Human Programmed Death-ligand 1 Research Articles

Polymer-based antibody mimetics (iBodies) target human PD-L1 and function as a potent immune checkpoint blocker

Immune checkpoint blockade (ICB) using monoclonal antibodies against programmed cell death protein 1 (PD-1) or programmed death-ligand 1 (PD-L1) is the treatment of choice for cancer immunotherapy. However, low tissue permeability, immunogenicity, immune-related adverse effects, and high cost could be possibly improved using alternative approaches. On the other hand, synthetic low-molecular-weight (LMW) PD-1/PD-L1 blockers have failed to progress beyond in vitro studies, mostly due to low binding affinity or poor pharmacological characteristics resulting from their limited solubility and/or stability.Here, we report the development of polymer-based anti-human PD-L1 antibody mimetics (α-hPD-L1 iBodies) by attaching the macrocyclic peptide WL12 to a N-(2-hydroxypropyl)methacrylamide copolymer. We characterized the binding properties of iBodies using surface plasmon resonance, enzyme-linked immunosorbent assay, flow cytometry, confocal microscopy, and a cellular ICB model. We found that the α-hPD-L1 iBodies specifically target human PD-L1 (hPD-L1) and block the PD-1/PD-L1 interaction in vitro, comparable to the atezolizumab, durvalumab, and avelumab licensed monoclonal antibodies targeting PD-L1. Our findings suggest that iBodies can be used as experimental tools to target hPD-L1 and could serve as a platform to potentiate the therapeutic effect of hPD-L1-targeting small molecules by improving their affinity and pharmacokinetic properties.

Abstract 4094: Immune modulatory cancer vaccines against IDO1 and PD-L1 trigger distinct pathways and cooperatively reduce tumor growth in preclinical models

Abstract While immune checkpoint inhibitors have shown clinical efficacy in many cancers, drug and immune resistance remain challenging. Indoleamine 2,3-dehydrogenase (IDO1) and Programmed Death Ligand 1 (PD-L1) both contribute to immunosuppression, leading to immune escape and cancer progression. In this context, vaccination to promote T-cell immunity against IDO1+ and PD-L1+ cells is an attractive strategy that demonstrated encouraging clinical results in melanoma (Kjeldsen et al. Nat Med 2021). Our study aims to further evaluate the efficacy and mode of action of combined IDO1 and PD-L1 peptide vaccines. Mice injected with tumor cells and treated with IDO1 or PD-L1 peptides were monitored for tumor growth. Vaccine activity was determined by IFNγ Elispot assay. Gene expression analysis was performed on tumors using Nanostring nCounter PanCancer IO360 Panel. IDO1 and PD-L1 expression were also examined via multiplex immunofluorescence in a human tumor tissue microarray (TMA) panel. Human IDO1 and PD-L1 specific CD4+ T cell clones were isolated and expanded from melanoma patients treated with IDO1/IO102 or PD-L1/IO103 peptide vaccines in combination with aPD1 therapy. Immunofluorescence analysis of murine tumor sections showed expression of IDO1 and PD-L1 by different cell populations. Vaccination against each target led to expansion of specific T cells in splenocytes and reduced tumor growth in MC38 and CT26 models. Combining IDO1 and PD-L1 treatments further enhanced the anti-tumor response. Gene expression analysis of tumors revealed distinct signatures following monotherapy and combination treatments. While PD-L1 vaccination predominantly enhanced the cytotoxic effector T cell function in the tumor microenvironment (TME) and concomitantly increased gene signatures associated with enhanced activation of T effector cells, IDO1 vaccine primarily exerted its effect via reduction in the immune suppression loop. TMA analysis of IDO1+ and PD-L1+ cells in human tumors also revealed that they represent largely distinct cell populations. Lastly, IDO1 and PDL1-specific CD4+ T cell clones from melanoma patients treated with IO102-IO103 vaccine could selectively target cells differentially expressing IDO1 or PDL1. Our data collectively show that cells expressing IDO1 and PD-L1 represent distinct populations in the TME thus targetable by the IDO1-PD-L1 vaccination approach. The vaccines targeting IDO1 and PD-L1 cooperatively reduce tumor outgrowth, and each contributes to the anti-tumor effect through distinct molecular programs regulating immunosuppression in the TME and T cell activation respectively. These data are supported by ex vivo functional assays using target specific T cells from vaccinated patients. Altogether, our data support the use of a dual antigen approach to reduce the immunosuppression and enhance anti-tumor effect. Citation Format: Marion Chapellier, Evelina Martinenaite, Preeyam Patel, Lea Svendsen, Shamaila Munir Ahmad, Hannah Jorinde Glöckner, Marco Carretta, Erika Sutanto-Ward, James DuHadaway, Souvik Dey, Shih-Chun Shen, Dema Ghaban, Marcos Iglesias, Megan Biller, Inés Lecoq, Alexander J. Muller, Mads Hald Andersen, Ayako Wakatsuki Pedersen. Immune modulatory cancer vaccines against IDO1 and PD-L1 trigger distinct pathways and cooperatively reduce tumor growth in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4094.

The expression and significance of PD-L1 in condyloma acuminatum.

It has been reported that programmed death-ligand 1 (PD-L1) is highly expressed in cells during viral infection, which helps the virus escape host immunity. However, the relationship between human papillomavirus (HPV) and PD-L1 in condyloma acuminatum and whether they participate in immunosuppression have not been reported. In this paper, we aimed to explore the expression and significance of PD-L1 in condyloma acuminatum. The expression of PD-L1 in the wart of condyloma acuminatum patients and the foreskin of healthy individuals was evaluated. Lentivirus transfection was used to introduce the HPV11-E7 gene into HaCaT cells to investigate whether HPV infection could affect the expression of PD-L1. The successfully constructed HPV11-E7 HaCaT cells were cocultured with Jurkat cells, and Jurkat cell apoptosis and proliferation as well as the Jurkat cell cycle were evaluated by flow cytometry and cell counting kit-8 (CCK-8) assays. PD-L1 was highly expressed in keratinocytes of genital warts. Through the construction of a cell model, we found that HPV11-E7 could upregulate the expression of PD-L1 in HaCaT cells. Furthermore, HPV11-E7 HaCaT cells can promote the apoptosis of Jurkat cells, inhibit the proliferation of Jurkat cells and mediate the cell cycle arrest of Jurkat cells through the PD-1/PD-L1 signalling pathway. HPV infection may upregulate PD-L1 expression in the keratinocytes of genital warts and participate in the inhibition of local T-cell function.

Abstract 5199: B7-H3 & PD-L1 double-humanized BALB/c mouse: a novel animal model for preclinical studies of human B7-H3 antibodies or bispecific antibodies

Abstract Immune checkpoint molecule B7-H3, also known as CD276, is a member of the B7-CD28 family of immunomodulatory proteins. It is a type I membrane protein with sequence similarities to the extracellular domain of programmed death-ligand 1 (PD-L1). B7-H3 is highly expressed in most human cancers, but has limited distribution in normal tissues, remaining elusive of its receptor. Due to its promising safety as a dominant tumor target, various strategies have been developed to modulate the effect of B7-H3 via monoclonal antibodies, bispecific antibodies, ADC, or CAR-T. To study the effect of these therapies in an immunocompetent mouse model, we established a double humanized B7-H3 and PD-L1 mouse model on BALB/c background (BALB/c-hB7-H3/hPD-L1). In this model, the extracellular domain of murine fragments was replaced by the human counterparts while the trans-membrane and cytoplasmic domain were kept intact. When engrafted with CT26 colon cancer cells, which stably overexpress human B7-H3 and PD-L1 while endogenous murine counterparts were knocked out, the tumor growth was inhibited certain degree by anti-B7-H3 antibody (8H9 Biosimilar, 20mpk, TGI=18.56%) treatment while inhibited significantly after the monotherapy of anti-PD-L1 (Tecentriq, 3 mpk, TGI=55.89%, p<0.001). The same dosage combination of anti-B7-H3 and anti-PD-L1 had a significant inhibition on tumor growth (TGI=76.85%, p<0.001), and had a synergistic effect (CDI<0.7) compared with the monotherapy. Analysis of tumor-infiltrating lymphocytes (TILs) at the end of the efficacy study showed that the proportion of CD45+ immune cells was significantly increased in all of the treated groups. The NK cells were significantly increased and the Treg cells were significantly decreased especially in the combined treatment group. Based on the above, the B7-H3 and PD-L1 double humanized mouse model is suitable for the pre-clinical evaluation of mono or combined immune checkpoint blockade with anti-human B7-H3 and PD-L1 therapy. Citation Format: Shiying Guo, Lingyu Song, Xin Qin, Jianming Xu, Hongyan Sun, Cunxiang Ju, Hongyu Wang, Santi Suryani Chen, Zhiying Li, Mark Wade Moore, Jing Zhao, Xiang Gao. B7-H3 & PD-L1 double-humanized BALB/c mouse: a novel animal model for preclinical studies of human B7-H3 antibodies or bispecific antibodies. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5199.

Active immunization with a structurally aggregated PD-L1 antigen breaks T and B immune tolerance in non-human primates and exhibits in vivo anti-tumoral effects in immunocompetent mouse tumor models

Despite the clinical success of the programmed death ligand 1 (PD-L1) blocking therapy in cancer treatment, only a subset of patients exhibits durable responses, therefore further exploration of other immunotherapeutic alternatives are needed. This paper reported the development of the PKPD-L1Vac vaccine, a new protein vaccine candidate that uses aluminum phosphate as an adjuvant and as an antigen the extracellular domain of human PD-L1 fused to a 47 amino-terminal portion of the LpdA protein from N. meningitides (PKPD-L1). The PKPD-L1 antigen has different physical and biological characteristics than those found in the natural molecule and in others PD-L1 vaccine candidates. The quimeric protein has a reduced binding capacity to the PD-1 and CD80 receptors to decrease their pro-tumoral activity. Besides, the distinctive feature of the PKPD-L1 polypeptide to be structurally aggregated could be desirable for its immunogenic properties. PKPD-L1Vac elicited anti-PD-L1-specific IgG antibodies and T lymphocyte-mediated immunity in mice and non-human primates. The vaccine administration demonstrated antitumor activity on CT-26 and B16–F10 primary tumor models in mice. Moreover, the immunization with PKPD-L1Vac increased the tumor-infiltrating lymphocytes and decreased the proportion of CD3+CD8+PD1+high anergic T cells in CT-26 tumor tissues, suggesting that the vaccine may remodel the tumor microenvironment. In summary, the PKPD-L1Vac vaccine exhibits very promising preclinical results and deserves to move forward to a phase I clinical trial.

Intra-articular delivery of AAV vectors encoding PD-L1 attenuates joint inflammation and tissue damage in a mouse model of rheumatoid arthritis.

Rheumatoid arthritis (RA) is the most common form of autoimmune inflammatory arthritis. Intra-articular gene delivery to block proinflammatory cytokines has been studied in pre-clinical models and human clinical trials. It has been demonstrated that the level of programmed death-ligand 1 (PD-L1) is associated with rheumatoid arthritis (RA). This study examined the therapeutic role of PD-L1 by intra-articular delivery via adeno-associated virus (AAV) vectors in the mouse collagen-induced arthritis (CIA) model. Mice were intra-articularly injected with AAV5 vectors encoding human PD-L1 on day 0 and immunized with bovine type II collagen to induce CIA simultaneously. On day 49 post AAV administration, joints were collected for histo-pathological and cytokine analysis. Additionally, the systemic impacts of intra-articular injection of AAV5/PD-L1 vectors were also studied. To study the therapeutic effect of PD-L1, AAV5/PD-L1 vectors were administered into the joints of RA mice on day 21. After administration of AAV5/PD-L1 vectors, strong PD-L1 expression was detected in AAV transduced joints. Joints treated with PD-L1 at the time of arthritis induction exhibited significantly less swelling and improved histopathological scores when compared to untreated joints. Additionally, the infiltration of T cells and macrophages was decreased in joints of CIA mice that received AAV5/PD-L1 vectors (P<0.05). The levels of pro-inflammatory cytokines, including IL-1, IL-6, IL-17 and TNFα, were lower in AAV5/PD-L1 treated than untreated joints (P<0.05). Furthermore, the administration of AAV5/PD-L1 vectors into the joints of CIA mice did not impact serum cytokine levels and the antibody titers to type II collagen. Biodistribution of AAV vectors after intra-articular injection showed undetectable AAV genomes in other tissues except for a low level in the liver. Similar to the results of AAV5/PD-L1 vector administration on day 0, decreased joint swelling and lower histopathological damage were observed in joints treated with AAV5/PD-L1 vectors on day 21. The results from this study demonstrate that local AAV mediated PD-L1 gene delivery into the joints is able to prevent the development and block the progression of arthritis in CIA mice without impacting systemic immune responses. This study provides a novel strategy to effectively treat inflammatory joint diseases using local AAV gene therapy by interference with immune checkpoint pathways.

Construction of an Iodine-Labeled CS1001 Antibody for Targeting PD-L1 Detection and Comparison with Low-Molecular-Peptide Micro-PET Imaging.

Programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1), the research focus in immune checkpoint regulation, play an important role in tumor immunotherapy. Inhibitors of this pathway are also the focus of tumor immunotherapy research. The PD-1/PD-L1 pathway can be blocked by selective binding to PD-L1. Clinical trials have been conducted in a variety of patients with advanced solid tumors. CS1001 is a high-affinity humanized full-length anti-PD-L1 monoclonal antibody with great clinical significance. We constructed a PD-L1-targeted radioactive molecular probe, 124/125I-labeled full-length antibody CS1001, and evaluated its binding specificity and targeting ability to PD-L1 in tumor cells and tumor models. Additionally, a comparison study with 68Ga-WL12, a PD-L1 targeting peptide, was conducted. The binding potency of 125I-CS1001 to human PD-L1 was evaluated by enzyme-linked immunosorbent assay (ELISA), and the Kd value was 52.1 ± 19.3 nM. The cellular uptake of 125I-CS1001 was examined in Chinese hamster ovary cells (CHO) and CHO expressing human PD-L1 (CHO-hPD-L1). At 2 h, the uptake values of 125I-CS1001 in CHO-hPD-L1 without blocking and in the presence of 0.1 mg non-radiolabeled CS1001 were 3.60 ± 0.08 and 0.09 ± 0.005 (%AD/2 × 105 cells, p < 0.001). Micro-PET imaging was performed between 8 to 192 h after injection of 124I-CS1001 into normal KM mice and CHO-hPD-L1 and HeLa tumor models. The standard uptake value (SUV) of relevant organs in PET images was calculated by drawing regions of interest (ROI). SUVmean of CHO-hPD-L1 tumors was significantly higher than that of HeLa tumors at 48 h (1.98 ± 0.04 vs 0.73 ± 0.14, p = 0.005). The SUVmean of 124I-CS1001 in CHO-hPD-L1 tumors at 48 h was higher than that of 68Ga-WL12 in CHO-hPD-L1 tumors at 0.5 h (1.98 ± 0.04 vs 1.09 ± 0.1 SUVmean, p = 0.007). In conclusion, this work provides a new method for monitoring and evaluating the in vivo expression of PD-L1 in tumors.

A novel anti-PD-L1/IL-15 immunocytokine overcomes resistance to PD-L1 blockade and elicits potent antitumor immunity

Despite the demonstrated immense potential of immune checkpoint inhibitors in various types of cancers, only a minority of patients respond to these therapies. Immunocytokines designed to deliver an immune-activating cytokine directly to the immunosuppressive tumor microenvironment (TME) and block the immune checkpoint simultaneously may provide a strategic advantage over the combination of two single agents. To increase the response rate to checkpoint blockade, in this study, we developed a novel immunocytokine (LH01) composed of the antibody against programmed death-ligand 1 (PD-L1) fused to interleukin (IL)-15 receptor alpha-sushi domain/IL-15 complex. We demonstrate that LH01 efficiently binds mouse or human PD-L1 and maintains IL-15 stimulatory activity. In syngeneic mouse models, LH01 showed improved antitumor efficacy and safety versus anti-PD-L1 plus LH02 (Fc-sushi-IL15) combination and overcame resistance to anti-PD-L1 treatment. Mechanistically, the dual anti-immunosuppressive function of LH01 activated both the innate and adaptive immune responses and induced a favorable and immunostimulatory TME. Furthermore, combination therapy with LH01 and bevacizumab exerts synergistic antitumor effects in an HT29 colorectal xenograft model. Collectively, our results provide supporting evidence that fusion of anti-PD-L1 and IL-15 might be a potent strategy to treat patients with cold tumors or resistance to checkpoint blockade.

FN3 linked nanobubbles as a targeted contrast agent for US imaging of cancer-associated human PD-L1.

PD-L1 (programmed death-ligand 1) targeted therapies may be useful for several cancers. The use of non-invasive diagnostic and prognostic molecular imaging platforms could improve clinical assessment of PD-L1 tumor status during these therapies. Contrast enhanced ultrasound molecular imaging (CE-USMI) techniques may offer versatile and cost-effective ways to detect and quantify the expression levels of cellular targets in vivo. However, conventional use of microbubbles as a blood pool contrast agent for CE-USMI is limited to accessing intravascular biomarkers rather than reflecting the tumor molecular status. Using a microfluidic based reconstruction process we therefore developed ultra-stable nanobubbles (NBs) as a contrast agent for molecular imaging of vascular and extravascular cell surface markers. We then functionalized these NBs by covalently linking to nanobody (FN3hPD-L1) targeting human (h)PD-L1 to measure the expression of human PD-L1 in the tumor microenvironment (TME) in vivo. We showed the specific binding of hPD-L1 targeted NBs in cell culture, and in xenografted mouse models of hPD-L1 expressing CT26 tumors. CE-USMI of hPD-L1 in the TME in vivo showed ~3-fold increase in contrast signal compared to non-targeted NBs. Overall, in vivo use of CE-USMI with hPD-L1 targeted NBs has the potential for clinical translation and imaging of human cancers during immunotherapy, and for prognostic evaluation of patient response to PD-L1 targeted immunotherapy.

Interferon‐γ Induced PD‐L1 Expression in Ovarian Cancer Cells is Regulated by IRF1 Signaling

The immune checkpoint programmed death ligand‐1 (PD‐L1) is highly expressed in cancer cells, including ovarian cancer (OC) cells. High PD‐L1 expression in ovarian cancer correlates with poor prognosis, but the mechanisms that regulate the PD‐L1 expression in OC remain poorly understood. We have recently shown that IFNγ induces the PD‐L1 expression in OC cells, resulting in their increased proliferation and invasion. Here, we show that the IFNγ‐induced PD‐L1 expression in OC cells is associated with increased levels of STAT1, Tyr‐701 pSTAT1 and Ser‐727 pSTAT1 in OC cells. JAK1 and STAT1 suppression significantly decreases the IFNγ‐induced PD‐L1 mRNA and protein levels in OC cells. In addition, IRF1 suppression significantly decreases the IFNγ‐induced gene and protein levels of PD‐L1, indicating that the IFNγ‐induced PD‐L1 expression in OC cells is dependent on IRF1 signaling. Chromatin immunoprecipitation data demonstrate that IFNγ induces occupancy of STAT1, Ser‐727 pSTAT1 and IRF1 at STAT1 and IRF1 binding sites in human PD‐L1 promoter. Together, these results show that the IFNγ‐induced PD‐L1 expression in OC cells is regulated by IRF1/JAK1/STAT1 signaling, and suggest that targeting the IRF1/JAK1/STAT1 pathway may provide leverage to regulate the PD‐L1 levels in ovarian cancer.

Pyrazolones as inhibitors of immune checkpoint blocking the PD-1/PD-L1 interaction

Immuno-therapy has become a leading strategy to fight cancer. Over the past few years, immuno-therapies using checkpoint inhibitor monoclonal antibodies (mAbs) against programmed death receptor 1 (PD-1) and programmed death ligand 1 (PD-L1) have demonstrated improved survival compared with chemotherapy. We describe the microwave-assisted synthesis and the characterization of an innovative series of synthetic compounds endowed with nanomolar activity against PD-L1. The properties of the compounds were characterized using several biophysical techniques including microscale thermophoresis (MST) and fluorescence resonance energy transfer (FRET) measurements. A few small molecules demonstrated a high affinity for human PD-L1, potently disrupted the PD-L1:PD-1 interaction and inhibited Src homology region 2 domain-containing phosphatase (SHP2) recruitment to PD-1. More than 30 molecules from the pyrazolone family have been synthesized and 5 highly potent “PD-L1 silencing compounds” have been identified, based on in vitro measurements. Structure-activity relationships have been defined and ADME properties were evaluated. The phenyl-pyrazolone unit offers novel perspectives to design PD-L1-targeting agents, potentially useful to combat cancer and other pathologies implicating the PD-1/PD-L1 checkpoint.

A novel PD-L1-targeted shark VNAR single-domain-based CAR-T cell strategy for treating breast cancer and liver cancer

Chimeric antigen receptor (CAR)-T cell therapy shows excellent potency against hematological malignancies, but it remains challenging to treat solid tumors, mainly because of a lack of appropriate antigenic targets and an immunosuppressive tumor microenvironment (TME). The checkpoint molecule programmed death-ligand 1 (PD-L1) is widely overexpressed in multiple tumor types, and the programmed death-ligand 1 (PD-1)/PD-L1 interaction is a crucial mediator of immunosuppression in the TME. Here we constructed a semi-synthetic shark VNAR phage library and isolated anti-PD-L1 single-domain antibodies. Among these VNARs, B2 showed cross-reactivity to human, mouse, and canine PD-L1, and it partially blocked the interaction of human PD-1 with PD-L1. CAR (B2) T cells specifically lysed human breast cancer and liver cancer cells by targeting constitutive and inducible expression of PD-L1 and hindered tumor metastasis. Combination of PD-L1 CAR (B2) T cells with CAR T cells targeted by GPC3 (a liver cancer-specific antigen) regresses liver tumors in mice. We concluded that PD-L1-targeted shark VNAR single-domain-based CAR-T therapy is a novel strategy to treat breast and liver cancer. This study provides a rationale for potential use of PD-L1 CAR-T cells as a monotherapy or in combination with a tumor-specific therapy in clinical studies.

Dual-sgRNA CRISPR/Cas9 knockout of PD-L1 in human U87 glioblastoma tumor cells inhibits proliferation, invasion, and tumor-associated macrophage polarization

Programmed death ligand 1 (PD-L1) plays a key role in glioblastoma multiforme (GBM) immunosuppression, vitality, proliferation, and migration, and is therefore a promising target for treating GBM. CRISPR/Cas9-mediated genomic editing can delete both cell surface and intracellular PD-L1. This systemic deliverable genomic PD-L1 deletion system can be used as an effective anti-GBM therapy by inhibiting tumor growth and migration, and overcoming immunosuppression. To target PD-L1 for CRISPR/Cas9 gene editing, we first identified two single guide RNA (sgRNA) sequences located on PD-L1 exon 3. The first sgRNA recognizes the forward strand of human PD-L1 near the beginning of exon 3 that allows editing by Cas9 at approximately base pair 82 (g82). The second sgRNA recognizes the forward strand of exon 3 that directs cutting at base pair 165 (g165). A homology-directed repair template (HDR) combined with the dual-sgRNAs was used to improve PD-L1 knockout specificity and efficiency. sgRNAs g82 and g165 were cloned into the multiplex CRISPR/Cas9 assembly system and co-transfected with the HDR template in human U87 GBM cells (g82/165 + HDR). T7E1 analysis suggests that the dual-sgRNA CRISPR/Cas9 strategy with a repair template was capable of editing the genomic level of PD-L1. This was further confirmed by examining PD-L1 protein levels by western blot and immunofluorescence assays. Western blot analysis showed that the dual-sgRNAs with the repair template caused a 64% reduction of PD-L1 protein levels in U87 cells, while immunostaining showed a significant reduction of intracellular PD-L1. PD-L1 deletion inhibited proliferation, growth, invasion and migration of U87 cells, indicating intracellular PD-L1 is necessary for tumor progression. Importantly, U87 cells treated with g82/165 + HDR polarized tumor-associated macrophages (TAM) toward an M1 phenotype, as indicated by an increase in TNF-α and a decrease in IL-4 secretions. This was further confirmed with flow cytometry that showed an increase in the M1 markers Ly6C + and CD80 +, and a decrease in the M2 marker CD206 + both in vitro and in vivo. Utilizing dual-sgRNAs and an HDR template with the CRISPR/Cas9 gene-editing system is a promising avenue for the treatment of GBM.

PD-L1 promotes myofibroblastic activation of hepatic stellate cells by distinct mechanisms selective for TGF-β receptor I versus II.

SUMMARYIntrahepatic cholangiocarcinoma (ICC) contains abundant myofibroblasts derived from hepatic stellate cells (HSCs) through an activation process mediated by TGF-β. To determine the role of programmed death-ligand 1 (PD-L1) in myofibroblastic activation of HSCs, we disrupted PD-L1 of HSCs by shRNA or anti-PD-L1 antibody. We find that PD-L1, produced by HSCs, is required for HSC activation by stabilizing TGF-β receptors I (TβRI) and II (TβRII). While the extracellular domain of PD-L1 (amino acids 19–238) targets TβRII protein to the plasma membrane and protects it from lysosomal degradation, a C-terminal 260-RLRKGR-265 motif on PD-L1 protects TβRI mRNA from degradation by the RNA exosome complex. PD-L1 is required for HSC expression of tumor-promoting factors, and targeting HSC PD-L1 by shRNA or Cre/loxP recombination suppresses HSC activation and ICC growth in mice. Thus, myofibroblast PD-L1 can modulate the tumor microenvironment and tumor growth by a mechanism independent of immune suppression.

Engineered mRNA-expressed bispecific antibody prevent intestinal cancer via lipid nanoparticle delivery

ABSTRACT The potential of antibodies, especially for the bispecific antibodies, are limited by high cost and complex technical process of development and manufacturing. A cost-effective and rapid platform for the endogenous antibodies expression via using the in vitro transcription (IVT) technique to produce nucleoside-modified mRNA and then encapsulated into lipid nanoparticle (LNP) may turn the body to a manufactory. Coinhibitory pathway of programmed death ligand 1 (PD-L1) and programmed cell death protein 1 receptor (PD-1) could suppress the T-cell mediated immunity. We hypothesized that the coblocking of PD-L1 and PD-1 via bispecific antibodies may achieve more potential antitumor efficacies compare with the monospecific ones. Here, we described the application of mRNA to encode a bispecific antibody with ablated Fc immune effector functions that targets both human PD-L1 and PD-1, termed XA-1, which was further assessed the in vitro functional activities and in vivo antitumor efficacies. The in vitro mRNA-encoded XA-1 held comparable abilities to fully block the PD-1/PD-L1 pathway as well as to enhance functional T cell activation compared to XA-1 protein from CHO cell source. Pharmacokinetic tests showed enhanced area under curve (AUC) of mRNA-encoded XA-1 compared with XA-1 at same dose. Chronic treatment of LNP-encapsulated XA-1 mRNA in the mouse tumor models which were reconstituted with human immune cells effectively induced promising antitumor efficacies compared to XA-1 protein. Current results collectively demonstrated that LNP-encapsulated mRNA represents the viable delivery platform for treating cancer and hold potential to be applied in the treatment of many diseases. Abbreviations: IVT: in vitro transcription; LNP: lipid nanoparticle; hPD-1: human PD-1; hPD-L1: human PD-L1; ITS-G: Insulin-Transferrin-Selenium; Pen/Strep: penicillin-streptomycin; FBS: fetal bovine serum; TGI: tumor growth inhibition; IE1: cytomegalovirus immediate early 1; SP: signal peptide; hIgLC: human immunoglobulin kappa light chain; hIgHC: human IgG1 heavy chain; AUC: area under the curve; Cl: serum clearance; Vss: steady-state distributed volume; MLR: mixed lymphocyte reaction.

IMMU-37. DISRUPTION OF PD-L1 BY ENHANCED TWO-SGRNAS CRISPR/CAS9 IN TREATMENT OF GLIOBLASTOMA

Abstract Anti-glioblastoma multiform (GBM) immunotherapy poses a great challenge due to immunosuppressive brain tumor environments and the blood brain barrier (BBB). Programmed death ligand 1 (PD-L1) plays a key role in GBM immunosuppression, vitality, proliferation, and migration. Targeting PD-L1 for immunotherapy is a promising new avenue for treating GBM. CRISPR/Cas9 gene editing can be used to knockout both membrane and cytoplasmic PD-L1, leading to an enhanced immunotherapeutic strategy. We identified two sgRNA sequences located on PD-L1 exon 3. The first sgRNA recognized the forward strand of human PD-L1 near the beginning of exon 3 and cuts at approximately base pair 82 (g82). The second sgRNA recognized the reverse strand of exon 3 and cuts at base pair 165 (g165). Two sgRNAs, g82 and g165, created an 83bp deletion in PD-L1 genomic sequence. Two sgRNAs combination with a homology-directed repair template (HDR) was designed to enhance PD-L1 knockout specificity and efficiency. Both g82 and g165 were cloned into one CRISPR/Cas9 plasmid, and was co-transfected with HDR. GFP tagged CRISPR/Cas9 plasmid containing of g82 and g165 (Cas9-g82/165) was loaded into Rhodamine labeled nanoparticles (Cas9-g82/165-NPs) and then treated to GBM U87 cells. The enhanced intracellular uptake and transfection of Cas9-g82/165-NPs were detected by a fluorescence microscopy. T7E1, qRT-PCR and western blot analysis determined that the dual sgRNA CRISPR/Ca9 system knocked out both endogenous (80%) and exogenous (64%) PD-L1 in U87 cells and PD-L1 overexpression U87 cells, respectively. Deletion of PD-L1 reduced U87 migration and proliferation, while PD-L1 overexpression promoted tumor growth and tumor-associated macrophage polarization. Together, deletion of both membrane and cytoplasmic PD-L1 altered the PD-L1-associated immunosuppressive environment and prevented tumor progression and migration. Thus, two-sgRNAs CRISPR/Cas9 gene-editing system is a promising avenue for anti-GBM immunotherapy.

Development of a novel humanized mouse model for improved evaluation of in vivo anti-cancer effects of anti-PD-1 antibody.

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of cancer in the clinic. Further discovery of novel drugs or therapeutic protocols that enhance efficacy requires reliable animal models that recapitulate human immune responses to ICI treatment in vivo. In this study, we utilized an immunodeficient NOG mouse substrain deficient for mouse FcγR genes, NOG-FcγR−/− mice, to evaluate the anti-cancer effects of nivolumab, an anti-programmed cell death-1 (PD-1) antibody. After reconstitution of human immune systems by human hematopoietic stem cell transplantation (huNOG-FcγR−/− mice), four different programmed death-ligand 1 (PD-L1)-positive human cancer cell lines were tested. Among them, the growth of three cell lines was strongly suppressed by nivolumab in huNOG-FcγR−/− mice, but not in conventional huNOG mice. Accordingly, immunohistochemistry demonstrated the enhanced infiltration of human T cells into tumor parenchyma in only nivolumab-treated huNOG-FcγR−/− mice. Consistently, the number of human T cells was increased in the spleen in huNOG-FcγR−/− mice by nivolumab but not in huNOG mice. Furthermore, human PD-L1 expression was strongly induced in the spleen of huNOG-FcγR−/− mice. Collectively, our results suggest that the anti-cancer effects of anti-PD-1 antibodies can be detected more clearly in NOG-FcγR−/− mice than in NOG mice.

OTME-18. Targeted CRISPR/Cas9 gene-editing regulates the brain tumor environment

Glioblastoma multiform (GBM) is the most common malignant brain tumor. Recent immunotherapy has demonstrated potential to treat GBM. However, the immune suppressive tumor environment in the brain represents a significant barrier for the treatment of GBM. Overexpression of programmed death ligand-1 (PD-L1) in GBM tumor cells and macrophages plays a key role in GBM vitality, proliferation, and migration, while also suppressing the immune system. We developed a CRISPR/Cas9 gene-editing system to delete whole cell PD-L1. Human PD-L1 targeted sgRNA were cloned into CRISPR/Cas9 plasmids with or without an HDR templet. CRISPR/Cas9 were treated to human GBM U87 cells for 15, 30, 60, 120 and 240 minutes. The intracellular concentration of CRISPR/Cas9 exhibited a time-dependent increases. A GFP tagged CRISPR/Cas9 plasmid was developed to test the transfection efficacy. Higher levels of GFP+ U87 cells were observed at day 3. CRISPR/Cas9 showed a greater PD-L1 knockout at day 3. The PD-L1 reduction limited the proliferation of U87 cells. A scratch assay showed that PD-L1 deletion inhibited the migration of U87 cells. An in vitro GBM model was developed by co-cultivation of U87 cells and macrophages. CRISPR/Cas9 treated co-cultures changed the ratios of U87 cells and macrophages and polarized tumor associated macrophages (TAM) from M2 toward M1. CRISPR/Cas9 gene-editing effectively deleted PD-L1 in U87 cells. Successful deletion of PD-L1 prevented U87 cells growth and migration, and altered the TAMs plasticity and the tumor environment.

Screening and characterization of aptamers for recombinant human programmed death-1 and recombinant extracellular domain of human programmed death ligand-1.

Programmed death ligand-1 (PD-L1) is expressed on tumor cells and macrophages. The detection of PD-L1 expression in cancer and the treatment by targeting the PD-L1/programmed death-1 (PD-1) are of great clinical significance. This work aims to screen the aptamers with high affinity and specificity for recombinant human PD-1 (rhPD-1)/recombinant human PD-L1 extracellular domain (rhPD-L1). In this study, we have expressed, purified, prepared, and identified rhPD-1 and rhPD-L1. The rhPD-L1/rhPD-1 aptamers with high affinity and specificity were obtained by systematic evolution of ligands by exponential enrichment technique. Ten aptamers sequences to rhPD-L1 and 10 aptamers sequences to rhPD-1 were obtained by cloning and sequencing. The affinity and specificity of candidate aptamers were analyzed by gold nanoparticles-based colorimetric assay, dot blot assay, and electrophoretic mobility shift assay. The aptamers named A6 were picked out as the optimal aptamers that recognize PD-1, specifically with the Kd value of 47.84 ± 24.78 nM. The aptamers named B10 were picked out as the optimal aptamers that recognize PD-L1, specifically with the Kd value of 59.72 ± 15.87 nM. The study lays a foundation for the development of detection methods and therapeutic drugs targeting PD-L1/PD-1.

A Small Molecule Antagonist of PD-1/PD-L1 Interactions Acts as an Immune Checkpoint Inhibitor for NSCLC and Melanoma Immunotherapy

Immune checkpoint inhibitors, such as monoclonal antibodies targeting programmed death 1 (PD-1) and programmed death ligand-1 (PD-L1), have achieved enormous success in the treatment of several cancers. However, monoclonal antibodies are expensive to produce, have poor tumor penetration, and may induce autoimmune side effects, all of which limit their application. Here, we demonstrate that PDI-1 (also name PD1/PD-L1 inhibitor 1), a small molecule antagonist of PD-1/PD-L1 interactions, shows potent anti-tumor activity in vitro and in vivo and acts by relieving PD-1/PD-L1-induced T cell exhaustion. We show that PDI-1 binds with high affinity to purified human and mouse PD-1 and PD-L1 proteins and is a competitive inhibitor of human PD-1/PD-L1 binding in vitro. Incubation of ex vivo activated human T cells with PDI-1 enhanced their cytotoxicity towards human lung cancer and melanoma cells, and concomitantly increased the production of granzyme B, perforin, and inflammatory cytokines. Luciferase reporter assays showed that PDI-1 directly increases TCR-mediated activation of NFAT in a PD-1/PD-L1-dependent manner. In two syngeneic mouse tumor models, the intraperitoneal administration of PDI-1 reduced the growth of tumors derived from human PD-L1-transfected mouse lung cancer and melanoma cells; increased and decreased the abundance of tumor-infiltrating CD8+ and FoxP3+ CD4+ T cells, respectively; decreased the abundance of PD-L1-expressing tumor cells, and increased the production of inflammatory cytokines. The anti-tumor effect of PDI-1 in vivo was comparable to that of the anti-PD-L1 antibody atezolizumab. These results suggest that the small molecule inhibitors of PD-1/PD-L1 may be effective as an alternative or complementary immune checkpoint inhibitor to monoclonal antibodies.