Role Of B7-H3 Research Articles

B7H3 (CD276) regulation of myeloid cell differentiation in pulmonary fibrosis

Abstract Myeloid-derived suppressor cells (MDSCs) are induced in cancer and fibrosis, while absent in healthy tissues. The expansions of MDSC are correlated with disease severity and lung function deterioration in the latter. B7H3 induced in lung fibrosis causes the recruitment of MDSCs. However, the mechanism underlying the biogenesis of MDSCs is unclear. To study if B7H3-induced expansion of MDSCs is due to inhibition of the differentiation of myeloid progenitors, the role of B7H3 in the regulation of BM-derived myeloid cells was studied. The results showed that B7H3 deficiency in BM LysM+ myeloid cells significantly increased differentiation to mature myeloid cells. In contrast, treatment with B7H3 inhibited such differentiation. In mice, LysM+ cells-specific B7H3 deficiency induced mature myeloid cell differentiation, but significantly decreased immature MDSCs, which was associated with less immunosuppressive capability. Lack of B7H3 caused a significant reduction of MDSC marker genes characteristic. Furthermore, the delayed B7H3 antibody treatment or by ablating of its secretion from collagen-expressing cells reduced BM-derived MDSCs and PD1-expressing progenitors but increased mature myeloid cell number, which was accompanied by attenuated lung fibrosis. These findings suggested that activated fibroblasts in lung fibrosis may be a key source of soluble B7H3 essential for the signal to BM skewing myeloid lineage fate and induced biogenesis of MDSC

New Emerging Targets in Cancer Immunotherapy: The Role of B7-H3.

Immune checkpoints (ICs) are molecules implicated in the fine-tuning of immune response via co-inhibitory or co-stimulatory signals, and serve to secure minimized host damage. Targeting ICs with various therapeutic modalities, including checkpoint inhibitors/monoclonal antibodies (mAbs), antibody-drug conjugates (ADCs), and CAR-T cells has produced remarkable results, especially in immunogenic tumors, setting a paradigm shift in cancer therapeutics through the incorporation of these IC-targeted treatments. However, the large proportion of subjects who experience primary or secondary resistance to available IC-targeted options necessitates further advancements that render immunotherapy beneficial for a larger patient pool with longer duration of response. B7-H3 (B7 Homolog 3 Protein, CD276) is a member of the B7 family of IC proteins that exerts pleiotropic immunomodulatory effects both in physiologic and pathologic contexts. Mounting evidence has demonstrated an aberrant expression of B7-H3 in various solid malignancies, including tumors less sensitive to current immunotherapeutic options, and has associated its expression with advanced disease, worse patient survival and impaired response to IC-based regimens. Anti-B7-H3 agents, including novel mAbs, bispecific antibodies, ADCs, CAR-T cells, and radioimmunotherapy agents, have exhibited encouraging antitumor activity in preclinical models and have recently entered clinical testing for several cancer types. In the present review, we concisely present the functional implications of B7-H3 and discuss the latest evidence regarding its prognostic significance and therapeutic potential in solid malignancies, with emphasis on anti-B7-H3 modalities that are currently evaluated in clinical trial settings. Better understanding of B7-H3 intricate interactions in the tumor microenvironment will expand the oncological utility of anti-B7-H3 agents and further shape their role in cancer therapeutics.

The role of B7-H4 in ovarian cancer immunotherapy: current status, challenges, and perspectives.

Immunotherapy stands as a critical and auspicious therapeutic approach in the fight against cancer nowadays. Immune checkpoint inhibitors, in particular, have garnered widespread employment and delivered groundbreaking therapeutic outcomes across various malignancies. However, the efficacy is unsatisfactory in the ovarian cancer. The pressing concerns of the substantial non-response rate require immediate attention. The pursuit of novel targets and the formulation of synergistic combination therapy approaches are imperative for addressing this challenge. B7-H4, a member of the B7 family of co-inhibitory molecules, exhibits high expression levels in ovarian cancer, correlating closely with tumor progression, drug resistance, and unfavorable prognosis. B7-H4 has the potential to serve as a valuable biomarker for evaluating the immune response of patients. Recent investigations and preclinical trials focusing on B7-H4 in the context of ovarian cancer immunotherapy highlight its emergence as a promising immunotherapeutic target. This review aims to discuss these findings and anticipate the future prospects of leveraging B7-H4 in ovarian cancer immunotherapy and targeted therapy.

Abstract B040: Novel immunotherapy strategies targeting PTEN and TP53 defects in advanced prostate cancer

Abstract Prostate cancer is the most diagnosed cancer in men worldwide and the leading cause of cancer death in men worldwide. Genetic inactivation of PTEN and TP53 are common in advanced prostate cancers. Checkpoint immunotherapy has yielded meaningful responses across many cancers but shown modest activity in advanced prostate cancer. Prior studies showed that overexpression of immune checkpoint B7-H3 (CD276) correlates with the increased risks of clinical recurrence, disease spread, and poor outcomes in various cancer types, including prostate cancer. However, the roles of B7-H3 in prostate cancer development and its tumor microenvironment remain unclear, partially due to the lack of tissue-specific deletion mouse models. This gap in knowledge hinders the application of immunotherapy targeting B7-H3 in prostate cancers. To identify PTEN- and p53-associated immune checkpoints, we performed multi-omics analyses of expression patterns of 51 checkpoint molecules in human prostate cancer samples and found that B7-H3 is one of the most significantly overexpressed immune checkpoints in prostate tumors containing PTEN and TP53 genetic inactivation. Mechanistically, we found that the PTEN-AKT pathway co-operates with p53 pathway in modulating B7-H3 expression in cancer cells. In Pten/Trp53 genetically engineered mouse (GEM) models, prostate-specific deletion of Cd276 resulted in markedly delayed tumor progression and reversed immunosuppression in the tumor microenvironment. Furthermore, we developed and evaluated novel combinatorial immunotherapy strategies targeting B7-H3 in advanced prostate cancer with PTEN and TP53 deficiencies. Citation Format: Wei Shi, Yin Wang, Yuehui Zhao, Di Zhao. Novel immunotherapy strategies targeting PTEN and TP53 defects in advanced prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B040.

Immune checkpoint B7-H3 is a therapeutic vulnerability in prostate cancer harboring PTEN and TP53 deficiencies.

Checkpoint immunotherapy has yielded meaningful responses across many cancers but has shown modest efficacy in advanced prostate cancer. B7 homolog 3 protein (B7-H3/CD276) is an immune checkpoint molecule and has emerged as a promising therapeutic target. However, much remains to be understood regarding B7-H3's role in cancer progression, predictive biomarkers for B7-H3-targeted therapy, and combinatorial strategies. Our multi-omics analyses identified B7-H3 as one of the most abundant immune checkpoints in prostate tumors containing PTEN and TP53 genetic inactivation. Here, we sought in vivo genetic evidence for, and mechanistic understanding of, the role of B7-H3 in PTEN/TP53-deficient prostate cancer. We found that loss of PTEN and TP53 induced B7-H3 expression by activating transcriptional factor Sp1. Prostate-specific deletion of Cd276 resulted in delayed tumor progression and reversed the suppression of tumor-infiltrating T cells and NK cells in Pten/Trp53 genetically engineered mouse models. Furthermore, we tested the efficacy of the B7-H3 inhibitor in preclinical models of castration-resistant prostate cancer (CRPC). We demonstrated that enriched regulatory T cells and elevated programmed cell death ligand 1 (PD-L1) in myeloid cells hinder the therapeutic efficacy of B7-H3 inhibition in prostate tumors. Last, we showed that B7-H3 inhibition combined with blockade of PD-L1 or cytotoxic T lymphocyte-associated protein 4 (CTLA-4) achieved durable antitumor effects and had curative potential in a PTEN/TP53-deficient CRPC model. Given that B7-H3-targeted therapies have been evaluated in early clinical trials, our studies provide insights into the potential of biomarker-driven combinatorial immunotherapy targeting B7-H3 in prostate cancer, among other malignancies.

Molecular correlates of high B7-H3-expressing metastatic castrate-resistant prostate cancers (mCRPC) via exome, transcriptome, and epigenome analyses.

5045 Background: mCRPC is a lethal condition with limited effective treatment options. B7-H3, a transmembrane protein of the B7 checkpoint superfamily is overexpressed in prostate cancer (PC) and is associated with poor prognosis. While several novel approaches target B7-H3 in prostate cancer, lack of knowledge about the molecular features and regulatory mechanisms of B7-H3 expression in mCRPC prevents the optimal design of these interventions. We aimed to characterize B7-H3 in mCRPC with the purpose to reveal the roles of B7-H3 in mCRPC pathogenesis, and stratify the patient population optimal for B7-H3–targeted therapies. Methods: We conducted bioinformatic interrogations at genome-scale on whole-exome and whole-transcriptome sequencing (WES, WTS) data from SU2C/PCF (n = 209, mCRPC), SUWC (n = 101, mCRPC) and GTEx (n = 246, benign prostate tissue). We developed and utilized novel machine learning (ML) algorithms to examine the association of B7-H3 with other key PC pathways. We examined the genetic and epigenetic regulation of B7-H3 by CHIP-seq. We also performed single-cell mRNA sequencing (scRNA-seq) analysis on one patient before and after treatment with the AR inhibitor, enzalutamide. We utilized both Gene Set Enrichment Analysis (GSEA) and our ML approaches to identify enriched signaling pathways in high B7-H3–expressing mCRPC. Results: Expression of B7-H3 was significantly elevated in mCRPC compared to benign prostate tissues, and was distinctive from other B7 family members. High B7-H3 expression was significantly associated with ERG fusions, AR-V7 variant, and increased FOXA1 and androgen receptor (AR) mRNA expression. At gene-level analysis, our ML algorithm suggested that B7-H3 shared similar gene networks as AR and its co-regulators, HOXB13, and FOXA1. CHIP-seq analysis revealed that the distal enhancers of B7-H3 in mCRPC were hyperactive (based on enhanced H3K27Ac marks) relative to primary tumors. Notably, these B7-H3 enhancers were bound by HOXB13, FOXA1 and AR in mCRPC samples. Our scRNA-seq analysis of one patient resistant to enzalutamide showed increased number of B7-H3-expressing cells. Based on integrated GSEA and ML analyses on WTS data, B7-H3 was positively associated with TGF-beta signaling, an enzalutamide resistance pathway. Conclusions: In mCRPC, we found B7-H3 overexpression as compared to other B7 family members. The association of B7-H3-high expression and certain genomic alterations may stratify mCRPC patients for B7-H3–targeted therapy. Further, B7-H3 exhibited regulation by AR, HOXB13 and FOXA1, at the B7-H3 enhancers. The activating epigenetic modification at the distal enhancers represents another potential marker to examine B7-H3 expression in tumors. Altogether, our study indicates that B7-H3 is a critical target in mCRPC patients, including those resistant to enzalutamide.

B7-H4 reduction induced by Toxoplasma gondii infection results in dysfunction of decidual dendritic cells by regulating the JAK2/STAT3 pathway

BackgroundPrimary infection of Toxoplasma gondii can cause serious abnormal pregnancy outcomes such as miscarriage and stillbirth. Inhibitory molecule B7-H4 is abundantly expressed in dendritic cells (DCs) and plays an important role in maintaining immune tolerance. However, the role of B7-H4 in decidual DCs (dDCs) in T. gondii-induced abnormal pregnancy outcomes is not clear.MethodsWe established T. gondii-infected abnormal pregnancy model in wild-type (WT) and B7-H4 knockout (B7-H4−/−) pregnant mice in vivo and cultured primary human dDCs in vitro. The abnormal pregnancy outcomes were observed and the expression of B7-H4, functional molecules (CD80, CD86, and MHC-II or HLA-DR), indoleamine 2,3-dioxygenase (IDO), cytokines (IL-10 and IL-12), and signaling molecules JAK2/STAT3 in dDCs was detected by flow cytometry and Western blot.ResultsOur results showed that T. gondii infection significantly decreased B7-H4 expression in dDCs. In addition, B7-H4−/− infected pregnant mice showed much more severe abnormal pregnancy outcomes than their counterparts. Importantly, B7-H4−/− infection further regulated the expression of molecules (CD80, CD86, and MHC-II or HLA-DR), enzyme IDO, and cytokines (IL-10 and IL-12) in dDCs. We further discovered that B7-H4−/− infection impairs the JAK2/STAT3 pathway, contributing to dDC dysfunction.ConclusionsTaken together, the results show that reduction of B7-H4 by T. gondii infection significantly modulates the decrease in cytokine IL-10 and enzyme IDO and the increase in cytokine IL-12, contributing to dDC dysfunction. Moreover, the JAK2/STAT3 pathway is involved in the regulation of B7-H4 by T. gondii infection and in the subsequent IDO and cytokine production, which ultimately contributes to abnormal pregnancy outcomes.Graphical

Depletion of B7-H4 from C3H10 T1/2 Mesenchymal Stem Cells Attenuates their Immunomodulatory Therapy in Experimental Autoimmune Encephalomyelitis Mice.

Considering the controversial issue of whether MSC therapy is effective in the treatment of multiple sclerosis, it is important to seek more powerful data to clarify the effect of MSCs. B7-H4 is a unique costimulatory molecule that belongs to the B7 ligand family and is broadly expressed in both lymphoid and non-lymphoid tissues. Previous studies have shown that B7-H4 is involved in regulating the progression of autoimmune diseases. However, its role in MSCs and stem cell transplantation remains unclear. In this study, we focus on C3H10 T1/2 cells, which are mouse-derived mesenchymal stem cells. And we investigated the role of B7-H4 in C3H10 T1/2 cells and explored its underlying mechanisms. As a result, downregulation of B7-H4 induced apoptosis and impaired the cell proliferation of C3H10 T1/2 cells. Further results showed that cells were arrested in the G0/G1 phase after knockdown of B7-H4. Furthermore, an EAE model was induced in female C57BL/6 mice by injecting MOG 35-55, and we investigated the effect of C3H10 T1/2 cell transplantation for the EAE model after downregulation of B7-H4 in vivo. We found that C3H10 cells can migrate to the area of spinal cord lesions, and depletion of B7-H4 attenuated the immunoregulatory effect of C3H10 T1/2 cells in vivo. Together, our findings suggest that B7-H4 is important for C3H10 cells to exert neurorestoration and therefore may be a potential molecular target for stem cell transplant strategies.

A Novel Anti-B7-H3 × Anti-CD3 Bispecific Antibody with Potent Antitumor Activity.

B7-H3 plays an important role in tumor apoptosis, proliferation, adhesion, angiogenesis, invasion, migration, and evasion of immune surveillance. It is overexpressed in various human solid tumor tissues. In patients, B7-H3 overexpression correlates with advanced stages, poor clinical outcomes, and resistance to therapy. The roles of B7-H3 in tumor progression make it a potential candidate for targeted therapy. Here, we generated a mouse anti-human B7-H3 antibody and demonstrated its binding activity via Tongji University Suzhou Instituteprotein-based and cell-based assays. We then developed a novel format anti-B7-H3 × anti-CD3 bispecific antibody based on the antibody-binding fragment of the anti-B7-H3 antibody and single-chain variable fragment structure of anti-CD3 antibody (OKT3) and demonstrated that this bispecific antibody mediated potent cytotoxic activities against various B7-H3-positive tumor cell lines in vitro by improving T cell activation and proliferation. This bispecific antibody also demonstrated potent antitumor activity in humanized mice xenograft models. These results revealed that the novel anti-B7-H3 × anti-CD3 bispecific antibody has the potential to be employed in treatment of B7-H3-positive solid tumors.

The B7H4-PDL1 classifier stratifies immuno-phenotype in cervical cancer

BackgroundIt has been revealed that B7H4 is negatively correlated with PDL1 and identifies immuno-cold tumors in glioma. However, the application of the B7H4-PDL1 classifier in cancers has not been well testified.MethodsA pan-cancer analysis was conducted to evaluate the immunological role of B7H4 using the RNA-sequencing data downloaded from the Cancer Genome Atlas (TCGA). Immunohistochemistry (IHC) and multiplexed quantitative immunofluorescence (QIF) were performed to validate the primary results revealed by bioinformatics analysis.ResultsThe pan-cancer analysis revealed that B7H4 was negatively correlated with PDL1 expression and immune cell infiltration in CeCa. In addition, patients with high B7H4 exhibited the shortest overall survival (OS) and relapse-free survival (RFS) while those with high PDL1 exhibited a better prognosis. Multiplexed QIF showed that B7H4 was mutually exclusive with PDL1 expression and the B7H4-high group exhibited the lowest CD8 + T cell infiltration. Besides, B7H4-high predicted highly proliferative subtypes, which expressed the highest Ki67 antigen. Moreover, B7H4-high also indicated a lower response to multiple therapies.ConclusionsTotally, the B7H4-PDL1 classifier identifies the immunogenicity and predicts proliferative subtypes and limited therapeutic options in CeCa, which may be a convenient and feasible biomarker in clinical practice.

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

Simple SummaryRhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma in children, and there is a critical need to develop efficacious and tolerable anticancer therapies against this aggressive disease. To uncover druggable RMS-associated tumor antigens, we analyzed the cell surface protein repertoire in RMS tumor cells and normal tissue. We identified several surface proteins highly enriched in RMS, including the immune checkpoint molecule B7-H3. A further analysis using patient specimens showed that B7-H3 is overexpressed in most of RMS tumors and weakly or not detected in normal organs. Interestingly, we found that B7-H3 depletion was associated with higher immune cell killing activity against tumor cells. In line with this, high B7-H3 tumor expression was associated with lower CD8 T-cell density. Our study reveals novel RMS-associated proteins for the development of targeted therapies. In addition, we demonstrate that targeting B7-H3 function can pave the way for the design of new immunotherapies in the treatment of RMS.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.

B7-H3 augments the pro-angiogenic function of tumor-associated macrophages and acts as a novel adjuvant target for triple-negative breast cancer therapy

B7-H3 is an immune checkpoint molecule from the B7 superfamily. It has been widely studied in tumor immune evasion in certain types of cancer. In our preliminary study, we found that B7-H3 is specifically enriched in tumor-associated macrophages (TAMs) in triple-negative breast cancer (TNBC) patients and strongly correlated with poor clinical prognosis. However, the role of B7-H3 in breast cancer remains elusive. Our current study aims to explore the potential of B7-H3 as a novel target in TNBC therapy. Here, we demonstrated that B7-H3 enriched on TAMs is tightly correlated with TNBC clinical progression. B7-H3high TAMs exhibit great pro-metastatic and immunosuppressive functions by intriguing extracellular matrix (ECM) reconstruction and tumor angiogenesis, therefore helping tumor cell dissemination and dampening T-cell infiltration in tumor microenvironment (TME). Importantly, targeting blockade of B7-H3 by anti-B7-H3 antibody improves the tumor vasculature disorder, thereby enhancing chemotherapy and PD-1 therapy efficacy. In conclusion, our study establishes the correlation between B7-H3high TAMs and TNBC progression for the first time. By exploring the possibility of targeting B7-H3 expressed in both tumor cells and TAMs, we suggest that B7-H3 could be a promising target in clinical TNBC treatment.

Abstract A84: B7-H3 promotes antitumor T-cell suppression via MDSCs in colorectal cancer

Abstract One of the mechanisms causing resistance to checkpoint inhibitor treatment is accumulation of suppressive immune cells including myeloid-derived suppressor cells (MDSCs). In CRC patients, accumulation of MDSCs correlates with poor overall survival. Among a subset of CRC patients with high mutation burden, 31.1% respond to checkpoint inhibitor treatment. This implies that targeting resistance mechanisms such as MDSCs in these CRC patients could boost the efficacy of this treatment. B7-H3 (CD279), a member of the B7 family, is expressed on myeloid cells and suppresses T-cell proliferation. Therefore, we hypothesize that B7-H3 on MDSCs could promote CRC tumor growth by suppressing cytotoxic CD8 T cells. We used polyps from ApcMin/+ mice, an intestinal tumor model and a transplantable CRC tumor model such as MC38 colon carcinoma to assess the role of B7-H3. Our findings show that B7-H3 is upregulated in ApcMin/+ polyps and is expressed on in vitro derived monocytic MDSCs (M-MDSCs). The frequency of MDSCs increased with tumor growth, indicating the close correlation between MDSCs and disease burden. Blocking B7-H3 with an antibody in MC38 tumor model significantly reduced tumor volume (control group receiving isotype antibody: 1672.2 ± 121 mm3; B7-H3 antibody treated group: 892.7 ± 36.4 mm3; p<0.05). The frequency of CD4 and CD8 T cells in spleens and tumors of B7-H3 antibody-treated mice was increased, but this was not statistically significant. However, the frequency of CD8 cells producing IFNγ or granzyme B was significantly increased in tumors of B7-H3 antibody-treated mice. This shows that inhibition of B7-H3 in CRC regresses tumor growth and expands cytotoxic CD8 T cells in MC38 tumors. Previously we showed that reduction of intestinal tumors in ApcMin/+Stat6-/- mice correlated with reduced MDSCs and increased CD8 cytotoxic activity, indicating that MDSCs suppressed CD8 cells. Therefore, B7-H3 suppresses cytotoxic CD8 response in colon carcinoma, possibly by mediating the suppressive function of MDSCs. Clinical trials using dual targeting antibodies to B7-H3 and CD3 recruit T cells to kill tumor cells expressing B7-H3. However, impaired T-cell effector function by MDSCs could limit the efficacy of this therapy. Targeting B7-H3 on MDSCs could overcome resistance and boost the efficacy of combination treatments. Citation Format: Asha Jayakumar, Alfred Bothwell. B7-H3 promotes antitumor T-cell suppression via MDSCs in colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A84.

Overexpression of B7-H3 in α-SMA-Positive Fibroblasts Is Associated With Cancer Progression and Survival in Gastric Adenocarcinomas.

Background: B7-H3 promotes tumor immune escape and is highly expressed in tumor tissues. Stromal cells in tumors, including fibroblasts, play an important role in this process; however, the role of B7-H3 in tumor fibroblasts has not been fully clarified.Methods: We examined B7-H3, CD31, and alpha-smooth muscle actin (α-SMA) protein expression in 268 gastric adenocarcinomas (GACs) by immunohistochemistry. The coexpression of B7-H3 with CD31 or α-SMA was examined using immunofluorescence double staining. Cytokine expression from fibroblasts treated with B7-H3 small interfering RNA (siRNA) was analyzed by a Quantitative reverse transcription-polymerase chain reaction (qPCR) and Enzyme-linked immunosorbent assay (ELISA). The transwell tests were conducted to assess the migration and invasion ability of fibroblasts. The overall survival was analyzed by a Kaplan-Meier analysis. Associations between categorical variables were assessed using the Pearson's Chi-square test or Fisher's exact test.Results: GAC patients with B7-H3 expression showed significantly poorer survival (P = 0.012). The overall survival of the group with high B7-H3 expression was significantly worse than the group with low B7-H3 expression in both tumor cells and in stromal cells (P = 0.007 and P = 0.048, respectively). B7-H3 expression correlated with many clinicopathological data, including tumor stage, tumor depth, lymph node involvement, and survival. Immunofluorescence staining showed that B7-H3 was expressed in tumor cells and α-SMA-positive fibroblasts. Remarkably, high expression of α-SMA was associated with a poor prognosis (P = 0.007), and the prognoses of patients with high stromal expression of B7-H3 and α-SMA were significantly worse than that of other combination types (P = 0.001). Additionally, the absence of B7-H3 led to decreased secretion of cytokines, such as interleukin (IL)-6 and vascular endothelial growth factor (VEGF), as well as a decline in migration and invasion ability in cancer-associated fibroblasts (CAFs).Conclusions: Patients with high B7-H3 expression either in tumor cells or in stromal cells had significantly poorer overall survival. Stromal B7-H3 expression was mostly detected in α-SMA-positive CAFs. GAC patients with both stromal B7-H3-high and α-SMA-high expression had significantly poorer overall survival, suggesting that stromal B7-H3 and α-SMA expression status can serve as an indicator of poor prognosis for GAC patients.

B7-H3 promotes the cell cycle-mediated chemoresistance of colorectal cancer cells by regulating CDC25A.

Colorectal cancer (CRC) is one of the most common malignancies, and chemoresistance is one of the key obstacles in the clinical outcome. Here, we studied the function of B7-H3 in regulating cell cycle-mediated chemoresistance in CRC. The ability of B7-H3 in regulating chemoresistance was investigated via cell viability, clonogenicity, apoptosis and cycle analysis in vitro. Moreover, the role of B7-H3/CDC25A axis in regulating chemoresistance in vivo in the xenograft tumor models by intraperitoneal injection of oxaliplatin (L-OHP) and CDC25A inhibitors. The correlation between B7-H3 and CDC25A was examined in the CRC patients by immunohistochemistry (IHC) and pathological analyses. We found that B7-H3 could effectively enhance the resistance to a chemotherapeutic drug (oxaliplatin or 5-fluorouracil) via CDC25A. B7-H3 regulated the expression of CDC25A by the STAT3 signaling pathway in CRC cells. Furthermore, overexpression of B7-H3 enhanced chemoresistance by reducing the G2/M phase arrest in a CDC25A-dependent manner. Silencing CDC25A or treatment with CDC25A inhibitor could reverse the B7-H3-induced chemoresistance of cancer cells. Moreover, both B7-H3 and CDC25A were significantly upregulated in CRC samples compared with normal adjacent tissues and that the levels correlated with tumor stage. CDC25A was positively correlated with B7-H3 expression in this cohort. Taken together, our findings provide an alternative mechanism by which CRC cells can acquire chemoresistance via the B7-H3/CDC25A axis.

Role of B7H3/IL-33 Signaling in Pulmonary Fibrosis-induced Profibrogenic Alterations in Bone Marrow.

Rationale: The impact of lung insult on the bone marrow (BM) and subsequent disease is unknown.Objectives: To study alterations in the BM in response to lung injury/fibrosis and examine their impact on subsequent lung insult.Methods: BM cells from control or bleomycin-treated donor mice were transplanted into naive mice, which were subsequently evaluated for bleomycin-induced pulmonary fibrosis. In addition, the effect of prior bleomycin treatment on subsequent fibrosis was examined in wild-type and B7H3-knockout mice. Samples from patients with idiopathic pulmonary fibrosis were analyzed for potential clinical relevance of the findings.Measurements and Main Results: Recipient mice transplanted with BM from bleomycin-pretreated donors showed significant exacerbation of subsequent fibrosis with increased B7H3+ cell numbers and a T-helper cell type 2-skewed phenotype. Pretreatment with a minimally fibrogenic/nonfibrogenic dose of bleomycin also caused exacerbation, but not in B7H3-deficient mice. Exacerbation was not observed if the mice received naive BM cell transplant after the initial bleomycin pretreatment. Soluble B7H3 stimulated BM Ly6Chi monocytic cell expansion in vitro and caused similar expansion in the lung in vivo. Notably, soluble B7H3 was elevated in plasma of patients with idiopathic pulmonary fibrosis and in BAL fluid in those with acute exacerbation. Finally, ST2 deficiency diminished the bleomycin-induced B7H3 and IL-13 upregulation, suggesting a role for type 2 innate lymphoid cells.Conclusions: Pulmonary fibrosis caused significant alterations in BM with expansion and activation of monocytic cells, which enhanced fibrosis when transplanted to naive recipients with potential mediation by a novel role for B7H3 in the pathophysiology of pulmonary fibrosis in both mice and humans.

B7-H4 is highly expressed in aggressive Epstein-Barr virus positive diffuse large B-cell lymphoma and inhibits apoptosis through upregulating Erk1/2 and Akt signalling pathways

BackgroundB7-H4 is among the B7 family members which may serve as a new targetable immune checkpoint molecule. It was reported that high level of serum B7-H4 level may be correlated with lymphoma. Nevertheless, the role of B7-H4 in Epstein-Barr Virus-Positive diffuse large B cell lymphoma (EBV+DLBCL) has not been addressed although it has been suggested that B7-H4 could promote tumor growth and metastatic progression in certain cancers.MethodsBetween January 2005 and November 2017 at the department of Hematology, Shanghai Jiao Tong University School of Medicine affiliated Shanghai General Hospital 260 DLBCL samples were analyzed for EBV-encoded small RNA (EBV-EBER) by in situ hybridization. The expression level of B7-H4 in DLBCL tumor tissue was evaluated by immunohistochemistry. Furthermore, the role of B7-H4 in DLBCL was further investigated in DLBCL cell line.ResultsEBV+DLBCL patients suffered from markedly lower overall survival (OS) and progression-free survival (PFS) rates in our study. We showed that B7-H4 was significantly overexpressed in 16 EBV+-subgroup cases out of 260 DLBCL patients. We further found that EBV infection in lymphoblast cells led to enhanced expression of B7-H4 followed by increased cell viability and reduced apoptosis. In contrast, inhibition of B7-H4 simultaneously impaired cell viability and induced apoptosis. Mechanistically, inhibiting B7-H4 resulted in decreased phosphorylation Erk 1/2 and Akt.ConclusionOur study reveals a critical role of B7-H4 in EBV+DLBCL development by regulating cell survival and apoptosis through the Erk and Akt signalling pathways. Targetting B7-H4 may be promising in the therapy of EBV+DLBCL.

Abstract 2405: B7H4 as a T cell inhibitory regulator in bladder cancer

Abstract Despite a high number of neoantigens and T cell infiltration, most locally advanced and metastatic bladder cancers (BC) (>70%) do not respond to anti-PD1 treatment. Thus, targeting additional checkpoints may play an important role in treatment of BC. We sought to identify negative regulators of T cell activity and evaluate their function using a previously validated pre-clinical carcinogen-induced mouse model of BC. To identify regulators of T cell activity, we first investigated the timing and infiltration of T cells during tumor development in the BBN mouse BC model. We found that numbers of CD4+ and CD8+ T cell increased dramatically within the first 1-2 weeks, but then decreased over the next six weeks decreasing to the lowest levels at 8 weeks before increasing again coordinating with increasing tumor volume. During the decrease in T cell numbers, macrophages increased and by transcriptome profiling we identified increased levels of the T cell inhibitory protein B7-H4. B7-H4+CD11b+ macrophages increased over 4 weeks with opposite expression of CD4+ and CD8+ T cells by FACS. By IHC we localized B7-H4 expression in macrophages adjacent to tumor. A bioinformatic analysis of the human TCGA identified highest B7-H4 expression in luminal infiltrated subtypes of MIBCs, but did not correlate with CD4, CD8 or overall tumor mutation burden. MIBCs with elevated B7-H4 expression had significantly worse survival. In vitro, addition of anti-B7-H4 significantly increased proliferation and IFN-γ production by human T cells co-cultured with B7-H4 expressing APCs. To determine the role of B7-H4 in BC, we treated mice with overt BC (beginning at 4 months of carcinogen administration) with vehicle, anti-PD1 or anti-B7-H4 antibody. Compared to vehicle treated animals, anti-B7-H4 treated mice had a reduction in the number of pT3 tumors (50% vs. 73%), but less than anti-PD1 treated tumors (27%). However, anti-B7-H4 treated mice had significantly increased tumor infiltrating CD8+ T cells per histological field (77.1+34.3 vs. 11.5+7.8; p=0.0121), as well as a significant increase splenic CD8+IFN-γ+ T cells and levels of secreted IFN-γ upon anti-CD3 stimulation. Transcriptome profiling of tumors that responded to anti-B7-H4 antibody by RNA-Seq identified a decrease in mitotic cell cycle, cell cycle checkpoints, RHO GTPases and mitotic spindle checkpoint pathways in responsive tumors. In summary, we confirm the expression of B7-H4 in macrophages found in a murine model of BC and correlate expression to poor survival in the TCGA of MIBC. Inhibition of B7-H4 results in lymphocyte proliferation in vitro and inhibition of B7-H4 in mice resulted in decreased tumor stage and increased CD8+ TILs. This data suggests that B7-H4 may be a candidate alternative checkpoint that can be targeted in humans with BC unresponsive to PD1 therapy. Citation Format: Joshua Meeks, Alexander P. Glaser, Damiano Fantini, Yanni Yu, Valerie Eaton, Joseph R. Podojil, Stephen D. Miller. B7H4 as a T cell inhibitory regulator in bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2405.

B7-H3 and B7-H4 expression in phyllodes tumors of the breast detected by RNA in situ hybridization and immunohistochemistry: Association with clinicopathological features and T-cell infiltration.

Phyllodes tumors are rare biphasic breast tumors with the potential for both local recurrence and distant metastasis. The aberrant expression of B7-H3 and B7-H4 B7 molecules could be potential targets for future development of immunotherapeutic approaches. This work was undertaken to evaluate the expression of B7-H3 and B7-H4 in phyllodes tumors and assess the association with the grade and clinical behavior of phyllodes tumors. In addition, the roles of B7-H3 and B7-H4 in the regulation of tumor immune surveillance were evaluated by assessing the relationship between B7-H3/B7-H4 expression and T-cell infiltration. The messenger RNA and protein expression of B7-H3/B7-H4 were determined by RNAscope in situ hybridization and immunohistochemistry, respectively, in 101 phyllodes tumors (60 benign, 26 borderline, and 15 malignant) using a tissue microarray. Immunohistochemistry for CD3 and CD8 was also performed. B7-H3 messenger RNA and protein appeared to be concentrated mainly in the stromal compartment of phyllodes tumors. However, B7-H4 messenger RNA and protein were undetectable in the stromal compartment of phyllodes tumors. Stromal B7-H3 messenger RNA and protein expression were noted in 10 (16.7%) and 31 (51.7%) of 60 benign phyllodes tumors, 12 (46.1%) and 20 (76.9%) of 26 borderline phyllodes tumors, and 10 (66.7%) and 13 (86.7%) of 15 malignant phyllodes tumors, respectively. Stromal B7-H3 messenger RNA and protein expression increased as phyllodes tumors progressed from benign to borderline and finally to the malignant grade (Pearson's R = 0.411, p < 0.001 and Pearson's R = 0.293, p = 0.003, respectively). The recurrence rate was higher in the stromal B7-H3 messenger RNA or protein-positive group than in the negative group, but this difference was not significant. Stromal B7-H3 protein expression inversely correlated with the densities of CD3+ and CD8+ T-cell infiltrates ( p = 0.001 and p = 0.027, respectively). These results suggest that B7-H3 is involved in the progression of phyllodes tumors and may contribute to their immune surveillance.

B7H4 is associated with stemness and cancer progression in esophageal squamous cell carcinoma

B7H4 is overexpressed in human cancers and often correlates with poor clinical outcome. There is a lack of data on the role of B7H4 as a cancer stem cell (CSC) regulator in esophageal squamous cell carcinoma (ESCC) and its expression levels compared to other stemness genes in ESCC. In this study, we have assessed the expression of B7H4 and cancer stemness proteins in 156 paraffin-embedded ESCC tissue samples using immunohistochemistry as well as in ESCC cell lines using Western blotting and immunofluorescence imaging. The correlation of B7H4 expression with clinicopathological parameters, cell cycle regulating genes, and PI3K/Akt/NF-κB signaling genes was investigated. The expression of B7H4 in ESCC tissue was correlated with the primary tumor (pT) stage, stromal activity, and the expression of CD68 and HIF-1α. However, B7H4 expression was negatively associated with CD8+ T cell infiltration in ESCC tissues. Moreover, B7H4 was found to be strongly linked to prognostic factors leading to poor clinical outcome. B7H4-expressing cancer cells also expressed known cancer stemness proteins (Sox9, LSD1, Oct4, and LGR5). Moreover, B7H4, Sox9, LSD1, Oct4, and LGR5 were highly expressed in more poorly differentiated ESCC cell lines. Notably, B7H4 expression was positively associated with the expression of cell cycle regulators such as cyclin D1, p27, and PI3K/Akt/NFκB signaling proteins. B7H4 could be a novel cancer stem cell marker for the prognostic evaluation of ESCC patients as well as a potential therapeutic target against ESCC.