Supplementary Figure 4 from Anti-DLL4 Inhibits Growth and Reduces Tumor-Initiating Cell Frequency in Colorectal Tumors with Oncogenic KRAS Mutations

Supplementary Table 1, Materials and Methods, Figure Legends 1-4 from Anti-DLL4 Inhibits Growth and Reduces Tumor-Initiating Cell Frequency in Colorectal Tumors with Oncogenic <i>KRAS</i> Mutations

Supplemental figures include the RSPO gene expression analysis for CRC models, the in vitro testing of anti-RSPO antibodies on RSPO-negative tumors, the IHC analysis of anti-RSPO3+chemo-treated ovarian tumors, the LGR, ZNRF3, and RNF43 gene expression profile in therapy responsive and non-responsive PDXs, the in vivo resistance of RSPO-negative tumors to RSPO blockade, the analysis of CSC frequency in anti-RSPO3-treated NSCL and pancreatic PDXs, and the IHC detection of CD44 in anti-RSPO3-treated CRC tumors.

Supplemental figure legends also include brief methods where appropriate.

Supplemental Tables include a list and brief description of xenograft models used in the study, the RSPO1-4 gene expression profile and beta-catenin activation status of all xenograft models, and the microarray analysis for 4 CRC xenograft models after treatment with anti-RSPO3 antibody.

Figure S1A. Binding affinities of OMP-59R5 to human (h) Notch1-4 receptors; Figure S1B. Alignment of the EGF repeats 10-15 of Notch2 and 9-14 of Notch3 from human (h), cynomolgus monkey (cyno), and mouse (m); Figure S2. Human NOTCH1, NOTCH2 and NOTCH3 gene in patient-derived primary xenograft tumors; Figure S3. Effect of OMP-59R5 on tumor growth of individual animals in OMP-PN8 and OMP-PN17 xenografts (from Figure 2); Figure S4A. Effect of OMP-59R5 on goblet cells; Figure S4B. Effect of OMP-59R5 on teeth in NOD/SCID mice; Figure S5. Effect of OMP-59R5 on (a) gene expression, (b) Human vimentin IHC (c) Western blot of Notch3 transmembrane domain (TM) and Notch3 intracellular domain (ICD) protein levels and (d) Quantitation of Notch1 ICD staining intensity levels in pancreatic xenograft tumors; Figure S6A. Effect of OMP-59R5 in combination with gemcitabine or gemcitabine/nab-paclitaxel in OMP-PN8 xenograft tumors; Figure S6B. Effect of OMP-59R5 in combination with gemcitabine/nab-paclitaxel on body weight change in OMP-PN8 xenograft tumor-bearing NOD/SCID mice (from Figure 4B); Figure S6C. Activity of OMP-59R5 in combination with nab-paclitaxel plus gemcitabine in OMP-PN16; Figure S8A. Perfused vessels are associated with the presence of desmin; Figure S8B. Quantification of perfused blood vessels; Figure S8C. Targeting DLL4/Notch signaling and Notch2/3 signaling has opposite effect on tumor stroma/vasculature; Figure S7A. Anti-tumor effect of OMP-59R5 in SCLC tumors; Figure S7B. Effect of OMP-59R5 on Notch3 ECD and Notch3 ICD expression in UM-PE13 xenograft tumors; Figure S7C. Limiting Dilution Assay

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.

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.

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.

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>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 Purpose: The Notch pathway plays an important role in both stem cell biology and cancer. Dysregulation of Notch signaling has been reported in several human tumor types. In this report, we describe the development of an antibody, OMP-59R5 (tarextumab), which blocks both Notch2 and Notch3 signaling. Experimental Design: We utilized patient-derived xenograft tumors to evaluate antitumor effect of OMP-59R5. Immunohistochemistry, RNA microarray, real-time PCR, and in vivo serial transplantation assays were employed to investigate the mechanisms of action and pharmacodynamic readouts. Results: We found that anti-Notch2/3, either as a single agent or in combination with chemotherapeutic agents was efficacious in a broad spectrum of epithelial tumors, including breast, lung, ovarian, and pancreatic cancers. Notably, the sensitivity of anti-Notch2/3 in combination with gemcitabine in pancreatic tumors was associated with higher levels of Notch3 gene expression. The antitumor effect of anti-Notch2/3 in combination with gemcitabine plus nab-paclitaxel was greater than the combination effect with gemcitabine alone. OMP-59R5 inhibits both human and mouse Notch2 and Notch3 function and its antitumor activity was characterized by a dual mechanism of action in both tumor and stromal/vascular cells in xenograft experiments. In tumor cells, anti-Notch2/3 inhibited expression of Notch target genes and reduced tumor-initiating cell frequency. In the tumor stroma, OMP-59R5 consistently inhibited the expression of Notch3, HeyL, and Rgs5, characteristic of affecting pericyte function in tumor vasculature. Conclusions: These findings indicate that blockade of Notch2/3 signaling with this cross-reactive antagonist antibody may be an effective strategy for treatment of a variety of tumor types. Clin Cancer Res; 21(9); 2084–95. ©2015 AACR.

Ovarian cancer is the deadliest gynecologic malignancy and the fifth leading cause of death from cancer in women in the U.S. 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 developed ipafricept (FZD8-Fc, OMP-54F28), a recombinant fusion protein consisting of the ligand-binding domain of FZD8 and a human IgG1 Fc fragment. This fusion protein blocks Wnt signaling induced by multiple Wnt family members by binding and sequestering WNT. Using minimally passaged ovarian patient-derived xenograft tumors (PDX), we demonstrate that ipafricept is efficacious in combination with chemotherapy in four of eight ovarian cancer PDX tumors examined. Utilizing an in vivo serial transplantation assay, we quantified a reduction of the tumor initiating cell frequency by ipafricept in combination with paclitaxel. Additionally, we have discovered that pre-treatment with ipafricept several days prior to paclitaxel therapy enhances the activity of both agents when compared to delivering the drugs simultaneously. The anti-tumor effect observed is directly associated with a modulation of Wnt pathway gene sets. In responsive tumors, we discovered that a large number of WNT target genes were significantly down-regulated by ipafricept (e.g, AXIN2, LRP5/6, and FZD8). Conversely, in non-responsive tumors, these genes were either unchanged or up-regulated by the combination therapy. Histologic analysis revealed that total beta-catenin protein levels were reduced by ipafricept alone and in combination with paclitaxel in responsive tumors but were unchanged in non-responsive tumors. We are using these tumors to develop biomarkers that can be used clinically. Our data demonstrates the potential therapeutic benefit of targeting Wnt signaling in ovarian cancer. A Phase 1b clinical trial is currently examining ipafricept in combination with paclitaxel and carboplatin in patients with recurrent platinum-sensitive ovarian cancer. Citation Format: Marcus M. Fischer, Wan-Ching Yen, Chun Zheng, Randall Henner, Fiore Cattaruzza, Tracy Tang, Pete Yeung, Tanuka Biswas, John Lewicki, Austin Gurney, Ann M. Kapoun, Timothy Hoey. Wnt pathway antagonist ipafricept (FZD8-Fc, OMP-54F28) inhibits tumor growth and reduces tumor-initiating cell frequency in ovarian patient-derived xenograft models. [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 4233. doi:10.1158/1538-7445.AM2015-4233

Abstract Both Notch/Delta-like ligand 4 (DLL4) and vascular endothelial growth factor (VEGF) pathways play a critical role in angiogenesis and tumor growth. Due to differential regulatory effects of VEGF and DLL4 on the vasculature, blockade of DLL4 or VEGF signaling inhibits tumor growth by distinct mechanisms: anti-DLL4 treatment induces an abnormal increase of poorly perfused blood vessels, which results in nonproductive angiogenesis unable to support tumor growth, whereas anti-VEGF therapy significantly decreases vasculature reducing the blood supply to tumors. In addition, DLL4-Notch signaling plays a key role in the maintenance of cancer stem cells. We have recently developed a bispecific monoclonal antibody that targets both human DLL4 and human VEGF (OMP-305B83). In vitro, this antibody exhibited low nanomolar binding affinity to hVEGF and hDLL4, and reduced human endothelial cell proliferation induced by VEGF. The bispecific antibody demonstrated significant in vivo anti-tumor efficacy in various solid tumors, induced tumor regression, decreased the frequency of tumor initiating cells, and delayed tumor recurrence following termination of chemotherapy. Analysis of tumor vasculature after treatment with anti-DLL4/VEGF revealed inhibition of vascular gene expression and endothelial cell proliferation, indicating that the anti-VEGF effect on the vasculature is dominant over the anti-DLL4 effect. Notably, at doses where both anti-DLL4 and anti-VEGF alone produces suboptimal anti-tumor effect, dual targeting resulted in additive tumor growth inhibition. The combination of anti-DLL4 and anti-VEGF resulted in broad spectrum efficacy in many different solid tumor types including breast, colon, ovarian and pancreatic tumors. Notably, serial transplantation studies indicated that the anti-cancer stem cell activity of anti-DLL4 was retained with the bispecific. In safety studies, OMP-305B83 demonstrated an improved cardiac profile in cynomolgus monkeys compared to anti-DLL4 with reduction of endothelial hyperplasia and suppression of vascular-related gene upregulation in the heart. These results indicate that our bispecific anti-DLL4/VEGF is broadly efficacious and may be useful for treatment of a variety of tumor types. We are currently enrolling patients with advanced refractory solid tumors in a Phase 1a clinical trial. Citation Format: Wan-Ching Yen, Marcus M. Fischer, Gretchen Argast, Breanna Wallace, Min Wang, Rene Meisner, John Lewicki, Ann M. Kapoun, Austin Gurney, Timothy Hoey. Dual targeting of the DLL4 and VEGF pathways with a bispecific monoclonal antibody inhibits tumor growth and reduces cancer stem cell frequency. [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 C164.

Abstract 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-FZD) or OMP-54F28 (FZD8-Fc) 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 OMP-54F28 with either taxanes (paclitaxel and nab-paclitaxel) or with DNA synthesis inhibitors (gemcitabine and carboplatin) in patient-derived tumor xenografts. In a model for pancreatic ductal carcinoma, vantictumab with nab-paclitaxel was more efficacious than vantictumab with gemcitabine in inhibiting tumor growth and Wnt target gene expression (at doses of nab-paclitaxel and gemcitabine that were equivalent in their single-agent growth-inhibitory effects). Histologic analysis 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. An independent experiment in a serous ovarian cancer xenograft model also showed enhanced anti-tumor activity when combining OMP-54F28 with either paclitaxel or nab-paclitaxel compared to the combination with carboplatin. A potential mechanism to account for these results involves on 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. We hypothesize that combination of Wnt blockade with chemotherapeutic agents, such as taxanes, that induce G2/M arrest may result in optimal anti-tumor activity. Citation Format: Wan-Ching Yen, Marcus M. Fischer, John Lewicki, Austin Gurney, Timothy Hoey. Enhanced anti-tumor effect of WNT pathway antagonists in combination with taxanes. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4547. doi:10.1158/1538-7445.AM2014-4547

Abstract Deregulation of the canonical Wnt/beta-catenin signaling pathway has long been associated with cancer. Intracellular components of this pathway, including Axin, APC, and beta-catenin are frequently mutated in a range of human tumors. The identity of specific extracellular ligands that contribute to human cancer development through this signaling axis has remained unclear. Molecular characterization of the secreted beta-catenin signaling activities produced by minimally passaged human tumor xenograft models identified RSPO family members produced by multiple tumor types including ovarian, pancreatic, colon, breast and non-small cell lung cancer. In human tumor xenograft models that had RSPO overexpression, in some instances due to genomic translocation, anti-RSPO treatment markedly inhibited tumor growth. In addition, striking combination activity with standard of care chemotherapy agents resulted in regression of established tumors. These results highlight the potential for therapeutic intervention with this newly appreciated signaling axis. Citation Format: Austin Gurney, Fumiko Axelrod, Chris Bond, Jennifer Cain, Cecile Chartier, Marcus Fischer, May Ji, Chris Murriel, Janak Raval, Jalpa Shah, Min Wang, Wan-Ching Yen, Ann Kapoun, John Lewicki, Timothy Hoey. Inhibition of R-spondin (RSPO) signaling reduces the growth of multiple human tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1764. doi:10.1158/1538-7445.AM2014-1764

Abstract The R-spondin-LGR signaling axis is a recently appreciated pathway that promotes beta-catenin signaling in normal stem cell populations. Beta-catenin signaling had long been considered synonymous with Wnt signaling. We conducted a reporter-based screen for secreted beta-catenin signaling activities produced by a panel of human tumors. This exercise and further molecular characterization efforts discovered RSPO activity produced by numerous human tumors of multiple tumor types including ovarian, pancreatic, colon, breast and non-small cell lung cancer. Specific antibody antagonists of RSPO family members were developed. In minimally passaged human tumor xenograft models, anti-RSPO treatment markedly inhibited tumor growth in several tumor types. Moreover, RPSO blockade promoted tumor differentiation and reduced the frequency of tumor initiating cells. These data highlight the potential for therapeutic intervention with this newly appreciated signaling axis. Citation Format: Austin Gurney, Cecile Chartier, Fumiko Axelrod, Jennifer Cain, Wan-Ching Yen, Christopher Murriel, Janak Raval, Marcus Fischer, Jalpa Shah, May Ji, Christopher Bond, Ann Kapoun, John Lewicki, Timothy Hoey. R-Spondin (RSPO) signaling drives the growth of multiple human tumor types. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 218. doi:10.1158/1538-7445.AM2013-218

Abstract Purpose: We previously showed that targeting Delta-like ligand 4 (DLL4) in colon and breast tumors inhibited tumor growth and reduced tumor initiating cell frequency. In this report, we have extended these studies to pancreatic cancer and probed the mechanism of action in tumor and stromal cells involved in antitumor efficacy. Experimental Design: Patient-derived pancreatic xenograft tumor models were used to evaluate the antitumor effect of anti-DLL4. To investigate the mechanism of action, we compared the activity of targeting DLL4 in tumor cells with an anti-human DLL4 antibody (anti-hDLL4) and in the host stroma/vasculature with an anti-mouse DLL4 antibody (anti-mDLL4). The effect of these antibodies on cancer stem cell frequency was examined by in vivo limiting dilution assays. Results: The combination of anti-hDLL4 and anti-mDLL4 was efficacious in a broad spectrum of pancreatic tumor xenografts and showed additive antitumor activity together with gemcitabine. Treatment with either anti-hDLL4 or anti-mDLL4 delayed pancreatic tumor recurrence following termination of gemcitabine treatment, and the two together produced an additive effect. Anti-hDLL4 had a pronounced effect in reducing the tumorigenicity of pancreatic cancer cells based on serial transplantation and tumorsphere assays. In contrast, disruption of tumor angiogenesis with anti-mDLL4 alone or with anti-VEGF had minimal effects on tumorigenicity. Gene expression analyses indicated that anti-DLL4 treatment regulated genes that participate in Notch signaling, pancreatic differentiation, and epithelial-to-mesenchymal transition. Conclusions: Our findings suggest a novel therapeutic approach for pancreatic cancer treatment through antagonism of DLL4/Notch signaling. Clin Cancer Res; 18(19); 5374–86. ©2012 AACR.

The Wnt/β-catenin pathway, which signals through the Frizzled (Fzd) receptor family and several coreceptors, has long been implicated in cancer. Here we demonstrate a therapeutic approach to targeting the Wnt pathway with a monoclonal antibody, OMP-18R5. This antibody, initially identified by binding to Frizzled 7, interacts with five Fzd receptors through a conserved epitope within the extracellular domain and blocks canonical Wnt signaling induced by multiple Wnt family members. In xenograft studies with minimally passaged human tumors, this antibody inhibits the growth of a range of tumor types, reduces tumor-initiating cell frequency, and exhibits synergistic activity with standard-of-care chemotherapeutic agents.

Clinical management of pancreatic cancer is challenging and in recent years has not been dramatically improved and this disease remains the fourth most common cause of cancer-related death. Dysregulated Notch2 and/or Notch3 activity has been associated with several human tumor types including pancreatic cancer. In this report, we describe the development of OMP-59R5, an antibody isolated originally by binding to Notch2 and subsequently found to also bind Notch3. OMP-59R5 potently blocks Notch2 and Notch3 signaling and inhibits the growth pancreatic cancer patient derived xenograft tumors, as a single agent and in combination with gemcitabine. The anti-tumor effects were associated with modulation of Notch target genes in tumor and stromal cells. Inclusion of OMP-59R5 delayed pancreatic tumor recurrence following termination of gemcitabine, correlated with an effect of anti-Notch2/3 in decreasing in cancer stem cell frequency and tumorigenicity. Gene set enrichment analysis showed that a subset of the stem cell gene sets and gene set related to epithelial-to-mesenchymal transistion, EMT, was up-regulated in tumors by gemcitabine alone, but down-regulated by the combination of gemcitabine plus OMP-59R5 treatment. Findings from the present study suggest that agents that reduce cancer cell frequency may improve cancer treatment by delaying or preventing tumor recurrence, and reducing the metastatic spread of the disease. In particular, blocking Notch-mediated proliferation of bulk tumor cells and cancer stem cells may provide an attractive strategy for novel therapy in pancreatic cancer treatment. Citation Format: Wan-Ching Yen, Marcus Fischer, Aaron Sato, Min Wang, Ann M. Kapoun, John Lewicki, Austin Gurney, Timothy Hoey. Targeting Notch signaling with a dual Notch 2/3 antagonist, OMP-59R5, inhibits tumor growth and decreases cancer stem cell frequency in pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Progress and Challenges; Jun 18-21, 2012; Lake Tahoe, NV. Philadelphia (PA): AACR; Cancer Res 2012;72(12 Suppl):Abstract nr B44.