B7-H3 is a new member of the B7 family. The receptor for B7-H3 has not been identified, but it seems to be expressed on activated T cells. Initial studies have shown that B7-H3 provides a stimulatory signal to T cells. However, recent studies suggest a negative regulatory role for B7-H3 in T cell responses. Thus, the immunological function of B7-H3 is controversial and unclear. In this study, we investigated the effects of neutralizing anti-B7-H3 mAb in a mouse model of allergic asthma to determine whether B7-H3 contributes to the development of pathogenic Th2 cells and pulmonary inflammation. Administration of anti-B7-H3 mAb significantly reduced airway hyperreactivity with a concomitant decrease in eosinophils in the lung as compared with control IgG-treated mice. Treatment with anti-B7-H3 mAb also resulted in decreased production of Th2 cytokines (IL-4, IL-5, and IL-13) in the draining lymph node cells. Although blockade of B7-H3 during the induction phase abrogated the development of asthmatic responses, B7-H3 blockade during the effector phase did not inhibit asthmatic responses. These results indicated an important role for B7-H3 in the development of pathogenic Th2 cells during the induction phase in a murine model of asthma.

Sublytic C5b-9 has been described as a pro-inflammatory mediator that triggers cell activation rather than inducing cell death. Dendritic cells (DC) play a critical role in controlling antigen-specific immune responses. Although DC maturation induced by various stimuli has been well characterized, the role of C5b-9 in DC function has not been described. In this report, we use in vitro assembled functional C5b-9 based on purified distal complement protein to show that DC maturation is promoted by sublytic C5b-9. This was demonstrated by up-regulation of CD83, HLA-antigens and costimulatory molecules, including CD80, D86, B7-H1, B7-H3, B7-H4 and BTLA. In addition, secretion of cytokines such as interleukin (IL)-12 and tumor necrosis factor-alpha was increased while the capacity for antigen uptake (FITC-Dextran and Lucifer Yellow) was reduced in C5b-9-treated DC. Mixed lymphocyte reactions indicated that C5b-9-activated DC acted as stimulators that significantly promoted CD4+ T cell activation and elicited production of cytokines, including interferon-gamma and IL-2. Interestingly, C5b-9-treated DC also orient CD4+ CD45RA+ naïve T cells toward Th1 polarization. Our results are the first to report that DC are potential immunoregulatory targets of C5b-9, suggesting that C5b-9 bridges innate and acquired immunity by inducing DC maturation.

As more patient data is cross-referenced with animal models of disease, the primary focus on T(h)1 autoreactive effector cell function in autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis, has shifted towards the role of T(h)17 autoreactive effector cells and the ability of regulatory T cells (T(reg)) to modulate the pro-inflammatory autoimmune response. Therefore, the currently favored hypothesis is that a delicate balance between T(h)1/17 effector cells and T(reg) cell function is critical in the regulation of inflammatory autoimmune disease. An intensive area of research with regard to the T(h)1/17:T(reg) cell balance is the utilization of blockade and/or ligation of various co-stimulatory or co-inhibitory molecules, respectively, during ongoing disease to skew the immune response toward a more tolerogenic/regulatory state. Currently, FDA-approved therapies for multiple sclerosis patients are all aimed at the suppression of immune cell function. The other favored method of treatment is a modulation or deletion of autoreactive immune cells via short-term blockade of activating co-stimulatory receptors via treatment with fusion proteins such as CTLA4-Ig and CTLA4-FasL. Based on the initial success of CTLA4-Ig, there are additional fusion proteins that are currently under development. Examples of the more recently identified B7/CD28 family members are PD-L1, PD-L2, inducible co-stimulatory molecule-ligand (ICOS-L), B7-H3, and B7-H4, all of which may emerge as potential fusion protein therapeutics, each with unique, yet often overlapping functions. The expression of both stimulatory and inhibitory B7 molecules seems to play an essential role in modulating immune cell function through a variety of mechanisms, which is supported by findings that suggest each B7 molecule has developed its own indispensable niche in the immune system. As more data are generated, the diagnostic and therapeutic potential of the above B7 family-member-derived fusion proteins becomes ever more apparent. Besides defining the biology of these B7/CD28 family members in vivo, additional difficulty in the development of these therapies lies in maintaining the normal immune functions of recognition and reaction to non-self-antigens following viral or bacterial infection in the patient. Further complicating the clinical translation of these therapies, the mechanism of action identified for a particular reagent may depend upon the method of immune-cell activation and the subset of immune cells targeted in the study.

Bladder cancer is one of most common malignant cancer. Although previous studies have found abnormal expression of B7-H3 in human bladder cancer tissues, the exact role and molecular mechanism of B7-H3 in bladder cancer remain unknown. In this study, we first detected the expression of B7-H3 in human bladder cancer samples and cell lines, and analyzed its correlations with clinicopathological pathological parameters. Next, siRNAs or overexpression plasmids of B7-H3 were transfected into T24 or 5637 cells, and cell proliferation, apoptosis, migration and invasion were analyzed via CCK-8, colony formation, flow cytometry and transwell assays, protein expression levels were determined by western blotting. The results presented here showed B7-H3 was upregulated in bladder cancer samples compared with normal tissues, and the expression level was correlated with local invasion status. B7-H3 did not affect cell proliferation and apoptosis, but cell migration and invasion were changed through the regulation of matrix metalloproteinase (MMP) 2/9. Knockdown of B7-H3 resulted in decreased activity of the STAT3 and PI3K/Akt pathways, and the Akt served as an upstream regulator of the STAT3. Our results suggest that the overexpression of B7-H3 promotes the migration and invasion of human bladder cancer cells through the PI3K/Akt/STAT3 signaling pathway.

Molecular alterations in malignant disease result in the expression or upregulations of various targets that can be used for imaging and treatment with radiopharmaceuticals. This theranostic principle has acquired greater importance in personalized medicine in recent years, particularly in oncology, where advanced tumors can be treated effectively with low side effects. Since the pioneering use of ¹³¹I in differentiated thyroid cancer in the 1940s, remarkable achievements in nuclear medicine endoradiotherapy have been demonstrated, mainly in the treatment of neuroendocrine neoplasms by using ¹⁷⁷Lu-labeled somatostatin analogs or in the treatment of advanced prostate cancer using prostate-specific membrane antigen-directed radionuclide therapy. Besides that, this review focuses on promising novel radiopharmaceuticals and describes their preclinical and clinical status. Radiolabeled antibodies, such as ¹³¹I-omburtamab directed against the B7-H3 protein on the surface of neuroblastoma cells; HuMab-5B1, a ⁸⁹Zr/¹⁷⁷Lu-labeled antibody for the treatment of CA19-9-expressing malignancies; and ¹⁷⁷Lu-lilotomab, a CD37 antibody for the treatment of B-cell lymphomas, are being highlighted. The neurotensin receptor ligand ¹¹¹In/¹⁷⁷Lu-3B-227 has demonstrated high potential in imaging and therapy for several malignancies (e.g., pancreatic adenocarcinomas). Targeting of the fibroblast activation protein is currently being explored for different tumor entities using PET imaging with the fibroblast activation protein inhibitor (FAPI) ⁶⁸Ga-FAPI-04, and the first therapeutic applications of ⁹⁰Y-FAPI-04 have been applied. After 2 decades of rapid development in theranostics, a variety of new targets are available for further clinical investigation.

CMTM6, a regulator of PD-L1 expression, also modulates tumor immunity. Little is known about the function of CMTM6 and its mechanism of action in head and neck squamous cell carcinoma (HNSCC). In this study, we found by immunohistochemistry (IHC) analysis that CMTM6 overexpression predicted a poor prognosis for HNSCC patients. We discovered that CMTM6 expression was correlated with increased activity through the Wnt/β-catenin signaling pathway, which is essential for tumorigenesis, maintenance of the cancer stem cells (CSCs), and the epithelial-to-mesenchymal transition (EMT) characteristic of multiple cancers. We used short hairpin RNA (shRNA) to eliminate expression of CMTM6, which led, in HNSCC cells, to reduced expression of nuclear β-catenin as well as inhibition of stem cell-like properties, TGF-β-induced EMT and cell proliferation. Consistent with these results, we identified a significant positive correlation between expression of CMTM6 and EMT- and CSC-related genes in The Cancer Genome Atlas (TCGA). We found positive correlations for both RNA and protein between expression of CMTM6 and immune checkpoint components. CMTM6 silencing-induced PD-L1 downregulation delayed SCC7 tumor growth and increased CD8+ and CD4+ T-cell infiltration. The proportions of PD-1+, TIM-3+, VISTA+, LAG-3+, and B7-H3+ exhausted T cells were decreased significantly in the CMTM6-knockdown group. CMTM6 thus regulates stemness, EMT, and T-cell dysfunction and may be a promising therapeutic target in the treatment of HNSCC.

The objective of this study was to analyze the clinical significance of cerebrospinal fluid (CSF) and plasma concentrations of B7-H3, tumor necrosis factor-alpha (TNF-alpha), gamma interferon (IFN-gamma), and interleukin-17 (IL-17) in bacterial and aseptic meningitis in children. The participants were six children with bacterial meningitis, 16 with aseptic meningitis, and 12 control subjects. All participants were between 2 months and 12 years of age on admission. Cytokines determination was performed by enzyme-linked immunosorbent assay technique. CSF and plasma-circulating B7-H3 were significantly higher in the bacterial meningitis group as compared with the aseptic group (p = 0.001) and the control group (p = 0.000 and p = 0.001 respectively). However, CSF and plasma-circulating B7-H3 in aseptic meningitis were not significantly higher than control group (p = 0.071 and p = 0.72 respectively).CSF and plasma-circulating TNF-alpha were significantly higher in the bacterial meningitis group as compared with the aseptic group (p = 0.004 and p < 0.0001 respectively) and control group (p = 0.004 and p < 0.0001 respectively). Similarly, we did not observe significant elevated TNF-alpha levels in CSF and plasma in aseptic group compared with control group (p = 0.03 and p = 0.12 respectively). IFN-gamma levels in CSF and plasma were undetectable in control group, and we did not find statistical significances in both of CSF and plasma between the elevated IFN-gamma level in bacterial meningitis group and aseptic meningitis group(p = 0.055 and p = 0.095 respectively) CSF and plasma levels of IL-17 were undetectable in all subjects. There were correlations between B7-H3 and TNF-alpha, IFN-gamma (r = 0.875, p = 0.000; r = -0.693, p = 0.000, respectively) in CSF in meningitis subjects. In plasma, levels of B7-H3 in bacterial meningitis on admission correlated positively with TNF-alpha (r = 0.968, p = 0.002), and white blood cell counts (r = 0.973, p = 0.001). Detectable CSF levels of B7-H3, TNF-alpha, and IFN-gamma on admission were not associated significantly with any of CSF characteristics. Additionally, CSF and plasma levels of B7-H3 decreased remarkably after treatment. Altogether, our data indicated that circulating B7-H3 and TNF-alpha levels in the CSF and plasma were useful markers for distinguishing bacterial from aseptic meningitis, and Circulating B7-H3 was demonstrated to be useful in evaluating the intensity of the infectious inflammatory process in the central nervous system in children.

Myeloid-derived suppressor cells (MDSC) potently inhibit antitumor immune responses, and thereby promoti tumor progression and metastasis. However, the nature of human tumor-infiltrating MDSC remains poorly characterized. Here, we find B7-H3 is exclusively expressed on a subset of intratumoral CD14+HLA-DR-/low MDSC but absent from adjacent normal lung tissues of patients with non-small cell lung carcinoma (NSCLC). Cytokine analysis revealed that B7-H3+CD14+HLA-DR-/low MDSC (B7-H3+MDSC) produced higher levels of IL-10 and TNFα but lower levels of IL-1β and IL-6 when compared with B7-H3-CD14+HLA-DR-/low myeloid-derived suppressor cells (B7-H3-MDSC). In a murine lung cancer model, B7-H3+MDSCs were found only in the tumor microenvironment and their frequencies increased during tumor progression. Clinical data analysis indicated that a higher frequency of B7-H3+MDSCs was associated with reduced recurrence-free survival in patients with NSCLC. Taken together, we identify a novel subset of MDSCs within the tumor microenvironment that fosters tumor progression.

Purpose: Breast cancer imaging methods lack diagnostic accuracy, in particular for patients with dense breast tissue, and improved techniques are critically needed. The purpose of this study was to evaluate antibody-indocyanine green (ICG) conjugates, which undergo dynamic absorption spectrum shifts after cellular endocytosis and degradation, and spectroscopic photoacoustic (sPA) imaging to differentiate normal breast tissue from breast cancer by imaging B7-H3, a novel breast cancer associated molecular target. Methods: Quantitative immunohistochemical staining of endothelial and epithelial B7-H3 expression was assessed in 279 human breast tissue samples, including normal (n=53), benign lesions (11 subtypes, n=129), and breast cancers (4 subtypes, n=97). After absorption spectra of intracellular and degraded B7-H3-ICG and Isotype control-ICG (Iso-ICG) were characterized, sPA imaging in a transgenic murine breast cancer model (FVB/N-Tg(MMTVPyMT)634Mul) was performed and compared to imaging of control conditions [B7-H3-ICG in tumor negative animals (n=60), Iso-ICG (n=30), blocking B7-H3+B7-H3-ICG (n=20), and free ICG (n=20)] and validated with ex vivo histological analysis. Results: Immunostaining showed differential B7-H3 expression on both the endothelium and tumor epithelium in human breast cancer with an area under the ROC curve of 0.93 to differentiate breast cancer vs non-cancer. Combined in vitro/in vivo imaging showed that sPA allowed specific B7-H3-ICG detection down to the 13 nM concentration and differentiation from Iso-ICG. sPA molecular imaging of B7-H3-ICG showed a 3.01-fold (P<0.01) increase in molecular B7-H3-ICG signal in tumors compared to control conditions. Conclusions: B7-H3 is a promising target for both vascular and epithelial sPA imaging of breast cancer. Leveraging antibody-ICG contrast agents and their dynamic optical absorption spectra allows for highly specific sPA imaging of breast cancer.

B7-H3, a recently identified B7 family member, has different isoforms in human and mouse. Mouse B7-H3 gene has only one isoform (2IgB7-H3) with two Ig-like domains, whereas human B7-H3 has two isoforms (2IgB7-H3 and 4IgB7-H3). In this study a systematic genomic survey across various species from teleost fishes to mammals revealed that 4IgB7-H3 isoform also appeared in pigs, guinea pigs, cows, dogs, African elephants, pandas, megabats and higher primate animals, which resulted from tandem exon duplication. Further sequence analysis indicated that this duplication generated a new conserved region in the first IgC domain, which might disable 4IgB7-H3 from releasing soluble form, while 2IgB7-H3 presented both membrane and soluble forms. Through three-dimensional (3D) structure modeling and fusion-protein binding assays, we discovered that the duplicated isoform had a different structure and might bind to another potential receptor on activated T cells. In T cell proliferation assay, human 2IgB7-H3 (h2IgB7-H3) and mouse B7-H3 (mB7-H3) both increased T cell proliferation and IL-2, IFN-γ production, whereas human 4IgB7-H3 (h4IgB7-H3) reduced cytokine production and T cell proliferation compared to control. Furthermore, both h2IgB7-H3 and mB7-H3 upregulated the function of lipopolysacharide (LPS)-activated monocyte in vitro. Taken together, our data implied that during the evolution of vertebrates, B7-H3 exon duplication contributed to the generation of a new 4IgB7-H3 isoform in many mammalian species, which have carried out distinct functions in the immune responses.

The recent impressive clinical responses to antibody-based immunotherapy have prompted the identification of clinically relevant tumor antigens that can serve as targets in solid tumors. Among them, B7-H3, a member of the B7 ligand family, represents an attractive target for antibody-based immunotherapy: it is overexpressed on differentiated malignant cells and cancer initiating cells, with limited heterogeneity, and high frequency (60% of 25,000 tumor samples) in many different cancer types, but has a limited expression at low level in normal tissues. In non-malignant tissues, B7-H3 has a predominantly inhibitory role in adaptive immunity, suppressing T-cell activation and proliferation. In malignant tissues, B7-H3 inhibits tumor antigen-specific immune responses, leading to a pro-tumorigenic effect. B7-H3 also has non-immunological pro-tumorigenic functions, such as promoting migration and invasion, angiogenesis, chemoresistance and endothelial-to-mesenchymal transition as well as affecting tumor cell metabolism. As a result, B7-H3 expression in tumors is associated with poor prognosis. Although experimental B7-H3 silencing reduces cancer cell malignant potential, there has been limited emphasis on the development of B7-H3 blocking antibodies, most likely because the B7-H3 receptor remains unknown. Instead, many antibody-based strategies utilizing distinct effector mechanisms to target B7-H3-expressing cancer cells have been developed. These strategies have demonstrated potent anti-tumor activity and acceptable safety profiles in preclinical models. Ongoing clinical trials are assessing their safety and efficacy in patients. Identification of the B7-H3 receptor will improve our understanding of its role in tumor immunity, and will suggest rational strategies to develop blocking antibodies which may enhance the therapeutic efficacy of tumor immunity.

B7-H3 (B7 homologue 3, CD276) is a member of the B7 immunoregulatory family and promotes tumor progression. The present study demonstrated that B7-H3 promotes gastric cancer cell migration and invasion. shRNA-mediated B7-H3 silencing in the N87 gastric cancer cell line suppressed cell migration and invasion in vitro and in vivo; downregulated metastasis-associated CXCR4; and inhibited AKT, ERK, and Jak2/Stat3 phosphorylation. B7-H3-silenced cells injected into the tail veins of 4-week-old female BALB/c nude mice produced fewer metastases than control cells, and resulted in longer survival times. Immunofluorescence analyses confirmed B7-H3/CXCR4 colocalization in N87 cells, and co-immunoprecipitation assays showed a direct interaction between the two proteins. Our analysis of 120 tissue samples from gastric cancer patients showed that increased B7-H3 expression correlated positively with both tumor infiltration depth and CXCR4 expression. These findings suggest that B7-H3 and CXCR4 may be novel targets for anti-gastric cancer therapeutics.

Purpose: Given that heterogeneous expression and variants of antigens on solid tumors are responsible for relapse after chimeric antigen receptor (CAR)-T cell therapy, we hypothesized that combinatorial targeting two tumor-associated antigens would lessen this problem and enhance the antitumor activity of T cells. Methods: The co-expression level of CD70 and B7-H3 was analyzed in multiple tumor tissue samples. Further, two putative antigens were identified in The Cancer Genome Atlas and Gene Expression Profiling Interactive Analysis database. Two CD70 targeted CARs with different antigen binding domain, truncated CD27 and CD70 specific single-chain antibody fragment (scFv), were designed to screen a more suitable target-antigen binding moiety. Accordingly, we designed a bivalent tandem CAR (TanCAR) and further assessed the anti-tumor efficacy of TanCAR-T cells in vitro and in vivo. Results: Our results indicated that co-expression of CD70 and B7-H3 was observed on multiple tumor types including kidney, breast, esophageal, liver, colon cancer, glioma as well as melanoma. The CD70 targeted CAR-T cells with binding moiety of CD70 specific scFv exhibit a higher affinity and antitumor effect against CD70⁺ tumor cells. TanCAR-T cells induced enhanced ability of cytolysis and cytokine release over unispecific CAR-T cells when encountering tumor cells expressing two target-antigens. Further, low doses of TanCAR-T cells could also effectively control the lung cancer and melanoma xenografts and improved overall survival of the treated animals. Conclusion: TanCAR-T cells targeting CD70 and B7-H3 exhibit enhanced antitumor functionality and improve the problem of antigenic heterogeneity and variant in the treatment against solid tumor and melanoma.

Keywords: B7-H3; CD70; Chimeric antigen receptor T cell; Immunotherapy; Solid tumor.

OBJECTIVE

This study focused on the expression pattern and clinical significance of B7-H3 expression in human acute leukemia.

METHODS

We systematically analyzed 134 patients with acute myeloid leukemia (101 cases) and acute lymphocytic leukemia (33 cases) by flow cytometry.

RESULTS

The frequency of B7-H3(+) cases was 44.8% in total. The B7-H3 expression rate differed from 0% to 74.8% in individual cases. The correlation between B7-H3 expression and traditional prognostic factors, such as age and gender, the white blood cell count was not confirmed. However, B7-H3 had a significant higher expression in CD34(+) cases and high risk karyotypes.

CONCLUSIONS

Owing to the expression of B7-H3 being statistically relevant in predicting disease progression and a shorter life survival, our results demonstrated that B7-H3 expression in acute leukemia predicts an unfavorable outcome.

B7-H3 is a cell surface molecule in the immunoglobulin superfamily that is frequently upregulated in response to autoantigens and pathogens during host T cell immune responses. However, B7-H3's role in the differential regulation of T cell subsets remains largely unknown. Therefore, we constructed a new B7-H3 deficient mouse strain (B7-H3 KO) and evaluated the functions of B7-H3 in the regulation of Th1, Th2, and Th17 subsets in experimental autoimmune encephalomyelitis (EAE), experimental asthma, and collagen-induced arthritis (CIA); these mouse models were used to predict human immune responses in multiple sclerosis, asthma, and rheumatoid arthritis, respectively. Here, we demonstrate that B7-H3 KO mice have significantly less inflammation, decreased pathogenesis, and limited disease progression in both EAE and CIA mouse models when compared with littermates; these results were accompanied by a decrease in IFN-γ and IL-17 production. In sharp contrast, B7-H3 KO mice developed severe ovalbumin (OVA)-induced asthma with characteristic infiltrations of eosinophils in the lung, increased IL-5 and IL-13 in lavage fluid, and elevated IgE anti-OVA antibodies in the blood. Our results suggest B7-H3 has a costimulatory function on Th1/Th17 but a coinhibitory function on Th2 responses. Our studies reveal that B7-H3 could affect different T cell subsets which have important implications for regulating pathogenesis and disease progression in human autoimmune disease.

Uveal melanoma (UM) is the most common primary intraocular cancer in adults. In the present study, we aimed to characterize the immunological features of primary UM cancer and to provide an association with prognostic markers and outcome. Also, we assessed the influence of the microenvironment on the expression of inhibitory immune checkpoints in UM. Genes of interest included MHC Class I and Class II molecules, as well as inhibitory immune-checkpoints, i.e. PDL1, PDL2, B7-H3, B7-H4, TBFRSF6B, CD47, CD155, GAL9, HVEM and CD200. We observed significant lower levels of MHC genes in UM cells as compared to normal uveal melanocytes. Unexpectedly however, the expression levels of most of the analyzed inhibitory immune-checkpoint genes were not different in cancer cells as compared to normal melanocytes, with the exception of CD200 and HVEM, that resulted significantly reduced. On the other hand, PDL1 inversely correlated with OS, PFS and thickness of the tumor. Also, PDL1, along with PDL2, expression significantly increased under inflammatory conditions. Finally, for the first time, we propose a possible role for CD47 in the immune evasive properties of UM. We show here that CD47 is significantly upregulated by UM cells following inflammatory stimuli and that it represents a good independent predictor of disease progression. The results from this study may propel advances in the development of immune-based therapies for UM patients.

BACKGROUND

B7-H3 exhibits altered expression in various cancers. However, the correlation between B7-H3 expression and prognosis of cancer patients remains controversial. Therefore, we elicit a meta-analysis to investigate the potential value of B7-H3 in the prognostic prediction in human cancers.

METHODS

We searched PubMed (last update by June 15th, 2016) to identify studies assessing the effect of B7-H3 on survival of cancer patients. Hazard ratios (HRs) for overall survival (OS), recurrence free survival (RFS) and progression-free survival (PFS) from individual studies were calculated and pooled by using a random-effect or fix-effect model, and heterogeneity and publication bias analyses were also performed.

RESULTS

Data from 24 observational studies consisting of 4141 patients were summarized. An elevated baseline B7-H3 was significantly correlated with poor OS (pooled HR = 2.09; 95% CI =1.60-2.74; P < 0.001). Differences across subgroups of tumor type (P = 0.324), year of publication (P = 0.431), ethnicity (P = 0.940), source of HR (P = 0.145), analysis type (P = 0.178) and sample size (P = 0.909) were not significant. Furthermore, high B7-H3 expression also predicted a significantly poor RFS (pooled HR = 1.39; 95% CI = 1.11-1.75; P = 0.004) but not PFS.

CONCLUSIONS

This meta-analysis clarifies that elevated B7-H3 expression is significantly associated with poor survival in cancer patients.

B7-H3 (CD276) belongs to the B7 family of immunoregulatory proteins and has been implicated in cancer progression and metastasis. In this study, we found that metastatic melanoma cells with knockdown expression of B7-H3 showed modest decrease in proliferation and glycolytic capacity and were more sensitive to dacarbazine (DTIC) chemotherapy and small-molecule inhibitors targeting MAP kinase (MAPK) and AKT/mTOR pathways: vemurafenib (PLX4032; BRAF inhibitor), binimetinib (MEK-162; MEK inhibitor), everolimus (RAD001; mTOR inhibitor), and triciribidine (API-2; AKT inhibitor). Similar effects were observed in melanoma cells in the presence of an inhibitory B7-H3 monoclonal antibody, while the opposite was seen in B7-H3-overexpressing cells. Further, combining B7-H3 inhibition with small-molecule inhibitors resulted in significantly increased antiproliferative effect in melanoma cells, as well as in BRAFV600E mutated cell lines derived from patient biopsies. Our findings indicate that targeting B7-H3 may be a novel alternative to improve current therapy of metastatic melanoma.

The aim of this study was to determine the expression of B7-H3, B7-H4, Foxp3 and IL-2 in cervical cancer tissues, and evaluate the corresponding clinical significance. The expression of B7-H3, B7-H4, Foxp3 and IL-2 in 108 cervical cancer specimens was detected using immunohistochemistry, and their relationship with clinicopathologic parameters was determined. B7-H3, B7-H4 and Foxp3 had high levels of expression in cervical cancer cells (72.22, 80.56, and 91.56%, respectively). B7-H3 levels were only significantly associated with tumor size (P=0.013), while B7-H4, Foxp3 and IL-2 levels were significantly associated with International Federation of Gynecology and Obstetrics (FIGO) stage (P=0.023, 0.014 and 0.036, respectively) and tumor size (P=0.045, 0.010 and 0.021, respectively). Their expression levels were not correlated with age, histologic type, differentiation and lymph node metastasis (all P>0.05). Cox regression multivariate analysis confirmed that B7-H3 or B7-H4 overexpression was an independent prognostic factor. In addition, there were significant positive relationships between the expression of B7-H3 and B7-H4 with Foxp3 (P<0.001). In contrast, the expression of B7-H3 and B7-H4 was negatively correlated with IL-2 (P<0.05). B7-H3, B7-H4 and Foxp3 may be useful biomarkers in patients with cervical cancer for predicting treatment.

Co-stimulatory molecule B7 homolog 3 protein (B7-H3) has been described as an important tumor antigen in various human tumors. The exact role of B7-H3 in tumor progression and its receptor are still ambiguous. The phenotype and the function of tumor-associated macrophages (TAMs) in human solid tumors are complicated and could contribute to the shaping of the tumor microenvironment. In the present study, B7-H3 expression and lymphocyte infiltration were investigated by immunohistochemistry in 117 colorectal carcinoma (CRC) patients. B7-H3 expression was positively associated with the infiltrating density of macrophage in CRC tissues, and B7-H3 expression and the infiltrating density of macrophages were negatively associated with the overall survival rate of patients. The putative B7-H3 receptor was found on activated monocytes and macrophages, indicating the direct function of B7-H3 signal on macrophages. Additional results revealed that during the differentiation of TAMs, B7-H3 promoted the polarization of type 2 macrophages (M2s) and switch of the M1 phenotype to the M2 phenotype. Thus, B7-H3 signaling promotes M2 differentiation via the putative receptor on monocytes and macrophages. Targeting the manipulation of TAMs through the B7-H3 pathway may be valuable for the development of novel immunotherapeutic strategies against human CRC.

B7-H3 (CD276), a member of the family of immune modulators, orchestrates antitumor immunity. To date, only small-sized studies have examined the association of B7-H3 expression with survival in pancreatic cancer, yielding inconclusive results. We evaluated tumor B7-H3 expression in 150 consecutive patients with pancreatic ductal adenocarcinoma using immunohistochemistry. B7-H3 expression was positive (≥10% tumor cells) in 99 of 150 (66%) cases of pancreatic cancer. We classified the tumors into four groups depending on B7-H3 expression (negative, low, intermediate, and high) and found that higher B7-H3 expression was independently associated with lower disease-free survival (DFS; for high vs. negative B7-H3 expression: multivariable hazard ratio (HR) = 3.12; 95% confidence interval (CI) = 1.48⁻6.15; Ptrend = 0.0026). Furthermore, the association of B7-H3 expression with survival differed according to the pathological stage (p-stage) (Pinteraction = 0.048, between p-stages I⁻II and III⁻IV). The association of B7-H3 positivity with lower DFS was stronger in tumors with p-stage I⁻II (multivariable HR = 3.10, 95% CI = 1.75⁻5.69; P < 0.0001) than in those with p-stage III⁻IV (multivariable HR = 1.20, 95% CI = 0.67⁻2.28; P = 0.55). We demonstrated that tumor high B7-H3 expression is independently associated with poor survival in patients with pancreatic cancer and that this association is stronger in tumors with p-stage I⁻II than in those with p-stage III⁻IV. B7-H3 expression may be a useful prognostic biomarker for identifying aggressive early-stage pancreatic cancer.

B7-H3 belongs to the co-inhibitory B7 family and plays an important role in the adaptive immune response in regulating T cells. In human malignancies, B7-H3 is reported to be involved in tumor immune evasion. However, the detailed molecular mechanism of B7-H3 in tumor evasion remains unclear, particularly in non-small cell lung cancer (NSCLC). Regulatory T cells (Tregs) are known as a key player in the inhibition of immune mechanisms. The study demonstrated the correlation between B7-H3 on tumor cells and the number of Tregs in the tumor microenvironment in NSCLC. B7-H3 was examined in tumor tissues from 110 patients with NSCLC by immunohistochemical analysis. Forkhead box P3+ (FOXP3+) Tregs in those spencimens were also detected and numbered. Survival curves were drawn using the Kaplan-Meier method and compared by the log-rank test. High B7-H3 expression in tumor cells significantly correlated with male gender, squamous NSCLC, advanced stage and shorter overall survival (OS) (P = 0.035, P = 0.004, P = 0.037, P = 0.014, respectively). Meanwhile, FOXP3 expression in tumor-infiltrating lymphocytes (TILs) was associated with male gender, regional lymph node involvement, advanced stage and worse OS (P = 0.009, P = 0.015, P = 0.014, P = 0.034, respectively). Significant correlation was identified between the expression of B7-H3 and the number of FOXP3+ TILs (P = 0.013). Patients with B7-H3 high/FOXP3 high had poorer OS (P = 0.006), suggesting that B7-H3 and Tregs may play a cooperatively role in tumor immune evasion, leading to poor outcomes for NSCLC patients.

CONCLUSIONS

B7-H3 is a B7-family co-stimulatory molecule and is broadly expressed on various tissues and immune cells. Transduction of B7-H3 into some tumours enhances anti-tumour responses. We have recently found that a triggering receptor expressed on myeloid cell-like transcript 2 (TLT-2) is a receptor for B7-H3. Here, we examined the roles of tumour-associated B7-H3 and the involvement of TLT-2 in anti-tumour immunity. Ovalbumin (OVA)(257-264)-specific OT-I CD8(+) T cells exhibited higher cytotoxicity against B7-H3-transduced OVA-expressing tumour cells (B7-H3/E.G7) in vitro and selectively eliminated B7-H3/E.G7 cells in vivo. The presence of B7-H3 on target cells efficiently augmented CD8(+) T-cell-mediated cytotoxicity against alloantigen or OVA, whereas the presence of B7-H3 in the priming phase did not affect the induced cytotoxicity. B7-H3 transduction into five tumour cell lines efficiently reduced their tumorigenicity and regressed growth. Treatment with either anti-B7-H3 or anti-TLT-2 monoclonal antibody accelerated growth of a tumour that expressed endogenous B7-H3, suggesting a co-stimulatory role of the B7-H3-TLT-2 pathway. The TLT-2 was preferentially expressed on CD8(+) T cells in regional lymph nodes, but was down-regulated in tumour-infiltrating CD8(+) T cells. Transduction of TLT-2 into OT-I CD8(+) T cells enhanced antigen-specific cytotoxicity against both parental and B7-H3-transduced tumour cells. Our results suggest that tumour-associated B7-H3 directly augments CD8(+) T-cell effector function, possibly by ligation of TLT-2 on tumour-infiltrating CD8(+) T cells at the local tumour site.

Targeting B7-H3 over-expressed tumor cells with anti-B7-H3 monoclonal antibodies inhibits tumor growth. Here we demonstrated the expression of B7 family homologue 3 (B7-H3) in a wide range of human tumor cells and further investigated whether B7-H3 could be served as a target for T-cell mediated immunotherapy against human cancers. The specific cytotoxic activity of activated T cell (ATC) armed with a novel anti-CD3 x anti-B7-H3 bispecific antibody (B7-H3Bi-Ab) against tumor cell was evaluated in vitro and in vivo. In contrast with unarmed ATC, an increase in cytotoxic activity of B7-H3Bi-armed ATC against tumor cells was observed at effector/target (E/T) ratios of 5:1, 10:1, and 20:1. Moreover, B7-H3Bi-armed ATC secreted more IFN-γ, TNF-α and IL-2 than unarmed ATC. Infusion of B7-H3Bi-armed ATC inhibited tumor growth in severe combined immunodeficiency (SCID) xenograft models, along with a significant survival benefit. Therefore, treatment with novel B7-H3Bi-armed ATC will be a promising strategy for current cancer immunotherapy.