Tetraspanin protein CD151 is abundant on endothelial cells. To determine whether CD151 affects angiogenesis, Cd151-null mice were prepared. Cd151-null mice showed no vascular defects during normal development or during neonatal oxygeninduced retinopathy. However, Cd151-null mice showed impaired pathologic angiogenesis in other in vivo assays (Matrigel plug, corneal micropocket, tumor implantation) and in the ex vivo aortic ring assay. Cd151-null mouse lung endothelial cells (MLECs) showed normal adhesion and proliferation, but marked alterations in vitro, in assays relevant to angiogenesis (migration, spreading, invasion, Matrigel contraction, tube and cable formation, spheroid sprouting). Consistent with these functional impairments, and with the close, preferential association of CD151 with laminin-binding integrins, Cd151-null MLECs also showed selective signaling defects, particularly on laminin substrate. Adhesion-dependent activation of PKB/c-Akt, e-NOS, Rac, and Cdc42 was diminished, but Raf, ERK, p38 MAP kinase, FAK, and Src were unaltered. In Cd151-null MLECs, connections were disrupted between laminin-binding integrins and at least 5 other proteins. In conclusion, CD151 modulates molecular organization of laminin-binding integrins, thereby supporting secondary (ie, after cell adhesion) functions of endothelial cells, which are needed for some types of pathologic angiogenesis in vivo. Selective effects of CD151 on pathologic angiogenesis make it a potentially useful target for anticancer therapy. IntroductionAngiogenesis, the formation of new blood vessels from preexisting vasculature, is crucial for many physiologic and pathologic situations. [1][2][3] It involves coordinated endothelial cell proliferation, migration, and tube formation, with integrin-type adhesion receptors playing major roles. [4][5][6] Although vitronectin-, fibronectin-, and collagen-binding integrins have been most extensively studied, laminin-binding integrins (␣3␤1, ␣6␤1, ␣6␤4) are also involved. [7][8][9][10][11] For example, during the later stages of angiogenesis, ␣3␤1 and ␣6␤1 integrins may retard morphogenic and proliferative events, while promoting basement membrane assembly, pericyte association, and tube stabilization. 7 By contrast, ␣6␤4 may regulate the onset of pathologic angiogenesis in mature blood vessels. 12 CD151, a tetraspanin protein family member, 13 associates closely with laminin-binding integrins, thereby modulating ␣3␤1-, ␣6␤1-, and ␣6␤4-dependent neurite outgrowth, cell migration, cell morphology, and adhesion strengthening. Mutation of CD151 in humans yielded kidney and skin disorders, but no obvious impairments in blood vessel formation or function were noted. 14 Mice in which Cd151 was deleted were surprisingly normal, while showing only ex vivo deficiencies in platelet aggregation, keratinocyte migration, and T-cell proliferation. 15,16 Again, there were no obvious blood vessel deficiencies. CD151 is present on many cell types, including endothelial cells, where it may either promote 17 or inhibit 18...

Tetraspanins CD9 and CD81 facilitate the fusion between gametes, myoblasts, or virus-infected cells. Here, we investigated the role of these tetraspanins in the fusion of mononuclear phagocytes. Expression of CD9 and CD81 and their complex formation with integrins were up-regulated when blood monocytes were cultured under normal conditions. Under fusogenic conditions in the presence of Con A, CD9 and CD81 up-regulation was inhibited, and their complex formation with integrins was down-regulated. Anti-CD9 and -CD81 antibodies, which were previously shown to inhibit the fusion of gametes, myoblasts, and virus-infected cells, unexpectedly promoted the fusion of monocytes and alveolar macrophages. However, these effects were not due to altered cell adhesion, aggregation, or cytokine production. When stimulated in vitro or in vivo, alveolar macrophages and bone marrow cells of CD9- and CD81-null mice formed larger numbers of multinucleated cells than those of wild-type mice. Finally, CD9/CD81 double-null mice spontaneously developed multinucleated giant cells in the lung and showed enhanced osteoclastogenesis in the bone. These results suggest that CD9 and CD81 coordinately prevent the fusion of mononuclear phagocytes.

The aim of this study was to investigate the clinical impact of sarcopenia on the efficacy of programmed death (PD)-1 inhibitors. We retrospectively reviewed the medical records of all patients treated with nivolumab or pembrolizumab between January 2016 and September 2018 for previously treated advanced non–small cell lung cancer (NSCLC). The cross-sectional area of the psoas muscle at the level of the third lumbar vertebra on baseline computed tomography was assessed to calculate the psoas muscle index (PMI). Sarcopenia was defined based on PMI cut-off values for Asian adults (6.36 cm 2 /m 2 for males and 3.92 cm 2 /m 2 for females). A total of 42 patients were analysed. The prevalence of sarcopenia was 52.4%. Sarcopenia was significantly associated with poorer progression-free survival (PFS) (median, 2.1 vs. 6.8 months, p = 0.004). Compared to patients with sarcopenia, those without sarcopenia had a higher overall response rate (40.0% vs. 9.1%, p = 0.025) and 1-year PFS rate (38.1% vs. 10.1%). In conclusion, sarcopenia at baseline as determined using computed tomography is a significant predictor of worse outcome in patients with advanced NSCLC receiving PD-1 blockade. Screening for sarcopenia may help identify patients more likely to achieve a long-term response in routine clinical practice.

BACKGROUND. The PD-1–blocking antibody nivolumab persists in patients several weeks after the last infusion. However, no study has systematically evaluated the maximum duration that the antibody persists on T cells or the association between this duration and residual therapeutic efficacy or potential adverse events.METHODS. To define the duration of binding and residual efficacy of nivolumab after discontinuation, we developed a simplified strategy for T cell monitoring and used it to analyze T cells from peripheral blood from 11 non–small cell lung cancer patients previously treated with nivolumab. To determine the suitability of our method for other applications, we compared transcriptome profiles between nivolumab-bound and nivolumab-unbound CD8 T cells. We also applied T cell monitoring in 2 nivolumab-treated patients who developed progressive lung tumors during long-term follow-up.RESULTS. Prolonged nivolumab binding was detected more than 20 weeks after the last infusion, regardless of the total number of nivolumab infusions (2–15 doses) or type of subsequent treatment, in 9 of the 11 cases in which long-term monitoring was possible. Ki-67 positivity, a proliferation marker, in T cells decreased in patients with progressive disease. Transcriptome profiling identified the signals regulating activation of nivolumab-bound T cells, which may contribute to nivolumab resistance. In 2 patients who restarted nivolumab, T cell proliferation markers exhibited the opposite trend and correlated with clinical response.CONCLUSIONS. Although only a few samples were analyzed, our strategy of monitoring both nivolumab binding and Ki-67 in T cells might help determine residual efficacy under various types of concurrent or subsequent treatment.TRIAL REGISTRATION. University Hospital Medical Information Network Clinical Trials Registry, UMIN000024623.FUNDING. This work was supported by Japan Society for the Promotion of Science KAKENHI (JP17K16045, JP18H05282, and JP15K09220), Japan Agency for Medical Research and Development (JP17cm0106310, JP18cm0106335 and JP18cm059042), and Core Research for Evolutional Science and Technology (JPMJCR16G2).

Summary Regulatory B cells (Breg) have immune suppressive functions in various autoimmune/inflammation models and diseases, and are found enriched in diverse B-cell subsets. The lack of a unique marker or set of markers efficiently identifying Breg cells impedes detailed investigation into their origin, development, and immunological roles. Here, we perform transcriptome analysis of IL10-expressing B cells to identify key regulators for Breg biogenesis and function and identify CD9, a tetraspanin-family transmembrane protein, as a key surface marker for most mouse IL10+ B cells and their progenitors. CD9 plays a role in the suppressive function of IL10+ B cells in ex-vivo T cell proliferation assays through a mechanism that is dependent upon B/T cell interactions. CD9+ B cells also demonstrate inhibition of Th1 mediated contact hypersensitivity in an in vivo model system. Taken together, our findings implicate CD9 in the immunosuppressive activity of regulatory B cells.