A three-phase trans-ethnic study reveals B7-H3 expression is a significant and independent biomarker associated with colon cancer overall survival

BACKGROUND

There have been inconsistent results and conflicting conclusions among the existing prognostic studies of B7-H3 expression in colon cancer patients. Therefore, the association between B7-H3 expression and colon cancer survival has remained largely unclear.

METHODS

We performed a three-phase and trans-ethnic prognostic study of B7-H3 expression in colon cancer patients involving perhaps the largest population to date. In the discovery phase, we utilized a Cox proportional hazards model adjusted for covariates to test the association between B7-H3 expression and colon cancer overall survival (OS) time in a European population from The Cancer Genome Atlas (TCGA) cohort (n=433). In the validation phase I, the association was replicated in a European population from Gene Expression Omnibus (GEO) cohort (n=811). In the validation phase II, we again confirmed the significant association in an Asian population from Fujian Medical University Union Hospital (UNION) cohort (n=179). Furthermore, a series of Kaplan-Meier analysis, bioinformatics analysis of tumor immune microenvironment (TIME), and immune checkpoint prognostic prediction analysis, as well as sensitivity analysis, were also conducted.

RESULTS

Highly expressed B7-H3 was a significant and robust biomarker to colon cancer survival, with a large hazard ratio (HR) [HRTCGA =4.60, 95% confidence interval (CI): 2.15 to 9.83, P=8.37×10-05; HRGEO =1.47, 95% CI: 1.12 to 1.94, P=0.0056; HRUNION =1.63, 95% CI: 1.36 to 1.95, P=7.91×10-08]. We detected an involvement of B7-H3 in the tumor immune microenvironment (TIME). Meanwhile, B7-H3 was significantly and weakly correlated with 6 out of 27 well-recognized immune checkpoint genes. Even after adjusting for effects of other immune checkpoint genes, B7-H3 still exhibited a harmful effect on colon cancer survival using samples from TCGA and GEO cohorts (HR =1.47, 95% CI: 1.07 to 2.02, P=0.0184), indicating that it was an independent prognostic factor of colon cancer. We also proposed an immune checkpoint prognostic risk score which possessed the capability to identify colon cancers with high risk of mortality.

CONCLUSIONS

The expression of B7-H3 is a significant, robust, and independent prognostic factor to colon cancer OS.

The role of B7-H3 in tumors and its potential in clinical application

B7-H3 (CD276 molecule) is an immune checkpoint from the B7 family of molecules that acts more as a co-inhibitory molecule to promote tumor progression. It is abnormally expressed on tumor cells and can be induced to express on antigen-presenting cells (APCs) including dendritic cells (DCs) and macrophages. In the tumor microenvironment (TME), B7-H3 promotes tumor progression by impairing T cell response, promoting the polarization of tumor-associated macrophages (TAMs) to M2, inhibiting the function of DCs, and promoting the migration and invasion of cancer-associated fibroblasts (CAFs). In addition, through non-immunological functions, B7-H3 promotes tumor cell proliferation, invasion, metastasis, resistance, angiogenesis, and metabolism, or in the form of exosomes to promote tumor progression. In this process, microRNAs can regulate the expression of B7-H3. B7-H3 may serve as a potential biomarker for tumor diagnosis and a marker of poor prognosis. Immunotherapy targeting B7-H3 and the combination of B7-H3 and other immune checkpoints have shown certain efficacy. In this review, we summarized the basic characteristics of B7-H3 and its mechanism to promote tumor progression by inducing immunosuppression and non-immunological functions, as well as the potential clinical applications of B7-H3 and immunotherapy based on B7-H3.

Targeting the immune checkpoint B7-H3 for next-generation cancer immunotherapy

Immune checkpoint inhibitors (ICIs) for programmed death-1 (PD-1) and programmed cell death-ligand 1 (PD-L1) have become preferred treatment strategies for several advanced cancers. However, response rates for these treatments are limited, which encourages the search for new ICI candidates. Recent reports have underscored significant roles of B7 homolog 3 protein (B7-H3) in tumor immunity and disease progression. While its multifaceted roles are being elucidated, B7-H3 has already entered clinical trials as a therapeutic target. In this review, we overview the recent results of clinical trials evaluating the antitumor activity and safety of B7-H3 targeting drugs. On this basis, we also discuss the challenges and opportunities arising from the application of these drugs. Finally, we point out current gaps to address in the understanding of B7-H3 function and regulation in order to fully unleash the future clinical utility of B7-H3-based therapies for the treatment of cancer.

Multi-Omics Data Analyses Identify B7-H3 as a Novel Prognostic Biomarker and Predict Response to Immune Checkpoint Blockade in Head and Neck Squamous Cell Carcinoma

B7 homolog 3 (B7-H3) is a recently found superfamily B7 molecule and therefore has significant involvement in immunological regulation. However, the relationships of B7-H3 expression with the tumor microenvironment (TME), response to immunotherapy, and prognosis in head and neck squamous cell carcinoma (HNSCC) are still unknown. In the present analysis, we determined B7-H3 as a novel biomarker that predicts the prognosis and response to immunotherapy in HNSCC. B7-H3 expression is enhanced in HNSCC compared to normal sample and is stably expressed in HNSCC cell line. Besides, high B7-H3 expression is correlated with a dismal prognosis and resistance to immunotherapy and contributes to an immunosuppressive microenvironment. Moreover, single-cell RNA sequencing (scRNA-seq) analysis shows that B7-H3 is mainly expressed in the stromal as well as malignant cells. In conclusion, the study provides insight in understanding the prognostic value of B7-H3 in HNSCC and highlights its involvement in promoting the immunosuppressive microenvironment, which presents an attractive strategy for antibody-based immunotherapy.

Concomitant inhibition of B7-H3 and PD-L1 expression by a novel and synthetic microRNA delivers potent antitumor activities in colorectal tumor models

The families of miR-34 and miR-449 share the same seed region. However, the members showed differential effects on the expression of B7-H3 and PD-L1 in HCT-116 cells. Using miR-34a as a template, the non-seed region was modified by nucleotide alteration, yielding four synthetic microRNA (miRNA) analogs. Among those, NS-MX3, with a base alteration from G to C at the 18th locus of miR-34a, showed the most potent inhibition on both B7-H3 and PD-L1 expression. Subsequent investigations demonstrated that NS-MX3 had a broad anti-proliferation activity against several colorectal tumor cell lines and its antitumor effect was consistently reflected by tumor growth inhibition (TGI) in the HCT-116 xenograft model. In addition, NS-MX3 displayed a synergistic effect on TGI when combined with bevacizumab or regorafenib. Further analysis revealed that the superior antitumor activity of NS-MX3 was correlated to concomitant suppression of both B7-H3 and PD-L1 expression in tumor tissues. Taken together, the present study indicates that the non-seed region of miRNAs plays an important role in the regulation of checkpoint genes, thus showcasing single nucleotide alteration of the non-seed region as a promising approach to discover and develop novel immunotherapies.

Integrated analysis reveals distinct molecular, clinical, and immunological features of B7-H3 in acute myeloid leukemia

The role of B7‐H3 in acute myeloid leukemia (AML) is not fully understood. Two previous studies investigating its expression and significances in AML are partially different. In this study, we aimed to systematically characterize the genomic and immune landscape in AML patients with altered B7‐H3 expression using multi‐omics data in the public domain. We found significantly increased B7‐H3 expression in AML compared to either other hematological malignancies or healthy controls. Clinically, high B7‐H3 expression was associated with old age, TP53 mutations, wild‐type WT1 and CEBPA, and the M3 and M5 FAB subtypes. Moreover, we observed that increased B7‐H3 expression correlated significantly with a poor outcome of AML patients in four independent datasets. Gene set enrichment analysis (GSEA) revealed the enrichment of the “EMT” oncogenic gene signatures in high B7‐H3 expressers. Further investigation suggested that B7‐H3 was more likely to be associated with immune‐suppressive cells (macrophages, neutrophils, dendritic cells, and Th17 cells). B7‐H3 was also positively associated with a number of checkpoint genes, such as VISTA (B7‐H5), CD80 (B7‐1), CD86 (B7‐2), and CD70. In summary, we uncovered distinct genomic and immunologic features associated with B7‐H3 expression in AML. This may lead to a better understanding of the molecular mechanisms underlying B7‐H3 dysregulation in AML and to the development of novel therapeutic strategies.

Association analysis of B7-H3 and B7-H4 gene single nucleotide polymorphisms in susceptibility to ankylosing spondylitis in eastern Chinese Han population

This study was conducted to describe the association between the genetic variation of the recently identified immune checkpoint molecules B7-H3 and B7-H4, and the susceptibility to ankylosing spondylitis (AS). Two single nucleotide polymorphisms (SNPs) of B7-H3 gene and three SNPs of B7-H4 gene were genotyped in 649 AS patients and 646 age- and sex-matched healthy controls. Allele, genotype frequencies and different inheritance models were performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs), and the demographic and clinical parameters of patients were recorded. Our data indicated that B7-H4 rs10801935 and rs3738414 polymorphisms were correlated with AS susceptibility. In the stratification analyses, the minor A allele and GA genotype of B7-H4 rs3738414 increased the risk of AS in male patients (OR = 1.244, 95%CI = 1.026-1.508; OR = 1.453, 95%CI = 1.120-1.886, respectively). However, the association did not reach statistical significance after Bonferroni correction. Furthermore, haplotype analysis revealed that B7-H4 haplotype block TAG was a risk factor for the onset of AS (OR = 1.190, 95%CI = 1.020-1.389). These findings suggested that B7-H4 gene polymorphism may contribute to AS susceptibility in eastern Chinese Han population.

Surfaceome Profiling of Rhabdomyosarcoma Reveals B7-H3 as a Mediator of Immune Evasion

Novel therapeutic strategies are needed for the treatment of rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in children. By using a combination of cell surface proteomics and transcriptomic profiling of RMS and normal muscle, we generated a catalog of targetable cell surface proteins enriched in RMS tumors. Among the top candidates, we identified B7-H3 as the major immunoregulatory molecule expressed by RMS tumors. By using a large cohort of tissue specimens, we demonstrated that B7-H3 is expressed in a majority of RMS tumors while not detected in normal human tissues. Through a deconvolution analysis of the RMS tumor RNA-seq data, we showed that B7-H3-rich tumors are enriched in macrophages M1, NK cells, and depleted in CD8⁺-T cells. Furthermore, in vitro functional assays showed that B7-H3 knockout in RMS tumor cells increases T-cell mediated cytotoxicity. Altogether, our study uncovers new potential targets for the treatment of RMS and provides the first biological insights into the role of B7-H3 in RMS biology, paving the way for the development of next-generation immunotherapies.

MicroRNA miR-29a Inhibits Colon Cancer Progression by Downregulating B7-H3 Expression: Potential Molecular Targets for Colon Cancer Therapy

MiR-29a belongs to one of the subtypes of miRNAs known as non-coding single-stranded RNAs and is preferentially expressed in normal tissues. B7-H3, a member of the B7/CD28 immunoglobulin superfamily, was shown to be overexpressed in several solid malignant tumors, including colon cancer. In addition, it is associated with tumor progression and poor prognosis. We used immunohistochemical and Western blotting to assess B7-H3 protein expression levels in colon cancer and adjacent normal tissues and then compared their relationships with clinicopathological factors. Quantitative real-time reverse-transcription PCR was used to assess B7-H3 and miRNA-29a mRNA expression levels, and then their relationship and clinical significance were evaluated. In addition, colon cancer Caco-2 cells, which constitutively overexpress B7-H3, were transfected with lentivirus particles for miR-29a upregulation. Invasion and migration assays were carried out in vitro along with the establishment of a subcutaneous xenograft model in vivo to determine the role of miRNA-29a in colon cancer progression. The B7-H3 protein showed elevated expression in colon carcinoma and was relevant to TNM staging, lymph node metastasis, and reduced survival. Meanwhile, miR-29a was preferentially expressed in normal colon tissues, while B7-H3 transcript levels had no marked differences between tumor and normal tissue specimens. In vitro, miR-29a upregulation resulted in reduced B7-H3 expression. Furthermore, miR-29a upregulation reduced the invasive and migratory abilities of colon carcinoma cells. In animal models, upregulation of miR-29a slowed down the growth of subcutaneous xenotransplanted tumors and resulted in prolonged survival time. MiR-29a downregulates B7-H3 expression and accordingly inhibits colon cancer progression, invasion, and migration, indicating miR-29a and B7-H3 might represent novel molecular targets for advanced immunotherapy in colon cancer.

Fibronectin enhances tumor metastasis through B7-H3 in clear cell renal cell carcinoma

B7 homolog 3 (B7‐H3) plays an important role in tumor biology, but the molecular mechanism underlying the role of B7‐H3 in tumor metastasis remains unclear. In this article, our analysis of The Cancer Genome Atlas database suggested that B7‐H3 expression is associated with poor prognosis of patients with clear cell renal cell carcinoma (ccRCC). B7‐H3 knockdown affected the expression of metastasis‐related genes and significantly suppressed the metastasis of ccRCC cells, but it had no significant effect on the proliferation of ccRCC cells. Database analysis revealed a strong positive correlation between B7‐H3 and fibronectin (FN) in ccRCC cells, and further study also confirmed that FN interacts with B7‐H3. Silencing FN expression inhibited the migration and invasion of ccRCC cells, whereas exogenous FN promoted the migration and invasion of ccRCC cells, which was accompanied by activation of kinases [namely, phosphorylated (p)‐phosphoinositide 3‐kinase, p‐protein kinase B, p‐p38 and p‐extracellular regulated protein kinase]. B7‐H3 knockdown abolished the prometastatic effect of FN. In conclusion, our data suggest that B7‐H3 binds to exogenous FN and promotes the metastasis of ccRCC cells.

SCLC-J1, a novel small cell lung cancer cell line

Small cell lung cancer (SCLC) is a type of high-grade neuroendocrine carcinoma. It initially responds to chemotherapy but rapidly becomes chemoresistant and it is highly proliferative. The prognosis in SCLC is poor. We have established a novel SCLC cell line, SCLC-J1, from a malignant pleural effusion in a patient with advanced SCLC. SCLC-J1 cells express ganglioside GD2, CD276, and Delta-like protein 3. RB1 is lost.

These features of the new SCLC cell line may be useful in understanding the cellular and molecular biology of SCLC and in designing better treatment.

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A novel small lung cancer cell line, SCLC-J1, was successfully established.

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SCLC-J1 cells express the tumor-specific antigens ganglioside GD2, CD276, and Delta-like protein 3. RB1 is lost.

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SCLC-J1 will provide insights into SCLC biology that may permit better therapeutic targeting.

Mifepristone inhibited the expression of B7-H2, B7-H3, B7-H4 and PD-L2 in adenomyosis

BACKGROUND

The immune mechanism was shown to be involved in the development of adenomyosis. The aim of the current study was to evaluate the expression of the immune checkpoints B7-H2, B7-H3, B7-H4 and PD-L2 in adenomyosis and to explore the effect of mifepristone on the expression of these immune checkpoints.

METHODS

The expression of B7-H2, B7-H3, B7-H4 and PD-L2 in normal endometria and adenomyosis patient samples treated with or without mifepristone was determined by immunohistochemistry analysis.

RESULTS

In adenomyosis patient samples, the expression of B7-H2, B7-H3 and B7-H4 was increased in the eutopic and ectopic endometria compared with normal endometria, both in the proliferative and secretory phases. Moreover, the expression of B7-H2 and B7-H3 was higher in adenomyotic lesions than in the corresponding eutopic endometria, both in the proliferative and secretory phases. The expression of PD-L2 was higher in adenomyotic lesions than in normal endometria in both the proliferative and secretory phases. In the secretory phase but not the proliferative phase, the expression of B7-H4 and PD-L2 in adenomyotic lesions was significantly higher than that in the corresponding eutopic endometria. In normal endometria and eutopic endometria, the expression of B7-H4 was elevated in the proliferative phase compared with that in the secretory phase, while in the ectopic endometria, B7-H4 expression was decreased in the proliferative phase compared with the secretory phase. In addition, the expression of B7-H2, B7-H3, B7-H4 and PD-L2 was significantly decreased in adenomyosis tissues after treatment with mifepristone.

CONCLUSIONS

The expression of the immune checkpoint proteins B7-H2, B7-H3, B7-H4 and PD-L2 is upregulated in adenomyosis tissues and is downregulated with mifepristone treatment. The data suggest that B7 immunomodulatory molecules are involved in the pathophysiology of adenomyosis.

LncRNATUG1 Facilitates Th2 Cell Differentiation by Targeting the miR-29c/B7-H3 Axis on Macrophages

The role of long non-coding RNAs (lncRNA) in asthma remains unclear. In this study, we examined the role of long non-coding RNA taurine upregulated 1 (lncRNA TUG1) in asthma. We found that lncRNA TUG1 is one of the differentially expressed lncRNAs in the monocytes of asthmatic children and is associated with Th cell differentiation. LncRNA TUG1 and miR-29c are mainly distributed in the cytoplasm of macrophages. Our data suggested that lncRNA TUG1 increased in macrophages stimulated by House Dust Mite in a dose-dependent manner. Using loss- and gain of function strategy, we found that miR-29c might regulate Th2 cell differentiation by directly targeting co-stimulatory molecule B7-H3. Furthermore, down-regulation of lncRNA TUG1 decreased the level of GATA3 in CD4+T cells and was associated with miR-29c/B7-H3 axis. Moreover, the dual-luciferase reporter assay confirmed that lncRNA TUG1 serves as a competing endogenous RNA to sponge miR-29c. According to the rescue experiment, lncRNA TUG1 regulated Th2 cell differentiation via miR-29c. These data suggest that lncRNA TUG1 in macrophages regulates Th2 cell differentiation via miR-29c/B7-H3 axis.

A Novel Orthotopic Implantation Technique for Osteosarcoma Produces Spontaneous Metastases and Illustrates Dose-Dependent Efficacy of B7-H3-CAR T Cells

The outcome for metastatic pediatric osteosarcoma (OS) remains poor. Thus, there is an urgent need to develop novel therapies, and immunotherapy with CAR T cells has the potential to meet this challenge. However, there is a lack of preclinical models that mimic salient features of human disease including reliable development of metastatic disease post orthotopic OS cell injection. To overcome this roadblock, and also enable real-time imaging of metastatic disease, we took advantage of LM7 OS cells expressing firefly luciferase (LM7.ffLuc). LM7.ffLuc were implanted in a collagen mesh into the tibia of mice, and mice reliably developed orthotopic tumors and lung metastases as judged by bioluminescence imaging and histopathological analysis. Intratibial implantation also enabled surgical removal by lower leg amputation and monitoring for metastases development post-surgery. We then used this model to evaluate the antitumor activity of CAR T cells targeting B7-H3, an antigen that is expressed in a broad range of solid tumors including OS. B7-H3-CAR T cells had potent antitumor activity in a dose-dependent manner and inhibited the development of pulmonary metastases resulting in a significant survival advantage. In contrast T cells expressing an inactive B7-H3-CAR had no antitumor activity. Using unmodified LM7 cells also enabled us to demonstrate that B7-H3-CAR T cells traffic to orthotopic tumor sites. Hence, we have developed an orthotopic, spontaneously metastasizing OS model. This model may improve our ability not only to predict the safety and efficacy of current and next generation CAR T cell therapies but also other treatment modalities for metastatic OS.

Cell-surface antigen profiling of pediatric brain tumors: B7-H3 is consistently expressed and can be targeted via local or systemic CAR T-cell delivery

BACKGROUND

Immunotherapy with chimeric antigen receptor (CAR) T cells is actively being explored for pediatric brain tumors in preclinical models and early phase clinical studies. At present, it is unclear which CAR target antigens are consistently expressed across different pediatric brain tumor types. In addition, the extent of HLA class I expression is unknown, which is critical for tumor recognition by conventional αβTCR T cells.

METHODS

We profiled 49 low- and high-grade pediatric brain tumor patient-derived orthotopic xenografts (PDOX) by flow analysis for the expression of 5 CAR targets (B7-H3, GD2, IL-13Rα2, EphA2, and HER2), and HLA class I. In addition, we generated B7-H3-CAR T cells and evaluated their antitumor activity in vitro and in vivo.

RESULTS

We established an expression hierarchy for the analyzed antigens (B7-H3 = GD2 >> IL-13Rα2 > HER2 = EphA2) and demonstrated that antigen expression is heterogenous. All high-grade gliomas expressed HLA class I, but only 57.1% of other tumor subtypes had detectable expression. We then selected B7-H3 as a target for CAR T-cell therapy. B7-H3-CAR T cells recognized tumor cells in an antigen-dependent fashion. Local or systemic administration of B7-H3-CAR T cells induced tumor regression in PDOX and immunocompetent murine glioma models resulting in a significant survival advantage.

CONCLUSIONS

Our study highlights the importance of studying target antigen and HLA class I expression in PDOX samples for the future design of immunotherapies. In addition, our results support active preclinical and clinical exploration of B7-H3-targeted CAR T-cell therapies for a broad spectrum of pediatric brain tumors.

Multiplexed digital spatial profiling of invasive breast tumors from Black and White women

The NanoString GeoMx digital spatial profiling is a new multiplexed platform that quantifies the abundance of tumor‐ and immune‐related proteins in a spatially resolved manner. We performed DSP for the simultaneous assessment of 52 analytes within spatially resolved tissue compartments defined by pan‐cytokeratin expression. We compared protein targets between 94 African American/Black and 65 European American/White cases, tumor and stromal tissue compartments, estrogen receptor alpha (ER)‐positive and ER‐negative cases, and explored potential biomarkers of survival. Of 33 analytes with robust signal for analysis, results were highly replicable. For a subset of markers, correlative analyses between DSP analytes and traditional immunohistochemistry scores revealed moderate to very strong associations between the two platforms. Similarly, DSP analytes and gene expression scores were concordant for 21 of 25 markers with overlap between the two datasets. Several analytes varied by ER status, and across the 25 immune markers surveyed, 14 had a significant inverse association with ER expression. B7 homolog 3 (B7‐H3; encoded by CD276) was the only analyte to show a significant difference by race, being lower in both the tumor and stromal compartments in Black women. DSP markers that were associated with survival included CD8, CD25, CD56, CD127, EpCAM, ER, Ki‐67, and STING. We conclude that DSP is an efficient tool for screening tumor‐ and immune‐related markers in a simultaneous fashion and yields results that are concordant with established immune profiling assays. DSP immune analytes were inversely associated with ER expression, in agreement with a substantial body of previous work that documents higher immune infiltration in ER‐negative breast cancers. This technology revealed that scores of the B7‐H3 protein were significantly lower in breast cancers from Black women compared with White women, an intriguing finding that requires replication in independent and racially diverse female populations.

Advances in immunotherapeutic targets for childhood cancers: A focus on glypican-2 and B7-H3

Cancer immunotherapies have revolutionized how we can treat adult malignancies and are being translated to pediatric oncology. Chimeric antigen receptor T-cell therapy and bispecific antibodies targeting CD19 have shown success for the treatment of pediatric patients with B-cell acute lymphoblastic leukemia. Anti-GD2 monoclonal antibody has demonstrated efficacy in neuroblastoma. In this review, we summarize the immunotherapeutic agents that have been approved for treating childhood cancers and provide an updated review of molecules expressed by pediatric cancers that are under study or are emerging candidates for future immunotherapies. Advances in our knowledge of tumor immunology and in genome profiling of cancers has led to the identification of new tumor-specific/associated antigens. While cell surface antigens are normally targeted in a major histocompatibility complex (MHC)-independent manner using antibody-based therapies, intracellular antigens are normally targeted with MHC-dependent T cell therapies. Glypican 2 (GPC2) and B7-H3 (CD276) are two cell surface antigens that are expressed by a variety of pediatric tumors such as neuroblastoma and potentially can have a positive impact on the treatment of pediatric cancers in the clinic.

Clinical Insights Into Novel Immune Checkpoint Inhibitors

The success of immune checkpoint inhibitors (ICIs), notably anti-cytotoxic T lymphocyte associated antigen-4 (CTLA-4) as well as inhibitors of CTLA-4, programmed death 1 (PD-1), and programmed death ligand-1 (PD-L1), has revolutionized treatment options for solid tumors. However, the lack of response to treatment, in terms of de novo or acquired resistance, and immune related adverse events (IRAE) remain as hurdles. One mechanisms to overcome the limitations of ICIs is to target other immune checkpoints associated with tumor microenvironment. Immune checkpoints such as lymphocyte activation gene-3 (LAG-3), T cell immunoglobulin and ITIM domain (TIGIT), T cell immunoglobulin and mucin-domain containing-3 (TIM-3), V-domain immunoglobulin suppressor of T cell activation (VISTA), B7 homolog 3 protein (B7-H3), inducible T cell costimulatory (ICOS), and B and T lymphocyte attenuator (BTLA) are feasible and promising options for treating solid tumors, and clinical trials are currently under active investigation. This review aims to summarize the clinical aspects of the immune checkpoints and introduce novel agents targeting these checkpoints.

B7-H3 on breast cancer cell MCF7 inhibits IFN-γ release from tumour-infiltrating T cells

B7-H3 is a type I membrane protein that has contradictory co-stimulatory and co-inhibitory effects in adaptive and anti-tumour immunity. B7-H3 is up-regulated in many malignant tumours, including breast cancer. Therefore, we hypothesise that B7-H3, which has an immunosuppressive role, suppresses anti-tumour immunity. The aim of this study was to clarify the role of B7-H3 in the tumor microenvironment in breast cancer, explore the possibility of B7-H3 as a target for clinical immunotherapy, and provide reference for clinical work. We knocked down B7-H3 with siRNA in MCF7 breast cancer cells, which we termed MCF7-B7-H3-KD cells, and the expression of B7-H3 was assessed by flow cytometry. GAPDH (glyceraldehyde-3-phosphate dehydrogenase) knockdown was used as a control (MCF7-Gapdh). MCF7-B7-H3-KD and MCF7-Gapdh cells were co-cultured with peripheral blood mononuclear cells (PBMCs) and CD3⁺ T cells from healthy donors to assess the effect of B7-H3 loss. PBMCs cultured with MCF7-Gapdh cells showed decreased activation, proliferation, and function of CD8⁺ T cells, but there was no effect on the proliferation of CD4⁺ T cells. However, when MCF7-B7-H3-KD cells were co-cultured with PBMCs, the proliferation ability of CD4⁺ T cells and CD8⁺ T cells was significantly higher than that observed in MCF7-Gapdh cell co-culture. Additionally, co-culture with MCF7-Gapdh cells decreased the expression of IFN-γ (Interferon-γ). However, after co-culture with MCF7-B7-H3-KD cells, there was an increase in IFN-γ. We further found that this inhibitory effect on IFN-γ was because of decreased mTOR (the mammalian target of rapamycin) phosphorylation in T cells. Treatment of T cells co-cultured with MCF7-B7-H3-KD cells with an mTOR inhibitor blocked the secretion of IFN-γ. B7-H3 on tumour cells inhibits the proliferation of CD4⁺ and CD8⁺ T cells and inhibits the release of IFN-γ by decreasing mTOR signalling. A better understanding of these complex immune regulatory mechanisms should facilitate the generation of more powerful and selective tools to manipulate cancer therapy.

B7-H3 targeted antibody-based immunotherapy of malignant diseases

Introduction: Recent advances in immuno-oncology and bioengineering have rekindled the interest in monoclonal antibody (mAb)-based immunotherapies for malignancies. Crucial for their success is the identification of tumor antigens (TAs) that can serve as targets. B7-H3, a member of the B7 ligand family, represents such a TA. Although its exact functions and receptor(s) remain unclear, B7-H3 has predominantly a pro-tumorigenic effect mainly by suppressing the anti-tumor functions of T-cells.Areas covered: Initially we present a historical perspective on TA-specific antibodies for diagnosis and treatment of malignancies. Following a description of the TA requirements to be an attractive antibody-based immunotherapy target, we show that B7-H3 fulfills these criteria. We discuss its structure and functions. In a review and pooled analysis, we describe the limited B7-H3 expression in normal tissues and estimate B7-H3 expression frequency in tumors, tumor-associated vasculature and cancer initiating cells (CICs). Lastly, we discuss the association of B7-H3 expression in tumors with poor prognosis.Expert opinion: B7-H3 is an attractive target for mAb-based cancer immunotherapy. B7-H3-targeting strategies are expected to be highly effective and - importantly - safe. To fully exploit the diagnostic and therapeutic potential of B7-H3, its expression in pre-malignant lesions, serum, metastases, and CICs requires further investigation.

Expression, regulation and clinical significance of B7-H3 on neutrophils in human gastric cancer

Neutrophils are conspicuous components of gastric cancer (GC) tumors, increasing with tumor progression and poor patient survival. However, the phenotype, regulation and clinical relevance of neutrophils in human GC are presently unknown. Most intratumoral neutrophils showed an activated CD54⁺ phenotype and expressed high level B7-H3. Tumor tissue culture supernatants from GC patients induced the expression of CD54 and B7-H3 on neutrophils in time-dependent and dose-dependent manners. Locally enriched CD54⁺ neutrophils and B7-H3⁺ neutrophils positively correlated with increased granulocyte-macrophage colony stimulating factor (GM-CSF) detection ex vivo; and in vitro GM-CSF induced the expression of CD54 and B7-H3 on neutrophils in both time-dependent and dose-dependent manners. Furthermore, GC tumor-derived GM-CSF activated neutrophils and induced neutrophil B7-H3 expression via JAK-STAT3 signaling pathway activation. Finally, intratumoral B7-H3⁺ neutrophils increased with tumor progression and independently predicted reduced overall survival. Collectively, these results suggest B7-H3⁺ neutrophils to be potential biomarkers in GC.

In Vitro Evaluation of CD276-CAR NK-92 Functionality, Migration and Invasion Potential in the Presence of Immune Inhibitory Factors of the Tumor Microenvironment

BACKGROUND

Melanoma is the most lethal of all skin-related cancers with incidences continuously rising. Novel therapeutic approaches are urgently needed, especially for the treatment of metastasizing or therapy-resistant melanoma. CAR-modified immune cells have shown excellent results in treating hematological malignancies and might represent a new treatment strategy for refractory melanoma. However, solid tumors pose some obstacles for cellular immunotherapy, including the identification of tumor-specific target antigens, insufficient homing and infiltration of immune cells as well as immune cell dysfunction in the immunosuppressive tumor microenvironment (TME).

METHODS

In order to investigate whether CAR NK cell-based immunotherapy can overcome the obstacles posed by the TME in melanoma, we generated CAR NK-92 cells targeting CD276 (B7-H3) which is abundantly expressed in solid tumors, including melanoma, and tested their effectivity in vitro in the presence of low pH, hypoxia and other known factors of the TME influencing anti-tumor responses. Moreover, the CRISPR/Cas9-induced disruption of the inhibitory receptor NKG2A was assessed for its potential enhancement of NK-92-mediated anti-tumor activity.

RESULTS

CD276-CAR NK-92 cells induced specific cytolysis of melanoma cell lines while being able to overcome a variety of the immunosuppressive effects normally exerted by the TME. NKG2A knock-out did not further improve CAR NK-92 cell-mediated cytotoxicity.

CONCLUSIONS

The strong cytotoxic effect of a CD276-specific CAR in combination with an "off-the-shelf" NK-92 cell line not being impaired by some of the most prominent negative factors of the TME make CD276-CAR NK-92 cells a promising cellular product for the treatment of melanoma and beyond.

MiR-29c downregulates tumor-expressed B7-H3 to mediate the antitumor NK-cell functions in ovarian cancer

OBJECTIVE

B7-H3 is a member of the B7 family of immune checkpoint molecule. Although B7-H3 has been shown to regulate T cell-mediated peripheral immune response, whether it also correlated with NK cell exhaustion in ovarian cancer remains unclear. The purpose of this study was to explore the mechanism of B7-H3 regulating NK-cell proliferation and function.

MATERIAL AND METHODS

To investigate the relationship between B7-H3 expression and the NK-cell function in ovarian cancer, human ovarian tumor tissues and cell lines were first examined the protein and mRNA expression of B7-H3 by quantitative real-time PCR (qRT-PCR), Immunohistochemistry and Western-blot assays. Then we established B7-H3 knockout cell lines and measured the cytotoxicity of NK cells on these cells by LDH release assay and Flow Cytometry. In addition, we analyzed B7-H3 in the regulation of glycolysis and glycolysis-related proteins by Glycolysis Stress Test, Glucose Consumption Assay and Western-blot. Moreover, luciferase reporter assay was used to confirm the directly regulation of miR-29c to B7-H3. Finally, we carried out in vivo experiments.

RESULTS

We observed that tumor-expressed B7-H3 inhibits NK-cell function in vitro and in vivo, and is associated with glycolysis of ovarian cancer cell. Therapeutically, B7-H3 blockade prolonged the survival of SKOV3 tumor-bearing mice. In addition, miR-29c improved the anti-tumor efficacy of NK-cell by directly targeting B7-H3 in vitro were observed, but not in vivo.

CONCLUSION

Our results demonstrate that miR-29c downregulates B7-H3 to inhibit NK-cell exhaustion and associated with glycolysis, which suggest that NK cells may be a new target of anti-B7-H3 therapy in ovarian cancer patients.

The Expression of Three Negative Co-Stimulatory B7 Family Molecules in Small Cell Lung Cancer and Their Effect on Prognosis

Background

In recent years, immune checkpoint inhibitors have shown significant effects in a variety of solid tumors. However, due to the low incidence of small cell lung cancer (SCLC) and its unclear mechanism, immune checkpoints in SCLC have not been fully studied.

Methods

We evaluated the expression of PD-L1, B7-H3, and B7-H4 in 115 SCLC tissue specimens using immunohistochemistry. The clinical data of patients with SCLC were retrospectively reviewed to investigate three negative co-stimulatory B7 family molecules’ ability to affect the prognosis of SCLC.

Results

Among the SCLC patients with complete follow-up data (n = 107), sixty-nine (64.49%) expressed moderate to high B7-H3 levels, which correlated positively with tumor sizes (P < 0.001). Eighty (74.77%) patients expressed moderate to high B7-H4 levels, which correlated positively with metastases (P = 0.049). The positive expression of B7-H3 and B7-H4 correlated significantly with shortened overall survival (OS) (B7-H3, P = 0.006; B7-H4, P = 0.019). PD-L1 was positively expressed only in 13.08% of cancer tissues, and there was no significant correlation with prognosis. The Cox proportional hazards regression showed that B7-H3 was an independent prognostic indicator of OS (P = 0.028; HR = 2.125 [95% CI = 0.985-4.462]).

Conclusions

Our results suggest that B7-H3 has a negative predictive effect on SCLC. This outcome provides a theoretical basis for the subsequent research on immune checkpoint inhibitors targeting B7-H3.

Expression patterns of the immune checkpoint ligand CD276 in urothelial carcinoma

BACKGROUND

CD276 is an immune checkpoint molecule. Elevated CD276 expression by urothelial carcinoma is associated with poor prognosis, but little is known about its expression across different tumor stages. We therefore investigated CD276 expression in bladder cancer (BC) cells and in tissue samples of BC stages from pT2 to pT4.

METHODS

CD276 expression was explored in 4 urothelial cancer cell lines and 4 primary normal urothelial cell populations by quantitative RT-PCR, Western blot and flow cytometry. CD276 was investigated in bladder tumors from 98 patients by immunohistochemistry using a score (0-300) incorporating both, staining intensity and area of CD276 staining. Normal appearing urothelium in the bladder of the same patients served as controls.

RESULTS

The urothelial carcinoma cell lines expressed significantly higher levels of CD276 on transcript (p < 0.006), total protein levels (p < 0.005), and on the cell surface (p < 0.02) when compared to normal urothelial cells. In pT2-T4 tumor tissue samples, CD276 was overexpressed (median score 185) when compared to corresponding healthy tissues from the same patients (median score 50; p < 0.001). No significant differences in CD276 expression were recorded in late, locally advanced ≥ pT3a tumors (median score 185) versus organ-confined < pT3a tumors (median score 190), but it was significantly lower in the normal urothelial tissue associated with ≥ pT3a tumors (median score 40) versus < pT3a tumors (median score 80; p < 0.05).

CONCLUSION

CD276 expression is significantly elevated in urothelial carcinoma cells in all stages but varies between individuals considerably. Reduced CD276 expression in normal urothelial cells may imply that these cells would be protected from CD276-mediated immuno therapies.