Immunogenicity of murine solid tumor models as a defining feature of in vivo behavior and response to immunotherapy

Timely administration of drug combination improves chemoimmunotherapy of an immune-cold tumor

An immunoactive complex consisting of a polyethyleneimine derivative (2E'), paclitaxel (PTX), and cyclic dinucleotide (CDN) was developed for chemoimmunotherapy of solid tumors. Each component uniquely contributes to stimulating innate immune response to tumors: 2E' carries PTX and CDN while stimulating antigen-presenting cells, PTX induces immunogenic cell death, and CDN activates the STING pathway. A single intratumoral injection of 2E'/PTX/CDN inhibited the growth of MOC1 oral squamous cell carcinoma and KPCY (2838c3) pancreatic tumors, achieving complete tumor regression in 80-100 % of mice. However, 2E'/PTX/CDN showed limited therapeutic efficacy with immune-cold B16F10 melanoma, accompanied by the increase of innate immune cells in the tumor draining lymph nodes peaking on day 5 post-administration and subsiding thereafter. The addition of a complex of 2E' and siRNA targeting PD-L1 (siPD-L1) at an optimal 5-d interval improved the response in B16F10 melanoma, resulting in tumor-free survival in 50 % of mice and rejection of live tumor rechallenge in 67 % of surviving animals. Consistent with the function of each component, the timed combination of 2E'/PTX/CDN and 2E'/siPD-L1 increased the fractions of mature dendritic cells and M1 macrophages, prevented the increase of regulatory T cells in tumor-draining lymph nodes, and increased melanoma antigen-specific CD8+ T cells in the spleen. These results demonstrate the effectiveness of the 2E'/PTX/CDN complex in the chemoimmunotherapy of solid tumors and highlight the significance of timely intervention to sustain the immunoactive phenotype in its application to immune-cold tumors.

Potentiation of immune checkpoint blockade with a pH-sensitizer as monitored in two pre-clinical tumor models with acidoCEST MRI

BACKGROUND

Tumor acidosis causes resistance to immune checkpoint blockade (ICB). We hypothesized that a "pH-sensitizer" can increase tumor extracellular pH (pHe) and improve tumor control following ICB. We also hypothesized that pHe measured with acidoCEST MRI can predict improved tumor control with ICB.

METHODS

We tested the effects of pH-sensitizers on proton efflux rate (PER), cytotoxicity, T cell activation, tumor immunogenicity, tumor growth and survival using 4T1 and B16-F10 tumor cells. We measured in vivo tumor pHe of 4T1 and B16-F10 models with acidoCEST MRI.

RESULTS

Among the pH-sensitizers tested, someprazole caused the greatest reduction in PER without exhibiting cytotoxicity or reducing T cell activation. Esomeprazole improved 4T1 tumor control with ICB administered one day after the pH-sensitizer. Tumor pHe positively correlated with TCF-1 + CD4 effector and CD8 T cell intratumoral frequencies and predicted improved 4T1 tumor control with ICB. For comparison, esomeprazole had a mild effect on B16-F10 tumor pHe, and worsened tumor control with ICB and increased intratumoral myeloid and dendritic cell (DC) frequencies.

CONCLUSIONS

A pH-sensitizer can improve tumor control with ICB, and acidoCEST MRI can be used to measure pHe and predict tumor control, but only in the 4T1 model and not the B16-F10 model.

Gut commensal Bifidobacterium-derived extracellular vesicles modulate the therapeutic effects of anti-PD-1 in lung cancer

Lung cancer is the leading cause of cancer-related deaths worldwide. Although immunotherapy such as anti-programmed death-1 and its ligand 1 (PD-1/L1) is a standard treatment for advanced non-small cell lung cancer (NSCLC), many patients do not derive benefit directly. Several studies have elucidated new strategies to improve the antitumor immune response through gut microbiota modulation. However, it remains largely debatable regarding how gut microbiota remotely affect lung cancer microenvironment and subsequently modulate immunotherapy response. Here we show that commensal Bifidobacterium-derived extracellular vesicles (Bif.BEVs) can modulate the therapeutic effect of anti-PD-1 therapy in NSCLC. These Bif.BEVs are up-taken by lung cancer cells predominantly via dynamin-dependent endocytosis and upregulate PD-L1 expression through TLR4-NF-κB pathway. They also efficiently penetrate murine intestinal and patient-derived lung cancer organoids. Oral gavage of these Bif.BEVs result in their accumulation in tumors in mice. Using a syngeneic mouse model, Bif.BEVs are found to synergize the anti-tumor effect of anti-PD-1 via modulation of key cytokines, immune response and oncogenic pathways, and increase in tumor-infiltrating CD8+ T cells. Our study therefore identifies a link between Bif.BEVs and the tumor microenvironment, providing an alternative mechanism to explain how gut microbiota can influence immunotherapy response, particularly in tumors located anatomically distant from the gut.

Discovery of HM-279, a Potent Inhibitor of ALK5 for Improving Therapeutic Efficacy of Cancer Immunotherapy

Activin receptor-like kinase 5 (ALK5) is a type I receptor serine/threonine kinase and responsible for the TGF-β signaling pathway. ALK5 is thought to be a key player in the tumor microenvironment to promote tumor progression by affecting the anticancer immunity. Therefore, ALK5 is an attractive drug target for modulating TGF-β signaling pathways to improve the therapeutic efficacy of cancer immunotherapy. We report the optimization of a series of thiazole analogues starting from lead compound 6, focusing on improving off-target selectivity. Compound 19f (HM-279) was identified as a potent ALK5 inhibitor with an acceptable off-target selectivity and favorable ADME/PK properties. Oral administration of HM-279 demonstrated antitumor activity in a CT26.WT colon carcinoma syngeneic mouse model as a single agent and in combination with the anti-PD-1 antibody through CD8+ T cell immunity.

Antitumor Efficacy of Interleukin 12-Transfected Mesenchymal Stem Cells in B16-F10 Mouse Melanoma Tumor Model

Background/Objectives: Mesenchymal stromal cells (MSCs) hold the potential for tumor-targeted gene delivery due to their ex vivo manipulability, low immunogenicity, scalability, and inherent tumor-homing properties. Despite the widespread use of viral vectors for MSC genetic modification, safety concerns have prompted interest in non-viral alternatives, such as gene electrotransfer (GET). This study aimed to optimize GET parameters for MSCs transfection, assess MSCs biodistribution after in vivo administration, and evaluate the therapeutic potential of interleukin-12 (IL-12)-modified MSCs in a mouse melanoma model. Methods: Human MSCs were isolated from umbilical cords under ethically approved protocols. GET protocols were optimized using a fluorescent reporter gene to evaluate transfection efficiency and cell viability. MSC biodistribution was examined following intravenous and intratumoral injections in murine tumor models using luminescent reporter gene. The therapeutic efficacy of IL-12-modified MSCs was assessed in a syngeneic mouse melanoma model. Results: Optimized GET protocols achieved a transfection efficiency of 80% and a cell viability of 90%. Biodistribution studies demonstrated effective tumor retention of MSCs following intratumoral injections, whereas intravenous administration resulted in predominant cell localization in the lungs. IL-12-modified MSCs injected intratumorally significantly inhibited tumor growth, delaying tumor progression by five days compared to controls. Conclusions: Optimized GET conditions enabled high-efficiency, high-viability MSCs transfection, facilitating their use as effective vehicles for localized cytokine delivery. While the innate tumor tropism of MSCs was not conclusively demonstrated, the study highlights the potential of GET as a reliable non-viral gene delivery platform and underscores the therapeutic promise of IL-12-modified MSCs in tumor-targeted gene therapy.

Electrochemotherapy with bleomycin, oxaliplatin, or cisplatin in mouse tumor models, from tumor ablation to in situ vaccination

Introduction

In addition to its direct cytotoxic effects, ablative therapies as electrochemotherapy (ECT) can elicit indirect antitumor effects by triggering immune system responses. Here, we comprehensively analyzed this dual effectiveness of intratumoral ECT with chemotherapeutic drugs bleomycin (BLM), oxaliplatin (OXA), and cisplatin (CDDP). Our aim was to determine if ECT can act as in situ vaccination and thereby induce an abscopal effect. By evaluating ECT's potential for in situ vaccination, our goal was to pave the way for future advancements for its combination with emerging (immuno)therapies, leading to enhanced responses and outcomes.

Methods

We employed two mouse tumor models, the immunologically cold B16F10 melanoma and 4T1 mammary carcinoma, to explore both local and systemic (i.e., abscopal) antitumor effects following equieffective intratumoral ECT with BLM, OXA, and CDDP. Through histological analyses and the use of immunodeficient and metastatic (for abscopal effect) mouse models, we identified and compared both the cytotoxic and immunological components of ECT's antitumor efficiency, such as immunologically recognizable cell deaths (immunogenic cell death and necrosis) and immune infiltrate (CD11+, CD4+, CD8+, GrB+).

Results

Differences in immunological involvement after equieffective intratumoral ECT were highlighted by variable kinetics of immunologically recognizable cell deaths and immune infiltrate across the studied tumor models. Particularly, the 4T1 tumor model exhibited a more pronounced involvement of the immune component compared to the B16F10 tumor model. Variances in the antitumor (immune) response were also detected based on the chemotherapeutic drug used in ECT. Collectively, ECT demonstrated effectiveness in inducing in situ vaccination in both tumor models; however, an abscopal effect was observed in the 4T1 tumor model only.

Conclusions

This is the first preclinical study systematically comparing the immune involvement in intratumoral ECT's efficiency using three distinct chemotherapeutic drugs in mouse tumor models. The demonstrated variability in immune response to ECT across different tumor models and chemotherapeutic drugs provides a basis for future investigations aimed at enhancing the effectiveness of combined treatments.

Chimeric antigen receptor macrophages (CAR-M) sensitize HER2+ solid tumors to PD1 blockade in pre-clinical models

We previously developed human CAR macrophages (CAR-M) and demonstrated redirection of macrophage anti-tumor function leading to tumor control in immunodeficient xenograft models. Here, we develop clinically relevant fully immunocompetent syngeneic models to evaluate the potential for CAR-M to remodel the tumor microenvironment (TME), induce T cell anti-tumor immunity, and sensitize solid tumors to PD1/PDL1 checkpoint inhibition. In vivo, anti-HER2 CAR-M significantly reduce tumor burden, prolong survival, remodel the TME, increase intratumoral T cell and natural killer (NK) cell infiltration, and induce antigen spreading. CAR-M therapy protects against antigen-negative relapses in a T cell dependent fashion, confirming long-term anti-tumor immunity. In HER2+ solid tumors with limited sensitivity to anti-PD1 (aPD1) monotherapy, the combination of CAR-M and aPD1 significantly improves tumor growth control, survival, and remodeling of the TME in pre-clinical models. These results demonstrate synergy between CAR-M and T cell checkpoint blockade and provide a strategy to potentially enhance response to aPD1 therapy for patients with non-responsive tumors.

Deleting Trim33 in Myeloid Cells Improves the Efficiency of Radiotherapy through an IFNβ-Dependent Antitumor Immune Response

Radiotherapy (RT) triggers an immune response that contributes to antitumor effects. Induction of IFNβ is a key event in this immunogenicity of RT. We have previously shown that TRIM33, a chromatin reader, restrains IFNβ expression in Toll-like receptor-activated myeloid cells. In this study, we explored whether deleting Trim33 in myeloid cells might improve the radio-induced immune response and subsequent efficiency of RT. We first established that Trim33-/- bone marrow-derived macrophages showed increased expression of IFNβ in response to direct irradiation, or to treatment with irradiated cancer cells, further supporting our hypothesis. We then tested the efficiency of a single-dose RT in three subcutaneous tumor models and one orthotopic tumor model. In all models, myeloid deletion of Trim33 led to a significantly improved response after RT, leading to a complete and durable response in most of the treated mice bearing orthotopic oral tumors. This effect required the involvement of the type I IFN pathway and the presence of CD8+ T lymphocytes but not NK cells. In addition, cured mice were capable of rejecting a secondary tumor challenge, demonstrating an in situ vaccination effect. We conclude that deleting Trim33 in myeloid cells improves RT efficiency, through a mechanism involving the type I IFN pathway and the immune response. Our work suggests that myeloid Trim33 is a host factor affecting the tumor response to RT, thus representing a new potential therapeutic target for modifying RT responses.

NF-κB associated markers of prognosis in early and metastatic triple negative breast cancer

BACKGROUND

Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer. While PD-1 based immunotherapies overall have led to improved treatment outcomes for this disease, a diverse response to frontline chemotherapy and immunotherapy still exist in TNBC, highlighting the need for more robust prognostic markers.

METHODS

Tumor-intrinsic immunotranscriptomics, serum cytokine profiling, and tumor burden studies were conducted in two syngeneic mouse models to assess differential effects in both the early-stage and metastatic setting. Bioinformatic analyses of both early and metastatic TNBC patient data were performed to assess if identified NF-κB-associated factors are associated with improved patient clinical outcomes.

RESULTS

NF-κB signaling driven by lymphotoxin beta expression is associated with tumor regression in TNBC mouse models. Furthermore, lymphotoxin beta expression in patient TNBC cohorts is prognostic of improved survival outcomes.

CONCLUSIONS

This study highlights the potential role for NF-κB-associated factors, specifically lymphotoxin beta to be used as prognostic markers in TNBC, which could ultimately provide insight for improved targeted treatment approaches in the clinic.

In Vivo Bioluminescence Imaging of Tumor Progression in the Lewis Lung Carcinoma Orthotopic Mouse Model: A Comparison Between the Tail Vein Injection and Intranasal Instillation Methods

Metastasis remains a leading cause of cancer-related mortality, yet its study has been constrained by the lack of reliable animal models that faithfully replicate this complex process. Syngeneic models for studying lung cancer metastasis are limited, with the Lewis lung carcinoma (LLC) model being the most commonly employed. The conventional LLC orthotopic model involves injecting LLC cells intravenously (i.v.) via the tail vein into syngeneic C57BL/6 mice. However, this model has significant drawbacks, such as tumor development in multiple anatomical sites, incomplete lung tumor penetrance, and challenges in monitoring lung tumor growth. This article highlights the advantages of using luciferase-expressing LLC cells combined with bioluminescence imaging (BLI) to quantify tumor progression in live animals. We demonstrate that both white- and black-furred C57BL/6 mice can be used for BLI. Finally, we propose that intranasal (i.n.) instillation of LLC cells offers a valuable alternative to the traditional i.v. tail vein injection method, particularly for its simplicity and improved reproducibility. Although the LLC i.n. model does not recapitulate the metastasis process via the blood vascular route, it is an effective model for studying tumor seeding within the lungs and is particularly useful for analyzing the impact of the lung microenvironment on tumor initiation and progression. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Lewis lung carcinoma intravenous injection method Support Protocol: In vivo bioluminescence imaging Basic Protocol 2: Lewis lung carcinoma intranasal instillation method.

Mimicking and analyzing the tumor microenvironment

The tumor microenvironment (TME) is increasingly appreciated to play a decisive role in cancer development and response to therapy in all solid tumors. Hypoxia, acidosis, high interstitial pressure, nutrient-poor conditions, and high cellular heterogeneity of the TME arise from interactions between cancer cells and their environment. These properties, in turn, play key roles in the aggressiveness and therapy resistance of the disease, through complex reciprocal interactions between the cancer cell genotype and phenotype, and the physicochemical and cellular environment. Understanding this complexity requires the combination of sophisticated cancer models and high-resolution analysis tools. Models must allow both control and analysis of cellular and acellular TME properties, and analyses must be able to capture the complexity at high depth and spatial resolution. Here, we review the advantages and limitations of key models and methods in order to guide further TME research and outline future challenges.

Epigenetic regulators of clonal hematopoiesis control CD8 T cell stemness during immunotherapy

Epigenetic reinforcement of T cell exhaustion is known to be a major barrier limiting T cell responses during immunotherapy. However, the core epigenetic regulators restricting antitumor immunity during prolonged antigen exposure are not clear. We investigated three commonly mutated epigenetic regulators that promote clonal hematopoiesis to determine whether they affect T cell stemness and response to checkpoint blockade immunotherapy. CD8 T cells lacking Dnmt3a, Tet2, or Asxl1 preserved a progenitor-exhausted (Tpex) population for more than 1 year during chronic antigen exposure without undergoing malignant transformation. Asxl1 controlled the self-renewal capacity of T cells and reduced CD8 T cell differentiation through H2AK119 ubiquitination and epigenetic modification of the polycomb group-repressive deubiquitinase pathway. Asxl1-deficient T cells synergized with anti-PD-L1 immunotherapy to improve tumor control in experimental models and conferred a survival advantage to mutated T cells from treated patients.

Targeting Dectin-1 and or VISTA enhances anti-tumor immunity in melanoma but not colorectal cancer model

PURPOSE

Acquired resistance to immune checkpoint blockers (ICBs) is a major barrier in cancer treatment, emphasizing the need for innovative strategies. Dectin-1 (gene Clec7a) is a C-type lectin receptor best known for its ability to recognize β-glucan-rich structures in fungal cell walls. While Dectin-1 is expressed in myeloid cells and tumor cells, its significance in cancer remains the subject of controversy.

METHODS

Using Celc7a-/- mice and curdlan administration to stimulate Dectin-1 signaling, we explored its impact. VISTA KO mice were employed to assess VISTA's role, and bulk RNAseq analyzed curdlan effects on neutrophils.

RESULTS

Our findings reveal myeloid cells as primary Dectin-1 expressing cells in the tumor microenvironment (TME), displaying an activated phenotype. Strong Dectin-1 co-expression/co-localization with VISTA and PD-L1 in TME myeloid cells was observed. While Dectin-1 deletion lacked protective effects, curdlan stimulation significantly curtailed B16-F10 tumor progression. RNAseq and pathway analyses supported curdlan's role in triggering a cascade of events leading to increased production of pro-inflammatory mediators, potentially resulting in the recruitment and activation of immune cells. Moreover, we identified a heterogeneous subset of Dectin-1+ effector T cells in the TME. Similar to mice, human myeloid cells are the prominent cells expressing Dectin-1 in cancer patients.

CONCLUSION

Our study proposes Dectin-1 as a potential adjunctive target with ICBs, orchestrating a comprehensive engagement of innate and adaptive immune responses in melanoma. This innovative approach holds promise for overcoming acquired resistance to ICBs in cancer treatment, offering avenues for further exploration and development.

Nanomaterial-Mediated Delivery of MLKL Plasmids Sensitizes Tumors to Immunotherapy and Reduces Metastases

Cancer immunotherapy has emerged as a promising approach for the induction of an antitumor response. While immunotherapy response rates are very high in some cancers, the efficacy against solid tumors remains limited caused by the presence of an immunosuppressive tumor microenvironment. Induction of immunogenic cell death (ICD) in the tumor can be used to boost immunotherapy response in solid cancers by eliciting the release of immune-stimulatory components. However, the delivery of components inducing ICD to tumor sites remains a challenge. Here, a novel delivery method is described for antitumor therapy based on MLKL (Mixed Lineage Kinase Domain-Like), a key mediator of necroptosis and inducer of ICD. A novel highly branched poly (β-amino ester)s (HPAEs) system is designed to efficiently deliver MLKL plasmid DNA to the tumor with consequent enhancement of immune antigen presentation for T cell responses in vitro, and improved antitumor response and prolonged survival in tumor-bearing mice. Combination of the therapy with anti-PD-1 treatment revealed significant changes in the composition of the tumor microenvironment, including increased infiltration of CD8+ T cells and tumor-associated lymphocytes. Overall, the HPAEs delivery system can enhance MLKL-based cancer immunotherapy and promote antitumor immune responses, providing a potential treatment to boost cancer immunotherapies.

Intermittent MEK Inhibition with GITR Costimulation Rescues T-cell Function for Increased Efficacy with CTLA-4 Blockade in Solid Tumor Models

MEK inhibitors (MEKi) have shown limited success as a treatment for MAPK/ERK pathway-dependent cancers due to various resistance mechanisms tumor cells can employ. CH5126766 (CKI27) is an inhibitor that binds to MEK and prevents release of RAF, reducing the relief of negative feedback commonly observed with other MEKis. We observed that CKI27 increased MHC expression in tumor cells and improved T cell-mediated killing. Yet, CKI27 also decreased T-cell proliferation, activation, and cytolytic activity by inhibiting the MAPK/ERK pathway that is activated downstream of T-cell receptor signaling. Therefore, we aimed to balance the positive and negative immunomodulatory effects of MEKis for optimal combination with immunotherapy. Intermittent administration of CKI27 allowed T cells to partially recover and costimulation via GITR and OX-40 agonist antibodies completely alleviated inhibition of function. In Kras mutant lung and colon tumor mouse models, intermittent CKI27 and anti-GITR significantly decreased tumor growth and prolonged survival when further combined with CTLA-4 immune checkpoint blockade. Moreover, this triple combination increased CD8+ and CD4+ T-cell proliferation, activation, and effector/memory subsets in the tumor-draining lymph nodes and tumors and led to intratumoral regulatory T-cell destabilization. These data, collectively, will allow for more informed decisions when optimizing combination regimens by overcoming resistance, reducing toxicity, and generating long-term immune responses.

Non-clinical evaluation of pmIL12 gene therapy for approval of the phase I clinical study

Immunotherapeutic drugs are promising medicines for cancer treatment. A potential candidate for immunotherapy is interleukin-12 (IL-12), a cytokine well known for its ability to mediate antitumor activity. We developed a plasmid encoding human IL-12 devoid of an antibiotic resistance gene (phIL12). For the approval of phase I clinical trials in basal cell carcinoma (BCC), the regulatory agency requires non-clinical in vivo testing of the pharmacodynamic, pharmacokinetic and toxicological properties of the plasmid. As human IL-12 is not biologically active in mice, a mouse ortholog of the plasmid phIL12 (pmIL12) was evaluated. The evaluation demonstrated the antitumor effectiveness of the protein accompanied by immune cell infiltration. The plasmid was distributed throughout the body, and the amount of plasmid diminished over time in all organs except the skin around the tumor. The therapy did not cause any detectable systemic toxicity. The results of the non-clinical evaluation demonstrated the safety and efficacy of the pmIL12/phIL12 GET, and on the basis of these results, approval was obtained for the initiation of a phase I clinical study in BCC.

Cryoablation Does Not Significantly Contribute to Systemic Effector Immune Responses in a Poorly Immunogenic B16F10 Melanoma Model

PURPOSE

Cryoablation is a minimally invasive procedure implemented to destroy solid tumors. It also results in the release of tumor antigens into the systemic circulation. Preclinical studies using immunogenic tumor models have shown that cryoablation evokes antitumor immune responses. The mechanisms by which cryoablation impacts immune responses in poorly immunogenic tumors have not been sufficiently explored.

EXPERIMENTAL DESIGN

We used a bilateral B16F10 melanoma model devoid of strong immunogenic antigens. Cryoablation-induced effector immune responses were investigated, also in combination with a peritumoral STING agonist and systemic anti-PD-1. Selective immune cell depletion, T-cell migration arrest, in vivo T-cell transplantation, and cryoablation versus surgical removal techniques were used to determine the contribution of cryoablation and immunotherapies to systemic antitumor effector immune responses.

RESULTS

Treatment of a tumor with cryoablation + STING agonist + anti-PD-1 resulted in the rejection of unablated, contralateral tumors. Depletion studies demonstrated that tumor rejection is essentially dependent on CD8+ T cells. T-cell arrest in the lymph nodes had no effect on the rejection process. Splenic CD8+ T cells isolated from cryoablation-treated mice with B16F10 melanoma, upon transplantation into melanoma-bearing recipients, did not impact the recipient's tumor growth. Finally, comparison of cryoablation + STING agonist + anti-PD-1 versus surgery + STING agonist + anti-PD-1 in the bilateral tumor model showed no difference in the rejection of contralateral tumors.

CONCLUSIONS

Cryoablation does not significantly contribute to systemic antitumor effector immune responses in a B16F10 melanoma model. Cryoablation primarily performs tumor debulking, and immunotherapy functions independently of cryoablation in eliciting antitumor effector immune responses.

Inhibition of glycosphingolipid synthesis with eliglustat in combination with immune checkpoint inhibitors in advanced cancers: preclinical evidence and phase I clinical trial

Glycosphingolipids (GSLs) are abundantly expressed in cancer cells. The effects of GSL-targeted immunotherapies are not fully understood. Here, we show that the inhibition of GSL synthesis with the UDP-glucose ceramide glucosyltransferase inhibitor eliglustat can increase the exposure of the major histocompatibility complex (MHC) and tumour antigen peptides, enhancing the antitumour response of CD8+ T cells in a range of tumour models. We therefore conducted a proof-of-concept phase I trial on the combination of eliglustat and an anti-PD-1 antibody for the treatment of advanced cancers (NCT04944888). The primary endpoints were safety and feasibility, and the secondary endpoint was antitumor activity. All prespecified endpoints were met. Among the 31 enrolled patients, only 1 patient experienced a grade 3 adverse event (AE), and no grade 4 AEs were observed. The objective response rate was 22.6% and the disease control rate reached 71%. Of the 8 patients with proficient mismatch repair/microsatellite stable (pMMR/MSS) colorectal cancer, one achieved complete response and two each had partial response and stable disease. In summary, inhibiting the synthesis of GSLs might represent an effective immunotherapy approach.

Non-viral-mediated gene transfer of OX40 ligand for tumor immunotherapy

Background

Immune checkpoint blockade (ICB) is rapidly becoming a standard of care in the treatment of many cancer types. However, the subset of patients who respond to this type of therapy is limited. Another way to promote antitumoral immunity is the use of immunostimulatory molecules, such as cytokines or T cell co-stimulators. The systemic administration of immunotherapeutics leads to significant immune-related adverse events (irAEs), therefore, the localized antitumoral action is needed. One way to achieve this is intratumoral non-viral gene-immune therapy, which allows for prolonged and localized gene expression, and multiple drug administration. In this study, we combined the previously described non-viral gene delivery system, PEG-PEI-TAT copolymer, PPT, with murine OX40L-encoding plasmid DNA.

Methods

The resulting OX40L/PPT nanoparticles were characterized via gel mobility assay, dynamic light scattering analysis and in vitro transfection efficiency evaluation. The antitumoral efficacy of intratumorally (i.t.) administered nanoparticles was estimated using subcutaneously (s.c.) implanted CT26 (colon cancer), B16F0 (melanoma) and 4T1 (breast cancer) tumor models. The dynamics of stromal immune cell populations was analyzed using flow cytometry. Weight loss and cachexia were used as irAE indicators. The effect of combination of i.t. OX40L/PPT with intraperitoneal PD-1 ICB was estimated in s.c. CT26 tumor model.

Results

The obtained OX40L/PPT nanoparticles had properties applicable for cell transfection and provided OX40L protein expression in vitro in all three investigated cancer models. We observed that OX40L/PPT treatment successfully inhibited tumor growth in B16F0 and CT26 tumor models and showed a tendency to inhibit 4T1 tumor growth. In B16F0 tumor model, OX40L/PPT treatment led to the increase in antitumoral effector NK and T killer cells and to the decrease in pro-tumoral myeloid cells populations within tumor stroma. No irAE signs were observed in all 3 tumor models, which indicates good treatment tolerability in mice. Combining OX40L/PPT with PD-1 ICB significantly improved treatment efficacy in the CT26 subcutaneous colon cancer model, providing protective immunity against CT26 colon cancer cells.

Conclusion

Overall, the anti-tumor efficacy observed with OX40L non-viral gene therapy, whether administered alone or in combination with ICB, highlights its potential to revolutionize cancer gene therapy, thus paving the way for unprecedented advancements in the cancer therapy field.

Intratumoral delivery of the chitin-derived C100 adjuvant promotes robust STING, IFNAR, and CD8+ T cell-dependent anti-tumor immunity

Stimulator of IFN genes (STING) is a promising target for adjuvants utilized in in situ cancer vaccination approaches. However, key barriers remain for clinical translation, including low cellular uptake and accessibility, STING variability necessitating personalized STING agonists, and interferon (IFN)-independent signals that can promote tumor growth. Here, we identify C100, a highly deacetylated chitin-derived polymer (HDCP), as an attractive alternative to conventional STING agonists. C100 promotes potent anti-tumor immune responses, outperforming less deacetylated HDCPs, with therapeutic efficacy dependent on STING and IFN alpha/beta receptor (IFNAR) signaling and CD8+ T cell mediators. Additionally, C100 injection synergizes with systemic checkpoint blockade targeting PD-1. Mechanistically, C100 triggers mitochondrial stress and DNA damage to exclusively activate the IFN arm of the cGAS-STING signaling pathway and elicit sustained IFNAR signaling. Altogether, these results reveal an effective STING- and IFNAR-dependent adjuvant for in situ cancer vaccines with a defined mechanism and distinct properties that overcome common limitations of existing STING therapeutics.

25-Hydroxycholesterol regulates lysosome AMP kinase activation and metabolic reprogramming to educate immunosuppressive macrophages

Macrophages are critical to turn noninflamed "cold tumors" into inflamed "hot tumors". Emerging evidence indicates abnormal cholesterol metabolites in the tumor microenvironment (TME) with unclear function. Here, we uncovered the inducible expression of cholesterol-25-hydroxylase (Ch25h) by interleukin-4 (IL-4) and interleukin-13 (IL-13) via the transcription factor STAT6, causing 25-hydroxycholesterol (25HC) accumulation. scRNA-seq analysis confirmed that CH25Hhi subsets were enriched in immunosuppressive macrophage subsets and correlated to lower survival rates in pan-cancers. Targeting CH25H abrogated macrophage immunosuppressive function to enhance infiltrating T cell numbers and activation, which synergized with anti-PD-1 to improve anti-tumor efficacy. Mechanically, lysosome-accumulated 25HC competed with cholesterol for GPR155 binding to inhibit the kinase mTORC1, leading to AMPKα activation and metabolic reprogramming. AMPKα also phosphorylated STAT6 Ser564 to enhance STAT6 activation and ARG1 production. Together, we propose CH25H as an immunometabolic checkpoint, which manipulates macrophage fate to reshape CD8+ T cell surveillance and anti-tumor response.

Neutrophils bearing adhesive polymer micropatches as a drug-free cancer immunotherapy

Tumour-associated neutrophils can exert antitumour effects but can also assume a pro-tumoural phenotype in the immunosuppressive tumour microenvironment. Here we show that neutrophils can be polarized towards the antitumour phenotype by discoidal polymer micrometric 'patches' that adhere to the neutrophils' surfaces without being internalized. Intravenously administered micropatch-loaded neutrophils accumulated in the spleen and in tumour-draining lymph nodes, and activated splenic natural killer cells and T cells, increasing the accumulation of dendritic cells and natural killer cells. In mice bearing subcutaneous B16F10 tumours or orthotopic 4T1 tumours, intravenous injection of the micropatch-loaded neutrophils led to robust systemic immune responses, a reduction in tumour burden and improvements in survival rates. Micropatch-activated neutrophils combined with the checkpoint inhibitor anti-cytotoxic T-lymphocyte-associated protein 4 resulted in strong inhibition of the growth of B16F10 tumours, and in complete tumour regression in one-third of the treated mice. Micropatch-loaded neutrophils could provide a potent, scalable and drug-free approach for neutrophil-based cancer immunotherapy.

Noncovalently particle-anchored cytokines with prolonged tumor retention safely elicit potent antitumor immunity

Preclinical studies have shown that immunostimulatory cytokines elicit antitumor immune responses but their clinical use is limited by severe immune-related adverse events upon systemic administration. Here, we report a facile and versatile strategy for noncovalently anchoring potent Fc-fused cytokine molecules to the surface of size-discrete particles decorated with Fc-binding peptide for local administration. Following intratumoral injection, particle-anchored Fc cytokines exhibit size-dependent intratumoral retention. The 1-micrometer particle prolongs intratumoral retention of Fc cytokine for over a week and has minimal systemic exposure, thereby eliciting antitumor immunity while eliminating systemic toxicity caused by circulating cytokines. In addition, the combination of these particle-anchored cytokines with immune checkpoint blockade antibodies safely promotes tumor regression in various syngeneic tumor models and genetically engineered murine tumor models and elicits systemic antitumor immunity against tumor rechallenge. Our formulation strategy renders a safe and tumor-agnostic approach that uncouples cytokines' immunostimulatory properties from their systemic toxicities for potential clinical application.

Quantitative performance assessment of Ultivue multiplex panels in formalin-fixed, paraffin-embedded human and murine tumor specimens

We present a rigorous validation strategy to evaluate the performance of Ultivue multiplex immunofluorescence panels. We have quantified the accuracy and precision of four different multiplex panels (three human and one mouse) in tumor specimens with varying levels of T cell density. Our results show that Ultivue panels are typically accurate wherein the relative difference in cell proportion between a multiplex image and a 1-plex image is less than 20% for a given biomarker. Ultivue panels exhibited relatively high intra-run precision (CV ≤ 25%) and relatively low inter-run precision (CV >> 25%) which can be remedied by using local intensity thresholding to gate biomarker positivity. We also evaluated the reproducibility of cell-cell distance estimates measured from multiplex images which show high intra- and inter-run precision. We introduce a new metric, multiplex labeling efficiency, which can be used to benchmark the overall fidelity of the multiplex data across multiple batch runs. Taken together our results provide a comprehensive characterization of Ultivue panels and offer practical guidelines for analyzing multiplex images.

Long-lasting mRNA-encoded interleukin-2 restores CD8+ T cell neoantigen immunity in MHC class I-deficient cancers

Major histocompatibility complex (MHC) class I antigen presentation deficiency is a common cancer immune escape mechanism, but the mechanistic implications and potential strategies to address this challenge remain poorly understood. Studying β2-microglobulin (B2M) deficient mouse tumor models, we find that MHC class I loss leads to a substantial immune desertification of the tumor microenvironment (TME) and broad resistance to immune-, chemo-, and radiotherapy. We show that treatment with long-lasting mRNA-encoded interleukin-2 (IL-2) restores an immune cell infiltrated, IFNγ-promoted, highly proinflammatory TME signature, and when combined with a tumor-targeting monoclonal antibody (mAB), can overcome therapeutic resistance. Unexpectedly, the effectiveness of this treatment is driven by IFNγ-releasing CD8+ T cells that recognize neoantigens cross-presented by TME-resident activated macrophages. These macrophages acquire augmented antigen presentation proficiency and other M1-phenotype-associated features under IL-2 treatment. Our findings highlight the importance of restoring neoantigen-specific immune responses in the treatment of cancers with MHC class I deficiencies.

rWTC-MBTA Vaccine Induces Potent Adaptive Immune Responses Against Glioblastomas via Dynamic Activation of Dendritic Cells

Despite strides in immunotherapy, glioblastoma multiforme (GBM) remains challenging due to low inherent immunogenicity and suppressive tumor microenvironment. Converting "cold" GBMs to "hot" is crucial for immune activation and improved outcomes. This study comprehensively characterized a therapeutic vaccination strategy for preclinical GBM models. The vaccine consists of Mannan-BAM-anchored irradiated whole tumor cells, Toll-like receptor ligands [lipoteichoic acid (LTA), polyinosinic-polycytidylic acid (Poly (I:C)), and resiquimod (R-848)], and anti-CD40 agonistic antibody (rWTC-MBTA). Intracranial GBM models (GL261, SB28 cells) are used to evaluate the vaccine efficacy. A substantial number of vaccinated mice exhibited complete regression of GBM tumors in a T-cell-dependent manner, with no significant toxicity. Long-term tumor-specific immune memory is confirmed upon tumor rechallenge. In the vaccine-draining lymph nodes of the SB28 model, rWTC-MBTA vaccination triggered a major rise in conventional dendritic cell type 1 (cDC1) 12 h post-treatment, followed by an increase in conventional dendritic cell type 2 (cDC2), monocyte-derived dendritic cell (moDC), and plasmacytoid dendritic cell (pDC) on Day 5 and Day 13. Enhanced cytotoxicity of CD4+ and CD8+ T cells in vaccinated mice is verified in co-culture with tumor cells. Analyses of immunosuppressive signals (T-cell exhaustion, myeloid-derived suppressor cells (MDSC), M2 macrophages) in the GBM microenvironment suggest potential combinations with other immunotherapies for enhanced efficacy. In conclusion, the authors findings demonstrate that rWTC-MBTA induces potent and long-term adaptive immune responses against GBM.

A Novel Translational PET Imaging Approach to Quantifying Distal Tumor Immune Activation After Targeted Radiation Therapy and Checkpoint Blockade

PURPOSE

This study aimed to provide a novel noninvasive method to quantify abscopal immune activation and predict combinational treatment response using [68Ga]-NOTA-GZP positron emission tomography (PET) imaging.

METHODS AND MATERIALS

4T1 breast cancer cells were implanted bilaterally in the mammary fat pad of Balb/c mice and Lewis's lung cancer cells (LLC) were implanted bilaterally on the shoulders of C57/Bl6 mice. One of the tumors received a single fraction of 12 Gy irradiation followed by combination of concurrent PD-1 and CTLA-4 inhibitors or controls. Tumor growth of the irradiated and nonirradiated tumors was measured and compared with 12 Gy irradiation only, checkpoint inhibitor only, and no treatment control group. Changes in granzyme B activity were assessed with [68Ga]-NOTA-GZP PET imaging from baseline and every 3 days until day 9.

RESULTS

In the 4T1 model, concurrent treatment with dual checkpoint inhibitors and radiation resulted in reduction of the irradiated tumor volume at day 30. At this same time point, the nonirradiated tumor volume for combination treatment decreased significantly, consistent with abscopal immune activation. Similarly, in the LLC model, concurrent treatment inhibited tumor growth on the nonirradiated tumor at day 15. On day 9, granzyme B PET signal in both 4T1 and LLC models was significantly higher in the nonirradiated tumors that responded to concurrent treatment compared with subsequent nonresponding tumors. A similar lack of granzyme B signal was observed in the nonirradiated tumors from mice that received radiation or checkpoint inhibitors only and control tumors. Receiver operating characteristic analysis identified a PET threshold of 1.505 and 1.233 on day 9 that predicted treatment response in 4T1 and LLC models, respectively.

CONCLUSIONS

[68Ga]-NOTA-GZP PET imaging was able to noninvasively predict abscopal immune activation before subsequent tumor volume changes after combination treatment. It provides a potential translational paradigm for investigating distal immune activation postradiation in a clinical setting.

Mannosylated STING Agonist Drugamers for Dendritic Cell-Mediated Cancer Immunotherapy

The Stimulator of Interferon Genes (STING) pathway is a promising target for cancer immunotherapy. Despite recent advances, therapies targeting the STING pathway are often limited by routes of administration, suboptimal STING activation, or off-target toxicity. Here, we report a dendritic cell (DC)-targeted polymeric prodrug platform (polySTING) that is designed to optimize intracellular delivery of a diamidobenzimidazole (diABZI) small-molecule STING agonist while minimizing off-target toxicity after parenteral administration. PolySTING incorporates mannose targeting ligands as a comonomer, which facilitates its uptake in CD206+/mannose receptor+ professional antigen-presenting cells (APCs) in the tumor microenvironment (TME). The STING agonist is conjugated through a cathepsin B-cleavable valine-alanine (VA) linker for selective intracellular drug release after receptor-mediated endocytosis. When administered intravenously in tumor-bearing mice, polySTING selectively targeted CD206+/mannose receptor+ APCs in the TME, resulting in increased cross-presenting CD8+ DCs, infiltrating CD8+ T cells in the TME as well as maturation across multiple DC subtypes in the tumor-draining lymph node (TDLN). Systemic administration of polySTING slowed tumor growth in a B16-F10 murine melanoma model as well as a 4T1 murine breast cancer model with an acceptable safety profile. Thus, we demonstrate that polySTING delivers STING agonists to professional APCs after systemic administration, generating efficacious DC-driven antitumor immunity with minimal side effects. This new polymeric prodrug platform may offer new opportunities for combining efficient targeted STING agonist delivery with other selective tumor therapeutic strategies.

Low-dose decitabine enhances the efficacy of viral cancer vaccines for immunotherapy

Cancer immunotherapy requires a specific antitumor CD8+ T cell-driven immune response; however, upon genetic and epigenetic alterations of the antigen processing and presenting components, cancer cells escape the CD8+ T cell recognition. As a result, poorly immunogenic tumors are refractory to conventional immunotherapy. In this context, the use of viral cancer vaccines in combination with hypomethylating agents represents a promising strategy to prevent cancer from escaping immune system recognition. In this study, we evaluated the sensitivity of melanoma (B16-expressing ovalbumin) and metastatic triple-negative breast cancer (4T1) cell lines to FDA-approved low-dose decitabine in combination with PeptiCRAd, an adenoviral anticancer vaccine. The two models showed different sensitivity to decitabine in vitro and in vivo when combined with PeptiCRAd. In particular, mice bearing syngeneic 4T1 cancer showed higher tumor growth control when receiving the combinatorial treatment compared to single controls in association with a higher expression of MHC class I on cancer cells and reduction in Tregs within the tumor microenvironment. Furthermore, remodeling of the CD8+ T cell infiltration and cytotoxic activity toward cancer cells confirmed the effect of decitabine in enhancing anticancer vaccines in immunotherapy regimens.

Design and Evaluation of Synthetic Delivery Formulations for Peptide-Based Cancer Vaccines

With the recent advances in neoantigen identification, peptide-based cancer vaccines offer substantial potential in the field of immunotherapy. However, rapid clearance, low immunogenicity, and insufficient antigen-presenting cell (APC) uptake limit the efficacy of peptide-based cancer vaccines. This review explores the barriers hindering vaccine efficiency, highlights recent advancements in synthetic delivery systems, and features strategies for the key delivery steps of lymph node (LN) drainage, APC delivery, cross-presentation strategies, and adjuvant incorporation. This paper also discusses the design of preclinical studies evaluating vaccine efficiency, including vaccine administration routes and murine tumor models.

Protein Kinase STK24 Promotes Tumor Immune Evasion via the AKT-PD-L1 Axis

Immunotherapy targeting PD-L1 is still ineffective for a wide variety of tumors with high unpredictability. Deploying combined immunotherapy with alternative targeting is practical to overcome this therapeutic resistance. Here, the deficiency of serine-threonine kinase STK24 is observed in tumor cells causing substantial attenuation of tumor growth in murine syngeneic models, a process relying on cytotoxic CD8+ T and NK cells. Mechanistically, STK24 in tumor cells associates with and directly phosphorylates AKT at Thr21, which promotes AKT activation and subsequent PD-L1 induction. Deletion or inhibition of STK24, by contrast, blocks IFN-γ-mediated PD-L1 expression. Various murine models indicate that in vivo silencing of STK24 can significantly enhance the efficacy of the anti-PD-1 blockade strategy. Elevated STK24 levels are observed in patient specimens in multiple tumor types and inversely correlated with intratumoral infiltration of cytotoxic CD8+ T cells and with patient survival. The study collectively identifies STK24 as a critical modulator of antitumor immunity, which engages in AKT and PD-L1/PD-1 signaling and is a promising target for combined immunotherapy.

Exploring histological predictive biomarkers for immune checkpoint inhibitor therapy response in non-small cell lung cancer

Treatment challenges persist in advanced lung cancer despite the development of therapies beyond the traditional platinum-based chemotherapy. The early 2000s marked a shift to tyrosine kinase inhibitors targeting epidermal growth factor receptor, ushering in personalized genetic-based treatment. A further significant advance was the development of immune checkpoint inhibitors (ICIs), especially for non-small cell lung cancer. These target programmed death-ligand 1 (PD-L1) and cytotoxic T lymphocyte antigen 4, which enhanced the immune response against tumor cells. However, not all patients respond, and immune-related toxicities arise. This review emphasizes identifying biomarkers for ICI response prediction. While PD-L1 is a widely used, validated biomarker, its predictive accuracy is imperfect. Investigating tumor-infiltrating lymphocytes, tertiary lymphoid structure, and emerging biomarkers such as high endothelial venule, Human leukocyte antigen class I, T-cell immunoreceptors with Ig and ITIM domains, and lymphocyte activation gene-3 counts is promising. Understanding and exploring additional predictive biomarkers for ICI response are crucial for enhancing patient stratification and overall care in lung cancer treatment.

Cancer-associated Fibroblast-specific Expression of the Matricellular Protein CCN1 Coordinates Neovascularization and Stroma Deposition in Melanoma Metastasis

Melanoma is the leading cause of skin cancer-related death. As prognosis of patients with melanoma remains problematic, identification of new therapeutic targets remains essential. Matricellular proteins are nonstructural extracellular matrix proteins. They are secreted into the tumor microenvironment to coordinate behavior among different cell types, yet their contribution to melanoma is underinvestigated. Examples of matricellular proteins include those comprising the CCN family. The CCN family member, CCN1, is highly proangiogenic. Herein, we show that, in human patients with melanoma, although found in several tumor cell types, CCN1 is highly expressed by a subset of cancer-associated fibroblasts (CAF) in patients with melanoma and this expression correlates positively with expression of proangiogenic genes and progressive disease/resistance to anti-PD1 checkpoint inhibitors. Consistent with these observations, in a syngeneic C57BL6 mouse model of melanoma, loss of CCN1 expression from Col1A2-Cre-, herein identified as "universal," fibroblasts, impaired metastasis of subcutaneously injected B16F10 tumor cells to lung, concomitant with disrupted neovascularization and collagen organization. Disruption of the extracellular matrix in the loss of CCN1 was validated using a novel artificial intelligence-based image analysis platform that revealed significantly decreased phenotypic fibrosis and composite morphometric collagen scores. As drug resistance is linked to matrix deposition and neoangiogenesis, these data suggest that CCN1, due to its multifaceted role, may represent a novel therapeutic target for drug-resistant melanoma. Our data further emphasize the essential role that cancer-associated, (universal) Col1A2-Cre-fibroblasts and extracellular matrix remodeling play in coordinating behavior among different cell types within the tumor microenvironment.

SIGNIFICANCE

In human patients, the expression of proangiogenic matricellular protein CCN1 in CAFs correlates positively with expression of stroma and angiogenic markers and progressive disease/resistance to checkpoint inhibitor therapy. In an animal model, loss of CCN1 from CAFs impaired metastasis of melanoma cells, neovascularization, and collagen deposition, emphasizing that CAFs coordinate cellular behavior in a tumor microenvironment and that CCN1 may be a novel target.

Targeting the activated microenvironment with endosialin (CD248)-directed CAR-T cells ablates perivascular cells to impair tumor growth and metastasis

BACKGROUND

Targeting of solid cancers with chimeric antigen receptor (CAR)-T cells is limited by the lack of suitable tumor-specific antigens and the immunosuppressive, desmoplastic tumor microenvironment that impedes CAR-T cell infiltration, activity and persistence. We hypothesized that targeting the endosialin (CD248) receptor, strongly expressed by tumor-associated pericytes and perivascular cancer-associated fibroblasts, would circumvent these challenges and offer an exciting antigen for CAR-T cell therapy due to the close proximity of target cells to the tumor vasculature, the limited endosialin expression in normal tissues and the lack of phenotype observed in endosialin knockout mice.

METHODS

We generated endosialin-directed E3K CAR-T cells from three immunocompetent mouse strains, BALB/c, FVB/N and C57BL/6. E3K CAR-T cell composition (CD4+/CD8+ ratio), activity in vitro against endosialin+ and endosialin- cells, and expansion and activity in vivo in syngeneic tumor models as well as in tumor-naive healthy and wounded mice and tumor-bearing endosialin knockout mice was assessed.

RESULTS

E3K CAR-T cells were active in vitro against both mouse and human endosialin+, but not endosialin-, cells. Adoptively transferred E3K CAR-T cells exhibited no activity in endosialin knockout mice, tumor-naive endosialin wildtype mice or in wound healing models, demonstrating an absence of off-target and on-target/off-tumor activity. By contrast, adoptive transfer of E3K CAR-T cells into BALB/c, FVB/N or C57BL/6 mice bearing syngeneic breast or lung cancer lines depleted target cells in the tumor stroma resulting in increased tumor necrosis, reduced tumor growth and a substantial impairment in metastatic outgrowth.

CONCLUSIONS

Together these data highlight endosialin as a viable antigen for CAR-T cell therapy and that targeting stromal cells closely associated with the tumor vasculature avoids CAR-T cells having to navigate the harsh immunosuppressive tumor microenvironment. Further, the ability of E3K CAR-T cells to recognize and target both mouse and human endosialin+ cells makes a humanized and optimized E3K CAR a promising candidate for clinical development applicable to a broad range of solid tumor types.

A dual-functional oncolytic adenovirus ZD55-aPD-L1 scFv armed with PD-L1 inhibitor potentiates its antitumor activity

BACKGROUND

Clinical data indicate that a substantial portion of cancer patients, though eligible for immune checkpoint inhibitor (ICI) therapy, cannot fully benefit from ICI monotherapy due to the poor immunogenicity of tumors and lack of tumor-infiltrating lymphocytes within the 'cold' tumor microenvironment (TME). In addition to poor antibody penetrance into the TME, systemic delivery of ICIs is associated with immune-related adverse events (irAEs) among recipients, some of which are life-threatening. Oncolytic virotherapy is a potentially viable approach to improving the efficacy of ICI therapy because of their ability to selectively replicate and lyse tumor cells, release tumor-associated antigens (TAAs), induce inflammatory response and promote lymphocyte infiltration in tumors.

METHODS

A recombinant oncolytic adenoviruses (OAd), denoted ZD55-aPD-L1 scFv, which carried the expression cassette for anti-PD-L1 scFv was constructed by molecular cloning. Western blot and ELISA assay were performed to detect aPD-L1 scFv expression. Flow cytometry were used to analyse PD-L1 expression and count tumor cells. Co-culture assay of human peripheral blood mononuclear cells (PBMCs) with tumor cells in vitro and triple-negative breast cancer (TNBC) MDA-MB-231 tumor-bearing model in vivo were evaluated the antitumor effects of recombinant oncolytic adenoviruses ZD55-aPD-L1 scFv.

RESULTS

We found that cells infected with recombinant oncolytic adenovirus ZD55-aPD-L1 scFv can effectively express aPD-L1 scFv, which function similarly to its full-length anti-PD-L1 antibody. PBMCs have inherently very limited killing effect on tumor cells even with administration of anti-PD-L1 antibody as observed from our in vitro co-cultures. Treatment consisting of ZD55 alone or ZD55 combined with anti-PD-L1 antibody yielded mediocre antitumor efficacy in subsequent in vitro and in vivo investigations, but were all substantially surpassed by the synergistic antitumor effects observed with ZD55-aPD-L1 scFv treatment. We show that the concomitant direct oncolysis by the recombinant OAd and localized autocrine/paracrine interception of PD-1:PD-L1 checkpoint interaction mediated by ZD55-aPD-L1 scFv-infected cells is exceedingly superior to co-administration of ZD55 and anti-PD-L1 antibody in the human TNBC mice model.

CONCLUSIONS

Our results provided evidence for the development of novel strategies, in this case an anti-PD-L1 scFv-armed OAd, to bolster immune responses to 'cold' tumors and to improve therapeutic responsiveness to ICIs.

Systemic Delivery of Paclitaxel by Find-Me Nanoparticles Activates Antitumor Immunity and Eliminates Tumors

Local delivery of immune-activating agents has shown promise in overcoming an immunosuppressive tumor microenvironment (TME) and stimulating antitumor immune responses in tumors. However, systemic therapy is ultimately needed to treat tumors that are not readily locatable or accessible. To enable systemic delivery of immune-activating agents, we employ poly(lactic-co-glycolide) (PLGA) nanoparticles (NPs) with a track record in systemic application. The surface of PLGA NPs is decorated with adenosine triphosphate (ATP), a damage-associated molecular pattern to recruit antigen-presenting cells (APCs). The ATP-conjugated PLGA NPs (NPpD-ATP) are loaded with paclitaxel (PTX), a chemotherapeutic agent inducing immunogenic cell death to generate tumor antigens in situ. We show that the NPpD-ATP retains ATP activity in hostile TME and provides a stable "find-me" signal to recruit APCs. Therefore, the PTX-loaded NPpD-ATP helps populate antitumor immune cells in TME and attenuate the growth of CT26 and B16F10 tumors better than a mixture of PTX-loaded NPpD and ATP. Combined with anti-PD-1 antibody, PTX-loaded NPpD-ATP achieves complete regression of CT26 tumors followed by antitumor immune memory. This study demonstrates the feasibility of systemic immunotherapy using a PLGA NP formulation that delivers ICD-inducing chemotherapy and an immunostimulatory signal.

Leukocyte-associated immunoglobulin-like receptor-1 blockade in combination with programmed death-ligand 1 targeting therapy mediates increased tumour control in mice

Collagen expression and structure in the tumour microenvironment are associated with tumour development and therapy response. Leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) is a widely expressed inhibitory collagen receptor. LAIR-2 is a soluble homologue of LAIR-1 that competes for collagen binding. Multiple studies in mice implicate blockade of LAIR-1:collagen interaction in cancer as a promising therapeutic strategy. Here, we investigated the role of LAIR-1 in anti-tumour responses. We show that although LAIR-1 inhibits activation, proliferation, and cytokine production of mouse T cells in vitro, tumour outgrowth in LAIR-1-deficient mice did not differ from wild type mice in several in vivo tumour models. Furthermore, treatment with NC410, a LAIR-2-Fc fusion protein, did not result in increased tumour clearance in tested immunocompetent mice, which contrasts with previous data in humanized mouse models. This discrepancy may be explained by our finding that NC410 blocks human LAIR-1:collagen interaction more effectively than mouse LAIR-1:collagen interaction. Despite the lack of therapeutic impact of NC410 monotherapy, mice treated with a combination of NC410 and anti-programmed death-ligand 1 did show reduced tumour burden and increased survival. Using LAIR-1-deficient mice, we showed that this effect seemed to be dependent on the presence of LAIR-1. Taken together, our data demonstrate that the absence of LAIR-1 signalling alone is not sufficient to control tumour growth in multiple immunocompetent mouse models. However, combined targeting of LAIR-1 and PD-L1 results in increased tumour control. Thus, additional targeting of the LAIR-1:collagen pathway with NC410 is a promising approach to treating tumours where conventional immunotherapy is ineffective.

Antitumour effect of the mitochondrial complex III inhibitor Atovaquone in combination with anti-PD-L1 therapy in mouse cancer models

Immune checkpoint blockade (ICB) provides effective and durable responses for several tumour types by unleashing an immune response directed against cancer cells. However, a substantial number of patients treated with ICB develop relapse or do not respond, which has been partly attributed to the immune-suppressive effect of tumour hypoxia. We have previously demonstrated that the mitochondrial complex III inhibitor atovaquone alleviates tumour hypoxia both in human xenografts and in cancer patients by decreasing oxygen consumption and consequently increasing oxygen availability in the tumour. Here, we show that atovaquone alleviates hypoxia and synergises with the ICB antibody anti-PD-L1, significantly improving the rates of tumour eradication in the syngeneic CT26 model of colorectal cancer. The synergistic effect between atovaquone and anti-PD-L1 relied on CD8+ T cells, resulted in the establishment of a tumour-specific memory immune response, and was not associated with any toxicity. We also tested atovaquone in combination with anti-PD-L1 in the LLC (lung) and MC38 (colorectal) cancer syngeneic models but, despite causing a considerable reduction in tumour hypoxia, atovaquone did not add any therapeutic benefit to ICB in these models. These results suggest that atovaquone has the potential to improve the outcomes of patients treated with ICB, but predictive biomarkers are required to identify individuals likely to benefit from this intervention.

Comparative Study of the Immune Microenvironment in Heterotopic Tumor Models

The tumor microenvironment (TME) is pivotal in cancer progression and the response to immunotherapy. A "hot" tumor typically contains immune cells that promote anti-tumor immunity, predicting positive prognosis. "Cold" tumors lack immune cells, suggesting a poor outlook across various cancers. Recent research has focused on converting "cold" tumors into "hot" tumors to enhance the success of immunotherapy. A prerequisite for the studies of the TME is an accurate knowledge of the cell populations of the TME. This study aimed to describe the immune TME of lung and colorectal cancer and melanoma, focusing on lymphoid and myeloid cell populations. We induced heterotopic immunocompetent tumors in C57BL/6 mice, using KP and LLC (Lewis lung carcinoma) cells for lung cancer, MC38 cells for colorectal cancer, and B16-F10 cells for melanoma. Immune cell infiltration was analyzed using multicolor flow cytometry in single-cell suspensions after tumor excision. KP cell tumors showed an abundance of neutrophils and eosinophils; however, they contained much less adaptive immune cells, while LLC cell tumors predominated in monocytes, neutrophils, and monocyte-derived dendritic cells. Monocytes and neutrophils, along with a significant T cell infiltration, were prevalent in MC38 tumors. Lastly, B16-F10 tumors were enriched in macrophages, while showing only moderate T cell presence. In conclusion, our data provide a detailed overview of the immune TME of various heterotopic tumors, highlighting the variabilities in the immune cell profiles of different tumor entities. Our data may be a helpful basis when investigating new immunotherapies, and thus, this report serves as a helpful tool for preclinical immunotherapy research design.

FGL2 promotes tumour growth and attenuates infiltration of activated immune cells in melanoma and ovarian cancer models

The tumour microenvironment is infiltrated by immunosuppressive cells, such as regulatory T cells (Tregs), which contribute to tumour escape and impede immunotherapy outcomes. Soluble fibrinogen-like protein 2 (sFGL2), a Treg effector protein, inhibits immune cell populations, via receptors FcγRIIB and FcγRIII, leading to downregulation of CD86 in antigen presenting cells and limiting T cell activation. Increased FGL2 expression is associated with tumour progression and poor survival in several different cancers, such as glioblastoma multiforme, lung, renal, liver, colorectal, and prostate cancer. Querying scRNA-seq human cancer data shows FGL2 is produced by cells in the tumour microenvironment (TME), particularly monocytes and macrophages as well as T cells and dendritic cells (DCs), while cancer cells have minimal expression of FGL2. We studied the role of FGL2 exclusively produced by cells in the TME, by leveraging Fgl2 knockout mice. We tested two murine models of cancer in which the role of FGL2 has not been previously studied: epithelial ovarian cancer and melanoma. We show that absence of FGL2 leads to a more activated TME, including activated DCs (CD86+, CD40+) and T cells (CD25+, TIGIT+), as well as demonstrating for the first time that the absence of FGL2 leads to more activated natural killer cells (DNAM-1+, NKG2D+) in the TME. Furthermore, the absence of FGL2 leads to prolonged survival in the B16F10 melanoma model, while the absence of FGL2 synergizes with oncolytic virus to prolong survival in the ID8-p53-/-Brca2-/- ovarian cancer model. In conclusion, targeting FGL2 is a promising cancer treatment strategy alone and in combination immunotherapies.

Primary tumor-induced immunity suppresses bone metastases of breast cancer in syngeneic immunocompetent mouse models

The immune system plays a crucial role in cancer development and progression. More than a century ago, mouse models showed that primary tumors suppressed the growth of newly implanted secondary tumors. This phenomenon, in which tumor-primed T cells mediate the rejection of tumor growth at a distant site, is known as concomitant tumor immunity. Here, we investigated the role of concomitant immunity in the development of breast cancer bone metastases using newly developed syngeneic immunocompetent mouse models. The presence of primary breast tumors developed by tumor cell injection into the mammary fat pads (MFPs) significantly reduced bone metastases of mouse breast cancer 4T1 and EMT6 cells induced by cell injection through the caudal artery (CA). Similar results were obtained when primary tumors were surgically resected prior to CA injection of tumor cells. In contrast, no inhibition was found when MFP and CA injections were performed using different cell combinations. Immunohistochemical studies revealed that the number of CD8+ T cells in bone metastases of 4T1 and EMT6 cells was significantly increased in the presence of primary tumors. The primary tumor-induced inhibition of bone metastases was not reproduced in T cell-deficient athymic nude mice. Furthermore, depletion of CD8+ T cells using an anti-CD8α antibody also abolished the primary tumor-induced inhibition of bone metastases. Taken together, these results suggest that immune cell priming by orthotopic breast tumors inhibits the development of breast cancer bone metastases, which is predominantly mediated by CD8+ cytotoxic T lymphocytes.

Interferon gamma immunoPET imaging to evaluate response to immune checkpoint inhibitors

Introduction

We previously developed a 89Zr-labeled antibody-based immuno-positron emission tomography (immunoPET) tracer targeting interferon gamma (IFNγ), a cytokine produced predominantly by activated T and natural killer (NK) cells during pathogen clearance, anti-tumor immunity, and various inflammatory and autoimmune conditions. The current study investigated [89Zr]Zr-DFO-anti-IFNγ PET as a method to monitor response to immune checkpoint inhibitors (ICIs).

Methods

BALB/c mice bearing CT26 colorectal tumors were treated with combined ICI (anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and anti-programmed death 1 (PD-1)). The [89Zr]Zr-DFO-anti-IFNγ PET tracer, generated with antibody clone AN18, was administered on the day of the second ICI treatment, with PET imaging 72 hours later. Tumor mRNA was analyzed by quantitative reverse-transcribed PCR (qRT-PCR).

Results

We detected significantly higher intratumoral localization of [89Zr]Zr-DFO-anti-IFNγ in ICI-treated mice compared to untreated controls, while uptake of an isotype control tracer remained similar between treated and untreated mice. Interestingly, [89Zr]Zr-DFO-anti-IFNγ uptake was also elevated relative to the isotype control in untreated mice, suggesting that the IFNγ-specific tracer might be able to detect underlying immune activity in situ in this immunogenic model. In an efficacy experiment, a significant inverse correlation between tracer uptake and tumor burden was also observed. Because antibodies to cytokines often exhibit neutralizing effects which might alter cellular communication within the tumor microenvironment, we also evaluated the impact of AN18 on downstream IFNγ signaling and ICI outcomes. Tumor transcript analysis using interferon regulatory factor 1 (IRF1) expression as a readout of IFNγ signaling suggested there may be a marginal disruption of this pathway. However, compared to a 250 µg dose known to neutralize IFNγ, which diminished ICI efficacy, a tracer-equivalent 50 µg dose did not reduce ICI response rates.

Discussion

These results support the use of IFNγ PET as a method to monitor immune activity in situ after ICI, which may also extend to additional T cell-activating immunotherapies.

Pan-PI3K inhibition with copanlisib overcomes Treg- and M2-TAM-mediated immune suppression and promotes anti-tumor immune responses

The PI3K pathway is one of the most frequently altered signaling pathways in human cancer. In addition to its function in cancer cells, PI3K plays a complex role in modulating anti-tumor immune responses upon immune checkpoint inhibition (ICI). Here, we evaluated the effects of the pan-Class I PI3K inhibitor copanlisib on different immune cell types in vitro and on tumor growth and immune cell infiltration in syngeneic murine cancer models. Intermittent treatment with copanlisib resulted in a strong in vivo anti-tumor efficacy, increased tumor infiltration of activated T cells and macrophages, and increased CD8+ T cell/regulatory T cell and M1/M2 macrophage ratios. The strong in vivo efficacy was at least partially due to immunomodulatory activity of copanlisib, as in vitro these murine cancer cells were resistant to PI3K inhibition. Furthermore, the combination of copanlisib with the ICI antibody anti-PD-1 demonstrated enhanced anti-tumor efficacy in both ICI-sensitive and insensitive syngeneic mouse tumor models. Importantly, in an ICI-sensitive model, combination therapy resulted in complete remission and prevention of tumor recurrence. Thus, the combination of ICIs with PI3K inhibition by intermittently dosed copanlisib represents a promising new strategy to increase sensitivity to ICI therapies and to treat human solid cancers.

HRS mediates tumor immune evasion by regulating proteostasis-associated interferon pathway activation

By sorting receptor tyrosine kinases into endolysosomes, the endosomal sorting complexes required for transport (ESCRTs) are thought to attenuate oncogenic signaling in tumor cells. Paradoxically, ESCRT members are upregulated in tumors. Here, we show that disruption of hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), a pivotal ESCRT component, inhibited tumor growth by promoting CD8+ T cell infiltration in melanoma and colon cancer mouse models. HRS ablation led to misfolded protein accumulation and triggered endoplasmic reticulum (ER) stress, resulting in the activation of the type I interferon pathway in an inositol-requiring enzyme-1α (IRE1α)/X-box binding protein 1 (XBP1)-dependent manner. HRS was upregulated in tumor cells with high tumor mutational burden (TMB). HRS expression associates with the response to PD-L1/PD-1 blockade therapy in melanoma patients with high TMB tumors. HRS ablation sensitized anti-PD-1 treatment in mouse melanoma models. Our study shows a mechanism by which tumor cells with high TMB evade immune surveillance and suggests HRS as a promising target to improve immunotherapy.

An engineered immunocytokine with collagen affinity improves the tumor bioavailability, tolerability, and therapeutic efficacy of IL-2

The clinical utility of human interleukin-2 (hIL-2) is limited by its short serum half-life, preferential activation of regulatory T (TReg) over immune effector cells, and dose-limiting toxicities. We previously engineered F10 immunocytokine (IC), an intramolecularly assembled cytokine/antibody fusion protein that linked hIL-2 to an anti-IL-2 antibody (denoted F10) that extended IL-2 half-life and augmented the immune effector to TReg ratio. Here, we leveraged molecular engineering to improve the anti-tumor therapeutic efficacy and tolerability of F10 IC by developing an iteration, denoted F10 IC-CBD (collagen binding domain), designed for intratumoral administration and in situ retention based on collagen affinity. F10 IC-CBD retained IL-2 bioactivity exclusively in the tumor and eliminated IL-2-associated toxicities. Furthermore, F10 IC exhibited potent single-agent therapeutic efficacy and synergy with systemic immune checkpoint blockade and elicited an abscopal response in mouse tumors models. This engineered fusion protein presents a prototype for the design of intratumoral therapies.

Dose-Specific Intratumoral GM-CSF Modulates Breast Tumor Oxygenation and Antitumor Immunity

GM-CSF has been employed as an adjuvant to cancer immunotherapy with mixed results based on dosage. We previously showed that GM-CSF regulated tumor angiogenesis by stimulating soluble vascular endothelial growth factor (VEGF) receptor-1 from monocytes/macrophages in a dose-dependent manner that neutralized free VEGF, and intratumoral injections of high-dose GM-CSF ablated blood vessels and worsened hypoxia in orthotopic polyoma middle T Ag (PyMT) triple-negative breast cancer (TNBC). In this study, we assessed both immunoregulatory and oxygen-regulatory components of low-dose versus high-dose GM-CSF to compare effects on tumor oxygen, vasculature, and antitumor immunity. We performed intratumoral injections of low-dose GM-CSF or saline controls for 3 wk in FVB/N PyMT TNBC. Low-dose GM-CSF uniquely reduced tumor hypoxia and normalized tumor vasculature by increasing NG2+ pericyte coverage on CD31+ endothelial cells. Priming of "cold," anti-PD1-resistant PyMT tumors with low-dose GM-CSF (hypoxia reduced) sensitized tumors to anti-PD1, whereas high-dose GM-CSF (hypoxia exacerbated) did not. Low-dose GM-CSF reduced hypoxic and inflammatory tumor-associated macrophage (TAM) transcriptional profiles; however, no phenotypic modulation of TAMs or tumor-infiltrating lymphocytes were observed by flow cytometry. In contrast, high-dose GM-CSF priming increased infiltration of TAMs lacking the MHC class IIhi phenotype or immunostimulatory marker expression, indicating an immunosuppressive phenotype under hypoxia. However, in anti-PD1 (programmed cell death 1)-susceptible BALB/c 4T1 tumors (considered hot versus PyMT), high-dose GM-CSF increased MHC class IIhi TAMs and immunostimulatory molecules, suggesting disparate effects of high-dose GM-CSF across PyMT versus 4T1 TNBC models. Our data demonstrate a (to our knowledge) novel role for low-dose GM-CSF in reducing tumor hypoxia for synergy with anti-PD1 and highlight why dosage and setting of GM-CSF in cancer immunotherapy regimens require careful consideration.

Investigation of the enhanced antitumour potency of STING agonist after conjugation to polymer nanoparticles

Intravenously administered cyclic dinucleotides and other STING agonists are hampered by low cellular uptake and poor circulatory half-life. Here we report the covalent conjugation of cyclic dinucleotides to poly(β-amino ester) nanoparticles through a cathepsin-sensitive linker. This is shown to increase stability and loading, thereby expanding the therapeutic window in multiple syngeneic tumour models, enabling the study of how the long-term fate of the nanoparticles affects the immune response. In a melanoma mouse model, primary tumour clearance depends on the STING signalling by host cells-rather than cancer cells-and immune memory depends on the spleen. The cancer cells act as a depot for the nanoparticles, releasing them over time to activate nearby immune cells to control tumour growth. Collectively, this work highlights the importance of nanoparticle structure and nano-biointeractions in controlling immunotherapy efficacy.

Antitumor activity of pegylated human interferon β as monotherapy or in combination with immune checkpoint inhibitors via tumor growth inhibition and dendritic cell activation

Type I interferons (IFN), especially human IFN alpha (IFNα), have been utilized for antitumor therapy for decades. Human interferon beta (IFNβ) is rarely used for cancer treatment, despite advantages over IFNα in biological activities such as tumor growth inhibition and dendritic cell (DC) activation. The utilization of pegylated human IFNβ (PEG-IFNβ), as monotherapy or in combination with immune checkpoint inhibitors (ICIs) was evaluated in this study through in vivo efficacy studies in syngeneic mouse melanoma, non-small cell lung cancer (NSCLC), and colon adenocarcinoma (COAD) models resistant to immune checkpoint inhibitors (ICIs). In vitro comparative study of PEG-IFNβ and pegylated IFNα-2b was performed in terms of tumor growth inhibition against human melanoma, NSCLC and COAD cell lines and activation of human monocyte-derived DCs (MoDCs). Our data demonstrate that the in vivo antitumor effects of PEG-IFNβ are partially attributable to tumor growth-inhibitory effects and DC-activating activities, superior to pegylated IFNα-2b. Our findings suggest that utilizing PEG-IFNβ as an antitumor therapy can enhance the therapeutic effect of ICIs in ICI-resistant tumors by directly inhibiting tumor growth and induction of DC maturation.

Tumor Cell-Intrinsic c-Myb Upregulation Stimulates Antitumor Immunity in a Murine Colorectal Cancer Model

The transcription factor c-Myb is overexpressed in many different types of solid tumors, including colorectal cancer. However, its exact role in tumorigenesis is unclear. In this study, we show that tumor-intrinsic c-Myb expression in mouse models of colon cancer and melanoma suppresses tumor growth. Although no differences in proliferation, apoptosis, and angiogenesis of tumors were evident in tumors with distinct levels of c-Myb expression, we observed changes in intratumoral immune cell infiltrates. MC38 tumors with upregulated c-Myb expression showed increased numbers of CD103+ dendritic cells and eosinophils, but decreased tumor-associated macrophages (TAM). Concomitantly, an increase in the number of activated cytotoxic CD8+ T cells upon c-Myb upregulation was observed, which correlated with a pro-inflammatory tumor microenvironment and increased numbers of M1 polarized TAMs. Mechanistically, c-Myb upregulation in immunogenic MC38 colon cancer cells resulted in enhanced expression of immunomodulatory genes, including those encoding β2-microglobulin and IFNβ, and decreased expression of the gene encoding the chemokine receptor CCR2. The increased numbers of activated cytotoxic CD8+ T cells contributed to tumor growth attenuation. In poorly immunogenic CT26, LLC, and B16-BL6 tumor cells, c-Myb upregulation did not affect the immunomodulatory gene expression. Despite this, c-Myb upregulation led to reduced B16-BL6 tumor growth but it did not affect tumor growth of CT26 and LLC tumors. Altogether, we postulate that c-Myb functions as a tumor suppressor in a tumor cell-type specific manner and modulates antitumor immunity.

Targeting the pericyte antigen DLK1 with an alpha type-1 polarized dendritic cell vaccine results in tumor vascular modulation and protection against colon cancer progression

Despite the availability of various treatment options, colorectal cancer (CRC) remains a significant contributor to cancer-related mortality. Current standard-of-care interventions, including surgery, chemotherapy, and targeted agents like immune checkpoint blockade and anti-angiogenic therapies, have improved short-term patient outcomes depending on disease stage, but survival rates with metastasis remain low. A promising strategy to enhance the clinical experience with CRC involves the use of dendritic cell (DC) vaccines that incite immunity against tumor-derived blood vessels, which are necessary for CRC growth and progression. In this report, we target tumor-derived pericytes expressing DLK1 with a clinically-relevant alpha type-1 polarized DC vaccine (αDC1) in a syngeneic mouse model of colorectal cancer. Our pre-clinical data demonstrate the αDC1 vaccine's ability to induce anti-tumor effects by facilitating cytotoxic T lymphocyte activity and ablating the tumor vasculature. This work, overall, provides a foundation to further interrogate immune-mediated mechanisms of protection in order to help devise efficacious αDC1-based strategies for patients with CRC.