotor system with enhanced penetration and endogenous GSH scavenging capability shows much promise as a potential platform for cancer treatment in the near future.

IL7-Fc Enhances the Efficacy of Adoptive T Cell Therapy under Lymphopenic Conditions in a Murine Melanoma Model

Adoptive cell therapy (ACT) using tumor-reactive T cells is a promising form of immunotherapy to specifically target cancer. However, the survival and functional maintenance of adoptively transferred T cells remains a challenge, ultimately limiting their efficacy. Here, we evaluated the use of recombinant IL7-Fc in ACT. In a lymphopenic murine melanoma model, IL7-Fc treatment led to the enhanced inhibition of tumor growth with an increased number of adoptively transferred CD8+ T cells in tumor tissue and tumor-draining lymph nodes. Additionally, IL7-Fc further enhanced anti-tumor responses that were induced by recombinant human IL2 in the same mouse model. In contrast, in an immunocompetent murine melanoma model, IL7-Fc dampened the anti-tumor immunity. Further, IL7-Fc decreased the proliferation of adoptively transferred and immune-activated tumor-reactive CD8+ T cells in immunocompetent mice by inducing the massive expansion of endogenous T cells, thereby limiting the space for adoptively transferred T cells. Our data suggest that IL7-Fc is principally beneficial for enhancing the efficacy of tumor-reactive T-cells in lymphopenic conditions for the ACT.

Synthetic bacterial vesicles combined with tumour extracellular vesicles as cancer immunotherapy

Bacterial outer membrane vesicles (OMV) have gained attention as a promising new cancer vaccine platform for efficiently provoking immune responses. However, OMV induce severe toxicity by activating the innate immune system. In this study, we applied a simple isolation approach to produce artificial OMV that we have named Synthetic Bacterial Vesicles (SyBV) that do not induce a severe toxic response. We also explored the potential of SyBV as an immunotherapy combined with tumour extracellular vesicles to induce anti-tumour immunity. Bacterial SyBV were produced with high yield by a protocol including lysozyme and high pH treatment, resulting in pure vesicles with very few cytosolic components and no RNA or DNA. These SyBV did not cause systemic pro-inflammatory cytokine responses in mice compared to naturally released OMV. However, SyBV and OMV were similarly effective in activation of mouse bone marrow-derived dendritic cells. Co-immunization with SyBV and melanoma extracellular vesicles elicited tumour regression in melanoma-bearing mice through Th-1 type T cell immunity and balanced antibody production. Also, the immunotherapeutic effect of SyBV was synergistically enhanced by anti-PD-1 inhibitor. Moreover, SyBV displayed significantly greater adjuvant activity than other classical adjuvants. Taken together, these results demonstrate a safe and efficient strategy for eliciting specific anti-tumour responses using immunotherapeutic bacterial SyBV.

Type I interferon signaling limits viral vector priming of CD8+ T cells during initiation of vitiligo and melanoma immunotherapy

Vitiligo is an autoimmune skin disease in which epidermal melanocytes are targeted for destruction by CD8+ T cells specific for melanocyte/melanoma-shared antigens. IFNγ is the central cytokine driving disease, but the role of type I IFN in vitiligo remains unclear. We investigated the functional role of type I IFN during vitiligo progression using two different mouse models: one induced with a vaccinia virus (VV) vaccine and one induced with dendritic cells to prime autoimmune T cells. Induction of vitiligo by VV in IFNaR-deficient mice led to the development of severe vitiligo compared with wild-type (WT) mice and was characterized by a significantly enhanced effector CD8+ T-cell response. Severe vitiligo in this model was a result of VV persistence, because exacerbation of disease in IFNaR-deficient mice was not observed when antigen-pulsed dendritic cells were used to induce vitiligo instead of virus. Treatment of B16F10 melanoma-inoculated mice with VV vaccine therapy also induced a significantly enhanced anti-tumor response in IFNaR-deficient mice compared with WT. These results not only help define the pathways responsible for vitiligo progression but also suggest that blockade of type I IFNs following administration of a VV vaccine may provide increased immunogenicity and efficacy for melanoma immunotherapy.

Hyalase-Mediated Cascade Degradation of a Matrix Barrier and Immune Cell Penetration by a Photothermal Microneedle for Efficient Anticancer Therapy

For melanoma with high lethality and metastasis rate, traditional therapy has limited effects; local photothermal therapy (PTT) synergetic with immune therapy for cancer treatment can perhaps improve the situation. However, because of the natural existence of the tumor matrix barrier, the penetration depth of drugs and immune cells often dampens the efficacy of cancer treatment. Herein, we report an innovative synergetic PTT and immune therapy through dissolving microneedles for the codelivery of the hyaluronidase-modified semiconductor polymer nanoparticles containing poly(cyclopentadithiophene-alt-benzothiadiazole) and immune adjuvant polyinosinic-polycytidylic acid (PIC). Benefiting from the dissolution of an extracellular matrix of hyaluronidase, the semiconductor polymer nanoparticles and PIC penetrate the tumor deeply, under synergetic therapy with PTT, activating the immune cells and enhancing the T-cell immune response for inhibition of tumor growth and metastasis. This study provides a promising platform for effective melanoma treatment and a novel strategy to overcome the stromal barrier.

Cytotoxic T lymphocyte-associated protein 4 antibody aggrandizes antitumor immune response of oncolytic virus M1 via targeting regulatory T cells

Oncolytic virotherapies are perceived as remarkable immunotherapies coming into view and represent highly promising cancer treatments, yet to figure out its specific immune responses and underlying barriers remains critical. Albeit recent studies have demonstrated that oncolytic viruses (OVs) could fine tune tumor microenvironment (TME) to elicit tumor suppression mainly due to effective T-cell responses, the interaction between suppressive T cells and OVs is barely undetermined. Herein, we found that regulatory T cells (Treg cells) were increased in the TME following systemic administration of oncolytic virus M1 along with the higher expression of relative cytokines and chemokines in both mouse RM-1 prostatic carcinoma model and mouse B16F10 melanoma model. Besides, Treg cells expressed high levels of CD25 post-M1 treatment, and its suppressive effect on CD8⁺ T cells was also elevated. Depletion of Treg cells in M1-treated groups significantly reinforced antitumor effect of M1. Specific targeting of Treg cells using cytotoxic T lymphocyte-associated protein 4 (CTLA-4) antibody (Ab) in combination with M1 treatment elicited a more profound tumor suppression and longer overall survival time than M1 alone in both tumor models. Moreover, CTLA-4 Ab further aggrandized antitumor immune response elicited by M1, including increased infiltration of CD45⁺ immune cells and CD8⁺ or CD4⁺ T lymphocytes, decreased ratio of Treg cells to CD4⁺ T lymphocytes, the intensified lymphocytotoxicity and elevated secretion of cytotoxic cytokines like interferon-γ, granzyme B and perforin. Therefore, our findings constituted a suggestive evidence that targeting Treg cells in M1-based oncolytic virotherapy may achieve a highly response in clinical cancer research.

Synergistic Activation of Antitumor Immunity by a Particulate Therapeutic Vaccine

Success in anticancer immune therapy relies on stimulation of tumor antigen-specific T lymphocytes and effective infiltration of the T cells into tumor tissue. Here, a therapeutic vaccine that promotes proliferation and tumor infiltration of antigen-specific T cells in both inflamed and noninflamed tumor types is described. The vaccine consists of STING agonist 2'3'-cGAMP, TLR9 ligand CpG, and tumor antigen peptides that are loaded into nanoporous microparticles (μGCVax). μGCVax is effective in inhibiting lung metastatic melanoma, primary breast cancer, and subcutaneous colorectal cancer in their respective murine models, including functional cure of HER2-positive breast cancer. Mechanistically, μGCVax potently stimulates type I interferon expression in dendritic cells, and promotes CD8+ and CD103+ dendritic cell maturation and migration to lymph nodes and other lymphatic tissues. Antitumor responses are dependent on TLR9 and interferon α/β receptor signaling, and to a less extent on STING signaling. These results demonstrate a high potential for μGCVax in mediating antitumor immunity in personalized cancer therapy.

Adjuvant-free peptide vaccine targeting Clec9a on dendritic cells can induce robust antitumor immune response through Syk/IL-21 axis

Dendritic cells (DCs) can process the antigens of cancer vaccine and thus stimulate the CD8+ T cells to recognize and kill the tumor cells that express these antigens. However, lack of promising carriers for presenting the antigens to DCs is one of the main barriers to the development of clinically effective cancer vaccines. Another limitation is the risk of inflammatory side effects induced by the adjuvants. It is still unclear how we can develop ideal adjuvant-free DC vaccine carriers without adjuvants. Methods: A 12-mer peptide carrier (CBP-12) with high affinity for Clec9a expressed on DCs was developed using an in silico rational optimization method. The therapeutic effects of the adjuvant-free vaccine comprising CBP-12 and exogenous or endogenous antigenic peptides were investigated in terms of antigen cross-presentation efficacy, specific cytotoxic T lymphocyte response, and antitumor activity. We also explored the mechanism involved in the antitumor effects of the adjuvant-free CBP-12 vaccine. Finally, we assessed the effects of the CBP-12 conjugated peptide vaccine combined with radiotherapy. Results: Here, we developed CBP-12 as a vaccine carrier that enhanced the uptake and cross-presentation of the antigens, thus inducing strong CD8+ T cell responses and antitumor effects in both anti-PD-1-responsive (B16-OVA) and -resistant (B16) models, even in adjuvant-free conditions. CBP-12 bound to and activated Clec9a, thereby stimulating Clec9a+ DC to product IL-21, but not IL-12 by activating of Syk. The antitumor effects of the CBP-12 conjugated peptide vaccines could be blocked by an IL-21 neutralizing antibody. We also observed the synergistic antitumor effects of the CBP-12 conjugated peptide vaccine combined with radiotherapy. Conclusions: CBP-12 could serve as an adjuvant-free peptide vaccine carrier for cancer immunotherapy.

Combination vaccine based on citrullinated vimentin and enolase peptides induces potent CD4-mediated anti-tumor responses

BACKGROUND

Stress-induced post-translational modifications occur during autophagy and can result in generation of new epitopes and immune recognition. One such modification is the conversion of arginine to citrulline by peptidylarginine deiminase enzymes.

METHODS

We used Human leukocyte antigen (HLA) transgenic mouse models to assess the immunogenicity of citrullinated peptide vaccine by cytokine Enzyme linked immunosorbant spot (ELISpot) assay. Vaccine efficacy was assessed in tumor therapy studies using HLA-matched B16 melanoma and ID8 ovarian models expressing either constitutive or interferon-gamma (IFNγ) inducible Major Histocompatibility Complex (MHC) class II (MHC-II) as represented by most human tumors. To determine the importance of CD4 T cells in tumor therapy, we analyzed the immune cell infiltrate into murine tumors using flow cytometry and performed therapy studies in the presence of CD4 and CD8 T cell depletion. We assessed the T cell repertoire to citrullinated peptides in ovarian cancer patients and healthy donors using flow cytometry.

RESULTS

The combination of citrullinated vimentin and enolase peptides (Modi-1) stimulated strong CD4 T cell responses in mice. Responses resulted in a potent anti-tumor therapy against established tumors and generated immunological memory which protected against tumor rechallenge. Depletion of CD4, but not CD8 T cells, abrogated the primary anti-tumor response as well as the memory response to tumor rechallenge. This was further reinforced by successful tumor regression being associated with an increase in tumor-infiltrating CD4 T cells and a reduction in tumor-associated myeloid suppressor cells. The anti-tumor response also relied on direct CD4 T cell recognition as only tumors expressing MHC-II were rejected. A comparison of different Toll-like receptor (TLR)-stimulating adjuvants showed that Modi-1 induced strong Th1 responses when combined with granulocyte-macrophage colony-stimulating factor (GMCSF), TLR9/TLR4, TLR9, TLR3, TLR1/2 and TLR7 agonists. Direct linkage of the TLR1/2 agonist to the peptides allowed the vaccine dose to be reduced by 10-fold to 100-fold without loss of anti-tumor activity. Furthermore, a CD4 Th1 response to the citrullinated peptides was seen in ovarian cancer patients.

CONCLUSIONS

Modi-1 citrullinated peptide vaccine induces potent CD4-mediated anti-tumor responses in mouse models and a CD4 T cell repertoire is present in ovarian cancer patients to the citrullinated peptides suggesting that Modi-1 could be an effective vaccine for ovarian cancer patients.

CD36-mediated ferroptosis dampens intratumoral CD8+ T cell effector function and impairs their antitumor ability

Understanding the mechanisms underlying how T cells become dysfunctional in a tumor microenvironment (TME) will greatly benefit cancer immunotherapy. We found that increased CD36 expression in tumor-infiltrating CD8⁺ T cells, which was induced by TME cholesterol, was associated with tumor progression and poor survival in human and murine cancers. Genetic ablation of Cd36 in effector CD8⁺ T cells exhibited increased cytotoxic cytokine production and enhanced tumor eradication. CD36 mediated uptake of fatty acids by tumor-infiltrating CD8⁺ T cells in TME, induced lipid peroxidation and ferroptosis, and led to reduced cytotoxic cytokine production and impaired antitumor ability. Blocking CD36 or inhibiting ferroptosis in CD8⁺ T cells effectively restored their antitumor activity and, more importantly, possessed greater antitumor efficacy in combination with anti-PD-1 antibodies. This study reveals a new mechanism of CD36 regulating the function of CD8⁺ effector T cells and therapeutic potential of targeting CD36 or inhibiting ferroptosis to restore T cell function.

DNGR-1 limits Flt3L-mediated antitumor immunity by restraining tumor-infiltrating type I conventional dendritic cells

BACKGROUND

Conventional type 1 dendritic cells (cDC1s) are central to antitumor immunity and their presence in the tumor microenvironment associates with improved outcomes in patients with cancer. DNGR-1 (CLEC9A) is a dead cell-sensing receptor highly restricted to cDC1s. DNGR-1 has been involved in both cross-presentation of dead cell-associated antigens and processes of disease tolerance, but its role in antitumor immunity has not been clarified yet.

METHODS

B16 and MC38 tumor cell lines were inoculated subcutaneously into wild-type (WT) and DNGR-1-deficient mice. To overexpress Flt3L systemically, we performed gene therapy through the hydrodynamic injection of an Flt3L-encoding plasmid. To characterize the immune response, we performed flow cytometry and RNA-Seq of tumor-infiltrating cDC1s.

RESULTS

Here, we found that cross-presentation of tumor antigens in the steady state was DNGR-1-independent. However, on Flt3L systemic overexpression, tumor growth was delayed in DNGR-1-deficient mice compared with WT mice. Of note, this protection was recapitulated by anti-DNGR-1-blocking antibodies in mice following Flt3L gene therapy. This improved antitumor immunity was associated with Batf3-dependent enhanced accumulation of CD8+ T cells and cDC1s within tumors. Mechanistically, the deficiency in DNGR-1 boosted an Flt3L-induced specific inflammatory gene signature in cDC1s, including Ccl5 expression. Indeed, the increased infiltration of cDC1s within tumors and their protective effect rely on CCL5/CCR5 chemoattraction. Moreover, FLT3LG and CCL5 or CCR5 gene expression signatures correlate with an enhanced cDC1 signature and a favorable overall survival in patients with cancer. Notably, cyclophosphamide elevated serum Flt3L levels and, in combination with the absence of DNGR-1, synergized against tumor growth.

CONCLUSION

DNGR-1 limits the accumulation of tumor-infiltrating cDC1s promoted by Flt3L. Thus, DNGR-1 blockade may improve antitumor immunity in tumor therapy settings associated to high Flt3L expression.

In situ delivery of iPSC-derived dendritic cells with local radiotherapy generates systemic antitumor immunity and potentiates PD-L1 blockade in preclinical poorly immunogenic tumor models

BACKGROUND

Dendritic cells (DCs) are a promising therapeutic target in cancer immunotherapy given their ability to prime antigen-specific T cells, and initiate antitumor immune response. A major obstacle for DC-based immunotherapy is the difficulty to obtain a sufficient number of functional DCs. Theoretically, this limitation can be overcome by using induced pluripotent stem cells (iPSCs); however, therapeutic strategies to engage iPSC-derived DCs (iPSC-DCs) into cancer immunotherapy remain to be elucidated. Accumulating evidence showing that induction of tumor-residing DCs enhances immunomodulatory effect of radiotherapy (RT) prompted us to investigate antitumor efficacy of combining intratumoral administration of iPSC-DCs with local RT.

METHODS

Mouse iPSCs were differentiated to iPSC-DCs on OP9 stromal cells expressing the notch ligand delta-like 1 in the presence of granulocyte macrophage colony-stimulating factor. Phenotype and the capacities of iPSC-DCs to traffic tumor-draining lymph nodes (TdLNs) and prime antigen-specific T cells were evaluated by flow cytometry and imaging flow cytometry. Antitumor efficacy of intratumoral injection of iPSC-DCs and RT was tested in syngeneic orthotopic mouse tumor models resistant to anti-PD-1 ligand 1 (PD-L1) therapy.

RESULTS

Mouse iPSC-DCs phenotypically resembled conventional type 2 DCs, and had a capacity to promote activation, proliferation and effector differentiation of antigen-specific CD8+ T cells in the presence of the cognate antigen in vitro. Combination of in situ administration of iPSC-DCs and RT facilitated the priming of tumor-specific CD8+ T cells, and synergistically delayed the growth of not only the treated tumor but also the distant non-irradiated tumors. Mechanistically, RT enhanced trafficking of intratumorally injected iPSC-DCs to the TdLN, upregulated CD40 expression, and increased the frequency of DC/CD8+ T cell aggregates. Phenotypic analysis of tumor-infiltrating CD8+ T cells and myeloid cells revealed an increase of stem-like Slamf6+ TIM3- CD8+ T cells and PD-L1 expression in tumor-associated macrophages and DCs. Consequently, combined therapy rendered poorly immunogenic tumors responsive to anti-PD-L1 therapy along with the development of tumor-specific immunological memory.

CONCLUSIONS

Our findings illustrate the translational potential of iPSC-DCs, and identify the therapeutic efficacy of a combinatorial platform to engage them for overcoming resistance to anti-PD-L1 therapy in poorly immunogenic tumors.

Inhibiting the MNK1/2-eIF4E axis impairs melanoma phenotype switching and potentiates antitumor immune responses

Melanomas commonly undergo a phenotype switch, from a proliferative to an invasive state. Such tumor cell plasticity contributes to immunotherapy resistance; however, the mechanisms are not completely understood and thus are therapeutically unexploited. Using melanoma mouse models, we demonstrated that blocking the MNK1/2-eIF4E axis inhibited melanoma phenotype switching and sensitized melanoma to anti-PD-1 immunotherapy. We showed that phospho-eIF4E-deficient murine melanomas expressed high levels of melanocytic antigens, with similar results verified in patient melanomas. Mechanistically, we identified phospho-eIF4E-mediated translational control of NGFR, a critical effector of phenotype switching. Genetic ablation of phospho-eIF4E reprogrammed the immunosuppressive microenvironment, exemplified by lowered production of inflammatory factors, decreased PD-L1 expression on dendritic cells and myeloid-derived suppressor cells, and increased CD8+ T cell infiltrates. Finally, dual blockade of the MNK1/2-eIF4E axis and the PD-1/PD-L1 immune checkpoint demonstrated efficacy in multiple melanoma models regardless of their genomic classification. An increase in the presence of intratumoral stem-like TCF1+PD-1+CD8+ T cells, a characteristic essential for durable antitumor immunity, was detected in mice given a MNK1/2 inhibitor and anti-PD-1 therapy. Using MNK1/2 inhibitors to repress phospho-eIF4E thus offers a strategy to inhibit melanoma plasticity and improve response to anti-PD-1 immunotherapy.

IL-1α Mediates Innate and Acquired Resistance to Immunotherapy in Melanoma

Inflammation has long been associated with cancer initiation and progression; however, how inflammation causes immune suppression in the tumor microenvironment and resistance to immunotherapy is not well understood. In this study, we show that both innate proinflammatory cytokine IL-1α and immunotherapy-induced IL-1α make melanoma resistant to immunotherapy. In a mouse melanoma model, we found that tumor size was inversely correlated with response to immunotherapy. Large tumors had higher levels of IL-1α, Th2 cytokines, polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), and regulatory T cells but lower levels of IL-12, Th1 cytokines, and activated T cells. We found that therapy with adenovirus-encoded CD40L (rAd.CD40L) increased tumor levels of IL-1α and PMN-MDSCs. Blocking the IL-1 signaling pathway significantly decreased rAd.CD40L-induced PMN-MDSCs and their associated PD-L1 expression in the tumor microenvironment and enhanced tumor-specific immunity. Similarly, blocking the IL-1 signaling pathway improved the antimelanoma activity of anti-PD-L1 Ab therapy. Our study suggests that blocking the IL-1α signaling pathway may increase the efficacy of immunotherapies against melanoma.

A DNA nanodevice-based vaccine for cancer immunotherapy

A major challenge in cancer vaccine therapy is the efficient delivery of antigens and adjuvants to stimulate a controlled yet robust tumour-specific T-cell response. Here, we describe a structurally well defined DNA nanodevice vaccine generated by precisely assembling two types of molecular adjuvants and an antigen peptide within the inner cavity of a tubular DNA nanostructure that can be activated in the subcellular environment to trigger T-cell activation and cancer cytotoxicity. The integration of low pH-responsive DNA 'locking strands' outside the nanostructures enables the opening of the vaccine in lysosomes in antigen-presenting cells, exposing adjuvants and antigens to activate a strong immune response. The DNA nanodevice vaccine elicited a potent antigen-specific T-cell response, with subsequent tumour regression in mouse cancer models. Nanodevice vaccination generated long-term T-cell responses that potently protected the mice against tumour rechallenge.

Galectin-9 interacts with PD-1 and TIM-3 to regulate T cell death and is a target for cancer immunotherapy

The two T cell inhibitory receptors PD-1 and TIM-3 are co-expressed during exhausted T cell differentiation, and recent evidence suggests that their crosstalk regulates T cell exhaustion and immunotherapy efficacy; however, the molecular mechanism is unclear. Here we show that PD-1 contributes to the persistence of PD-1+TIM-3+ T cells by binding to the TIM-3 ligand galectin-9 (Gal-9) and attenuates Gal-9/TIM-3-induced cell death. Anti-Gal-9 therapy selectively expands intratumoral TIM-3+ cytotoxic CD8 T cells and immunosuppressive regulatory T cells (Treg cells). The combination of anti-Gal-9 and an agonistic antibody to the co-stimulatory receptor GITR (glucocorticoid-induced tumor necrosis factor receptor-related protein) that depletes Treg cells induces synergistic antitumor activity. Gal-9 expression and secretion are promoted by interferon β and γ, and high Gal-9 expression correlates with poor prognosis in multiple human cancers. Our work uncovers a function for PD-1 in exhausted T cell survival and suggests Gal-9 as a promising target for immunotherapy.

Therapeutic depletion of CCR8+ tumor-infiltrating regulatory T cells elicits antitumor immunity and synergizes with anti-PD-1 therapy

BACKGROUND

Modulation and depletion strategies of regulatory T cells (Tregs) constitute valid approaches in antitumor immunotherapy but suffer from severe adverse effects due to their lack of selectivity for the tumor-infiltrating (ti-)Treg population, indicating the need for a ti-Treg specific biomarker.

METHODS

We employed single-cell RNA-sequencing in a mouse model of non-small cell lung carcinoma (NSCLC) to obtain a comprehensive overview of the tumor-infiltrating T-cell compartment, with a focus on ti-Treg subpopulations. These findings were validated by flow cytometric analysis of both mouse (LLC-OVA, MC38 and B16-OVA) and human (NSCLC and melanoma) tumor samples. We generated two CCR8-specific nanobodies (Nbs) that recognize distinct epitopes on the CCR8 extracellular domain. These Nbs were formulated as tetravalent Nb-Fc fusion proteins for optimal CCR8 binding and blocking, containing either an antibody-dependent cell-mediated cytotoxicity (ADCC)-deficient or an ADCC-prone Fc region. The therapeutic use of these Nb-Fc fusion proteins was evaluated, either as monotherapy or as combination therapy with anti-programmed cell death protein-1 (anti-PD-1), in both the LLC-OVA and MC38 mouse models.

RESULTS

We were able to discern two ti-Treg populations, one of which is characterized by the unique expression of Ccr8 in conjunction with Treg activation markers. Ccr8 is also expressed by dysfunctional CD4+ and CD8+ T cells, but the CCR8 protein was only prominent on the highly activated and strongly T-cell suppressive ti-Treg subpopulation of mouse and human tumors, with no major CCR8-positivity found on peripheral Tregs. CCR8 expression resulted from TCR-mediated Treg triggering in an NF-κB-dependent fashion, but was not essential for the recruitment, activation nor suppressive capacity of these cells. While treatment of tumor-bearing mice with a blocking ADCC-deficient Nb-Fc did not influence tumor growth, ADCC-prone Nb-Fc elicited antitumor immunity and reduced tumor growth in synergy with anti-PD-1 therapy. Importantly, ADCC-prone Nb-Fc specifically depleted ti-Tregs in a natural killer (NK) cell-dependent fashion without affecting peripheral Tregs.

CONCLUSIONS

Collectively, our findings highlight the efficacy and safety of targeting CCR8 for the depletion of tumor-promoting ti-Tregs in combination with anti-PD-1 therapy.

Distinct metabolic programs established in the thymus control effector functions of γδ T cell subsets in tumor microenvironments

Metabolic programming controls immune cell lineages and functions, but little is known about γδ T cell metabolism. Here, we found that γδ T cell subsets making either interferon-γ (IFN-γ) or interleukin (IL)-17 have intrinsically distinct metabolic requirements. Whereas IFN-γ+ γδ T cells were almost exclusively dependent on glycolysis, IL-17+ γδ T cells strongly engaged oxidative metabolism, with increased mitochondrial mass and activity. These distinct metabolic signatures were surprisingly imprinted early during thymic development and were stably maintained in the periphery and within tumors. Moreover, pro-tumoral IL-17+ γδ T cells selectively showed high lipid uptake and intracellular lipid storage and were expanded in obesity and in tumors of obese mice. Conversely, glucose supplementation enhanced the antitumor functions of IFN-γ+ γδ T cells and reduced tumor growth upon adoptive transfer. These findings have important implications for the differentiation of effector γδ T cells and their manipulation in cancer immunotherapy.

NF-κB-inducing kinase maintains T cell metabolic fitness in antitumor immunity

Metabolic reprograming toward aerobic glycolysis is a pivotal mechanism shaping immune responses. Here we show that deficiency in NF-κB-inducing kinase (NIK) impairs glycolysis induction, rendering CD8+ effector T cells hypofunctional in the tumor microenvironment. Conversely, ectopic expression of NIK promotes CD8+ T cell metabolism and effector function, thereby profoundly enhancing antitumor immunity and improving the efficacy of T cell adoptive therapy. NIK regulates T cell metabolism via a NF-κB-independent mechanism that involves stabilization of hexokinase 2 (HK2), a rate-limiting enzyme of the glycolytic pathway. NIK prevents autophagic degradation of HK2 through controlling cellular reactive oxygen species levels, which in turn involves modulation of glucose-6-phosphate dehydrogenase (G6PD), an enzyme that mediates production of the antioxidant NADPH. We show that the G6PD-NADPH redox system is important for HK2 stability and metabolism in activated T cells. These findings establish NIK as a pivotal regulator of T cell metabolism and highlight a post-translational mechanism of metabolic regulation.

Potentiating the Antitumor Activity of Cytotoxic T Cells via the Transmembrane Domain of IGSF4 That Increases TCR Avidity

A robust T-cell response is an important component of sustained antitumor immunity. In this respect, the avidity of TCR in the antigen-targeting of tumors is crucial for the quality of the T-cell response. This study reports that the transmembrane (TM) domain of immunoglobulin superfamily member 4 (IGSF4) binds to the TM of the CD3 ζ-chain through an interaction between His177 and Asp36, which results in IGSF4-CD3 ζ dimers. IGSF4 also forms homo-dimers through the GxxVA motif in the TM domain, thereby constituting large TCR clusters. Overexpression of IGSF4 lacking the extracellular (IG4ΔEXT) domain potentiates the OTI CD8+ T cells to release IFN-γ and TNF-α and to kill OVA+-B16F10 melanoma cells. In animal models, IG4ΔEXT significantly reduces B16F10 tumor metastasis as well as tumor growth. Collectively, the results indicate that the TM domain of IGSF4 can regulate TCR avidity, and they further demonstrate that TCR avidity regulation is critical for improving the antitumor activity of cytotoxic T cells.

Detection of Immunogenic Cell Death in Tumor Vaccination Mouse Model

Immunogenic cell death (ICD) is a form of regulated cell death that is capable of eliciting an immune response. In cancer, tumor cells undergoing ICD are known to emit damage associated molecular patterns (DAMPs) that are capable of recruiting and activating antigen presenting cells (APCs), which ultimately lead to the activation of an antitumor immune response. Surface translocation of intracellular chaperones such as calreticulin, release of TLR agonists such as high mobility box 1, and the secretion of type I IFN are some of the hallmark features seen in tumors succumbing to ICD. While detection of these molecules is suggestive of ICD induction, which alone does not certify that the treatment is an ICD inducer, an in vivo vaccination assay using injured tumor cells remains to be the gold standard method to functionally verify ICD. This chapter will discuss the necessary steps required to conduct an in vivo vaccination assay, focusing on the preparation of vaccine using treated tumor cells, and how these cells are then utilized in the animal model.

Boiling histotripsy and in-situ CD40 stimulation improve the checkpoint blockade therapy of poorly immunogenic tumors

Background: Advanced stage cancers with a suppressive tumor microenvironment (TME) are often refractory to immune checkpoint inhibitor (ICI) therapy. Recent studies have shown that focused ultrasound (FUS) TME-modulation can synergize ICI therapy, but enhancing survival outcomes in poorly immunogenic tumors remains challenging. Here, we investigated the role of focused ultrasound based boiling histotripsy (HT) and in-situ anti-CD40 agonist antibody (αCD40) combinatorial therapy in enhancing therapeutic efficacy against ICI refractory murine melanoma. Methods: Unilateral and bilateral large (~330-400 mm3) poorly immunogenic B16F10 melanoma tumors were established in the flank regions of mice. Tumors were exposed to single local HT followed by an in-situ administration of αCD40 (HT+ αCD40: HT40). Inflammatory signatures post treatment were assessed using pan-cancer immune profiling and flow cytometry. The ability of HT40 ± ICI to enhance local and systemic effects was determined by immunological characterization of the harvested tissues, and by tumor growth delay of local and distant untreated tumors 4-6 weeks post treatment. Results: Immune profiling revealed that HT40 upregulated a variety of inflammatory markers in the tumors. Immunologically, HT40 treated tumors showed an increased population of granzyme B+ expressing functional CD8+ T cells (~4-fold) as well as an increased M1 to M2 macrophage ratio (~2-3-fold) and CD8+ T: regulatory T cell ratio (~5-fold) compared to the untreated control. Systemically, the proliferation rates of the melanoma-specific memory T cell population were significantly enhanced by HT40 treatment. Finally, the combination of HT40 and ICI therapy (anti-CTLA-4 and anti-PD-L1) caused superior inhibition of distant untreated tumors, and prolonged survival rates compared to the control. Conclusions: Data suggest that HT40 reprograms immunologically cold tumors and sensitizes them to ICI therapy. This approach may be clinically useful for treating advanced stage melanoma cancers.