A ketogenic diet in combination with gemcitabine increases survival in pancreatic cancer KPC mice

Pancreatic ductal adenocarcinoma (PDAC) continues to be a major health problem. A ketogenic diet (KD), characterized by a very low carbohydrate and high fat composition, has gained attention for its anti-tumor potential. We evaluated the effect and mechanisms of feeding a strict KD alone or in combination with gemcitabine in the autochthonous LSL-Kras^G12D/+; LSL-Trp53 ^R172H/+; Pdx1-Cre (KPC) mouse model. For this purpose, both male and female pancreatic tumor-bearing KPC mice were allocated to a control diet (CD; %kcal: 70% carb, 14% protein, 16% fat), a KD (%kcal: 14% protein, 1% carb, 85% fat), a CD + gemcitabine (CG), or a KD + gemcitabine (KG) group. Mice fed a KD alone or in combination with gemcitabine showed significantly increased blood β-hydroxybutyrate levels compared to mice fed a CD or CG. KPC mice fed a KG had a significant increase in overall median survival compared to KPC mice fed a CD (increased overall median survival by 42%). Interestingly, when the data was disaggregated by sex, the effect of a KG was significant in female KPC mice (60% increase in median overall survival), but not in male KPC mice (28% increase in median overall survival). Mechanistically, the enhanced survival response to a KD combined with gemcitabine was multifactorial, including inhibition of ERK and AKT pathways, regulation of fatty acid metabolism and the modulation of the gut microbiota. In summary, a KD in combination with gemcitabine appears beneficial as a treatment strategy in PDAC in KPC mice, deserving further clinical evaluation.

Germline Aberrations in Pancreatic Cancer: Implications for Clinical Care

Pancreatic ductal adenocarcinoma (PDAC) has an extremely poor prognosis and represents a major public health issue, as both its incidence and mortality are expecting to increase steeply over the next years. Effective screening strategies are lacking, and most patients are diagnosed with unresectable disease precluding the only chance of cure. Therapeutic options for advanced disease are limited, and the treatment paradigm is still based on chemotherapy, with a few rare exceptions to targeted therapies. Germline variants in cancer susceptibility genes-particularly those involved in mechanisms of DNA repair-are emerging as promising targets for PDAC treatment and prevention. Hereditary PDAC is part of the spectrum of several syndromic disorders, and germline testing of PDAC patients has relevant implications for broad cancer prevention. Germline aberrations in BRCA1 and BRCA2 genes are predictive biomarkers of response to poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitor olaparib and platinum-based chemotherapy in PDAC, while mutations in mismatch repair genes identify patients suitable for immune checkpoint inhibitors. This review provides a timely and comprehensive overview of germline aberrations in PDAC and their implications for clinical care. It also discusses the need for optimal approaches to better select patients for PARP inhibitor therapy, novel therapeutic opportunities under clinical investigation, and preclinical models for cancer susceptibility and drug discovery.

SEMA3C Supports Pancreatic Cancer Progression by Regulating the Autophagy Process and Tumor Immune Microenvironment

To date, driver genes for pancreatic cancer treatment are difficult to pursue therapeutically. Targeting mutated KRAS, the most renowned driver gene in pancreatic cancer, is an active area of study. We discovered a gene named SEMA3C was highly expressed in pancreatic cancer cell lines and patients with a G12D mutation in KRAS. High expression of SEMA3C in patients was significantly associated with the decreased survival of pancreatic cancer patients based on the TCGA database. In pancreatic cancer cells, SEMA3C knockdown or inhibition exhibited growth/colony inhibition and cell cycle arrest. In addition, SEMA3C inhibition sensitized KRAS or MEK1/2 inhibition in pancreatic cancer cells. Overexpression of SEMA3C resulted in the induction of autophagy, whereas depletion of SEMA3C compromised induction of autophagy. SEMA3C modified the PD-L1 expression in tumor and immune cells and is correlated with the M2-like macrophage marker ARG1/CD163 expression, which could reshape the tumor microenvironment. Inhibition of SEMA3C decreased tumor formation in the xenograft model in vivo. Taken together, our data suggest that SEMA3C plays a substantial role in promoting cancer cell survival by regulating the autophagy process and impacting the tumor environment immune response. SEMA3C can be used as a novel target or marker with therapeutic or diagnostic potential in pancreatic cancer especially in tumors harboring the specific KRAS G12D mutation.

SOAT1 promotes mevalonate pathway dependency in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis, and new therapies are needed. Altered metabolism is a cancer vulnerability, and several metabolic pathways have been shown to promote PDAC. However, the changes in cholesterol metabolism and their role during PDAC progression remain largely unknown. Here we used organoid and mouse models to determine the drivers of altered cholesterol metabolism in PDAC and the consequences of its disruption on tumor progression. We identified sterol O-acyltransferase 1 (SOAT1) as a key player in sustaining the mevalonate pathway by converting cholesterol to inert cholesterol esters, thereby preventing the negative feedback elicited by unesterified cholesterol. Genetic targeting of Soat1 impairs cell proliferation in vitro and tumor progression in vivo and reveals a mevalonate pathway dependency in p53 mutant PDAC cells that have undergone p53 loss of heterozygosity (LOH). In contrast, pancreatic organoids lacking p53 mutation and p53 LOH are insensitive to SOAT1 loss, indicating a potential therapeutic window for inhibiting SOAT1 in PDAC.

Abstract B25: Engrailed-1 promotes pancreatic cancer progression via antagonizing COMPASS activity

Pancreatic ductal adenocarcinoma (PDA) is the most deadly disease in human malignancies. Using pancreatic organoid models, we have shown that enhancer reprogramming allows pancreatic cancer cells to acquire aggressive characteristics during disease progression. Recently we found that organoid cultures (mM) derived from metastatic lesions of KPC mice (Kras+/LSL-G12D; Trp53+/LSL-R172H; Pdx1-Cre) can survive in the reduced condition, unlike the paired primary tumor-derived organoid cultures (mT). We implicate Engrailed-1 (EN1), a neurodevelopmental transcription factor (TF), in this process as a prosurvival factor. We show that EN1 is indispensable for organoid survival in the reduced condition, highly expressed in mM compared to mT organoid cultures, and associated with poor prognosis. Gain- and loss-of-function experiments further show that EN1 is responsible for the aggressiveness of pancreatic cancer cells in vitro (anchorage-independent growth, migration, and invasion) and in vivo. On the other hand, subcutaneous tumors derived from EN1 expressing mT organoids exhibit squamous-like differentiation compared to control. In line with this, squamous-type PDA patients tend to express EN1 compared to other subtypes of PDA. Furthermore, EN1 perturbation renders the changes of squamous-PDA identity and KDM6A deficiency signatures. Mechanistically, EN1 can physically interact with KDM6A and repress H3K4me3 occupancy in a subset of genes without affecting H3K27me3 and H3K27ac occupancies, suggesting that the regulation of COMPASS (Complex Proteins Associated with Set1) activity by EN1 might be critical in this process. Finally, by combining EN1 with FOXA1, previously shown to be responsible for enhancer activation in PDA organoids, we were able to fully reprogram pancreatic cancer cells into highly aggressive pancreatic cancer cells. In sum, we report that EN1 confers the aggressiveness of pancreatic cancer cells via regulation of COMPASS activity and contributes to squamous-type identity and PDA progression.

Citation Format: Chang-il Hwang, Jae-Seok Roe, Eun Jung Lee, Claudia Tonelli, Tim D.D. Somervile, Melissa Yao, Joseph P. Milazzo, Hervé Tiriac, Youngkyu Park, Christopher Vakoc, David Tuveson. Engrailed-1 promotes pancreatic cancer progression via antagonizing COMPASS activity [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 B25.

Abstract B64: Using pancreatic organoids to infer therapeutic resistance and sensitivity

Pancreatic ductal adenocarcinoma (PDA) is a lethal disease with a 5-year survival rate less than 6%. The late diagnosis of the disease and poor efficacy of systemic treatments are major factors for this poor prognosis, and highlight the need for novel PDA models better able to predict resistance/sensitivity to treatment. To fulfill this need, our laboratory developed a three-dimensional culture system that enables the rapid growth of both mouse and human pancreatic ductal organoids. Organoids can be established from healthy or neoplastic tissues using both large (surgical material) and small (fine needle biopsy) samples, thereby providing a novel platform for therapeutic testing for all stages of disease. In this study, we use organoids to evaluate the therapeutic efficacy of the simultaneous inhibition of MEK and AKT kinases, which are activated in PDA by KRAS mutations. Tumor-derived organoids were resistant to both single agents and combination treatment. Genetically engineered mouse models of pancreatic cancer (KPC) also only exhibited a brief response to dual inhibition of MEK and AKT. To assess the potential mechanism of resistance, we evaluated the activation of a number of receptor tyrosine kinases by interrogating both mouse and organoid treated tissues. Members of the ERBB family were activated in KPC animals and tumor-derived organoids treated with both MEK and AKT inhibitors. Accordingly, the addition of an irreversible pan-ERBB inhibitor to the combination of MEK and AKT inhibitors, or MEK inhibitor alone, prevented ERBB-mediated resistance and improved tumor sensitivity to therapeutic intervention. This new therapeutic strategy is efficacious both ex-vivo and in vivo using human tumor-derived organoids and their associated transplant model. Finally, we show that human PDA organoids can be used in high throughput therapeutic screening for the identification of patient-specific therapeutic sensitivities. In summary, pancreatic organoids represent a system that can be used to predict drug sensitivity as well as to identify mechanism of resistance.

*Equal contribution

Citation Format: Herve Tiriac*, Mariano Ponz-Sarvise*, Vincenzo Corbo*, Kristopher K. Frese*, Dannielle D. Engle*, Daniel Ohlund, Tobiloba Oni, Chang-il Hwang, Abram Handly-Santana, Brinda Alagesan, Dea Filippini, Kevin Wright, Kenneth H. Yu, Youngkyu Park, David A. Tuveson.{Authors}. Using pancreatic organoids to infer therapeutic resistance and sensitivity. [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 B64.

Abstract A04: Identification of novel pancreatic cancer-specific biomarkers with organoid models

Pancreatic ductal adenocarcinoma (PDA) is almost uniformly lethal and surgical intervention is the only cure. Unfortunately, the majority of patients are ineligible for resection because of the advanced stage of disease by the time of diagnosis. This is due in part to that lack of diagnostic tools, especially for families with elevated risk. Although considered an intractable and aggressive malignancy, progression from the initiating events to overt cancer requires approximately 12 years, and advancement to metastatic disease takes another 5 – 7 years. This latency indicates that there is a window for early detection and intervention. The PDA biomarker, CA19-9, is measured in the blood to follow tumor burden longitudinally, but is neither sensitive nor specific enough to be used for diagnosis. In particular, the use of CA19-9 in PDA diagnosis is problematic given the elevation of CA19-9 in benign conditions, such as pancreatitis, that have a higher incidence than PDA. To improve the diagnostic performance of CA19-9, we identified tissue- and cancer-specific protein carriers of the CA19-9 carbohydrate modification using murine and human organoid model systems of pancreatic cancer disease progression. To induce CA19-9 expression in murine organoids, two human gylcosyl transferases that were deficient in mice were ectopically expressed. CA19-9 protein carriers specific to malignancy were identified relative to normal, proliferating ductal cells. Some CA19-9 carriers that were shared between normal and malignant pancreatic ductal organoids were also detected in the sera of patients with benign pancreatic disease, highlighting their inability to distinguish malignancy from pancreatitis. Importantly, several of the tumor-specific novel CA19-9 carriers identified in organoids also discriminated between benign and malignant disease in human patient sera, and are nominated for clinical validation. Overall, organoid model systems allow identification of biomarkers that discriminate between normal proliferation and malignant conditions of multiple gastrointestinal tissues, providing a robust platform for biomarker discovery.

Citation Format: Dannielle Engle, Herve Tiriac, Rivera Keith, Michael Ludwig, Chang-il Hwang, Kenneth Yu, Darryl Pappin, David Tuveson.{Authors}. Identification of novel pancreatic cancer-specific biomarkers with organoid models. [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 A04.

Abstract B16: Using human patient-derived organoids to identify genetic dependencies in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal malignancies due to its late diagnosis and limited response to treatment. Tractable model systems to interrogate pathways involved in pancreatic tumorigenesis and to probe individual responses to novel therapies are urgently needed. To that end, we established methods to culture normal and neoplastic pancreatic duct cells as three-dimensional organoid cultures. Pancreatic organoids can be rapidly generated from resected tumors or fine needle biopsies, survive cryopreservation, and exhibit ductal- and disease-stage-specific characteristics. Following orthotopic transplant, neoplastic organoids recapitulated the full spectrum of tumor development by forming early-grade neoplasms that progressed to locally invasive and metastatic carcinomas, demonstrating the utility of organoids to model the stages of PDA tumorigenesis. Monolayer cell lines were generated from organoid cultures with high efficiency, creating a diverse collection of new PDA cell lines. To better understand pathways involved in PDA progression, we performed transcriptomic and proteomic analyses of murine organoids derived from normal pancreatic ducts, pancreatic intraepithelial neoplasias (PanINs), and PDAs. These datasets revealed expression changes associated with early and late pancreatic tumorigenesis. To identify genes dysregulated during pancreatic tumorigenesis whose depletion impaired human PDA cells, a CRISPR-Cas competition assay was employed. Taken together, pancreatic organoids offer a novel model system for studying pancreatic cancer biology and can be used to screen for genetic dependencies in PDA.

Citation Format: Lindsey A. Baker, Hervé Tiriac, Vincenzo Corbo, Sylvia F. Boj, Chang-il Hwang, Iok In Christine Chio, Danielle D. Engle, Myrthe Jager, Mariano Ponz-Sarvise, Mona S. Spector, Ana Gracanin, Tobiloba Oni, Kenneth H. Yu, Ruben van Boxtel, Meritxell Huch, Keith D. Rivera, John P. Wilson, Michael E. Feigin, Daniel Öhlund, Abram Handly-Santana, Christine M. Ardito-Abraham, Michael Ludwig, Ela Elyada, Brinda Alagesan, Giulia Biffi, Georgi N. Yordanov, Bethany Delcuze, Brianna Creighton, Kevin Wright, Youngkyu Park, Folkert H.M. Morsink, I. Quintus Molenaar, Inne H. Borel Rinkes, Edwin Cuppen, Yuan Hao, Ying Jin, Isaac J. Nijman, Christine Iacobuzio-Donahue, Steven D. Leach, Darryl J. Pappin, Molly Hammell, David S. Klimstra, Olca Basturk, Ralph H. Hruban, George Johan Offerhaus, Robert G.J. Vries, Hans Clevers, David A. Tuveson. Using human patient-derived organoids to identify genetic dependencies in pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr B16.

Abstract 4183: Modeling soft tissue sarcomas by conditional inactivation of p53 and Rb tumor suppressor genes

Soft tissue sarcomas, particularly its most common type, undifferentiated pleomorphic sarcomas (also known as malignant fibrous histiocytomas), frequently carry mutations in p53 and Rb tumor suppressor genes. We have established the sarcoma mouse model using conditional inactivation of p53 and Rb by a single subcutaneous injection of adenovirus carrying Cre-recombinase into transgenic mice with floxed copies of p53 and Rb genes. The majority of sarcomas in this model are malignant fibrous histiocytomas, which is a neoplasm consisting of intermixed fibroblast- and histiocyte-like cells. By using irradiation chimeras that have been generated by transplanting bone marrow cells from mice carrying the Rosa26StopLacZ or the Z/EG reporter, as well as floxed p53 and Rb genes, to irradiated p53loxP/loxPRbloxP/loxP mice, we have determined that sarcomas in this model do not originate from hematopoietic cells but arise from the local resident cells. Although the majority of dermal cells infected with AdCMVCre-eGFP have shown expression of fibroblast marker procollagen type I or macrophage marker F4/80, we have observed that cells expressing stem cell markers Sca-1 and nestin also have been targeted by adenovirus. Notably, isolated mesenchymal multipotent cells characterized by strict plastic adherence and low levels of Sca-1 expression have shown enhanced potential for malignant transformation according to proliferation, invasion, and soft agar assays, following conditional inactivation of p53 and Rb. Additionally, we have determined that sarcomas have increased expression of CXCR4, while its ligand SDF-1 is expressed by infiltrating macrophages. Treatment of sarcoma cells with SDF-1 leads to their increased invasion in Boyden chamber assay while CXCR4 knockdown with siRNA abrogates this effect. Taken together, our results indicate that local Sca-1low multipotent dermal stem/progenitor cells may be a preferential target for malignant transformation associated with p53 and Rb deficiency. Furthermore, accumulation of SDF-1 producing macrophages may stimulate sarcomagenesis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4183.

Gene profile of replicative senescence is different from progeria or elderly donor

In vitro cellular senescence of human diploid fibroblast has been a good model for aging research, which shows similar phenotypes to in vivo aging. Gene expression profiling would provide an insight to understand the mechanism of senescence. Using cDNA microarray containing 384 known genes, we compared the expression profiles of three different types of aging models: replicative senescence, fibroblasts from progeria or from elderly donor. Although all of them showed senescence phenotypes, distinct sets of genes were altered in each group. Pairwise plots or cluster analysis of activation fold of gene expression revealed closer relationships between fibroblasts from progeria or from old individual, but not between replicative senescence fibroblasts and either models. Differential expression pattern of several genes were confirmed by RT-PCR. We suggest that the replicative senescence model might behave differently to other types of aging models due to the distinct gene expression.

Structure-reactivity probes for active site shapes of cholesterol esterase by carbamate inhibitors

4,4'-Biphenyl-di-N-butylcarbamate (1), (S)-1,1'-bi-2-naphthyl-2, 2'-di-N-butylcarbamate (S-2), (S)-1, 1'-bi-2-naphthyl-2-N-butylcarbamate-2'-butyrate (S-3), 2, 2'-biphenyl-di-N-butylcarbamate (4), 2, 2'-biphenyl-2-N-octadecylcarbamate-2'-N-octylcarbamate (5), 2, 2'-biphenyl-2-N-octadecylcarbamate-2'-N-phenylcarbamate (6), 2, 2'-biphenyl-2-N-butylcarbamate-2'-butyrate (7), 2, 2'-biphenyl-2-N-butylcarbamate-2'-ol (8), 2, 2'-biphenyl-2-N-octylcarbamate-2'-ol (9), (R)-1, 1'-bi-2-N-naphthyl-2-butylcarbamate-2'-ol (R-10), and glyceryl-1,2, 3-tri-N-butylcarbamate (11) are prepared and evaluated for their inhibition effects on porcine pancreatic cholesterol esterase. All inhibitors are irreversible inhibitors of the enzyme. Carbamates 1-3 and 7-10 are the first alkyl chain and esteratic binding site-directed irreversible inhibitors due to the fact that the reactivity of the enzyme is protected by the irreversible inhibitor, trifluoroacetophenone in the presence of these carbamates. Carbamate 1 is the least potent inhibitor for the enzyme probably due to the fact that the inhibitor molecule adopts a linear conformation and one of the carbamyl groups of the inhibitor molecule covalently interacts with the first alkyl chain binding site of the enzyme while the other carbamyl group of the inhibitor molecule exposes outside the active site. With near orthogonal conformations at the pivot bond of biaryl groups, one carbamyl group of carbamates S-2, S-3, and R-10 covalently binds to the first alkyl chain binding site of the enzyme while the other carbamyl, butyryl, or hydroxy group can not bind covalently to the second alkyl chain binding site probably due to the orthogonal conformations. Carbamates 4-9 and 11 are very potent inhibitors for the enzyme probably due to the fact that all these molecules freely rotate at the pivot bond of the biphenyl or glyceryl group and therefore can fit well into the bent-shaped first and second alkyl chains binding sites of the enzyme. Although, carbamates 4-6 and 11 are irreversible inhibitors of cholesterol esterase, the enzyme is not protected but further inhibited by trifluoroacetophenone in the presence of these carbamates. Therefore, carbamates 4-6 and 11 covalently bind to the first alkyl chain binding site of the enzyme by one of the carbamyl groups and may also bind to the second alkyl chain binding site of the enzyme by the second carbamyl group. Besides the bent-shaped conformation, the inhibition by carbamate 6 is probably assisted by a favorable pi-pi interaction between Phe 324 at the second alkyl chain binding site of the enzyme and the phenyl group of the inhibitor molecule. For cholesterol esterase, carbamates 8-10 are more potent than carbamates S-2, 4, and 5 probably due to the fact that the inhibitor molecules interact with the second alkyl chain binding site of the enzyme through a hydrogen bond between the phenol hydroxy group of the inhibitor molecules and the His 435 residue in that site.