B7-H4 enhances oncogenicity and inhibits apoptosis in pancreatic cancer cells

B7-H4 is expressed in a variety of tumor cells and functions as a negative regulator of T cells. However, clarification is needed as to whether B7-H4 mediates tumorigenesis through mechanisms, such as apoptosis, in addition to mediating tumor immune escape. We investigate the mechanisms involved in enhanced oncogenicity and the inhibition of apoptosis by B7-H4 in pancreatic cancer cells. Short interfering RNAs (siRNAs) specific for B7-H4 were evaluated for their ability to knockdown B7-H4 mRNA and protein expression in pancreatic cancer cells and the most effective siRNA was selected for investigating the effect of B7-H4 gene silencing in a number of functional assays. The inhibition of B7-H4 increased cell-cell adhesion and decreased the formation of pseudopodia. It also increased the expression of E-cadherin and decreased the expression of vimentin and CD44. B7-H4 siRNA inhibited cell proliferation, colony formation and migration of pancreatic cancer cells. Moreover, increased apoptosis in pancreatic cancer cells following B7-H4 silencing was demonstrated in vitro by using flow cytometry and in a xenograft tumor model and was associated with increased caspase activity and decreased Erk1/2 phosphorylation both in vitro and in vivo. Loss of B7-H4 function thus prevents tumor growth through many processes, including the induction of apoptosis and inhibition of the Erk1/2 signaling pathway indicating that B7-H4 is a cancer promoter and a potentially important therapeutic target. B7-H4 inhibition might offer an exciting opportunity to inhibit the progression of human pancreatic cancers.     

共刺激分子B7-H4在宫颈癌中的表达及意义

目的:肿瘤微环境中免疫共刺激分子B7-H4与其配体结合后可提供免疫抑制信号,调控肿瘤组织中的免疫应答。本研究探讨B7-H4、Fas及Caspase-3裂解片段在宫颈鳞状细胞癌中的表达及其与临床病理因素的关系,分析其参与肿瘤免疫逃逸的机制。方法:应用免疫组织化学SP法检测23例正常宫颈上皮、38例宫颈上皮内瘤变(CIN)和132例宫颈鳞状细胞癌组织中B7-H4、Fas及Caspase-3裂解片段的表达水平,分析其与宫颈癌各临床病理因素的相关性。结果:B7-H4在正常宫颈上皮组织中不表达,在CIN组织中微弱表达,在宫颈鳞状细胞癌组织中高表达。B7-H4表达与肿瘤的临床分期、淋巴结转移、原发肿瘤大小和肿瘤浸润深度有关,B7-H4与Fas蛋白表达呈现负相关,与Caspase-3裂解片段存在共表达关系。结论:B7-H4在宫颈鳞状细胞癌中过表达可引起Fas蛋白表达下调和Caspase-3裂解片段增多,抑制肿瘤细胞发生凋亡,参与肿瘤逃避宿主的免疫监视,从而促发宫颈癌的发生和发展。阻断B7-H4通路途径,有望成为宫颈鳞状细胞癌治疗的新靶点。     

B7-H4-mediated immunoresistance is supressed by PI3K/Akt/mTOR pathway inhibitors

B7-H4 plays an important role in tumor immune evasion. In previous studies we have found that B7-H4 can translocate to the nucleus, and the exposure to PI3K inhibitor Ly294002 affects B7-H4 subcellular distribution. In this study we report the role of PI3K/Akt pathway in the B7-H4 subcellular distribution and the effect of PI3K/Akt inhibitors on B7-H4-mediated immunoresistance. The involvement of PI3K/Akt pathway in B7-H4 subcellular distribution was evident in experiments with wortmannin, while MDM2 inhibitor nutlin-3 and the mTOR inhibitor rapamycin were used to dissect the signaling downstream of Akt. Wortmannin and rapamycin demonstrated similar effects on B7-H4 subcellular distribution. Exposure to any of these inhibitors decreased levels of membrane B7-H4 while at the same time inducing its nuclear accumulation, while exposure to nutlin-3 had no effect on B7-H4 subcellular distribution. In the T cell proliferation assay, both wortmannin and rapamycin effectively inhibited B7-H4 WT/293 cells-mediated T cell proliferation while exerting no effect on Mock/293 cells. PI3K/Akt/mTOR plays a role in B7-H4 subcellular distribution, while MDM2 does not take part in it. Moreover, we show that wortmannin and rapamycin inhibit B7-H4-mediated tumor immunoresistance through regulating B7-H4 subcellular distribution. Taken together, these results suggest that PI3K/Akt/mTOR inhibitors might be used for adjuvant therapy aimed at inhibition of immune evasion.     

B7-H1 Expression Is Associated with Poor Prognosis in Colorectal Carcinoma and Regulates the Proliferation and Invasion of HCT116 Colorectal Cancer Cells

Background And Objective

The investigation concerning the B7-H1 expression in colorectal cancer cells is at an early stage. It is unclear whether B7-H1 expression may have diagnostic or prognostic value in colorectal carcinoma. Additionally, how B7-H1 is associated with the clinical features of colorectal carcinoma is not known. In order to investigate the relationship between B7-H1 and colorectal cancer, we analyzed B7-H1 expression and its effect in clinical specimens and HCT116 cells.

Methods

Paraffin-embedded specimens from 143 eligible patients were used to investigate the expression of CD274 by immunohistochemistry. We also examined whether B7-H1 itself may be related to cell proliferation, apoptosis, migration and invasion in colon cancer HCT116 cells.

Results

Our results show that B7-H1 was highly expressed in colorectal carcinoma and was significantly associated with cell differentiation status and TNM (Tumor Node Metastasis) stage. Patients with positive B7-H1 expression showed a trend of shorter survival time. Using multivariate analysis, we demonstrate that positive B7-H1 expression is an independent predictor of colorectal carcinoma prognosis. Our results indicate that B7-H1 silencing with siRNA inhibits cell proliferation, migration and invasion. Furthermore, cell apoptosis was also increased by B7-H1 inhibition.

Conclusions

Positive B7-H1 expression is an independent predictor for colorectal carcinoma prognosis. Moreover, knockdown of B7-H1 can inhibit cell proliferation, migration and invasion.     

Phosphoglycerate mutase-derived polypeptide inhibits glycolytic flux and induces cell growth arrest in tumor cell lines

The putative tumor metastasis suppressor protein Nm23-H1 is a nucleoside diphosphate kinase that exhibits a novel protein kinase activity when bound to glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In this study we show that the glycolytic enzyme phosphoglycerate mutase B (PGM) becomes phosphorylated in the presence of the Nm23-H1.GAPDH complex in vitro. Mutation of His-10 in PGM abolishes the Nm23-H1.GAPDH complex-induced phosphorylation. Nm23-H1, GAPDH, and PGM are known to co-localize as shown by free flow isoelectric focusing. In association with Nm23-H1 and GAPDH, PGM could be activated by dCTP, which is a substrate of Nm23-H1, in addition to the well known PGM activator 2,3-bisphosphoglycerate. A synthetic cell-penetrating peptide (PGMtide) encompassing the phosphorylated histidine and several residues from PGM (LIRHGE) promoted growth arrest of several tumor cell lines, whereas proliferation of tested non-tumor cells was not influenced. Analysis of metabolic activity of one of the tumor cell lines, MCF-7, indicated that PGMtide inhibited glycolytic flux, consistent with in vivo inhibition of PGM. The specificity of the observed effect was further determined experimentally by testing the effect of PGMtide on cells growing in the presence of pyruvate, which helps to compensate PGM inhibition in the glycolytic pathway. Thus, growth of MCF-7 cells was not arrested by PGMtide in the presence of pyruvate. The data presented here provide evidence that inhibition of PGM activity can be achieved by exogenous addition of a polypeptide, resulting in inhibition of glycolysis and cell growth arrest in cell culture.     

Overexpression of B7-H1 (PD-L1) significantly associates with tumor grade and postoperative prognosis in human urothelial cancers

PURPOSE: The programmed death-1 (PD-1)/B7-H1 (also called PD-L1) pathway negatively regulates T cell activation and has been suggested to play an important role in regulating antitumor host immunity. To investigate the clinical significance of B7-H1 expression to the tumor grade and postoperative prognosis of patients with urothelial cancer, we analyzed the relationship between B7-H1 expression and various clinicopathological features and postoperative prognosis. EXPERIMENTAL DESIGN: Sixty-five urothelial cancer cases were examined. B7-H1 expression in tumors and the numbers and phenotypes of tumor-infiltrating lymphocytes were evaluated by immunohistochemistry and flow cytometry. RESULTS: A substantial expression of B7-H1 was observed in all urothelial cancers investigated. Tumor specimens from patients with higher WHO grade or primary tumor classifications showed significantly higher percentages of tumor-associated B7-H1. Tumor-associated B7-H1 expression was significantly associated with a high frequency of postoperative recurrence and poor survival rate. Furthermore, multivariate analysis indicated that tumor-associated B7-H1 was more significant prognostic factor than WHO grade. CONCLUSIONS: Our results demonstrate that the aberrant expression of B7-H1 in urothelial cancer is associated with aggressive tumors, suggesting a regulatory role of tumor-associated B7-H1 in antitumor immunity. Therefore, the manipulation of tumor-associated B7-H1 may become a beneficial target for immunotherapy in human urothelial cancer.     

Cloning and characterization of porcine 4Ig-B7-H3: a potent inhibitor of porcine T-cell activation

Background

Members of the B7 superfamily costimulate the proliferation of lymphocytes during the initiation and maintenance of antigen-specific humoral and cell-mediated immune responses. B7-H3 (CD276) is a newly identified member of the B7 superfamily. It has been shown that B7-H3 plays a significant role in regulating T cell response in humans and mice, but it is not known whether a counterpart of human or murine B7-H3 exists in porcine species.

Methodology/Principal Findings

We cloned the porcine 4ig-b7-h3 gene using a blast search at the NCBI database with human b7-h3, RT-PCR and 3′-terminus RACE. Protein sequence analysis showed that the protein encoded by this gene contained 4Ig-like domains and was 90.88% identical with human 4Ig-B7-H3. Results of Dot-blot hybridization and RT-PCR showed that B7-H3 was broadly distributed in porcine tissues mainly as two isoforms, 2Ig-B7-H3 and 4Ig-B7-H3, of which 4Ig-B7-H3 was dominant. We further demonstrated that porcine 4Ig-B7-H3 was able to inhibit the proliferation and cytokine production of porcine T cells activated through the TCR pathway, similar to human B7-H3.

Conclusion

We cloned the porcine 4ig-b7-h3 gene and demonstrated that the porcine 4Ig-B7-H3 serves as a negative regulator for the T-cell immune response.     

B7-H3 enhances tumor immunity in vivo by costimulating rapid clonal expansion of antigen-specific CD8+ cytolytic T cells

B7-H3 is a B7 family molecule with T cell costimulatory function in vitro. The in vivo role of B7-H3 in the stimulation of tumor immunity is unclear. We report here that expression of B7-H3 by transfection of the mouse P815 tumor line enhances its immunogenicity, leading to the regression of tumors and amplification of a tumor-specific CD8+ CTL response in syngeneic mice. Tumor cells engineered to express B7-H3 elicit a rapid clonal expansion of P1A tumor Ag-specific CD8+ CTL in lymphoid organs in vivo and acquire the ability to directly stimulate T cell growth, division, and development of cytolytic activity in vitro. Our results thus establish a role for B7-H3 in the costimulation of T cell immune responses in vivo.     

PI3K/Akt/mTOR信号通路与自噬及肿瘤的关系

自噬是一种以胞质内出现双层膜结构包裹长寿命蛋白和细胞器的自噬体为特征的细胞“自我消化”过程,在维持细胞内稳态、发育、肿瘤发生和感染中发挥重要作用。近来,诸多研究表明,自噬作为一把“双刃剑”,对肿瘤的发生发展既有促进作用,也有抑制作用。PI3K/Akt/mTOR通路由PI3激酶(PI3K)、蛋白激酶B（PKB/Akt）和哺乳动物类雷帕霉素靶蛋白（mTOR）3个作用分子组成,是一个中心的调节机构,对肿瘤细胞的生长与增殖有促进作用,同时对自噬进行抑制。本文就PI3K/Akt/mTOR通路与自噬及肿瘤发生发展的关系作一综述。     

Tumor-infiltrating programmed death receptor-1+ dendritic cells mediate immune suppression in ovarian cancer

Within the ovarian cancer microenvironment, there are several mechanisms that suppress the actions of antitumor immune effectors. Delineating the complex immune microenvironment is an important goal toward developing effective immune-based therapies. A dominant pathway of immune suppression in ovarian cancer involves tumor-associated and dendritic cell (DC)-associated B7-H1. The interaction of B7-H1 with PD-1 on tumor-infiltrating T cells is a widely cited theory of immune suppression involving B7-H1 in ovarian cancer. Recent studies suggest that the B7-H1 ligand, programmed death receptor-1 (PD-1), is also expressed on myeloid cells, complicating interpretations of how B7-H1 regulates DC function in the tumor. In this study, we found that ovarian cancer-infiltrating DCs progressively expressed increased levels of PD-1 over time in addition to B7-H1. These dual-positive PD-1(+) B7-H1(+) DCs have a classical DC phenotype (i.e., CD11c(+)CD11b(+)CD8(-)), but are immature, suppressive, and respond poorly to danger signals. Accumulation of PD-1(+)B7-H1(+) DCs in the tumor was associated with suppression of T cell activity and decreased infiltrating T cells in advancing tumors. T cell suppressor function of these DCs appeared to be mediated by T cell-associated PD-1. In contrast, ligation of PD-1 expressed on the tumor-associated DCs suppressed NF-κB activation, release of immune regulatory cytokines, and upregulation of costimulatory molecules. PD-1 blockade in mice bearing ovarian cancer substantially reduced tumor burden and increased effector Ag-specific T cell responses. Our results reveal a novel role of tumor infiltrating PD-1(+)B7-H1(+) DCs in mediating immune suppression in ovarian cancer.     

B7-H4 Treatment of T Cells Inhibits ERK, JNK, p38, and AKT Activation

B7-H4 is a newly identified B7 homolog that plays an important role in maintaining T-cell homeostasis by inhibiting T-cell proliferation and lymphokine-secretion. In this study, we investigated the signal transduction pathways inhibited by B7-H4 engagement in mouse T cells. We found that treatment of CD3(+) T cells with a B7-H4.Ig fusion protein inhibits anti-CD3 elicited T-cell receptor (TCR)/CD28 signaling events, including phosphorylation of the MAP kinases, ERK, p38, and JNK. B7-H4.Ig treatment also inhibited the phosphorylation of AKT kinase and impaired its kinase activity as assessed by the phosphorylation of its endogenous substrate GSK-3. Expression of IL-2 is also reduced by B7-H4. In contrast, the phosphorylation state of the TCR proximal tyrosine kinases ZAP70 and lymphocyte-specific protein tyrosine kinase (LCK) are not affected by B7-H4 ligation. These results indicate that B7-H4 inhibits T-cell proliferation and IL-2 production through interfering with activation of ERK, JNK, and AKT, but not of ZAP70 or LCK.     

Clinical significance and regulation of the costimulatory molecule B7-H3 in human colorectal carcinoma

B7-H3, a member of the B7-family molecules, plays an important role in adaptive immune responses, and was shown to either promote or inhibit T-cell responses in various experimental systems. B7-H3 was expressed in some human cancers and correlated with poor outcome of cancer patients. However, its exact role in cancer is not known. In the present study, we studied the expression of B7-H3 in the pathologic specimens of 102 patients treated for colorectal carcinoma (CRC) by immunohistochemistry. Strong B7-H3 expression was found in cancer tissues from 54.3% CRC patients, while minimal expression was found in adjacent normal colorectal tissues. Higher B7-H3 expression in tumor positively correlated with a more advanced tumor grade. In addition, consistent with a role of B7-H3 in suppressing tumor immune surveillance, the expression of B7-H3 in cancer cells negatively correlated with the intensity of tumor infiltrating T lymphocytes in both tumor nest and tumor stroma. Furthermore, we found that the level of soluble B7-H3 in sera from CRC patients was higher than healthy donors. TNF-α, an important cancer-promoting inflammatory molecule, was subsequently found to significantly increase the release of soluble B7-H3 in colon cancer cell lines. Therefore, our data suggest that both soluble and membranous B7-H3 proteins are involved in colon cancer progression and evasion of cancer immune surveillance.     

B7-H3 suppresses doxorubicin-induced senescence-like growth arrest in colorectal cancer through the AKT/TM4SF1/SIRT1 pathway

Emerging evidence suggests that cellular senescence induced by chemotherapy has been recognized as a new weapon for cancer therapy. This study aimed to research novel functions of B7-H3 in cellular senescence induced by a low dose of doxorubicin (DOX) in colorectal cancer (CRC). Here, our results demonstrated that B7-H3 knockdown promoted, while B7-H3 overexpression inhibited, DOX-induced cellular senescence. B7-H3 knockdown dramatically enhanced the growth arrest of CRC cells after low-dose DOX treatment, but B7-H3 overexpression had the opposite effect. By RNA-seq analysis and western blot, we showed that B7-H3 prevented cellular senescence and growth arrest through the AKT/TM4SF1/SIRT1 pathway. Blocking the AKT/TM4SF1/SIRT1 pathway dramatically reversed B7-H3-induced resistance to cellular senescence. More importantly, B7-H3 inhibited DOX-induced cellular senescence of CRC cells in vivo. Therefore, targeting B7-H3 or the B7-H3/AKT/TM4SF1/SIRT1 pathway might be a new strategy for promoting cellular senescence-like growth arrest during drug treatment in CRC.Subject terms: Cancer therapy, Drug discovery     

Murine B7-H3 is a negative regulator of T cells

T cell activation is regulated by the innate immune system through positive and negative costimulatory molecules. B7-H3 is a novel B7-like molecule with a putative receptor on activated T cells. Human B7-H3 was first described as a positive costimulator, most potently inducing IFN-gamma production and cellular immunity. In this study we examined the expression and function of mouse B7-H3. B7-H3 is mostly expressed on professional APCs; its expression on dendritic cells appears to be up-regulated by LPS. In contrast to human B7-H3, we found that mouse B7-H3 protein inhibited T cell activation and effector cytokine production. An antagonistic mAb to B7-H3 enhanced T cell proliferation in vitro and led to exacerbated experimental autoimmune encephalomyelitis in vivo. Therefore, mouse B7-H3 serves as a negative regulator of T cell activation and function.     

B7-H3 is expressed in human hepatocellular carcinoma and is associated with tumor aggressiveness and postoperative recurrence

B7-H3, a novel B7 family member, positively or negatively regulates T-cell responses. We investigated the clinical relevance and prognostic significance of B7-H3 in hepatocellular carcinoma (HCC). Western blotting showed B7-H3 upregulation in 17 of 24 (70.8 %) HCC tissues compared with nontumor liver tissues (p = 0.028). B7-H3 immunostaining on tissue microarrays containing 240 HCC patient samples indicated that 225 (93.8 %) tumors had aberrant B7-H3 expression, with strong intensity in 79 (32.9 %) cases, whereas B7-H3 expression in peritumor liver cells was weak in most cases (226; 94.2 %). Notably, patients with high/moderate tumor cell B7-H3 expression showed significantly poorer survival (p = 0.009) and increased recurrence (p = 0.002). After multivariable adjustment, high/moderate B7-H3 expression remained significant for an increased risk of recurrence (hazard ratio = 1.79; 95 % confidence interval = 1.19–2.70; p = 0.005). B7-H3 expression correlated with invasive phenotypes like vascular invasion and advanced tumor stage, and the metastatic potential of HCC cell lines. Flow cytometry showed that B7-H3 expression is inversely correlated with proliferation and interferon-γ production by infiltrating T cells. Interferon-γ stimulation significantly upregulated B7-H3 expression in HCC cells in vitro, implicating B7-H3 expression as a feedback mechanism to evade anti-tumor immunity. Importantly, the prognostic value of B7-H3 expression was validated in an independent cohort of 206 HCC patients. Collectively, our data suggest that B7-H3 was abundantly expressed in HCC and was associated with adverse clinicopathologic features and poor outcome. Thus, B7-H3 represents an attractive target for diagnostic and therapeutic manipulation in human HCC.     

Construction,expression and functional analysis of anti-B7-H4-scFv-CH3 recombinant antibody

The B7-H4 molecule, a unique negative regulator of T lymphocytes which is overexpressed on the surface of various tumor cells, is a particularly important target candidate for tumor therapy because it can be blocked with anti-B7-H4 antibodies to inhibit the B7-H4 signaling pathway. Our previous work established an anti-B7-H4 single-chain variable fragment (scFv) library, so we have now amplified the genes encoding anti-B7-H4-scFv and human IgG1 CH3 and ligated them by overlap extension PCR to obtain a recombinant gene. After sequencing, the gene was cloned into the expression vector pET43.1a and expression was induced in E. coli BL21 (DE3) by isopropyl-β-D-1-thiogalactopyranoside (IPTG). The protein was purified on a nickel-nitrilotriacetic acid (Ni-NTA) resin column and its antigen specificity and affinity were examined by ELISA and western blotting. We also established a Lewis lung cancer model in C57BL/6 mice to further identify the biological function of the scFv protein in vivo. The results showed that tumor volume, body weight and necrotic tissues in the control group were significantly greater than in the experimental group, indicating that selected scFvs had good biological activity and could inhibit tumor growth in tumor-bearing mice. Our work thus offers a new approach for the development of cancer-targeted therapy.     

The immunomodulatory protein B7-H4 is overexpressed in breast and ovarian cancers and promotes epithelial cell transformation

B7-H4 protein is expressed on the surface of a variety of immune cells and functions as a negative regulator of T cell responses. We independently identified B7-H4 (DD-O110) through a genomic effort to discover genes upregulated in tumors and here we describe a new functional role for B7-H4 protein in cancer. We show that B7-H4 mRNA and protein are overexpressed in human serous ovarian cancers and breast cancers with relatively little or no expression in normal tissues. B7-H4 protein is extensively glycosylated and displayed on the surface of tumor cells and we provide the first demonstration of a direct role for B7-H4 in promoting malignant transformation of epithelial cells. Overexpression of B7-H4 in a human ovarian cancer cell line with little endogenous B7-H4 expression increased tumor formation in SCID mice. Whereas overexpression of B7-H4 protected epithelial cells from anoikis, siRNA-mediated knockdown of B7-H4 mRNA and protein expression in a breast cancer cell line increased caspase activity and apoptosis. The restricted normal tissue distribution of B7-H4, its overexpression in a majority of breast and ovarian cancers and functional activity in transformation validate this cell surface protein as a new target for therapeutic intervention. A therapeutic antibody strategy aimed at B7-H4 could offer an exciting opportunity to inhibit the growth and progression of human ovarian and breast cancers.     

B7-H3 is Overexpressed in Patients Suffering Osteosarcoma and Associated with Tumor Aggressiveness and Metastasis

B7-H3 is a member of the B7-family of co-stimulatory molecules, which has been shown to be broadly expressed in various tumor tissues, and which plays an important role in adaptive immune responses. The role of B7-H3 in osteosarcoma, however, remains unknown. In this study we used immunohistochemistry to analyze B7-H3 expression in 61 primary osteosarcoma tissues with case-matched adjacent normal tissues, and 37 osteochondroma and 20 bone fibrous dysplasia tissues. B7-H3 expression was expressed in 91.8% (56/61) of the osteosarcoma lesions, and the intensity of B7-H3 expression in osteosarcoma was significantly increased compared with adjacent normal tissues, osteochondroma and bone fibrous dysplasia tissues (p<0.001). Patients with high tumor B7-H3 levels had a significantly shorter survival time and recurrence time than patients with low tumor B7-H3 levels (p<0.001). Moreover, tumor B7-H3 expression inversely correlated with the number of tumor-infiltrating CD8⁺ T cells (p<0.05). In vitro, increasing expression of B7-H3 promotes osteosarcoma cell invasion, at least in part by upregulating matrix metalloproteinase-2 (MMP-2). In conclusion, our study provides the first evidence of B7-H3 expression in osteosarcoma cells as a potential mechanism controlling tumor immunity and invasive malignancy, and which is correlated with patients’ survival and metastasis.