InVivoMAb anti-mouse CTLA-4 (CD152)

Immune checkpoint blockade (ICB) evokes antitumor immunity through the reinvigoration of T cell responses. T cell differentiation status controls response, with less differentiated cells having an enhanced capacity to proliferate after ICB. Given that conventional type 1 dendritic cells (cDC1) maintain precursor exhausted T cells (TPEX), we hypothesized that expansion of cDC1s with Flt3L could enhance responses to ICB. Here we show that treatment with Fms-related tyrosine kinase 3 ligand (Flt3L) expands CD62L+SLAMF6+CD8+ T cells in the tumor through a mechanism that requires XCR1+ dendritic cells to traffic to the tumor-draining lymph node. The combination of Flt3L and anti-CTLA-4 enhanced therapeutic responses. Combination therapy is associated with the emergence of a CD8+ T cell subset characterized by the expression of Il21r and oligoclonal expansion of CD8+ T cells within tumors through a mechanism that is dependent on lymph node egress.

Colorectal cancer (CRC) is a leading cause of cancer-related death and remains a significant global health challenge. Cancer vaccines have emerged as a promising immunotherapy for long-term tumor control. While Listeria monocytogenes (Lm)-based intravenous vaccines can generate tumor-reactive CD8 T cells, clinical trial success has been limited. Here, we sought to determine whether in vivo targeting of gastrointestinal tissues with foodborne delivery of Lm-based cancer vaccines controlled tumor growth in murine models of CRC.

Radiotherapy (RT) is a clinical mainstay of cancer treatment that triggers tumor-specific immune responses. However, the effectiveness is usually hampered due to the hypoxic tumor microenvironment (TME) and the ambivalent impact of RT on the immune landscape of tumors. Herein, we develop an injectable hydrogel encapsulating interleukin-12 (IL-12)/anti-CTLA-4 (aCTLA-4) co-engineered red blood cells (RBC), which is in situ self-assembled within the TME to increase oxygen supply and instigate sequential aCTLA-4/IL-12 release, thus achieving Ba/O2 self-compensated radiosensitization and activating multistage immune responses. Once in the acidic TME, the in situ injected BaO2 undergoes hydrolysis to generate H2O2 and Ba2+, followed by the rapid reaction of Ba2+ with sodium alginate to afford a biocompatible hydrogel. Meanwhile, catalase presented on RBC converts H2O2 into O2, thereby alleviating hypoxia-induced radioresistance and inducing O2-mediated pore formation on RBC membrane for rapid release of aCTLA-4 to relieve tumor immunosuppression. Subsequently, IL-12 anchored on RBC is dilatorily released and interacts with T/NK cells within the TME to induce IFN-γ-dependent antitumor immunity. Taken together, the in situ self-assembled cell reservoir hydrogel offers a futuristic avenue to realize multistage radioimmunotherapy for effective tumor regression by programmable immunoregulation with significant clinical value.

T cell exhaustion has been implicated in cancer and infectious diseases. In this study, we report a novel mouse model, "MolT-II", with T cells expressing a transgenic T cell receptor (TCR) specific for a Moloney virus envelope-derived, MHC class II-presented peptide epitope. Characterization of MolT-II CD4 T cells revealed that they are dysfunctional, showing severely impaired effector functions, reduced proliferation and increased baseline expression of co-inhibitory receptors such as PD-1, LAG-3 and CTLA-4, likely due to chronic exposure to a self-antigen. We further show that epitope-specific peptide vaccination combined with immune checkpoint blockade is able to restore the function of MolT-II CD4 T cells in vivo, associated with enhanced tumor control in mice. The MolT-II mouse strain thus represents an in vivo model for reversible CD4 T cell dysfunction, allowing the study of the role of CD4 T cell regulation in cancer, mechanisms underlying CD4 T cell dysfunction and exhaustion, and novel immunomodulatory therapies aiming to rescue dysfunctional T cells.

Immune checkpoint inhibitor (ICI) therapy is effective and in routine clinical use for various cancers, but accurately identifying which patients will respond remains a significant challenge. The PET agent 18F-FDG has uptake by cancer cells as well as inflammation induced by ICI therapy, complicating and often limiting the utility of 18F-FDG for early response assessment during ICI therapy. An imaging agent that accurately distinguishes responders from nonresponders early in the course of ICI therapy could enable intensification or change of therapy for nonresponders. In this study, the 18F-labeled amino acid 18F-MeFAMP, a fluorinated analog selectively targeting system A amino acid transport, was compared with 18F-FDG in the MC38 syngeneic mouse model of ICI therapy. 18F-MeFAMP was chosen because of the relatively low uptake of system A substrates in inflammatory tissues combined with growing evidence suggesting system A transporters are involved in immunotherapy. Methods: PET/CT imaging was used to compare tumor uptake of 18F-MeFAMP with tumor uptake of 18F-FDG before and 6 d after starting dual ICIs in MC38 tumor-bearing female C57BL/6 mice. SUVs, biologic tumor volumes, and total lesion activity were measured along with selected tumor-to-organ ratios. Histogram analysis of tracer uptake was performed to assess differences in tumor activity distribution between responders and nonresponders. Results:18F-FDG showed no significant differences at baseline or after ICI regardless of response. In contrast, 18F-MeFAMP SUVs defined using a 40% of SUVmax threshold (SUV40%) decreased significantly in responders (-60.0% ± 15.6%, P < 0.0001), whereas nonresponders showed no significant change (+45.5% ± 51.2%, P = 0.09). Similar patterns were observed with SUVmax, biologic tumor volume, and total lesion activity measures with 18F-MeFAMP. Histogram analysis revealed significant 18F-MeFAMP uptake differences between groups before and after imaging (P < 0.05). 18F-MeFAMP demonstrated low uptake in common metastatic sites, including liver, lungs, and brain. Conclusion:18F-MeFAMP better detected early ICI response than 18F-FDG with favorable whole-body imaging properties. These findings support further investigation of 18F-MeFAMP for early evaluation of response to ICI and the role of system A substrates in cancer and immune cells before and during ICI.

Activated T cells and macrophages play a critical role in immune-associated myocarditis. However, the molecular and cellular mechanisms driving cardiomyocyte damage by immune cells remain poorly understood. In this study, we co-cultured human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) with activated human peripheral blood mononuclear cells (aPBMCs) to recapitulate myocardial infiltration of immune cells. Our results demonstrated that aPBMCs induced hiPSC-CMs death in a dose- and time-dependent manner. Transcriptome analysis revealed the activation of several death pathways, including pyroptosis, apoptosis and necroptosis. The time course of immunofluorescence staining of key proteins related to different death pathways demonstrated that necroptosis was the earliest activated pathway. Pharmacological blockade of necroptosis by targeting mixed lineage kinase domain-like protein (MLKL), receptor-interacting protein kinase 1 (RIPK1) and receptor-interacting protein RIPK1 kinase 3 (RIPK3) protected hiPSC-CMs against injury induced by aPBMCs, while inhibitors of pyroptosis and apoptosis showed no protective effect. Moreover, MLKL knockdown in hiPSC-CMs prevented cell death due to aPBMCs challenge. Additionally, we validated the cardioprotective effects of blocking necroptosis in a mouse model of immune checkpoint inhibitors (ICIs)-related myocarditis using a combination of long-term anti-programmed cell death 1 (PD- 1) and anti-cytotoxic T-lymphocyte antigen- 4 (CTLA- 4) antibodies. ICIs led to elevation of myocardial injury markers in serum and activated immune cells infiltration. Furthermore, in vivo administration of a MLKL inhibitor prevented ICIs-induced myocardial injury. In conclusion, our findings suggested that MLKL-mediated necroptosis predominantly contributed to cardiomyocyte death resulting from activated immune cells. Suppressing necroptosis may be an effective therapeutic approach against myocardial damage in myocarditis.

Colorectal cancer and liver metastases are a leading cause of cancer-related mortality. Overexpression of the immunostimulatory cytokine TNFSF14/LIGHT associates with improved survival and correlates with increased tumor-infiltrating lymphocytes in patients and a clinically relevant model of colorectal liver metastases. We demonstrate that LIGHT monotherapy activates T cells, but also induces T cell exhaustion and the recruitment of immunosuppressive elements. As colorectal liver metastases exhibit high levels of CTLA-4 expression, we combined LIGHT overexpression with anti-CTLA-4, leading to complete tumor control. The combination functions by homing tumor-infiltrating lymphocytes, inducing tumor antigen-specific T cells, and reversing T cell exhaustion. Whereas both LIGHT overexpression and anti-CTLA-4 increase tumor-promoting macrophages, the combination eliminates this population. The ability of LIGHT overexpression combined with CTLA-4 inhibition to reverse T cell exhaustion and myeloid cell suppression is supported by analysis of complementary patient cohorts and has strong clinical relevance, especially given that liver metastases contribute to immunotherapy resistance across various cancer types.

Long-term survival of glioblastoma multiforme (GBM) remains challenging, spurring the development of novel therapies such as oncolytic virus therapy. While oncolytic virus shows promise in clinical trials, many patients do not respond to this therapy. Here, we perform a CRISPR screening and identify the non-canonical BRG1/BRM-associated factor (ncBAF) complex as a pivotal tumor-intrinsic factor for oncolytic virotherapy resistance. Knocking out the ncBAF-specific subunit bromodomain-containing protein 9 (BRD9) markedly augments the oncolytic efficacy of oncolytic herpes simplex virus type 1 (oHSV1) and enhances antitumor immunity. Mechanistically, BRD9 binds to RELA and potentiates the expression of downstream antiviral genes. Notably, the application of BRD9 inhibitor (IBRD9) significantly enhances the oncolytic activity of oHSV1 in various GBM models. Moreover, reduced BRD9 levels strongly correlate with improved outcomes in clinical trials of oHSV1. These findings suggest that BRD9 is an attractive target for overcoming the resistance to oHSV1 in glioblastoma treatment.

Pancreatic cancer's aberrant lipid metabolism fuels cell growth, invasion, and metastasis, yet its impact on immune surveillance and immunotherapy is unclear. This study investigated how sterol regulatory element-binding transcription factor 1 (SREBP1)-driven lipid metabolism affects the tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDAC).

The involvement of tumour-resident memory T (TRM) cells in responses to immune checkpoint inhibitors remains unclear. Here, we show that while CD103+CD8 TRM cells are involved in response to PD-1 blockade, CD49a+CD4 TRM cells are required for the response to anti-CTLA-4. Using preclinical mouse models, we demonstrate that the benefits of anti-PD-1 treatment are compromised in animals challenged with anti-CD8 and anti-CD103 blocking antibodies. By contrast, the benefits of anti-CTLA-4 are decreased by anti-CD4 and anti-CD49a neutralizing antibodies. Single-cell RNA sequencing on tumour-infiltrating T-lymphocytes (TIL) reveals a CD49a+CD4 TRM signature, enriched in Ctla-4 transcripts, exacerbated upon anti-CTLA-4. CTLA-4 blockade expands CD49a+CD4 TRM cells and increases tumour-specific CD4-TIL-mediated cytotoxicity. A CD49a+CD4 TRM signature enriched in CTLA-4 and cytotoxicity-linked transcripts is also identified in human TILs. Multiplex immunohistochemistry in a cohort of anti-CTLA-4-plus-anti-PD-1-treated melanomas reveals an increase in CD49a+CD4 T-cell density in pre-treatment tumours, which correlates with higher rates of patient progression-free survival. Thus, CD49a+CD4 TRM cells may correspond to a predictive biomarker of response to combined immunotherapy.

Ovarian cancer is the sixth leading cause of cancer death among American women, with most fatalities attributable to tubo-ovarian high-grade serous carcinoma (HGSC). This malignancy usually develops resistance to conventional chemotherapy, underscoring the need for robust preclinical models to guide the development of novel therapies. Here, we introduce an HGSC mouse model generated via Ovgp1-driven Cre recombinase effecting CRISPR/Cas9-mediated deletion of Trp53, Rb1, and Nf1 tumor suppressors in mouse oviductal epithelium (m-sgPRN model). Cyclin-dependent kinase 12 (CDK12) inactivation-frequently observed in human HGSC-is associated with poorer outcomes, DNA damage accumulation (including tandem duplications), and increased tumor immunogenicity. In our system, coablation of Cdk12 (m-sgPRN;Cdk12KO) recapitulated hallmark features of HGSC, while accelerating tumor progression and reducing survival. In a conventional (Cre-lox-mediated) Trp53/Nf1/Rb1 triple knockout model with concurrent Cdk12 ablation (PRN;Cdk12KO mice), we observed T cell-rich immune infiltrates mirroring those seen clinically. We established both models as subcutaneous or intraperitoneal syngeneic allografts of CDK12-inactivated HGSC that exhibited sensitivity to immune checkpoint blockade. Furthermore, a CRISPR/Cas9 synthetic lethality screen in PRN;Cdk12KO-derived cell lines identified CDK13-an essential paralog of CDK12-as the most depleted candidate, confirming a previously reported synthetic lethal interaction. Pharmacologic CDK13/12 degradation (employing YJ1206) demonstrated enhanced efficacy in cell lines derived from both m-sgPRN;Cdk12KO and PRN;Cdk12KO models. Our results define CDK12 as a key tumor suppressor in tubo-ovarian HGSC and highlight CDK13 targeting as a promising therapeutic approach in CDK12-inactive disease. Additionally, we have established valuable in vivo resources to facilitate further investigation and drug development in this challenging malignancy.

The lack of T cells in tumors is a major hurdle to successful immune checkpoint therapy (ICT). Therefore, therapeutic strategies promoting T cell recruitment into tumors are warranted to improve the treatment efficacy. Here, we report that Fc-optimized anti-cytotoxic T lymphocyte antigen 4 (CTLA-4) antibodies are potent remodelers of tumor vasculature that increase tumor-associated high endothelial venules (TA-HEVs), specialized blood vessels supporting lymphocyte entry into tumors. Mechanistically, this effect is dependent on the Fc domain of anti-CTLA-4 antibodies and CD4+ T cells and involves interferon gamma (IFNγ). Unexpectedly, we find that the human anti-CTLA-4 antibody ipilimumab fails to increase TA-HEVs in a humanized mouse model. However, increasing its Fc effector function rescues the modulation of TA-HEVs, promotes CD4+ and CD8+ T cell infiltration into tumors, and sensitizes recalcitrant tumors to programmed cell death protein 1 (PD-1) blockade. Our findings suggest that Fc-optimized anti-CTLA-4 antibodies could be used to reprogram tumor vasculature in poorly immunogenic cold tumors and improve the efficacy of ICT.

Many metastatic clear cell renal cell carcinomas (ccRCC) are resistant to immune checkpoint inhibitor therapies, however the mechanisms underlying sensitivity or resistance remain incompletely characterised. We demonstrate that ccRCCs in the Vhl/Trp53/Rb1 mutant mouse model are resistant to combined anti-PD-1/anti-CTLA-4 therapy alone and in combination with additional therapeutic agents that reflect current ccRCC clinical trials. However, in some animals in vivo checkpoint therapy allowed isolated splenic T cells to recognise cultured ccRCC cells from the same animal, implicating the tumour microenvironment in suppression of T cell activation. We identified putative immunosuppressive myeloid cell populations with features similar to myeloid cells in the microenvironment of human ccRCC. The expression patterns of immune checkpoint ligands in both the mouse model and in human ccRCC suggests that several checkpoint systems other than PD-1 and CTLA-4 are likely to represent the dominant T cell suppressive forces in ccRCC. Our findings characterise an autochthonous mouse ccRCC model of immune checkpoint inhibitor therapy resistance and pave the way for a systematic functional dissection of the identified potential molecular barriers to effective immune therapy of ccRCC.

Resistance to BRAF and MEK inhibitors (BRAFi/MEKi) in metastatic melanoma frequently results in cross-resistance to immune checkpoint inhibitors (ICI), limiting effective treatment options. However, a subset of BRAFi/MEKi-resistant patients remains responsive to second-line ICI, suggesting heterogeneous underlying resistance mechanisms. This study aimed to explore the tumor immune microenvironment in BRAFi/MEKi-resistant melanoma to uncover factors influencing sensitivity to second-line ICI therapy.

Persisting programmed cell death-1 (PD-1) signaling impairs T cell effector function, which is highly associated with T cell exhaustion and immunotherapy failure. However, the mechanism responsible for PD-1 deubiquitination and T cell dysfunction remains unclear. Here, we show that ubiquitin-specific peptidase 24 (USP24) promotes PD-1 protein stability by removing K48-linked polyubiquitin. Increased interleukin-6 level transcriptionally activates the USP24 expression, which leads to PD-1 stabilization. Furthermore, USP24 deficiency reduces PD-1 levels in CD8+ T cells and attenuates EgfrL858R-driven lung tumorigenesis in Usp24C1695A catalytic deficient mice. Targeting PD-1 stability with the USP24-specific inhibitor USP24-i-101 boosts cytotoxic T cell activity, restrains lung tumor growth, and achieves superior therapeutic effects when combined with anti-CTLA4 immunotherapy. Clinically, patients with lung cancer exhibiting high USP24 expression in tumor-infiltrating CD8+ T cells display exhausted features and show unfavorable responses to immunotherapy. Our findings dissect the mechanism for regulating enhanced PD-1 stability in tumor-infiltrating CD8+ T cells and reveal USP24 as a potential target of antitumor immunotherapy.

Although ACVR2A mutations are prevalent in non-viral hepatocellular carcinomas (HCCs), the underlying mechanism remains unelucidated. Our molecular investigation reveals that ACVR2A impairment induces hyperglycolysis through the inactivation of the SMAD signaling pathway. Using syngeneic transplantation models and human clinical samples, we clarify that ACVR2A-deficient HCC cells produce and secrete lactate via the upregulation of lactate dehydrogenase A (LDHA) and monocarboxylate transporter 4 (MCT4) expression levels, which promotes regulatory T (Treg) cell accumulation and then acquires resistance to immune checkpoint inhibitors. Remarkably, genetic knockdown and pharmacological inhibition of MCT4 ameliorate the high-lactate milieu in ACVR2A-deficient HCC, resulting in the suppression of intratumoral Treg cell recruitment and the restoration of the sensitivity to PD-1 blockade. These findings furnish compelling evidence that lactate attenuates anti-tumor immunity and that therapeutics targeting this pathway present a promising strategy for mitigating immunotherapy resistance in ACVR2A-deficient HCC.