InVivoPlus anti-mouse CTLA-4 (CD152)

Background: Immune checkpoint inhibitors are ineffective in the majority of colorectal cancers (CRCs) that are microsatellite stable. However, the underlying reasons for their unresponsiveness and mechanisms of immune evasion are poorly understood. In the present study, we aimed to elucidate the mechanisms underlying the immune evasion driven by CRC cells. Methods: We performed single-cell RNA sequencing of tumor tissues from 30 CRC patients and syngeneic mice implanted with transformation-related protein 53 (Trp53) knockout CT26 cells. Gene expression and correlations of individual tumor microenvironment (TME) components were analyzed, and their functional significance was investigated using syngeneic mouse models and cell line co-culture experiments. Results: CCAAT enhancer-binding protein beta (CEBPB) expression was increased in tumor protein 53 (TP53)-mutated CRCs. We confirmed that wild-type TP53 negatively regulated CEBPB expression in CRC cell lines. CEBPB expression was associated with decreased intratumoral T cell infiltration and negatively impacted survival in CRC patients. In the intercellular correlation analysis of gene expression, tumor epithelial cell CEBPB expression was significantly correlated with cytotoxic T-lymphocyte associated protein 4 (CTLA4) expression in T cells, especially in regulatory and exhausted T cells. Cebpb overexpression promoted tumor growth in the immunocompetent syngeneic mouse models, which was accompanied by increased CTLA-4 expression in tumor-infiltrating CD4+ T cells. In vitro co-culture experiments also showed that tumor cell CEBPB overexpression increased CTLA4 in T cells. Conclusions: Tumor cell CEBPB expression, up-regulated by TP53 mutation, can increase CTLA4 expression in T cells and negatively affect patient outcomes. These findings suggested a central role of tumor cell CEBPB in shaping an immunosuppressive TME.

Interleukin-2 (IL-2) variants with increased CD25 dependence that selectively expand Foxp3+ regulatory T (TR) cells are in clinical trials for treating inflammatory diseases. Using an Fc-fused IL-2 mutein (Fc.IL-2 mutein) we developed that prevents diabetes in non-obese diabetic (NOD) mice, we show that Fc.IL-2 mutein induced an activated TR population with elevated proliferation, a transcriptional program associated with Stat5- and T cell receptor-dependent gene modules, and high IL-10 and CTLA-4 expression. Increased IL-10 signaling limited surface major histocompatibility complex class II upregulation during conventional dendritic cell (cDC) maturation, while increased CTLA-4-dependent transendocytosis led to the transfer of CD80 and CD86 co-stimulatory ligands from maturing cDCs to TR cells. In NOD mice, Fc.IL-2 mutein treatment promoted the suppression of cDCs in the inflamed pancreas and pancreatic lymph nodes, resulting in T cell anergy. Thus, IL-2 mutein-expanded TR cells have enhanced functional properties and restrict cDC function, offering promise for targeted immunotherapy use in autoimmune disease.

Pancreatic ductal adenocarcinoma (PDAC) is characterised by immune evasion that contribute to poor prognosis. Cancer-associated fibroblasts (CAFs) play a pivotal role in orchestrating the PDAC tumour microenvironment. We investigated the role of CAF-derived extracellular vesicle (EV)-packaged long non-coding RNAs (lncRNAs) in immune evasion and explored gene therapy using engineered EVs loading small interfering RNAs (siRNAs) as a potential therapeutic strategy. Our findings highlight the significance of EV-packaged lncRNA RP11-161H23.5 from CAF in promoting PDAC immune evasion by downregulating HLA-A expression, a key component of antigen presentation. Mechanistically, RP11-161H23.5 forms a complex with CNOT4, a subunit of the mRNA deadenylase CCR4-NOT complex, enhancing the degradation of HLA-A mRNA by shortening its poly(A) tail. This immune evasion mechanism compromises the anti-tumour immune response. To combat this, we propose an innovative approach utilising engineered EVs as natural and biocompatible nanocarriers for siRNA-based gene therapy and this strategy holds promise for enhancing the effectiveness of immunotherapy in PDAC. Overall, our study sheds light on the critical role of CAF-derived EV-packaged lncRNA RP11-161H23.5/CNOT4/HLA-A axis in PDAC immune evasion and presents a novel avenue for therapeutic intervention.

Programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) blockade has become a mainstay of cancer immunotherapy. Targeting the PD-1/PD-L1 axis with small molecules is an attractive approach to enhance antitumor immunity. Here, we identified a natural marine product, benzosceptrin C (BC), that enhances the cytotoxicity of T cells to cancer cells by reducing the abundance of PD-L1. Furthermore, BC exerts its antitumor effect in mice bearing MC38 tumors by activating tumor-infiltrating T cell immunity. Mechanistic studies suggest that BC can prevent palmitoylation of PD-L1 by inhibiting DHHC3 enzymatic activity. Subsequently, PD-L1 is transferred from the membrane to the cytoplasm and cannot return to the membrane via recycling endosomes, triggering lysosome-mediated degradation of PD-L1. Moreover, the combination of BC and anti-CTLA4 effectively enhances antitumor T cell immunity. Our findings reveal a previously unrecognized antitumor mechanism of BC and represent an alternative immune checkpoint blockade (ICB) therapeutic strategy to enhance the efficacy of cancer immunotherapy.