Targeting activin receptor-like kinase 7 ameliorates adiposity and associated metabolic disorders.

Activin receptor-like kinase 7 (ALK7) is a type I receptor in the TGF-ß superfamily preferentially expressed in adipose tissue and associated with lipid metabolism. Inactivation of ALK7 signaling in mice results in increased lipolysis and resistance to both genetic and diet-induced obesity. Human genetic studies have recently revealed an association between ALK7 variants and both reduced waist to hip ratios and resistance to development of diabetes. In the present study, treatment with a neutralizing mAb against ALK7 caused a substantial loss of adipose mass and improved glucose intolerance and insulin resistance in both genetic and diet-induced mouse obesity models. The enhanced lipolysis increased fatty acid supply from adipocytes to promote fatty acid oxidation in muscle and oxygen consumption at the whole-body level. The treatment temporarily increased hepatic triglyceride levels, which resolved with long-term Ab treatment. Blocking of ALK7 signals also decreased production of its ligand, growth differentiation factor 3, by downregulating S100A8/A9 release from adipocytes and, subsequently, IL-1ß release from adipose tissue macrophages. These findings support the feasibility of potential therapeutics targeting ALK7 as a treatment for obesity and diabetes.

Anti-Müllerian hormone concentration regulates activin receptor-like kinase-2/3 expression levels with opposing effects on ovarian cancer cell survival.

Anti­Müllerian hormone (AMH) type II receptor (AMHRII) and the AMH/AMHRII signaling pathway are potential therapeutic targets in ovarian carcinoma. Conversely, the role of the three AMH type I receptors (AMHRIs), namely activin receptor­like kinase (ALK)2, ALK3 and ALK6, in ovarian cancer remains to be clarified. To determine the respective roles of these three AMHRIs, the present study used four ovarian cancer cell lines (COV434­AMHRII, SKOV3­AMHRII, OVCAR8, KGN) and primary cells isolated from tumor ascites from patients with ovarian cancer. The results demonstrated that ALK2 and ALK3 may be the two main AMHRIs involved in AMH signaling at physiological endogenous and supraphysiological exogenous AMH concentrations, respectively. Supraphysiological AMH concentrations (25 nM recombinant AMH) were associated with apoptosis in all four cell lines and decreased clonogenic survival in COV434­AMHRII and SKOV3­AMHRII cells. These biological effects were induced via ALK3 recruitment by AMHRII, as ALK3­AMHRII dimerization was favored at increasing AMH concentrations. By contrast, ALK2 was associated with AMHRII at physiological endogenous concentrations of AMH (10 pM). Based on these results, tetravalent IgG1­like bispecific antibodies (BsAbs) against AMHRII and ALK2, and against AMHRII and ALK3 were designed and evaluated. In vivo, COV434­AMHRII tumor cell xenograft growth was significantly reduced in all BsAb­treated groups compared with that in the vehicle group (P=0.018 for BsAb 12G4­3D7; P=0.001 for all other BsAbs). However, the growth of COV434­AMHRII tumor cell xenografts was slower in mice treated with the anti­AMRII­ALK2 BsAb 12G4­2F9 compared with that in animals that received a control BsAb that targeted AMHRII and CD5 (P=0.048). These results provide new insights into type I receptor specificity in AMH signaling pathways and may lead to an innovative therapeutic approach to modulate AMH signaling using anti­AMHRII/anti­AMHRI BsAbs.

Development of conformational antibodies targeting Cripto-1 with neutralizing effects in vitro.

Human Cripto-1 (Cripto-1), the founding member of the EGF-CFC superfamily, is a key regulator of many processes during embryonic development and oncogenesis. Cripto-1 is barely present or even absent in normal adult tissues while it is aberrantly re-expressed in various tumors. Blockade of the CFC domain-mediated Cripto-1 functions is acknowledged as a promising therapeutic intervention point to inhibit the tumorigenic activity of the protein. In this work, we report the generation and characterization of murine monoclonal antibodies raised against the synthetic folded CFC [112-150] domain of the human protein. Through subtractive ELISA assays clones were screened for the ability to specifically recognize "hot spot" residues on the CFC domain, which are crucial for the interaction with Activin Type I receptor (ALK4) and GRP78. On selected antibodies, SPR and epitope mapping studies have confirmed their specificity and have revealed that recognition occurs only on a conformational epitope. Furthermore, FACS analyses have confirmed the ability of 1B4 antibody to recognize the membrane-anchored and soluble native Cripto-1 protein in a panel of human cancer cells. Finally, we have evaluated its functional effects through in vitro cellular signaling assays and cell cycle analysis. These findings suggest that the selected anti-CFC mAbs have the potential to neutralize the protein oncogenic activity and may be used as theranostic molecules suitable as tumor homing agents for Cripto-1-overexpressing cancer cells and tissues and to overcome drug-resistance in routine cancer therapies.

Cutting Edge: ACVRL1 Signaling Augments CD8α+ Dendritic Cell Development.

Dendritic cells (DCs) are a collection of different subtypes, each of which is characterized by specific surface markers, gene-expression patterns, and distinct functions. Members of the IFN regulatory factor family play critical roles in DC development and functions. Recently, Irf8 was shown to activate TGF-ß signaling, which led to exacerbated neuroinflammation in the experimental autoimmune encephalomyelitis mouse model. We analyzed the effect of Irf8 on TGF-ß/bone morphogenetic protein pathway-specific genes in DCs and identified Acvrl1, a type I TGF-ß superfamily receptor, as a gene strongly induced by Irf8 expression. Among various DC subtypes, Acvrl1 is differentially expressed in CD8α(+) DCs. ACVRL1 signaling augmented Irf8-directed classical CD8α(+) DC development. Irf8 expression is essential for plasmacytoid DC and CD8α(+) DC development, and this study demonstrates that ACVRL1 signaling plays a pivotal role whereby it suppresses plasmacytoid DC development while enhancing that of CD8α(+) DCs, thus contributing to DC diversity development.

RNAi screen for kinases and phosphatases that play a role in antigen presentation by dendritic cells.

Effective CD8(+) T-cell responses against tumor or microbial antigens that are not directly expressed in antigen-presenting cells (APCs) depend on the cross-presentation of these antigens on MHC class I in APCs. To identify signaling molecules that regulate cross-presentation, we used lentiviral-based RNA interference to test the roles of hundreds of kinases and phosphatases in this process. Our study uncovered eight previously unknown genes, consisting of one positive and seven negative regulators of antigen cross-presentation. Depletion of Acvr1c, a type I receptor for TGF-ß family of signaling molecules, led to an increase in CD80 and CD86 co-stimulator surface expression and secreted IL-12 in mouse bone marrow-derived DCs, as well as antigen-specific T-cell proliferation.

A model-based approach to predicting the human pharmacokinetics of a monoclonal antibody exhibiting target-mediated drug disposition.

In the drug discovery and development setting, the ability to accurately predict the human pharmacokinetics (PK) of a candidate compound from preclinical data is critical for informing the effective design of the first-in-human trial. PK prediction is especially challenging for monoclonal antibodies exhibiting nonlinear PK attributed to target-mediated drug disposition (TMDD). Here, we present a model-based method for predicting the PK of PF-03446962, an IgG2 antibody directed against human ALK1 (activin receptor-like kinase 1) receptor. Systems parameters as determined experimentally or obtained from the literature, such as binding affinity (k(on) and k(off)), internalization of the drug-target complex (k(int)), target degradation rate (k(deg)), and target abundance (R(0)), were directly integrated into the modeling and prediction. NONMEM 7 was used to model monkey PK data and simulate human PK profiles based on the construct of a TMDD model using a population-based approach. As validated by actual patient data from a phase I study, the human PK of PF-03446962 were predicted within 1- to 2-fold of observations. Whereas traditional approaches fail, this approach successfully predicted the human PK of a monoclonal antibody exhibiting nonlinearity because of TMDD.

Immune responses to self-antigens in asthma patients: clinical and immunopathological implications.

Asthma leads to chronic airway inflammation that shares pathological features of chronic rejection after lung transplantation. Due to the significant role of autoimmunity in chronic rejection, we hypothesized that immunity to self-antigens may also be present in asthma. The goal was to define immune responses to self-antigens in patients with asthma. Blood and clinical data were collected from 99 asthmatics and 60 controls. Serum was analyzed for antibodies (Abs) to collagen V (ColV) by enzyme-linked immunosorbent assay and correlated with disease severity. Asthmatics' sera were tested in a human protein array to determine immune responses to other self-antigens. Asthmatics had higher concentrations of Abs to ColV (predominantly immunoglobulin G isotype) compared with controls (p < 0.01). These Abs correlated with severe asthma (p < 0.01) and corticosteroid use (p = 0.032). Additionally, Abs to novel self-antigens epidermal group factor receptor (EGFr), activin A type 1 receptor, and α-catenin were detected in asthmatics. We conclude that Abs to self-antigens (ColV, EGFr, activin A type 1 receptor, and α-catenin) are present in the sera of asthmatics, correlating with clinical disease. Epithelial damage from airway inflammation during asthma may result in the exposure of cryptic self-antigens or their determinants, resulting in immune response to self-antigens, which may contribute to the pathogenesis of asthma.

[BMP7 signaling via BMPR1A, BMPR1B inhibits the proliferation of lung large carcinoma NCI-H460 cell].

BACKGROUND AND OBJECTIVE: It has been demonstrated that bone morphogenetic protein 7 (BMP7) may both inhibit and enhance cell proliferation of many kinds of cancers, but the impact of BMP7 on lung cancer cells and the exact mechanisms are not clear. The aim of this study is to investigate the effect of BMP7 on proliferation of lung carcinoma cells and explore the roles of different types of I receptors in BMP7 signal transmission by blocking endogenous BMPRIs. METHODS: The levels of expression of BMPIRs (BMP7 type I receptors) mRNA in four different NSCLC (human non-small cell lung tumor) cell lines and HBE (normal human bronchial epithelial) cell were detected by RT-PCR. The responsiveness of pulmonary large carcinoma NCI-H460 cell to BMP7 treatment as well as to a combination of BMP7 and anti-BMPIRs treatment in proliferation were detected by MTT. RESULTS: RT-PCR showed that NCI-H460 cells expressed all three types of BMPIRs; MTT showed that BMP7 inhibit the proliferation of NCI-H460 cell line. Blocking endogenous BMPR1A, BMPR1B obviously reversed the inhibition of BMP7 on the proliferation of NCI-H460 cell respectively (P = 0.003, P = 0.014). Moreover, blocking both endogenous BMPR1A and BMPR1B almost offset the effect of BMP7 on the proliferation of NCI-H460 cell completely (P < 0.001). But ACVR1A blocking did not affect the proliferation of NCI-H460 cell et al (P = 0.074). CONCLUSIONS: BMP7 signaling via BMPR1A and BMPR1B inhibits the proliferation of pulmonary large carcinoma cell NCI-H460.

Activin and transforming growth factor-beta signaling pathways are activated after allergen challenge in mild asthma.

BACKGROUND: Both transforming growth factor (TGF)-beta(1) and activin-A have been implicated in airway remodeling in asthma, but the modulation of their specific signaling pathways after disease activation remains undefined. OBJECTIVE: To define the expression kinetics of TGF-beta(1), activin-A ligands, and follistatin (a natural activin inhibitor), their type I and type II receptors (activin-like kinase[ALK]-1, ALK-5, ALK-4, TbetaRII, and ActRIIA/RIIB) and activation of signaling (via phosphorylated (p) Smad2), in the asthmatic airway after allergen challenge. METHODS: Immunohistochemistry was performed on bronchial biopsies from 15 mild atopic patients with asthma (median age, 25 years; median FEV(1)% predicted, 97%) at baseline and 24 hours after allergen inhalation. Functional effects of activin-A were evaluated by using cultured normal human bronchial epithelial (NHBE) cells. RESULTS: pSmad2(+) epithelial cells increased at 24 hours (P = .03), and pSmad2 was detected in submucosal cells. No modulation of activin-A, follistatin, or TGF-beta(1) expression was demonstrated. Activin receptor(+) cells increased after allergen challenge: ALK-4 in epithelium (P = .04) and submucosa (P = .04), and ActRIIA in epithelium (P = .01). The TGF-beta receptor ALK-5 expression was minimal in the submucosa at baseline and after challenge and was downregulated in the epithelium after challenge (P = .02), whereas ALK-1 and TbetaRII expression in the submucosa increased after allergen challenge (P = .03 and P = .004, respectively). ALK-1 and ALK-4 expression by T cells was increased after allergen challenge. Activin-A induced NHBE cell proliferation, was produced by NHBE cells in response to TNF-alpha, and downregulated TNF-alpha and IL-13-induced chemokine production by NHBE cells. CONCLUSION: Both TGF-beta and activin signaling pathways are activated on allergen provocation in asthma. Activin-A may contribute to resolution of inflammation.

TGF-{beta} signaling of human T cells is modulated by the ancillary TGF-{beta} receptor endoglin.

Transforming growth factor beta (TGF-beta) inhibits T cell activation and alters differentiation of naive T cells into effector cells. Although four main cell-surface proteins can interact with TGF-beta, only the signaling receptors type I (TGF-betaR type I) and type II (TGF-betaR type II) have so far been described on T cells. The aim of the present study was to investigate the expression of the ancillary receptor endoglin (CD105) by T cells and its role in TGF-beta-mediated signal transduction and function. CD105 expression was analyzed on resting and activated human CD4(+) T cells by flow cytometry, western blot, immunoprecipitation, proliferation and SMAD-responsive reporter gene assays. CD4(+) T cells constitutively expressed CD105 in memory T cells and partially also in naive T cells; however, surface expression is regulated and is increased following TCR engagement, which induced serine/threonine phosphorylation of CD105. In contrast to the suppressive signal mediated by the TGF-beta, cross-linking of CD105 substantially enhanced T cell proliferation, indicating that CD105 by itself mediates signal transduction. Furthermore, CD105 cross-linking induced SMAD-independent signaling via ERK kinase phosphorylation. The present study demonstrates that CD105 is expressed on the surface by activated CD4(+) T cells and CD3 regulated by post-translational means. Furthermore, CD105 acts as a regulatory receptor, counteracting TGF-beta-mediated suppression.

Lack of circulating autoantibodies to bone morphogenetic protein receptor-II or activin receptor-like kinase 1 in mixed connective tissue disease patients with pulmonary arterial hypertension.

OBJECTIVES: To examine whether autoantibodies against bone morphogenetic protein receptor-II (BMPR-II) or activin receptor-like kinase 1 (ALK-1) are associated with pulmonary arterial hypertension (PAH) in patients with mixed connective tissue disease (MCTD). METHODS: We studied sera from 37 MCTD patients with or without PAH, six patients with idiopathic PAH, and 30 healthy controls. Circulating anti-BMPR-II and anti-ALK-1 antibodies were detected using immunoprecipitation of recombinant antigens generated by in vitro transcription/translation and indirect immunofluorescence of cultured cells that were induced to express these antigens by gene transfer. Anti-BMPR-II antibodies were further examined by immunoprecipitation and immunoblotting using a recombinant fragment of the extracellular domain of BMPR-II. RESULTS: Serum anti-BMPR-II and anti-ALK-1 autoantibodies were not detected in MCTD patients irrespective of the presence or absence of PAH, or in patients with idiopathic PAH. CONCLUSIONS: Our finding does not support the hypothesis that autoantibody-mediated dysregulation of signals through BMPR-II or ALK-1 contributes to the development of PAH in patients with connective tissue diseases.

Effect of Nma on growth inhibition by TGF-betaa in human gastric carcinoma cell lines.

Non-metastatic gene A (nma) has a homologue DNA sequence to a gene of bone morphogenetic proteins and activin membrane-bound inhibitor (BAMBI), which negatively regulates TGF-beta signaling. In this study, we analyzed the functional homology between Nma and BAMBI in human gastric carcinoma cell lines. Various levels of nma mRNA expression were detected by the RT-PCR technique in all human gastric carcinoma cell lines. Then, Nma antisense and sense S-oligodeoxynucleotide (ODN) were used to analyze the response of TGF-beta to cell growth and invasion gastric carcinoma cell lines. The cell growth was inhibited by TGF-beta in Nma antisense S-ODN treatment gastric carcinoma cell lines, MKN28, MKN1, MKN74 and TMK1. TGF-beta reduced cell growth and invasive activity of MKN28 treated with Nma antisense S-ODN in a dose and time-dependent manner. Furthermore, lysates of Nma sense or antisense S-ODN treated MKN28 cells were immunoprecipitated with anti-TGFbetaR-I or anti-TGFbetaR-II antibody. The 29 kDa signal considered as Nma appeared in sense S-ODN treated MKN28 cells immunoprecipitated with anti-TGFbetaR-I. These results indicate that Nma negatively regulates TGF-beta signaling, consequently playing an important role as one of the escape mechanisms from TGF-beta-mediated growth control similarly to BAMBI, and induce cell growth and invasion in human gastric carcinoma cell lines.