Abstract IA21: Myeloid cells are required for PD-1/PD-L1 checkpoint activation and the establishment of an immune-suppressive environment in pancreatic cancer

Pancreatic cancer is characterized by the accumulation of a fibro-inflammatory stroma. Accumulation of the stroma is already evident surrounding Pancreatic Intraepithelial Neoplasias (PanINs), common precursor lesions to pancreatic cancer (Hezel et al., 2006). The stroma is abundantly infiltrated by immune cells, and myeloid cells are a predominant population (Clark et al., 2007). Different myeloid subsets have been correlated with tumor promotion and unmasking of anti-tumor immunity (Liou et al., 2015; Long et al., 2016; Mitchem et al., 2013; Stromnes et al., 2014). Both PanINs and pancreatic cancer and commonly associated with oncogenic mutations in the Kras gene (Biankin et al., 2012; Jones et al., 2010; Kanda et al., 2012). Expression of oncogenic Kras in the pancreas of genetically engineered mice recapitulates the PanIN to pancreatic cancer progression, including the accumulation of fibrotic stroma (Hingorani et al., 2003). We have described a mouse model that allows inducible and reversible expression of oncogenic Kras in the pancreas, the iKras* mouse. Inactivation of oncogenic Kras during the PanIN stage or in cancer leads to regression of the epithelial lesions as well as to remodeling of the stroma, indicating that the accumulation of the stroma is regulated by signals derived from oncogenic Kras-expressing epithelial cells (Collins et al., 2012a).

In the current study, we have investigated the interaction between epithelial cells and myeloid cells that infiltrate the pancreas. For this purpose, we have used a combination of genetically engineered mice (iKras*p53* mice (Collins et al., 2012b)) and transplantation approaches into CD11b-DTR mice (Duffield et al., 2005), that allow depletion of myeloid cells upon administration of Diphtheria Toxin. Our results show that the infiltration and polarization of macrophages in the pancreas depends on signals derived from oncogenic Kras-expressing epithelial cells, either directly or through activation of a pro-inflammatory subset of stromal fibroblasts. Conversely, myeloid cells infiltration is required for the progression of PanINs and pancreatic cancer. Depletion of myeloid cells prevented KrasG12D driven pancreatic cancer initiation. In pre-established tumors, myeloid cell depletion resulted in arrest of growth or tumor regression. We observed that tumor progression was dependent on myeloid cell-mediated blockade of CD8+ T cell anti-tumor activity. Furthermore, myeloid cells regulate the expression of the Programmed death-ligand 1 (PD-L1) in tumor cells in an EGFR/MAPK dependent manner.

Our results show that myeloid cells regulate a complex network of signals that ensure immune suppression within the pancreatic cancer microenvironment. Moreover, we show that depletion of the myeloid cell population restores anti-tumor immunity mediated by CD8+ T cells, a finding with implications for the design of immune therapies for pancreatic cancer.

References:

Biankin, A. V., Waddell, N., Kassahn, K. S., Gingras, M. C., Muthuswamy, L. B., Johns, A. L., Miller, D. K., Wilson, P. J., Patch, A. M., Wu, J., et al. (2012). Pancreatic cancer genomes reveal aberrations in axon guidance pathway genes. Nature 491, 399-405.

Clark, C. E., Hingorani, S. R., Mick, R., Combs, C., Tuveson, D. A., and Vonderheide, R. H. (2007). Dynamics of the immune reaction to pancreatic cancer from inception to invasion. Cancer Res 67, 9518-9527.

Collins, M. A., Bednar, F., Zhang, Y., Brisset, J. C., Galban, S., Galban, C. J., Rakshit, S., Flannagan, K. S., Adsay, N. V., and Pasca di Magliano, M. (2012a). Oncogenic Kras is required for both the initiation and maintenance of pancreatic cancer in mice. J Clin Invest 122, 639-653.

Collins, M. A., Brisset, J. C., Zhang, Y., Bednar, F., Pierre, J., Heist, K. A., Galban, C. J., Galban, S., and di Magliano, M. P. (2012b). Metastatic pancreatic cancer is dependent on oncogenic Kras in mice. PLoS One 7, e49707.

Duffield, J. S., Forbes, S. J., Constandinou, C. M., Clay, S., Partolina, M., Vuthoori, S., Wu, S., Lang, R., and Iredale, J. P. (2005). Selective depletion of macrophages reveals distinct, opposing roles during liver injury and repair. J Clin Invest 115, 56-65.

Hezel, A. F., Kimmelman, A. C., Stanger, B. Z., Bardeesy, N., and Depinho, R. A. (2006). Genetics and biology of pancreatic ductal adenocarcinoma. Genes Dev 20, 1218-1249.

Hingorani, S. R., Petricoin, E. F., Maitra, A., Rajapakse, V., King, C., Jacobetz, M. A., Ross, S., Conrads, T. P., Veenstra, T. D., Hitt, B. A., et al. (2003). Preinvasive and invasive ductal pancreatic cancer and its early detection in the mouse. Cancer Cell 4, 437-450.

Jones, S., Wang, T. L., Shih Ie, M., Mao, T. L., Nakayama, K., Roden, R., Glas, R., Slamon, D., Diaz, L. A., Jr., Vogelstein, B., et al. (2010). Frequent mutations of chromatin remodeling gene ARID1A in ovarian clear cell carcinoma. Science 330, 228-231.

Kanda, M., Matthaei, H., Wu, J., Hong, S. M., Yu, J., Borges, M., Hruban, R. H., Maitra, A., Kinzler, K., Vogelstein, B., and Goggins, M. (2012). Presence of somatic mutations in most early-stage pancreatic intraepithelial neoplasia. Gastroenterology 142, 730-733 e739.

Liou, G. Y., Doppler, H., Necela, B., Edenfield, B., Zhang, L., Dawson, D. W., and Storz, P. (2015). Mutant KRAS-induced expression of ICAM-1 in pancreatic acinar cells causes attraction of macrophages to expedite the formation of precancerous lesions. Cancer Discov 5, 52-63.

Long, K. B., Gladney, W. L., Tooker, G. M., Graham, K., Fraietta, J. A., and Beatty, G. L. (2016). IFNgamma and CCL2 Cooperate to Redirect Tumor-Infiltrating Monocytes to Degrade Fibrosis and Enhance Chemotherapy Efficacy in Pancreatic Carcinoma. Cancer Discov.

Mitchem, J. B., Brennan, D. J., Knolhoff, B. L., Belt, B. A., Zhu, Y., Sanford, D. E., Belaygorod, L., Carpenter, D., Collins, L., Piwnica-Worms, D., et al. (2013). Targeting tumor-infiltrating macrophages decreases tumor-initiating cells, relieves immunosuppression, and improves chemotherapeutic responses. Cancer Res 73, 1128-1141.

Stromnes, I. M., Brockenbrough, J. S., Izeradjene, K., Carlson, M. A., Cuevas, C., Simmons, R. M., Greenberg, P. D., and Hingorani, S. R. (2014). Targeted depletion of an MDSC subset unmasks pancreatic ductal adenocarcinoma to adaptive immunity. Gut.

Citation Format: Yaqing Zhang, Esha Mathew, Ashley Velez-Delgado, Kristen B. Long, Dongjun Li, Flor M. Mendez, Kevin Flannagan, Andrew D. Rhim, Diane M. Simeone, Gregory L. Beatty, Marina Pasca di Magliano.{Authors}. Myeloid cells are required for PD-1/PD-L1 checkpoint activation and the establishment of an immune-suppressive environment in pancreatic cancer [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 IA21.

Abstract A62: ATDC is required for KRAS-induced pancreatic tumorigenesis

We have recently demonstrated that ATDC, a novel oncogenic protein, serves as an invasive switch in pancreatic cancer (PDA) by activation of beta–catenin signaling and upregulation of CD44, resulting in EMT and an invasive phenotype during PanIN progression. To further explore the tumorigenic function of ATDC, we generated a floxed ATDC mouse (A F/F) to evaluate the impact of conditional knockout of ATDC on oncogenic Kras-induced PDA initiation and progression. Pancreas-specific ATDC knockout did not cause any histologic abnormalities in pancreas, up to 1 year of age (n=8). Through a series of crosses of LSL-KrasG12D (K), p53F/+ (P), RosaYFP (Y), Pdx1-Cre (C) and AF/F mice, KrasG12D; CY (KCY); KrasG12D; p53+/-; CY (KPCY), KCYA-/- KPCYA-/- mice were generated. Knockout of ATDC in KPCY mice completely prevented the development of ADM and PanIN lesions in 3 month old mice (n= 8), and resulted in the formation of very rare ADM and PanIN1 lesions (2 out of 8) in KPCYA-/- mice at 12 months of age (n=8). In contrast, all KPCY mice developed extensive PanIN (low and high grade) at 3 months of age (n= 8), with the subsequent development of invasive and metastatic cancer at frequencies similar to that reported in the literature. To determine the possible mechanisms by which ATDC inhibited KrasG12D-induced acinar-ductal metaplasia (ADM), we isolated acini from 1.5 month old KCY and KCYA-/- pancreata and performed in vitro 3D cultures and ADM assays. ADM lesions readily formed in 3-D cultures of acini from KCY mice at 5 days, and this was significantly inhibited in acini isolated from KCYA-/- mice (duct-like structures: 95.1±3.5% to 28.0±2.2%*, KCY vs KCYA-/-, n=3, *p<0.05). Expression of ATDC specific shRNA in acini from KCY mice also effectively decreased ADM formation in 3D culture, an effect that was completely reversed by ATDC overexpression using an ATDC-shRNA-resistant expression vector. To further evaluate the role of ATDC in ADM and PanIN formation, we induced caerulein-mediated acute pancreatitis in 1.5 month old WT, CYA-/-, KCY, KCYA-/- mice and analyzed pancreatic tissue 1 and 7 days following cerulein treatment. 1 day post-caerulein treatment, KCY, KCYA-/-, CYA-/- and WT mice exhibited widespread ADM, which was replaced by normal acini by 7 days in WT, CYA-/- and KCYA-/- mice. However, in KCY mice 7 days post-cerulein treatment, extensive ADM and PanIN lesions were present, suggesting that ATDC is required for oncogenic KRAS to promote ADM and PanIN formation. Conclusions: Knockout of ATDC markedly reduces KrasG12D-induced ADM and PanIN formation, highlighting a key biologic function for ATDC in this process and its role in driving progression of KRAS-induced tumorigenesis in the pancreas.

Citation Format: Lidong Wang, Huibin Yang, Ethan V. Abel, Phillip L. Palmbos, Christophe Halbrook, Kenneth Takeuchi, Jiaqi Shi, Yaqing Zhang, Sumithra Urs, Meghna Waghray, Marina Pasca di Magliano, Andrew D. Rhim, Howard C. Crawford, Diane M. Simeone.{Authors}. ATDC is required for KRAS-induced pancreatic tumorigenesis. [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 A62.

Can Stopping Nerves, Stop Cancer?

The nervous system is viewed as a tissue affected by cancer and as a conduit for the transmission of cancer pain and perineural invasion. Here, we review recent studies that indicate a more direct role. Several studies have shown that reducing stress or suppressing sympathetic drive correlates with improved outcomes and prolonged survival. Recent studies using animal models of visceral and somatic cancer further support a role for the nervous system in cancer progression. Specifically, nerve ablation had a profound impact on disease progression, including delayed development of precancerous lesions, and decreased tumor growth and metastasis. In this review, we summarize new evidence and discuss how future studies may address the role of neural signaling in the modulation of tumorigenesis.

Abstract A096: Myeloid cells are required for pancreatic carcinogenesis and PD-1/PD-L1 checkpoint activation

Myeloid cells, including both macrophages and immature myeloid cells/myeloid derived suppressor cells (MDSCs), accumulate during the progression of pancreatic cancer. The goal of this study was to determine the effect of myeloid cell depletion on the onset and progression of pancreatic cancer, and to understand the relationship between myeloid cells and T cell-mediated immunity within the pancreatic cancer microenvironment.

Primary mouse pancreatic cancer cells were transplanted into CD11b-DTR mice. Alternatively, the iKras* mouse model of pancreatic cancer was crossed into CD11b-DTR mice. CD11b+ cells were depleted by Diphtheria Toxin treatment during tumor initiation or in established tumors. Depletion of myeloid cells prevented KrasG12D driven pancreatic cancer initiation.

Myeloid cells are required for sustained MAPK signaling in pancreatic epithelial cells during the onset of carcinogenesis, notwithstanding the expression of oncogenic Kras. In pre-established tumors, myeloid cell depletion arrested tumor growth and in some cases, induced tumor regressions that were dependent on CD8+ T cells. We found that myeloid cells inhibited CD8+ T cell anti-tumor activity by inducing the expression of Programmed cell death-ligand 1 (PD-L1) in tumor cells in an EGFR/MAPK dependent manner. Treatment with MEK inhibitors lowers the intratumoral expression of PD-L1 and renders the tumor susceptible to PD-1 blockade.

Our results show that myeloid cells support immune evasion in pancreatic cancer through EGFR/MAPK dependent regulation of PD-L1 expression on tumor cells. Derailing this cross-talk between myeloid cells and tumor cells is sufficient to restore anti-tumor immunity mediated by CD8+ T cells, a finding with implications for the design of immune therapies for pancreatic cancer.

Note: This abstract was not presented at the conference.

Citation Format: Yaqing Zhang, Ashley Velez-Delgado, Esha Mathew, Dongjun Li, Flor M. Mendez, Kevin Flannagan, Andrew D. Rhim, Diane M. Simeone, Gregory L. Beatty, Marina Pasca di Magliano. Myeloid cells are required for pancreatic carcinogenesis and PD-1/PD-L1 checkpoint activation [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A096.

Adipocytes promote pancreatic cancer cell proliferation via glutamine transfer

Adipocytes promote progression of multiple cancers, but their role in pancreatic intraepithelial neoplasia (PanIN) and ductal adenocarcinoma (PDAC) is poorly defined. Nutrient transfer is a mechanism underlying stromal cell-cancer crosstalk. We studied the role of adipocytes in regulating in vitro PanIN and PDAC cell proliferation with a focus on glutamine metabolism. Murine 3T3L1 adipocytes were used to model adipocytes. Cell lines derived from PKCY mice were used to model PanIN and PDAC. Co-culture was used to study the effect of adipocytes on PanIN and PDAC cell proliferation in response to manipulation of glutamine metabolism. Glutamine secretion was measured with a bioanalyzer. Western blotting was used to study the effect of PanIN and PDAC cells on expression of glutamine-related enzymes in adipocytes. Adipocytes promote proliferation of PanIN and PDAC cells, an effect that was amplified in nutrient-poor conditions. Adipocytes secrete glutamine and rescue PanIN and PDAC cell proliferation in the absence of glutamine, an effect that was glutamine synthetase-dependent and involved PDAC cell-induced down-regulation of glutaminase expression in adipocytes. These findings suggest glutamine transfer as a potential mechanism underlying adipocyte-induced PanIN and PDAC cell proliferation.

Ablation of sensory neurons in a genetic model of pancreatic ductal adenocarcinoma slows initiation and progression of cancer

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an exuberant inflammatory desmoplastic response. The PDAC microenvironment is complex, containing both pro- and antitumorigenic elements, and remains to be fully characterized. Here, we show that sensory neurons, an under-studied cohort of the pancreas tumor stroma, play a significant role in the initiation and progression of the early stages of PDAC. Using a well-established autochthonous model of PDAC (PKC), we show that inflammation and neuronal damage in the peripheral and central nervous system (CNS) occurs as early as the pancreatic intraepithelial neoplasia (PanIN) 2 stage. Also at the PanIN2 stage, pancreas acinar-derived cells frequently invade along sensory neurons into the spinal cord and migrate caudally to the lower thoracic and upper lumbar regions. Sensory neuron ablation by neonatal capsaicin injection prevented perineural invasion (PNI), astrocyte activation, and neuronal damage, suggesting that sensory neurons convey inflammatory signals from Kras-induced pancreatic neoplasia to the CNS. Neuron ablation in PKC mice also significantly delayed PanIN formation and ultimately prolonged survival compared with vehicle-treated controls (median survival, 7.8 vs. 4.5 mo; P = 0.001). These data establish a reciprocal signaling loop between the pancreas and nervous system, including the CNS, that supports inflammation associated with oncogenic Kras-induced neoplasia. Thus, pancreatic sensory neurons comprise an important stromal cell population that supports the initiation and progression of PDAC and may represent a potential target for prevention in high-risk populations.

A randomized phase II dose-response exercise trial among colon cancer survivors: Purpose, study design, methods, and recruitment results

BACKGROUND

Observational studies indicate that higher volumes of physical activity are associated with improved disease outcomes among colon cancer survivors. The aim of this report is to describe the purpose, study design, methods, and recruitment results of the courage trial, a National Cancer Institute (NCI) sponsored, phase II, randomized, dose-response exercise trial among colon cancer survivors.

METHODS/RESULTS

The primary objective of the courage trial is to quantify the feasibility, safety, and physiologic effects of low-dose (150 min·week(-1)) and high-dose (300 min·week(-1)) moderate-intensity aerobic exercise compared to usual-care control group over six months. The exercise groups are provided with in-home treadmills and heart rate monitors. Between January and July 2015, 1433 letters were mailed using a population-based state cancer registry; 126 colon cancer survivors inquired about participation, and 39 were randomized onto the study protocol. Age was associated with inquiry about study participation (P<0.001) and randomization onto the study protocol (P<0.001). No other demographic, clinical, or geographic characteristics were associated with study inquiry or randomization. The final trial participant was randomized in August 2015. Six month endpoint data collection was completed in February 2016.

DISCUSSION

The recruitment of colon cancer survivors into an exercise trial is feasible. The findings from this trial will inform key design aspects for future phase 2 and phase 3 randomized controlled trials to examine the efficacy of exercise to improve clinical outcomes among colon cancer survivors.

Orthotopic Injection of Pancreatic Cancer Cells

Pancreatic ductal adenocarcinoma is an aggressive disease with a 5-yr survival rate of only 5%. The location of the pancreas in the abdomen, where it is obscured by other organs, makes it a difficult tissue to study and manipulate. This protocol describes in detail how to orthotopically inject cancer cells into the pancreas in mice. This technique is particularly useful when the cells must be manipulated in ways that cannot be modeled genetically.

Isolating Epithelial and Epithelial-to-Mesenchymal Transition Populations from Primary Tumors by Fluorescence-Activated Cell Sorting

Transgenic mice that express conditional reporters allow for the isolation of specific cell lineages. These cells can be further stratified by gene expression and collected by fluorescence-activated cell sorting (FACS) for further analysis. Using Cre-recombinase (Cre) technology we have generated a transgenic mouse line termed PKCY in which all pancreatic epithelial cells and therefore all pancreatic cancer cells are constitutively labeled with yellow fluorescent protein (YFP). We have used immunofluorescent staining for E-cadherin to divide the YFP(+) tumor population into epithelial cells (E-cadherin positive) and cells that have undergone an epithelial-to-mesenchymal transition (EMT; E-cadherin negative). This protocol describes how to prepare a tumor sample for FACS, with an emphasis on separating epithelial and EMT populations. These cells can then be used for a number of applications including, but not limited to, the generation of cell lines, gene-expression analysis by quantitative polymerase chain reaction (qPCR) or RNA sequencing, DNA sequencing, chromatin immunoprecipitation, and western blots.

Whole Genome Sequencing Defines the Genetic Heterogeneity of Familial Pancreatic Cancer

Pancreatic cancer is projected to become the second leading cause of cancer-related death in the United States by 2020. A familial aggregation of pancreatic cancer has been established, but the cause of this aggregation in most families is unknown. To determine the genetic basis of susceptibility in these families, we sequenced the germline genomes of 638 patients with familial pancreatic cancer and the tumor exomes of 39 familial pancreatic adenocarcinomas. Our analyses support the role of previously identified familial pancreatic cancer susceptibility genes such as BRCA2, CDKN2A, and ATM, and identify novel candidate genes harboring rare, deleterious germline variants for further characterization. We also show how somatic point mutations that occur during hematopoiesis can affect the interpretation of genome-wide studies of hereditary traits. Our observations have important implications for the etiology of pancreatic cancer and for the identification of susceptibility genes in other common cancer types.

SIGNIFICANCE

The genetic basis of disease susceptibility in the majority of patients with familial pancreatic cancer is unknown. We whole genome sequenced 638 patients with familial pancreatic cancer and demonstrate that the genetic underpinning of inherited pancreatic cancer is highly heterogeneous. This has significant implications for the management of patients with familial pancreatic cancer.

Abstract 1572: Sensitive and robust targeted sequencing of pancreatic precancer and tumors using microfluidic single-molecule enrichment

Pancreatic ductal adenocarcinoma (PDAC) arises from two precursor lesions, pancreatic intraepithelial neoplasias and pancreatic cysts, such as intraductal papillary mucinous neoplasias (IPMNs). Since cyst lesions are readily detected on cross sectional imaging, early diagnosis of IPMN-associated PDAC and intervention may be feasible. However, clinical guidelines dictating which IPMNs are high-risk and require surgical resection are suboptimal. Recently, the genomic signature of IPMN-associated carcinomas has been described opening the possibility for targeted genomic analysis. Previous groups have sought to achieve this using conventional methods. However, since IPMN tissue and cyst fluid are limited in quantity and contain inhibitors of PCR, we developed a novel microfluidics-based approach to achieve sensitive and specific targeted amplification and Illumina library construction.

We have optimized a novel method to enrich targeted genomic regions for next generation sequencing (NGS) platforms featuring microfluidic partitioning of the sample into uniform picoliter volume droplets containing single molecules of target DNA. All droplets contain all of the primers and PCR reagents, ensuring that every target molecule from the sample is amplified, and after endpoint PCR results in a highly uniform yield that facilitates efficient use of the NGS platform. In addition, the primers contain ‘Illumina tails’ that enable easy sample indexing and loading directly onto a MiSeq without additional library preparation.

Here we detail the successful customization and use of the ThunderBolts Cancer Panel, which targets 230 commonly mutated regions in 50 cancer associated genes, with additional primers for commonly mutated genes in PDAC. Addition of the 37 PDAC-relevant primer pairs to the commercially available core panel was very straightforward and resulted in sequencing metrics similar to those of the core panel alone (100% coverage at 100x depth, mean read depth of 2500). Cyst fluid from 30 patients with IPMN resected under Sendai criteria were analyzed. We describe the mutational signature of cyst fluid and relate the presence and quantity of mutations in KRAS, GNAS and PIK3CA to the presence of invasive carcinoma and high grade dysplasia on pathology. Finally, unbiased and high resolution sequencing was obtained using this protocol with as little as 8ng of input DNA.

Using picodroplet PCR technology we were able to achieve unprecedented sequencing performance on ultra-low sample inputs. Given the ease of use and customization of the panel, the same platform may be readily adapted to other applications in which samples are limited or are difficult to amplify. Future studies will utilize this platform for an expanded analysis of pancreatic cyst fluid with additional primers.

Citation Format: Angelina I. Londoño-Joshi, Erica Pratt, Robert W. Cowan, Michael L. Samuels, Steve Kotsopoulos, Jeff Olson, Francis Long, Michelle A. Anderson, Diane Simeone, Andrew D. Rhim. Sensitive and robust targeted sequencing of pancreatic precancer and tumors using microfluidic single-molecule enrichment. [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 1572. doi:10.1158/1538-7445.AM2015-1572

Abstract A11: Ets transcription factor Etv5 regulates ductal morphogenesis and differentiation in association with Sox9 in vitro and increases susceptibility and delays recovery from pancreatitis in vivo

Introduction: The exocrine pancreas comprises a branched network of ducts that are connected to acini and lined by a monolayered epithelium that derives from the endoderm and is surrounded by mesenchyme. The formation and maturation of pancreatic ductal cells during branching morphogenesis is controlled by a complex hierarchy of transcription factors, which is not fully understood. The Ets-transcription factor Etv5 has been reported to play an important role during the development of organs that undergo branching morphogenesis such as mammary and salivary glands. We therefore aimed to characterize the functional role of Etv5 in pancreatic ductal development and differentiation.

Methods: Cells were isolated from wild-type mouse pancreata and lentiviral transduction was used to induce Etv5 overexpression. Cells were grown in 3D organotypic culture and analyzed with time lapsed microscopy for morphology and dynamics in the formation of duct-like cystic structures. Differentiation status of cells grown in 3D was analyzed by immunofluorescence-staining (IF) and qPCR. To asses the role of Etv5 in the normal mouse pancreas and its role in inflammation and regeneration in vivo, Pdx1cre;Etv5-/-; RosaYFP mice were generated and aged up to six months and subjected to a cerulein induced acute pancreatitis protocol.

Results: Normal pancreatic ductal cells grown in 3D-organotypic culture form spheroid cysts that resemble pancreatic ductal structures. Etv5 overexpression leads to early and exuberant formation of spheroid cysts within 2 days after seeding. Time-lapse microscopy demonstrated a significantly increased movement of cellular structures along the cyst as well as fusion of cysts into larger tubular structures. mRNA analysis of cysts harvested at day 7 displayed a strong upregulation of Sox9 and Foxa2, important regulators of ductal differentiation. Concurrently, E-cadherin was upregulated significantly whereas N-cadherin was downregulated indicating the terminal differentiation of these cells. IF-staining revealed co-localization of Etv5 and Sox9 in spheroid cysts of Etv5-overexpressing cells. Knockdown of Sox9 in Etv5-overexpressing cells with siRNA partially abrogated the formation of tubular structures and disrupted cyst architecture. Etv5 knockout mice (Pdx1Cre;Etv5-/-) were generated and we performed a cerulein-induced acute pancreatitis model. We found significantly elevated levels of serum amylase in Etv5-/- mice on Days 1 and 3 of the protocol. In a semiquantitative, blinded review of the histology, there was significantly more intense edema, inflammation, vacuolization and necrosis in Etv5-/- mice in all time points, which was also confirmed by quantitative amylase area scoring.

Conclusion: Our data suggest a novel role for Etv5 in pancreatic ductal morphogenesis and lumen formation that is at least in part mediated by Sox9. In addition, our data suggests that the loss of Etv5 expression increases susceptibility to pancreatitis and results in persistent pancreatitis with delayed regeneration.

Citation Format: Koushik K. Das, Steffen Heeg, Maximilian Reichert, Shigetsugu Takano, Basil S. Bakir, Gregory P. Botta, Christopher Hahn, Andrew D. Rhim, Anil K. Rustgi. Ets transcription factor Etv5 regulates ductal morphogenesis and differentiation in association with Sox9 in vitro and increases susceptibility and delays recovery from pancreatitis in vivo. [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 A11.

Abstract PR05: p120 catenin mediated epithelial-to-mesenchymal plasticity determines the metastatic potential of pancreatic ductal adenocarcinoma

Introduction: The majority of pancreatic ductal adenocarcinoma (PDAC) patients present with metastases and nearly all will succumb to disease within 6-12 months of clinical presentation (Hidalgo, 2010). Recently, p120catenin (p120) was identified as a “cancer candidate gene” in sleeping beauty-induced PDAC and p120 loss is associated with poor patient survival (Mann et al, 2012). P120 is critical in stabilizing E-cadherin (E-cad) at the adherens junctions. In this study, we wished to unravel new roles for p120 in the context of PDAC initiation and progression (epithelial-mesenchymal transition or EMT), as well as metastasis.

Results: We have introduced a floxed p120 allele into the Pdx1cre;LSL-KrasG12D;R26YFP (KCY) PDAC mouse model. Mice with homozygous p120 deletion in the context of a LSL-KrasG12D allele (KCYp120fl/fl) are not viable. However, mice with heterozygous p120 loss (KCYp120fl/wt) are born according to Mendelian ratios. At 20 weeks of age, KCYp120fl/wt mice show a remarkable acceleration of the Kras-driven phenotype. KCYp120fl/wt mice (n=21) harbor the entire spectrum of precursor lesions, including PanINs (1-3), mucinous cystic neoplasms (MCN) and intraductal papillary mucinous neoplasms (IPMN) and metastatic PDAC. The phenotype in control KCYp120wt/wt mice (n=12) was restricted to early PanINs. We next asked whether the second allele of p120 is lost during metastatic dissemination. We demonstrated that the remaining p120 allele is expressed in liver metastases, indicating that p120 loss-of-heterozygosity did not occur. Of note, in liver metastases, p120 co-localizes with E-cad, thereby indicating that a single p120 allele is sufficient to stabilize E-cad. This raised the question of whether one p120 allele is required to establish epithelial integrity at the metastatic site. In order to address this mechanistically, and since KCYp120fl/fl are not viable, we performed three-dimensional (3D) culture experiments with pancreatic cells isolated from non-recombined LSL-KrasG12D/+;p120wt/wt;R26YFP (KYp120wt/wt), KYp120fl/wt and KYp120fl/fl mice. Cells were Cre-recombined in vitro. In 3D culture, KYp120wt/wt cells form round multicellular cysts. Monoallelic p120 loss only disrupts the symmetry of cysts while biallelic loss completely prevents cells from forming organized, cyctic structures. We next injected these cell lines orthotopically into the pancreata of immunodeficient mice. KYp120wt/wt cells form PanIN-like structures. Interestingly, KYp120fl/wt establish large cysts reminiscent of IPMN/MCN lesions. In the cysts, p120 is localized at the plasma membrane with E-cad. However, the invasive fronts of tumors show significantly less p120 expression. Finally, KYp120fl/fl cells form poorly differentiated tumors invading into the surrounding stroma. Given the fact that p120 stabilizes E-cad and that E-cad is critical in EMT and MET, we injected the KYp120wt/wt, KYp120fl/wt and KYp120fl/fl cell lines directly into the portal veins of these mice. KYp120fl/wt cells colonize the liver and retain the remaining p120 allele and display membranous E-cad localization. By contrast, although KYp120fl/fl cells are able to generate invasive primary pancreatic tumors when being injected orthotopically, these cells fail to colonize the liver.

Conclusions: Our findings demonstrate that monoallelic loss of p120 accelerates Kras-driven PDAC formation. However, one allele of p120 is required to establish epithelial integrity and metastases. Taken together, these results for the first time underscore the importance of p120-mediated EMT plasticity in order to complete the metastatic cascade in vivo. Furthermore, therapeutic strategies to prevent EMT alone may not be sufficient in light of our results but rather require novel approaches to target EMT plasticity so as to enhance survival in metastatic PDAC.

This abstract is also presented as Poster A63.

Citation Format: Maximilian Reichert, Basil S. Bakir, Christopher M. Hahn, Gregory P. Botta, Andrew D. Rhim, Robert H. Vonderheide, Albert B. Reynolds, Yingtao Bi, Ramana Davuluri, Burcu Saka, N. Volkan Adsay, Anil K. Rustgi. p120 catenin mediated epithelial-to-mesenchymal plasticity determines the metastatic potential of pancreatic ductal adenocarcinoma. [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 PR05.

Abstract A46: The Ets-transcription factor Etv1 induces epithelial-mesenchymal transition (EMT) and invasion as well as expands the stromal compartment in vivo

Introduction: The Ets-transcription factor Etv1 is involved in epithelial-mesenchymal interactions during pancreatic development and shows enhanced expression in PanIN as well as in pancreatic ductal adenocarcinoma (PDAC). Therefore, we aimed to identify the mechanistic roles of Etv1 in EMT and invasion in PanIN and PDAC.

Methods: Cells were isolated from Pdx1Cre;KrasG12D/+-mice (PanIN) and Pdx1Cre;KrasG12D/+;p53R175H/+-mice (PDAC) and lentiviral tranduction was used to induce overexpression or knockdown (shRNA) of Etv1, respectively. Cells were grown in 3D organotypic culture to analyze morphology and growth behavior. Invasion and sphere formation (self-renewal) assays were performed. FACS-sorting was used to isolate CD44+/CD24+ cells as a putative cancer stem cell population in PDAC and analyzed for Etv1 expression. To assess the role of Etv1 in PDAC in vivo, orthotopic pancreatic xenograft transplantation of Etv1 overexpressing PDAC cells was performed.

Results: Etv1 overexpression in PanIN cells grown in 3D-organotypic culture induces a spindle shaped morphology and highly perturbed cyst architecture in contrast to control PanIN cells that form spheroid cysts that resemble normal pancreatic ductal structures. Concurrently and consistently, EMT-related genes (snail, twist, zeb1 and zeb2, as well as vimentin and N-cadherin) were found upregulated by &gt;2-fold in PanIN-mEtv1 cells. Moreover, the expression of Mmp3 and Mmp9 was significantly increased. Functionally, the invasive capacity of PanIN-mEtv1 cells was more than twice that of control cells; knockdown of Etv1 in PDAC-cells significantly abrogated their invasive capacity. In sphere forming assays PanIN-mEtv1 cells revealed an increased self-renewal capacity, whereas sphere formation is reduced by knockdown of Etv1 in PanIN as well as in PDAC cells. FACS-sorting and subsequent expression analysis revealed increased Etv1 levels in the putative cancer stem cell population of CD44+/CD24+ PDAC-cells. Data from orthotopic xenografts showed significantly larger tumors, significantly increased stromal expansion measured by trichrome staining, and increased local tumor invasion in Etv1-overexpressing cells compared to controls. The increased stromal expansion significantly correlated to the increased tumor volume observed in Etv1 over-expressing xenografts.

Conclusion: Our novel data indicate that Etv1 induces EMT as well as invasion both in vitro and in vivo and mediates self-renewal capacity of premalignant cells derived from PanIN- as well as PDAC-cells. Our in vivo data suggest a role for Etv1 in expanding the stromal compartment. These striking data suggest that Etv1 is biologically important in EMT. In vivo experiments with conditional knockout of Etv1 in Pdx1Cre;KrasG12D/+;p53R175H/+-mice are ongoing to further elucidate the role of Etv1 in PanIN and PDAC initiation and progression.

Citation Format: Koushik K. Das, Steffen Heeg, Maximilian Reichert, Shigetsugu Takano, Basil S. Bakir, Gregory P. Botta, Christopher Hahn, Andrew D. Rhim, Anil K. Rustgi. The Ets-transcription factor Etv1 induces epithelial-mesenchymal transition (EMT) and invasion as well as expands the stromal compartment in vivo. [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 A46.

Culturing mouse tumor cells

Genetically engineered mouse models (GEMMs) are attractive for the study of cancer; however, they can be time-consuming and expensive to produce and maintain. Thus, in certain contexts, the use of in vitro culture systems of tumor cells may provide an efficient and effective means to test hypotheses before assessment in or to complement discoveries in GEMMs. This introduction will briefly review the issues pertaining to in vitro analyses of primary cancer cells and highlight several "best practice" protocols that can be used when working with diverse types of carcinomas.

Culturing primary mouse pancreatic ductal cells

The most common subtype of pancreatic cancer is pancreatic ductal adenocarcinoma (PDAC). PDAC resembles ductal cells morphologically. To study pancreatic ductal cell (PDC) and pancreatic intraepithelial neoplasia (PanIN)/PDAC biology, it is essential to have reliable in vitro culture conditions. Here we describe a methodology to isolate, culture, and passage PDCs and duct-like cells from the mouse pancreas. It can be used to isolate cells from genetically engineered mouse models (GEMMs), providing a valuable tool to study disease models in vitro to complement in vivo findings. The culture conditions allow epithelial cells to outgrow fibroblast and other "contaminating" cell types within a few passages. However, the resulting cultures, although mostly epithelial, are not completely devoid of fibroblasts. Regardless, this protocol provides guidelines for a robust in vitro culture system to isolate, maintain, and expand primary pancreatic ductal epithelial cells. It can be applied to virtually all GEMMs of pancreatic disease and other diseases and cancers that arise from ductal structures. Because most carcinomas resemble ductal structures, this protocol has utility in the study of other cancers in addition to PDAC, such as breast and prostate cancers.

Creation of primary cell lines from lineage-labeled mouse models of cancer

Frequently, it is necessary to isolate pure populations of cancer cells for downstream assays, such as transcriptional analysis, signaling studies, and the creation of noncontaminated primary cell lines. Genetic lineage labeling with fluorescent reporter alleles allows for the identification of epithelial-derived cells within tumors. This protocol describes a method to isolate lineage-labeled pancreatic epithelial cells for ex vivo analysis, but it can be adapted for any type of lineage-labeled tumor.

Three-dimensional organotypic culture of stratified epithelia

One of the limitations of conventional tissue culture on flat two-dimensional surfaces is the loss of complex interactions between the epithelium and stroma. We have devised a culture system that recreates the salient features of the stratified epithelium using primary cell cultures from mouse models. The protocol described here is applicable to the esophageal epithelium, but stratified epithelial cells from other organs (e.g., skin) can be grown. Once established, the system can be used to interrogate the effect of various pharmacologic and genetic manipulations on epithelial homeostasis and invasion.

ATDC induces an invasive switch in KRAS-induced pancreatic tumorigenesis

The initiation of pancreatic ductal adenocarcinoma (PDA) is linked to activating mutations in KRAS. However, in PDA mouse models, expression of oncogenic mutant KRAS during development gives rise to tumors only after a prolonged latency or following induction of pancreatitis. Here we describe a novel mouse model expressing ataxia telangiectasia group D complementing gene (ATDC, also known as TRIM29 [tripartite motif 29]) that, in the presence of oncogenic KRAS, accelerates pancreatic intraepithelial neoplasia (PanIN) formation and the development of invasive and metastatic cancers. We found that ATDC up-regulates CD44 in mouse and human PanIN lesions via activation of β-catenin signaling, leading to the induction of an epithelial-to-mesenchymal transition (EMT) phenotype characterized by expression of Zeb1 and Snail1. We show that ATDC is up-regulated by oncogenic Kras in a subset of PanIN cells that are capable of invading the surrounding stroma. These results delineate a novel molecular pathway for EMT in pancreatic tumorigenesis, showing that ATDC is a proximal regulator of EMT.

Characterization of microfluidic shear-dependent epithelial cell adhesion molecule immunocapture and enrichment of pancreatic cancer cells from blood cells with dielectrophoresis

Current microfluidic techniques for isolating circulating tumor cells (CTCs) from cancer patient blood are limited by low capture purity, and dielectrophoresis (DEP) has the potential to complement existing immunocapture techniques to improve capture performance. We present a hybrid DEP and immunocapture Hele-Shaw flow cell to characterize DEP's effects on immunocapture of pancreatic cancer cells (Capan-1, PANC-1, and BxPC-3) and peripheral blood mononuclear cells (PBMCs) with an anti-EpCAM (epithelial cell adhesion molecule) antibody. By carefully specifying the applied electric field frequency, we demonstrate that pancreatic cancer cells are attracted to immunocapture surfaces by positive DEP whereas PBMCs are repelled by negative DEP. Using an exponential capture model to interpret our capture data, we show that immunocapture performance is dependent on the applied DEP force sign and magnitude, cell surface EpCAM expression level, and shear stress experienced by cells flowing in the capture device. Our work suggests that DEP can not only repel contaminating blood cells but also enhance capture of cancer cell populations that are less likely to be captured by traditional immunocapture methods. This combination of DEP and immunocapture techniques to potentially increase CTC capture purity can facilitate subsequent biological analyses of captured CTCs and research on cancer metastasis and drug therapies.

Stromal elements act to restrain, rather than support, pancreatic ductal adenocarcinoma

Sonic hedgehog (Shh), a soluble ligand overexpressed by neoplastic cells in pancreatic ductal adenocarcinoma (PDAC), drives formation of a fibroblast-rich desmoplastic stroma. To better understand its role in malignant progression, we deleted Shh in a well-defined mouse model of PDAC. As predicted, Shh-deficient tumors had reduced stromal content. Surprisingly, such tumors were more aggressive and exhibited undifferentiated histology, increased vascularity, and heightened proliferation--features that were fully recapitulated in control mice treated with a Smoothened inhibitor. Furthermore, administration of VEGFR blocking antibody selectively improved survival of Shh-deficient tumors, indicating that Hedgehog-driven stroma suppresses tumor growth in part by restraining tumor angiogenesis. Together, these data demonstrate that some components of the tumor stroma can act to restrain tumor growth.

Microfluidic immunocapture of circulating pancreatic cells using parallel EpCAM and MUC1 capture: characterization, optimization and downstream analysis

We have developed and optimized a microfluidic device platform for the capture and analysis of circulating pancreatic cells (CPCs) and pancreatic circulating tumor cells (CTCs). Our platform uses parallel anti-EpCAM and cancer-specific mucin 1 (MUC1) immunocapture in a silicon microdevice. Using a combination of anti-EpCAM and anti-MUC1 capture in a single device, we are able to achieve efficient capture while extending immunocapture beyond single marker recognition. We also have detected a known oncogenic KRAS mutation in cells spiked in whole blood using immunocapture, RNA extraction, RT-PCR and Sanger sequencing. To allow for downstream single-cell genetic analysis, intact nuclei were released from captured cells by using targeted membrane lysis. We have developed a staining protocol for clinical samples, including standard CTC markers; DAPI, cytokeratin (CK) and CD45, and a novel marker of carcinogenesis in CPCs, mucin 4 (MUC4). We have also demonstrated a semi-automated approach to image analysis and CPC identification, suitable for clinical hypothesis generation. Initial results from immunocapture of a clinical pancreatic cancer patient sample show that parallel capture may capture more of the heterogeneity of the CPC population. With this platform, we aim to develop a diagnostic biomarker for early pancreatic carcinogenesis and patient risk stratification.

Detection of circulating pancreas epithelial cells in patients with pancreatic cystic lesions

Hematogenous dissemination is thought to be a late event in cancer progression. We recently showed in a genetic model of pancreatic ductal adenocarcinoma that pancreas cells can be detected in the bloodstream before tumor formation. To confirm these findings in humans, we used microfluidic geometrically enhanced differential immunocapture to detect circulating pancreas epithelial cells in patient blood samples. We captured more than 3 circulating pancreas epithelial cells/mL in 7 of 21 (33%) patients with cystic lesions and no clinical diagnosis of cancer (Sendai criteria negative), 8 of 11 (73%) with pancreatic ductal adenocarcinoma, and in 0 of 19 patients without cysts or cancer (controls). These findings indicate that cancer cells are present in the circulation of patients before tumors are detected, which might be used in risk assessment.

The effects of long-term therapy with proton pump inhibitors on meal stimulated gastrin

BACKGROUND

Dyspepsia develops in healthy volunteers after withdrawal of proton-pump inhibitors. This phenomenon, attributed to rebound acid hypersecretion, is thought to be mediated by reflex hypergastrinemia.

AIMS

To measure fasting and postprandial gastrin in patients on long-term proton-pump inhibitor treatment and correlate gastrin levels with the duration of treatment and other potential predictors.

METHODS

In this cross sectional study patients, with erosive esophagitis, on long-term proton-pump inhibitor treatment and healthy controls underwent gastrin measurements at baseline and four times following a meal and Helicobacter pylori status was determined.

RESULTS

A total of 100 patients and 50 controls were studied. Pre- and postprandial gastrin levels were higher in patients (p<0.001). No significant correlation was found between the area under the gastrin-curve and the treatment duration. Female patients had significantly higher gastrin levels than males pre- and postprandial, whereas such differences was not found in the control group. Female gender was the only independent predictor of s-gastrin levels (OR 2.50 compared to males, 95% CI: 1.08-5.76, p=0.032) in the patient group.

CONCLUSION

Gastrin values were higher in patients compared to controls. There was no correlation between gastrin levels and treatment duration. Female patients had significantly higher gastrin values than males.