The Rap G protein signal regulates Notch activation in early thymic progenitor cells, and deregulated Rap activation (Raphigh) results in the development of Notch-dependent T-cell acute lymphoblastic leukemia (T-ALL). We demonstrate that the Rap signal is required for the proliferation and leukemogenesis of established Notch-dependent T-ALL cell lines. Attenuation of the Rap signal by the expression of a dominant-negative Rap1A17 or Rap1GAP, Sipa1, in a T-ALL cell line resulted in the reduced Notch processing at site 2 due to impaired maturation of Adam10. Inhibition of the Rap1 prenylation with a geranylgeranyl transferase inhibitor abrogated its membrane-anchoring to Golgi-network and caused reduced proprotein convertase activity required for Adam10 maturation. Exogenous expression of a mature form of Adam10 overcame the Sipa1-induced inhibition of T-ALL cell proliferation. T-ALL cell lines expressed Notch ligands in a Notch-signal dependent manner, which contributed to the cell-autonomous Notch activation. Although the initial thymic blast cells barely expressed Notch ligands during the T-ALL development from Raphigh hematopoietic progenitors in vivo, the ligands were clearly expressed in the T-ALL cells invading extrathymic vital organs. These results reveal a crucial role of the Rap signal in the Notch-dependent T-ALL development and the progression.
Although the efficacy of zoledronic acid in postmenopausal women with breast cancer has been suggested, the underlying mechanism has not been fully clarified. Therefore, which patients may benefit from zoledronic acid and the optimal frequency of zoledronic acid administration are unclear. This study evaluates the effects of zoledronic acid on the tumor response in postmenopausal women with breast cancer and explores the relationship between its efficacy and γδ T cells.
This study is an open-label, multi-institutional, single-arm, phase II clinical trial. Zoledronic acid will be administered once during preoperative hormonal therapy with letrozole for 24 weeks in postmenopausal women with Estrogen Receptor (ER)-positive , Human Epidermal Growth Factor Receptor 2 (HER2)-negative, clinical T1 or T2 N0M0 breast cancer. The primary endpoint is the objective response rate measured by MRI at 12 and 24 weeks. The secondary endpoints are the associations between the frequency of Vγ2Vδ2 T cells before the administration of zoledronic acid and the objective response, the association between the frequency of Vγ2Vδ2 T cells and the Preoperative Endocrine Prognostic Index score, and the association between the frequency of Vγ2Vδ2 T cells and Ki67 (MIB-1 index).
This study is designed to determine the add-on effect of zoledronic acid during preoperative hormonal therapy and to investigate the changes of the frequency of Vγ2Vδ2 T cells after the administration of zoledronic acid to explore the potential mechanism of zoledronic acid in breast cancer patients.
This trial was registered at the UMIN Clinical Trials Registry as UMIN000008701.
Zoledronic acid; Postmenopausal women; Breast cancer; γδ T cells; Letrozole
Exposing human tumor cells to nitrogen-containing bisphosphonates (N-BPs), such as zoledronic acid (Zol), greatly increases their susceptibility to killing by γδ T cells. Based on this finding and other studies, cancer immunotherapy using γδ T cells and N-BPs has been studied in pilot clinical trials and has shown benefits. Although Zol treatment can render a wide variety of human tumor cells susceptible to γδ T cell killing, there has not been a systematic investigation to determine which types of tumor cells are the most susceptible to γδ T cell-mediated cytotoxicity. In this study, we determined the Zol concentrations required to stimulate half maximal tumor necrosis factor-α production by γδ T cells cultured with various tumor cell lines pretreated with Zol and compared these concentrations with those required for half maximal inhibition of farnesyl diphosphate synthase (FPPS) in the same tumor cell lines. The inhibition of tumor cell growth by Zol was also assessed. We found that FPPS inhibition strongly correlated with γδ T cell activation, confirming that the mechanism underlying γδ T cell activation by Zol is isopentenyl diphosphate (IPP) accumulation due to FPPS blockade. In addition, we showed that γδ TCR-mediated signaling correlated with γδ T cell tumor necrosis factor-α production and cytotoxicity. Some lymphoma, myeloid leukemia, and mammary carcinoma cell lines were relatively resistant to Zol treatment suggesting that assessing tumor sensitivity to Zol may help select those patients most likely to benefit from immunotherapy with γδ T cells.
isopentenyl diphosphate; lymphoma; myeloid cells; nitrogen-containing bisphosphonate; tumor
Human γδ T cells display potent cytotoxicity against various tumor cells pretreated with zoledronic acid (Zol). Zol has shown benefits when added to adjuvant endocrine therapy for patients with early-stage breast cancer or to standard chemotherapy for patients with multiple myeloma. Although γδ T cells may contribute to this additive effect, the responsiveness of γδ T cells from early-stage breast cancer patients has not been fully investigated. In this study, we determined the number, frequency, and responsiveness of Vγ2Vδ2 T cells from early- and late-stage breast cancer patients and examined the effect of IL-18 on their ex vivo expansion. The responsiveness of Vγ2Vδ2 T cells from patients with low frequencies of Vγ2Vδ2 T cells was significantly diminished. IL-18, however, enhanced ex vivo proliferative responses of Vγ2Vδ2 T cells and helper NK cells from patients with either low or high frequencies of Vγ2Vδ2 T cells. Treatment of breast cancer patients with Zol alone decreased the number of Vγ2Vδ2 T cells and reduced their ex vivo responsiveness. These results demonstrate that Zol can elicit immunological responses by γδ T cells from early-stage breast cancer patients but that frequent in vivo treatment reduces Vγ2Vδ2 T cell numbers and their responsiveness to stimulation.
γδ T cells; helper NK cells; breast cancer; phosphoantigen; nitrogen-containing bisphosphonate; IL-18
Enteroendocrine cells are solitary epithelial cells scattered throughout the gastrointestinal tract and produce various types of hormones, constituting one of the largest endocrine systems in the body. The study of these rare epithelial cells has been hampered by the difficulty in isolating them because of the lack of specific cell surface markers. Here, we report that enteroendocrine cells selectively express a tight junction membrane protein, claudin-4 (Cld4), and are efficiently isolated with the use of an antibody specific for the Cld4 extracellular domain and flow cytometry. Sorted Cld4+ epithelial cells in the small intestine exclusively expressed a chromogranin A gene (Chga) and other enteroendocrine cell–related genes (Ffar1, Ffar4, Gpr119), and the population was divided into two subpopulations based on the activity of binding to Ulex europaeus agglutinin-1 (UEA-1). A Cld4+UEA-1− cell population almost exclusively expressed glucose-dependent insulinotropic polypeptide gene (Gip), thus representing K cells, whereas a Cld4+UEA-1+ cell population expressed other gut hormone genes, including glucagon-like peptide 1 (Gcg), pancreatic polypeptide–like peptide with N-terminal tyrosine amide (Pyy), cholecystokinin (Cck), secretin (Sct), and tryptophan hydroxylase 1 (Tph1). In addition, we found that orally administered luminal antigens were taken up by the solitary Cld4+ cells in the small intestinal villi, raising the possibility that enteroendocrine cells might also play a role in initiation of mucosal immunity. Our results provide a useful tool for the cellular and functional characterization of enteroendocrine cells.
Vγ9Vδ2 (also termed Vγ2Vδ2) T cells, a major human peripheral blood γδ T cell subset, recognize microbial (E)-4-hydroxy-3-methylbut-2-enyl diphosphate and endogenous isopentenyl diphosphate in a TCR-dependent manner. The recognition does not require specific accessory cells, antigen uptake, antigen processing, or MHC class I, class II, or class Ib expression. This subset of T cells plays important roles in mediating innate immunity against a wide variety of infections and displays potent and broad cytotoxic activity against human tumor cells. Because γδT cells express both natural killer receptors such as NKG2D and γδ T cell receptors, they are considered to represent a link between innate and adaptive immunity. In addition, activated γδ T cells express a high level of antigen-presenting cell-related molecules and can present peptide antigens derived from destructed cells to αβ T cells. Utilizing these antimicrobial and anti-tumor properties of γδ T cells, preclinical and clinical trials have been conducted to develop novel immunotherapies for infections and malignancies. Here, we review the immunological properties of γδ T cells including the underlying recognition mechanism of nonpeptitde antigens and summarize the results of γδ T cell-based therapies so far performed. Based on the results of the reported trials, γδ T cells appear to be a promising tool for novel immunotherapies against certain types of diseases.
γδ T cells; nonpeptide antigen; tumor; infection; autoimmune and allergic diseases; immunotherapy
Claudin (Cld)-4 is one of the dominant Clds expressed in the kidney and urinary tract, including selective segments of renal nephrons and the entire urothelium from the pelvis to the bladder. We generated Cldn4−/− mice and found that these mice had increased mortality due to hydronephrosis of relatively late onset. While the renal nephrons of Cldn4−/− mice showed a concomitant diminution of Cld8 expression at tight junction (TJ), accumulation of Cld3 at TJ was markedly enhanced in compensation and the overall TJ structure was unaffected. Nonetheless, Cldn4−/− mice showed slightly yet significantly increased fractional excretion of Ca2+ and Cl−, suggesting a role of Cld4 in the specific reabsorption of these ions via a paracellular route. Although the urine volume tended to be increased concordantly, Cldn4−/− mice were capable of concentrating urine normally on dehydration, with no evidence of diabetes insipidus. In the urothelium, the formation of TJs and uroplaques as well as the gross barrier function were also unaffected. However, intravenous pyelography analysis indicated retarded urine flow prior to hydronephrosis. Histological examination revealed diffuse hyperplasia and a thickening of pelvic and ureteral urothelial layers with markedly increased BrdU uptake in vivo. These results suggest that progressive hydronephrosis in Cldn4−/− mice arises from urinary tract obstruction due to urothelial hyperplasia, and that Cld4 plays an important role in maintaining the homeostatic integrity of normal urothelium.
Although Rap GTPases of the Ras family remained enigmatic for years, extensive studies in this decade have revealed diverse functions of Rap signaling in the control of cell proliferation, differentiation, survival, adhesion, and movement. With the use of gene-engineered mice, we have uncovered essential roles of endogenous Rap signaling in normal lymphocyte development of both T- and B-lineage cells. Deregulation of Rap signaling, on the other hand, results in the development of characteristic leukemia in manners highly dependent on the contexts of cell lineages. These results highlight crucial roles of Rap signaling in the physiology and pathology of lymphocyte development.
lymphocyte development; leukemia; RapGTPases; Spa-1; Notch
Trafficking of immune cells is controlled by directed migration of relevant cells toward chemotactic signals. Actin cytoskeleton undergoes continuous remodeling and serves as machinery for cell migration. The mDia family of formins and the Wiskott-Aldrich syndrome protein (WASP)–Arp2/3 system are two major actin nucleating–polymerizing systems in mammalian cells, with the former producing long straight actin filaments and the latter producing branched actin meshwork. Although much is known about the latter, the physiological functions of mDia proteins are unclear. We generated mice deficient in one mDia isoform, mDia1. Although mDia1−/− mice were born and developed without apparent abnormality, mDia1−/− T lymphocytes exhibited impaired trafficking to secondary lymphoid organs in vivo and showed reduced chemotaxis, little actin filament formation, and impaired polarity in response to chemotactic stimuli in vitro. Similarly, mDia1−/− thymocytes showed reduced chemotaxis and impaired egression from the thymus. These results suggest that mDia1 plays a distinct role in chemotaxis in T lymphocyte trafficking.
A transcriptional regulator, Hes1, plays crucial roles in the control of differentiation and proliferation of neuronal, endocrine, and T-lymphocyte progenitors during development. Mechanisms for the regulation of cell proliferation by Hes1, however, remain to be verified. In embryonic carcinoma cells, endogenous Hes1 expression was repressed by retinoic acid in concord with enhanced p27Kip1 expression and cell cycle arrest. Conversely, conditional expression of a moderate but not maximal level of Hes1 in HeLa cells by a tetracycline-inducible system resulted in reduced p27Kip1 expression, which was attributed to decreased basal transcript rather than enhanced proteasomal degradation, with concomitant increases in the growth rate and saturation density. Hes1 induction repressed the promoter activity of a 5′ flanking basal enhancer region of p27Kip1 gene in a manner dependent on Hes1 expression levels, and this was mediated by its binding to class C sites in the promoter region. Finally, hypoplastic fetal thymi, as well as livers and brains of Hes1-deficient mice, showed significantly increased p27Kip1 transcripts compared with those of control littermates. These results have suggested that Hes1 directly contributes to the promotion of progenitor cell proliferation through transcriptional repression of a cyclin-dependent kinase inhibitor, p27Kip1.
Brd4 is a mammalian protein that contains a double bromodomain. It binds to chromatin and regulates cell cycle progression at multiple stages. By immunopurification and mass spectrometry, we identified a Rap GTPase-activating protein (GAP), signal-induced proliferation-associated protein 1 (SPA-1), as a factor that interacts with Brd4. SPA-1 localizes to the cytoplasm and to a lesser degree in the nucleus, while Brd4 resides in the nucleus. Bifluorescence complementation revealed that Brd4 and SPA-1 interact with each other in the nucleus of living cells. Supporting the functional importance of the interaction, Brd4 enhanced Rap GAP activity of SPA-1. Furthermore ectopic expression of SPA-1 and Brd4 redirected subcellular localization of the partner and disrupted normal cell cycle progression. These effects were, however, reversed by coexpression of the two proteins, indicating that a proper balance between Brd4 and SPA-1 in G2 is required for cell division. This work reveals a novel link between Brd4 and a GTPase-dependent mitogenic signaling pathway.
Activation of T cells by antigen requires adhesive interactions with antigen-presenting cells (APC) in which leukocyte function-associated antigen 1 (LFA-1) and intercellular adhesion molecules (ICAMs) are important. However, it is not well understood what signaling molecules regulate this process and how the modulation of adhesive events influences T-cell activation. Here we show that Rap1 is activated in T cells in an antigen-dependent manner and accumulated at the contact site of T-cell and antigen-loaded APC. Inhibition of Rap1 activation by a dominant-negative Rap1 or SPA-1, a Rap1 GTPase-activating protein, abrogates LFA-1-ICAM-1-mediated adhesive interactions with antigen-pulsed APC and the subsequent T-cell-receptor triggering and interleukin-2 production. Conversely, augmented antigen-dependent Rap1 activation by the expression of wild-type Rap1 enhances these responses but culminates in apoptosis by Fas and FasL. Thus, Rap1 functions as a key regulator of T-cell and APC interactions and modulates T-cell responses from productive activation to activation-induced cell death by regulating the strength of adhesive interactions. Moreover, constitutive Rap1 activation rendered T cells unresponsive with accumulation of p27Kip1. Our study indicates that the activation state of Rap1 has a decisive effect on the T-cell response to antigen.
PD-1 is an immunoglobulin superfamily member bearing an immunoreceptor tyrosine-based inhibitory motif, and disruption of the PD-1 gene results in the development of lupus-like autoimmune diseases. In this study, we examined effects of the PD-1 deficiency on the thymocyte differentiation at the clonal level using T cell receptor (TCR)-β (Vβ8) and TCR-α/β (H-Y and 2C) transgenic mice. In these TCR transgenic lines, PD-1 expression in the thymus was variably augmented, but as in the normal mice, confined largely to the CD4−CD8− thymocytes. The transgenic mice crossed with PD-1−/− mice in the neutral genetic backgrounds exhibited selective increase in the CD4+CD8+ (DP) population with little effect on other thymocytes subsets. Similarly, the absence of PD-1 facilitated expansion of DP thymocytes in recombination activating gene (RAG)-2−/− mice by anti-CD3ε antibody injection. On the other hand, H-Y or 2C transgenic PD-1−/− mice with the positively selecting background showed significantly reduced efficiency for the generation of CD8+ single positive cells bearing the transgenic TCR-α/β in spite of the increased DP population. These results collectively indicate that PD-1 negatively regulates the β selection and modulates the positive selection, and suggest that PD-1 deficiency may lead to the significant alteration of mature T cell repertoire.
immunoreceptor tyrosine-based inhibitory motif; knock-out mice; positive selection; T cell receptor transgenic mice; RAG-2–deficient mice
To identify the intracellular signals which increase the adhesiveness of leukocyte function-associated antigen 1 (LFA-1), we established an assay system for activation-dependent adhesion through LFA-1/intercellular adhesion molecule 1 ICAM-1 using mouse lymphoid cells reconstituted with human LFA-1 and then introduced constitutively active forms of signaling molecules. We found that the phorbol myristate acetate (PMA)-responsive protein kinase C (PKC) isotypes (α, βI, βII, and δ) or phosphatidylinositol-3-OH kinase (PI 3-kinase) itself activated LFA-1 to bind ICAM-1. H-Ras and Rac activated LFA-1 in a PI 3-kinase-dependent manner, whereas Rho and R-Ras had little effect. Unexpectedly, Rap1 was demonstrated to function as the most potent activator of LFA-1. Distinct from H-Ras and Rac, Rap1 increased the adhesiveness independently of PI 3-kinase, indicating that Rap1 is a novel activation signal for the integrins. Rap1 induced changes in the conformation and affinity of LFA-1 and, interestingly, caused marked LFA-1/ICAM-1-mediated cell aggregation. Furthermore, a dominant negative form of Rap1 (Rap1N17) inhibited T-cell receptor-mediated LFA-1 activation in Jurkat T cells and LFA-1/ICAM-1-dependent cell aggregation upon differentiation of HL-60 cells into macrophages, suggesting that Rap1 is critically involved in physiological processes. These unique functions of Rap1 in controlling cellular adhesion through LFA-1 suggest a pivotal role as an immunological regulator.
Streptococcal pyrogenic exotoxin C (SPEC), when injected intradermally, induces erythema in unsensitized rabbits. In the present study, we examined whether this erythema induction is due to the T-cell stimulatory activity of SPEC as a superantigen. Analysis by using single-residue mutant SPECs indicated that mutant SPECs Y15I, A16E, and Y17I, in which tyrosine 15, alanine 16, and tyrosine 17 were replaced with isoleucine, glutamic acid, and isoleucine, respectively, exhibited significantly reduced mitogenic activity for Vβ2+ human T cells in vitro, and Y15I showed as much as a 1,000-fold reduction. Y15I mutant SPEC, however, retained the ability to bind to major histocompatibility complex class II antigen and to form a homodimer, implying that residue 15 is critically important for the interaction of SPEC with T-cell antigen receptor β chains. When injected intradermally into normal rabbits, wild-type SPEC induced a characteristic erythema after 3 h in a dose-dependent fashion, which was associated with polymorphonuclear and mononuclear cell infiltration. This erythema formation was found to be severely suppressed by systemic pretreatment with cyclosporin A, suggesting the involvement of host T cells. Y15I mutant SPEC exhibited nearly 1,000-fold less erythema induction in vivo than wild-type SPEC. Altogether, the present results strongly suggest that erythema induction in rabbits by SPEC is attributable mostly to its T-cell stimulatory activity as a superantigen.