The Role Of Human B7-H3in Inflammatory Responses And Tumor Immune Escape Of Lung Cancer

Part ⅰIdentification of Soluble CD276(B7-H3) and analysis of itsClinical Significance in bacterical SepsisExpression of membrane CD276(mB7-H3) has been reported on dendritic cells(DCs), monocytes, activated T cells, and various carcinoma cells. However, reportsconcerning its in vivo function have been inconsistent. Moreover, whether there is asoluble form of this protein is not known. In this study, using a sensitive dualmonoclonal antibody sandwich enzyme-linked immunosorbent assay (ELISA) to detectthe soluble form of B7-H3(sB7-H3), we demonstrated the release of sB7-H3bymonocytes, DCs, activated T cells, and various mB7-H3+but not mB7-H3–carcinomacells. Release from cells was blocked by addition of a matrix metalloproteinase inhibitor(MMPI), which concomitantly caused the accumulation of B7-H3on the cell surface.To determine the level of circulating sB7-H3, more than200serum samples wereincluded in the study. The results indicated that sB7-H3was present at high levels in allserum samples. Western blotting of sB7-H3from cell culture supernatants or sera ofhealthy donors indicated that the molecular size was approximately16kDa. SolubleB7-H3was able to bind to the B7-H3receptor (B7-H3R) on activated T cells, whichshowed that sB7-H3is a functionally active form. Furthermore, we found that patientsdiagnosed with sepsis, in contrast to healthy individuals, exhibited significant levels ofraised plasma soluble B7-H3(sB7-H3) and that this level correlated with the clinicaloutcome and levels of plasma TNF-and IL-6.These results indicate that release ofsB7-H3from the cell surface is mediated by a matrix metalloproteinase and probablyregulates B7-H3R/B7-H3interactions in vivo. Cleavage of sB7-H3to an active solubleform would alter both proximal and distal cellular responses in inflammatory responses. Part ⅱB7-H3Augments the Septic Inflammatory Response inTLR2/TLR4-dependent mannerB7-H3, a new member of the B7superfamily, acts as both a T cell costimulatorand coinhibitor, and thus plays a key role in the regulation of T cell-mediated immuneresponses. However, it is unclear whether B7-H3is involved in the innate immunemonocyte/macrophage-mediated inflammatory response. In levels analysis of B7-H3Rin patients with sepsis, we found that a putative receptor for B7-H3was detected onmonocytes and peritoneal macrophages from septic patients, but not on monocytes fromhealthy donors. On this basis, we investigate the effect of B7-H3on mono/macrophagein vitro and in vivo. Here we show that, although B7-H3alone failed to stimulateproinflammatory cytokine release from murine bone marrow-derived macrophages(BMM), it strongly augmented both gram-negative lipopolysaccharide (LPS) andgram-positive bacterial lipoprotein (BLP) induced NF-B activation and inflammatoryresponse. This occurred in both a TLR4-and TLR2-dependent manner. Takentogether, our data indicate that significantly elevated plasma sB7-H3in septic patientsmay predict a poor outcome. Furthermore, we demonstrate that B7-H3functions as acostimulator of innate immunity by augmenting proinflammatory cytokine release frombacterial cell wall product-stimulated monocytes/macrophages. Part ⅲA Novel Subset of Tumor-infiltrating B7-H3+CD14+HLA-DR-Myeloid-derived Suppressor Cells Preferentially InduceRegulatory T Cells Leading to Tumor ProgressionMyeloid-derived suppressor cells (MDSCs) are potent immune-suppressive cellspromoting tumor progression and metastasis. Although surface markers of Gr-1andCD11b are widely used to define MDSC in mice, human MDSCs lack definitivephenotypic markers. Here, we showed that CD14+HLA-DR-lowMDSCs were significantly increased in blood and tumor tissues of non-small cell lung cancer patients.Intriguingly, we found that B7-H3molecule was exclusively expressed on a subset oftumor-infiltrating CD14+HLA-DR-lowMDSCs but not in peripheral blood MDSCs.Both B7-H3+and B7-H3-CD14+HLA-DR-lowMDSCs exhibited potent T cellsuppressive activity. However, B7-H3+MDSCs, as compared to B7-H3-MDSCs,showed increased tumor-promoting activity and preferentially induced Treg expansion.Correlation analyses revealed that B7-H3+MDSCs, but not B7-H3-MDSCs, werepositively correlated with Treg infiltration. Furthermore, in mouse lung cancer model,B7-H3+MDSCs were found within the tumor microenvironment and increased duringtumor progression. Similarly, this subset of MDSCs exhibited potent immunesuppressive activity and induced Treg expansion. Taken together, we identify a novelsubset of MDSCs within the tumor microenvironment that preferentially inducesregulatory T cell expansion leading to tumor progression.