Precision-activated T-cell engagers targeting HER2 or EGFR and CD3 mitigate on-target, off-tumor toxicity for immunotherapy in solid tumors

To enhance the therapeutic index of T-cell engagers (TCEs), we engineered masked, precision-activated TCEs (XPAT proteins), targeting a tumor antigen (human epidermal growth factor receptor 2 (HER2) or epidermal growth factor receptor (EGFR)) and CD3. Unstructured XTEN polypeptide masks flank the N and C termini of the TCE and are designed to be released by proteases in the tumor microenvironment. In vitro, unmasked HER2-XPAT (uTCE) demonstrates potent cytotoxicity, with XTEN polypeptide masking providing up to 4-log-fold protection. In vivo, HER2-XPAT protein induces protease-dependent antitumor activity and is proteolytically stable in healthy tissues. In non-human primates, HER2-XPAT protein demonstrates a strong safety margin (>400-fold increase in tolerated maximum concentration versus uTCE). HER2-XPAT protein cleavage is low and similar in plasma samples from healthy and diseased humans and non-human primates, supporting translatability of stability to patients. EGFR-XPAT protein confirmed the utility of XPAT technology for tumor targets more widely expressed in healthy tissues.

Abstract P193: AMX-818, a novel prodrug HER2-XPAT T-cell engager (TCE) with potent T cell activation, proteolytic cleavage and efficacy in xenograft tumors, and wide safety margins in NHP (Non Human Primate)

Background: TCEs are effective in leukemias, but have been limited in solid tumors due to on-target, off-tumor toxicity. Attempts to circumvent cytokine release syndrome (CRS), including step-up dosing and complex designs, have had limited success due to toxicity and immunogenicity. AMX-818, HER2-XPAT, or XTENylated Protease-Activated T Cell Engager, is a prodrug TCE that exploits dysregulated protease activity present in tumors to expand the therapeutic index (TI). The core of the molecule (PAT) consists of 2 tandem scFvs targeting CD3 and HER2. Attached to the core are two unstructured polypeptides (XTEN) that function as universal masks, sterically reduce target engagement and extend T1/2. Protease cleavage sites at the base of the XTEN masks enable proteolytic activation of XPATs in the tumor microenvironment, releasing a potent TCE with short T1/2. Methods: Nonclinical studies were conducted with HER2-XPAT or AMX-818, unmasked HER2-PAT, HER2-NoClvSite (no protease linkers) or the fluorescent labeled counterparts in vitro and in vivo xenografts and NHP. Results: The unmasked HER2-PAT demonstrated potent in vitro T cell cytotoxicity (EC50 1-2pM), target-dependent T cell activation and cytokine production by hPBMCs (human mononuclear cells). HER2-XPAT demonstrated 14,000-fold protection against killing of HER2 tumor cells, and minimal cytotoxicity against cardiomyocytes up to 1uM. In vivo, HER2-XPAT or AMX-818 induced complete tumor regressions (CRs) in HER2+ BT-474 tumors (similar to effect with equimolar doses of HER2-PAT), whereas HER2-NoClvSite lacked efficacy, supporting the need for protease cleavage for activity. HER2-XPAT was also highly efficacious in the HER2 low-expressing HT-55 colorectal model. Labeled XPATs with the same protease cleavage sites in 9 different in vivo xenograft and PDX models demonstrated preferential unmasking into cleaved products in tumors in contrast to healthy organs, with average ~20% of drug in tumor cleaved to the fully active TCE form. In NHPs, AMX-818 caused early T-cell margination as low as 2mg/kg, but has been dose-escalated safely up to 42mg/kg (MTD) with no CRS. Doses of 0.5 to 42 mg/kg demonstrated dose proportional increases in HER2-XPAT exposure, with low to negligible levels of cleavage products present in systemic circulation. Continuous infusion of unmasked HER2-PAT induced lethal CRS and cytokine spikes at 0.3mg/kg/d but was tolerated at 0.2 mg/kg/d, providing AMX-818 with ~450-fold improvement in safety compared to HER2-PAT. Repeat-dose GLP toxicology studies have demonstrated that the highest dose evaluated (6 mg/kg) was the NOAEL, suggesting that HER2-XPAT has a wide TI based on predicted human PK and predicted efficacious exposures. Conclusions: AMX-818 is a potent, protease-activated prodrug TCE exhibiting preferential tumor unmasking, with minimal systemic unmasking and no CRS at high doses in NHP. AMX-818 represents a promising solution to widen the TI for TCE activity in HER2-high and HER2-low expressing tumors.

Citation Format: Milton To, Pete Yeung, Michael Fox, Mikhail Hammond, Fiore Cattaruzza, Ayesha Nazeer, Caitlin Koski, Lucas Liu, Sina Khorsand, Deena Rennerfeldt, Kari Morrissey, Zachary Lange, Ming Dong, Sharon Lam, Mika K. Derynck, Bryan A. Irving, Volker Schellenberger. AMX-818, a novel prodrug HER2-XPAT T-cell engager (TCE) with potent T cell activation, proteolytic cleavage and efficacy in xenograft tumors, and wide safety margins in NHP (Non Human Primate) [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P193.

Abstract 1824: HER2-XPAT, a novel protease-activatable T-cell engager (TCE) with potent T-cell activation and efficacy in solid tumors and large safety margins in non-human primate (NHP)

Background: TCEs are effective in leukemias but have been challenging in solid tumors due to on-target, off-tumor toxicity. Attempts to circumvent cytokine release syndrome (CRS) including step-up dosing and/or complex molecular designs have been unsuccessful due to toxicity and/or enhanced immunogenicity. HER2-XPAT, or XTENylated Protease-Activated bispecific T-Cell Engager, is a prodrug TCE that exploits the protease activity present in tumors vs healthy tissue to expand the therapeutic index (TI). The core of the HER2-XPAT (PAT) consists of 2 tandem scFvs targeting CD3 and HER2. Attached to the core, two unstructured polypeptide masks (XTEN) sterically reduce target engagement and extend T1/2. Protease cleavage sites at the base of the XTEN masks enable proteolytic activation of XPATs in the tumor microenvironment, unleashing a potent TCE with short T1/2, further improving the TI.

Methods: Preclinical studies were conducted to characterize the activity of HER2-XPAT, HER2-PAT (cleaved XPAT), and HER2-NonClv (a non-cleavable XPAT) for cytotoxicity in vitro, anti-tumor efficacy and cleavage in xenograft models, stability in human plasma, and safety in NHPs.

Results: The unmasked HER2-PAT demonstrated potent in vitro T-cell cytotoxicity (EC50 1-2pM) and target-dependent T-cell activation and cytokine production by hPBMCs. HER2-XPAT provided up to 14,000-fold protection against killing of HER2 tumor cells and exhibited only minimal cytotoxicity against cardiomyocytes at 1μM. In vivo, HER2-XPAT induced complete tumor regressions (CRs) in BT-474 tumors with equimolar dosing as HER2-PAT, whereas HER2-NonClv lacked efficacy, supporting a requirement of protease cleavage. HER2-XPAT was also highly efficacious in the HER2 low-expressing HT-55 colorectal model. Preferential proteolytic cleavage of fluorescent-labeled HER2-XPAT in tumors vs healthy organs was demonstrated in vivo. In NHP, HER2-XPAT has been dose-escalated safely up to 42mg/kg (MTD). HER2-XPAT demonstrated early T-cell margination at 2mg/kg but largely spared CRS, cytokines, and major tissue toxicity up to 42mg/kg. In vivo, the PK of HER2-XPAT was comparable to its non-cleavable counterpart, consistent with its ex vivo stability for cleavage in cancer pts plasma for 7 days at 37°C. Continuous infusion of HER2-PAT induced lethal CRS and cytokine spikes at 0.3mg/kg/d but was tolerated at 0.25mg/kg/d, providing HER2-XPAT with 500-fold protection in tolerated Cmax vs HER2-PAT.

Conclusions: HER2-XPAT is a potent, prodrug TCE exhibiting protease-dependent tumor efficacy in mouse xenografts and a wide TI with no CRS in NHPs. XTEN's low immunogenicity has already been demonstrated in humans (growth hormone and FVIII). HER2-XPAT represents a promising solution for HER2-high tumors with potential expansion to HER2 low expressing tumors. IND studies are ongoing.

Citation Format: Fiore Cattaruzza, Ayesha Nazeer, Zachary Lange, Caitlin Koski, Mikhail Hammond, Milton To, Pete Yeung, Sharon Lam, Mika K. Derynck, Bryan Irving, Volker Schellenberger. HER2-XPAT, a novel protease-activatable T-cell engager (TCE) with potent T-cell activation and efficacy in solid tumors and large safety margins in non-human primate (NHP) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1824.

Abstract PS17-11: Her2-xpat, a novel protease-activatable prodrug t-cell engager (tce), exhibits potent t-cell activation and efficacy in her2 tumors, yielding large predicted safety margins based on non-human primate (nhp)

Background

TCEs are effective at inducing remissions in hematologic cancers but have been challenging in solid tumors due to on-target, off-tumor toxicity. Attempts to circumvent CRS include fractionated or step-up dosing and/or complex molecular designs, but these have been unsuccessful due to toxicity and/or enhanced immunogenicity. Amunix has developed a conditionally active TCE, XPAT or XTENylated Protease-Activated bispecific T-Cell Engager, that exploits the protease activity present in tumors vs. healthy tissue to expand the therapeutic index (TI). The core of the HER2-XPAT (PAT) consists of 2 tandem scFVs targeting CD3 and HER2. Two unstructured polypeptide masks (XTEN) are attached to the core that sterically reduce target engagement and extend T1/2. Protease cleavage sites at the base of the XTEN masks enable proteolytic activation of XPATs in the tumor microenvironment, unleashing a highly potent TCE with a short T1/2 and further improving the TI. Although checkpoint inhibitors have been ineffective in HER2+ or HR+ breast cancer, TCEs can co-opt T-cells regardless of their antigenic specificity, providing the potential to introduce effective T-cell immunity against tumors expressing HER2. HER2-XPAT, as a tumor protease-activatable prodrug with a wide safety margin, offers the potential to induce effective T-cell cytotoxicity against HER2hi tumors and HR+/HER2 1-2+ tumors.

Methods

Preclinical studies were conducted to characterize the activity of HER2-XPAT, HER2-PAT (cleaved XPAT), and HER2-NonClv (a non-cleavable XPAT) for cytolytic activity in vitro, for anti-tumor efficacy in xenograft models, and for stability and safety in NHPs.

Results

HER2-PAT (cleaved XPAT) demonstrated potent in vitro tumor-directed T-cell cytotoxicity (EC50 1-2pM) and target-dependent T-cell activation and production of cytokines by PBMCs. HER2-PAT also exhibited cytotoxicity in HR+, HER2 1+ MCF7s at higher doses (EC50 0.13nM). HER2-XPAT provided up to 14,000-fold protection against killing of HER2 tumor cells and exhibited no cytotoxicity against cardiomyocytes at concentrations up to 1uM. In vivo, HER2-XPAT induced complete tumor regressions in BT-474 tumor models with equimolar dosing to HER2-PAT, whereas non-cleavable HER2-NonClv had no efficacy, supporting tumor protease cleavage requirement for T-cell activity. In NHP, HER2-XPAT has been dose-escalated safely up to 42mg/kg (MTD) but was not tolerated at 50mg/kg. HER2-XPAT demonstrated early T-cell margination at 2mg/kg but largely spared CRS, cytokine production, and tissue toxicity at doses up to 42mg/kg. PK profiles of HER2-XPAT and HER2-NonClv were comparable in NHP, indicating minimal systemic cleavage of XPAT, consistent with its ex vivo stability when incubated in the plasma of cancer pts for 7 days at 37°C. Given by continuous infusion, HER2-PAT induced lethal CRS and cytokine spikes at 0.3mg/kg/d, but was tolerated at 0.2mg/kg/d, providing HER2-XPAT with >3000-fold protection in tolerated Cmax versus HER2-PAT, >4 logs over cytotoxicity EC50s for HER2 and HR+ cell lines, and a 20-fold margin of safety over the dose required for pharmacodynamic activity.

Conclusions

HER2-XPAT is a potent prodrug T-cell engager with promising evidence of activity at low doses while exhibiting minimal CRS and a potentially wide TI based on NHP tolerability at doses up to 42mg/kg. With XTEN’s prior clinical data demonstrating low immunogenicity, the XPAT TCEs provide a promising solution. IND studies are currently ongoing. Additional PK, PD, cytokines, safety, and efficacy data will be presented.

Citation Format: Fiore Cattaruzza, Ayesha Nazeer, Zachary Lange, Caitlin Koski, Mikhail Hammond, Angela Henkensiefken, Trang Dao-Pick, Mika K Derynck, Bryan Irving, Volker Schellenberger. Her2-xpat, a novel protease-activatable prodrug t-cell engager (tce), exhibits potent t-cell activation and efficacy in her2 tumors, yielding large predicted safety margins based on non-human primate (nhp) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-11.

Abstract 3376: HER2-XPAT and EGFR-XPAT: Pro-drug T-cell engagers (TCEs) engineered to address on-target, off-tumor toxicity with potent efficacy in vitro and in vivo and large safety margins in NHP

Background: TCEs have proven to be effective in creating durable remissions in hematologic malignancies but have been challenging in solid tumors due to on-target, off-tumor toxicity. To circumvent the toxicity, many have tried step-up, fractionated dosing or complex formats, but these have largely been unsuccessful due to toxicity and/or enhanced immunogenicity. To address this challenge, Amunix has developed a conditionally active TCE, the XPAT or XTENylated Protease-Activated T Cell Engager, that exploits the protease activity present in tumors vs. healthy tissue, enabling expansion of the therapeutic index (TI). The core of the XPAT consists of 2 tandem scFVs targeting CD3 and a tumor antigen. Two unstructured and modular polypeptide masks (XTEN) are attached to the core that sterically reduce target engagement and extend T1/2. Protease cleavage sites at the base of these XTEN polypeptide masks are then proteolytically released in the tumor microenvironment to unleash a highly potent TCE with a short T1/2, further improving the TI.

Methods: HER2-XPAT and EGFR-XPATs were each purified from E.coli expressed from a single plasmid. The activity of both the prodrugs (XPATs) and their protease-activated counterparts (PATs) were characterized for cytotoxicity in vitro and in huPBMC-transduced tumor-bearing mice. Pilot toxicity studies were conducted in NHPs (cyno).

Results: Both protease-activated (PATs) forms of EGFR-XPAT and HER2-XPAT demonstrated potent in vitro T cell directed cytotoxicity against tumor cells (EC50s 1-2pM), while the masked XPAT provided 3,000-14,000-fold protection against target cell killing. Intact EGFR-XPAT demonstrated dose-dependent complete tumor responses (CRs) in HT-29 CRC xenografts, with HER2-XPAT demonstrating similar efficacy and CRs in both BT-474 and SK-OV-3 tumors. In cynos, 1 mg/kg of EGFR-XPAT was the MTD and 1.5 mg/kg exceeded the MTD, while the activated PAT was lethal at 0.132mg/kg/day by continuous infusion (with single dose 1 hour bolus of 0.066ug/kg). This indicated a near 2 log protection or more in predicted Cmax of XPAT vs PAT. A HER2-XPAT has been dose escalated up to 21 mg/kg in cynos and was well-tolerated, with the MTD still unreached. At doses starting from 2.5mg/kg of a HER2-XPAT, lymphocyte margination and laboratory abnormalities were observed, indicating evidence of biologic activity well below the tolerated 21 mg/kg dose. An estimated T1/2 of ~4 days was observed.

Conclusions: EGFR-XPAT and HER2-XPAT are novel T cell engagers with protease-cleavable XTEN masks with preclinical evidence of potent anti-tumor activity and a wide margin of protection in cynos. With the prior XTEN clinical data of low immunogenicity, the XPAT TCEs provide a promising solution to overcome On-target, Off-tumor toxicity. Additional PD, safety and efficacy data will be presented.

Citation Format: Fiore Cattaruzza, Ayesha Nazeer, Zachary Lange, Mikhail Hammond, Caitlin Koski, Angela Henkensiefken, Mika K. Derynck, Bryan Irving, Volker Schellenberger. HER2-XPAT and EGFR-XPAT: Pro-drug T-cell engagers (TCEs) engineered to address on-target, off-tumor toxicity with potent efficacy in vitro and in vivo and large safety margins in NHP [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3376.

Phase Ib: Preliminary clinical activity and immune activation for NKTR-262 [TLR 7/8 agonist] plus NKTR-214 [CD122-biased agonist] in patients (pts) with locally advanced or metastatic solid tumors (REVEAL Phase Ib/II Trial)

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Background: NKTR-262 is a novel intratumoral prodrug designed to promote tumor antigen release, an immune stimulatory environment, and antigen presentation. NKTR-214 increases CD8+ T cells and NK cells in the tumor microenvironment. The combination of NKTR-262 with NKTR-214 accesses innate and adaptive immunity to provide an abscopal response and systemic tumor immunity. The Phase 1b/2 REVEAL trial is enrolling. Methods: In a 3+3 Phase 1 design, pts who are relapsed/refractory to ≥1 CPI receive escalating doses of intratumoral (IT) NKTR-262 followed by combined q3w treatment of IT NKTR-262 and fixed-dose intravenous (IV) NKTR-214 (0.006 mg/kg). Phase 1 will evaluate PK, safety, efficacy, and determine recommended Phase 2 dose. Scans are conducted every 9 wks (± 1 wk). Peripheral blood (PB) and tumor tissue are collected to measure biomarkers of immune activation. In Phase 2 expansion, NKTR-262 + NKTR-214 ± IV nivolumab (360 mg) will be assessed in specific tumor cohorts of IO-naïve and experienced pts. Results: As of 06 Nov 2018, 11 pts had received at least one cycle of NKTR-262 + NKTR-214 therapy. 7/11 pts were efficacy evaluable with at least one on-treatment scan (4 MEL, 2 SARC, 1 CRC). 2/4 R/R melanoma pts had uPRs with 100% (scan 2) and 40% (scan 1) reductions in target lesions per RECIST 1.1, respectively. Both patients remain on treatment. Two SARC pts had stable disease at scan 1. No pts experienced G3 or higher TRAEs or immune-related adverse events (AEs). Most common G1-2 AEs were transient flu-like symptoms. Gene expression analysis of tumor and PB show dose-dependent induction (4 to 16-fold) of TLR target genes. Consistent with the mechanism of action for NKTR-214, PB flow cytometry shows an average 13-fold increase from baseline in Ki67+ CD8+T cells in 6 pts. Conclusions: NKTR-262 + NKTR-214 engage the immune activation cascade from local tumor antigen production to anti-tumor T cell response. Initial dose levels of NKTR-262 with fixed-dose NKTR-214 were well-tolerated with early evidence of clinical activity. These data support continued evaluation of the combination +/- nivolumab. Clinical trial information: NCT03435640.

Abstract 3826: GITRL-Fc biomarker and mechanism study: GITRL-Fc reduces Treg frequency in tumors and requires effector function for inhibition of tumor growth

Activation of the co-stimulatory receptor GITR (Glucocorticoid-Induced Tumor Necrosis Factor Receptor) by GITR-Ligand (GITRL) promotes proliferation and activation of effector T cells (T eff) and inhibits suppressive activity of regulatory T cells (Treg). Here, we have further characterized the mechanism of action of a single-gene GITRL trimer fused to an immunoglobulin Fc domain (GITRL-Fc, 336B3) by examining pharmacodynamic (PD) biomarkers in time course studies. Mice bearing CT26.WT colon tumors were treated with weekly GITRL-Fc and sacrificed 24 hours, 7 and 14 days after the first dose. Immuno-phenotyping of tumor-associated immune cells revealed a reduction in Treg frequency in tumor by 24 hours post-dose that was maintained at 7 and 14 days. Furthermore, GITRL-Fc treatment increased activation markers on tumor-associated CD4+ and CD8+ T cells, suggesting an increased cytotoxic environment within the tumor. This was supported by significant and sustained increase in CD8+ T cell:Treg ratio in the tumor after GITRL-Fc treatment. To determine whether intratumoral (IT) injection of GITRL-Fc is an effective route of administration, we compared efficacy, pharmacodynamic (PD) markers and pharmacokinetics in IT- and intraperitoneal (IP)-injected mice bearing bilateral CT26.WT tumors. Both routes of administration showed similar tumor growth inhibition (TGI) and PD markers in both the treated and the abscopal tumors, but IT injection resulted in a significantly lower serum GITRL-Fc concentration, suggesting that IT administration may be an alternative route of administration to IP with similar efficacy. The GITRL-Fc molecule 336B3 is effector function competent and able to induce cell-mediated cytotoxicity upon binding. To determine whether this effector function is required for GITRL-Fc-induced TGI, we treated CT26.WT tumor-bearing mice with 336B3 and 336B22, a GITRL-Fc molecule deficient in effector function. The effector function-competent 336B3 induced significant TGI and a more robust activation of Teff cells and reduction in Treg frequency, when compared to 336B22, suggesting that effector function is important for efficacy. To identify biomarkers for GITRL-Fc, we performed microarray analyses on multiple syngeneic mouse models treated with GITRL-Fc and developed GITRL gene signatures from blood and from tumors. We also developed multiplexed immunohistochemistry panels designed to quantify frequency of GITR and GITRL expression (GITR+CD8, GITR+FOXP3) in tumors. In conclusion, we have examined the effects of GITRL-Fc on preclinical mouse models. Biomarker analysis showed that loss of Tregs, activation of T cells and Fc-mediated effector function are key elements in the mechanism of action of the molecule. We have identified potential biomarkers to be used for PD and potential predictive analysis in clinical trial patient samples.

Citation Format: Gretchen M. Argast, Belinda Cancilla, Fiore Cattaruzza, Pete Yeung, Reyhaneh Lahmy, Erwan Le Scolan, Rose Harris, Alayne Brunner, Min Wang, Fumiko Axelrod, Jorge Monteon, Jennifer Elechko, Andrew Lam, MingHong Xie, Earth Light Lowe, Gilbert O'Young, Austin Gurney, Ann M. Kapoun. GITRL-Fc biomarker and mechanism study: GITRL-Fc reduces Treg frequency in tumors and requires effector function for inhibition of tumor growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3826.

Abstract A030: Biomarker study of vantictumab plus paclitaxel in HER2- breast cancer patients

Introduction: We have developed a monoclonal antibody, vantictumab, that blocks canonical Wnt/β-catenin signaling through binding of five FZD receptors (1, 2, 5, 7, and 8). This antibody inhibits the growth of several tumor types, including breast. Vantictumab reduces tumor-initiating cell frequency and exhibits synergistic activity with standard-of-care (SOC) agents (Gurney et al., 2012). To confirm the mechanism of action and to potentially target breast cancer patients most likely to respond to vantictumab, we undertook a biomarker study. Methods: We previously identified a 6-gene Wnt pathway-related signature, FBXW2, CCND2, RHOU, CTBP2, WIF1, and DKK1, based on microarray gene expression data from 8 BC patient-derived xenograft (PDX) models with established in vivo response to vantictumab plus SOC. This signature successfully predicted the response of 8 additional and independent PDX breast tumors. We further developed a qPCR Research Use Only (RUO) assay for the 6 genes for use on FFPE human breast tumor samples. This assay was evaluated in the phase 1b study of vantictumab in combination with paclitaxel in locally recurrent or metastatic HER2- breast cancer (NCT01973309) and the signature was refined using a Lasso model with overall survival as the outcome. A repeated 10 fold cross-validation was used to evaluate the performance of the gene signature. The association of the signature with progression-free survival (PFS) and overall survival (OS) was examined (n=40 patients). Furthermore, pharmacodynamic (PD) biomarker analyses were performed on tumor biopsies and hair follicles by comparing gene expression data from post-treatment time points versus baseline data (Affymetrix U133 plus 2 Microarrays). Results: A potential predictive 6-gene Wnt pathway biomarker was identified based on preclinical data and the biomarker was evaluated and refined in a phase 1b study of vantictumab in combination with paclitaxel in HER2- breast cancer. In the phase 1b study, AUC = 75% with repeated 10 fold cross-validation measuring the performance of the gene signature. Based on this analysis, two genes, RHOU and DKK1, were dropped from the preclinical gene signature, which was consistent with the feature ranking in the preclinical qPCR data. The refined 4-gene signature was significantly associated with both PFS and OS at a 50% percentile cut-off. In addition, analysis of PD biomarkers demonstrated that Wnt pathway target genes including AXIN2, LEF1, and CTNNB1 were downregulated while differentiation markers, e.g., KRT19 and Wnt pathway inhibitors, e.g., SFRP1, DKK3 were upregulated by vantictumab plus paclitaxel. Conclusions: We developed a 4-gene signature as a potential predictive biomarker for the response to vantictumab plus paclitaxel in HER2- breast cancer. PD biomarker analysis in tumors and hair follicles confirmed the mechanism of action of vantictumab in patient samples. Preliminary efficacy of vantictumab plus paclitaxel in the phase 1b study was encouraging, particularly in breast cancer patients positive for the 4-gene signature. Updated biomarker and PK/PD data from the phase 1b trial (NCT01973309) will also be presented.

Citation Format: Chun Zhang, William R. Henner, Min Wang, Fiore Cattaruzza, Pete Yeung, Gilbert O'Young, Yuwang Liu, Gretchen Argast, Lu Xu, Shailaja Uttamsingh, John Lewicki, Ann M. Kapoun. Biomarker study of vantictumab plus paclitaxel in HER2- breast cancer patients [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A030.

RSPO3 antagonism inhibits growth and tumorigenicity in colorectal tumors harboring common Wnt pathway mutations

Activating mutations in the Wnt pathway are a characteristic feature of colorectal cancer (CRC). The R-spondin (RSPO) family is a group of secreted proteins that enhance Wnt signaling and RSPO2 and RSPO3 gene fusions have been reported in CRC. We have previously shown that Wnt pathway blockers exhibit potent combinatorial activity with taxanes to inhibit tumor growth. Here we show that RSPO3 antagonism synergizes with paclitaxel based chemotherapies in patient-derived xenograft models (PDX) with RSPO3 fusions and in tumors with common CRC mutations such as APC, β-catenin, or RNF43. In these latter types of tumors that represent over 90% of CRC, RSPO3 is produced by stromal cells in the tumor microenvironment and the activating mutations appear to sensitize the tumors to Wnt-Rspo synergy. The combination of RSPO3 inhibition and taxane treatment provides an approach to effectively target oncogenic WNT signaling in a significant number of patients with colorectal and other intestinal cancers.

Abstract 5621: Prevalence of GITR expression and pharmacodynamic (PD) biomarkers in syngeneic tumor models treated by a GITR agonist (GITRL-Fc)

GITRL (Glucocorticoid-Induced Tumor Necrosis Factor Receptor Ligand, TNFSF18) is a member of the tumor necrosis factor (TNF) ligand superfamily. GITRL binds and activates the co-stimulatory surface receptor GITR, which promotes proliferation and activation of effector T cells (Teff) and inhibits suppressive activity of regulatory T cells (Treg). It is thus hypothesized that co-stimulation of GITR by agonist agents will promote anti-tumor immunity. We generated a novel single-gene GITRL trimer fused to an immunoglobulin Fc domain (GITRL-Fc) that shows robust single agent antitumor efficacy and immune effects in multiple syngeneic mouse models, suggesting its potential benefit in cancer immunotherapy To investigate the prevalence of GITR expression in human tumors, RNA-Seq data analyses of 33 tumor types in TCGA showed GITR is highly expressed in a subset of solid tumors, including head & neck, lung, breast, esophageal, and bladder cancers. In most solid tumors, GITR expression correlated poorly with T cell markers, implying that GITR may not be exclusive to immune cells and may be expressed in tumor cells as well. Similar findings emerged from RNA-Seq data analysis of patient-derived xenograft (PDX) samples from 24 tumor types. The gene expression data was corroborated by immunohistochemistry (IHC) analysis of GITR expression in 17 tumor types which showed that in addition to immune cells, GITR was expressed on tumor cell membranes. A multi-platform approach was taken to investigate GITRL-Fc pharmacodynamic (PD) biomarkers in tumors and in matched whole blood samples from mice bearing CT26 colon, 4T1 breast, and B16F10 melanoma carcinoma models. Global gene expression levels were profiled by microarray on treated and control tissues. We also monitored the changes of immune cell populations and cytokine secretions by flow cytometry, Luminex and IHC. Immune gene changes were more robust in tumors than in blood samples. In tumor samples, GITRL-Fc increased the gene expression associated with T cells, CD8 T cells, cytotoxicity, Th1 cells, interferon gamma (IFN-γ), natural killer cells, Teff cells, and T cell activation markers. These gene changes were validated by quantitative real-time PCR. Similarly, flow cytometry analysis showed that GITRL-Fc promoted activation of CD4+ effector cells, decreased Treg frequency, and increased the ratio of CD8+ T cell/Treg in the tumor. GITRL-Fc also modulated secretion of cytokines in splenocytes, including an increase in IFN-γ. Taken together, the PD biomarker changes in immune-related gene expression, immune cell populations, and cytokine secretions observed in these preclinical tumor models are consistent with GITRL-Fc mechanism of action and demonstrated target engagement of GITRL-Fc. Additional approaches, including in-silico sorting, to monitor rare immune cell populations in tumor samples will be discussed.

Citation Format: Min Wang, Fiore Cattaruzza, Pete Yeung, Alayne Brunner, Erwan LeScolan, Yuwang Liu, Jennifer Cain, Gilbert OYoung, Earth Light Lowe, Belinda Cancilla, Rose Harris, Tim Hoey, Austin Gurney, John Lewicki, Gretchen Argast, Ann M. Kapoun. Prevalence of GITR expression and pharmacodynamic (PD) biomarkers in syngeneic tumor models treated by a GITR agonist (GITRL-Fc) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5621. doi:10.1158/1538-7445.AM2017-5621

Abstract 1911: R-SPONDIN3 antagonism sensitizes colorectal cancer to taxane treatment

Introduction: Colorectal cancer (CRC) is the third most common cancer diagnosed in both men and women. Dysregulation of the WNT/β-catenin pathway is the most commonly mutated pathway in CRC. R-spondins (RSPO), a family of secreted proteins, are enhancers of WNT signaling. Previous preclinical studies have demonstrated that WNT inhibition results in superior antitumor efficacy in combination with taxanes. This superior combinatorial activity with taxanes has been identified in lung, ovarian, breast and pancreatic cancers. Taxanes have been found to be generally ineffective in the clinical treatment of colorectal cancer. Analysis of the local microenvironment, or stem cell niche, has identified stromal cells as an abundant source of RSPO. In patient-derived tumor xenografts (PDX), the murine stromal cells replace human stromal cells and provide the microenvironment that supports tumor cell growth. We have classified PDX tumors as human RSPO3 high or low/negative using RNA sequencing and by expression studies. Inhibition of RSPO3 with OMP-131R10, a clinical stage therapeutic antibody which binds to human and murine RSPO3, has demonstrated efficacy in human RSPO3 high, APCWT PDX.

Purpose: Common features in CRC are mutations in APC or β-catenin which are present in approximately 90% of cases. Tumors with RSPO3 genomic translocation and/or overexpression of RSPO3 are generally APC WT and β-cateninWT, and thus RSPO overexpression represents an alternative mechanism to upregulate the Wnt pathway. Alternatively, RSPO3 may be secreted by murine stromal cells, or by a rare population of tumor cells. In this study, we tested OMP-131R10 in combination with taxane treatment in human RSPO3 low CRC PDX models with APC or β-catenin mutations and in a PDX model with a RSPO3 translocation.

Results: Anti-RSPO3 was highly effective in combination with nab-paclitaxel in a CRC model with an RSPO3 translocation and RSPO3 overexpression. Furthermore, the combination of OMP-131R10 and taxane treatment resulted in synergistic inhibition of tumor growth in 8/10 PDX models with APC or β -catenin mutations and low human tumor cell RSPO3 expression. Tumor regression or durable stable disease was evident in 6/8 models. Responsive models contained either heterozygous inactivating mutations in APC (6/8) or homozygous activating mutations in β-catenin (2/8). Combination of OMP-131R10 with paclitaxel potentiated mitotic arrest, enhanced terminal differentiation and reduced the tumorigenic cell frequency by 40 fold based on serial transplantation studies.

Conclusion: Anti-RSPO3 (OMP-131R10) was active in the majority of CRC PDX models tested when combined with taxane treatment. These CRC models harbored mutations in APC and β-catenin. This data indicates that RSPO3 inhibition is an effective means to target the mutated Wnt pathway in CRC, and that antagonizing RSPO3 in combination with paclitaxel may improve survival for CRC patients.

Citation Format: Marcus M. Fischer, V. Pete Yeung, Fiore Cattaruzza, Christopher Murriel, James W. Evans, Gilbert O'Young, Alayne Brunner, Min Wang, Belinda Cancilla, Ann Kapoun, Timothy Hoey. R-SPONDIN3 antagonism sensitizes colorectal cancer to taxane treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1911. doi:10.1158/1538-7445.AM2017-1911

WNT antagonists exhibit unique combinatorial antitumor activity with taxanes by potentiating mitotic cell death

The WNT pathway mediates intercellular signaling that regulates cell fate in both normal development and cancer. It is widely appreciated that the WNT pathway is frequently dysregulated in human cancers through a variety of genetic and epigenetic mechanisms. Targets in the WNT pathway are being extensively pursued for the development of new anticancer therapies, and we have advanced two WNT antagonists for clinical development: vantictumab (anti-FZD) and ipafricept (FZD8-Fc). We examined the antitumor efficacy of these WNT antagonists in combination with various chemotherapies in a large set of patient-derived xenograft models. In responsive models, WNT blockade led to profound synergy with taxanes such as paclitaxel, and the combination activity with taxanes was consistently more effective than with other classes of chemotherapy. Taxane monotherapy increased the frequency of cells with active WNT signaling. This selection of WNT-active chemotherapy-resistant tumorigenic cells was prevented by WNT-antagonizing biologics and required sequential dosing of the WNT antagonist followed by the taxane. The WNT antagonists potentiated paclitaxel-mediated mitotic blockade and promoted widespread mitotic cell death. By blocking WNT/β-catenin signaling before mitotic blockade by paclitaxel, we found that this treatment effectively sensitizes cancer stem cells to taxanes. This combination strategy and treatment regimen has been incorporated into ongoing clinical testing for vantictumab and ipafricept.

Rational combination therapy in young vs older patients with advanced colorectal cancer (CRC)

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Background: Although CRC is rare in young adults, the incidence has increased recently and patients present more commonly with Stage III or IV disease which may reflect differing biology. Prior analyses revealed a statistically significant increase in the risk of death in young patients with metastatic CRC compared to older patients. Methods: To assess age-dependent genetic changes, DNA and RNA from younger ( < 40) and older ( > 65) CRC were isolated, and whole exome and transcriptome sequencing analysis from 4699 FFPE CRC clinical specimens were performed. Hybridization capture was performed on up to 3,769 exons from 403 cancer-related genes and 47 introns of 19 genes commonly rearranged in cancer. Samples were sequenced to high (average 688X) uniform coverage. CRC PDXs were injected into athymic nude mice and randomized into vehicle control, refametinib (MEKi), OMP-18R5 (monoclonal Ab against FZD 1, 2, 5, 7, and 8), or the combination and treated for at least 28 days. Results: Gene alteration rates in the younger and older cohorts were similar in a majority of the genes analyzed. Alterations in CTNNB1 [p < 0.001, False Discovery Rate (FDR) = 0.07] and MLH1 (p < 0.001, FDR = 0.017) were found to be more common in younger patients. Older patients were more likely to have alterations in APC (p < 0.01, FDR < 0.01) and FAM123B (p < 0.01, FDR = 0.03). The CTNNB1 data provided support to explore the WNT pathway as a potential target for younger patients. Therefore, we conducted an in vivo study of MEKi and OMP-18R5 to assess efficacy in molecularly defined young CRC PDX models. In a young PDX models, we observed enhanced combination effects with tumor growth inhibition index (treated/control) of 13% in the combination arm (compared to tumor growth of 150 %, and 116%, respectively with MEKi and OMP-18R5 alone). Interestingly, in this PDX models, RNA sequencing data showed baseline enrichment in the WNT and mTOR pathway, not observed in the older PDX models. Conclusions: The combination of refametinib and OMP-18R5 showed enhanced antitumor activity in combination compared to the single agent arms. Studies investigating predictive biomarkers of response are currently underway.

Abstract 4652: Effects of anti-DLL4 treatment on non-small cell lung cancer (NSCLC) human xenograft tumors

Background: Non-small cell lung cancer (NSCLC) accounts for the vast majority of lung cancers, the leading cause of cancer-related deaths. Notch signaling has been shown to play an important role in lung cancer initiation and progression. Delta-like ligand 4 (DLL4) activates the Notch pathway and is important for cancer stem cell (CSC) survival. Demcizumab (OMP-21M18) is a humanized IgG2 anti-DLL4 antibody currently being tested in a Phase 2 trial in combination with pemetrexed and carboplatin for first-line treatment of patients with NSCLC. Previously, OMP-21M18 in combination with its mouse anti-DLL4 surrogate has been shown to inhibit tumor growth, decrease cancer stem cell frequency, and cause dysfunctional sprouting of new vessels resulting in an anti-angiogenic effect in patient-derived tumor xenograft (PDX) models in breast, colon, ovarian, and pancreatic cancers. Here we show results from NSCLC PDX models.

Methods and Results: Anti-DLL4 treatment was tested in a series of NSCLC PDX models. Because DLL4 inhibition has been shown to have effects on the tumor as well as the vasculature, the combination of OMP-21M18 (targeting human DLL4) and 21R30 (antibody targeting mouse DLL4) treatment in the PDX models was used to model demcizumab treatment in humans. Treatment with anti-DLL4 in combination with chemotherapy inhibited tumor growth in a series of NSCLC PDX models. Additionally, a tumorigenicity assay showed a decrease in the frequency of tumor-initiating cells following treatment with anti-DLL4 and chemotherapy. Gene expression analysis of tumor samples provided insights into the mechanism of action.

Conclusions: Anti-DLL4 treatment in a panel of NSCLC PDX tumor models in vivo showed inhibition of tumor growth and a decrease in the frequency of tumor-initiating cells. Mechanism of action and gene expression analysis of these models treated with anti-DLL4 will be presented. These findings provide additional evidence supporting demcizumab as an effective treatment for NSCLC patients.

Citation Format: Alayne Brunner, Fiore Cattaruzza, Wan-Ching Yen, Pete Yeung, Marcus Fischer, Belinda Cancilla, Gilbert O’Young, Raymond Tam, Yu-Wang Liu, Austin Gurney, John Lewicki, Tim Hoey, Min Wang, Ann M. Kapoun. Effects of anti-DLL4 treatment on non-small cell lung cancer (NSCLC) human xenograft tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4652.

Abstract 404: Development of a RSPO3 CLIA-validated assay as a predictive biomarker for response to anti-RSPO3 antibody treatment in patients with solid tumors

R-Spondin (RSPO) proteins bind to LGR receptors and potentiate Wnt/β-catenin signaling. We have identified a therapeutic anti-RSPO3 antibody targeting the RSPO-LGR pathway. In preclinical studies, RSPO3 gene expression has shown correlation with anti-RSPO3 antibody efficacy in multiple solid tumor types. A qPCR-based RSPO3 assay has been developed as a predictive biomarker for response to the anti-RSPO3 antibody. In addition, RSPO gene fusions may play a role in the activation of Wnt signaling. A gene fusion detection workflow consisting of a RSPO3 CLIA assay, a RSPO3 RUO assay and next generation sequencing (NGS) has also been developed.

We designed 6 qPCR-based assays for the RSPO3 CLIA assay development and 2 assays for the RUO assay. These assays were designed to span exon-exon junctions or target microarray probe set sequences. Amplification sensitivity and specificity were assessed for assay selection. The analytic performance of the candidate RSPO3 CLIA assay and quality control measures were established in a validation study. The validation study included: 1) performance specifications of the RSPO3 assay including analytical sensitivity, linearity, and precision, 2) determination of a reportable range, 3) establishment of a cut-off for the RSPO3 CLIA assay for patient selection, and 4) establishment of quality control procedures. 104 human cancer tissues and 24 independent patient-derived tumor xenografts (PDX) were used in these studies. To evaluate the fusion detection workflow, the RUO assay was performed on samples that tested above the CLIA assay cut-off. The delta Ct difference between the CLIA and RUO assays was calculated to identify potential fusions.

The limit of quantification was established for the RSPO3 CLIA assay. The 95% reference interval was estimated to be (-2.44, 16.02) with 90% confidence interval for the lower bound (-3.45, -2.12) and upper bound (15.26, 16.57). The delta Ct cut-off for the RSPO3 CLIA assay was set based on sensitivity, specificity and prevalence. No statistically significant difference in the total variance across the tested samples was observed. A549 and OV56 were identified to be cell line controls with established acceptable delta Ct limits. Using NGS, RSPO3 fusions were identified in 6 PDX tumors with delta Ct RUO - delta Ct CLIA&gt;7, including a novel fusion. This cut-off was further refined with NGS of 9 clinical samples. Prevalence of the RSPO3 expression and fusions will be presented.

A qPCR based RSPO3 assay was developed and CLIA-validated for use as a potential predictive biomarker for response to anti-RSPO3 therapy. This RSPO3 CLIA assay, together with the fusion detection workflow, will be evaluated in a Phase 1a/b dose escalation study of anti-RSPO3 (OMP-131R10) in advanced solid tumors and in combination with FOLFIRI in metastatic colorectal cancer (NCT02482441).

Citation Format: Chun Zhang, Yuwang Liu, Min Wang, Gilbert OYoung, Joy Kavanagh, Cheryl McFarlane, Fiore Cattaruzza, Pete Yeung, Jennifer Cain, Wan-Ching Yen, Marcus Fischer, Belinda Cancilla, Edwina Dobbin, Michelle McCarthy, Austin Gurney, Leonardo Faoro, John Lewicki, Tim Hoey, Ann M. Kapoun. Development of a RSPO3 CLIA-validated assay as a predictive biomarker for response to anti-RSPO3 antibody treatment in patients with solid tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 404.

Abstract P3-07-57: Development of a 6-gene qPCR RUO-validated assay as a predictive biomarker for response of vantictumab (OMP-18R5; anti-frizzled) in HER2- breast cancer patients

Background: We have developed a monoclonal antibody, vantictumab that blocks canonical WNT/β-catenin signaling through binding of five FZD receptors (1, 2, 5, 7, 8). This antibody inhibits the growth of several tumor types, including breast. Vantictumab reduces tumor-initiating cell frequency and exhibits synergistic activity with standard-of-care (SOC) agents (Gurney et al, 2012). To target breast cancer patients most likely to respond to vantictumab, we undertook a predictive biomarker study.

Methods: We have identified a 6-gene Wnt pathway-related signature, FBXW2, CCND2, RHOU, CTBP2, WIF1, and DKK1, based on microarray gene expression data from 8 breast cancer patient derived xenograft (PDX) models with established in vivo response to vantictumab plus SOC. This signature successfully predicted the response of 8 additional and independent PDX breast tumors. We further developed a qPCR Research Use Only (RUO) assay for the 6 genes to be used on FFPE human breast tumor samples. Multiple assays targeting different regions spanning each mRNA transcript were tested and selected based on PCR efficiency, specificity and sensitivity. We compared assay sensitivity under different cDNA synthesis and pre-amplification conditions: random vs. gene-specific priming, number of pre-amplification cycles, pre-amplification reaction volumes, and cDNA synthesis kits. A repeatability study was performed to test assay performance. The pre-amplification and PCR were repeated over three separate days and across two independent labs.

Results: Our results showed that cDNA synthesis by gene-specific priming followed by 18 cycles of pre-amplification performed the best and the assay is robust with minimal starting FFPE RNA input. The results of the repeatability study were consistent among the different days and the different labs (&lt;5% CV). Using the 6-gene qPCR RUO assay, the signature score from the microarray data was further refined using 12 PDX HER2- breast tumors with known in vivo response to vantictumab with SOC. The prevalence of the 6-gene signature was established using ∼100 HER2- breast cancer samples.

Conclusions: A robust 6-gene RUO-validated assay was developed as a predictive biomarker for vantictumab in HER2- breast cancer. The assay is currently being evaluated in a Phase 1b study of vantictumab with paclitaxel in HER2- breast cancer.

Citation Format: Zhang C, O'Young G, Wikstrom K, Davison T, Yeung P, Cattaruzza F, Yen W-C, Hoey T, Lewicki J, Rachmann R, Kerr P, Hill L, Eason R, McErlean S, Liu Y, Kapoun AM. Development of a 6-gene qPCR RUO-validated assay as a predictive biomarker for response of vantictumab (OMP-18R5; anti-frizzled) in HER2- breast cancer patients. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-57.

Abstract A30: Predictive and pharmacodynamic biomarkers of vantictumab (OMP-18R5; anti-Frizzled) in non-small cell lung cancer

Background: Vantictumab is a monoclonal antibody that blocks canonical WNT/β-catenin signaling through binding of five FZD receptors (1, 2, 5, 7, 8). This antibody inhibits the growth of several tumor types, reduces tumor-initiating cell frequency (TIC) and exhibits synergistic activity with standard-of-care (SOC) chemotherapeutic agents (Gurney et al., 2012). To target responsive patients and understand the mechanism of action of the drug, we set out to identify predictive and pharmacodynamic (PD) biomarkers of vantictumab in non-small cell lung cancer (NSCLC).

Materials and methods: The response to vanticutmab was established from in vivo efficacy experiments including different treatment groups: control, vantictumab, paclitaxel and vantictumab in combination with paclitaxel. For combination treatment, same day dosing and sequential dosing (paclitaxel dosed 2 days after the antibody) were compared. Samples were collected for PD biomarker analysis. To identify a predictive biomarker for the response to vantictumab in NSCLC patients, gene expression data from 7 NSCLC patient derived xenograft (PDX) models was analyzed. We utilized support vector machine-recursive feature elimination (SVM-RFE, Guyon et al., 2002) to select genes and support vector machine (SVM) for classification.

Results: Vantictumab showed significant tumor growth inhibition as a single agent as well as in combination with paclitaxel. The reduction of TIC and the antitumor efficacy of vantictumab were significantly enhanced with sequential dosing compared with same day dosing. These findings suggested that optimal synergy occurs using sequential dosing, likely due to enhanced blockade of cell cycle progression at mitosis. PD biomarker analysis confirmed inhibition of genes in Wnt, Notch, and stem cell pathways by vantictumab both as a single agent and also in combination with paclitaxel. Wnt pathway targets including AXIN2 and LEF1 were down-regulated significantly by vantictumab in both sequential dosing and same day dosing confirming the mechanism of action. From a series of 7 in vivo efficacy PDX experiments, LEF1 was identified as a predictive biomarker of vantictumab response and achieved the best performance with cross-validated positive predictive value (PPV) = negative predictive value (NPV) = sensitivity = specificity = 100%. Strong correlation was also observed between LEF1 gene expression and the ratio of tumor volume. Furthermore, LEF1 was able to successfully predict the response to vantictumab in 2 independent NSCLC PDX models. Prevalence estimation for LEF1 ranged from 35% to 50% based on public microarray datasets. LEF1 was also found to be significantly correlated with the response to vantictumab in combination with paclitaxel in 12 NSCLC PDX models (p = 0.0162), indicating LEF1 as a potential predictive biomarker of the response vantictumab as a single agent and in combination with SOC in NSCLC.

Conclusions: A biomarker study for the pharmacodynamics and response to vantictumab was performed using a series of PDX NSCLC models. PD biomarkers were identified which confirmed the mechanism of action of vantictumab. LEF1 was identified as a predictive biomarker and is being evaluated in the Phase 1b study of vantictumab in combination with SOC in previously treated NSCLC: NCT01957007. Comprehensive PD and predictive biomarker data will be presented.

Citation Format: CHUN ZHANG, Fiore Cattaruzza, Pete Yeung, Wan-Ching Yen, Marcus Fischer, Alayne Brunner, Min Wang, Belinda Cancilla, Rainer Brachmann, Tim Hoey, John Lewicki, Ann M. Kapoun. Predictive and pharmacodynamic biomarkers of vantictumab (OMP-18R5; anti-Frizzled) in non-small cell lung cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A30.

Non-invasive imaging and cellular tracking of pulmonary emboli by near-infrared fluorescence and positron-emission tomography

Functional imaging of proteolytic activity is an emerging strategy to quantify disease and response to therapy at the molecular level. We present a new peptide-based imaging probe technology that advances these goals by exploiting enzymatic activity to deposit probes labelled with near-infrared (NIR) fluorophores or radioisotopes in cell membranes of disease-associated proteolysis. This strategy allows for non-invasive detection of protease activity in vivo and ex vivo by tracking deposited probes in tissues. We demonstrate non-invasive detection of thrombin generation in a murine model of pulmonary embolism using our protease-activated peptide probes in microscopic clots within the lungs with NIR fluorescence optical imaging and positron-emission tomography. Thrombin activity is imaged deep in tissue and tracked predominantly to platelets within the lumen of blood vessels. The modular design of our probes allows for facile investigation of other proteases, and their contributions to disease by tailoring the protease activation and cell-binding elements.

Functional imaging of proteolytic activity is an emerging strategy to guide patient diagnosis and monitor clinical outcome. Here the authors present a peptide-based probe to detect and localize thrombin activity ex vivo and non-invasively in mouse models of wounding and pulmonary thrombosis.

Abstract 2576: Enhanced antitumor efficacy by sequential application of Wnt pathway antagonists in combination with taxanes

The Wnt/beta-catenin pathway, which signals through the Frizzled (FZD) receptor family and several co-receptors, has long been implicated in cancer. We have previously demonstrated that inhibition of Wnt/beta-catenin signaling by vantictumab (anti-Fzd7, OMP-18R5) or ipafricept (FZD8-Fc, OMP-54F28) inhibits tumor growth, decreases tumorigenicity and induces differentiation in solid tumors. The anti-tumor effect of our Wnt antagonists is most evident in combination with chemotherapeutic agents. We sought to determine if the anti-tumor effect of Wnt pathway inhibitors varied with different chemotherapeutic agents. We compared the growth inhibitory effect of vantictumab and ipafricept with either taxanes (paclitaxel and nab-paclitaxel) or with DNA synthesis inhibitors (gemcitabine and carboplatin) in patient-derived tumor xenografts. We observed enhanced anti-tumor activity when combining vantictumab or ipafricept with nab-paclitaxel or paclitaxel compared to the combination with gemcitabine or carboplatin in pancreatic ductal carcinoma and serous ovarian cancer xenograft models. Histologic analysis in a pancreatic ductal carcinoma indicated that nab-paclitaxel increased mitotic cells and beta-catenin levels. Importantly, the addition of vantictumab to nab-paclitaxel reversed the nab-paclitaxel-induced increase in mitotic cells and beta-catenin expression. A potential mechanism to account for these results involves the observation that Wnt/beta-catenin signaling is under cell cycle control and peaks at the G2/M phase. Taxanes inhibit microtubule function and block the cell cycle at G2/M. In contrast, other chemotherapeutic agents, such as platinum compounds and nucleoside analogs, inhibit DNA synthesis and block cell proliferation at S phase. Our findings suggest that combination of Wnt blockade with chemotherapeutic agents, such as taxanes, that induce G2/M arrest may resulted in enhanced anti-tumor activity. The optimal synergy of anti-Wnt plus taxane combination occurs when the antibody was applied prior to taxane. Further analyses in serous ovarian tumors reveal that pre-treatment with ipafricept resulted in dysregulated beta-cetenin localization within giant multi-nucleated cells and up-regulation of genes associated with negative regulators of G1 progression. Our work provides evidence for the enhanced anti-tumor effect of Wnt pathway inhibitors in combination with taxanes and highlights the importance of preclinical examination to identify the most efficacious combination therapy regimens and the timing of antibody action for Wnt antagonists in combination with taxanes for optimal treatment efficacy.

Citation Format: Wan-Ching Yen, Marcus Fischer, Belinda Cancilla, Fiore Cattaruzza, Tracy Tang, Pete Yeung, John Lewicki, Austin Gurney, Timothy Hoey. Enhanced antitumor efficacy by sequential application of Wnt pathway antagonists in combination with taxanes. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2576. doi:10.1158/1538-7445.AM2015-2576

Serine proteases and protease-activated receptor 2 mediate the proinflammatory and algesic actions of diverse stimulants

BACKGROUND AND PURPOSE

Although serine proteases and agonists of protease-activated receptor 2 (PAR2) cause inflammation and pain, the spectrum of proteases that are activated by proinflammatory and algesic stimuli and their contribution to inflammatory pain are uncertain.

EXPERIMENTAL APPROACH

Enzymic assays and selective inhibitors were used to characterize protease activity in mice after intraplantar injections of formalin, bradykinin, PAR2 activating peptide (AP) or vehicle. The capacity of these proteases and of recombinant mouse trypsin 4 to cleave fragments of PAR2 and to activate PAR2 in cell lines was determined. Protease inhibitors and par2 (-/-) mice were used to assess the contributions of proteases and PAR2 to pain and inflammation.

KEY RESULTS

Intraplantar injection of formalin, bradykinin or PAR2-AP led to the activation of proteases that were susceptible to the serine protease inhibitor melagatran but resistant to soybean trypsin inhibitor (SBTI). Melagatran inhibited mouse trypsin 4, which degraded SBTI. Proteases generated in inflamed tissues cleaved PAR2-derived peptides. These proteases and trypsin 4 increased [Ca(2+) ]i in PAR2-transfected but not in untransfected cells, and melagatran suppressed this activity. Melagatran or PAR2 deletion suppressed oedema and mechanical hypersensitivity induced by intraplantar formalin, bradykinin and PAR2-AP, but had no effect on capsaicin-induced pain.

CONCLUSIONS AND IMPLICATIONS

Diverse proinflammatory and algesic agents activate melagatran-sensitive serine proteases that cause inflammation and pain by a PAR2-mediated mechanism. By inducing self-activating proteases, PAR2 amplifies and sustains inflammation and pain. Serine protease inhibitors can attenuate the inflammatory and algesic effects of diverse stimuli, representing a useful therapeutic strategy.

Endothelin-converting enzyme 1 and β-arrestins exert spatiotemporal control of substance P-induced inflammatory signals

Although the intracellular trafficking of G protein-coupled receptors controls specific signaling events, it is unclear how the spatiotemporal control of signaling contributes to complex pathophysiological processes such as inflammation. By using bioluminescence resonance energy transfer and superresolution microscopy, we found that substance P (SP) induces the association of the neurokinin 1 receptor (NK1R) with two classes of proteins that regulate SP signaling from plasma and endosomal membranes: the scaffolding proteins β-arrestin (βARRs) 1 and 2 and the transmembrane metallopeptidases ECE-1c and ECE-1d. In HEK293 cells and non-transformed human colonocytes, we observed that G protein-coupled receptor kinase 2 and βARR1/2 terminate plasma membrane Ca(2+) signaling and initiate receptor trafficking to endosomes that is necessary for sustained activation of ERKs in the nucleus. βARRs deliver the SP-NK1R endosomes, where ECE-1 associates with the complex, degrades SP, and allows the NK1R, freed from βARRs, to recycle. Thus, both ECE-1 and βARRs mediate the resensitization of NK1R Ca(2+) signaling at the plasma membrane. Sustained exposure of colonocytes to SP activates NF-κB and stimulates IL-8 secretion. This proinflammatory signaling is unaffected by inhibition of the endosomal ERK pathway but is suppressed by ECE-1 inhibition or βARR2 knockdown. Inhibition of protein phosphatase 2A, which also contributes to sustained NK1R signaling at the plasma membrane, similarly attenuates IL-8 secretion. Thus, the primary function of βARRs and ECE-1 in SP-dependent inflammatory signaling is to promote resensitization, which allows the sustained NK1R signaling from the plasma membrane that drives inflammation.

Transient receptor potential ankyrin 1 mediates chronic pancreatitis pain in mice

Chronic pancreatitis (CP) is a devastating disease characterized by persistent and uncontrolled abdominal pain. Our lack of understanding is partially due to the lack of experimental models that mimic the human disease and also to the lack of validated behavioral measures of visceral pain. The ligand-gated cation channel transient receptor potential ankyrin 1 (TRPA1) mediates inflammation and pain in early experimental pancreatitis. It is unknown if TRPA1 causes fibrosis and sustained pancreatic pain. We induced CP by injecting the chemical agent trinitrobenzene sulfonic acid (TNBS), which causes severe acute pancreatitis, into the pancreatic duct of C57BL/6 trpa1(+/+) and trpa1(-/-) mice. Chronic inflammatory changes and pain behaviors were assessed after 2-3 wk. TNBS injection caused marked pancreatic fibrosis with increased collagen-staining intensity, atrophy, fatty replacement, monocyte infiltration, and pancreatic stellate cell activation, and these changes were reflected by increased histological damage scores. TNBS-injected animals showed mechanical hypersensitivity during von Frey filament probing of the abdomen, decreased daily voluntary wheel-running activity, and increased immobility scores during open-field testing. Pancreatic TNBS also reduced the threshold to hindpaw withdrawal to von Frey filament probing, suggesting central sensitization. Inflammatory changes and pain indexes were significantly reduced in trpa1(-/-) mice. In conclusion, we have characterized in mice a model of CP that resembles the human condition, with marked histological changes and behavioral measures of pain. We have demonstrated, using novel and objective pain measurements, that TRPA1 mediates inflammation and visceral hypersensitivity in CP and could be a therapeutic target for the treatment of sustained inflammatory abdominal pain.

The TGR5 receptor mediates bile acid-induced itch and analgesia

Patients with cholestatic disease exhibit pruritus and analgesia, but the mechanisms underlying these symptoms are unknown. We report that bile acids, which are elevated in the circulation and tissues during cholestasis, cause itch and analgesia by activating the GPCR TGR5. TGR5 was detected in peptidergic neurons of mouse dorsal root ganglia and spinal cord that transmit itch and pain, and in dermal macrophages that contain opioids. Bile acids and a TGR5-selective agonist induced hyperexcitability of dorsal root ganglia neurons and stimulated the release of the itch and analgesia transmitters gastrin-releasing peptide and leucine-enkephalin. Intradermal injection of bile acids and a TGR5-selective agonist stimulated scratching behavior by gastrin-releasing peptide- and opioid-dependent mechanisms in mice. Scratching was attenuated in Tgr5-KO mice but exacerbated in Tgr5-Tg mice (overexpressing mouse TGR5), which exhibited spontaneous pruritus. Intraplantar and intrathecal injection of bile acids caused analgesia to mechanical stimulation of the paw by an opioid-dependent mechanism. Both peripheral and central mechanisms of analgesia were absent from Tgr5-KO mice. Thus, bile acids activate TGR5 on sensory nerves, stimulating the release of neuropeptides in the spinal cord that transmit itch and analgesia. These mechanisms could contribute to pruritus and painless jaundice that occur during cholestatic liver diseases.

The receptor TGR5 mediates the prokinetic actions of intestinal bile acids and is required for normal defecation in mice

BACKGROUND & AIMS

Abnormal delivery of bile acids (BAs) to the colon as a result of disease or therapy causes constipation or diarrhea by unknown mechanisms. The G protein-coupled BA receptor TGR5 (or GPBAR1) is expressed by enteric neurons and endocrine cells, which regulate motility and secretion.

METHODS

We analyzed gastrointestinal and colon transit, as well as defecation frequency and water content, in wild-type, knockout, and transgenic mice (trg5-wt, tgr5-ko, and tgr5-tg, respectively). We analyzed colon tissues for contractility, peristalsis, and transmitter release.

RESULTS

Deoxycholic acid inhibited contractility of colonic longitudinal muscle from tgr5-wt but not tgr5-ko mice. Application of deoxycholic acid, lithocholic acid, or oleanolic acid (a selective agonist of TGR5) to the mucosa of tgr5-wt mice caused oral contraction and caudal relaxation, indicating peristalsis. BAs stimulated release of the peristaltic transmitters 5-hydroxytryptamine and calcitonin gene-related peptide; antagonists of these transmitters suppressed BA-induced peristalsis, consistent with localization of TGR5 to enterochromaffin cells and intrinsic primary afferent neurons. tgr5-ko mice did not undergo peristalsis or transmitter release in response to BAs. Mechanically induced peristalsis and transmitter release were not affected by deletion of tgr5. Whole-gut transit was 1.4-fold slower in tgr5-ko than tgr5-wt or tgr5-tg mice, whereas colonic transit was 2.2-fold faster in tgr5-tg mice. Defecation frequency was reduced 2.6-fold in tgr5-ko and increased 1.4-fold in tgr5-tg mice compared with tgr5-wt mice. Water content in stool was lower (37%) in tgr5-ko than tgr5-tg (58%) or tgr5-wt mice (62%).

CONCLUSIONS

The receptor TGR5 mediates the effects of BAs on colonic motility, and deficiency of TGR5 causes constipation in mice. These findings might mediate the long-known laxative properties of BAs, and TGR5 might be a therapeutic target for digestive diseases.

Active cathepsins B, L, and S in murine and human pancreatitis

Cathepsins regulate premature trypsinogen activation within acinar cells, a key initial step in pancreatitis. The identity, origin, and causative roles of activated cathepsins in pancreatic inflammation and pain are not defined. By using a near infrared-labeled activity-based probe (GB123) that covalently modifies active cathepsins, we localized and identified activated cathepsins in mice with cerulein-induced pancreatitis and in pancreatic juice from patients with chronic pancreatitis. We used inhibitors of activated cathepsins to define their causative role in pancreatic inflammation and pain. After GB123 administration to mice with pancreatitis, reflectance and confocal imaging showed significant accumulation of the probe in inflamed pancreas compared with controls, particularly in acinar cells and macrophages, and in spinal cord microglia and neurons. Biochemical analysis of pancreatic extracts identified them as cathepsins B, L, and S (Cat-B, Cat-L, and Cat-S, respectively). These active cathepsins were also identified in pancreatic juice from patients with chronic pancreatitis undergoing an endoscopic procedure for the treatment of pain, indicating cathepsin secretion. The cathepsin inhibitor K11777 suppressed cerulein-induced activation of Cat-B, Cat-L, and Cat-S in the pancreas and ameliorated pancreatic inflammation, nocifensive behavior, and activation of spinal nociceptive neurons. Thus pancreatitis is associated with an increase in the active forms of the proteases Cat-B, Cat-L, and Cat-S in pancreatic acinar cells and macrophages, and in spinal neurons and microglial cells. Inhibition of cathepsin activation ameliorated pancreatic inflammation and pain. Activity-based probes permit identification of proteases that are predictive biomarkers of disease progression and response to therapy and may be useful noninvasive tools for the detection of pancreatic inflammation.

Brain-gut interactions increase peripheral nociceptive signaling in mice with postinfectious irritable bowel syndrome

BACKGROUND & AIMS

To investigate the peripheral sensory effects of repeated stress in patients with postinfectious irritable bowel syndrome (IBS), we tested whether stress following self-limiting bacterial colitis increases colonic dorsal root ganglia (DRG) nociceptive signaling.

METHODS

C57BL/6 mice were infected with Citrobacter rodentium. Stress was induced using a 9-day water avoidance paradigm (days 21-30 after infection). Colonic DRG neuronal excitability was measured using perforated patch clamp techniques, in vitro multi-unit afferent recordings, and measurements of visceromotor reflexes.

RESULTS

Combined stress and prior infection increased corticosterone and epinephrine levels, compared with infected animals, but did not alter the resolution of colonic inflammation. These changes were associated with increased neuronal excitability and parallel changes in multi-unit afferent recordings and visceromotor reflex thresholds. Protease activity was increased at day 30 following infection with C rodentium. Protease inhibitors markedly reduced the effects of colonic supernatants on neuronal excitability from C rodentium but not stressed animals. Colonic DRG neurons expressed messenger RNAs for the β(2) adrenergic and glucocorticoid receptors; incubation with stress mediators recapitulated the effects on neuronal excitability observed with chronic stress alone. PAR2 activation with concentrations of the activating peptide SLIGRL that had no effect on neuronal excitability in controls caused marked increases in excitability when applied to neurons from chronically stressed animals.

CONCLUSIONS

Stress, combined with prior acute colitis, results in exaggerated peripheral nociceptive signaling. Proteases and stress mediators can signal directly to colonic DRG neurons; further analysis of these pathways could provide new targets for treatment of patients with postinfectious IBS.

Cathepsin S is activated during colitis and causes visceral hyperalgesia by a PAR2-dependent mechanism in mice

BACKGROUND & AIMS

Although proteases control inflammation and pain, the identity, cellular origin, mechanism of action, and causative role of proteases that are activated during disease are not defined. We investigated the activation and function of cysteine cathepsins (Cat) in colitis.

METHODS

Because protease activity, rather than expression, is regulated, we treated mice with fluorescent activity-based probes that covalently modify activated cathepsins. Activated proteases were localized by tomographic imaging of intact mice and confocal imaging of tissues, and were identified by electrophoresis and immunoprecipitation. We examined the effects of activated cathepsins on excitability of colonic nociceptors and on colonic pain, and determined their role in colonic inflammatory pain by gene deletion.

RESULTS

Tomography and magnetic resonance imaging localized activated cathepsins to the inflamed colon of piroxicam-treated il10(-/-) mice. Confocal imaging detected activated cathepsins in colonic macrophages and spinal neurons and microglial cells of mice with colitis. Gel electrophoresis and immunoprecipitation identified activated Cat-B, Cat-L, and Cat-S in colon and spinal cord, and Cat-S was preferentially secreted into the colonic lumen. Intraluminal Cat-S amplified visceromotor responses to colorectal distension and induced hyperexcitability of colonic nociceptors, which required expression of protease-activated receptor-2. Cat-S deletion attenuated colonic inflammatory pain induced with trinitrobenzene sulfonic acid.

CONCLUSIONS

Activity-based probes enable noninvasive detection, cellular localization, and proteomic identification of proteases activated during colitis and are potential diagnostic tools for detection of predictive disease biomarkers. Macrophage cathepsins are activated during colitis, and Cat-S activates nociceptors to induce visceral pain via protease-activated receptor-2. Cat-S mediates colitis pain and is a potential therapeutic target.

Transient receptor potential ankyrin 1 is expressed by inhibitory motoneurons of the mouse intestine

BACKGROUND & AIMS

Transient receptor potential ankyrin (TRPA) 1, an excitatory ion channel expressed by sensory neurons, mediates somatic and visceral pain in response to direct activation or noxious mechanical stimulation. Although the intestine is routinely exposed to irritant alimentary compounds and inflammatory mediators that activate TRPA1, there is no direct evidence for functional TRPA1 receptors on enteric neurons, and the effects of TRPA1 activation on intestinal function have not been determined. We characterized expression of TRPA1 by enteric neurons and determined its involvement in the control of intestinal contractility and transit.

METHODS

TRPA1 expression was characterized by reverse-transcription polymerase chain reaction and immunofluorescence analyses. TRPA1 function was examined by Ca(2+) imaging and by assays of contractile activity and transit.

RESULTS

We detected TRPA1 messenger RNA in the mouse intestine and TRPA1 immunoreactivity in enteric neurons. The cecum and colon had immunoreactivity for neuronal TRPA1, but the duodenum did not. TRPA1 immunoreactivity was also detected in inhibitory motoneurons and descending interneurons, cholinergic neurons, and intrinsic primary afferent neurons. TRPA1 activators, including cinnamaldehyde, allyl isothiocyanate (AITC), and 4-hydroxynonenal, increased [Ca(2+)](i) in myenteric neurons. These were reduced by a TRPA1 antagonist (HC-030031) or deletion of Trpa1. TRPA1 activation inhibited contractility of the segments of colon but not stomach or small intestine of Trpa1(+/+) but not Trpa1(-/-) mice; this effect was reduced by tetrodotoxin or N(G)-nitro-l-arginine methyl ester. Administration of AITC by gavage did not alter gastric emptying or small intestinal transit, but luminal AITC inhibited colonic transit via TRPA1.

CONCLUSIONS

Functional TRPA1 is expressed by enteric neurons, and activation of neuronal TRPA1 inhibits spontaneous neurogenic contractions and transit of the colon.

Serine proteases mediate inflammatory pain in acute pancreatitis

Acute pancreatitis is a life-threatening inflammatory disease characterized by abdominal pain of unknown etiology. Trypsin, a key mediator of pancreatitis, causes inflammation and pain by activating protease-activated receptor 2 (PAR(2)), but the isoforms of trypsin that cause pancreatitis and pancreatic pain are unknown. We hypothesized that human trypsin IV and rat P23, which activate PAR(2) and are resistant to pancreatic trypsin inhibitors, contribute to pancreatic inflammation and pain. Injections of a subinflammatory dose of exogenous trypsin increased c-Fos immunoreactivity, indicative of spinal nociceptive activation, but did not cause inflammation, as assessed by measuring serum amylase and myeloperoxidase activity and by histology. The same dose of trypsin IV and P23 increased some inflammatory end points and caused a more robust effect on nociception, which was blocked by melagatran, a trypsin inhibitor that also inhibits polypeptide-resistant trypsin isoforms. To determine the contribution of endogenous activation of trypsin and its minor isoforms, recombinant enterokinase (ENK), which activates trypsins in the duodenum, was administered into the pancreas. Intraductal ENK caused nociception and inflammation that were diminished by polypeptide inhibitors, including soybean trypsin inhibitor and a specific trypsin inhibitor (type I-P), and by melagatran. Finally, the secretagogue cerulein induced pancreatic nociceptive activation and nocifensive behavior that were reversed by melagatran. Thus trypsin and its minor isoforms mediate pancreatic pain and inflammation. In particular, the inhibitor-resistant isoforms trypsin IV and P23 may be important in mediating prolonged pancreatic inflammatory pain in pancreatitis. Our results suggest that inhibitors of these isoforms could be novel therapies for pancreatitis pain.

Transient receptor potential ion channels V4 and A1 contribute to pancreatitis pain in mice

The mechanisms of pancreatic pain, a cardinal symptom of pancreatitis, are unknown. Proinflammatory agents that activate transient receptor potential (TRP) channels in nociceptive neurons can cause neurogenic inflammation and pain. We report a major role for TRPV4, which detects osmotic pressure and arachidonic acid metabolites, and TRPA1, which responds to 4-hydroxynonenal and cyclopentenone prostaglandins, in pancreatic inflammation and pain in mice. Immunoreactive TRPV4 and TRPA1 were detected in pancreatic nerve fibers and in dorsal root ganglia neurons innervating the pancreas, which were identified by retrograde tracing. Agonists of TRPV4 and TRPA1 increased intracellular Ca(2+) concentration ([Ca(2+)](i)) in these neurons in culture, and neurons also responded to the TRPV1 agonist capsaicin and are thus nociceptors. Intraductal injection of TRPV4 and TRPA1 agonists increased c-Fos expression in spinal neurons, indicative of nociceptor activation, and intraductal TRPA1 agonists also caused pancreatic inflammation. The effects of TRPV4 and TRPA1 agonists on [Ca(2+)](i), pain and inflammation were markedly diminished or abolished in trpv4 and trpa1 knockout mice. The secretagogue cerulein induced pancreatitis, c-Fos expression in spinal neurons, and pain behavior in wild-type mice. Deletion of trpv4 or trpa1 suppressed c-Fos expression and pain behavior, and deletion of trpa1 attenuated pancreatitis. Thus TRPV4 and TRPA1 contribute to pancreatic pain, and TRPA1 also mediates pancreatic inflammation. Our results provide new information about the contributions of TRPV4 and TRPA1 to inflammatory pain and suggest that channel antagonists are an effective therapy for pancreatitis, when multiple proinflammatory agents are generated that can activate and sensitize these channels.

Expression and function of the bile acid receptor GpBAR1 (TGR5) in the murine enteric nervous system

BACKGROUND

Bile acids (BAs) regulate cells by activating nuclear and membrane-bound receptors. G protein coupled bile acid receptor 1 (GpBAR1) is a membrane-bound G-protein-coupled receptor that can mediate the rapid, transcription-independent actions of BAs. Although BAs have well-known actions on motility and secretion, nothing is known about the localization and function of GpBAR1 in the gastrointestinal tract.

METHODS

We generated an antibody to the C-terminus of human GpBAR1, and characterized the antibody by immunofluorescence and Western blotting of HEK293-GpBAR1-GFP cells. We localized GpBAR1 immunoreactivity (IR) and mRNA in the mouse intestine, and determined the mechanism by which BAs activate GpBAR1 to regulate intestinal motility.

KEY RESULTS

The GpBAR1 antibody specifically detected GpBAR1-GFP at the plasma membrane of HEK293 cells, and interacted with proteins corresponding in mass to the GpBAR1-GFP fusion protein. GpBAR1-IR and mRNA were detected in enteric ganglia of the mouse stomach and small and large intestine, and in the muscularis externa and mucosa of the small intestine. Within the myenteric plexus of the intestine, GpBAR1-IR was localized to approximately 50% of all neurons and to >80% of inhibitory motor neurons and descending interneurons expressing nitric oxide synthase. Deoxycholic acid, a GpBAR1 agonist, caused a rapid and sustained inhibition of spontaneous phasic activity of isolated segments of ileum and colon by a neurogenic, cholinergic and nitrergic mechanism, and delayed gastrointestinal transit.

CONCLUSIONS & INFERENCES

G protein coupled bile acid receptor 1 is unexpectedly expressed in enteric neurons. Bile acids activate GpBAR1 on inhibitory motor neurons to release nitric oxide and suppress motility, revealing a novel mechanism for the actions of BAs on intestinal motility.

A role for transient receptor potential vanilloid 4 in tonicity-induced neurogenic inflammation

BACKGROUND AND PURPOSE

Changes in extracellular fluid osmolarity, which occur after tissue damage and disease, cause inflammation and maintain chronic inflammatory states by unknown mechanisms. Here, we investigated whether the osmosensitive channel, transient receptor potential vanilloid 4 (TRPV4), mediates inflammation to hypotonic stimuli by a neurogenic mechanism.

EXPERIMENTAL APPROACH

TRPV4 was localized in dorsal root ganglia (DRG) by immunofluorescence. The effects of TRPV4 agonists on release of pro-inflammatory neuropeptides from peripheral tissues and on inflammation were examined.

KEY RESULTS

Immunoreactive TRPV4 was detected in DRG neurones innervating the mouse hindpaw, where it was co-expressed in some neurones with CGRP and substance P, mediators of neurogenic inflammation. Hypotonic solutions and 4alpha-phorbol 12,13-didecanoate, which activate TRPV4, stimulated neuropeptide release in urinary bladder and airways, sites of neurogenic inflammation. Intraplantar injection of hypotonic solutions and 4alpha-phorbol 12,13-didecanoate caused oedema and granulocyte recruitment. These effects were inhibited by a desensitizing dose of the neurotoxin capsaicin, antagonists of CGRP and substance P receptors, and TRPV4 gene knockdown or deletion. In contrast, antagonism of neuropeptide receptors and disruption of TRPV4 did not prevent this oedema. TRPV4 gene knockdown or deletion also markedly reduced oedema and granulocyte infiltration induced by intraplantar injection of formalin.

CONCLUSIONS AND IMPLICATIONS

Activation of TRPV4 stimulates neuropeptide release from afferent nerves and induces neurogenic inflammation. This mechanism may mediate the generation and maintenance of inflammation after injury and during diseases, in which there are changes in extracellular osmolarity. Antagonism of TRPV4 may offer a therapeutic approach for inflammatory hyperalgesia and chronic inflammation.

Transient receptor potential ankyrin-1 has a major role in mediating visceral pain in mice

The excitatory ion channel transient receptor potential ankyrin-1 (TRPA1) is prominently expressed by primary afferent neurons and is a mediator of inflammatory pain. Inflammatory agents can directly activate [e.g., hydroxynonenal (HNE), prostaglandin metabolites] or indirectly sensitize [e.g., agonists of protease-activated receptor (PAR(2))] TRPA1 to induce somatic pain and hyperalgesia. However, the contribution of TRPA1 to visceral pain is unknown. We investigated the role of TRPA1 in visceral hyperalgesia by measuring abdominal visceromotor responses (VMR) to colorectal distention (CRD) after intracolonic administration of TRPA1 agonists [mustard oil (MO), HNE], sensitizing agents [PAR(2) activating peptide (PAR(2)-AP)], and the inflammatory agent trinitrobenzene sulfonic acid (TNBS) in trpa1(+/+) and trpa1(-/-) mice. Sensory neurons innervating the colon, identified by retrograde tracing, coexpressed immunoreactive TRPA1, calcitonin gene-related peptide, and substance P, expressed TRPA1 mRNA and responded to MO with depolarizing currents. Intracolonic MO and HNE increased VMR to CRD and induced immunoreactive c-fos in spinal neurons in trpa1+/+ but not in trpa1(-/-) mice. Intracolonic PAR(2)-AP induced mechanical hyperalgesia in trpa1+/+ but not in trpa1(-/-) mice. TNBS-induced colitis increased in VMR to CRD and induced c-fos in spinal neurons in trpa1(+/+) but not in trpa1(-/-) mice. Thus TRPA1 is expressed by colonic primary afferent neurons. Direct activation of TRPA1 causes visceral hyperalgesia, and TRPA1 mediates PAR(2)-induced hyperalgesia. TRPA1 deletion markedly reduces colitis-induced mechanical hyperalgesia in the colon. Our results suggest that TRPA1 has a major role in visceral nociception and may be a therapeutic target for colonic inflammatory pain.

Endothelin-converting enzyme 1 promotes re-sensitization of neurokinin 1 receptor-dependent neurogenic inflammation

BACKGROUND AND PURPOSE

The metalloendopeptidase endothelin-converting enzyme 1 (ECE-1) is prominently expressed in the endothelium where it converts big endothelin to endothelin-1, a vasoconstrictor peptide. Although ECE-1 is found in endosomes in endothelial cells, the role of endosomal ECE-1 is unclear. ECE-1 degrades the pro-inflammatory neuropeptide substance P (SP) in endosomes to promote recycling and re-sensitization of its neurokinin 1 (NK(1)) receptor. We investigated whether ECE-1 regulates NK(1) receptor re-sensitization and the pro-inflammatory effects of SP in the endothelium.

EXPERIMENTAL APPROACH

We examined ECE-1 expression, SP trafficking and NK(1) receptor re-sensitization in human microvascular endothelial cells (HMEC-1), and investigated re-sensitization of SP-induced plasma extravasation in rats.

KEY RESULTS

HMEC-1 expressed all four ECE-1 isoforms (a-d), and fluorescent SP trafficked to early endosomes containing ECE-1b/d. The ECE-1 inhibitor SM-19712 prevented re-sensitization of SP-induced Ca2+ signals in HMEC-1 cells. Immunoreactive ECE-1 and NK(1) receptors co-localized in microvascular endothelial cells in the rat. SP-induced extravasation of Evans blue in the urinary bladder, skin and ears of the rat desensitized when the interval between two SP injections was 10 min, and re-sensitized after 480 min. SM-19712 inhibited this re-sensitization.

CONCLUSIONS AND IMPLICATIONS

By degrading endocytosed SP, ECE-1 promotes the recycling and re-sensitization of NK(1) receptors in endothelial cells, and thereby induces re-sensitization of the pro-inflammatory effects of SP. Thus, ECE-1 inhibitors may ameliorate the pro-inflammatory actions of SP.

Evidence for the involvement of 5-HT2A receptors in mild mesenteric ischemia/reperfusion dysfunctions in mice

In this study, the involvement of 5-HT2A receptors on mesenteric ischemia-reperfusion injury was examined in mice. Intestinal ischemia produced by 45 min occlusion of superior mesenteric artery was followed by 24h reperfusion (I/R). The 5-HT2A selective antagonist, ketanserin (0.5 mgkg(-1)) or the 5-HT2A agonist DOI (0.25 mgkg(-1)) was intravenously administered before ischemia and 8h after the beginning of reperfusion. The effects were compared with those obtained in sham operated animals (S). Ketanserin prevented the upper gastrointestinal transit delay induced by I/R (P<0.01), protected intestine from leukocyte recruitment as indicated by jejunal myeloperoxidase activity (P<0.05) and reverted Evans Blue extravasation elicited by I/R in lung, colon and jejunum (P<0.05). On the other hand, 5-HT2A activation by DOI mimicked the effects of I/R in S mice prolonging small intestine transit (P<0.05) and enhancing neutrophil accumulation in jejunal tissues (P<0.05). Furthermore, the reduction of ADP-induced platelet aggregation in plasma of I/R mice was prevented by ketanserin treatment. All together, these findings support the critical involvement of 5-HT2A receptor subtype in mediating the damage induced by mesenteric I/R in mice.

An AFM investigation of oligonucleotides anchored on unoxidized crystalline silicon surfaces

Carboxylic terminated monolayers have been covalently attached on phosphorous doped crystalline (100) silicon surfaces using a cathodic electro grafting technique. The functionalization concentration and efficiency have been evaluated with different techniques. In particular, topographic images, performed with an atomic force microscope, were used to optimize the protocol in order to obtain a surface whose characteristics of uniformity and reproducibility are ideal for a bio-electronic device. Phase lag images of the functionalized surfaces were also performed, and show non-topographic structures that have been interpreted as areas of different molecule self-orientation. Poly-thymine oligonucleotides have been anchored on such a surface to form a nano-biosensing device capable to react selectively with a specific target molecule, a poly-adenine oligonucleotide. AFM images of high density (approximately 3x10(12) mol/cm2) single strand and double strand covered samples show toroidal shaped structures formed by the self-assembly of the oligonucleotides on the silicon surface.

Protective effect of proteinase-activated receptor 2 activation on motility impairment and tissue damage induced by intestinal ischemia/reperfusion in rodents

We hypothesized that proteinase-activated receptor-2 (PAR(2)) modulates intestinal injuries induced by ischemia/reperfusion. Ischemia (1 hour) plus reperfusion (6 hours) significantly delayed gastrointestinal transit (GIT) compared with sham operation. Intraduodenal injection of PAR(2)-activating peptide SLIGRL-NH(2) significantly accelerated transit in ischemia/reperfusion but not in sham-operated rats. GIT was significantly delayed in ischemia/reperfusion and sham-operated PAR(2)(-/-) mice compared with PAR(2)(+/+). SLIGRL-NH(2) significantly accelerated transit in ischemia/reperfusion in PAR(2)(+/+) but not in PAR(2)(-/-) mice. Prevention of mast cell degranulation with cromolyn, ablation of visceral afferents with capsaicin, and antagonism of calcitonin gene-related peptide (CGRP) and neurokinin-1 receptors with CGRP(8-37) and RP67580, respectively, abolished the SLIGRL-NH(2)-induced stimulatory effect on transit in ischemia/reperfusion. Tissue damage was significantly reduced by SLIGRL-NH(2); this effect was not observed in cromolyn-, capsaicin-, or RP67580-treated rats but was detected following CGRP(8-37). Intestinal PAR(2) mRNA levels were not affected by SLIGRL-NH(2) in ischemia/reperfusion. We propose that PAR(2) modulates GIT and tissue damage in intestinal ischemia/reperfusion by a mechanism dependent on mast cells and visceral afferents. PAR(2) effect on transit might be mediated by CGRP and substance P, whereas the effect on tissue damage appears to involve substance P but not CGRP. PAR(2) might be a signaling system in the neuroimmune communication in intestinal ischemia/reperfusion.

The selective inhibition of inducible nitric oxide synthase prevents intestinal ischemia-reperfusion injury in mice

Nitric oxide (NO) involvement in intestinal ischemia-reperfusion (I/R) injury has been widely suggested but its protective or detrimental role remains still question of debate. Here, we examine the impact of supplementation or inhibition of NO availability on intestinal dysmotility and inflammation caused by mesenteric I/R in mice. Ischemia 45min and reperfusion 24h were performed by superior mesenteric artery occlusion in female Swiss mice. Saline-treated sham-operated (S) or normal mice without surgery (N) served as controls. Drugs were subcutaneously injected 0, 4, 8, and 18 h after ischemia. Upper gastrointestinal transit (GIT, estimated through black marker gavage), intestinal myeloperoxidase activity (MPO), intestinal malondialdehyde levels (MDA), Evans blue extravasation (EB), intestinal histological damage, and mean arterial pressure (MAP) were considered. In I/R mice, GIT was significantly delayed compared to S and N groups; MPO activity and EB extravasation enhanced, whereas MDA levels did not change. Compared to N and S groups, in I/R mice selective iNOS inhibitor P-BIT significantly prevented motor, MPO and EB changes; putative iNOS inhibitor aminoguanidine significantly counteracted GIT delay but not neutrophil recruitment and the increase in vascular permeability; NOS inhibitor l-NAME and NO precursor l-arginine were scarcely or no effective. Furthermore, in S mice aminoguanidine caused a significant increase of MPO activity reverted by H(1) histamine receptor antagonist pre-treatment. Unlike P-BIT, aminoguanidine and l-NAME injection increased MAP. These findings confirm a detrimental role for iNOS-derived NO overproduction during reperfusion. Aminoguanidine-associated neutrophil recruitment suggests that this drug could act through mechanisms additional to iNOS inhibition involving both eNOS blockade, as indicated by its hemodynamic effects, and indirect activation of H(1) histamine receptors.

AFM characterization of solid-supported lipid multilayers prepared by spin-coating

Lipids are the principal components of biologically relevant structures as cellular membranes. They have been the subject of many studies due to their biological relevance and their potential applications. Different techniques, such as Langmuir-Blodgett and vesicle-fusion deposition, are available to deposit ordered lipid films on etched surfaces. Recently, a new technique of lipid film deposition has been proposed in which stacks of a small and well-controlled number of bilayers are prepared on a suitable substrate using a spin-coater. We studied the morphological properties of multi-layers made of cationic and neutral lipids (DOTAP and DOPC) and mixtures of them using dynamic mode atomic force microscopy (AFM). After adapting and optimizing, the spin-coating technique to deposit lipids on a chemically etched Silicon (1,0,0) substrate, a morphological nanometer-scale characterization of the aforementioned samples has been provided. The AFM study showed that an initial layer of ordered vesicles is formed and, afterward, depending on details of the spin-coating preparation protocol and to the dimension of the silicon substrate, vesicle fusion and structural rearrangements of the lipid layers may occur. The present data disclose the possibility to control the lipid's structures by acting on spin-coating parameters with promising perspectives for novel applications of lipid films.