Compartmentalized role of xCT in supporting pancreatic tumor growth, inflammation and mood disturbance in mice

xCT (Slc7a11), the specific subunit of the cystine/glutamate antiporter system xc-, is present in the brain and on immune cells, where it is known to modulate behavior and inflammatory responses. In a variety of cancers -including pancreatic ductal adenocarcinoma (PDAC)-, xCT is upregulated by tumor cells to support their growth and spread. Therefore, we studied the impact of xCT deletion in pancreatic tumor cells (Panc02) and/or the host (xCT-/- mice) on tumor burden, inflammation, cachexia and mood disturbances. Deletion of xCT in the tumor strongly reduced tumor growth. Targeting xCT in the host and not the tumor resulted only in a partial reduction of tumor burden, while it did attenuate tumor-related systemic inflammation and prevented an increase in immunosuppressive regulatory T cells. The latter effect could be replicated by specific xCT deletion in immune cells. xCT deletion in the host or the tumor differentially modulated neuroinflammation. When mice were grafted with xCT-deleted tumor cells, hypothalamic inflammation was reduced and, accordingly, food intake improved. Tumor bearing xCT-/- mice showed a trend of reduced hippocampal neuroinflammation with less anxiety- and depressive-like behavior. Taken together, targeting xCT may have beneficial effects on pancreatic cancer-related comorbidities, beyond reducing tumor burden. The search for novel and specific xCT inhibitors is warranted as they may represent a holistic therapy in pancreatic cancer.

LRP8-mediated selenocysteine uptake is a targetable vulnerability in MYCN-amplified neuroblastoma

Ferroptosis has emerged as an attractive strategy in cancer therapy. Understanding the operational networks regulating ferroptosis may unravel vulnerabilities that could be harnessed for therapeutic benefit. Using CRISPR-activation screens in ferroptosis hypersensitive cells, we identify the selenoprotein P (SELENOP) receptor, LRP8, as a key determinant protecting MYCN-amplified neuroblastoma cells from ferroptosis. Genetic deletion of LRP8 leads to ferroptosis as a result of an insufficient supply of selenocysteine, which is required for the translation of the antiferroptotic selenoprotein GPX4. This dependency is caused by low expression of alternative selenium uptake pathways such as system Xc- . The identification of LRP8 as a specific vulnerability of MYCN-amplified neuroblastoma cells was confirmed in constitutive and inducible LRP8 knockout orthotopic xenografts. These findings disclose a yet-unaccounted mechanism of selective ferroptosis induction that might be explored as a therapeutic strategy for high-risk neuroblastoma and potentially other MYCN-amplified entities.

Resistance to mesenchymal reprogramming sustains clonal propagation in metastatic breast cancer

The acquisition of mesenchymal traits is considered a hallmark of breast cancer progression. However, the functional relevance of epithelial-to-mesenchymal transition (EMT) remains controversial and context dependent. Here, we isolate epithelial and mesenchymal populations from human breast cancer metastatic biopsies and assess their functional potential in vivo. Strikingly, progressively decreasing epithelial cell adhesion molecule (EPCAM) levels correlate with declining disease propagation. Mechanistically, we find that persistent EPCAM expression marks epithelial clones that resist EMT induction and propagate competitively. In contrast, loss of EPCAM defines clones arrested in a mesenchymal state, with concomitant suppression of tumorigenicity and metastatic potential. This dichotomy results from distinct clonal trajectories impacting global epigenetic programs that are determined by the interplay between human ZEB1 and its target GRHL2. Collectively, our results indicate that susceptibility to irreversible EMT restrains clonal propagation, whereas resistance to mesenchymal reprogramming sustains disease spread in multiple models of human metastatic breast cancer, including patient-derived cells in vivo.

A novel empeROR of pancreatic malignancy

How pancreatic cancer cells acquire tumor initiating capacities remains poorly understood. A recent study by Yamazaki et al (2023) uncovers a crucial, targetable role of tyrosine kinase-like orphan receptor (ROR1) in PDAC tumor formation and progression.

HAPLN1 potentiates peritoneal metastasis in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) frequently metastasizes into the peritoneum, which contributes to poor prognosis. Metastatic spreading is promoted by cancer cell plasticity, yet its regulation by the microenvironment is incompletely understood. Here, we show that the presence of hyaluronan and proteoglycan link protein-1 (HAPLN1) in the extracellular matrix enhances tumor cell plasticity and PDAC metastasis. Bioinformatic analysis showed that HAPLN1 expression is enriched in the basal PDAC subtype and associated with worse overall patient survival. In a mouse model for peritoneal carcinomatosis, HAPLN1-induced immunomodulation favors a more permissive microenvironment, which accelerates the peritoneal spread of tumor cells. Mechanistically, HAPLN1, via upregulation of tumor necrosis factor receptor 2 (TNFR2), promotes TNF-mediated upregulation of Hyaluronan (HA) production, facilitating EMT, stemness, invasion and immunomodulation. Extracellular HAPLN1 modifies cancer cells and fibroblasts, rendering them more immunomodulatory. As such, we identify HAPLN1 as a prognostic marker and as a driver for peritoneal metastasis in PDAC.

Molecular heterogeneity and commonalities in pancreatic cancer precursors with gastric and intestinal phenotype

OBJECTIVE

Due to the limited number of modifiable risk factors, secondary prevention strategies based on early diagnosis represent the preferred route to improve the prognosis of pancreatic ductal adenocarcinoma (PDAC). Here, we provide a comparative morphogenetic analysis of PDAC precursors aiming at dissecting the process of carcinogenesis and tackling the heterogeneity of preinvasive lesions.

DESIGN

Targeted and whole-genome low-coverage sequencing, genome-wide methylation and transcriptome analyses were applied on a final collective of 122 morphologically well-characterised low-grade and high-grade PDAC precursors, including intestinal and gastric intraductal papillary mucinous neoplasms (IPMN) and pancreatic intraepithelial neoplasias (PanIN).

RESULTS

Epigenetic regulation of mucin genes determines the phenotype of PDAC precursors. PanIN and gastric IPMN display a ductal molecular profile and numerous similarly regulated pathways, including the Notch pathway, but can be distinguished by recurrent deletions and differential methylation and, in part, by the expression of mucin-like 3. Intestinal IPMN are clearly distinct lesions at the molecular level with a more instable genotype and are possibly related to a different ductal cell compartment.

CONCLUSIONS

PDAC precursors with gastric and intestinal phenotype are heterogeneous in terms of morphology, genetic and epigenetic profile. This heterogeneity is related to a different cell identity and, possibly, to a different aetiology.

Practical Considerations for Complex Tissue Dissociation for Single-Cell Transcriptomics

Single-cell and single-nucleus RNA sequencing have revolutionized biomedical research, allowing analysis of complex tissues, identification of novel cell types, and mapping of development as well as disease states. Successful application of this technology critically relies on the dissociation of solid organs and tissues into high-quality single-cell (or nuclei) suspensions.In this chapter, we examine several key aspects of the tissue handling workflow that need to be considered when establishing an efficient tissue processing protocol for single-cell RNA sequencing (scRNA-seq). These include tissue collection, transport, and storage, as well as the choice of the dissociation conditions. We emphasize the importance of the tissue quality check and discuss the advantages (and potential limitations) of tissue cryopreservation. We provide practical tips and considerations on each of the steps of the processing workflow, and comment on how to maximize cell viability and integrity, which are critical for obtaining high-quality single-cell transcriptomic data.

Mechanisms of PDAC subtype heterogeneity and therapy response

Pancreatic ductal adenocarcinoma (PDAC) is clinically challenging due to late diagnosis and resistance to therapy. Two major PDAC subtypes have been defined based on malignant epithelial cell gene expression profiles; the basal-like/squamous subtype is associated with a worse prognosis and therapeutic resistance as opposed to the classical subtype. Subtype specification is not binary, consistent with plasticity of malignant cell phenotype. PDAC heterogeneity and plasticity reflect partly malignant cell-intrinsic transcriptional and epigenetic regulation. However, the stromal and immune compartments of the tumor microenvironment (TME) also determine disease progression and therapy response. It is evident that integration of intrinsic and extrinsic factors can dictate subtype heterogeneity, and thus, delineating the pathways involved can help to reprogram PDAC towards a classical/druggable subtype.

Abstract C034: Bioinformatical identification of cancer-associated-fibroblasts with tumor cells pro-migratory crosstalks depending on activin

Pancreatic ductal adenocarcinoma (PDAC) aggressiveness results from its high metastatic and chemoresistance potential. Pancreatic cancer cells are immersed in an exuberant tumor microenvironment (or stroma), which represents up to 80% of PDAC tumor volume, and is hijacked by cancer cells for their own survival and metastasis. Additionally, PDAC tumors are heterogeneous, e.g. transcriptomic (RNAseq) analyses of human PDAC tumors have allowed patients to be stratified into two tumor subgroups (basal and classical) with different prognoses. Therefore, we aimed to understand which tumor-stroma crosstalks are critical for PDAC aggressiveness in the context of its heterogeneity, and how they can be pharmacologically targeted, to then propose more effective personalized therapeutic strategies. By performing bioinformatical analysis on RNAseq data from PDX (Patient Derived Xenograft), a hybrid tumor model from which human-derived tumor cell sequences are distinguishable from murine-derived stromal cell sequences, we searched for different stromal behaviors linked to the tumor aggressiveness, to be then validated in published PDAC patient databases. According to NMF (Non-negative matrix factorization) and GSEA (Gene Set Enrichment Analyses), we identified two components, which classify the samples according to a stromal gradient. Interestingly, these components are characterized by distinct functional signatures of aggressiveness and they are highly prognostic (correlated with survival). In addition, these components stratify patients independently on the described molecular tumor (basal or classical) classification. Importantly, we validated those results on other PDAC published databases. Moreover, ligand-receptor bioinformatics analyses identified novel players of the TGFβ superfamily in the most aggressive stromal component. Indeed, we have highlighted the involvement of the ligand activin a member of this large superfamily. Using in situ hybridization coupled with immunofluorescence, we were able to demonstrate that activin is only expressed by stromal cells, and more specifically by cancer associated fibroblasts (CAF), with however a strong heterogeneity (inter and intra-tumor). In vitro, activin strongly increases the migratory capacity of fibroblasts but also of specific cancer cells, this effect being effectively blocked pharmacologically with an activin receptor-targeting drug that is now tested in a pre-clinical PDAC murine model. Therapeutic targeting of the stroma must take into account its functional heterogeneity. We have identified in specific aggressive PDAC tumors novel stromal players involved in the tumor-stroma symbiosis, and which presumably play a critical role in CAFs and cancer cells migration and invasion. Our work should enable to delineate which stroma-targeting drug to co-deliver, in addition to chemotherapies, in stratified patients, to improve PDAC prognosis.

Citation Format: Alexia Brunel, Jérôme Raffenne, Remy Nicolle, Ilse Rooman, Elisa Espinet, Marjorie Fanjul, Aurélie Perraud, Muriel Mathonnet, Sophie Vasseur, Nelson Dusetti, Yvan Martineau, Christine Jean, Corinne Bousquet. Bioinformatical identification of cancer-associated-fibroblasts with tumor cells pro-migratory crosstalks depending on activin [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr C034.

Axon guidance receptor ROBO3 modulates subtype identity and prognosis via AXL-associated inflammatory network in pancreatic cancer

Metastatic pancreatic cancer (PDAC) has a poor clinical outcome with a 5-year survival rate below 3%. Recent transcriptome profiling of PDAC biopsies has identified 2 clinically distinct subtypes - the "basal-like" (BL) subtype with poor prognosis and therapy resistance compared with the less aggressive and drug-susceptible "classical" (CLA) subtype. However, the mechanistic events and environmental factors that promote the BL subtype identity are not very clear. Using preclinical models, patient-derived xenografts, and FACS-sorted PDAC patient biopsies, we report here that the axon guidance receptor, roundabout guidance receptor 3 (ROBO3), promotes the BL metastatic program via a potentially unique AXL/IL-6/phosphorylated STAT3 (p-STAT3) regulatory axis. RNA-Seq identified a ROBO3-mediated BL-specific gene program, while tyrosine kinase profiling revealed AXL as the key mediator of the p-STAT3 activation. CRISPR/dCas9-based ROBO3 silencing disrupted the AXL/p-STAT3 signaling axis, thereby halting metastasis and enhancing therapy sensitivity. Transcriptome analysis of resected patient tumors revealed that AXLhi neoplastic cells associated with the inflammatory stromal program. Combining AXL inhibitor and chemotherapy substantially restored a CLA phenotypic state and reduced disease aggressiveness. Thus, we conclude that a ROBO3-driven hierarchical network determines the inflammatory and prometastatic programs in a specific PDAC subtype.

Abstract 960: HAPLN1 increases peritoneal carcinomatosis by inducing tumor cell hyperplasticity

Pancreatic Ductal Adenocarcinoma (PDAC) frequently metastasizes into the peritoneum forming peritoneal carcinomatosis, which are so far not treatable effectively. Metastasis-initiating cells need to acquire beneficial traits including cell plasticity, immune evasion, dormancy state control and organ colonization. These characteristics can be summarized in broad terms into two main processes, epithelial-to-mesenchymal transition (EMT) and stemness. Hyaluronic acid (HA), an extracellular matrix component, is a crucial factor in regulating these processes in PDAC, but it is so far not successfully targetable. Analyzing publicly available databases by gene set enrichment analysis (GSEA), a signature related to HA binding was enriched in tumor samples compared to normal tissue. Hyaluronan And Proteoglycan Link Protein 1 (HAPLN1) was the top contributor to the enrichment score, being the 8th most enriched gene overall. We found that higher HAPLN1 expression correlated with shorter overall survival and that HAPLN1high patients had both, basal subtype and EMT signatures enriched. Moreover, these patients had a signature for peritoneal metastasis significantly enriched, suggesting a higher risk for peritoneal carcinomatosis. To study the role of HAPLN1 on PDAC in vitro, we stably overexpressed HAPLN1 in the murine PDAC cell line KPC. KPC-HAPLN1 cells expressed more EMT markers, more stem-related genes and changed the proteoglycan production from Aggrecan to Versican, which is known to be pro-metastatic. We found that spheroid formation, a feature of stemness, was improved in KPC-HAPLN1 vs KPC. Additionally, embedding these spheroids into matrigel led to an increased invasion of KPC-HAPLN1 cells. KPC-HAPLN1 cells improved KPC cell invasion capacities when co-cultured, indicating a paracrine effect. In vivo, intraperitoneal injection of luciferase expressing KPC cells resulted in higher luciferase activity when tumor cells expressed HAPLN1. Analyzing the peritoneal lavage (PL) from these mice, we obtained significantly more tumor cells in KPC-HAPLN1 injected mice. RNAseq data of tumor cells isolated from tumor nodules and PL showed that KPC-HAPLN1 cells acquired an increased metastatic potential and a strong immunomodulatory phenotype. Thus, we evaluated the immune cell composition of the PL by flow cytometry. Neutrophil and monocyte percentages were drastically reduced in KPC-HAPLN1 bearing mice. On the contrary, these mice had a significant increase in macrophages, which showed a reduction in pro-inflammatory gene expression. We conclude that HAPLN1 expression in tumor cells promotes a hyperplastic phenotype that facilitates invasion and colonization of the peritoneum, among others by creation of a pro-tumoral immune microenvironment.

Citation Format: Lena Wiedmann, Francesca De Angelis Rigotti, Nuria Vaquero-Siguero, Elisa Donato, Elisa Espinet, Andreas Trumpp, Andreas Fischer, Juan Rodriguez-Vita. HAPLN1 increases peritoneal carcinomatosis by inducing tumor cell hyperplasticity [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 960.

Pancreatic Organoids for Regenerative Medicine and Cancer Research

In recent years, the development of ex vivo organoid cultures has gained substantial attention as a model to study regenerative medicine and diseases in several tissues. Diabetes and pancreatic ductal adenocarcinoma (PDAC) are the two major devastating diseases affecting the pancreas. Suitable models for regenerative medicine in diabetes and to accurately study PDAC biology and treatment response are essential in the pancreatic field. Pancreatic organoids can be generated from healthy pancreas or pancreatic tumors and constitute an important translational bridge between in vitro and in vivo models. Here, we review the rapidly emerging field of pancreatic organoids and summarize the current applications of the technology to tissue regeneration, disease modelling, and drug screening.

On the Origin of Pancreatic Cancer: Molecular Tumor Subtypes in Perspective of Exocrine Cell Plasticity

Pancreatic ductal adenocarcinoma (PDAC) is a devastating type of cancer. While many studies have shed light into the pathobiology of PDAC, the nature of PDAC's cell of origin remains under debate. Studies in adult pancreatic tissue have unveiled a remarkable exocrine cell plasticity including transitional states, mostly exemplified by acinar to ductal cell metaplasia, but also with recent evidence hinting at duct to basal cell transitions. Single-cell RNA sequencing has further revealed intrapopulation heterogeneity among acinar and duct cells. Transcriptomic and epigenomic relationships between these exocrine cell differentiation states and PDAC molecular subtypes have started to emerge, suggesting different ontogenies for different tumor subtypes. This review sheds light on these diverse aspects with particular focus on studies with human cells. Understanding the "masked ball" of exocrine cells at origin of PDAC and leaving behind the binary acinar vs duct cell classification may significantly advance our insights in PDAC biology.

TNF-α-producing macrophages determine subtype identity and prognosis via AP1 enhancer reprogramming in pancreatic cancer

Large-scale genomic profiling of pancreatic cancer (PDAC) has revealed two distinct subtypes: 'classical' and 'basal-like'. Their variable coexistence within the stromal immune microenvironment is linked to differential prognosis; however, the extent to which these neoplastic subtypes shape the stromal immune landscape and impact clinical outcome remains unclear. By combining preclinical models, patient-derived xenografts, as well as FACS-sorted PDAC patient biopsies, we show that the basal-like neoplastic state is sustained via BRD4-mediated cJUN/AP1 expression, which induces CCL2 to recruit tumor necrosis factor (TNF)-α-secreting macrophages. TNF-α+ macrophages force classical neoplastic cells into an aggressive phenotypic state via lineage reprogramming. Integration of ATAC-, ChIP- and RNA-seq data revealed distinct JUNB/AP1 (classical) and cJUN/AP1 (basal-like)-driven regulation of PDAC subtype identity. Pharmacological inhibition of BRD4 led to suppression of the BRD4-cJUN-CCL2-TNF-α axis, restoration of classical subtype identity and a favorable prognosis. Hence, patient-tailored therapy for a cJUNhigh/TNF-αhigh subtype is paramount in overcoming highly inflamed and aggressive PDAC states.

Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis

Metastasis is the primary cause of cancer-related mortality. Tumor cell interactions with cells of the vessel wall are decisive and potentially rate-limiting for metastasis. The molecular nature of this cross-talk is, beyond candidate gene approaches, hitherto poorly understood. Using endothelial cell (EC) bulk and single-cell transcriptomics in combination with serum proteomics, we traced the evolution of the metastatic vascular niche in surgical models of lung metastasis. Temporal multiomics revealed that primary tumors systemically reprogram the body’s vascular endothelium to perturb homeostasis and to precondition the vascular niche for metastatic growth. The vasculature with its enormous surface thereby serves as amplifier of tumor-induced instructive signals. Comparative analysis of lung EC gene expression and secretome identified the transforming growth factor–β (TGFβ) pathway specifier LRG1, leucine-rich alpha-2-glycoprotein 1, as an early instructor of metastasis. In the presence of a primary tumor, ECs systemically up-regulated LRG1 in a signal transducer and activator of transcription 3 (STAT3)–dependent manner. A meta-analysis of retrospective clinical studies revealed a corresponding up-regulation of LRG1 concentrations in the serum of patients with cancer. Functionally, systemic up-regulation of LRG1 promoted metastasis in mice by increasing the number of prometastatic neural/glial antigen 2 (NG2)+ perivascular cells. In turn, genetic deletion of Lrg1 hampered growth of lung metastasis. Postsurgical adjuvant administration of an LRG1-neutralizing antibody delayed metastatic growth and increased overall survival. This study has established a systems map of early primary tumor-induced vascular changes and identified LRG1 as a therapeutic target for metastasis.

Human Retrotransposons and the Global Shutdown of Homeostatic Innate Immunity by Oncolytic Parvovirus H-1PV in Pancreatic Cancer

Although the oncolytic parvovirus H-1PV has entered clinical trials, predicting therapeutic success remains challenging. We investigated whether the antiviral state in tumor cells determines the parvoviral oncolytic efficacy. The interferon/interferon-stimulated genes (IFN/ISG)-circuit and its major configurator, human endogenous retroviruses (HERVs), were evaluated using qRT-PCR, ELISA, Western blot, and RNA-Seq techniques. In pancreatic cancer cell lines, H-1PV caused a late global shutdown of innate immunity, whereby the concomitant inhibition of HERVs and IFN/ISGs was co-regulatory rather than causative. The growth-inhibitory IC50 doses correlated with the power of suppression but not with absolute ISG levels. Moreover, H-1PV was not sensitive to exogenous IFN despite upregulated antiviral ISGs. Such resistance questioned the biological necessity of the oncotropic ISG-shutdown, which instead might represent a surrogate marker for personalized oncolytic efficacy. The disabled antiviral homeostasis may modify the activity of other viruses, as demonstrated by the reemergence of endogenous AluY-retrotransposons. This way of suppression may compromise the interferogenicity of drugs having gemcitabine-like mechanisms of action. This shortcoming in immunogenic cell death induction is however amendable by immune cells which release IFN in response to H-1PV.

Versatile workflow for cell type-resolved transcriptional and epigenetic profiles from cryopreserved human lung

Complexity of lung microenvironment and changes in cellular composition during disease make it exceptionally hard to understand molecular mechanisms driving development of chronic lung diseases. Although recent advances in cell type-resolved approaches hold great promise for studying complex diseases, their implementation relies on local access to fresh tissue, as traditional tissue storage methods do not allow viable cell isolation. To overcome these hurdles, we developed a versatile workflow that allows storage of lung tissue with high viability, permits thorough sample quality check before cell isolation, and befits sequencing-based profiling. We demonstrate that cryopreservation enables isolation of multiple cell types from both healthy and diseased lungs. Basal cells from cryopreserved airways retain their differentiation ability, indicating that cellular identity is not altered by cryopreservation. Importantly, using RNA sequencing and EPIC Array, we show that gene expression and DNA methylation signatures are preserved upon cryopreservation, emphasizing the suitability of our workflow for omics profiling of lung cells. Moreover, we obtained high-quality single-cell RNA-sequencing data of cells from cryopreserved human lungs, demonstrating that cryopreservation empowers single-cell approaches. Overall, thanks to its simplicity, our workflow is well suited for prospective tissue collection by academic collaborators and biobanks, opening worldwide access to viable human tissue.

Stromal NRG1 in luminal breast cancer defines pro-fibrotic and migratory cancer-associated fibroblasts

HER3 is highly expressed in luminal breast cancer subtypes. Its activation by NRG1 promotes activation of AKT and ERK1/2, contributing to tumour progression and therapy resistance. HER3-targeting agents that block this activation, are currently under phase 1/2 clinical studies, and although they have shown favorable tolerability, their activity as a single agent has proven to be limited. Here we show that phosphorylation and activation of HER3 in luminal breast cancer cells occurs in a paracrine manner and is mediated by NRG1 expressed by cancer-associated fibroblasts (CAFs). Moreover, we uncover a HER3-independent NRG1 signaling in CAFs that results in the induction of a strong migratory and pro-fibrotic phenotype, describing a subtype of CAFs with elevated expression of NRG1 and an associated transcriptomic profile that determines their functional properties. Finally, we identified Hyaluronan Synthase 2 (HAS2), a targetable molecule strongly correlated with NRG1, as an attractive player supporting NRG1 signaling in CAFs.

Abstract IA05: Viral Mimicry in Pancreatic Cancer

With an overall survival rate of about 8% after five years, ductal adenocarcinoma of the pancreas (PDAC) is one of the cancers with the worst prognosis (Cancer Research UK and American Cancer Society). A hallmark of PDAC is the immense contribution of desmoplastic stroma to the total tumour mass. Typically, epithelial PDAC cells represent only a minority of cells within the tumour (as low as 10%). The excessive stromal presence represents a major technical challenge when aiming to interrogate the specific molecular signals contributed by the neoplastic epithelial cell compartment from data generated using bulk tumour samples. To address this, we FACS-purified epithelial cells from PDAC and, as controls, healthy human pancreas and performed genome-wide transcriptome and DNA methylome analyses. Clustering based on DNA methylation revealed two distinct groups of PDAC with different methylation levels at genomic regions encoding repeat elements. Methylationlow tumours showed higher expression of endogenous retroviral (ERV) transcripts and a strong engagement of the dsRNA sensing machinery. This results in the cell intrinsic activation of an interferon response signature (IFNsign), leading to the reprogramming of stromal cells towards a pro-tumourigenic microenvironment and poor patient outcome. Methylationlow/IFNsignhigh and Methylationhigh/IFNsignlow PDAC cells harboured distinct lineage traits specific for normal ductal or acinar pancreatic epithelial cells at the methylation and transcriptional level. Moreover, ductal-cell-derived KrasG12D/Trp53-/- mutant mouse PDACs showed higher expression of IFNsign compared to tumors initiated by the same genetic drivers in acinar cells. Collectively, our data point to two distinct origins and etiology of human PDACs, with the aggressive Methylationhigh/IFNsignlow tumour subtype potentially targetable by agents blocking cell intrinsic IFN-signaling.

Citation Format: Elisa Espinet, Andreas Trumpp. Viral Mimicry in Pancreatic Cancer [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr IA05.

Aggressive PDACs Show Hypomethylation of Repetitive Elements and the Execution of an Intrinsic IFN Program Linked to a Ductal Cell of Origin

Pancreatic ductal adenocarcinoma (PDAC) is characterized by extensive desmoplasia, which challenges the molecular analyses of bulk tumor samples. Here we FACS-purified epithelial cells from human PDAC and normal pancreas and derived their genome-wide transcriptome and DNA methylome landscapes. Clustering based on DNA methylation revealed two distinct PDAC groups displaying different methylation patterns at regions encoding repeat elements. Methylation^low tumors are characterized by higher expression of endogenous retroviral transcripts and double-stranded RNA sensors, which lead to a cell-intrinsic activation of an interferon signature (IFNsign). This results in a protumorigenic microenvironment and poor patient outcome. Methylation^low/IFNsign^high and Methylation^high/IFNsign^low PDAC cells preserve lineage traits, respective of normal ductal or acinar pancreatic cells. Moreover, ductal-derived Kras ^G12D/Trp53 ^-/- mouse PDACs show higher expression of IFNsign compared with acinar-derived counterparts. Collectively, our data point to two different origins and etiologies of human PDACs, with the aggressive Methylation^low/IFNsign^high subtype potentially targetable by agents blocking intrinsic IFN signaling. SIGNIFICANCE: The mutational landscapes of PDAC alone cannot explain the observed interpatient heterogeneity. We identified two PDAC subtypes characterized by differential DNA methylation, preserving traits from normal ductal/acinar cells associated with IFN signaling. Our work suggests that epigenetic traits and the cell of origin contribute to PDAC heterogeneity.This article is highlighted in the In This Issue feature, p. 521.

Novel Non-integrating DNA Nano-S/MAR Vectors Restore Gene Function in Isogenic Patient-Derived Pancreatic Tumor Models

We describe herein non-integrating minimally sized nano-S/MAR DNA vectors, which can be used to genetically modify dividing cells in place of integrating vectors. They represent a unique genetic tool, which avoids vector-mediated damage. Previous work has shown that DNA vectors comprising a mammalian S/MAR element can provide persistent mitotic stability over hundreds of cell divisions, resisting epigenetic silencing and thereby allowing sustained transgene expression. The composition of the original S/MAR vectors does present some inherent limitations that can provoke cellular toxicity. Herein, we present a new system, the nano-S/MAR, which drives higher transgene expression and has improved efficiency of establishment, due to the minimal impact on cellular processes and perturbation of the endogenous transcriptome. We show that these features enable the hitherto challenging genetic modification of patient-derived cells to stably restore the tumor suppressor gene SMAD4 to a patient-derived SMAD4 knockout pancreatic cancer line. Nano-S/MAR modification does not alter the molecular or phenotypic integrity of the patient-derived cells in cell culture and xenograft mouse models. In conclusion, we show that these DNA vectors can be used to persistently modify a range of cells, providing sustained transgene expression while avoiding the risks of insertional mutagenesis and other vector-mediated toxicity.

Endothelial Notch1 Activity Facilitates Metastasis

Endothelial cells (ECs) provide angiocrine factors orchestrating tumor progression. Here, we show that activated Notch1 receptors (N1ICD) are frequently observed in ECs of human carcinomas and melanoma, and in ECs of the pre-metastatic niche in mice. EC N1ICD expression in melanoma correlated with shorter progression-free survival. Sustained N1ICD activity induced EC senescence, expression of chemokines and the adhesion molecule VCAM1. This promoted neutrophil infiltration, tumor cell (TC) adhesion to the endothelium, intravasation, lung colonization, and postsurgical metastasis. Thus, sustained vascular Notch signaling facilitates metastasis by generating a senescent, pro-inflammatory endothelium. Consequently, treatment with Notch1 or VCAM1-blocking antibodies prevented Notch-driven metastasis, and genetic ablation of EC Notch signaling inhibited peritoneal neutrophil infiltration in an ovarian carcinoma mouse model.

Abstract B77: CYP3A5 mediates basal and acquired therapy resistance in different subtypes of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a very aggressive disease with poor prognosis. Treatment with gemcitabine, the FOLFIRINOX scheme or nab-paclitaxel offer only a modest increase in overall survival. For a number of other carcinomas, tumor subtypes have been uncovered that allow the use of targeted therapies. Although subtypes of PDAC were described, this malignancy is clinically still treated as a single disease. We established patient-derived models representing the full spectrum of previously identified quasi-mesenchymal (QM-PDA), classical and exocrine-like PDAC subtypes, and identified two markers—HNF1A and KRT81—that enable stratification of tumors into different subtypes by immunohistochemistry. Patients bearing tumors of these subtypes show significant differences in overall survival and their tumors differ in drug sensitivity, with the exocrine-like subtype being resistant to tyrosine kinase inhibitors and paclitaxel. The xenobiotic enzyme, cytochrome P450 3A5 (CYP3A5), metabolizes these compounds in tumors of the exocrine-like subtype, and pharmacological or short hairpin RNA (shRNA)-mediated CYP3A5 inhibition sensitizes tumor cells to these drugs. Additionally, retrospective analysis of a large patient cohort confirmed that CYP3A5 is predominantly found in those patient tumors classified as exocrine-like. Whereas the hepatocyte nuclear factor 4, alpha (HNF4A) controls basal expression of CYP3A5, drug-induced CYP3A5 upregulation is mediated by the nuclear receptor NR1I2. Interfering with these regulatory mechanisms may provide an alternative approach to suppress the CYP3A5 pathway. CYP3A5 also contributes to acquired drug resistance in QM-PDA and classical PDAC, and is highly expressed in several additional malignancies. These findings designate CYP3A5 as predictor of therapy response and as a tumor cell-autonomous detoxification mechanism that must be overcome to prevent drug resistance.

Citation Format: Elisa M. Noll, Christian Eisen, Albrecht Stenzinger, Elisa Espinet, Alexander Muckenhuber, Corinna Klein, Vanessa Vogel, Bernd Klaus, Wiebke Nadler, Christoph Rösli, Christian Lutz, Michael Kulke, Jan Engelhardt, Franziska Zickgraf, Octavio Espinosa, Matthias Schlesner, Xiaoqi Jiang, Annette Kopp-Schneider, Peter Neuhaus, Marcus Bahra, Bruno V. Sinn, Roland Eils, Nathalia A. Giese, Thilo Hackert, Oliver Strobel, Jens Werner, Markus W. Büchler, Wilko Weichert, Andreas Trumpp, Martin R. Sprick.{Authors}. CYP3A5 mediates basal and acquired therapy resistance in different subtypes of pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B77.

Abstract LB-120: CYP3A5 mediates basal and acquired therapy resistance in different subtypes of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with poor prognosis. Treatment with gemcitabine, the FOLFIRINOX scheme or nab-paclitaxel offer only a modest increase in overall survival. For a number of other carcinomas, tumor subtypes have been uncovered that allow the use of targeted therapies. Although subtypes of PDAC were described, this malignancy is clinically still treated as a single disease. We established patient-derived models representing the full spectrum of previously identified quasi-mesenchymal (QM-PDA), classical and exocrine-like PDAC subtypes, and identified two markers—HNF1A and KRT81—that enable stratification of tumors into different subtypes by immunohistochemistry. Patients bearing tumors of these subtypes show significant differences in overall survival and their tumors differ in drug sensitivity, with the exocrine-like subtype being resistant to tyrosine kinase inhibitors and paclitaxel. The xenobiotic enzyme, cytochrome P450 3A5 (CYP3A5), metabolizes these compounds in tumor cells of the exocrine-like subtype, and pharmacological or short hairpin RNA (shRNA)-mediated CYP3A5 inhibition sensitizes tumor cells to these drugs. Additionally, retrospective analysis of a large patient cohort confirmed that CYP3A5 is predominantly found in those patient tumors classified as exocrine-like (Noll, Eisen et al., Nature Medicine (2016) accepted). Whereas the hepatocyte nuclear factor 4, alpha (HNF4A) controls basal expression of CYP3A5, drug-induced CYP3A5 upregulation is mediated by the nuclear receptor NR1I2. Interfering with these regulatory mechanisms may provide an alternative approach to suppress the CYP3A5 mediated resistance pathway. CYP3A5 also contributes to acquired drug resistance in QM-PDA and classical PDAC in vitro and in vivo. Finally, CYP3A5 is highly expressed in several additional malignancies including hepatocellular and cervical carcinomas raising the possibility that the CYP3A5 resistance mechanism is operational in a variety of human cancers. These findings designate CYP3A5 as predictor of therapy response and as a tumor cell-autonomous detoxification mechanism that must be overcome to prevent drug resistance.

Citation Format: Elisa M. Noll, Christian Eisen, Albrecht Stenzinger, Elisa Espinet, Alexander Muckenhuber, Corinna Klein, Vanessa Vogel, Bernd Klaus, Wiebke Nadler, Christoph Rösli, Christian Lutz, Michael Kulke, Jan Engelhardt, Franziska Zickgraf, Octavio Espinosa, Matthias Schlesner, Xiaoqi Jiang, Annette Kopp-Schneider, Peter Neuhaus, Marcus Bahra, Bruno Sinn, Roland Eils, Nathalia Giese, Thilo Hackert, Oliver Strobel, Jens Werner, Markus W. Büchler, Wilko Weichert, Andreas Trumpp, Martin R. Sprick. CYP3A5 mediates basal and acquired therapy resistance in different subtypes of pancreatic ductal adenocarcinoma. [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 LB-120.

Abstract IA22: CYP3A5 mediates resistance to small molecule inhibitors in a subtype of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is clinically still treated as a single disease. We have generated patient-derived models representing the recently identified quasi-mesenchymal, classical and exocrine-like PDAC subtypes, and report a two-marker set facilitating patient stratification by immunohistochemistry. The subtypes show significant differences in overall survival and drug sensitivity, with the exocrine-like subtype being resistant to the tyrosine kinase inhibitors erlotinib, dasatinib, as well as the chemotherapeutic paclitaxel. Highly expressed cytochrome P450 3A5 (CYP3A5) actively metabolizes these compounds in the exocrine-like subtype, and pharmacological or shRNA-mediated CYP3A5 inhibition sensitizes tumor cells in vivo. Additionally, we investigated the transcriptional network underlying the subtype-specific CYP3A5 expression. Hence, these data show that exocrine-like PDAC adopts a highly effective detoxification mechanism akin to that of hepatocytes. High expression of CYP3A5 in other tumor entities suggests this pathway as an important target to overcome drug resistance and to predict response to therapy with small molecule drugs.

Citation Format: Elisa M. Noll, Elisa M. Noll, Christian Eisen, Christian Eisen, Elisa Espinet, Elisa Espinet, Albrecht Stenzinger, Wilko Weichert, Martin R. Sprick, Andreas Trumpp, Andreas Trumpp. CYP3A5 mediates resistance to small molecule inhibitors in a subtype of pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr IA22.

Abstract A69: A novel mechanism mediates drug resistance in the exocrine-like pancreatic ductal adenocarcinoma (PDAC) subtype

PDAC is a highly aggressive disease with dismal prognosis [1, 2]. Despite extensive research and the discovery of several drug candidates, little progress has been reported since the approval of gemcitabine and erlotinib [1]. Moreover, recent trials with targeted therapies have shown only limited or no benefit [1, 2]. For a number of other carcinomas, tumor subclasses have been uncovered that allow the use of targeted therapies. The mutational landscape of PDAC is complex and heterogeneous, raising the question whether subclasses also exist in PDAC [3]. Collisson et al. described three PDAC subtypes that were identified based on their gene-expression profiles: The classical, the quasi-mesenchymal and the exocrine-like subtype [4]. However, not all subtypes could be identified in the previously available model systems. We have established a novel patient-derived model system that allows the analysis of these three human PDAC subtypes in vitro and in vivo. Hence, we provide a systematic workflow to propagate human PDAC in orthotopic xenografts and to derive tumor-initiating primary cell lines of all three PDAC subtypes. HNF-1 and Keratin 81 were identified as markers for subtype stratification by immunohistochemistry. Application of this two-marker set on a 258 large patient cohort confirmed a predominantly non-overlapping staining and revealed a significant difference in overall survival across the three subtypes. Furthermore, a drug screen uncovered subtype-specific drug sensitivities towards a number of drugs, including gemcitabine and dasatinib. Notably, the exocrine-like subtype was resistant towards all compounds tested. Thus, we aimed to identify the underlying cause of the observed drug resistance. Molecular analysis including gene set enrichment analysis (GSEA) allowed us to identify a putative novel mechanism of drug resistance. Analysis by qRT-PCR and Western blot demonstrated the enhanced expression of several genes mediating this mechanism particularly in the exocrine-like subtype in vitro and in vivo. These findings led to the identification of a novel protein target central to this mechanism. Additionally, retrospective immunohistochemical analysis of a large patient cohort confirmed that this target is predominantly found in those patient tumors classified as exocrine-like. Hence, we hypothesized that the observed strong activation of this mechanism in the exocrine-like PDAC subtype could be responsible for the drug resistance observed in this subclass. In line with this, functional inhibition of this mechanism resulted in increased drug sensitivity in the exocrine-like subtype. Hence, our findings may ultimately advance personalized treatment by applying novel marker-based patient selection strategies in combination with tailored drug use, a strategy which will be presented in more detail at the conference.

[1] Hidalgo, M. Pancreatic cancer. The New England journal of medicine. 362, 1605-1617, doi:10.1056/NEJMra0901557 (2010).

[2] Vincent, A., Herman, J., Schulick, R., Hruban, R. H. & Goggins, M. Pancreatic cancer. Lancet. 378, 607-620, doi:10.1016/S0140-6736(10)62307-0 (2011).

[3] Jones, S. et al. Core signalling pathways in human pancreatic cancers revealed by global genomic analyses. Science. 321, 1801-1806, doi:10.1126/science.1164368 (2008).

[4] Collisson, E. A. et al. Subtypes of pancreatic ductal adenocarcinoma and their differing responses to therapy. Nature medicine. 17, 500-503, doi:10.1038/nm.2344 (2011).

Citation Format: Elisa M. Noll, Christian Eisen, Elisa Espinet, Vanessa Vogel, Corinna Klein, Albrecht Stenzinger, Franziska Zickgraf, Peter Neuhaus, Marcus Bahra, Bruno V. Sinn, Christian Lutz, Michael Kulke, Andreas Pahl, Nathalia A. Giese, Oliver Strobel, Jens Werner, Wilko Weichert, Andreas Trumpp, Martin R. Sprick. A novel mechanism mediates drug resistance in the exocrine-like pancreatic ductal adenocarcinoma (PDAC) subtype. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A69.

Stromal gene expression defines poor-prognosis subtypes in colorectal cancer

Recent molecular classifications of colorectal cancer (CRC) based on global gene expression profiles have defined subtypes displaying resistance to therapy and poor prognosis. Upon evaluation of these classification systems, we discovered that their predictive power arises from genes expressed by stromal cells rather than epithelial tumor cells. Bioinformatic and immunohistochemical analyses identify stromal markers that associate robustly with disease relapse across the various classifications. Functional studies indicate that cancer-associated fibroblasts (CAFs) increase the frequency of tumor-initiating cells, an effect that is dramatically enhanced by transforming growth factor (TGF)-β signaling. Likewise, we find that all poor-prognosis CRC subtypes share a gene program induced by TGF-β in tumor stromal cells. Using patient-derived tumor organoids and xenografts, we show that the use of TGF-β signaling inhibitors to block the cross-talk between cancer cells and the microenvironment halts disease progression.

Immunostaining Protocol: P-Stat3 (Xenograft and Mice)

We sought to understand the mechanisms behind the potent effect of stromal TGF-beta program on the capacity of colorectal cancer (CRC) cells to initiate metastasis. We discovered that mice subcutaneous tumors and metastases generated in the context of a TGF-beta activated microenvironment displayed prominent accumulation of p-STAT3 in CRC cells compared with those derived from control cells. STAT3 signaling depended on GP130 as shown by strong reduction of epithelial p STAT3 levels upon GP130 shRNA-mediated knockdown in CRC cells.

Dependency of colorectal cancer on a TGF-β-driven program in stromal cells for metastasis initiation

A large proportion of colorectal cancers (CRCs) display mutational inactivation of the TGF-β pathway, yet, paradoxically, they are characterized by elevated TGF-β production. Here, we unveil a prometastatic program induced by TGF-β in the microenvironment that associates with a high risk of CRC relapse upon treatment. The activity of TGF-β on stromal cells increases the efficiency of organ colonization by CRC cells, whereas mice treated with a pharmacological inhibitor of TGFBR1 are resilient to metastasis formation. Secretion of IL11 by TGF-β-stimulated cancer-associated fibroblasts (CAFs) triggers GP130/STAT3 signaling in tumor cells. This crosstalk confers a survival advantage to metastatic cells. The dependency on the TGF-β stromal program for metastasis initiation could be exploited to improve the diagnosis and treatment of CRC.

[Capsule endoscopy interpretation: the role of physician extenders]

BACKGROUND AND AIMS

capsule endoscopy (CE) allows for a new era in small-bowel examination. Nevertheless, physicians time for CE-interpretation remains longer than desirable. Alternative strategies to physicians have not been widely investigated. The aim of this study was to evaluate the accuracy of physician extenders in CE-interpretation.

MATERIAL AND METHODS

one CE-experienced gastroenterologist and two physician extenders reviewed independently 20 CE-procedures. Each reader was blinded to the findings of their colleagues. A consensus formed by the readers and a second CE-experienced gastroenterologist was used as gold standard. Number, type and location of images selected, character of CE-exams and their relationship with indications were recorded. Gastric emptying time (GEt), small-bowel transit time (SBTt) and time spent by readers were also noted.

RESULTS

sensitivity and specificity for "overall" lesions was 79 and 99% for the gastroenterologist; 86 and 43% for the nurse; and 80 and 57% for the resident. All 34 "major" lesions considered by consensus were found by the readers. Agreement between consensus and readers for images classification and procedures interpretation was good to excellent (? from 0.55 to 1). No significant differences were found in the GEt and SBTt obtained by consensus and readers. The gastroenterologist was faster than physician extenders (mean time spent was 51.9 +/- 13.5 minutes versus 62.2 +/- 19 and 60.9 +/- 17.1 for nurse and resident, respectively; p < 0.05).

CONCLUSIONS

physician extenders could be the perfect complement to gastroenterologists for CE-interpretation but gastroenterologists should supervise their findings. Future cost-efficacy analyses are required to assess the benefits of this alternative.

Functional isocyanide metal complexes as building blocks for supramolecular materials: hydrogen-bonded liquid crystals

Gold, palladium and platinum complexes with an unusual isocyanide ligand containing a carboxylic acid function, [AuCl(CNC(6)H(4)COOH)], cis-[MI(2)(CNC(6)H(4)COOH)(2)] and trans-[MI(2)(CNC(6)H(4)COOH)(2)] (M = Pd, Pt) have been isolated. The carboxylic acid group of the coordinated isocyanide acts as a hydrogen donor for hydrogen-bonding and three series of stable hydrogen-bonded liquid crystalline metal complexes have been prepared with decyloxystilbazole. Although all the metal acid derivatives used are not mesomorphic, and decyloxystilbazole only shows an ordered Smectic E phase, four out of the five hydrogen-bonded decyloxystilbazole complexes studied display enantiotropic smectic A or nematic mesophases. The single crystal X-ray diffraction structure of trans-[PdI(2)(CNC(6)H(4)COOH)(2)].C(4)H(8)O(2) has been determined and confirms the formation of a supramolecular array in the solid state supported by hydrogen-bonding.

[Utility of endoscopy in digestive hemorrhage due to vasculitis]

Vasculitides constitute a heterogeneous group of diseases characterized by inflammation of blood vessels. The skin is mainly affected, although the gastrointestinal tract mucosa can also be involved. The contribution of endoscopy in these cases has not been clearly determined. We report three cases of systemic vasculitis (polyarteritis nodosa, Schonlein-Henoch purpura and Behcet's disease) presenting with acute digestive bleeding. Endoscopy was an effective technique for completing the diagnosis and in establishing an effective nonsurgical therapeutic approach in these potentially lethal cases of gastrointestinal hemorrhage.