Inhibitory Fc-Gamma IIb Receptor Signaling Induced by Multivalent IgG-Fc Is Dependent on Sialylation

Immunoglobulin (IgG) Fc glycosylation has been shown to be important for the biological activity of antibodies. Fc sialylation is important for the anti-inflammatory activity of IgGs. However, evaluating the structure-activity relationship (SAR) of antibody Fc glycosylation has been hindered using simplified in vitro models in which antibodies are often displayed in monomeric forms. Presenting antibodies in monomeric forms may not accurately replicate the natural environment of the antibodies when binding their antigen in vivo. To address these limitations, we used different Fc-containing molecules, displaying their Fc domains in monovalent and multivalent fashion. Given the inhibitory role of Fc gamma receptor IIb (FcγRIIb) in autoimmune and inflammatory diseases, we focused on evaluating the impact of Fc sialylation on the activation of FcγRIIb. We report for the first time that in human cellular systems, sialic acid mediates the induction of FcγRIIb phosphorylation by IgG-Fc when the IgG-Fc is displayed in a multivalent fashion. This effect was observed with different types of therapeutic agents such as sialylated anti-TNFα antibodies, sialylated IVIg and sialylated recombinant multivalent Fc products. These studies represent the first report of the specific effects of Fc sialylation on FcγRIIb signaling on human immune cells and may help in the characterization of the anti-inflammatory activity of Fc-containing therapeutic candidates.

Multiomic study of skin, peripheral blood, and serum: is serum proteome a reflection of disease process at the end-organ level in systemic sclerosis?

BACKGROUND

Serum proteins can be readily assessed during routine clinical care. However, it is unclear to what extent serum proteins reflect the molecular dysregulations of peripheral blood cells (PBCs) or affected end-organs in systemic sclerosis (SSc). We conducted a multiomic comparative analysis of SSc serum profile, PBC, and skin gene expression in concurrently collected samples.

METHODS

Global gene expression profiling was carried out in skin and PBC samples obtained from 49 SSc patients enrolled in the GENISOS observational cohort and 25 unaffected controls. Levels of 911 proteins were determined by Olink Proximity Extension Assay in concurrently collected serum samples.

RESULTS

Both SSc PBC and skin transcriptomes showed a prominent type I interferon signature. The examination of SSc serum profile revealed an upregulation of proteins involved in pro-fibrotic homing and extravasation, as well as extracellular matrix components/modulators. Notably, several soluble receptor proteins such as EGFR, ERBB2, ERBB3, VEGFR2, TGFBR3, and PDGF-Rα were downregulated. Thirty-nine proteins correlated with severity of SSc skin disease. The differential expression of serum protein in SSc vs. control comparison significantly correlated with the differential expression of corresponding transcripts in skin but not in PBCs. Moreover, the differentially expressed serum proteins were significantly more connected to the Well-Associated-Proteins in the skin than PBC gene expression dataset. The assessment of the concordance of between-sample similarities revealed that the molecular profile of serum proteins and skin gene expression data were significantly concordant in patients with SSc but not in healthy controls.

CONCLUSIONS

SSc serum protein profile shows an upregulation of profibrotic cytokines and a downregulation of soluble EGF and other key receptors. Our multilevel comparative analysis indicates that the serum protein profile in SSc correlates more closely with molecular dysregulations of skin than PBCs and might serve as a reflection of disease severity at the end-organ level.

Enhancing reproducibility of gene expression analysis with known protein functional relationships: The concept of well-associated protein

Identification of differentially expressed genes (DEGs) is well recognized to be variable across independent replications of genome-wide transcriptional studies. These are often employed to characterize disease state early in the process of discovery and prioritize novel targets aimed at addressing unmet medical need. Increasing reproducibility of biological findings from these studies could potentially positively impact the success rate of new clinical interventions. This work demonstrates that statistically sound combination of gene expression data with prior knowledge about biology in the form of large protein interaction networks can yield quantitatively more reproducible observations from studies characterizing human disease. The novel concept of Well-Associated Proteins (WAPs) introduced herein-gene products significantly associated on protein interaction networks with the differences in transcript levels between control and disease-does not require choosing a differential expression threshold and can be computed efficiently enough to enable false discovery rate estimation via permutation. Reproducibility of WAPs is shown to be on average superior to that of DEGs under easily-quantifiable conditions suggesting that they can yield a significantly more robust description of disease. Enhanced reproducibility of WAPs versus DEGs is first demonstrated with four independent data sets focused on systemic sclerosis. This finding is then validated over thousands of pairs of data sets obtained by random partitions of large studies in several other diseases. Conditions that individual data sets must satisfy to yield robust WAP scores are examined. Reproducible identification of WAPs can potentially benefit drug target selection and precision medicine studies.

Elucidating the interplay between IgG-Fc valency and FcγR activation for the design of immune complex inhibitors

Autoantibody immune complex (IC) activation of Fcγ receptors (FcγRs) is a common pathogenic hallmark of multiple autoimmune diseases. Given that the IC structural features that elicit FcγR activation are poorly understood and the FcγR system is highly complex, few therapeutics can directly block these processes without inadvertently activating the FcγR system. To address these issues, the structure activity relationships of an engineered panel of multivalent Fc constructs were evaluated using sensitive FcγR binding and signaling cellular assays. These studies identified an Fc valency with avid binding to FcγRs but without activation of immune cell effector functions. These observations directed the design of a potent trivalent immunoglobulin G-Fc molecule that broadly inhibited IC-driven processes in a variety of immune cells expressing FcγRs. The Fc trimer, Fc3Y, was highly efficacious in three different animal models of autoimmune diseases. This recombinant molecule may represent an effective therapeutic candidate for FcγR-mediated autoimmune diseases.

Neutrophil Elastase-Generated Fragment of Vascular Endothelial Growth Factor-A Stimulates Macrophage and Endothelial Progenitor Cell Migration

Elastase released from neutrophils as part of the innate immune system has been implicated in chronic diseases such as emphysema and cardiovascular disease. We have previously shown that neutrophil elastase targets vascular endothelial growth factor-A (VEGF) for partial degradation to generate a fragment of VEGF (VEGFf) that has distinct activities. Namely, VEGFf binds to VEGF receptor 1 but not to VEGF receptor 2 and shows altered signaling compared to intact VEGF. In the present study we investigated the chemotactic function of VEGF and VEGFf released from cells by neutrophil elastase. We found that endothelial cells migrated in response to intact VEGF but not VEGFf whereas RAW 264.7 macrophages/monocytes and embryonic endothelial progenitor cells were stimulated to migrate by either VEGF or VEGFf. To investigate the role of elastase-mediated release of VEGF from cells/extracellular matrices, a co-culture system was established. High or low VEGF producing cells were co-cultured with macrophages, endothelial or endothelial progenitor cells and treated with neutrophil elastase. Elastase treatment stimulated macrophage and endothelial progenitor cell migration with the response being greater with the high VEGF expressing cells. However, elastase treatment led to decreased endothelial cell migration due to VEGF cleavage to VEGF fragment. These findings suggest that the tissue response to NE-mediated injury might involve the generation of diffusible VEGF fragments that stimulate inflammatory cell recruitment.

The effect and mechanism of M402 on gemcitabine uptake into pancreatic tumors

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Background: Pancreatic ductal adenocarcinoma (PDAC) is characterized by extensive desmoplasia, which has been attributed to high interstitial pressure and poor drug delivery. In nonclinical studies, M402 affected multiple growth factors, adhesion molecules, and chemokines, inhibiting tumor progression, metastasis, and angiogenesis by clearing heparin-binding factors from the tumor microenvironment. We hypothesized that M402 could modulate tumor-stroma interactions in an orthotopic pancreatic cancer model (rich in desmoplasia), decreasing the fibrotic response and in turn increasing tumor perfusion and drug delivery. Methods: Capan-2 human PDAC cells were injected into the pancreata of nude mice. M402 (40 mg/kg/day, s.c.) or saline began Week 5. Gemcitabine (GEM; 30 mg/kg, i.p. biweekly) started Week 7. At different time points, primary tumors were analyzed for mRNA arrays, immunohistochemistry (ECM components, CD31), and functional tumor vasculature. GEM tumor uptake was evaluated by quantifying the incorporation of dFdC into tumor DNA by LC-MS/MS. M402 tumor uptake was visualized using HyLite-750-labeled drug in a Xenogen system. Results: M402 readily targeted pancreatic tumors with long residence time. Alone and particularly in combination with GEM, M402 significantly reduced tumor size and fibrosis, which was accompanied by down-regulation of SHH, PDGF, and TGF-β signaling in stromal cells. Tumors treated with M402 or M402+GEM showed perfusion and microvessel penetration into the tumor centers while vehicle or GEM treated tumors exhibited limited tortuous vessels surrounding the tumor rim. This translated into increased GEM incorporation into the tumor DNA when mice were pre-treated with M402 vs. saline (10.9±5.5 vs. 6.7±1.8 pg of dFdC/µg dG, respectively; p=0.037). Conclusions: M402 appears to inhibit stromal activation within the tumor microenvironment. Reduction in desmoplasia led to improved tumor perfusion, delivery of GEM, and tumor shrinkage. These and other promising nonclinical data support the rationale for the ongoing Phase 1/2 study evaluating the safety and tolerability of M402 in combination with nab-paclitaxel and GEM in patients with metastatic pancreatic cancer.

Abstract 302: Characterization of effects of M402 on EMT in pancreatic ductal adenocarcinoma

Background: Pancreatic ductal adenocarcinoma (PDA) is an almost uniformly lethal disease. The current treatment for resectable disease consists of surgery and adjuvant gemcitabine therapy. However, for more than 80 percent of the patients with PDA surgery is not an option. For these patients palliative chemotherapy using gemcitabine, or most recently FOLFIRINOX, is considered standard of care. Even with palliative chemotherapy the median overall survival for patients with metastatic PDA is dismal and improved therapeutic strategies are a clear unmet medical need. Heparins may be of interest for the treatment of PDA. They play an important role in tumor progression and metastasis by binding at heparin binding domains, thereby preventing growth factor gradients created along proteoglycan heparan sulfates and thus disrupting signaling. We used a novel heparan sulfate mimetic, M402, which binds to multiple growth factors, adhesion molecules, and chemokines. We previously showed that M402 decreases both epithelial-to-mesynchymal transition and chemotherapy resistance in PDA. Here we further evaluated the underlying mechanisms of M402 in EMT.

Results: We studied the effects of M402 on PDA using a genetically engineered mouse model (GEMM) for PDA (LSL-KRASG12D/+; Trp53 LSL-R172H/flox; pdx-CRE), which recapitulates human PDA. Combination therapy of M402 with gemcitabine significantly prolonged the average survival of the mice when compared to mice treated with gemcitabine monotherapy (87 days versus 78 days) and significantly reduced metastasis and local invasion into the small intestine. These data suggest an effect of M402 on invasiveness and EMT. Gemcitabine treatment increased EMT as determined by staining for E-cadherin and Fsp1 double positive cells. In contrast, M402 treatment resulted in a decrease in E-cadherin and Fsp1 double positive cells in pancreatic tumors. We next sought to determine whether M402 affects cancer cells or stromal cells. In vitro experiments show that cell lines derived from our model respond to M402 by decreasing their invasive behavior in 3D culture and scratch assays. Moreover, we found that M402 augments the gemcitabine effect in vitro. These data suggest that M402 affects both EMT and gemcitabine response. Further identification by whole transcriptome microarray analysis of treated tumors hints towards a role of M402 in affecting multiple signaling pathways involved in the regulation of EMT. These data will undoubtedly lead to better insight into the mechanism of action of M402 and will increase our understanding of the pathways PDA cells use to evade the effects of chemotherapy. M402 is currently being investigated in a phase 1/2 M402 gemcitabine combination study to assess if these findings can be translated into a clinical benefit in pancreatic cancer patients.

Conclusion: These data suggest that M402 reduces acquired chemotherapy resistance in a GEMM for PDA by decreasing EMT.

Citation Format: Ilse Oosterom, Birgit C. Schultes, Chia Lin Chu, Zoya Galcheva-Gargova, Elma Kurtagic, He Zhou, Jay Duffner, Emile E. Voest, David A. Tuveson, Martijn Lolkema. Characterization of effects of M402 on EMT in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 302. doi:10.1158/1538-7445.AM2013-302

M402, a heparan sulfate mimetic and novel candidate for the treatment of pancreatic cancer

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Background: Recent advances in pancreatic cancer research implicate the involvement of several heparin-binding growth factors (such as HGF, HB-EGF, PDGF, hedgehogs, and TGFs) that control tumor-stroma interactions. We have rationally designed a heparan sulfate mimetic, M402, which has been previously shown to affect tumor progression and metastasis through disruption of multiple pathways. We hypothesized that M402 could modulate tumor-stroma interactions and enhance the efficacy of gemcitabine, and evaluated its efficacy in two preclinical models. Methods: A genetically engineered mouse model (GEMM; KrasLSLG12D p53LSLR172H) featuring spontaneous pancreatic tumor formation and metastasis assessed M402’s effect on tumorigenesis and metastasis. The orthotopic Capan-2 model in nude mice evaluated the effect of M402 on desmoplasia, a fibrotic response that hinders effective delivery of chemotherapeutics, via inhibition of sonic hedgehog (SHH) signaling in fibroblasts and stellate cells. In both models, M402 was studied as monotherapy and with gemcitabine. Results: In the GEMM, M402 significantly prolonged survival in combination with gemcitabine while each monotherapy showed modest efficacy. M402, alone and in combination, also reduced metastases and local invasion and inhibited epithelial-to-mesenchymal transition. In the Capan-2 model, gemcitabine was increasingly less effective as desmoplasia progressed over time. The addition of M402 to gemcitabine increased its efficacy with respect to primary tumor burden. Metastasis, invasion, and surrounding fibrotic lesions appeared particularly impacted by the combination treatment. M402 was also effective as monotherapy with dose-dependency, which correlated with reduced SHH signaling. Conclusions: M402 can modulate tumor-stroma interactions involved in the metastatic and desmoplastic pathways in two pancreatic cancer models supporting the translation of these findings into a clinical study. A first-in-human study is planned that will evaluate the safety, pharmacokinetics, efficacy, and biomarker profiles of escalating M402 doses in combination with gemcitabine in patients with metastatic pancreatic cancer.

Complex receptor-ligand dynamics control the response of the VEGF system to protease injury

BACKGROUND

Vascular homeostasis and response to injury are dependent on the coordinated activity of growth factors such as vascular endothelial growth factor-A (VEGF). VEGF signaling is mediated by VEGF receptors 1 (VEGFR1) and 2 (VEGFR2). VEGF also binds to extracellular matrix (ECM) and neuropilin (NP), a cell surface glycoprotein that enhances VEGF binding to VEGFR2 while inhibiting VEGF-VEGFR1 interactions. Proteases such as neutrophil elastase release VEGF bound to ECM; however, this results in proteolytic processing of VEGF to a smaller species termed VEGF fragment (VEGFf). We hypothesized that the generation and presence of VEGFf would have significant effects on the binding distribution of VEGF.

RESULTS

We show that VEGFf, unlike VEGF, does not bind ECM, fibronectin, or NP-1. Using computational simulations, we find that excess VEGFf can lead to increased binding of VEGF to VEGFR2 through VEGFf binding to VEGFR1 and subsequent liberation of NP-1. We show experimentally that VEGF-induced migration has a biphasic response to conversion of VEGF to VEGFf. Simulations suggest that a simple change in VEGFR1 or VEGFR2 complexes are unlikely to be responsible and that a more complex integration of signals is more likely involved.

CONCLUSIONS

These findings suggest that proteolytic damage at sites of tissue injury and inflammation has the potential to modulate the VEGF system through a complex process and highlight the need for quantitative analysis to reveal mechanisms of growth factor control.

Engineered bivalent ligands to bias ErbB receptor-mediated signaling and phenotypes

The ErbB receptor family is dysregulated in many cancers, and its therapeutic manipulation by targeted antibodies and kinase inhibitors has resulted in effective chemotherapies. However, many malignancies remain refractory to current interventions. We describe a new approach that directs ErbB receptor interactions, resulting in biased signaling and phenotypes. Due to known receptor-ligand affinities and the necessity of ErbB receptors to dimerize to signal, bivalent ligands, formed by the synthetic linkage of two neuregulin-1β (NRG) moieties, two epidermal growth factor (EGF) moieties, or an EGF and a NRG moiety, can potentially drive homotypic receptor interactions and diminish formation of HER2-containing heterodimers, which are implicated in many malignancies and are a prevalent outcome of stimulation by native, monovalent EGF, or NRG. We demonstrate the therapeutic potential of this approach by showing that bivalent NRG (NN) can bias signaling in HER3-expressing cancer cells, resulting in some cases in decreased migration, inhibited proliferation, and increased apoptosis, whereas native NRG stimulation increased the malignant potential of the same cells. Hence, this new approach may have therapeutic relevance in ovarian, breast, lung, and other cancers in which HER3 has been implicated.

Neutrophil elastase cleaves VEGF to generate a VEGF fragment with altered activity

Excessive neutrophil elastase (NE) activity and altered vascular endothelial growth factor (VEGF) signaling have independently been implicated in the development and progression of pulmonary emphysema. In the present study, we investigated the potential link between NE and VEGF. We noted that VEGF(165) is a substrate for NE. Digestion of purified VEGF(165) with NE generated a partially degraded disulfide-linked fragment of VEGF. Mass spectrometric analysis revealed that NE likely cleaves VEGF(165) at both the NH(2) and COOH termini to produce VEGF fragment chains approximately 5 kDa reduced in size. NE treatment of VEGF-laden endothelial cell cultures and smooth muscle cells endogenously expressing VEGF generated VEGF fragments similar to those observed with purified VEGF(165). NE-generated VEGF fragment showed significantly reduced binding to VEGF receptor 2 and heparin yet retained the ability to bind to VEGF receptor 1. Interestingly, VEGF fragment showed altered signaling in pulmonary artery endothelial cells compared with intact VEGF(165). Specifically, treatment with VEGF fragment did not activate extracellular-regulated kinases 1 and 2 (ERK1/2), yet resulted in enhanced activation of protein kinase B (Akt). Treatment of monocyte/macrophage RAW 264.7 cells with VEGF fragment, on the other hand, led to both Akt and ERK1/2 activation, increased VEGFR1 expression, and stimulated chemotaxis. These findings suggest that the tissue response to NE-mediated injury might involve the generation of diffusible VEGF fragments that stimulate inflammatory cell recruitment and activation via VEGF receptor 1.