Programmed Cell Death Ligand-1 Axis Research Articles

Engineered nanomedicines block the PD-1/PD-L1 axis for potentiated cancer immunotherapy.

Immunotherapy, in particular immune checkpoint blockade (ICB) therapy targeting the programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) axis, has remarkably revolutionized cancer treatment in the clinic. Anti-PD-1/PD-L1 therapy is designed to restore the antitumor response of cytotoxic T cells (CTLs) by blocking the interaction between PD-L1 on tumour cells and PD-1 on CTLs. Nevertheless, current anti-PD-1/PD-L1 therapy suffers from poor therapeutic outcomes in a large variety of solid tumours due to insufficient tumour specificity, severe cytotoxic effects, and the occurrence of immune resistance. In recent years, nanosized drug delivery systems (NDDSs), endowed with highly efficient tumour targeting and versatility for combination therapy, have paved a new avenue for cancer immunotherapy. In this review article, we summarized the recent advances in NDDSs for anti-PD-1/PD-L1 therapy. We then discussed the challenges and further provided perspectives to promote the clinical application of NDDS-based anti-PD-1/PD-L1 therapy.

Yin Yang 1-stimulated long noncoding RNA bladder cancer-associated transcript 1 upregulation facilitates esophageal carcinoma progression via the microRNA-5590-3p/programmed cell death-ligand 1 pathway

ABSTRACT Esophageal carcinoma (EC) is a common gastrointestinal malignancy that poses a threat to public health worldwide. Long noncoding RNA (lncRNA) bladder cancer-associated transcript 1 (BLACAT1) exerts a tumorigenic role in several malignant tumors; nevertheless, its function in EC remains largely unknown. Besides, programmed cell death-ligand 1 (PD-L1), an oncogene in numerous human cancers, has been identified as a therapeutic target for EC. Therefore, we intended to explore the potential regulatory network involving BLACAT1 and PD-L1 in EC. In this study, we observed increased BLACAT1 and PD-L1 levels in EC tissues and EC cell lines. Moreover, YY1 could activate BLACAT1 transcription in EC cells (TE-1 and EC9706). In addition, in vitro and in vivo experiments demonstrated that BLACAT1 facilitated EC cell proliferation and metastasis and EC tumor growth. Also, the effects of BLACAT1 silencing on EC cell functions were partially reversed by PD-L1 overexpression. Besides, it was identified that BLACAT1 competed with PD-L1 to bind to miR-5590-3p in EC cells. Furthermore, miR-5590-3p suppression could abrogate the functional effects of BLACAT1 knockdown on EC cells; while PD-L1 silencing partly abolished the promoting effects of miR-5590-3p suppression on the biological functions of EC cells. To sum up, YY1-induced BLACAT1 accelerated EC progression via regulating the miR-5590-3p/PD-L1 axis.

CircFOXK2 enhances tumorigenesis and immune evasion in non-small cell lung cancer by miR-485-5p/PD-L1 axis.

Circular RNAs (circRNAs) serve a key role in lots of cancers. The outcomes of upregulated circular RNA forkhead box K2 (circFOXK2) on non-small cell lung cancer (NSCLC) persisted uncertainly. In this study, the role of circFOXK2 in NSCLC was inspected. The abundances of circFOXK2, microRNA-485-5p (miR-485-5p) and programmed cell death ligand-1 (PD-L1) were confirmed by quantitative real-time PCR and western blot. Cell counting kit-8 (CCK-8) assay and clonogenic assay were accomplished to conclude the proliferation of NSCLC cells. Wound healing and transwell assays were implemented to evaluate cell migration and invasion. Lactate dehydrogenase (LDH) cytotoxicity assay was enforced to quantify the cytotoxicity of CD8+ T cells. Flow cytometry assay was employed to detect apoptosis. Besides, the mice experiments were utilized for in vivo tumorigenesis analysis. Dual-luciferase reporter assay was carried out to reveal the associations between miR-485-5p and circFOXK2 or PD-L1. CircFOXK2 and PD-L1 levels were augmented in NSCLC. CircFOXK2 targeted miR-485-5p, which could bind to PD-L1. CircFOXK2 served a key role in NSCLC tumorigenesis and cytotoxicity of CD8+ T cells. MiR-485-5p inhibition or PD-L1 overexpression abolished the inhibitory effects of circFOXK2 lack on NSCLC tumorigenesis and cytotoxicity of CD8+ T cells. CircFOXK2 sponged miR-485-5p to stimulate PD-L1 and expedited NSCLC development.

Discovery of 4-phenylindolines containing a (5-cyanopyridin-3-yl)methoxy moiety as potent inhibitors of the PD-1/PD-L1 interaction

With the great success of anti-programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) monoclonal antibodies in clinical applications, blocking the PD-1/PD-L1 pathway has become the most compelling strategy in the field of tumor immunotherapy. In this study, a novel series of 4-phenylindolines containing a (5-cyanopyridin-3-yl)methoxy moiety were developed, and their structure–activity relationships were preliminarily discussed. Among them, compounds M17 and M23 exhibited the most potent ability to disrupt the PD-1/PD-L1 interaction, demonstrating IC50 values of 60.1 nM and 53.2 nM, respectively. The binding mode of M23 was further explored by molecular docking analysis with dimeric PD-L1. Therefore, M17 and M23 are promising lead compounds for developing potent inhibitors of the PD-1/PD-L1 axis.

Radiation Therapy Promotes Hepatocellular Carcinoma Immune Cloaking via PD-L1 Upregulation Induced by cGAS-STING Activation

Radiation therapy (RT) is one of the main treatments for patients with unresectable hepatocellular carcinoma (HCC). Emerging evidence indicates that the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) stimulator of interferon gene (STING) pathway is crucial in RT-induced antitumor immune responses. Here, we discovered that activation of the cancer cell-intrinsic cGAS-STING pathway mediated immune cloaking after RT-induced DNA damage. Key regulatory proteins in the cGAS-STING signaling pathway in human and murine HCC cell lines were knocked out or down using CRISPR and CRISPR-associated protein 9 or small interfering RNA. The underlying mechanism of immune cloaking and clinical significance of cGAS-STING-induced programmed cell death ligand 1 (PD-L1) expression were studied with both ex vivo analyses and in vitro experiments. RT upregulated PD-L1 in patients with HCC, which correlated with poor survival. RT activated cGAS-STING, increasing immune-checkpoint PD-L1 expression in human and mouse liver cancer cells. Ionizing radiation activated the STING-TANK-binding kinase 1 (TBK1)-interferon regulatory factor 3 (IRF3) innate immune pathway, leading to PD-L1 upregulation in HCC cells and inhibiting cytotoxic T-lymphocyte activity and protecting tumor cells from immune-mediated eradication. Knockdown of cGAS, STING, TBK1, and IRF3 reversed the antitumor effect of cytotoxic T-lymphocyte-mediated cytotoxicity after ionizing radiation in vitro or in vivo. RT potentiated the antitumor effect of programmed cell death protein 1 and PD-L1 axis blockade and augmented cytotoxic T-cell (CTL) infiltration in HCC tumors in immunocompetent mice. CD8 depletion compromised the synergetic antitumor effect of combined RT and anti-PD-L1 blockade, demonstrating that CD8+ CTLs are required for antitumor immunity induced by combination therapy. Our results identified an immune-cloaking mechanism for RT-activated, innate immune cGAS-STING and suggested that RT enhances HCC immunotherapy.

Novel Biphenyl Pyridines as Potent Small-Molecule Inhibitors Targeting the Programmed Cell Death-1/Programmed Cell Death-Ligand 1 Interaction.

With the successful clinical application of anti-programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) monoclonal antibodies (mAb), targeting the PD-1/PD-L1 interaction has become a promising method for the discovery of cancer therapy. Due to the inherent limitations of antibodies, it is necessary to search for small-molecule inhibitors against the PD-1/PD-L1 axis. We report the design, synthesis, and evaluation in vitro and in vivo of a series of novel biphenyl pyridines as the inhibitors of PD-1/PD-L1. 2-(((2-Methoxy-6-(2-methyl-[1,1'-biphenyl]-3-yl)pyridin-3-yl)methyl)amino)ethan-1-ol (24) was found to inhibit the PD-1/PD-L1 interaction with an IC50 value of 3.8 ± 0.3 nM and enhance the killing activity of tumor cells by immune cells. Compound 24 displays great pharmacokinetics (oral bioavailability of 22%) and significant in vivo antitumor activity in a CT26 mouse model. Flow cytometry and immunohistochemistry data indicated that compound 24 activates the immune activity in tumors. These results suggest that compound 24 is a promising small-molecule inhibitor against the PD-1/PD-L1 axis and merits further development.

Bone marrow-derived mesenchymal stem cells inhibit CD8+ T cell immune responses via PD-1/PD-L1 pathway in multiple myeloma.

High expression of the inhibitory receptor programmed cell death ligand 1 (PD-L1) on tumor cells and tumor stromal cells have been found to play a key role in tumor immune evasion in several human malignancies. However, the expression of PD-L1 on bone marrow mesenchymal stem cells (BMSCs) and whether the programmed cell death 1 (PD-1)/PD-L1 signal pathway is involved in the BMSCs versus T cell immune response in multiple myeloma (MM) remains poorly defined. In this study, we explored the expression of PD-L1 on BMSCs from newly diagnosed MM (NDMM) patients and the role of PD-1/PD-L1 pathway in BMSC-mediated regulation of CD8+ T cells. The data showed that the expression of PD-L1 on BMSCs in NDMM patients was significantly increased compared to that in normal controls (NC) (18·81±1·61 versus 2·78±0·70%; P<0·001). Furthermore, the PD-1 expression on CD8+ T cells with NDMM patients was significantly higher than that in normal controls (43·22±2·98 versus 20·71±1·08%; P<0·001). However, there was no significant difference in PD-1 expression of CD4+ T cells and natural killer (NK) cells between the NDMM and NC groups. Additionally, the co-culture assays revealed that BMSCs significantly suppressed CD8+ T cell function. However, the PD-L1 inhibitor effectively reversed BMSC-mediated suppression in CD8+ T cells. We also found that the combination of PD-L1 inhibitor and pomalidomide can further enhance the killing effect of CD8+ T cells on MM cells. In summary, our findings demonstrated that BMSCs in patients with MM may induce apoptosis of CD8+ T cells through the PD-1/PD-L1 axis and inhibit the release of perforin and granzyme B from CD8+ T cells to promote the immune escape of MM.

HIF1A-AS2 Promotes the Proliferation and Metastasis of Gastric Cancer Cells Through miR-429/PD-L1 Axis.

Gastric cancer (GC) is a common leading cause of cancer-related mortality of all malignancies. LncRNA hypoxia-inducible factor-1 alpha antisense RNA-2 (HIF1A-AS2) has been identified to involve in the development of GC. Therefore, we further explored the detailed molecular mechanism of HIF1A-AS2 in GC progression. The expression of HIF1A-AS2, microRNA-429 (miR-429), and programmed cell death ligand 1 (PD-L1) was measured using quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. Cell proliferation, migration, and invasion abilities were detected by Cell Counting Kit-8 (CCK-8) or transwell assay. The interaction between miR-429 and HIF1A-AS2 or PD-L1 was confirmed by luciferase reporter assay. Murine xenograft model was established to investigate the role of HIF1A-AS2 in vivo. HIF1A-AS2 was elevated in GC tissues and cell lines. Functional experiments showed that HIF1A-AS2 knockdown inhibited GC cell proliferation, migration, and invasion in vitro, as well as hindered tumor growth in vivo. Moreover, HIF1A-AS2 directly bound to miR-429 based on bioinformatics prediction and luciferase assay, and inhibition of miR-429 abolished the effects of HIF1A-AS2 knockdown on GC cells. Furthermore, miR-429 directly targeted PD-L1, and overexpression of miR-429 suppressed GC tumorigenesis via PD-L1. Besides that, PD-L1 also performed an oncogenic role in GC cell proliferation and metastasis. Additionally, HIF1A-AS2 could indirectly regulate PD-L1 expression via sponging miR-429. HIF1A-AS2 is a dependable predictor of malignancy and prognosis in GC and functions as an oncogene to promote GC cell proliferation and metastasis by regulating miR-429/PD-L1 axis, indicating a new insight into the search for novel biomarkers and therapeutic strategies.

Immune checkpoint expression on peripheral cytotoxic lymphocytes in cervical cancer patients: moving beyond the PD-1/PD-L1 axis.

Immune checkpoint therapy to reverse natural killer (NK) and T cell exhaustion has emerged as a promising treatment in various cancers. While anti-programmed cell death 1 (PD-1) pembrolizumab has recently gained Food and Drug Administration (FDA) approval for use in recurrent or metastatic cervical cancer, other checkpoint molecules, such as T cell immunoreceptor with immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibition motif (ITIM) domains (TIGIT) and T cell immunoglobulin and mucin-domain containing-3 (Tim-3), have yet to be fully explored in this disease. We report expression of TIGIT, Tim-3 and PD-1 on subsets of peripheral blood NK (CD56dim/neg CD16bright/dim/neg and CD56bright CD16dim/neg ) and T cells. The percentages of these cells were increased in women with cervical cancer and pre-malignant lesions. PD-1+ NK and T cells were likely to co-express TIGIT and/or Tim-3. These cells, with an apparently 'exhausted' phenotype, were augmented in patients. A subset of cells were also natural killer group 2 member D (NKG2D)- and DNAX accessory molecule 1 (DNAM-1)-positive. PD-1int and PD-1high T cells were notably increased in cervical cancer. Soluble programmed cell death ligand 1 (PD-L1) was higher in cancer patient blood versus healthy donors and we observed a positive correlation between sPD-L1 and PD-1+ T cells in women with low-grade lesions. Within the cancer group, there were no significant correlations between sPD-L1 levels and cervical cancer stage. However, when comparing cancer versus healthy donors, we observed an inverse association between sPD-L1 and total T cells and a correlation between sPD-L1 and CD56dim NK cells. Our results may show an overview of the immune response towards pre-cancerous lesions and cervical cancer, perhaps giving an early clue as to whom to administer blocking therapies. The increase of multiple checkpoint markers may aid in identifying patients uniquely responsive to combined antibody therapies.

Programmed Cell Death Protein 1/Programmed Cell Death Ligand-1 Axis activates Intracellular ERK Signaling in Tumor Cells to Mediate Poor Prognosis in T-cell Lymphoma.

Purpose: To investigate the prognostic significance of programmed cell death ligand-1 (PD-L1) and phosphorylated ERK (p-ERK) and their interactions in T-cell lymphoma (TCL).Methods: The mRNA levels of PD-L1 and ERK in TCL samples were analyzed. Formalin-fixed paraffin-embedded tissues from 69 TCL patients were collected to detect the expression of PD-L1 and p-ERK by multiplexed immunofluorescence staining. The total PD-L1 and p-ERK was measured by western blotting, and membrane PD-L1 was determined using flow cytometry.Results: PD-L1 and ERK mRNA levels were significantly upregulated in TCL. The expression rates of PD-L1 and p-ERK were 52.2% and 27.5%, respectively. PD-L1 expression correlated with stage (R=0.304, P=0.011) and IPI score (R=0.313, P=0.009), and p-ERK expression correlated with stage (R=0.330, P=0.006) and IPI score (R=0.376, P=0.002). PD-L1 expression positively correlated with p-ERK expression (R=0.355, P=0.003). Patients with co-expression of PD-L1 and p-ERK had the worst overall survival (P=0.007). In three TCL cell lines with PD-L1 expression, we demonstrated that the expression of p-ERK was upregulated after stimulation with PD-1, suggesting that ERK signaling was activated.Conclusions: The PD-1/PD-L1 axis activates intracellular ERK signaling in tumor cells and that PD-L1, p-ERK or their combination are potential biomarkers for predicting the prognosis in TCL patients.

Study and analysis of antitumor resistance mechanism of PD1/PD-L1 immune checkpoint blocker.

Immunocheckpoint proteins of tumor infiltrating lymphocytes play an important role in tumor prognosis in the course of tumor clinicopathology. PD‐1 (Programmed cell death protein 1) is an important immunosuppressive molecule. By binding to PD‐L1 (programmed cell death‐ligand 1), it blocks TCR and its costimulus signal transduction, inhibits the activation and proliferation of T cells, depletes the function of effector T cells, and enables tumor cells to achieve immune escape. In recent years, immunocheckpoint blocking therapy targeting the PD‐1/PD‐L1 axis has achieved good results in a variety of malignant tumors, pushing tumor immunotherapy to a new milestone, such as anti‐PD‐1 monoclonal antibody Nivolumab, Pembrolizumab, and anti‐PD‐L1 monoclonal antibody Atezolizumab, which are considered as potential antitumor drugs. It was found in clinical use that some patients obtained long‐term efficacy, but most of them developed drug resistance recurrence in the later stage. The high incidence of drug resistance (including primary and acquired drug resistance) still cannot be ignored, which limited its clinical application and became a new problem in this field. Due to tumor heterogeneity, current limited research shows that PD‐1 or PD‐L1 monoclonal antibody drug resistance may be related to the following factors: mutation of tumor antigen and antigen presentation process, multiple immune checkpoint interactions, immune microenvironment changes dynamically, activation of oncogenic pathways, gene mutation and epigenetic changes of key proteins in tumors, tumor competitive metabolism, and accumulation of metabolites, etc, mechanisms of resistance are complex. Therefore, it is the most urgent task to further elucidate the mechanism of immune checkpoint inhibitor resistance, discover multitumor universal biomarkers, and develop new target agents to improve the response rate of immunotherapy in patients. In this study, the mechanism of anti‐PD‐1/PD‐L1 drug resistance in tumors, the potential biomarkers for predicting PD‐1 acquired resistance, and the recent development of combination therapy were reviewed one by one. It is believed that, based on the complex mechanism of drug resistance, it is of no clinical significance to simply search for and regulate drug resistance targets, and it may even produce drug resistance again soon. It is speculated that according to the possible tumor characteristics, three types of treatment methods should be combined to change the tumor microenvironment ecology and eliminate various heterogeneous tumor subsets, so as to reduce tumor drug resistance and improve long‐term clinical efficacy.

Combining poly(ADP-ribose) polymerase inhibitors and immune checkpoint inhibitors in breast cancer: rationale and preliminary clinical results.

Recently, both immune checkpoint inhibitors and poly(ADP-ribose) polymerase inhibitors have demonstrated clinical benefit in some subsets of HER2-negative breast cancer patients. A biological rationale exists supporting a potential synergism between these compounds, which may further increase their antitumor activity in the clinic. PARP inhibitors were shown to activate type I interferon pathway, thus eliciting local and general immune response, while inducing programmed cell death-ligand 1 (PD-L1) up-regulation. In addition, the DNA damages created by PARP inhibition may increase tumor mutational burden and neo-antigens, thereby favoring efficacy of immune checkpoint inhibitors. Accordingly, clinical trials combining PARP inhibitors and agents targeting the PD-1/PD-L1 axis have been initiated in breast cancer in both advanced and early stages, enrolling patients with germline BRCA1/2 mutation, homologous recombination deficiency and/or with triple negative phenotype. Preliminary safety and efficacy results are encouraging, but it is still unclear whether the combination adds benefit compared with each therapeutic administered as single agent. Although a strong rationale exists to support the combination of PARP inhibitors with immune checkpoint inhibitors, future clinical trials will have to demonstrate whether it improves outcome and to identify which patients are the most likely to benefit from.

Berberine diminishes cancer cell PD-L1 expression and facilitates antitumor immunity via inhibiting the deubiquitination activity of CSN5

Programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) blocking therapy has become a major pillar of cancer immunotherapy. Compared with antibodies targeting, small-molecule checkpoint inhibitors which have favorable pharmacokinetics are urgently needed. Here we identified berberine (BBR), a proven anti-inflammation drug, as a negative regulator of PD-L1 from a set of traditional Chinese medicine (TCM) chemical monomers. BBR enhanced the sensitivity of tumour cells to co-cultured T-cells by decreasing the level of PD-L1 in cancer cells. In addition, BBR exerted its antitumor effect in Lewis tumor xenograft mice through enhancing tumor-infiltrating T-cell immunity and attenuating the activation of immunosuppressive myeloid-derived suppressor cells (MDSCs) and regulatory T-cells (Tregs). BBR triggered PD-L1 degradation through ubiquitin (Ub)/proteasome-dependent pathway. Remarkably, BBR selectively bound to the glutamic acid 76 of constitutive photomorphogenic-9 signalosome 5 (CSN5) and inhibited PD-1/PD-L1 axis through its deubiquitination activity, resulting in ubiquitination and degradation of PD-L1. Our data reveals a previously unrecognized antitumor mechanism of BBR, suggesting BBR is small-molecule immune checkpoint inhibitor for cancer treatment.

662 Targeting the α9-nAChR/PD-L1 axis in antiproliferative effects of Allium cepa L. var. proliferum Regel extract on melanoma cells

Programmed cell death ligand-1 (PD-L1) is critical for melanoma development, progression and treatment. The α9 nicotinic acetylcholine receptor (nAChR) is shown to affect melanoma cell proliferation. Allium cepa L. var. proliferum Regel extract possesses anticancer properties. However, the mechanism of Allium cepa L. var. proliferum Regel extract in the antiproliferative effects of melanoma cells remains unclear. Using UPLC-ESI-MS/MS method, a total of 42 compounds were identified in Allium cepa L. var. proliferum Regel extract classified into five categories, including organosulfur compounds (962.20 ± 34.55 μg/g), polyphenols (100.40 ± 12.55 μg/g), flavonoids (58.36 ± 10.75 μg/g), organic acids (54.04 ± 2.69 μg/g), and alkaloids (15.08 ± 3.10 μg/g) where we found various bioactive components targeted to nAChRs. We analyzed the genetic dependency of α1-10 nAChRs from Achilles_CRISPR dataset (n=38) using CRISPR-Cas9 technology. α9-nAChR contributed significantly to the survival of melanoma cells (dependency scores < 0). We evaluated α1-10 nAChRs and PD-L1 mRNA expression from CCLE_Expression dataset (n=50). α9-nAChR was the only gene that strongly correlated to PD-L1 expression (r=0.6, p<0.001). There was also a strong correlation between α9-nAChR and PD-L1 expression (r=0.7, p<0.001) in the tissue microarray (n=192) using the IHC staining. Knockdown or overexpression of α9-nAChR significantly down- or upregulated the expression of PD-L1 via the transcription factor STAT3 binding to the PD-L1 promoter, respectively, and affected melanoma cell proliferation. Allium cepa L. var. proliferum Regel extract inhibited melanoma cell proliferation through inactivation of α9-nAChR/PD-L1 axis. Our results suggest that α9-nAChR/ PD-L1 axis regulates the cell proliferation of melanoma and Allium cepa L. var. proliferum Regel extract is considered as a potential candidate to prevent melanoma.

Loss of MHC Class I Expression in HPV-associated Cervical and Vulvar Neoplasia

Tumor cell expression of major histocompatibility complex (MHC) class I is required for antigen presentation and adaptive immune recognition. Absent or diminished MHC class I expression is thought to contribute to immunotherapeutic resistance in some epithelial tumors but has not been previously studied in cervical and vulvar carcinoma. Given that anti-programmed cell death 1 (PD-1) checkpoint inhibition is deployed for programmed cell death ligand 1 (PD-L1)-positive recurrent and metastatic cervical squamous carcinomas, identifying tumors with loss of MHC class I is of clinical interest to optimize the selection of immunotherapeutic candidates. Immunohistochemistry for PD-L1 and MHC class I combined A, B, and C heavy chains (MHC class I) was assessed in 58 human papillomavirus-associated cervical and vulvar lesions, including 27 squamous intraepithelial lesions (SILs) and 31 invasive squamous cell carcinoma (SCC). Although 84% of SCC and 22% of SIL were PD-L1-positive, 35.5% (11/31) of SCC and 18.5% (5/27) of SIL also showed clonal or complete loss of MHC class I. Loss of MHC class I expression was more common in PD-L1-positive (10/26, 38%) versus PD-L1-negative SCC (1/5, 20%). In summary, over one third of human papillomavirus-associated cervical and vulvar SCC show clonal or complete loss of MHC class I expression, including many PD-L1-positive cases. This suggests that the efficacy of checkpoint inhibitors targeting the PD-1/PD-L1 axis may be limited in a subset of cervical and vulvar squamous neoplasms due to an impaired ability to engage with the adaptive immune system related to loss of MHC class I expression.

Programmed Cell Death-1: Programmed Cell Death-Ligand 1 Interaction Protects Human Cardiomyocytes Against T-Cell Mediated Inflammation and Apoptosis Response In Vitro

Aim: Immunological checkpoint therapy is considered a powerful method for cancer therapy and acts by re-activating autologous T cells to kill the cancer cell. Myocarditis cases have been reported in cancer patients after immunological therapy; for example, nivolumab treatment is a monoclonal antibody that blocks programmed cell death-1/programmed cell death ligand-1 ligand interaction. This project provided insight into the inflammatory response as a benchmark to investigate the potential cardiotoxic effect of T cell response to the programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) axis in regulating cardiomyocyte injury in vitro. Methods and Results: We investigated cardiomyopathy resulted from the PD-1/PD-L1 axis blockade using the anti-PD-1 antibody in Rockefeller University embryonic stem cells-derived cardiomyocytes (RUES2-CMs) and a melanoma tumor-bearing murine model. We found that nivolumab alone did not induce inflammatory-related proteins, including PD-L1 expression, and did not induce apoptosis, which was contrary to doxorubicin, a cardiotoxic chemotherapy drug. However, nivolumab was able to exacerbate the immune response by increasing cytokine and inflammatory gene expression in RUES2-CMs when co-cultured with CD4+ T lymphocytes and induced apoptosis. This effect was not observed when RUES2-CMs were co-cultured with CD8+ T lymphocytes. The in vivo model showed that the heart function of tumor-bearing mice was decreased after treatment with anti-PD-1 antibody and demonstrated a dilated left ventricle histological examination. The dilated left ventricle was associated with an infiltration of CD4+ and CD8+ T lymphocytes into the myocardium. PD-L1 and inflammatory-associated gene expression were significantly increased in anti-PD-1-treated tumor-bearing mice. Cleaved caspase-3 and mouse plasma cardiac troponin I expressions were increased significantly. Conclusion: PD-L1 expression on cardiomyocytes suppressed T-cell function. Blockade of PD-1 by nivolumab enhanced cardiomyocyte inflammation and apoptosis through the enhancement of T-cell response towards cardiomyocytes.

Polydatin Exerts an Antitumor Effect Through Regulating the miR-382/PD-L1 Axis in Colorectal Cancer.

Background: Colorectal cancer (CRC) is considered as one of the most lethal malignancies worldwide. However, the effective therapies remain limited. Polydatin, a main effective component of the Chinese herb Polygonum cuspidatum, has multiple antitumor activities; however, whether Polydatin has anti-CRC activity is not fully understood. Materials and Methods: CRC cell proliferation and apoptosis were measured after treatment of Polydatin using Cell Counting Kit-8 assay, colony formation assay, and flow cytometer assay. The expression of miR-382 and programmed cell death ligand 1 (PD-L1) were determined in CRC cell lines by quantitative real-time polymerase chain reaction and Western blot, respectively. Furthermore, dual-luciferase reporter assay was conducted to determine the target of miR-382. Moreover, loss-of-functional experiments were used to identify the effect of Polydatin on miR-382. Finally, tumor xenograft experiments were conducted to determine the effect of Polydatin in vivo. Results: As a result, Polydatin effectively inhibited cell proliferation and promoted cell apoptosis in CRC cell lines. PD-L1 was confirmed as a direct target of miR-382. Furthermore, Polydatin could suppress the expression of PD-L1 by upregulating miR-382. Moreover, Polydatin inhibits proliferation and promotes apoptosis of CRC cells by regulating miR-382 and suppressing CRC tumor growth in vivo. Conclusion: Polydatin inhibits CRC cell proliferation and promotes apoptosis by regulating miR-382/PD-L1 axis. Polydatin could be a potential compound to synthesize novel antitumor drugs.

An update of knowledge on PD-L1 in head and neck cancers: Physiologic, prognostic and therapeutic perspectives.

Programmed cell death-ligand 1 (PD-L1) is a transmembrane protein that acts as a co-inhibitory factor in the immune response. Its receptor, programmed cell death protein 1 (PD-1), is found on immune cells, where binding to PD-L1 can reduce the proliferation of PD-1-positive cells, inhibit their cytokine secretion and induce apoptosis. PD-L1 in immune-privileged tissue plays a crucial role in peripheral tolerance. PD-L1 can be overexpressed in various malignancies, including oral squamous cell carcinoma, where it can attenuate the host immune response to tumour cells and has been associated with a worse prognosis. Monoclonal antibody therapies targeting the PD-1:PD-L1 axis have shown initial promise, but further research is needed to identify which patients will benefit. We provide an update of knowledge on PD-L1, including its structure, function and regulation. We also review studies on the overexpression of PD-L1 in cancer, specifically oral squamous cell carcinoma, and explore its potential value as a therapeutic target.

PD-1/PD-L1 Axis, Rather Than High-Mobility Group Alarmins or CD8+ Tumor-Infiltrating Lymphocytes, Is Associated With Survival in Head and Neck Squamous Cell Carcinoma Patients Who Received Surgical Resection.

In current studies, the influence of tumor immune microenvironment on tumorigenesis and tumor progression has been widely explored. In the present study, we investigated the expression and significance of high mobility group box 1 (HMGB1), HMG nucleosome-binding protein 1 (HMGN1), the receptor programmed cell death 1 (PD-1) and its ligand programmed cell death ligand 1 (PD-L1) in head and neck squamous cell carcinoma (HNSCC). We explored whether HMGB1 and HMGN1 take part in recruiting T cells to HNSCC microenvironment. Furthermore, we assessed the prognostic value of HMG proteins, TILs, and PD-1/PD-L1 in postoperative patients. Tumor tissue sections were collected from 81 cases of patients with resectable HNSCC. All patients' information was integrated with clinical and pathological records, as well as follow-up data. We used immunohistochemistry to examine the subcellular localization and expression levels of HMGB1 and HMGN1, as well as tumor CD3+, CD8+, FOXP3+ lymphocyte infiltration, and the expression of immune inhibiting molecules PD-1/PD-L1. Results showed that there was no significant difference in the number of CD8+ and FOXP3+ T cells between the two groups with or without HMGB1 cytoplasmic expression in tumor tissues. The number of CD3+ T cells in HMGB1 cytoplasmic expression group (339.39 ± 230.76) was more than that in group without HMGB1 cytoplasmic expression (233.30 ± 230.91, P < 0.05). The number of CD3+, CD8+, and FOXP3+ T cells in HMGN1 cytoplasmic expression group [400.74 ± 224.04, 158.10 ± 112.10, 36.00(15.00, 69.00)] was more than that in group without HMGN1-cytoplasmic expression [222.84 ± 217.78, P < 0.01; 105.10 ± 108.25, P < 0.05; 13.00(6.75, 32.25), P < 0.01]. The positive rates of PD-1 and PD-L1 in tumor tissues were 29.6 and 67.9%, respectively. Multivariate analysis suggested that tumor expression of PD-L1 was an independent prognostic factor and PD-L1 overexpression indicated a poor overall survival (OS) and disease-free survival (DFS). Taken together, we concluded that HMGB1 and HMGN1 secreted by cancer cells may relate to recruitment of tumor infiltrating lymphocytes (TILs) in HNSCC. PD-1/PD-L1 axis, rather than HMG proteins or CD8+ tumor-infiltrating lymphocytes, has a critical role in tumor immune microenvironment and could predict the outcome of HNSCC patients who received surgical resection.

Osteoclast Immunosuppressive Effects in Multiple Myeloma: Role of Programmed Cell Death Ligand 1.

Immunomodulatory drugs and monoclonal antibody-based immunotherapies have significantly improved the prognosis of the patients with multiple myeloma (MM) in the recent years. These new classes of reagents target malignant plasma cells (PCs) and further modulate the immune microenvironment, which prolongs anti-MM responses and may prevent tumor occurrence. Since MM remains an incurable cancer for most patients, there continues to be a need to identify new tumor target molecules and investigate alternative cellular approaches using gene therapeutic strategies and novel treatment mechanisms. Osteoclasts (OCs), as critical multi-nucleated large cells responsible for bone destruction in >80% MM patients, have become an attractive cellular target for the development of novel MM immunotherapies. In MM, OCs are induced and activated by malignant PCs in a reciprocal manner, leading to osteolytic bone disease commonly associated with this malignancy. Significantly, bidirectional interactions between OCs and MM cells create a positive feedback loop to promote MM cell progression, increase angiogenesis, and inhibit immune surveillance via both cell–cell contact and abnormal production of multiple cytokines/chemokines. Most recently, hyper-activated OCs have been associated with activation of programmed cell death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway, which impairs T cell proliferation and cytotoxicity against MM cells. Importantly, therapeutic anti-CD38 monoclonal antibodies and checkpoint inhibitors can alleviate OC-induced immune suppression. Furthermore, a proliferation-inducing ligand, abundantly secreted by OCs and OC precursors, significantly upregulates PD-L1 expression on MM cells, in addition to directly promoting MM cell proliferation and survival. Coupled with increased PD-L1 expression in other immune-suppressive cells, i.e., myeloid-derived suppressor cells and tumor-associated macrophages, these results strongly suggest that OCs contribute to the immunosuppressive MM BM microenvironment. Based on these findings and ongoing osteoimmunology studies, therapeutic interventions targeting OC number and function are under development to diminish both MM bone disease and related immune suppression. In this review, we discuss the classical and novel roles of OCs in the patho-immunology of MM. We also describe novel therapeutic strategies simultaneously targeting OCs and MM interactions, including PD-1/PD-L1 axis, to overcome the immune-suppressive microenvironment and improve patient outcome.