Combined SEP and anti-PD-L1 antibody produces a synergistic antitumor effect in B16-F10 melanoma-bearing mice

Attenuated Salmonella-delivered PD-1 siRNA enhances the antitumor effects of EZH2 inhibitors in colorectal cancer

Immunotherapy has made significant progress in the treatment of malignant tumors. However, strategies to combine immunotherapy with anticancer drugs have attracted great attention due to the low response rate and unique toxicity profile of immunotherapies and the subsequent development of acquired resistance in some initial responders. EZH2, a histone methyl transferase subunit of a Polycomb repressor complex,is highly expressed in a variety of tumors, and targeting EZH2 has become a new strategy for tumor therapy and drug combination. Here，we studied the effect of EZH2 inhibitors on colorectal cancer cells and their combination with immunotherapy. Our results demonstrated that EZH2 inhibitors can not only significantly inhibit the survival of colorectal cancer (CRC) cells and induce apoptosis, effectively inhibit cell invasion and migration, but also cause an increase in the expression of PD-L1 receptors on the cell surface. To determine the effect of EZH2 in combination with immunotherapy, we combine EZH2 inhibitors with PD-1 siRNA delivered by attenuated Salmonella. The vivo experiments have shown that the combination of EZH2 inhibitors and Salmonella-delivered PD-1 siRNA can further inhibit the development of CRC, trigger effective anti-tumor immunity, and improve therapeutic efficacy. Its underlying mechanisms mainly involve synergistic immunomodulation and apoptosis. This study suggests an emerging strategy based on a combination of EZH2 inhibitor and immunotherapy based on PD-1 inhibition.

Mathematical modeling identifies LAG3 and HAVCR2 as biomarkers of T cell exhaustion in melanoma

Cytotoxic T lymphocytes (CTLs) control tumors via lysis of antigen-presenting targets or through secretion of cytokines such as interferon-γ (IFNG), which inhibit tumor cell proliferation. Improved understanding of CTL interactions within solid tumors will aid the development of immunotherapeutic strategies against cancer. In this study, we take a systems biology approach to compare the importance of cytolytic versus IFNG-mediated cytostatic effects in a murine melanoma model (B16F10) and to dissect the contribution of immune checkpoints HAVCR2, LAG3, and PDCD1/CD274 to CTL exhaustion. We integrated multimodal data to inform an ordinary differential equation (ODE) model of CTL activities inside the tumor. Our model predicted that CTL cytotoxicity played only a minor role in tumor control relative to the cytostatic effects of IFNG. Furthermore, our analysis revealed that within B16F10 melanomas HAVCR2 and LAG3 better characterize the development of a dysfunctional CTL phenotype than does the PDCD1/CD274 axis.

Repurposing Ponatinib as a PD-L1 Inhibitor Revealed by Drug Repurposing Screening and Validation by In Vitro and In Vivo Experiments

Cancer treatment by inhibiting the PD-1/PD-L1 pathway using monoclonal antibodies has made great advances as it showed long-lasting antitumor responses in a wide range of cancers. However, antibodies exhibit several disadvantages, which include low permeability, immune-related adverse effects, complex synthetic procedures, and high treatment costs. Hence, small-molecule inhibitors can be used as alternatives; however, no small molecule with in vivo activity has been reported. In addition, there are many challenges in developing a new drug, including the timeline and escalating cost. Therefore, repurposing an approved drug offers advantages over the development of an entirely new drug. Herein, we identify an FDA-approved small-molecule drug, Ponatinib, as a PD-L1 inhibitor via virtual drug screening of the ZINC database. Ponatinib showed stable binding with PD-L1, with the highest binding energy among all of the screened FDA-approved drugs. The binding of Ponatinib with PD-L1 was supported by a fluorescence quenching assay and immunofluorescence study. Further, we compared the in vivo antitumor efficacy of Ponatinib with a commercially available anti-PD-L1 antibody in the murine melanoma model. Ponatinib was found to be more efficient in delaying tumor growth than the anti-PD-L1 antibody. Furthermore, Ponatinib also reduced the expression of PD-L1 in tumors and increased the T-cell population. Interestingly, splenocytes isolated from Ponatinib-treated mice showed enhanced cytotoxic T-cell (CTL) activity against B16-F10 cells. However, Ponatinib itself did not have any direct toxic effect on cancer cells in vitro. These findings suggest that Ponatinib can be used as a potent small-molecule inhibitor of PD-L1 to overcome the disadvantages associated with antibodies.

Demonstration of the Antitumor Activity of the iNKT Agonist ABX196, a Novel Enhancer of Cancer Immunotherapy, in Melanoma and Hepatocarcinoma Mouse Models

Immune checkpoint blockers (ICB) provide a promising approach to antitumor immunotherapy through blockade of immunosuppressive pathways. The synthetic glycolipid, ABX196, is a potent stimulator of invariant natural killer T cells (iNKT), a small subset of regulatory lymphocytes, which are powerful enhancers of immunity when activated. ABX196 was investigated alone and in combination with chemotherapy and ICBs in a melanoma B16F10 tumor cell-bearing and an orthotopic Hepa 1-6 hepatocarcinoma (HCC) cell-bearing C57BL/6 mice model. In the melanoma model, immune response evaluation included immunofluorescence staining and detection by flow cytometry to identify anti-CD45, anti-CD8, anti-CD4, anti-CD3, anti-CD19, anti-FoxP3, CD1d tetramer, and anti-programmed cell death protein 1 (PD-1) markers. Analysis by MRI, liver weight, and IHC staining to detect CD4, CD8, F4/80, PD-1, programmed death-ligand 1, Ki67, and FoxP3 markers were used to measure antitumor response in the HCC model. Combination treatment with ABX196 and anti-PD-1 resulted in significant synergistic antitumor effects, reflected by the increase of CD8+ cells in the tumor and an increased ratio of CD8+ effector cells to FoxP3+ regulatory T cells (Treg) in mice with melanomas. ABX196 monotherapy and combination therapy resulted in antitumor effects in the HCC model. No significant differences in survival were demonstrated between monotherapy and combination therapy due to high response levels with either treatment. A synergistic combination effect was apparent when IFNγ was measured in peripheral blood, indicating sustained activation of iNKT cells. In both models, the antitumor effects were associated with a generation of a more advantageous T-effector to Treg cell ratio within the tumor, which could lead to in the proliferation and accumulation of cells that would otherwise be anergized.

SYNOPSIS

Using melanoma and HCC tumor models in mice, this study demonstrates the potential of ABX196, alone and in combination with anti-PD-1 antibody, as a novel strategy to overcome the immunosuppressive microenvironment and to produce antitumor activity.

siRNA targeting PD-L1 delivered with attenuated Salmonella enhanced the anti-tumor effect of lenvatinib on mice bearing Hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a primary liver cancer representing serious harm to human health. The effective treatment of HCC is challenging. Lenvatinib is an inhibitor of polytyrosine kinase that exerts an effect against HCC by blocking the VEGF signaling pathway. However, its efficacy in most patients remains unsatisfactory. The factors influencing tumorigenesis are diverse; thus, combined treatment is an important strategy against tumors. Programmed death ligand-1 (PD-L1), which binds to programmed death-1 (PD-1), significantly compromises the anti-tumor effect of T cells. Therefore, we designed a siRNA-PD-L1 and delivered it using attenuated Salmonella, and its synergistic effects with Lenvatinib against HCC were evaluated. The results showed that the combination of Lenvatinib and siRNA-PD-L1 inhibited tumor growth in H22 tumor-bearing mice, arrested cell proliferation, and increased cell apoptosis in the tumor. The combination treatment synergistically inhibited the expression of VEGF and PD-L1 and contributed to the increase in T-cell infiltration in the tumor tissues and the ratio of T cells in the spleen. Furthermore, the combination treatment increased the number of granzyme B⁺ T cells, indicating a significantly improved anti-tumor immunity in mice. Therefore, this combination might be a potential novel strategy for HCC treatment.

Strongylocentrotus nudus Eggs Polysaccharide Enhances Macrophage Phagocytosis Against E.coli Infection by TLR4/STAT3 Axis

Antibiotics resistance is one of the most significant public health threats globally. Strategies that strengthen host defenses to control pathogen infection has become a hot research field. Macrophages are part of early host defense mechanisms, and are activated via host pattern recognition receptors (PRRs), such as Toll-like receptor 4 (TLR4), which then facilitates phagocytosis and elimination of invading pathogens. However, few activators of PRRs have been approved for clinical use because of their toxic effects. This study aimed to investigate whether Strongylocentrotus nudus eggs polysaccharide (SEP), a non-toxic extract from seafood, contributes to host defense against bacterial infection. Results showed that SEP promoted bacterial clearance by enhancing phagocytosis by macrophages during E. coli infection in vitro, but was inhibited by TLR4 specific inhibitor TAK-242, STAT3 inhibitor Stattic or blockade of CD64. In addition, SEP protected mice from E. coli induced mortality, reduced pulmonary inflammation and inhibited dissemination of bacteria to organs, while TAK-242 retarded the protection of SEP. Overall, SEP strengthened innate host defense and improved the outcome in bacterial infection, suggesting that SEP could be used as a potential immunomodulator in host-directed therapies.

Biomaterials and Bioactive Natural Products from Marine Invertebrates: From Basic Research to Innovative Applications

Aquatic invertebrates are a major source of biomaterials and bioactive natural products that can find applications as pharmaceutics, nutraceutics, cosmetics, antibiotics, antifouling products and biomaterials. Symbiotic microorganisms are often the real producers of many secondary metabolites initially isolated from marine invertebrates; however, a certain number of them are actually synthesized by the macro-organisms. In this review, we analysed the literature of the years 2010–2019 on natural products (bioactive molecules and biomaterials) from the main phyla of marine invertebrates explored so far, including sponges, cnidarians, molluscs, echinoderms and ascidians, and present relevant examples of natural products of interest to public and private stakeholders. We also describe omics tools that have been more relevant in identifying and understanding mechanisms and processes underlying the biosynthesis of secondary metabolites in marine invertebrates. Since there is increasing attention on finding new solutions for a sustainable large-scale supply of bioactive compounds, we propose that a possible improvement in the biodiscovery pipeline might also come from the study and utilization of aquatic invertebrate stem cells.

Hypoxia-Mediated ROS Amplification Triggers Mitochondria-Mediated Apoptotic Cell Death via PD-L1/ROS-Responsive, Dual-Targeted, Drug-Laden Thioketal Nanoparticles

Amalgamation of the reactive oxygen species (ROS)-responsive stimulus with nanoparticles has gained considerable interest owing to their high tumor specificity. Hypoxia plays a pivotal role in the acceleration of intracellular ROS production. Herein, we report the construction of a cancer cell (PD-L1)- and ROS-responsive, dual-targeted, temozolomide (TMZ)-laden nanosystem which offers a better anticancer effect in a hypoxic tumor microenvironment. A dual-targeted system boosted permeation in the cancer cells. Hypoxic conditions elevating the high ROS level accelerated the in situ release of TMZ from anti-PD-L1-TKNPs. Hyperaccumulated ROS engendered from TMZ caused oxidative damage leading to mitochondria-mediated apoptosis. TMZ fabricated in the multifunctional nanosystem (anti-PD-L1-TMZ-TKNPs) provided excellent tumor accumulation and retarded tumor growth under in vivo conditions. The elevated apoptosis effect with the activation of an apoptotic marker, DNA double-strand breakage marker, and downregulation of the angiogenesis marker in the tumor tissue following treatment with anti-PD-L1-TMZ-TKNPs exerts robust anticancer effect. Collectively, the nanoconstruct offers deep tumor permeation and high drug release and broadens the application of the ROS-responsive nanosystem for a successful anticancer effect.

Association between PD-L1 Expression and the Prognosis and Clinicopathologic Features of Renal Cell Carcinoma: A Systematic Review and Meta-Analysis

The expression of programmed cell death-ligand 1 (PD-L1) and its correlation with the prognosis and clinicopathologic features of renal cell carcinoma (RCC) remain controversial to date. Concerning this issue, we had conducted a meta-analysis of relevant studies searched in the Web of Science, PubMed, EMBASE, and Cochrane Library databases. The Newcastle-Ottawa quality assessment scale was applied to assess the quality of the included studies. The hazard ratio (HR) and its corresponding 95% confidence intervals (CIs) were collected by Stata 12.0 and used for the results of overall survival (OS) and disease-free survival (DFS). A total of 1,644 patients in 8 studies were included in this meta-analysis. Results showed that PD-L1 expression significantly correlated with OS (HR = 1.98, 95% CI: 1.22-3.22, Z = 2.77, p = 0.006) and DFS (HR = 3.70, 95% CI: 2.07-6.62, Z = 4.40, p = 0.0001) in ccRCC. Subgroup analysis indicated that PD-L1 expression significantly correlated with the lymph-gland transfer ratio (HR = 2.45, 95% CI: 1.02-5.92, Z = 1.99, p = 0.05) and tumor necrosis (HR = 6.05, 95% CI: 3.78-9.67, Z = 7.51, p < 0.00001). This meta-analysis suggests that PD-L1 expression is a valuable prognostic tool for patients with ccRCC. Subgroup analyses demonstrated that it was helpful for screening patients with RCC who need anti-PD-1/PD-L1 treatment and support them to benefit from such immune-targeted therapy.

PCC0208025 (BMS202), a small molecule inhibitor of PD-L1, produces an antitumor effect in B16-F10 melanoma-bearing mice

The increased PD-L1 expression induces poorer prognosis in melanoma. The small molecule inhibitors of PD-1/PD-L1 pathways have been an encouraging drug development strategy because of good affinity and oral bioavailability without immunogenicity and immunotoxicities of PD-1/PD-L1 antibodies. In this study, we studied the effects of PCC0208025 (BMS202), a small molecule inhibitor of PD-L1, on PD-1/PD-L1 binding and the cytokines secretion in human CD3⁺ cells in vitro. We also investigated the antitumor and immunomodulatory activity of PCC0208025 and the pharmacokinetics properties in B16-F10 melanoma-bearing mice. The results showed that PCC0208025 inhibited the PD-1/PD-L1 proteins binding, and rescued PD-L1-mediated inhibition of IFN-γ production in human CD3⁺ T cells in vitro. Furthermore, in B16-F10 melanoma-bearing mice, PCC0208025 presented the antitumor effects, enhanced IFN-γ levels in plasma, increased the frequency of CD3⁺CD8⁺ T and CD8⁺IFN-γ⁺ T and the ratios of CD8⁺/Treg, and deceased the CD4⁺CD25⁺CD127^low/− (Treg) number in tumor. Pharmacokinetics study found that PCC0208025 was absorbed and distributed into the tumors with much higher concentrations than those of the blockade against PD-1/PD-L1 binding. Our work suggests that PCC0208025 exhibited anti-tumor effects through inhibiting Treg expansion and increasing cytotoxic activity of tumor-infiltrating CD8⁺ T cells by the blockade of PD-1/PD-L1 binding, which may provide the pharmacological basis to develop small molecule inhibitors of PD-1/PD-L1 binding for PCC0208025 as a lead compound.

An engineered oncolytic virus expressing PD-L1 inhibitors activates tumor neoantigen-specific T cell responses

Oncolytic viruses offer an in situ vaccination approach to activate tumor-specific T cell responses. However, the upregulation of PD-L1 expression on tumor cells and immune cells leads to tumor resistance to oncolytic immunotherapy. In this study, we generate an engineered oncolytic virus that coexpresses a PD-L1 inhibitor and GM-CSF. We find that the oncolytic virus is able to secrete the PD-L1 inhibitor that systemically binds and inhibits PD-L1 on tumor cells and immune cells. Importantly, the intratumoral injection with the oncolytic virus overcomes PD-L1-mediated immunosuppression during both the priming and effector phases, provokes systemic T cell responses against dominant and subdominant neoantigen epitopes derived from mutations, and leads to an effective rejection of both virus-injected and distant tumors. In summary, this engineered oncolytic virus is able to activate tumor neoantigen-specific T cell responses, providing a potent, individual tumor-specific oncolytic immunotherapy for cancer patients, especially those resistant to PD-1/PD-L1 blockade therapy.

Oncolytic viruses can activate tumor neoantigen-specific T cell responses. However, PD-L1 upregulation on tumor cells and immune cells leads to tumor resistance to this immunotherapy approach. Here, the authors develop an oncolytic virus which expresses both a PD-L1 inhibitor and GM-CSF which allows an improved tumor neoantigen-specific T cell response in preclinical models.

Oncolytic poxvirus CF33-hNIS-ΔF14.5 favorably modulates tumor immune microenvironment and works synergistically with anti-PD-L1 antibody in a triple-negative breast cancer model

Triple-negative breast cancer is the most aggressive subtype of breast cancer and is difficult to treat. Breast cancer is considered to be poorly immunogenic and hence is less responsive to immunotherapies. We tested whether the oncolytic poxvirus CF33-hNIS-ΔF14.5 could modulate tumor immune microenvironment and make the tumors responsive to the immune checkpoint inhibitor anti-PD-L1. We found that virus infection causes the upregulation of PD-L1 levels on triple-negative breast cancer cells in vitro as well as in vivo in mice. In a mouse model of orthotopic triple-negative breast cancer, the virus was found to increase tumor infiltration by CD8+ T cells. Likewise, in mice treated with CF33-hNIS-ΔF14.5 high levels of proinflammatory cytokines IFNγ and IL-6 were found in the tumors but not in the serum. The levels of immune modulation were even higher in mice that were treated with a combination of the virus and anti-PD-L1 antibody. While CF33-hNIS-ΔF14.5 and anti-PD-L1 antibody failed to exert significant anti-tumor effect as a single agent, a combination of the two agents resulted in significant anti-tumor effect with 50% mice experiencing complete tumor regression when both agents were injected intra-tumorally. Furthermore, the ‘cured’ mice did not develop tumor after re-challenge with the same cancer cells suggesting that they developed immunity against those cancer cells. Taken together, our study shows that CF33-hNIS-ΔF14.5 favorably modulates tumor immune microenvironment in triple-negative breast cancer model making them responsive to the immune checkpoint inhibitor anti-PD-L1, and hence warrants further studies to determine the clinical applicability of this combination therapy.