L-5-hydroxytryptophan promotes antitumor immunity by inhibiting PD-L1 inducible expression.

BACKGROUND: The repression or downregulation of programmed death-ligand 1 (PD-L1) can release its inhibition of T cells and activate antitumor immune responses. Although PD-1 and PD-L1 antibodies are promising treatments for diverse tumor types, their inherent disadvantages and immune-related adverse events remain significant issues. The development of small molecule inhibitors targeting the interaction surface of PD-1 and PD-L1 has been reviving, yet many challenges remain. To address these issues, we aimed to find small molecules with durable efficacy and favorable biosafety that alter PD-L1 surface expression and can be developed into a promising alternative and complementary therapy for existing anti-PD-1/PD-L1 therapies. METHODS: Cell-based screen of 200 metabolic molecules using a high-throughput flow cytometry assay of PD-L1 surface expression was conducted, and L-5-hydroxytryptophan (L-5-HTP) was found to suppress PD-L1 expression induced by interferon gamma (IFN-γ). Inhibition of PD-L1 induction and antitumor effect of L-5-HTP were evaluated in two syngeneic mouse tumor models. Flow cytometry was performed to investigate the change in the tumor microenvironment caused by L-5-HTP treatment. RESULTS: We discovered that L-5-HTP suppressed IFN-γ-induced PD-L1 expression in tumor cells transcriptionally, and this effect was directly due to itself. Mechanistically, L-5-HTP inhibited IFN-γ-induced expression of RTK ligands and thus suppressed phosphorylation-mediated activation of RTK receptors and the downstream MEK/ERK/c-JUN signaling cascade, leading to decreased PD-L1 induction. In syngeneic mouse tumor models, treatment with 100 mg/kg L-5-HTP (intraperitoneal) inhibited PD-L1 expression and exhibited antitumor effect. L-5-HTP upregulated the ratio of granzyme B+ CD8+ activated cytotoxic T cells. An intact immune system and PD-L1 expression was critical for L-5-HTP to exert its antitumor effects. Furthermore, L-5-HTP acted synergistically with PD-1 antibody to improve anticancer effect. CONCLUSION: Our study illustrated L-5-HTP's inhibitory effect on PD-L1 induction stimulated by IFN-γ in tumor cells and also provided insight into repurposing L-5-HTP for use in tumor immunotherapy.

Maximizing cancer therapy via complementary mechanisms of immune activation: PD-1 blockade, neoantigen vaccination, and Tregs depletion.

BACKGROUND: A number of different immune pathways are involved in the effective killing of cancer cells, collectively named as the 'Cancer Immunity Cycle'. Anti-PD-1 checkpoint blockade (CPB) therapy is active on one of these pathways and reinvigorates anticancer T cell immunity, leading to long-term responses in a limited fraction of patients with cancer. We have previously shown that neoantigens-based adenovirus vectored vaccine in combination with anti-PD-1 further expands pre-existing anticancer immunity and elicits novel neoantigen-specific T cells thereby increasing efficacy to 50% of tumor clearance in mice. Here we added a third component to the CPB plus vaccine combination, which is able to modify the suppressive tumor microenvironment by reducing the number of tumor-infiltrating regulatory T cells (Tregs), as strategy for improving the therapeutic efficacy and overcoming resistance. METHODS: The antitumor efficacy of anti-PD-1, neoantigen vaccine and Treg modulating agents, either Bempegaldesleukin (BEMPEG: NKTR-214) or an anti-CTLA-4 mAb with Treg-depleting activity, was investigated in murine tumor models. We evaluated tumor growth in treated animals, neoantigen-specific T cells in tumors, tumor-infiltrating lymphocytes (TILs) and intratumoral Tregs. RESULTS: The addition of BEMPEG or anti-CTLA-4 to the combination of vaccine and anti-PD-1 led to complete eradication of large tumors in nearby 100% of treated animals, in association with expansion and activation of cancer neoantigen-specific T cells and reduction of tumor-infiltrating Tregs. CONCLUSION: These data support the notion that the integrated regulation of three steps of the cancer immunity cycle, including expansion of neoantigen-specific T cells, reversal of the exhausted T cell phenotype together with the reduction of intratumoral Tregs may represent a novel rationally designed drug combination approach to achieve higher cure rates.

Thermal-sensitive lipid nanoparticles potentiate anti-PD therapy through enhancing drug penetration and T lymphocytes infiltration in metastatic tumor.

The response rate of anti-PD therapy in most cancer patients remains low. Therapeutic drug and tumor-infiltrating lymphocytes (TILs) are usually obstructed by the stromal region within tumor microenvironment (TME) rather than distributed around tumor cells, thus unable to induce the immune response of cytotoxic T cells. Here, we constructed the cationic thermosensitive lipid nanoparticles IR780/DPPC/BMS by introducing cationic NIR photosensitizer IR-780 iodide (IR780) modified lipid components, thermosensitive lipid DPPC and PD-1/PD-L1 inhibitor BMS202 (BMS). Upon laser irradiation, IR780/DPPC/BMS penetrated into deep tumor, and reduced cancer-associated fibroblasts (CAFs) around tumor cells to remodel the spatial distribution of TILs in TME. Interestingly, the cationic IR780/DPPC/BMS could capture released tumor-associated antigens (TAAs), thereby enhancing the antigen-presenting ability of DCs to activate cytotoxic T lymphocytes. Moreover, IR780/DPPC/BMS initiated gel-liquid crystal phase transition under laser irradiation, accelerating the disintegration of lipid bilayer structure and leading to the responsive release of BMS, which would reverse the tumor immunosuppression state by blocking PD-1/PD-L1 pathway for a long term. This combination treatment can synergistically exert the antitumor immune response and inhibit the tumor growth and metastasis.

Development of natural products for anti-PD-1/PD-L1 immunotherapy against cancer.

ETHNOPHARMACOLOGICAL RELEVANCE: The programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) immune checkpoint is one of the most promising therapeutic targets for cancer immunotherapy, but several challenges remain in current anti-PD-1/PD-L1 therapy. Natural products, mainly derived from traditional medicine, could improve and expand anti-PD-1/PD-L1 therapy because of their advantages such as large diversity and multi-target effects. AIM OF THE STUDY: This review summarize natural products, raw extracts, and traditional medicines with pharmacological effects associated with the PD-1/PD-L1 axis, particularly PD-L1. MATERIALS AND METHODS: Electronic literature databases, including Web of Science, PubMed, and ScienceDirect, and online drugs and chemicals databases, including DrugBank, ZINC, PubChem, STITCH, and CTD, were searched without date limitation by February 2021. 'Natural product or herb or herbal plant or traditional medicine' and 'PD-L1' and 'Cancer immunotherapy' were used as the search keywords. Among 112 articles identified in database searching, 54 articles are full text articles, reporting in silico, in vitro, in vivo and clinical trials. 68 articles included are review articles and grey literature such as thesis and congress abstracts. RESULTS: Several natural products and traditional medicines have exhibited diverse and multi-functional effects including direct blockade of PD-1/PD-L1 interactions, modulation of PD-L1 expression, and cooperation with PD-1/PD-L1 inhibitors. CONCLUSION: Natural products and traditional medicines can facilitate the development of more effective and acceptable diverse strategies for anti-PD-1/PD-L1 therapy, but further exploration of natural products and pharmaceutical techniques is required.

YIV-906 potentiated anti-PD1 action against hepatocellular carcinoma by enhancing adaptive and innate immunity in the tumor microenvironment.

YIV-906 (PHY906) is a standardized botanical cancer drug candidate developed with a systems biology approach-inspired by a traditional Chinese herbal formulation, historically used to treat gastrointestinal symptoms including diarrhea, nausea and vomiting. In combination with chemotherapy and/or radiation therapy, preclinical and clinical results suggest that YIV-906 has the potential to prolong survival and improve quality of life for cancer patients. Here, we demonstrated that YIV-906 plus anti-PD1 could eradicate all Hepa 1-6 tumors in all tumor bearing mice. YIV-906 was found to have multiple mechanisms of action to enhance adaptive and innate immunity. In combination, YIV-906 reduced PD1 or counteracted PD-L1 induction caused by anti-PD1 which led to higher T-cell activation gene expression of the tumor. In addition, YIV-906 could reduce immune tolerance by modulating IDO activity and reducing monocytic MDSC of the tumor. The combination of anti-PD1 and YIV-906 generated acute inflammation in the tumor microenvironment with more M1-like macrophages. YIV-906 could potentiate the action of interferon gamma (IFNg) to increase M1-like macrophage polarization while inhibiting IL4 action to decrease M2 macrophage polarization. Flavonoids from YIV-906 were responsible for modulating IDO activity and potentiating IFNg action in M1-like macrophage polarization. In conclusion, YIV-906 could act as an immunomodulator and enhance the innate and adaptive immune response and potentiate anti-tumor activity for immunotherapies to treat cancer.

Hyperbaric Oxygen Boosts PD-1 Antibody Delivery and T Cell Infiltration for Augmented Immune Responses Against Solid Tumors.

Aberrant mechanical properties and immunosuppression are the two key factors that limit the antitumor efficacy of T cell immune checkpoint blockade inhibitors, e.g., programmed cell death-1 antibody (PD-1 Ab), against solid tumors in the clinic. This study leverages hyperbaric oxygen (HBO) for the first time to address these two issues and reports the PD-1-Ab-mediated immune responses against various stroma-rich solid malignancies. The results demonstrate that HBO promoted PD-1 Ab delivery and T cells infiltration into tumor parenchyma by depleting the extracellular matrix's main components, such as collagen and fibronectin. Furthermore, HBO disrupts hypoxia-mediated immunosuppression and helps PD-1 Ab trigger robust cytotoxic T lymphocytes and long-lasting immunological memory to inhibit tumor relapses. Such enhanced immune responses are effective in solid tumors from rodents and the cancer cells from hepatocellular carcinoma patients. The results illustrate that HBO bolsters antitumor efficacy of PD-1 Ab, and the HBO-PD-1 Ab combination is a promising stroma-rich solid tumors' treatment in the clinic.

Enhancing clinical and immunological effects of anti-PD-1 with belapectin, a galectin-3 inhibitor.

BACKGROUND: PD-1/PD-L1 engagement and overexpression of galectin-3 (Gal-3) are critical mechanisms of tumor-induced immune suppression that contribute to immunotherapy resistance. We hypothesized that Gal-3 blockade with belapectin (GR-MD-02) plus anti-PD-1 (pembrolizumab) would enhance tumor response in patients with metastatic melanoma (MM) and head and neck squamous cell carcinoma (HNSCC). METHODS: We performed a phase I dose escalation study of belapectin+pembrolizumab in patients with advanced MM or HNSCC (NCT02575404). Belapectin was administered at 2, 4, or 8 mg/kg IV 60 min before pembrolizumab (200 mg IV every 3 weeks for five cycles). Responding patients continued pembrolizumab monotherapy for up to 17 cycles. Main eligibility requirements were a functional Eastern Cooperative Oncology Group status of 0-2, measurable or assessable disease, and no active autoimmune disease. Prior T-cell checkpoint antibody therapy was permitted. RESULTS: Objective response was observed in 50% of MM (7/14) and and 33% of HNSCC (2/6) patients. Belapectin+pembrolizumab was associated with fewer immune-mediated adverse events than anticipated with pembrolizumab monotherapy. There were no dose-limiting toxicities for belapectin within the dose range investigated. Significantly increased effector memory T-cell activation and reduced monocytic myeloid-derived suppressor cells (M-MDSCs) were observed in responders compared with non-responders. Increased baseline expression of Gal-3+ tumor cells and PD-1+CD8+ T cells in the periphery correlated with response as did higher serum trough levels of pembrolizumab. CONCLUSIONS: Belapectin+pembrolizumab therapy has activity in MM and HNSCC. Increased Gal-3 expression, expansion of effector memory T cells, and decreased M-MDSCs correlated with clinical response. Further investigation is planned.

Narrowband ultraviolet B therapy for refractory immune-related lichenoid dermatitis on PD-1 therapy: a case report.

Treatment with programmed cell death 1 inhibitors is associated with a wide range of cutaneous immune-related adverse events, with lichenoid eruptions representing one of the major cutaneous toxicities. We describe the case of an 81-year-old man with metastatic melanoma treated with pembrolizumab who subsequently developed a delayed-onset generalized lichenoid dermatitis. After failing multiple lines of systemic immunosuppression, narrowband ultraviolet B (NBUVB) phototherapy three times per week for 17 sessions resulted in a significant clinical response in his cutaneous eruption and was well tolerated. NBUVB is a safe, lower-cost modality that induces local, skin-specific immunosuppression without the toxicities of traditional systemic immunosuppressive agents. To date, this is the first report of use of NBUVB in immune-related lichenoid dermatitis resistant to multiple standard therapies.

A combination of PD­1/PD­L1 inhibitors: The prospect of overcoming the weakness of tumor immunotherapy (Review).

Programmed cell death protein­1 (PD­1)/programmed death protein ligand­1 (PD­L1) inhibitors for treatment of a various types of cancers have revolutionized cancer immunotherapy. However, PD­1/PD­L1 inhibitors are associated with a low response rate and are only effective on a small number of patients with cancer. Development of an anti­PD­1/PD­L1 sensitizer for improving response rate and effectiveness of immunotherapy is a challenge. The present study reviews the synergistic effects of PD­1/PD­L1 inhibitor with oncolytic virus, tumor vaccine, molecular targeted drugs, immunotherapy, chemotherapy, radiotherapy, intestinal flora and traditional Chinese medicine, to provide information for development of effective combination therapies.

Liver Injury Caused by Green Tea Extract in PD-1-/- Mice: An Impaired Immune Tolerance Model for Idiosyncratic Drug-Induced Liver Injury.

Idiosyncratic drug-induced liver injury (IDILI) is an idiosyncratic drug reaction that is specific to an individual and can lead to liver failure and even death. The mechanism of IDILI remains poorly understood, but most IDILI appears to be immune-mediated. We have developed the first validated animal model by using a PD-1-/- mouse model in combination with anti-CTLA-4 to block immune checkpoints and impair immune tolerance. Treatment of these mice with drugs that cause IDILI in humans led to delayed-onset liver injury with characteristics similar to IDILI in humans. The current study investigates the effects of green tea extract, a weight-loss dietary supplement that has been reported to cause IDILI in humans. Green tea extracts contain a highly variable content of catechins including (-)-epigallocatechin gallate, the major catechin in green tea formulations. If the liver injury caused by green tea extract in humans is immune-mediated, it may occur in our impaired immune tolerance model. Female PD-1-/- mice treated with anti-CTLA-4 antibody and green tea extract (500 mg/kg), a dose that is considered a no-observed-adverse-effect level for liver in rodents, produced a delayed onset increase in serum alanine transaminase levels and an increase in hepatic CD8+ T cells. In contrast, the response in male PD-1-/- mice was less pronounced, and there was no evidence of liver injury in wild-type mice. These findings are consistent with the hypothesis that the IDILI caused by green tea extract is immune-mediated and is similar to IDILI caused by medications that are associated with IDILI.