Abstract 3283: GEN1046 (DuoBody®-PD-L1x4-1BB) in combination with PD-1 blockade potentiates anti-tumor immunity

GEN1046 (DuoBody®-PD-L1x4-1BB) is an investigational, potential first-in-class bispecific immunomodulatory antibody designed to elicit an anti-tumor immune response by simultaneous and complementary blockade of PD-L1 on tumor or immune cells and conditional 4-1BB stimulation on T cells and NK cells. Previously, we described encouraging preclinical and early clinical activity of GEN1046 (Muik, et al., 2022, Cancer Discovery). We hypothesized that combining GEN1046 with PD-1 blockade would further potentiate anti-tumor activity through distinct and complementary immune modulatory effects. Addition of an anti-PD-1 agent would free up PD-L1 for binding to GEN1046, thus promoting PD-L1-dependent 4-1BB conditional agonism, while maintaining complete blockade of the PD-1 pathway by inhibiting interactions with both PD-L1 and PD-L2. ​Here we provide preclinical evidence supportive of therapeutic synergy by the combination of GEN1046 and anti-PD-1 and describe the mechanisms of enhanced anti-tumor immunity elicited by the combination. In in vitro studies, combining GEN1046 with an anti-PD-1 agent potentiated cytokine release in mixed lymphocyte reaction assays (using either unstimulated T cells or T cells exhausted by repeated CD3/CD28 co-stimulation) and enhanced T-cell expansion and cytokine secretion in antigen-specific proliferation assays compared to each single agent. In in vivo studies in mice bearing syngeneic subcutaneous MC38 tumors, the combination of an anti-mouse PD-L1x4-1BB bispecific antibody with anti-mouse PD-1 potentiated anti-tumor activity with significant enhancement of survival (P≤0.001) and durable, complete tumor regressions (CR) in 7/10 mice compared to no CR observed with either single agent, suggesting therapeutic synergy with the combination. The combination treatment elicited long-lasting immune memory response, as animals with CR were protected from tumor outgrowth upon rechallenge with MC38 cells. Mechanistically, animals treated with the combination showed a trend for ≥1.5-fold increase in the average density of CD3+ and CD4+ tumor-infiltrating lymphocytes (TILs), as well as proliferating (Ki67+) and cytotoxic (GZMB+) CD8+ TILs relative to each single agent, consistent with an amplified anti-tumor immune response. Together, these preclinical results suggest that combining GEN1046-induced conditional 4-1BB stimulation with complete PD-1 blockade can improve the anti-tumor immune response via distinct and complementary immune modulatory effects. The combination of GEN1046 with pembrolizumab is currently being investigated in ongoing clinical studies in patients with advanced NSCLC, who are treatment-naïve (NCT03917381) or have progressed on prior CPI-containing therapy (NCT05117242).

Citation Format: Michela Capello, Angelica Sette, Theo Plantinga, Vanessa Spires, Kristina Nuermberger, Jordan Blum, Alexander Muik, Carol Costa Sa, Omar Jabado, Saskia Burm, Aras Toker, Sina Fellermeier-Kopf, Tahi Ahmadi, Brandon Higgs, Suzana Couto, Özlem Türeci, Mark Fereshteh, Ugur Sahin, Maria Jure-Kunkel, Nora Pencheva. GEN1046 (DuoBody®-PD-L1x4-1BB) in combination with PD-1 blockade potentiates anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3283.

Abstract 5442: SlideQC: An AI-based tool for automated quality control of whole-slide digital pathology images

Introduction: Artifacts are often introduced during tissue collection and processing, slide preparation, and/or when generating whole slide images (WSI). The presence of artifacts has a negative impact on the digital pathology workflow as artifacts may hinder diagnostic reporting and can lead to false positive and false negative results when using image analysis algorithms or computer-aided diagnosis systems. Manual quality control of WSI is a time-consuming procedure and therefore automated quality control tools, which report and exclude artifacts, are highly desirable to streamline digital pathology workflows. To automate the quality control step, we developed SlideQC, an AI-based quality control tool that automatically detects, reports, and outlines artifacts such as air bubbles, dust/debris, folds, out-of-focus,and pen marks, in both research and clinical workflows. Methods: SlideQC was trained with a DenseNet-based network using 1984 annotations for artifacts including air bubbles, dust/debris, folds, out-of-focus, and pen markers, across 254 Haematoxylin and Eosin (H&E) stained WSI from more than 9 tissue types. A set of 2048 annotations from synthetically generated out-of-focus images was added to supplement the training data. The performance of the SlideQC was evaluated on an external test cohort of 49 WSI H&E images sourced from the open-source database ‘HistoQCRepo’, across 375 annotations (tissue and artifact), and compared with the performance of HistoQC, an open-source quality control tool for digital pathology slides. Results: On the external test cohort, SlideQC showed high sensitivity, specificity, and F1-score with average values of 0.93, 0.99, and 0.93, across the five artifact types. In the same cohort, HistoQC attained an average sensitivity, specificity, and F1-score of 0.65, 0.79, and 0.54, respectively. Conclusions: SlideQC achieved high sensitivity, specificity, and F1-score on an external test cohort. SlideQC can add efficiency gains to a workflow by performing quality control on 100% of slides rather than the currently manually performed on only a subset of the slides in clinical pathology departments. SlideQC can allowthe triaging and alerting of slides containing a high level of artifact within a digital pathology workflow. The tool can also be used to exclude the artifact region from downstream analysis by subsequent image analysis algorithms.

Citation Format: Daniela Rodrigues, Stefan Reinhard, Therese Waldburger, Daniel Martin, Suzana Couto, Inti Zlobec, Peter Caie, Erik Burlingame. SlideQC: An AI-based tool for automated quality control of whole-slide digital pathology images. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5442.

A Novel BCMA Immunohistochemistry Assay Reveals a Heterogenous and Dynamic BCMA Expression Profile in Multiple Myeloma

B-cell maturation antigen (BCMA) is a promising target for the treatment of multiple myeloma (MM) because the expression of this protein is largely limited to B-cell sets, plasma cells, MM, and other B-cell malignancies. Early studies assessing BCMA protein expression and localization have used insufficiently qualified immunohistochemistry assays, which have reported broad ranges of BCMA expression. As a result, our understanding of BCMA tissue expression derived from these data is limited, specifically the prevalence of BCMA expression on the cell surface/membrane, which has mechanistic relevance to the antimyeloma activity of several novel biotherapeutics. Here, we report on the qualification and application of a novel anti-BCMA immunohistochemistry antibody, 805G12. This antibody shows robust detection of BCMA in formalin-fixed, decalcified bone marrow tissue and provides key insights into membrane BCMA expression. The clone 805G12, which was raised against an intracellular C-terminal domain peptide of membrane BCMA, exhibited increased sensitivity and superior specificity across healthy and diseased tissue compared with the frequently referenced commercial reagent AF193. The new clone also demonstrated a broad range of expression of BCMA in MM and diffuse large B-cell lymphoma specimens. Additionally, cross-reactivity with closely related tumor necrosis factor receptor family members was observed with AF193 but not with 805G12. Furthermore, via established 805G12 and other independent BCMA assays, it was concluded that proteolytic processing by γ-secretase contributes to the levels of BCMA localized to the plasma membrane. As BCMA-directed therapeutics emerge to address the need for more effective treatment in the relapsed or refractory MM disease setting, the implementation of a qualified assay would ensure that reliable and consistent data on BCMA surface expression are used to inform clinical trial decisions and patient responses.

Abstract 459: Identification of the PDAC immunogenic subtype using deep learning with multi-scaled digital H&E images

Background: Pancreatic ductal adenocarcinoma (PDAC) has proven a difficult cancer to treat. To improve treatment strategies, molecular subtypes have been identified, one being immunogenic with significant immune infiltrate and better prognosis. These subtypes have been determined by RNA profiling, which often exhibits technical challenges in a clinical setting. Here we present a deep learning-based method to identify PDAC immunogenic patients using H&E images. This method is robust to RNA quality issues and can elucidate unique morphological features not obtainable with RNA profiling to refine the selection of patients with this phenotype.

Methods: Patients (n=265) were primarily stage II or IV, treated previously with gemcitabine+nab-paclitaxel or FOLFIRINOX. Ground truth for immunogenic subtype (n=105) was defined with RNASeq. Whole slide images were subdivided into non-overlapping, fixed-size tiles at 4 magnifications: 2.5x, 5x, 10x, 20x, followed by feature extraction using a ResNet50 convolutional neural network. Principal component (PC) analysis reduced dimensionality of extracted features in each tile. The dataset was split into 80% training, 20% testing. Posterior probabilities from a linear model were inputs to a support vector machine to predict outcome (2-step model). Progression- free survival (PFS) was evaluated using the Kaplan Meier method.

Results: ImageNet-trained ResNet50 model extracted 2048 features from each tile and the first 75 PCs, explaining 87% variance, were input into the 2-step model; average AUC=0.77 (95% CI=0.70,0.83) across the 4 magnification datasets. A multi-scale ensemble approach combining these 4 magnifications improved the AUC to 0.80 (95% CI=0.66,0.93). Accuracy, sensitivity, and specificity were 0.79, 0.76, and 0.81, respectively. The predicted immunogenic subtype showed significantly improved PFS compared to the other 3 subtypes (HR 95%CI = 0.54 (0.36,0.81), p=0.003), while the RNASeq-derived immunogenic subtype had less differentiation (HR 95%CI = 0.64 (0.42,0.98), p=0.04).

Conclusions: This study presents a deep learning 2-step model approach using tumor H&E images to identify PDAC immunogenic subtype, with improved prognostic potential to that identified by RNA profiling, suggesting possible application in clinical settings for patient stratification. Future work will expand the model to larger independent cohorts.

Citation Format: Han Si, Steven Xu, Anantharaman Muthuswamy, Ryan Liang, Kate Sasser, Hisham K. Hamadeh, Suzana Couto, Brandon Higgs. Identification of the PDAC immunogenic subtype using deep learning with multi-scaled digital H&E images [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 459.

Abstract 2034: Spatial transcriptomics identifies unique pharmacodynamic effects of checkpoint inhibitor treatment on the tumor microenvironment in NSCLC

Background: Immune checkpoint inhibitor (ICI) therapy has improved outcomes in non-small cell lung cancer (NSCLC), particularly in patients with high tumor infiltrating lymphocytes (TILs). Identifying the pharmacodynamic (PD) impact of ICI on immune cells in the tumor microenvironment (TME) can inform therapeutic development for patients with progressive disease. We sought to identify PD changes in the TME from patients before and after ICI therapy using a spatial transcriptomics platform that allows highly multiplexed profiling of 1,800 genes (Nanostring Digital Spatial Profiler [DSP]).

Methods: Formalin fixed, paraffin embedded (FFPE) tumor tissue from 22 patients was sourced commercially. Patients were treated with neoadjuvant chemotherapy, then underwent a surgical tumor resection. After surgery an adjuvant chemotherapy was administered until progression; patients then received monotherapy ICI (nivolumab or pembrolizumab). Once progressed on ICI, another resection was performed. Patients were then treated with chemotherapy and followed until progression and/or death. The DSP technology was used to independently profile RNA from PanCK+ (tumor) and PanCK- (stroma) regions in the tissue based on fluorescence staining. Six circular regions of 600μm in diameter were selected for analysis using the GeoMx instrument; each area contained CD3+ cells. Additionally, immunohistochemistry for PDL1 and CD3 was performed, images were scored by a pathologist and analyzed with digital pathology algorithms.

Results: Spatial transcriptomic analysis of pre- vs post-ICI treatment in stroma revealed significant increases in T cell genes (CD3E, TCRB, NKG7), T-cell activation markers (CD69, IFNG, OX40, GZMB, ICOS), costimulatory signaling (CD28, CD80, CD86), and immune checkpoints (CTLA4, TIGIT). Ayers et al., JCI 2017 identified 28 genes predictive of ICI response, 12 were significantly upregulated in the stroma post-ICI (26 were present in the DSP panel). We identified genes in the pre-ICI stromal microenvironment that were highly expressed in patients with partial response to ICI, the most significant genes were involved in immune regulation (IFIT1) and extracellular matrix remodeling (MMP3). In contrast, stromal genes highly expressed in patients with progressive disease were associated with T-cell maintenance (ETS1, IL7R, CCL19).

Conclusions: In this study we used spatial transcriptomics to profile tissue regions where T-cells were in close proximity to tumor cells (microns). This focused, local PD analysis confirmed activated T-cells are present post-ICI. Ongoing studies in a larger cohort will be used to identify tumoral mechanisms of resistance and immune dysfunction to inform future therapeutics and combinations.

Citation Format: Li Fan, Omar Jabado, Nora Pencheva, Patricia Coutinho de Souza, Brandon Higgs, Angelo Harris, Patrick Franken, Anantharaman Muthuswamy, Maria Jure-Kunkel, Suzana Couto, Kate Sasser, Mark Fereshteh. Spatial transcriptomics identifies unique pharmacodynamic effects of checkpoint inhibitor treatment on the tumor microenvironment in NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2034.

DLBCL cell of origin typing and whole transcriptome analysis using single slides with HTG EdgeSeq

7576

Background: Diffuse large B-cell Lymphoma (DLBCL) is a highly heterogenous disease. Gene microarrays were initially used to classify DLBCL into germinal center B-cell-like (GCB) or activated B-cell-like (ABC) Cell of Origin (COO) subtypes. ABC is associated with shorter overall survival. In newly diagnosed patients, COO classification by RNA profiling is a validated prognostic. A simpler immunohistochemical (IHC) staining of CD10, MUM1 and BCL6 is a proxy used in clinical practice in lieu of transcriptomics due to its expense, complexity and tissue requirements. Recent advances in the HTG EdgeSeq platform allow genome-scale profiling with minimal tissue. We successfully applied this novel technology to perform simultaneous COO classification, immune cell enrichment and tumor pathway analysis using a single FFPE slide. Methods: Accuracy of the HTG EdgeSeq panel (19,000 genes) was assessed in a head-to-head comparison with RNAseq using FFPE tumor samples (n = 8). DLBCL resections and core needle biopsies were commercially sourced and COO typed using Han’s algorithm into GCB or non-GCB (n = 65). Tumor locations included: lymphoid organs, gastrointestinal tract, testes, and the pleural cavity. EdgeSeq was performed on single slides with an average tissue area of 40mm2. Transcriptomic COO classification was performed using a linear combination of genes as described in Wright et al., PNAS 2003, substituting HTG platform-specific weights. Validated COO gene sets from literature and commercial diagnostic assays were tested. Immune cell gene signature enrichment analysis was performed using xCell (Aran et al., Genome Biol 2017); pathway analysis was performed with GSEA (Subramanian et al., PNAS 2005). Results: Gene expression levels estimated from whole transcriptome EdgeSeq on single slides were highly correlated to whole transcriptome RNAseq. Differential expression analysis of GCB vs non-GCB showed that key prognostic genes were detectable and enriched in the expected subtypes. Using these pre-established signatures, subtyping accuracy was ̃93% on the training set and 89% on the test set. Immune cell enrichment analysis identified class-switched memory B-cells as more prevalent in non-GCB subjects. This is consistent with emerging evidence that memory B-cells are the primary source of ABC DLBCL and not plasma cells (Venturutti & Melnick, Blood 2020). Pathway analysis identified genes regulated by the oncogene ic transcription factor MYC were enriched in non-GCB samples; MYC protein was found to be overexpressed in ABC in a large study (Hu et al., Blood 2013). Conclusions: Combined COO typing and whole transcriptome analysis from a single slide efficiently uses precious patient tissue. Longitudinal core needle sampling may yield insights into tumor evolution and therapeutic mechanisms of action across the DLBCL treatment landscape.

833 A scalable deep learning framework for rapid automated annotation of histologic and morphologic features from large unlabeled pan-cancer H&E datasets

Background

Recent advances in machine learning and digital pathology have enabled a variety of applications including predicting tumor grade and genetic subtypes, quantifying the tumor microenvironment (TME), and identifying prognostic morphological features from H&E whole slide images (WSI). These supervised deep learning models require large quantities of images manually annotated with cellular- and tissue-level details by pathologists, which limits scale and generalizability across cancer types and imaging platforms. Here we propose a semi-supervised deep learning framework that automatically annotates biologically relevant image content from hundreds of solid tumor WSI with minimal pathologist intervention, thus improving quality and speed of analytical workflows aimed at deriving clinically relevant features.

Methods

The dataset consisted of >200 H&E images across >10 solid tumor types (e.g. breast, lung, colorectal, cervical, and urothelial cancers) from advanced disease patients. WSI were first partitioned into small tiles of 128μm for feature extraction using a 50-layer convolutional neural network pre-trained on the ImageNet database. Dimensionality reduction and unsupervised clustering were applied to the resultant embeddings and image clusters were identified with enriched histological and morphological characteristics. A random subset of representative tiles (<0.5% of whole slide tissue areas) from these distinct image clusters was manually reviewed by pathologists and assigned to eight histological and morphological categories: tumor, stroma/connective tissue, necrotic cells, lymphocytes, red blood cells, white blood cells, normal tissue and glass/background. This dataset allowed the development of a multi-label deep neural network to segment morphologically distinct regions and detect/quantify histopathological features in WSI.

Results

As representative image tiles within each image cluster were morphologically similar, expert pathologists were able to assign annotations to multiple images in parallel, effectively at 150 images/hour. Five-fold cross-validation showed average prediction accuracy of 0.93 [0.8–1.0] and area under the curve of 0.90 [0.8–1.0] over the eight image categories. As an extension of this classifier framework, all whole slide H&E images were segmented and composite lymphocyte, stromal, and necrotic content per patient tumor was derived and correlated with estimates by pathologists (p<0.05).

Conclusions

A novel and scalable deep learning framework for annotating and learning H&E features from a large unlabeled WSI dataset across tumor types was developed. This automated approach accurately identified distinct histomorphological features, with significantly reduced labeling time and effort required for pathologists. Further, this classifier framework was extended to annotate regions enriched in lymphocytes, stromal, and necrotic cells – important TME contexture with clinical relevance for patient prognosis and treatment decisions.

516 Peripheral and tumoral immune activity in the expansion part of the first-in-human DuoBody®-PD-L1×4–1BB (GEN1046) trial

Background

DuoBody-PD-L1×4-1BB (GEN1046) is a class-defining, bispecific immunotherapy designed to induce an antitumor immune response by simultaneous and complementary PD-L1 blockade and conditional 4-1BB stimulation. Encouraging clinical activity and manageable safety were observed during dose escalation in the ongoing phase 1/2a trial in patients with advanced solid tumors (NCT03917381). We report exploratory pharmacodynamic analyses and potential biomarkers of response in an expansion cohort of patients with PD-(L)1–R/R NSCLC.

Methods

Patients with metastatic/unresectable NSCLC who had multiple lines of prior systemic therapy, including a checkpoint inhibitor, received flat-dose DuoBody-PD-L1×4-1BB (100 mg) intravenously every 3 weeks. Immunophenotyping of peripheral blood and measurements of soluble immune mediators were evaluated in serial blood samples in cycles 1–2. Tumor PD-L1 and 4-1BB expression and additional immune markers were evaluated by immunohistochemistry in core needle tumor biopsy specimens collected before treatment and at cycle 2.

Results

As of May 2021, 40 patients with PD-(L)1–R/R NSCLC were enrolled (median age, 63 years). Treatment with DuoBody-PD-L1×4-1BB elicited pharmacodynamic modulation of immune endpoints within the first 2 cycles. Induction of peripheral IFN-y, CXCL9/10, and expansion of peripheral CD8+ effector memory T cells and activated NK cells were observed starting at cycle 1 (>2-fold from baseline) and maintained or increased through cycle 2. Based on 9 paired tumor biopsy samples, increased PD-L1 and 4-1BB expression and cytotoxic CD8+/GZMB+ cell density were detected following treatment. In a subset of patients with clinical response (n=5 confirmed PRs), a trend of greater induction of IFN-y, CXCL9/10, and activated NK cells was observed vs nonresponders. Disease control rates were higher in patients who had progressed on prior anti–PD-1 therapy within 8 months (64% [16/25]) from the first dose of DuoBody-PD-L1×4-1BB. As expected, among patients with evaluable baseline tumors (n=26), most with any degree of tumor reduction (best change, <0%) harbored PD-L1+ tumors (≥1% tumor positive score; 7/10) and showed close spatial proximity between PD-L1+ and 4-1BB+ cells. Conversely, most patients without any degree of tumor reduction presented with PD-L1− tumors (12/16).

Conclusions

In patients with NSCLC who progressed on PD-(L)1 therapy, DuoBody-PD-L1×4-1BB elicited pharmacodynamic effects consistent with its proposed mechanism of action. Relationships between disease control and PD-L1 tumoral expression, as well as time from last prior anti–PD-1 therapy, were observed. These findings support that patient selection and/or anti–PD-1 combination therapy may lead to improved clinical efficacy. Further analyses are ongoing and updated results will be presented.

Acknowledgements

The authors thank Hrefna Kristin Johannsdottir, Lei Pang, and Kate Sasser at Genmab A/S and Friederike Gieseke at BioNTech SE for their valuable contributions. This trial was funded by Genmab A/S and BioNTech SE.

Trial Registration

NCT03917381

Ethics Approval

This trial is undertaken following full approval of the final protocol, amendments, informed consent form, applicable recruiting materials, and subject compensation programs by the Independent Ethics Committee/Institutional Review Board.

Consent

Written informed consent, in accordance with principles that originated in the Declaration of Helsinki 2013, current ICH guidelines including ICH-GCP E6(R2), applicable regulatory requirements, and sponsor policy, was provided by the patients.

928 A translational approach to catalog pancreatic cancer heterogeneity using spatial genomics in large patient cohorts for target validation and rational combination selection

Background

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with short overall survival; the standard of care (SoC) is chemotherapy. Immunotherapies in development aim to remodel the stroma by depleting immunosuppressive cell types or using T-cell redirection to kill tumor cells. To date, none of these methods have improved overall survival beyond SoC. Next generation immunotherapies that employ histopathology and molecular subtyping1 for target and patient selection may succeed. Here we leverage a spatial transcriptomics platform (Nanostring Digital Spatial Profiling, DSP) to reveal molecular signaling in tumoral and stromal cells in 57 PDAC patients using tumor microarrays (TMAs). This approach is rapid and clinically relevant as molecular and histology data can be easily bridged.

Methods

TMAs generated from surgical resection tissue were commercially sourced. DSP was performed using the CTA RNA panel (1,800 target genes) using PanCK fluorescence for tumor/stroma segmentation. In parallel, slides were chromogenically stained for T-cells (CD3) and macrophages (CD68/CD163). Differential gene expression, gene signature and gene co-expression network analysis was performed using linear models in R.2 3

Results

Differential gene expression analysis and correlation to IHC confirmed the DSP platform successfully profiled tumor and stromal compartments (figure 1). Immune cell signatures4 and pathway analysis revealed a heterogenous stromal environment. Using a fibroblast gene signature derived from single-cell RNAseq5 we found fibroblast density was positively correlated to PDGFR signaling and MHC-II expression but negatively correlated to B, CD4+ T and neutrophil cell levels (figure 2a). This finding supports the idea that atypical antigen presentation in cancer associated fibroblasts (CAFs) may be exploitable for immunotherapies.6 We constructed a co-expression network from in-situ stromal gene expression and used it to identify receptors coordinately expressed with the immunosuppressive macrophage marker CSF1R as a bispecific antibody partner (figure 2b).7 Classical macrophage markers were identified but also receptors with lesser-known functions in macrophages (TIM3/HAVCR2, FPR3, MS4A6A, LILRB4). Surveying target pairs in this method allows rapid, patient-specific confirmation in serial TMA sections with singleplex IHC or RNAscope.

Abstact 928 Figure 1

Segmentation strategy and validation of DSP (A) PanCK, CD68 and CD3 staining from two representative tumor cores; (B, C) correlation of gene transcripts in stroma to cell counts from chromogenic staining; (D) heatmap of selected genes differentially expressed in tumor and stroma (n=57 patients).

Abstract 928 Figure 2

Exploration of the stromal compartment in PDAC TMAs. (A) Heatmap of selected cell type and gene signatures from gene expression in the stroma, color represents single sample enrichment score using GSVA method; (B) a gene co-expression subnetwork in the stroma centered on CSF1R, edge thickness represents strength of correlation, green nodes have evidence for cell surface expression based on proteomic profiling.7

Conclusions

In this study we were able to recapitulate known PDAC biology using very small samples of primary tumors. The combination of TMAs and DSP enables a rapid validation of targets and hypothesis generation for bispecific parings. Further analysis of untreated (n=14) and post-adjuvant chemotherapy (n=26) patients using RNA DSP, IHC and bulk RNAseq is under way. Results from this cohort will enable an integrated histopathology and molecular approach to developing next-generation immunotherapies.

References

Collisson EA, Bailey P, Chang DK, Biankin AV. Molecular subtypes of pancreatic cancer. Nat Rev Gastroenterol Hepatol 2019 April;16(4):207–220.

Ritchie ME, Phipson B, Wu D, Hu Y, Law CW, Shi W, Smyth GK (2015). “limma powers differential expression analyses for RNA-sequencing and microarray studies.” Nucleic Acids Research 43(7):e47.

Hänzelmann S, Castelo R, Guinney J (2013). “GSVA: gene set variation analysis for microarray and RNA-Seq data.” BMC Bioinformatics 14,7.

Charoentong P, Finotello F, Angelova M, Mayer C, Efremova M, Rieder D, Hackl H, Trajanoski Z. Pan-cancer immunogenomic analyses reveal genotype-immunophenotype relationships and predictors of response to checkpoint blockade. Cell Rep 2017 January 3;18(1):248–262.

Tirosh I, Izar B, Prakadan SM, Wadsworth MH 2nd, Treacy D, Trombetta JJ, Rotem A, Rodman C, Lian C, Murphy G, Fallahi-Sichani M, Dutton-Regester K, Lin JR, Cohen O, Shah P, Lu D, Genshaft AS, Hughes TK, Ziegler CG, Kazer SW, Gaillard A, Kolb KE, Villani AC, Johannessen CM, Andreev AY, Van Allen EM, Bertagnolli M, Sorger PK, Sullivan RJ, Flaherty KT, Frederick DT, Jané-Valbuena J, Yoon CH, Rozenblatt-Rosen O, Shalek AK, Regev A, Garraway LA. Dissecting the multicellular ecosystem of metastatic melanoma by single-cell RNA-seq. Science 2016 April 8;352(6282):189–96.

Elyada E, Bolisetty M, Laise P, Flynn WF, Courtois ET, Burkhart RA, Teinor JA, Belleau P, Biffi G, Lucito MS, Sivajothi S, Armstrong TD, Engle DD, Yu KH, Hao Y, Wolfgang CL, Park Y, Preall J, Jaffee EM, Califano A, Robson P, Tuveson DA. Cross-species single-cell analysis of pancreatic ductal adenocarcinoma reveals antigen-presenting cancer-associated fibroblasts. Cancer Discov 2019 August;9(8):1102–1123.

Bausch-Fluck D, Hofmann A, Bock T, Frei AP, Cerciello F, Jacobs A, Moest H, Omasits U, Gundry RL, Yoon C, Schiess R, Schmidt A, Mirkowska P, Härtlová A, Van Eyk JE, Bourquin JP, Aebersold R, Boheler KR, Zandstra P, Wollscheid B. A mass spectrometric-derived cell surface protein atlas. PLoS One 2015 April 20;10(3):e0121314.

Ethics Approval

Specimens were harvested from unused tissue after a surgical tumor resection procedure. A discrete legal consent form from both hospital and individuals was obtained by the commercial tissue vendor BioMax US for all samples analyzed in this abstract. All human tissues are collected under HIPPA approved protocols.

Consent

Written informed consent was obtained from the patient for publication of this abstract and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.

Targeting the Wnt signaling pathway through R-spondin 3 identifies an anti-fibrosis treatment strategy for multiple organs

The Wnt/β-catenin signaling pathway has been implicated in human proliferative diseases such as cancer and fibrosis. The functions of β-catenin and several other components of this pathway have been investigated in fibrosis. However, the potential role of R-spondin proteins (RSPOs), enhancers of the Wnt/β-catenin signaling, has not been described. A specific interventional strategy targeting this pathway for fibrosis remains to be defined. We developed monoclonal antibodies against members of the RSPO family (RSPO1, 2, and 3) and probed their potential function in fibrosis in vivo. We demonstrated that RSPO3 plays a critical role in the development of fibrosis in multiple organs. Specifically, an anti-RSPO3 antibody, OMP-131R10, when dosed therapeutically, attenuated fibrosis in carbon tetrachloride (CCl₄)-induced liver fibrosis, bleomycin-induced pulmonary and skin fibrosis models. Mechanistically, we showed that RSPO3 induces multiple pro-fibrotic chemokines and cytokines in Kupffer cells and hepatocytes. We found that the anti-fibrotic activity of OMP-131R10 is associated with its inhibition of β-catenin activation in vivo. Finally, RSPO3 was found to be highly elevated in the active lesions of fibrotic tissues in mouse models of fibrosis and in patients with idiopathic pulmonary fibrosis (IPF) and nonalcoholic steatohepatitis (NASH). Together these data provide an anti-fibrotic strategy for targeting the Wnt/β-catenin pathway through RSPO3 blockade and support that OMP-131R10 could be an important therapeutic agent for fibrosis.

Abstract A43: Spatial organization of pancreatic ductal adenocarcinoma (PDAC)–associated immune cells from the Adjuvant Pancreatic Adenocarcinoma Clinical Trial (APACT) study

Introduction: It is strikingly difficult to develop successful treatments for PDAC; even with curative resection, most patients die from early occult metastases. Prior studies identified the presence of tumor-infiltrating lymphocytes (TILs) in primary PDAC tumors as having prognostic significance in the PDAC adjuvant setting, sharpening the questions of what fraction of patients have immune-infiltrated tumors and what therapeutic strategies should be pursued in these patients vs. the non-infiltrated group. The phase 3 APACT trial evaluated the use of adjuvant nab-paclitaxel plus gemcitabine vs. gemcitabine in 866 patients with PDAC who had undergone primary tumor resection, with the primary endpoint of disease-free survival evaluated by independent review. We extended studies of the tumor microenvironment of PDAC to a large set of resected APACT primary tumors in an effort to further refine features of tumor or immune infiltrate that influence disease progression and to determine if chemotherapy regimen–specific predictive signatures are identifiable. Tissue analyses for a large subset of APACT samples included RNA-seq, DNA-seq, multiplexed immunohistochemistry (IHC), and proteomics.

Methods: We imaged and quantified markers for tumor cells, 7 different immune cells, and 2 immune checkpoint markers using bright-field chromogenic multiplexed IHC from pretreatment samples for more than 500 APACT primary tumor samples. We computationally defined the tumor, tumor margin, and distal stromal (&gt; 150 μm from tumor boundary) regions, and quantified densities and distributions of immune cells in these regions. As part of an initial analysis of more than 400 samples, we applied both unsupervised clustering and supervised classification to these IHC measurements to identify patient subgroups with similar spatial arrangements of immune cells relative to tumor regions.

Results: The preliminary analysis of normalized cell densities across all 3 tissue regions revealed 3 patient subgroups: one in which immune cells are mixed within the tumor regions; a second where immune cells approach the tumor boundary but are depleted within the tumor; and a third in which immune cells are depleted in both tumor and its margin, remaining at high densities only in the distal stromal regions. Within these latter subgroups, CD20+, CD4+, and CD8+ cells were more prevalently depleted from tumor and/or margin, whereas CD163+ and CD163+CMAF+ cells showed less of this arrangement. Nearly 85% of patients fell in the second or third patient group.

Conclusions: We are pursuing analyses of these data in conjunction with upcoming molecular and genetic profiling data to further elucidate the association of the immune cell populations and these subgroups with clinical outcomes. These data will provide an unprecedented opportunity for exploratory analysis and discovery of immune, molecular, and genetic biomarkers for PDAC patient stratification.

Citation Format: David J. Reiss, Thomas Lila, Suzana Couto, Sitharthan Kamalakaran, Yan Ren, Doug Bowman, Amber Ortiz, Maria Wang, Clifton Drew, Kao-Tai Tsai, Mathieu Marella, Brian Fox, Garth McGrath, Matthew Trotter, Fadi Towfic, Ian Cushman, Alexander Ratushny, Brian Lu, Daniel Pierce, Jim Cassidy. Spatial organization of pancreatic ductal adenocarcinoma (PDAC)–associated immune cells from the Adjuvant Pancreatic Adenocarcinoma Clinical Trial (APACT) study [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr A43.

UBE2G1 governs the destruction of cereblon neomorphic substrates

The cereblon modulating agents (CMs) including lenalidomide, pomalidomide and CC-220 repurpose the Cul4-RBX1-DDB1-CRBN (CRL4^CRBN) E3 ubiquitin ligase complex to induce the degradation of specific neomorphic substrates via polyubiquitination in conjunction with E2 ubiquitin-conjugating enzymes, which have until now remained elusive. Here we show that the ubiquitin-conjugating enzymes UBE2G1 and UBE2D3 cooperatively promote the K48-linked polyubiquitination of CRL4^CRBN neomorphic substrates via a sequential ubiquitination mechanism. Blockade of UBE2G1 diminishes the ubiquitination and degradation of neomorphic substrates, and consequent antitumor activities elicited by all tested CMs. For example, UBE2G1 inactivation significantly attenuated the degradation of myeloma survival factors IKZF1 and IKZF3 induced by lenalidomide and pomalidomide, hence conferring drug resistance. UBE2G1-deficient myeloma cells, however, remained sensitive to a more potent IKZF1/3 degrader CC-220. Collectively, it will be of fundamental interest to explore if loss of UBE2G1 activity is linked to clinical resistance to drugs that hijack the CRL4^CRBN to eliminate disease-driving proteins.

Advanced modelling of the transport phenomena across horizontal clothing microclimates with natural convection

The ability of clothing to provide protection against external environments is critical for wearer's safety and thermal comfort. It is a function of several factors, such as external environmental conditions, clothing properties and activity level. These factors determine the characteristics of the different microclimates existing inside the clothing which, ultimately, have a key role in the transport processes occurring across clothing. As an effort to understand the effect of transport phenomena in clothing microclimates on the overall heat transport across clothing structures, a numerical approach was used to study the buoyancy-driven heat transfer across horizontal air layers trapped inside air impermeable clothing. The study included both the internal flow occurring inside the microclimate and the external flow occurring outside the clothing layer, in order to analyze the interdependency of these flows in the way heat is transported to/from the body. Two-dimensional simulations were conducted considering different values of microclimate thickness (8, 25 and 52 mm), external air temperature (10, 20 and 30 °C), external air velocity (0.5, 1 and 3 m s(-1)) and emissivity of the clothing inner surface (0.05 and 0.95), which implied Rayleigh numbers in the microclimate spanning 4 orders of magnitude (9 × 10(2)-3 × 10(5)). The convective heat transfer coefficients obtained along the clothing were found to strongly depend on the transport phenomena in the microclimate, in particular when natural convection is the most important transport mechanism. In such scenario, convective coefficients were found to vary in wavy-like manner, depending on the position of the flow vortices in the microclimate. These observations clearly differ from data in the literature for the case of air flow over flat-heated surfaces with constant temperature (which shows monotonic variations of the convective heat transfer coefficients, along the length of the surface). The flow patterns and temperature fields in the microclimates were found to strongly depend on the characteristics of the external boundary layer forming along the clothing and on the distribution of temperature in the clothing. The local heat transfer rates obtained in the microclimate are in marked contrast with those found in the literature for enclosures with constant-temperature active walls. These results stress the importance of coupling the calculation of the internal and the external flows and of the heat transfer convective and radiative components, when analyzing the way heat is transported to/from the body.

Abstract 1354: Comparison of pomalidomide dosing strategies in lenalidomide-refractory myeloma: Impact on clinical outcome, immune activation and cereblon targets

In preclinical and mostly in vitro studies, pomalidomide (Pom) has been shown to mediate direct anti-proliferative effects on tumor cells, as well as immune-modulatory effects on T cells, NK cells and monocytes. Cereblon (CRBN), a direct cellular target for Pom has been involved in the anti-proliferative effects in tumor cells via selective degradation of Ikaros (IKZF1) and Aiolos (IKZF3). Depletion of IKZF1/IKZF3 has also been implicated in Len-mediated amplification of anti-CD3-induced IL2 production in human T cells in culture. However the impact of pomalidomide on tumor proliferation and immune activation in vivo is unknown.

Here we have evaluated the clinical and pharmacodynamic effects of continuous or intermittent dosing strategies of pomalidomide/dexamethasone in lenalidomide-refractory myeloma in a randomized trial. 39 eligible patients with relapsed myeloma were randomized to therapy with Pom/Dexamethazone (following Pom alone for cycle 1), utilizing either continuous Pom dosing (2 mg-28/28 days, cohort 1, n = 19) or an intermittent dosing schedule (4 mg-21/28 days, cohort 2, n = 20). Dexamethazone was administered at 40 mg weekly at cycle 2 and beyond.

Intermittent dosing strategy, despite having frequent adverse events, led to greater tumor reduction. Both cohorts experienced similar event-free and overall survival. Both regimens led to a distinct pattern but similar degree of mid-cycle immune activation as manifest by increased expression of cytokines and lytic genes in T and NK cells. Pomalidomide induced polyfunctional T cell activation, with increased proportion of co-inhibitory receptor BTLA+ T cells and Tim-3+ NK cells. Baseline levels of cereblon, ikaros and aiolos protein in tumor cells using validated IHC assay on marrow biopsies, did not correlate with response or survival. Pomalidomide treatment led to a rapid decline in Ikaros in T and NK cells in vivo as measured by intranuclear flow staining, and therapy-induced activation of CD8+ T cells correlated with clinical response.

These data demonstrate that pomalidomide leads to strong and rapid immunomodulatory effects involving both innate and adaptive immunity, even in heavily pre-treated MM, which correlate with clinical anti-tumor effects. Clinicaltrials.gov-NCT01319422.

Citation Format: Rituparna Das, Kartik Sehgal, Lin Zhang, Rakesh Verma, Yanhong Deng, Mehmet Kocoglu, Juan Vasquez, Srini Koduru, Yan Ren, Maria Wang, Suzana Couto, Mike Breider, Donna Hansel, Stuart Seropian, Dennis Cooper, Anjan Thakurta, Xiaopan Yao, Kavita M. Dhodapkar, Madhav V. Dhodapkar. Comparison of pomalidomide dosing strategies in lenalidomide-refractory myeloma: Impact on clinical outcome, immune activation and cereblon targets. [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 1354. doi:10.1158/1538-7445.AM2015-1354

Abstract 5445: Dual-color immunohistochemistry assays for measuring Aiolos and Ikaros proteins in multiple myeloma patient samples

IMiDs® immunomodulatory drugs Lenalidomide (LEN) and Pomalidomide (POM) are antineoplastic agents that have a significant clinical impact in the treatment of patients with multiple myeloma (MM). Recent studies indicate that the anti-proliferative activity of LEN and POM in MM cells is associated with ubiquitination and degradation of the Ikaros family zinc finger protein transcription factors, Aiolos (IKZF3) and Ikaros (IKZF1), the substrates of the Cereblon (CRBN)-dependent Cullin 4 E3-ligase complex. Measurement of Aiolos and Ikaros protein levels in MM patient samples is critical for future correlative studies. Here we describe the development and validation of dual IHC Aiolos/CD138 and Ikaros/CD138 assays using the highly specific Aiolos rabbit monoclonal antibody CGN-9-9-7, and a commercial Ikaros rabbit polyclonal antibody H-100 in combination with a commercial CD138 antibody. Aiolos and Ikaros immunoreactivity in CD138+ MM cells is scored using the semi-quantitative H-score method. H-scores range from 0 to 300 and are the sum of the products of the percentage of tumor cells (0-100%) and the intensity of staining (0-3). The assays were specific and detected high Aiolos and Ikaros expression in the positive control OCI-Ly10 lymphoma cell line, and low Aiolos and Ikaros levels in POM treated OCI-Ly10 cells. These results were confirmed via Western Blot analysis of Aiolos and Ikaros expression data in these cells lines. Assay precision was examined via staining serial sections of the same MM tumor across three different days and deemed acceptable. The dual IHC assays were used to evaluate bone marrow core biopsies or aspirate clots from 22 MM patients and H-scores were determined by a board-certified pathologist. The dual IHC assays detected a wide range of Aiolos or Ikaros immunoreactivity in the 22 MM cases, with nuclear H-scores ranging from 10 to 260 for Aiolos and 40 to 240 for Ikaros. In conclusion, the dual Aiolos/CD138 and Ikaros/CD138 IHC assays were developed to provide a specific and reliable semi-quantitative method to evaluate Aiolos and Ikaros protein levels in both bone marrow core biopsies and clots from MM patients. These assays are currently being used in clinical trials to assess the importance of Aiolos and Ikaros as biomarkers in MM patients treated with IMiDs® immunomodulatory drugs.

Citation Format: Yan Ren, Maria Wang, Suzana Couto, Donna Hansel, Anita K. Gandhi, Patrick Hagner, Anjan Thakurta, Rajesh Chopra, Mike Breider. Dual-color immunohistochemistry assays for measuring Aiolos and Ikaros proteins in multiple myeloma patient samples. [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 5445. doi:10.1158/1538-7445.AM2015-5445

Host genetic background impacts modulation of the TLR4 pathway by RON in tissue-associated macrophages

Toll-like receptors (TLRs) enable metazoans to mount effective innate immune responses to microbial and viral pathogens, as well as to endogenous host-derived ligands. It is understood that genetic background of the host can influence TLR responsiveness, altering susceptibility to pathogen infection, autoimmunity and cancer. Macrophage stimulatory protein (MSP), which activates the receptor tyrosine kinase recepteur d'origine nantais (RON), promotes key macrophage functions such as motility and phagocytic activity. MSP also acts via RON to modulate signaling by TLR4, which recognizes a range of pathogen or endogenous host-derived molecules. Here, we show that RON exerts divergent control over TLR4 activity in macrophages from different mouse genetic backgrounds. RON potently modulated the TLR4 response in macrophages from M2-prone FVB mice, as compared with M1-skewed C57Bl6 mice. Moreover, global expression analysis revealed that RON suppresses the TLR4-dependent type-I interferon gene signature only in FVB macrophages. This leads to attenuated production of the potent inflammatory mediator, tumor necrosis factor-α. Eliminating RON kinase activity markedly decreased carcinogen-mediated tumorigenesis in M2/Th2-biased FVB mice. We propose that host genetic background influences RON function, thereby contributing to the variability in TLR4 responsiveness in rodents and, potentially, in humans. These findings provide novel insight into the complex interplay between genetic context and immune function.

Proapoptotic activation of death receptor 5 on tumor endothelial cells disrupts the vasculature and reduces tumor growth

The proapoptotic death receptor DR5 has been studied extensively in cancer cells, but its action in the tumor microenvironment is not well defined. Here, we uncover a role for DR5 signaling in tumor endothelial cells (ECs). We detected DR5 expression in ECs within tumors but not normal tissues. Treatment of tumor-bearing mice with an oligomeric form of the DR5 ligand Apo2L/TRAIL induced apoptosis in tumor ECs, collapsing blood vessels and reducing tumor growth: Vascular disruption and antitumor activity required DR5 expression on tumor ECs but not malignant cells. These results establish a therapeutic paradigm for proapoptotic receptor agonists as selective tumor vascular disruption agents, providing an alternative, perhaps complementary, strategy to their use as activators of apoptosis in malignant cells.

Androgen hormone action in prostatic carcinogenesis: stromal androgen receptors mediate prostate cancer progression, malignant transformation and metastasis

It has been postulated that prostatic carcinogenesis is androgen dependent and that androgens mediate their effects primarily through epithelial cells; however, definitive proof of androgen hormone action in prostate cancer (PRCA) progression is lacking. Here we demonstrate through genetic loss of function experiments that PRCA progression is androgen dependent and that androgen dependency occurs via prostatic stromal androgen receptors (AR) but not epithelial AR. Utilizing tissue recombination models of prostatic carcinogenesis, loss of AR function was evaluated by surgical castration or genetic deletion. Loss of AR function prevented prostatic carcinogenesis, malignant transformation and metastasis. Tissue-specific evaluation of androgen hormone action demonstrated that epithelial AR was not necessary for PRCA progression, whereas stromal AR was essential for PRCA progression, malignant transformation and metastasis. Stromal AR was not necessary for prostatic maintenance, suggesting that the lack of cancer progression due to stromal AR deletion was not related to altered prostatic homeostasis. Gene expression analysis identified numerous androgen-regulated stromal factors. Four candidate stromal AR-regulated genes were secreted growth factors: fibroblast growth factors-2, -7, -10 and hepatocyte growth factor which were significantly affected by androgens and anti-androgens in stromal cells grown in vitro. These data support the concept that androgens are necessary for PRCA progression and that the androgen-regulated stromal microenvironment is essential to carcinogenesis, malignant transformation and metastasis and may serve as a potential target in the prevention of PRCA.

Three interrelated themes in current breast cancer research: gene addiction, phenotypic plasticity, and cancer stem cells

Recent efforts to understand breast cancer biology involve three interrelated themes that are founded on a combination of clinical and experimental observations. The central concept is gene addiction. The clinical dilemma is the escape from gene addiction, which is mediated, in part, by phenotypic plasticity as exemplified by epithelial-to-mesenchymal transition and mesenchymal-to-epithelial transition. Finally, cancer stem cells are now recognized as the basis for minimal residual disease and malignant progression over time. These themes cooperate in breast cancer, as induction of epithelial-to-mesenchymal transition enhances self-renewal and expression of cancer stem cells, which are believed to facilitate tumor resistance.

Internet and Print Resources to Facilitate Pathology Analysis When Phenotyping Genetically Engineered Rodents

Genetically engineered mice and rats are increasingly used as models for exploring disease progression and mechanisms. The full spectrum of anatomic, biochemical, and functional changes that develop in novel, genetically engineered mouse and rat lines must be cataloged before predictions regarding the significance of the mutation may be extrapolated to diseases in other vertebrate species, including humans. A growing list of reference materials, including books, journal articles, and websites, has been produced in the last 2 decades to assist researchers in phenotyping newly engineered rodent lines. This compilation provides an extensive register of materials related to the pathology component of rodent phenotypic analysis. In this article, the authors annotate the resources they use most often, to allow for quick determination of their relevance to research projects.

An anti-Axl monoclonal antibody attenuates xenograft tumor growth and enhances the effect of multiple anticancer therapies

Axl is expressed in various types of cancer and is involved in multiple processes of tumorigenesis, including promoting tumor cell growth, migration, invasion, metastasis as well as angiogenesis. To evaluate further the mechanisms involved in the expression/activation of Axl in various aspects of tumorigenesis, especially its roles in modulating tumor stromal functions, we have developed a phage-derived mAb (YW327.6S2) that recognizes both human and murine Axl. YW327.6S2 binds to both human and murine Axl with high affinity. It blocks the ligand Gas6 binding to the receptor, downregulates receptor expression, inhibits receptor activation and downstream signaling. In A549 non-small-cell lung cancer (NSCLC) and MDA-MB-231 breast cancer models, YW327.6S2 attenuates xenograft tumor growth and potentiates the effect of anti-VEGF treatment. In NSCLC models, YW327.6S2 also enhances the effect of erlotinib and chemotherapy in reducing tumor growth. Furthermore, YW327.6S2 reduces the metastasis of MDA-MB-231 breast cancer cells to distant organs. YW327.6S2 induces tumor cell apoptosis in NSCLC, reduces tumor-associated vascular density and inhibits the secretion of inflammatory cytokines and chemokines from tumor-associated macrophages in the breast cancer model. In conclusion, anti-Axl mAb can enhance the therapeutic efficacy of anti-VEGF, EGFR small-molecule inhibitors as well as chemotherapy. Axl mAb affects not only tumor cells but also tumor stroma through its modulation of tumor-associated vasculature and immune cell functions.

Atypical parasitic migration and necrotizing sacral myelitis due to Serratospiculoides amaculata in a prairie falcon (Falco mexicanus)

An adult, wild-caught, female prairie falcon (Falco mexicanus) was presented with the chief complaint of anorexia. Radiographic findings included increased densities within the air sacs, and coelomic endoscopy revealed numerous slender worms within the air sacs and on the serosal surfaces of the ovary, oviduct, liver, proventriculus, and ventriculus. The bird seemed to improve for a short period of time with antiparasitic therapy (ivermectin and fenbendazole) and supportive care. Twenty-one days after initial presentation, the bird became recumbent with increasing pelvic limb neurologic deficits and was euthanized. On histopathologic examination, mature nematodes and larvated eggs identified as Serratospiculoides amaculata were found within the subdural space of the distal thoracolumbar and synsacral spinal cord and within the coelomic cavity. This case suggests that S. amaculata can cause clinically significant lesions in its falconiform host with potentially fatal results.