TLR Stimulation Produces IFN-ß as the Primary Driver of IFN Signaling in Nonlymphoid Primary Human Cells.

Several human autoimmune diseases are characterized by increased expression of type 1 IFN-stimulated genes in both the peripheral blood and tissue. The contributions of different type I IFNs to this gene signature are uncertain as the type I IFN family consists of 13 alphas and one each of ß, ε, κ, and ω subtypes. We sought to investigate the contribution of various IFNs to IFN signaling in primary human cell types. We stimulated primary skin, muscle, kidney, and PBMCs from normal healthy human donors with various TLR ligands and measured the expression of type I IFN subtypes and activation of downstream signaling by quantitative PCR. We show that IFNB1 is the dominant type I IFN expressed upon TLR3 and TLR4 stimulation, and its expression profile is associated with subsequent MX1 transcription. Furthermore, using an IFN-ß-specific neutralizing Ab, we show that MX1 expression is inhibited in a dose-dependent manner, suggesting that IFN-ß is the primary driver of IFN-stimulated genes following TLR3 and TLR4 engagement. Stimulation with TLR7/8 and TLR9 ligands induced IFNB1 and IFNA subtypes and MX1 expression only in PBMCs and not in tissue resident cell types. Concordantly, IFN-ß neutralization had no effect on MX1 expression in PBMCs potentially because of the combination of IFNB1 and IFNA expression. Combined, these data highlight the potential role for IFN-ß in driving local inflammatory responses in clinically relevant human tissue types and opportunities to treat local inflammation by targeting IFN-ß.

Discovery of PF-06928215 as a high affinity inhibitor of cGAS enabled by a novel fluorescence polarization assay.

Cyclic GMP-AMP synthase (cGAS) initiates the innate immune system in response to cytosolic dsDNA. After binding and activation from dsDNA, cGAS uses ATP and GTP to synthesize 2', 3' -cGAMP (cGAMP), a cyclic dinucleotide second messenger with mixed 2'-5' and 3'-5' phosphodiester bonds. Inappropriate stimulation of cGAS has been implicated in autoimmune disease such as systemic lupus erythematosus, thus inhibition of cGAS may be of therapeutic benefit in some diseases; however, the size and polarity of the cGAS active site makes it a challenging target for the development of conventional substrate-competitive inhibitors. We report here the development of a high affinity (KD = 200 nM) inhibitor from a low affinity fragment hit with supporting biochemical and structural data showing these molecules bind to the cGAS active site. We also report a new high throughput cGAS fluorescence polarization (FP)-based assay to enable the rapid identification and optimization of cGAS inhibitors. This FP assay uses Cy5-labelled cGAMP in combination with a novel high affinity monoclonal antibody that specifically recognizes cGAMP with no cross reactivity to cAMP, cGMP, ATP, or GTP. Given its role in the innate immune response, cGAS is a promising therapeutic target for autoinflammatory disease. Our results demonstrate its druggability, provide a high affinity tool compound, and establish a high throughput assay for the identification of next generation cGAS inhibitors.

SLIT2/ROBO2 signaling pathway inhibits nonmuscle myosin IIA activity and destabilizes kidney podocyte adhesion.

The repulsive guidance cue SLIT2 and its receptor ROBO2 are required for kidney development and podocyte foot process structure, but the SLIT2/ROBO2 signaling mechanism regulating podocyte function is not known. Here we report that a potentially novel signaling pathway consisting of SLIT/ROBO Rho GTPase activating protein 1 (SRGAP1) and nonmuscle myosin IIA (NMIIA) regulates podocyte adhesion downstream of ROBO2. We found that the myosin II regulatory light chain (MRLC), a subunit of NMIIA, interacts directly with SRGAP1 and forms a complex with ROBO2/SRGAP1/NMIIA in the presence of SLIT2. Immunostaining demonstrated that SRGAP1 is a podocyte protein and is colocalized with ROBO2 on the basal surface of podocytes. In addition, SLIT2 stimulation inhibits NMIIA activity, decreases focal adhesion formation, and reduces podocyte attachment to collagen. In vivo studies further showed that podocyte-specific knockout of Robo2 protects mice from hypertension-induced podocyte detachment and albuminuria and also partially rescues the podocyte-loss phenotype in Myh9 knockout mice. Thus, we have identified SLIT2/ROBO2/SRGAP1/NMIIA as a potentially novel signaling pathway in kidney podocytes, which may play a role in regulating podocyte adhesion and attachment. Our findings also suggest that SLIT2/ROBO2 signaling might be a therapeutic target for kidney diseases associated with podocyte detachment and loss.

Novel Anti-TM4SF1 Antibody-Drug Conjugates with Activity against Tumor Cells and Tumor Vasculature.

Antibody-drug conjugates (ADC) represent a promising therapeutic modality for managing cancer. Here, we report a novel humanized ADC that targets the tetraspanin-like protein TM4SF1. TM4SF1 is highly expressed on the plasma membranes of many human cancer cells and also on the endothelial cells lining tumor blood vessels. TM4SF1 is internalized upon interaction with antibodies. We hypothesized that an ADC against TM4SF1 would inhibit cancer growth directly by killing cancer cells and indirectly by attacking the tumor vasculature. We generated a humanized anti-human TM4SF1 monoclonal antibody, v1.10, and armed it with an auristatin cytotoxic agent LP2 (chemical name mc-3377). v1.10-LP2 selectively killed cultured human tumor cell lines and human endothelial cells that express TM4SF1. Acting as a single agent, v1.10-LP2 induced complete regression of several TM4SF1-expressing tumor xenografts in nude mice, including non-small cell lung cancer and pancreas, prostate, and colon cancers. As v1.10 did not react with mouse TM4SF1, it could not target the mouse tumor vasculature. Therefore, we generated a surrogate anti-mouse TM4SF1 antibody, 2A7A, and conjugated it to LP2. At 3 mpk, 2A7A-LP2 regressed several tumor xenografts without noticeable toxicity. Combination therapy with v1.10-LP2 and 2A7A-LP2 together was more effective than either ADC alone. These data provide proof-of-concept that TM4SF1-targeting ADCs have potential as anticancer agents with dual action against tumor cells and the tumor vasculature. Such agents could offer exceptional therapeutic value and warrant further investigation. Mol Cancer Ther; 14(8); 1868-76. ©2015 AACR.

Brown fat determination and development from muscle precursor cells by novel action of bone morphogenetic protein 6.

Brown adipose tissue (BAT) plays a pivotal role in promoting energy expenditure by the virtue of uncoupling protein-1 (UCP-1) that differentiates BAT from its energy storing white adipose tissue (WAT) counterpart. The clinical implication of "classical" BAT (originates from Myf5 positive myoblastic lineage) or the "beige" fat (originates through trans-differentiation of WAT) activation in improving metabolic parameters is now becoming apparent. However, the inducers and endogenous molecular determinants that govern the lineage commitment and differentiation of classical BAT remain obscure. We report here that in the absence of any forced gene expression, stimulation with bone morphogenetic protein 6 (BMP6) induces brown fat differentiation from skeletal muscle precursor cells of murine and human origins. Through a comprehensive transcriptional profiling approach, we have discovered that two days of BMP6 stimulation in C2C12 myoblast cells is sufficient to induce genes characteristic of brown preadipocytes. This developmental switch is modulated in part by newly identified regulators, Optineurin (Optn) and Cyclooxygenase-2 (Cox2). Furthermore, pathway analyses using the Causal Reasoning Engine (CRE) identified additional potential causal drivers of this BMP6 induced commitment switch. Subsequent analyses to decipher key pathway that facilitates terminal differentiation of these BMP6 primed cells identified a key role for Insulin Like Growth Factor-1 Receptor (IGF-1R). Collectively these data highlight a therapeutically innovative role for BMP6 by providing a means to enhance the amount of myogenic lineage derived brown fat.

Inhibition of NOTCH signaling by gamma secretase inhibitor engages the RB pathway and elicits cell cycle exit in T-cell acute lymphoblastic leukemia cells.

NOTCH signaling is deregulated in the majority of T-cell acute lymphoblastic leukemias (T-ALL) as a result of activating mutations in NOTCH1. Gamma secretase inhibitors (GSI) block proteolytic activation of NOTCH receptors and may provide a targeted therapy for T-ALL. We have investigated the mechanisms of GSI sensitivity across a panel of T-ALL cell lines, yielding an approach for patient stratification based on pathway activity and also providing a rational combination strategy for enhanced response to GSI. Whereas the NOTCH1 mutation status does not serve as a predictor of GSI sensitivity, a gene expression signature of NOTCH pathway activity does correlate with response, and may be useful in the selection of patients more likely to respond to GSI. Furthermore, inhibition of the NOTCH pathway activity signature correlates with the induction of the cyclin-dependent kinase inhibitors CDKN2D (p19(INK4d)) and CDKN1B (p27(Kip1)), leading to derepression of RB and subsequent exit from the cell cycle. Consistent with this evidence of cell cycle exit, short-term exposure of GSI resulted in sustained molecular and phenotypic effects after withdrawal of the compound. Combination treatment with GSI and a small molecule inhibitor of CDK4 produced synergistic growth inhibition, providing evidence that GSI engagement of the CDK4/RB pathway is an important mechanism of GSI action and supports further investigation of this combination for improved efficacy in treating T-ALL.

Brain tumor oncolysis with replication-conditional herpes simplex virus type 1 expressing the prodrug-activating genes, CYP2B1 and secreted human intestinal carboxylesterase, in combination with cyclophosphamide and irinotecan.

The treatment of malignant glioma is currently ineffective. Oncolytic viruses are being explored as a means to selectively lyse tumor cells in the brain. We have engineered a mutant herpes simplex virus type 1 with deletions in the viral UL39 and gamma(1)34.5 genes and an insertion of the two prodrug activating genes, CYP2B1 and secreted human intestinal carboxylesterase. Each of these can convert the inactive prodrugs, cyclophosphamide and irinotecan (CPT-11), into their active metabolites, respectively. This new oncolytic virus (MGH2) displays increased antitumor efficacy against human glioma cells both in vitro and in vivo when combined with cyclophosphamide and CPT-11. Importantly, cyclophosphamide, CPT-11, or the combination of cyclophosphamide and CPT-11 does not significantly affect oncolytic virus replication. Therefore, MGH2 provides effective multimodal therapy for gliomas in preclinical models when combined with these chemotherapy agents.

PTEN decreases in vivo vascularization of experimental gliomas in spite of proangiogenic stimuli.

Approximately 30-40% of malignant glial tumors exhibit mutations in the tumor suppressor gene, PTEN/MMAC. Additionally, these tumors are associated with (a) mutations in epidermal growth factor receptor (EGFR), leading to a pro-oncogenic constitutive activation, as well as amplification of its gene, and/or (b) mutations in p53, disrupting normal cellular homeostatic processes. Whereas PTEN/MMAC has been shown to possess antiangiogenic action, constitutively active EGFR or p53 gene defects have been associated with proangiogenic action. In this article, we asked if PTEN/MMAC gene transfer into human glioma cells that possess inactivating mutations of the PTEN/MMAC gene but also express either constitutively active EGFR (U87DeltaEGFR cells) or possess an inactivating mutation of p53 (U251 cells) still display inhibited angiogenesis in orthotopic and ectopic models of gliomas. Human glioma xenografts treated with PTEN/MMAC gene transfer exhibited significantly decreased vascularity both in an orthotopic and in an ectopic model. Taken in combination, these results provide strong evidence of PTEN/MMAC's role in regulating glioma angiogenesis even in the presence of strong proangiogenic signals provided by constitutive EGFR activation or p53 inactivation.

MRI of transgene expression: correlation to therapeutic gene expression.

Magnetic resonance imaging (MRI) can provide high-resolution 3D maps of structural and functional information, yet its use of mapping in vivo gene expression has only recently been explored. A potential application for this technology is to noninvasively image transgene expression. The current study explores the latter using a nonregulatable internalizing engineered transferrin receptor (ETR) whose expression can be probed for with a superparamagnetic Tf-CLIO probe. Using an HSV-based amplicon vector system for transgene delivery, we demonstrate that: 1) ETR is a sensitive MR marker gene; 2) several transgenes can be efficiently expressed from a single amplicon; 3) expression of each transgene results in functional gene product; and 4) ETR gene expression correlates with expression of therapeutic genes when the latter are contained within the same amplicon. These data, taken together, suggest that MRI of ETR expression can serve as a surrogate for measuring therapeutic transgene expression.