Abstract C051: Ceramide signaling regulates PDA aggression through exosome reprogramming of the stroma

Ceramide is a bioactive lipid signaling molecule that regulates multiple cellular processes influencing pancreatic tumor progression and drug response. The pleiotropic role of ceramide signaling in cancer includes modulation of exosome biogenesis and secretion. Smpd3 encodes an enzyme that generates ceramide through hydrolysis of sphingomyelin. Employing the KPC mouse model of pancreatic cancer, we demonstrated that Smpd3 regulates exosome biogenesis in pancreatic ductal adenocarcinoma (PDA) cells and is pro-tumorigenic during PDA progression. Ablation of Smdp3 in KPC mice significantly extends survival by 19% when compared to KPC; Smpd3wt/wt controls. KPC; Smpd3f/f mice display significantly less PanIN and tumor burden compared to KPC; Smpd3wt/wt controls. Lipidomics analysis of epithelial cell lines generated from end-stage pancreatic tumors of KPC; Smpd3f/f and KPC; Smpd3wt/wt mice demonstrated an alteration in hundreds of lipid species including ceramides, triacylglycerides, sphingomyelins, and phosphatidylcholines. Analysis of RNA-seq data of these epithelial cell lines showed a switching of primary tumors from the predominant more aggressive basal-like subtype seen in KPC; Smpd3wt/wt mice to classical in KPC; Smpd3f/f mice. Pathways analysis of our RNA-seq dataset showed an enrichment for genes involved in cellular mechanics and regulation of the tumor microenvironment. To query if Smpd3-generated exosomes have a direct effect on pancreatic tumor progression, we injected KPC; Smpd3wt/wt and KPC; Smpd3f/f mice with exosomes isolated from KPC; Smpd3f/f and KPC; Smpd3wt/wt PDA cell lines. Injection of exosomes derived from KPC; Smpd3f/f mice significantly extended survival of both Smpd3wt/wt and KPC; Smpd3f/f mice when compared to injection of exosomes isolated from KPC; Smpd3wt/wt mice, suggesting an anti-tumorigenic effect of exosomes isolated from Smpd3-deficient PDA cell lines. We observed a decrease in extracellular matrix collagen abundance and fewer activated stellate cells and fibroblasts in KPC; Smpd3f/f compared to control KPC; Smpd3wt/wt pancreata. Abrogation of Smpd3 expression also affected immune cell infiltration, as demonstrated by a significant increase in iNOS+ F4/80+ double positive macrophages in KPC; Smpd3f/f pancreata when compared to KPC; Smpd3wt/wt pancreata. Loss of Smpd3 resulted in a significant reduction in CD31+ endothelial cells in pancreatic tumors of KPC; Smpd3f/f mice when compared to KPC; Smpd3wt/wt mice, which may influence the ability of chemotherapeutics to enter pancreatic tumors. Our patient data demonstrate that high SMPD3 expression in surgically resected, treatment naive PDA significantly correlated with longer patient survival when patients received adjuvant chemotherapy, more than 95% of which was gemcitabine. Collectively, our data show that ceramide-dependent exosomes promote tumorigenesis, specifically activation of stellate cells and fibroblasts – which may in turn induce a stiff, fibrotic, proinflammatory tumor microenvironment that also impedes vasculature formation.

Citation Format: Audrey M. Hendley, Atsushi Urano, Xianlu L. Peng, Sudipta Ashe, Natanya R. Kerper, Tuan A. Phu, Martin Ng, Simone Giacometti, David I. Berrios, Gun H. Jang, Jen J. Yeh, Steven Gallinger, David K. Chang, Andrew V. Biankin, Valerie M. Weaver, Grace E. Kim, David W. Dawson, Robert L. Raffai, Matthias Hebrok. Ceramide signaling regulates PDA aggression through exosome reprogramming of the stroma [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 C051.

Abstract PR-008: Kdm6 demethylases are critical regulators of pancreatic cancer initiation, progression and subtype specification

Aberrant epigenetic regulation is a hallmark of pancreatic cancer. Since changes in histone methylation are potentially reversible, they present an attractive target for therapeutic intervention. Kdm6a and Kdm6b belong to a family of histone demethylases specific for lysine 27 of histone 3 and have been implicated in multiple types of cancer, including pancreatic ductal adenocarcinoma (PDA). We have gathered data from the extensive investigation of a mouse model of PDA in which either Kdm6b or both Kdm6a and Kdm6b have been deleted with concomitant activation of oncogenic KrasG12D restricted to adult acinar cells. While prior work had demonstrated an important role for Kdm6a in PDA formation, our data now show that the closely related Kdm6b is implicated in PDA tumorigenesis as well. Partial or complete loss of Kdm6b results in accelerated acinar-to-ductal metaplasia (ADM) and formation of pancreatic intraepithelial neoplasia (PanIN) with increased inflammation and fibrosis. Accelerated ADM formation was also observed ex vivo upon culturing acinar cells in the absence of oncogenic Kras, indicating that Kdm6b activity is critical for the maintenance of acinar identity and suppresses the early stages of pancreatic neoplasia development. However, only mice heterozygous for Kdm6b continue to exhibit a reduced overall median survival compared to KrasG12D alone, while complete loss of Kdm6b results in a similar overall median survival compared to KrasG12D. This suggests a requirement for oncogenic Kdm6b function during later progression of PanIN to invasive cancer. Conversely, concomitant loss of Kdm6a and Kdm6b protects against ADM and PanIN formation in vivo and ex vivo and double mutants display a trend towards an increased overall median survival compared to mice carrying only the KrasG12D mutation. Strikingly, the resulting tumors of Kdm6a/Kdm6b deficient mice exhibit features of an extremely rare subtype of sarcomatoid pancreatic cancer found in human patients. Taken together, this suggests that Kdm6 demethylase function is required during the initiation and progression of PDA. Furthermore, targeting Kdm6a/Kdm6b with specific inhibitors at distinct stages might provide opportunities for novel treatment avenues for pancreatic cancer.

Citation Format: Laura Leonhardt, Lucia Y. Li, David I. Berrios, Sudipta Ashe, Audrey M. Hendley, Grace E. Kim, Matthias Hebrok. Kdm6 demethylases are critical regulators of pancreatic cancer initiation, progression and subtype specification [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PR-008.

Single-cell transcriptome analysis defines heterogeneity of the murine pancreatic ductal tree

To study disease development, an inventory of an organ's cell types and understanding of physiologic function is paramount. Here, we performed single-cell RNA-sequencing to examine heterogeneity of murine pancreatic duct cells, pancreatobiliary cells, and intrapancreatic bile duct cells. We describe an epithelial-mesenchymal transitory axis in our three pancreatic duct subpopulations and identify osteopontin as a regulator of this fate decision as well as human duct cell dedifferentiation. Our results further identify functional heterogeneity within pancreatic duct subpopulations by elucidating a role for geminin in accumulation of DNA damage in the setting of chronic pancreatitis. Our findings implicate diverse functional roles for subpopulations of pancreatic duct cells in maintenance of duct cell identity and disease progression and establish a comprehensive road map of murine pancreatic duct cell, pancreatobiliary cell, and intrapancreatic bile duct cell homeostasis.

Abstract C20: Smpd3 augments chemotherapy and thwarts PDA progression

Deregulated sphingolipid metabolism alters pancreatic cancer progression; for that reason, bioactive lipid signaling molecules such as ceramide show promise as both biomarkers for disease progression and novel therapeutic targets. Intracellular ceramide levels are critical for regulating cellular senescence, apoptosis, and cell cycle arrest in response to stress stimuli such as chemotherapeutics. Our data show Sphingomyelin Phosphodiesterase 3 (Smpd3), a regulator of ceramide synthesis and exosome biogenesis, has a protumorigenic function in pancreatic ductal adenocarcinoma (PDA). Immunodeficient mice orthotopically implanted with Smpd3-deficient PDA cell lines demonstrate significantly reduced tumor burden and longer survival when compared with controls. This observation was mirrored by our KPC; Smpd3f/f mouse model, in which loss of Smpd3 expression significantly correlated with longer survival and decreased metastasis when compared to KPC; Smpd3wt/wt controls. Analysis of SMPD3 in PDA patients revealed that low SMPD3 RNA and protein expression is significantly associated with worse survival. Because chemotherapeutics have been shown to affect expression and function of SMPD3, we stratified patient cohorts into individuals who received adjuvant chemotherapy, more than 95% of which was gemcitabine, and those who did not receive adjuvant chemotherapy. We found that high SMPD3 expression in surgically resected PDA significantly correlated with longer patient survival only in patients receiving adjuvant chemotherapy, and not in the no-adjuvant-chemotherapy group. These data suggest an interaction between adjuvant chemotherapy with gemcitabine and SMPD3 expression. Furthermore, we found that gemcitabine stimulates both the enzymatic activity and expression of SMPD3 in vitro in a panel of human PDA cell lines. Our results suggest a crucial role for SMPD3 in facilitating a protumorigenic environment during PDA progression and implicate SMPD3 as a potential novel biomarker for guiding individualized chemotherapeutic regimens for PDA patients.

Citation Format: Audrey M. Hendley, Atsushi Urano, Natanya R. Kerper, Phat Duong, Peter Bailey, David K. Chang, Andrew V. Biankin, David W. Dawson, Grace Kim, Robert L. Raffai, Matthias Hebrok. Smpd3 augments chemotherapy and thwarts PDA progression [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 C20.

Expression of Activated Ras in Gastric Chief Cells of Mice Leads to the Full Spectrum of Metaplastic Lineage Transitions

BACKGROUND & AIMS

Gastric cancer develops in the context of parietal cell loss, spasmolytic polypeptide-expressing metaplasia (SPEM), and intestinal metaplasia (IM). We investigated whether expression of the activated form of Ras in gastric chief cells of mice leads to the development of SPEM, as well as progression of metaplasia.

METHODS

We studied Mist1-CreERT2Tg/+;LSL-K-Ras(G12D)Tg/+ (Mist1-Kras) mice, which express the active form of Kras in chief cells on tamoxifen exposure. We studied Mist1-CreERT2Tg/+;LSL-KRas (G12D)Tg/+;R26RmTmG/+ (Mist1-Kras-mTmG) mice to examine whether chief cells that express active Kras give rise to SPEM and IM. Some mice received intraperitoneal injections of the Mitogen-activated protein kinase kinase (MEK) inhibitor, selumetinib, for 14 consecutive days. Gastric tissues were collected and analyzed by immunohistochemistry, immunofluorescence, and quantitative polymerase chain reaction.

RESULTS

Mist1-Kras mice developed metaplastic glands, which completely replaced normal fundic lineages and progressed to IM within 3-4 months after tamoxifen injection. The metaplastic glands expressed markers of SPEM and IM, and were infiltrated by macrophages. Lineage tracing studies confirmed that the metaplasia developed directly from Kras (G12D)-induced chief cells. Selumetinib induced persistent regression of SPEM and IM, and re-established normal mucosal cells, which were derived from normal gastric progenitor cells.

CONCLUSIONS

Expression of activated Ras in chief cells of Mist1-Kras mice led to the full range of metaplastic lineage transitions, including SPEM and IM. Inhibition of Ras signaling by inhibition of MEK might reverse preneoplastic metaplasia in the stomach.

p120 Catenin Suppresses Basal Epithelial Cell Extrusion in Invasive Pancreatic Neoplasia

Aberrant regulation of cellular extrusion can promote invasion and metastasis. Here, we identify molecular requirements for early cellular invasion using a premalignant mouse model of pancreatic cancer with conditional knockout of p120 catenin (Ctnnd1). Mice with biallelic loss of p120 catenin progressively develop high-grade pancreatic intraepithelial neoplasia (PanIN) lesions and neoplasia accompanied by prominent acute and chronic inflammatory processes, which is mediated, in part, through NF-κB signaling. Loss of p120 catenin in the context of oncogenic Kras also promotes remarkable apical and basal epithelial cell extrusion. Abundant single epithelial cells exit PanIN epithelium basally, retain epithelial morphology, survive, and display features of malignancy. Similar extrusion defects are observed following p120 catenin knockdown in vitro, and these effects are completely abrogated by the activation of S1P/S1pr2 signaling. In the context of oncogenic Kras, p120 catenin loss significantly reduces expression of genes mediating S1P/S1pr2 signaling in vivo and in vitro, and this effect is mediated at least, in part, through activation of NF-κB. These results provide insight into mechanisms controlling early events in the metastatic process and suggest that p120 catenin and S1P/S1pr2 signaling enhance cancer progression by regulating epithelial cell invasion. Cancer Res; 76(11); 3351-63. ©2016 AACR.

p53 mutations cooperate with oncogenic Kras to promote adenocarcinoma from pancreatic ductal cells

Pancreatic cancer is one of the most lethal malignancies, with virtually all patients eventually succumbing to their disease. Mutations in p53 have been documented in >50% of pancreatic cancers. Owing to the high incidence of p53 mutations in PanIN 3 lesions and pancreatic tumors, we interrogated the comparative ability of adult pancreatic acinar and ductal cells to respond to oncogenic Kras and mutant Tp53(R172H) using Hnf1b:CreER(T2) and Mist1:CreER(T2) mice. These studies involved co-activation of a membrane-tethered GFP lineage label, allowing for direct visualization and isolation of cells undergoing Kras and mutant p53 activation. Kras activation in Mist1(+) adult acinar cells resulted in brisk PanIN formation, whereas no evidence of pancreatic neoplasia was observed for up to 6 months following Kras activation in Hnf1beta(+) adult ductal cells. In contrast to the lack of response to oncogenic Kras alone, simultaneous activation of Kras and mutant p53 in adult ductal epithelium generated invasive PDAC in 75% of mice as early as 2.5 months after tamoxifen administration. These data demonstrate that pancreatic ductal cells, whereas exhibiting relative resistance to oncogenic Kras alone, can serve as an effective cell of origin for pancreatic ductal adenocarcinoma in the setting of gain-of-function mutations in p53.

Abstract 4186: p120 catenin: A novel regulator of epithelial cell delamination in early Kras-driven pancreatic cancer

By 2020, pancreatic cancer is estimated to climb from the 4th to the 2nd most common cause of cancer-related deaths in the United States. This deadly disease has continued to remain largely refractory to chemotherapeutic and treatment regimens, and patients often experience a heavy metastatic burden. A study combining the Sleeping beauty transposon random insertion mutagenesis system with an oncogenic KrasG12D allele in mice as a screen to identify candidate pancreatic cancer genes identified genes enriched in adherens and tight junctions as significantly enriched in Kras-driven neoplasia with Ctnnd1 as a locus commonly mutated in mice developing metastatic progression of pancreatic cancer. Ctnnd1 encodes the adherens junction protein p120 catenin, which is integral in stabilization of cadherin molecules at cell membranes. p120 catenin is misexpressed in an estimated 60% primary pancreatic tumors and low/absent expression levels and predominant cytoplasmic localization of p120 catenin in primary resected pancreatic tumors correlates with worse survival in pancreatic cancer patients. Yet, the mechanisms by which p120 catenin contributes to the pathogenesis of pancreatic cancer are not clear. We have comprehensively examined p120 catenin staining in human Pancreatic Intraepithelial Neoplasia (PanIN) and identified mislocalization of p120 catenin to the cytoplasm as early as PanIN2. 3/5 PanIN3 examined had predominant cytoplasmic staining, which led us to hypothesize that p120 catenin might play a critical role in early pancreatic neoplasia, before the onset of Pancreatic Ductal Adenocarcinoma. To examine the role of p120 catenin during early Kras-driven pancreatic neoplasia, we ablated p120 catenin in a mouse model of preinvasive pancreatic cancer, KCiMist1. KCiMist1p120f/f pancreases display significant acceleration of acinar to ductal metaplasia (ADM) and PanIN formation when compared to KCiMist1p120wt/wt pancreases one month post tamoxifen injection. KCiMist1p120f/f pancreases are significantly larger than KCiMist1p120wt/wt pancreases with 92.89% pancreatic area occupied by Fibrostroma one month post tamoxifen injection. As a result, KCiMist1p120f/f animals have severe exocrine pancreatic insufficiency and die on average 8 weeks earlier than their KCiMist1p120wt/wt controls. Lineage tracing revealed a prominent epithelial cell delamination phenotype in KCiMist1p120f/f pancreases. Quantification of epithelial cells in the extensive stroma revealed a striking 832/7000 CK19+ cells in KCiMist1p120f/f pancreases vs 15/7000 CK19+ cells in KCiMist1p120wt/wt pancreases. Microarray analysis showed >1263 differentially expressed genes! IPA pathway analysis revealed significant gene expression changes in PI3K/AKT and Cdc42 signaling. Taken together, our results suggest a critical role for p120 catenin in regulating epithelial cell delamination in early pancreatic cancer.

Citation Format: Audrey M. Hendley, Yue J. Wang, Janivette Alsina, Ishrat Ahmed, Hao Zhang, Samuel Savidge, Hao Ho, Albert Reynolds, Anirban Maitra, Michael Goggins, Christine Iacobuzio-Donahue, Steven D. Leach, Jennifer M. Bailey. p120 catenin: A novel regulator of epithelial cell delamination in early Kras-driven pancreatic cancer. [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 4186. doi:10.1158/1538-7445.AM2015-4186

p120 Catenin is required for normal tubulogenesis but not epithelial integrity in developing mouse pancreas

The intracellular protein p120 catenin aids in maintenance of cell-cell adhesion by regulating E-cadherin stability in epithelial cells. In an effort to understand the biology of p120 catenin in pancreas development, we ablated p120 catenin in mouse pancreatic progenitor cells, which resulted in deletion of p120 catenin in all epithelial lineages of the developing mouse pancreas: islet, acinar, centroacinar, and ductal. Loss of p120 catenin resulted in formation of dilated epithelial tubules, expansion of ductal epithelia, loss of acinar cells, and the induction of pancreatic inflammation. Aberrant branching morphogenesis and tubulogenesis were also observed. Throughout development, the phenotype became more severe, ultimately resulting in an abnormal pancreas comprised primarily of duct-like epithelium expressing early progenitor markers. In pancreatic tissue lacking p120 catenin, overall epithelial architecture remained intact; however, actin cytoskeleton organization was disrupted, an observation associated with increased cytoplasmic PKCζ. Although we observed reduced expression of adherens junction proteins E-cadherin, β-catenin, and α-catenin, p120 catenin family members p0071, ARVCF, and δ-catenin remained present at cell membranes in homozygous p120(f/f) pancreases, potentially providing stability for maintenance of epithelial integrity during development. Adult mice homozygous for deletion of p120 catenin displayed dilated main pancreatic ducts, chronic pancreatitis, acinar to ductal metaplasia (ADM), and mucinous metaplasia that resembles PanIN1a. Taken together, our data demonstrate an essential role for p120 catenin in pancreas development.

Dicer is required for maintenance of adult pancreatic acinar cell identity and plays a role in Kras-driven pancreatic neoplasia

The role of miRNA processing in the maintenance of adult pancreatic acinar cell identity and during the initiation and progression of pancreatic neoplasia has not been studied in detail. In this work, we deleted Dicer specifically in adult pancreatic acinar cells, with or without simultaneous activation of oncogenic Kras. We found that Dicer is essential for the maintenance of acinar cell identity. Acinar cells lacking Dicer showed increased plasticity, as evidenced by loss of polarity, initiation of epithelial-to-mesenchymal transition (EMT) and acinar-to-ductal metaplasia (ADM). In the context of oncogenic Kras activation, the initiation of ADM and pancreatic intraepithelial neoplasia (PanIN) were both highly sensitive to Dicer gene dosage. Homozygous Dicer deletion accelerated the formation of ADM but not PanIN. In contrast, heterozygous Dicer deletion accelerated PanIN initiation, revealing complex roles for Dicer in the regulation of both normal and neoplastic pancreatic epithelial identity.

Abstract 66: p120 catenin: A novel regulator of PanIN epithelial cell delamination in preinvasive pancreatic cancer

Pancreatic cancer is among the deadliest human malignancies ranking 4th in the United States for cancer-related deaths among both men and women. Due to the invasive nature of pancreatic cancer, metastasis to the lymphatic system and distant organs is a major contributor to pancreatic cancer-related death. Genetic alterations in cell adhesion molecules contribute to human disease including developmentally related syndromes and cancer. In a sequencing study of 24 primary pancreatic tumor exomes published by the Hopkins pancreatic cancer team in 2008, 79% of tumors had at least one mutation in a homophilic cell adhesion molecule, and this class of molecules was named as one of the twelve core signaling pathways in pancreatic cancer. Among this class of cell adhesion molecules are adherens junctions. Mislocalization of the adherens protein p120 catenin has been identified in almost all of the major types of human carcinomas including pancreatic cancer. An accumulating body of evidence has identified p120 catenin as a prognostic marker in pancreatic cancer. Based on relevant literature, we hypothesize that misexpression and mislocalization of p120 catenin in pancreatic cancer is pathologic in the progression of this deadly disease. To test this hypothesis, we have ablated p120 catenin in the KCiMist1 mouse model of pancreatic cancer. The KCiMist1 mouse model activates oncogenic Kras in adult pancreatic acinar cells and displays the preinvasive PanIN 1 - PanIN 3 lesions in a manner that faithfully recapitulates the human disease. Homozygous deletion of p120 catenin in this model resulted in an almost complete replacement of acinar cells by acinar to ductal metaplastic lesions, accelerated PanIN formation, and stromal infiltration at 1 month. At 2 months, the stromal infiltrate persists, and we see considerable evidence of fibrosis and fatty deposition in the pancreas, which are pathologic features of pancreatitis. We used the KCiMist1Gp120f/f model to trace the lineage of acinar cells undergoing Kras activation and p120 catenin excision, and observed a marked increase in isolated GFP+ Ecadherin+ cells located in the extensive stroma at 1 and 2 months suggesting that p120 catenin normally restrains PanIN epithelial cell delamination. We have begun to study potential mechanisms for this delamination phenotype including epithelial-mesenchymal transition (EMT) and non-EMT based mechanisms. Research suggests that EMT is a contributing factor to the development of drug resistance, which makes EMT a promising target for the development of future therapies that reduce invasion and drug resistance leading to better prognosis for patients with pancreatic cancer. Our preliminary findings suggest that the KCiMist1Gp120f/f mouse model represents a valuable tool to study both EMT and non-EMT based mechanisms for PanIN epithelial cell delamination.

Citation Format: Audrey M. Hendley, Jennifer M. Bailey, Janivette Alsina, Christine Iacobuzio-Donahue, Anirban Maitra, Albert Reynolds, Steven D. Leach. p120 catenin: A novel regulator of PanIN epithelial cell delamination in preinvasive pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 66. doi:10.1158/1538-7445.AM2014-66