Immune Checkpoint Blockade in Cancer Immunotherapy: Mechanisms, Clinical Outcomes, and Safety Profiles of PD-1/PD-L1 Inhibitors

PRPS2-mediated modulation of the antitumor immune response in lung cancer through CCL2-mediated tumor-associated macrophages and myeloid-derived suppressor cells

BACKGROUND

Phosphoribosyl pyrophosphate synthetase 2 (PRPS2) is known as an oncogene in many types of cancers, including lung cancer. However, its role in regulating tumor-associated macrophages (TAM) and myeloid-derived suppressor cells (MDSC) remains unclear. Our study aimed to explore the involvement of PRPS2 in TAM and MDSC regulation.

METHODS

Stable Lewis lung cancer (LLC) cell lines were established using a lentivirus system. These LLC lines were then used to establish tumor model in mice. The levels of target genes were determined using qPCR, western blotting, and ELISA assays. The percentage of different immune cell types was analyzed using fluorescence-activated cell sorting. The chemotaxis ability of TAM and MDSC was evaluated using an in vitro transwell chemotaxis assay.

RESULTS

Notably, PRPS2 was found to regulate the chemotaxis of TAM and MDSC in tumor cells, as evidenced by the positive correlation of PRPS2 expression levels and abundance of TAM and MDSC populations. In addition, the expression of CCL2, mediated by PRPS2, was identified as a key factor in the chemotaxis of TAM and MDSC, as evidenced by a significant reduction in macrophages and MDSC numbers in the presence of the CCL2 antibody. Furthermore, in vivo experiments confirmed the involvement of PRPS2 in mediating CCL2 expression. PRPS2 was also found to regulate immune cell infiltration into tumors, whereas knockdown of CCL2 reversed the phenotype induced by PRPS2 overexpression. In tumor tissues from mice implanted with LLC-PRPS2-shCCL2 cells, a notable increase in CD4+ and CD8+ T cell percentages, alongside a marked decrease in TAMs, M-MDSC, and PMN-MDSC, was observed.

CONCLUSION

Taken together, PRPS2 plays a crucial role in modulating the antitumor immune response by reprogramming CCL2-mediated TAM and MDSC.

Ganoderma lucidum spores-derived particulate β-glucan treatment improves antitumor response by regulating myeloid-derived suppressor cells in triple-negative breast cancer

Granular β-1,3-glucan extracted from the wall of Ganoderma lucidum spores, named GPG, is a bioregulator. In this study, we investigated the structural, thermal, and other physical properties of GPG. We determined whether GPG ameliorated immunosuppression caused by Gemcitabine (GEM) chemotherapy. Triple-negative breast cancer mice with GPG combined with GEM treatment had reduced tumor burdens. In addition, GEM treatment alone altered the tumor microenvironment(TME), including a reduction in antitumor T cells and a rise in myeloid-derived suppressor cells (MDSC) and regulatory T cells (Tregs). However, combined GPG treatment reversed the tumor immunosuppressive microenvironment induced by GEM. GPG inhibited bone marrow (BM)-derived MDSC differentiation and reversed MDSC expansion induced by conditioned medium (CM) in GEM-treated E0771 cells through a Dectin-1 pathway. In addition, GPG downgraded PD-L1 and IDO1 expression on MDSC while boosting MHC-II, CD86, TNF-α, and IL-6 expression. In conclusion, this study demonstrated that GPG could alleviate the adverse effects induced by GEM chemotherapy by regulating TME.

Hepatocellular Carcinoma: Beyond the Border of Advanced Stage Therapy

Hepatocellular carcinoma (HCC) is the deadliest emergent health issue around the globe. The stronger oncogenic effect, proteins, and weakened immune response are precisely linked with a significant prospect of developing HCC. Several conventional systemic therapies, antiangiogenic therapy, and immunotherapy techniques have significantly improved the outcomes for early-, intermediate-, and advanced-stage HCC patients, giving new hope for effective HCC management and prolonged survival rates. Innovative therapeutic approaches beyond conventional treatments have altered the landscape of managing HCC, particularly focusing on targeted therapies and immunotherapies. The advancement in HCC treatment suggested by the Food and Drug Administration is multidimensional treatment options, including multikinase inhibitors (sorafenib, lenvatinib, regorafenib, ramucirumab, and cabozantinib) and immune checkpoint inhibitors (atezolizumab, pembrolizumab, durvalumab, tremelimumab, ipilimumab, and nivolumab), in monotherapy and in combination therapy to increase life expectancy of HCC patients. This review highlights the efficacy of multikinase inhibitors and immune checkpoint inhibitors in monotherapy and combination therapy through the analysis of phase II, and III clinical trials, targeting the key molecular pathways involved in cellular signaling and immune response for the prospective treatment of advanced and unresectable HCC and discusses the upcoming combinations of immune checkpoint inhibitors-tyrosine kinase inhibitors and immune checkpoint inhibitors-vascular endothelial growth factor inhibitors. Finally, the hidden challenges with pharmacological therapy for HCC, feasible solutions for the future, and implications of possible presumptions to develop drugs for HCC treatment are reported.

Improving tumor sensitivity by the introduction of an ester chain to triaryl derivatives targeting PD-1/PD-L1

PD-1/PD-L1 pathway blockade is a promising immunotherapy for the treatment of cancer. In this manuscript, a series of triaryl compounds containing ester chains were designed and synthesized based on the pharmacophore studies of the lead BMS-1. After several SAR iterations, 22 showed the best biochemical activity binding to hPD-L1 with an IC50 of 1.21 nM in HTRF assay, and a KD value of 5.068 nM in SPR analysis. Cell-based experiments showed that 22 effectively promoted A549 cell death by restoring T-cell immune function. 22 showed significant in vivo antitumor activity in a 4T1 mouse model without obvious toxicity, with a TGI rate of 67.8 % (20 mg/kg, ip). Immunohistochemistry data indicated that 22 activates the immune activity in tumors. These results suggest that 22 is a promising compound for further development of PD-1/PD-L1 inhibitor for cancer therapy.

B cells in head and neck squamous cell carcinoma: current opinion and novel therapy

Head and neck squamous cell carcinoma (HNSCC) is a common malignant tumour. Despite advancements in surgery, radiotherapy and chemotherapy, which have improved the prognosis of most patients, a subset of patients with poor prognoses still exist due to loss of surgical opportunities, postoperative recurrence, and metastasis, among other reasons. The tumour microenvironment (TME) is a complex organization composed of tumour, stromal, and endothelial cells. Communication and interaction between tumours and immune cells within the TME are increasingly being recognized as pivotal in inhibiting or promoting tumour development. Previous studies on T cells in the TME of HNSCC have yielded novel therapeutic possibilities. However, the function of B cells, another adaptive immune cell type, in the TME of HNSCC patients has yet to be determined. Recent studies have revealed various distinct subtypes of B cells and tertiary lymphoid structures (TLSs) in the TME of HNSCC patients, which are believed to impact the efficacy of immune checkpoint inhibitors (ICIs). Therefore, this paper focuses on B cells in the TME to explore potential directions for future immunotherapy for HNSCC.

β-Glucan-conjugated anti-PD-L1 antibody enhances antitumor efficacy in preclinical mouse models

The use of immune checkpoint blockade (ICB) is a promising approach for clinical cancer treatment. However, most of cancer patients do not respond to anti-PD-1/PD-L1 antibody. In this study, we proposed a novel strategy of antibody-β-glucan conjugates (AGC) to enhance the antitumor immune response to ICB therapy. The AGC were constructed by conjugating an anti-PD-L1 antibody with a β-glucan via click chemistry. This design facilitates the delivery of β-glucan into the tumor microenvironment (TME). Furthermore, the bridging effect mediated by AGC can promote the interaction between tumor cells and dendritic cells (DCs), thereby enhancing immunotherapeutic benefits. In the MC38 tumor-bearing mouse model, AGC demonstrated powerful tumor suppression, achieving a tumor suppression rate of 86.7 %. Immunophenotyping, cytokine analysis, RNA sequencing, and FTY720-treated models were combined to elucidate the mechanism underlying AGC function. Compared with anti-PD-L1 antibody, AGC induced an earlier immune response, infiltration of DCs, and activation of preexisting T cells in the TME, with T cells predominantly proliferating locally rather than migrating from other organs. In conclusion, these data suggest that AGC could serve as a promising strategy to improve ICB therapy with prospects for clinical utilization.

Inhibitors of Immune Checkpoints: Small Molecule- and Peptide-Based Approaches

The revolutionary progress in cancer immunotherapy, particularly the advent of immune checkpoint inhibitors, marks a significant milestone in the fight against malignancies. However, the majority of clinically employed immune checkpoint inhibitors are monoclonal antibodies (mAbs) with several limitations, such as poor oral bioavailability and immune-related adverse effects (irAEs). Another major limitation is the restriction of the efficacy of mAbs to a subset of cancer patients, which triggered extensive research efforts to identify alternative approaches in targeting immune checkpoints aiming to overcome the restricted efficacy of mAbs. This comprehensive review aims to explore the cutting-edge developments in targeting immune checkpoints, focusing on both small molecule- and peptide-based approaches. By delving into drug discovery platforms, we provide insights into the diverse strategies employed to identify and optimize small molecules and peptides as inhibitors of immune checkpoints. In addition, we discuss recent advances in nanomaterials as drug carriers, providing a basis for the development of small molecule- and peptide-based platforms for cancer immunotherapy. Ongoing research focused on the discovery of small molecules and peptide-inspired agents targeting immune checkpoints paves the way for developing orally bioavailable agents as the next-generation cancer immunotherapies.

The expression mechanism of programmed cell death 1 ligand 1 and its role in immunomodulatory ability of mesenchymal stem cells

Programmed cell death 1 ligand 1 (PD-L1) is an important immunosuppressive molecule, which inhibits the function of T cells and other immune cells by binding to the receptor programmed cell death-1. The PD-L1 expression disorder plays an important role in the occurrence, development, and treatment of sepsis or other inflammatory diseases, and has become an important target for the treatment of these diseases. Mesenchymal stem cells (MSCs) are a kind of pluripotent stem cells with multiple differentiation potential. In recent years, MSCs have been found to have a strong immunosuppressive ability and are used to treat various inflammatory insults caused by hyperimmune diseases. Moreover, PD-L1 is deeply involved in the immunosuppressive events of MSCs and plays an important role in the treatment of various diseases. In this review, we will summarize the main regulatory mechanism of PD-L1 expression, and discuss various biological functions of PD-L1 in the immune regulation of MSCs.

Analysis of long non-coding RNAs associated with disulfidptosis for prognostic signature and immunotherapy response in uterine corpus endometrial carcinoma

Disulfidptosis, the demise of cells caused by the abnormal breakdown of disulfide bonds and actin in the cytoprotein backbone, has attracted attention in studies concerning disulfide-related cell death and its potential implications in cancer treatment. This study utilized bioinformatics to detect disulfidptosis associated lncRNA prognostic markers (DALPMs) with Uterine Corpus Endometrial Carcinoma (UCEC)-related to investigate the correlation between these indicators and the tumor immune microenvironment. The RNA sequencing data and somatic mutation information of patients with UCEC were obtained from the Cancer Genome Atlas (TCGA) database. Patients were randomly divided into Train and Test groups. The findings revealed a potential prognostic model comprising 14 DALPMs. Both univariate and multivariate Cox analyses demonstrated that the model-derived risk score functioned as a standalone prognostic indicator for patients. Significant disparities in survival outcomes were observed between the high- and low-risk groups as defined by the model. Differences in tumor mutational burden (TMB), tumor immune dysfunction and exclusion (TIDE), and tumor microenvironment (TME) stromal cells between patients of the high- and low-risk groups were also observed. The forecast model comprising long non-coding RNAs (lncRNAs) associated with disulfidptosis can effectively anticipate patients' prognoses.

Methylation of hypoxia-inducible factor 3 subunit alpha contributes to poor prognosis in lung adenocarcinoma

Hypoxia-inducible factor 3 subunit alpha (HIF3A) has been implicated in various types of cancers, while its precise role in the lung adenocarcinoma remains unclear. Our study aimed to investigate the roles of HIF3A in lung adenocarcinoma and its regulation by DNA methylation. We utilized bioinformatic tools, including UALCAN and KMPlot, to analyze the relationship between HIF3A expression, DNA methylation, and patient survival rate in lung adenocarcinoma. We also used siRNA-mediated knockdown of HIF3A and DNA-methyltransferase 1 (DNMT1), as well as the treatment of DNA methylation inhibitor 5-Azacytidine, in A549 and H1299 lung adenocarcinoma cell lines. qPCR, MTT, and cell counting assays were performed to evaluate the mRNA expression and cell viability. The bioinformatic analysis revealed that HIF3A expression was downregulated and its methylation was upregulated in lung tumor tissues. Additionally, Kaplan-Meier analysis indicated a correlation between low HIF3A expression and patient poor survival rate. We found that DNMT1 regulated HIF3A methylation. Knockdown of HIF3A promoted cancer cell proliferation. These data suggest that downregulation of HIF3A promotes tumor cell proliferation, and support that HIF3A methylation may serve as a prognostic factor for lung adenocarcinoma.

Integrative landscape analysis of prognostic model biomarkers and immunogenomics of disulfidptosis-related genes in breast cancer based on LASSO and WGCNA analyses

BACKGROUND

Disulfidptosis is a novel type of programmed cell death. However, the value of disulfidptosis-related genes (DRGs) in the prediction of breast cancer prognosis is unclear.

METHODS

RNA-seq data of 1231 patients, together with information on patient clinical characteristics and prognosis, were downloaded from TCGA. DRGs were identified between cancerous and non-cancerous tissues. The LASSO algorithm was used to assign half of the samples to the training set. Risk scores were used for construction of a prognostic model for risk stratification and prognosis prediction, and the clinical applicability was examined using a line diagram. The relationships between risk scores, immune cell infiltration, molecular subtypes, and responses to immunotherapy and chemotherapy were examined.

RESULTS

We identified and obtained four DRG-related prognostic lncRNAs (AC009097.2, AC133552.5, YTHDF3-AS1, and AC084824.5), which were used for establishing the risk model. Longer survival was associated with low risk. The DRG-associated lncRNAs were found to independently predict patient prognosis. The AUCs under the ROCs for one-, three-, and 5-year survival in the training cohort were 0.720, 0.687, and 0.692, respectively. The model showed that the high-risk patients had reduced overall survival as well as high tumor mutation burdens. Furthermore, high-risk patients showed increased sensitivity to therapeutic drugs, including docetaxel, paclitaxel, and oxaliplatin.

CONCLUSION

The risk score model was effective for predicting both prognosis and sensitivity to therapeutic drugs, suggesting its possible usefulness for the management of patients with breast cancer.

Effect of Fragment 1 on the Binding of Epigallocatechin Gallate to the PD-L1 Dimer Explored by Molecular Dynamics

Blocking the interaction between programmed cell death-1 (PD-1) and programmed cell death-ligand 1 (PD-L1) by directly targeting the PD-L1 dimer has emerged as a hot topic in the field of cancer immunotherapy. Epigallocatechin gallate (EGCG), a natural product, has been demonstrated binding to the PD-L1 dimer in our previous study, but has a weaker binding capacity, moreover, EGCG is located at the end of the binding pocket of the PD-L1 dimer. The inhibitor fragment 1 (FRA) lies at the other end. So, we proposed that the introduction of FRA might be able to improve the binding ability. To illuminate this issue, molecular dynamics (MD) simulation was performed in the present study. Binding free energy calculations show that the binding affinity is significantly increased by 17 kcal/mol upon the introduction of FRA. It may be due to the energy contributions of emerging key residues ATyr56, AMet115, BTyr123, AIle54 and the enhanced contributions of initial key residues ATyr123 and BVal68. Binding mode and non-bonded interaction results indicate that FRA_EGCG (EGCG in combination with FRA) binds to the C-, F- and G-sheet of the PD-L1 dimer. Importantly, the introduction of FRA mainly strengthened the nonpolar interactions. The free energy landscape and secondary structure results further show that FRA_EGCG can interact with the PD-L1 dimer more stably. These data demonstrated here provide the theoretical basis for screening two or more natural products with additive inhibitory effect on this pathway and therefore exerting more effective anticancer immunity.

[89Zr]-Atezolizumab-PET Imaging Reveals Longitudinal Alterations in PDL1 during Therapy in TNBC Preclinical Models

Triple-negative breast cancers (TNBCs) currently have limited treatment options; however, PD-L1 is an indicator of susceptibility to immunotherapy. Currently, assessment of PD-L1 is limited to biopsy samples. These limitations may be overcome with molecular imaging. In this work, we describe chemistry development and optimization, in vitro, in vivo, and dosimetry of [89Zr]-Atezolizumab for PD-L1 imaging. Atezolizumab was conjugated to DFO and radiolabeled with 89Zr. Tumor uptake and heterogeneity in TNBC xenograft and patient-derived xenograft (PDX) mouse models were quantified following [89Zr]-Atezolizumab-PET imaging. PD-L1 expression in TNBC PDX models undergoing therapy and immunohistochemistry (IHC) was used to validate imaging. SUV from PET imaging was quantified and used to identify heterogeneity. PET/CT imaging using [89Zr]-Atezolizumab identified a significant increase in tumor:muscle SUVmean 1 and 4 days after niraparib therapy and revealed an increased trend in PD-L1 expression following other cytotoxic therapies. A preliminary dosimetry study indicated the organs that will receive a higher dose are the spleen, adrenals, kidneys, and liver. [89Zr]-Atezolizumab PET/CT imaging reveals potential for the noninvasive detection of PD-L1-positive TNBC tumors and allows for quantitative and longitudinal assessment. This has potential significance for understanding tumor heterogeneity and monitoring early expression changes in PD-L1 induced by therapy.

Dissecting the roles and clinical potential of YY1 in the tumor microenvironment

Yin-Yang 1 (YY1) is a member of the GLI-Kruppel family of zinc finger proteins and plays a vital dual biological role in cancer as an oncogene or a tumor suppressor during tumorigenesis and tumor progression. The tumor microenvironment (TME) is identified as the “soil” of tumor that has a critical role in both tumor growth and metastasis. Many studies have found that YY1 is closely related to the remodeling and regulation of the TME. Herein, we reviewed the expression pattern of YY1 in tumors and summarized the function and mechanism of YY1 in regulating tumor angiogenesis, immune and metabolism. In addition, we discussed the potential value of YY1 in tumor diagnosis and treatment and provided a novel molecular strategy for the clinical diagnosis and treatment of tumors.

PD-1/PD-L1 and DNA Damage Response in Cancer

The application of immunotherapy for cancer treatment is rapidly becoming more widespread. Immunotherapeutic agents are frequently combined with various types of treatments to obtain a more durable antitumor clinical response in patients who have developed resistance to monotherapy. Chemotherapeutic drugs that induce DNA damage and trigger DNA damage response (DDR) frequently induce an increase in the expression of the programmed death ligand-1 (PD-L1) that can be employed by cancer cells to avoid immune surveillance. PD-L1 exposed on cancer cells can in turn be targeted to re-establish the immune-reactive tumor microenvironment, which ultimately increases the tumor's susceptibility to combined therapies. Here we review the recent advances in how the DDR regulates PD-L1 expression and point out the effect of etoposide, irinotecan, and platinum compounds on the anti-tumor immune response.

GPR65 as a potential immune checkpoint regulates the immune microenvironment according to pan-cancer analysis

It has been reported that inhibition of GPR65 may be effective for the treatment of certain cancers. Nevertheless, the role of GPR65 in various cancers remains unknown. We conducted an exhaustive pan-cancer analysis of GPR65 using multiple databases, including TCGA, GTEx, BioGPS, HPA, cBioPortal, and GeneCards. GPR65 was found to be differentially expressed in various cancers and linked to tumor mutational burden (TMB), microsatellite instability (MSI), and Ploidy, playing a key function in the tumor microenvironment (TME). It is closely linked to the development of Th17 cells as well as Th1 and Th2 cells in certain cancers. Our findings indicate that the expression of GPR65 is highly linked with clinical prognosis, mutations, and immune cell infiltration. It was revealed as an indicator of patient prognosis as well as a possible immunomodulatory role. As a possible new immunological checkpoint, GPR65 could be a target for tumor immunotherapy.

IL2RA is a prognostic indicator and correlated with immune characteristics of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive and incurable cancer with a dismal prognosis. In this study, we aimed to explore potential predictors for the prognosis and immunological characteristics of PDAC. Estimation of stromal and immune cells in malignant tumors, using expression data (ESTIMATE) method was applied to calculate the immune and stromal scores of 206 PDAC samples from GSE71729. R package of "limma" was utilized to identify differentially expressed genes (DEGs). Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses were conducted for functional exploration. Protein-protein interaction (PPI) network and Univariate Cox analysis were conducted to select key prognostic genes of PDAC. Gene set enrichment analysis (GSEA) was applied to investigate the roles of IL2RA in PDAC. Single sample GSEA (ssGSEA) was performed to evaluate the immunological characteristics of PDAC samples. Wilcoxon rank sum test was conducted to compare the difference of immunological characteristics of PDAC samples between low IL2RA and high IL2RA. Spearman correlation analysis was used to explore the correlations of IL2RA expression and immune checkpoint genes. A total of 747 DEGs were identified between low and high immune/stromal groups. Functional exploration revealed upregulated DEGs were associated with immune-related activities, whereas downregulated DEGs were involved in inflammatory-related activities. IL2RA was selected as the critical gene by overlapping the hub genes in PPI network and prognostic genes. Significantly, IL2RA expression was significantly elevated in PDAC and patients with higher IL2RA expression had worse prognoses. The immunological and oncogenic roles of IL2RA in PDAC were evidenced by GSEA. Furthermore, PDAC samples with high IL2RA expression exhibited increased immune infiltration and better immunotherapy responses. IL2RA expression was positively correlated with PDCD1, CD274, CTLA4, IDO1, TDO2, and TIGT. Higher expression of IL2RA predicts worse survival outcomes and increased immune infiltration in PDAC. PDAC patients with high IL2RA expression might potentially benefit from immunotherapy.

Crosstalk between angiogenesis and immune regulation in the tumor microenvironment

Cancer creates a complex tumor microenvironment (TME) composed of immune cells, stromal cells, blood vessels, and various other cellular and extracellular elements. It is essential for the development of anti-cancer combination therapies to understand and overcome this high heterogeneity and complexity as well as the dynamic interactions between them within the TME. Recent treatment strategies incorporating immune-checkpoint inhibitors and anti-angiogenic agents have brought many changes and advances in clinical cancer treatment. However, there are still challenges for immune suppressive tumors, which are characterized by a lack of T cell infiltration and treatment resistance. In this review, we will investigate the crosstalk between immunity and angiogenesis in the TME. In addition, we will look at strategies designed to enhance anti-cancer immunity, to convert “immune suppressive tumors” into “immune activating tumors,” and the mechanisms by which these strategies enhance effector immune cell infiltration.

B Cell Function in the Tumor Microenvironment

The tumor microenvironment (TME) is a heterogeneous, complex organization composed of tumor, stroma, and endothelial cells that is characterized by cross talk between tumor and innate and adaptive immune cells. Over the last decade, it has become increasingly clear that the immune cells in the TME play a critical role in controlling or promoting tumor growth. The function of T lymphocytes in this process has been well characterized. On the other hand, the function of B lymphocytes is less clear, although recent data from our group and others have strongly indicated a critical role for B cells in antitumor immunity. There are, however, a multitude of populations of B cells found within the TME, ranging from naive B cells all the way to terminally differentiated plasma cells and memory B cells. Here, we characterize the role of B cells in the TME in both animal models and patients, with an emphasis on dissecting how B cell heterogeneity contributes to the immune response to cancer.

What Happens to the Immune Microenvironment After PD-1 Inhibitor Therapy?

The fruitful results of tumor immunotherapy establish its indispensable status in the regulation of the tumorous immune context. It seems that the treatment of programmed cell death receptor 1 (PD-1) blockade is one of the most promising approaches for cancer control. The significant efficacy of PD-1 inhibitor therapy has been made in several cancer types, such as breast cancer, lung cancer, and multiple myeloma. Even so, the mechanisms of how anti-PD-1 therapy takes effect by impacting the immune microenvironment and how partial patients acquire the resistance to PD-1 blockade have yet to be studied. In this review, we discuss the cross talk between immune cells and how they promote PD-1 blockade efficacy. In addition, we also depict factors that may underlie tumor resistance to PD-1 blockade and feasible solutions in combination with it.

Efficacy and safety of PD-1/PD-L1 inhibitors combined with CTLA-4 inhibitor versus chemotherapy for advanced lung cancer: A meta-analysis

BACKGROUND

This meta-analysis was performed to compare efficacy and tolerability between antiprogrammed cell death (PD-1)/programmed cell death-ligand-1 (PD-L1) + anticytotoxic T-lymphocyte-associated protein-4 (CTLA-4) treatment and chemotherapy in advanced lung cancer.

METHODS

Cochrane Library, Embase, and PubMed databases were searched for potential articles. The fixed-effect model or random-effect model was adopted for pooled analysis based on the I2 and P-value.

RESULTS

Six articles with 1338 patients were identified and subjected to meta-analysis. Compared with chemotherapy, anti-PD-1/PD-L1 + anti-CTLA-4 treatment could significantly improve the overall survival (hazard ratio [HR] = 0.78, 95%confidence interval [CI]: 0.71-0.84, P = .21) and progression-free survival (HR = 0.77, 95%CI: 0.71-0.83, P = .30) of advanced lung cancer patients. Moreover, there was no obvious difference in the incidence of 3 to 4 adverse events (AEs) serious adverse reactions (HR = 1.35, 95%CI: 0.66-2.74, P < .00001) between the 2 treatment groups, but the incidence rates of AEs leading to discontinuation (HR = 2.56, 95%CI: 1.53-4.30, P < .00001) and AEs leading to death (HR = 2.10, 95%CI: 1.21-3.63, P = .20) were higher. Furthermore, no remarkable differences in objective response rate (HR = 1.31, 95%CI: 0.97-1.77, P = .02) were observed between the 2 groups.

CONCLUSION

Our meta-analysis revealed that PD-1/PD-L1 inhibitors plus CTLA-4 inhibitor could markedly improve the endpoint outcomes of patients compared with chemotherapy alone, and did not significantly increase the serious adverse reactions. Thus, it can serve as a new treatment strategy for advanced lung cancer.

Discovery of phenyl-linked symmetric small molecules as inhibitors of the programmed cell death-1/programmed cell death-ligand 1 interaction

Programmed cell death-1/programmed cell death ligand 1 (PD-1/PD-L1) is one of the most promising targets in the field of immune checkpoint blockade therapy. Beginning with our exploration of linkers and structure-activity relationship research, we found that the aromatic ring could replace the linker and aryl group to maintain the satisfactory activity of classic triaryl scaffold inhibitor. Based on previous studies, we designed and synthesized a series of C₂-symmetric phenyl-linked compounds, and further tail optimization afforded the inhibitors, which displayed promising inhibitory activity against the PD-1/PD-L1 interaction with IC₅₀ value at the single nanomolar range (C13-C15). Further cell-based PD-1/PD-L1 blockade bioassays indicated that these C₂-symmetric molecules could significantly inhibit the PD-1/PD-L1 interaction at the cellular level and restore T cells' immune function at the safety concentrations. The discovery of these phenyl-linked symmetric small molecules showed the potential of simplified-linker and C₂-symmetric strategy and provided a basis for developing symmetric small molecule inhibitors of PD-1/PD-L1 interaction. Moreover, C13 and C15 performed stable binding modes to PD-L1 dimeric after computational docking and dynamic simulation, which may serve as a good starting point for further development.

A clinically acceptable strategy for sensitizing anti-PD-1 treatment by hypoxia relief

The hypoxic tumor microenvironment (TME) hinders the effectiveness of immunotherapy. Alleviating tumor hypoxia to improve the efficacy of immune checkpoint inhibitors (ICIs) represented by programmed cell death protein 1 (PD-1) antibody has become a meaningful strategy. In this study, we adopted three methods to alleviate hypoxia, including direct oxygen delivery using two different carriers and an indirect way involving HIF-1α inhibition. Both in vivo and in vitro experiments showed that liposomes modified with perfluorocarbon or hemoglobin (PFC@lipo or Hb@lipo) were able to efficiently load and release oxygen, relieving tumor hypoxia. However, the gas release behavior of PFC@lipo was uncontrollable, which might induce acute hyperoxia side effects during intravenous injection and reduce its biosafety. In contrast, whether administered locally or systemically, Hb@lipo revealed high animal tolerance, and was much safer than commercial HIF-1α inhibitor (PX-478), displaying prospects as a promising oxygen carrier for clinical practice. Pharmacodynamic experiments suggested that Hb@lipo helped PD-1 antibody break the therapeutic bottleneck and significantly inhibited the progression of 4 T1 breast cancer. But in CT26 colon cancer, the combination therapy failed to suppress tumor growth. After in-depth analysis and comparison, we found that the ratio of M1/M2 tumor associated macrophages (TAMs) between these two tumor models were dramatically different. And the lower M1/M2 ratio in CT26 tumors limited the anti-tumor effect of combination therapy. In this study, three methods for alleviating tumor hypoxia were compared from the perspectives of biosafety, efficacy and clinical applicability. Among them, Hb@lipo stood out, and its combined use with PD-1 antibody exhibit a distinct synergistic suppression effect on tumors with more M1 macrophages presented in the microenvironment. Our work provided a good reference for improving the efficacy of PD-1 antibody by alleviating tumor hypoxia.

Small molecule inhibitors against PD-1/PD-L1 immune checkpoints and current methodologies for their development: a review

Programmed death-1/programmed death ligand-1 (PD-1/PD-L1) based immunotherapy is a revolutionary cancer therapy with great clinical success. The majority of clinically used PD-1/PD-L1 inhibitors are monoclonal antibodies but their applications are limited due to their poor oral bioavailability and immune-related adverse effects (irAEs). In contrast, several small molecule inhibitors against PD-1/PD-L1 immune checkpoints show promising blockage effects on PD-1/PD-L1 interactions without irAEs. However, proper analytical methods and bioassays are required to effectively screen small molecule derived PD-1/PD-L1 inhibitors. Herein, we summarize the biophysical and biochemical assays currently employed for the measurements of binding capacities, molecular interactions, and blocking effects of small molecule inhibitors on PD-1/PD-L1. In addition, the discovery of natural products based PD-1/PD-L1 antagonists utilizing these screening assays are reviewed. Potential pitfalls for obtaining false leading compounds as PD-1/PD-L1 inhibitors by using certain binding bioassays are also discussed in this review.