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Lumican is secreted by pancreatic stellate cells and inhibits cancer progression. Extracellular lumican inhibits cancer cell replication and restrains growth of early-stage pancreatic adenocarcinoma (PDAC) such that patients with tumors containing stromal lumican experience a three-fold longer survival after treatment. In the present study, patient tumor tissues, ex-vivo cultures of patient-derived xenografts (PDX), PDAC stellate and tumor cells were used to investigate whether hypoxia (1% O2) within the tumor microenvironment influences stromal lumican expression and secretion. We observed that hypoxia significantly reduced lumican expression and secretion from pancreatic stellate cells, but not cancer cells. Although hypoxia enhanced lactate dehydrogenase A (LDHA) expression and lactate secretion from all cells, neither hypoxia-induced nor exogenous lactate influenced lumican expression. Autophagy was induced by hypoxia in ex vivo cultures of PDX and pancreatic stellate cells, but not cancer cells cultured in 2D. Autophagic flux inhibitors, bafilomycin A1, chloroquine diphosphate salt, and ammonium chloride prevented hypoxia-mediated reduction in lumican expression in stellate cells. Furthermore, inhibition of AMP-regulated protein kinase (AMPK) phosphorylation or hypoxia-inducible factor (HIF)-1α expression within hypoxic stellate cells restored lumican expression levels. Hypoxia did not affect lumican mRNA expression, indicating that hypoxia-induced reduction of lumican occurs post-transcriptionally; in addition, AMPK inhibition prevented hypoxia-reduced phosphorylation of the mTOR/p70S6K/4EBP signaling pathway, a key contributor to protein synthesis. Taken together, these findings demonstrate that hypoxia reduces stromal lumican in PDAC through autophagy-mediated degradation and reduction in protein synthesis within pancreatic cancer stellate cells.

Depletion of malic enzyme 3 in pancreatic cancer cells that have a deletion of the gene for malic enzyme 2 selectively kills the cells, suggesting that the enzyme might represent a therapeutic target for this subset of cancers. Gene deletion in pancreatic cancer In pancreatic cancer, a commonly deleted genomic region includes the gene that encodes metabolic malic enzyme 2, ME2. The authors show that pancreatic tumour cells depend on the activity of the other malic enzyme isoform, ME3, for survival. This finding reveals a metabolic collateral vulnerability that may be further explored to develop therapeutic strategies. The genome of pancreatic ductal adenocarcinoma (PDAC) frequently contains deletions of tumour suppressor gene loci, most notably SMAD4 , which is homozygously deleted in nearly one-third of cases 1 . As loss of neighbouring housekeeping genes can confer collateral lethality, we sought to determine whether loss of the metabolic gene malic enzyme 2 ( ME2 ) in the SMAD4 locus would create cancer-specific metabolic vulnerability upon targeting of its paralogous isoform ME3 . The mitochondrial malic enzymes (ME2 and ME3) are oxidative decarboxylases that catalyse the conversion of malate to pyruvate and are essential for NADPH regeneration and reactive oxygen species homeostasis 2 , 3 . Here we show that ME3 depletion selectively kills ME2 -null PDAC cells in a manner consistent with an essential function for ME3 in ME2 -null cancer cells. Mechanistically, integrated metabolomic and molecular investigation of cells deficient in mitochondrial malic enzymes revealed diminished NADPH production and consequent high levels of reactive oxygen species. These changes activate AMP activated protein kinase (AMPK), which in turn directly suppresses sterol regulatory element-binding protein 1 (SREBP1)-directed transcription of its direct targets including the BCAT2 branched-chain amino acid transaminase 2) gene. BCAT2 catalyses the transfer of the amino group from branched-chain amino acids to α-ketoglutarate (α-KG) 4 thereby regenerating glutamate, which functions in part to support de novo nucleotide synthesis. Thus, mitochondrial malic enzyme deficiency, which results in impaired NADPH production, provides a prime ‘collateral lethality’ therapeutic strategy for the treatment of a substantial fraction of patients diagnosed with this intractable disease.

Pancreatic ductal adenocarcinoma (PDAC) tumors are characterized by a desmoplastic reaction resulting in dense deposition of collagen that is known to promote cancer progression. A central mediator of protumorigenic collagen signaling is the receptor tyrosine kinase discoid domain receptor 1 (DDR1). DDR1 is a critical driver of a mesenchymal and invasive cancer cell PDAC phenotype. Previous studies have demonstrated that genetic or pharmacologic inhibition of DDR1 reduces PDAC tumorigenesis and metastasis. Here, we investigated whether DDR1 signaling has cancer cell nonautonomous effects that promote PDAC progression and metastasis. We demonstrate that collagen-induced DDR1 activation in cancer cells is a major stimulus for CXCL5 production, resulting in the recruitment of tumor-associated neutrophils (TANs), the formation of neutrophil extracellular traps (NETs), and subsequent cancer cell invasion and metastasis. Moreover, we have identified that collagen-induced CXCL5 production was mediated by a DDR1/PKC θ /SYK/NF- κ B signaling cascade. Together, these results highlight the critical contribution of the collagen I–DDR1 interaction in the formation of an immune microenvironment that promotes PDAC metastasis.

HNF1A (Hepatocyte nuclear factor 1 alpha) is a transcription factor that is known to regulate pancreatic differentiation and maintain homeostasis of endocrine pancreas. Recently, genome-wide association studies have implicated HNF1A as a susceptibility gene for pancreatic cancer. However, the functional significance and molecular mechanism of HNF1A in pancreatic carcinogenesis remains unclear. Using RT-PCR, Western blot and immunohistochemistry methods, we examined HNF1A gene expression in eight pancreatic carcinoma cell lines and in paired tumor and normal tissue samples from patients with resected pancreatic ductal adenocarcinoma. We knocked down the HNF1A gene expression in two cancer cell lines using three siRNA sequences. The impacts on cell proliferation, apoptosis, and cell cycle as well as the phosphorylation of Akt signaling transduction proteins were examined using ATP assay, flow cytometry and Western blot. HNF1A was expressed in three out of eight pancreatic adenocarcinoma cell lines and the level of HNF1A mRNA and protein expression was significantly lower in tumors than in normal adjacent tissues by both RT-PCR and Western Blot analyses. Immunohistochemistry revealed that the level of HNF1A expression was significantly lower in tumor tissues than in non-tumor tissues. Selective blocking of HNF1A by specific siRNA conferred a 2-fold higher rate of cell proliferation, 20% increased S phase and G2 phase cells, and 30-40% reduced apoptosis in pancreatic cancer cell lines. We further demonstrated that HNF1A knockdown activated Akt and its downstream target, the mammalian target of rapamycin (mTOR) in pancreatic cancer cells. These observations provide experimental evidence supporting a possible tumor suppressor role of HNF1A in pancreatic cancer.

Tumor metastasis are accompanied by the EMT (epithelial-mesenchymal transition)-MET (mesenchymal-epithelial transition) two-step process. In this study, we investigated the importance of cancer associated fibroblasts (CAF) in the process. First, the primary cultures of isolated pancreatic CAF, fibroblasts of normal pancreatic tissues (NF), and normal hepatic stellate cells (HSF) were identified and verified via the expression of α-SMA and vimentin. Using an indirect three-dimensional co-culture model, the morphological changes were observed by light microscopy and laser scanning confocal microscopy. The invasive and migration capacity of pancreatic cancer cells was determined by Transwell chamber migration assay or scratch assay. The mRNA and protein expression levels of E-cadherin, vimentin, and Gli1 were determined by RT-PCR and western blotting. Primary cultures of isolated CAF, NF, HSF showed satisfactory growth with active proliferation. Indirect co-culture with CAF, BxPc-3 and Panc-1 cells showed significant partial EMT, reduced E-cadherin expression, and enhanced vimentin expression as compared with the single culture and NF/HSF co-culture groups, with corresponding increases in migratory and invasive capacities. PCR and western blotting results showed that mRNA and protein expression levels of Gli1 in CAF and Snail in cancer cells were increased. This process could be reversed by inhibition of hedgehog (HH) signaling in CAF. In the tumor microenvironment, activation of CAF is the key event in mediating partial EMT, and its mechanism may be associated with paracrine action after activation of HH signaling in CAF.

Pancreatic cancers use a novel glutamine metabolism pathway, regulated by oncogenic KRAS, to maintain redox balance; these findings add to the understanding of the mechanisms by which oncogenic alterations reprogram cellular metabolism to promote tumour growth. Novel glutamine pathway in pancreatic cancer Pancreatic tumours often carry activating KRAS mutations. This study describes a novel KRAS-regulated pathway that is critical to the metabolism of glutamine by human pancreatic cancer cells and is required for tumour growth. The pathway appears to maintain redox homeostasis but is dispensable in normal cells, providing a possible avenue for pursuing antitumour compounds that might act in pancreatic ductal adenocarcinoma, an extremely aggressive cancer that is highly refractory to chemotherapy, radiation and targeted therapies. Cancer cells have metabolic dependencies that distinguish them from their normal counterparts 1 . Among these dependencies is an increased use of the amino acid glutamine to fuel anabolic processes 2 . Indeed, the spectrum of glutamine-dependent tumours and the mechanisms whereby glutamine supports cancer metabolism remain areas of active investigation. Here we report the identification of a non-canonical pathway of glutamine use in human pancreatic ductal adenocarcinoma (PDAC) cells that is required for tumour growth. Whereas most cells use glutamate dehydrogenase (GLUD1) to convert glutamine-derived glutamate into α-ketoglutarate in the mitochondria to fuel the tricarboxylic acid cycle, PDAC relies on a distinct pathway in which glutamine-derived aspartate is transported into the cytoplasm where it can be converted into oxaloacetate by aspartate transaminase (GOT1). Subsequently, this oxaloacetate is converted into malate and then pyruvate, ostensibly increasing the NADPH/NADP + ratio which can potentially maintain the cellular redox state. Importantly, PDAC cells are strongly dependent on this series of reactions, as glutamine deprivation or genetic inhibition of any enzyme in this pathway leads to an increase in reactive oxygen species and a reduction in reduced glutathione. Moreover, knockdown of any component enzyme in this series of reactions also results in a pronounced suppression of PDAC growth in vitro and in vivo . Furthermore, we establish that the reprogramming of glutamine metabolism is mediated by oncogenic KRAS, the signature genetic alteration in PDAC, through the transcriptional upregulation and repression of key metabolic enzymes in this pathway. The essentiality of this pathway in PDAC and the fact that it is dispensable in normal cells may provide novel therapeutic approaches to treat these refractory tumours.

KRAS mutations are a driver event of pancreatic ductal adenocarcinoma; here, a subpopulation of dormant tumour cells, relying on oxidative phosphorylation for survival, is shown to be responsible for tumour relapse after treatment targeting the KRAS pathway. Respiration-dependent cancer stem cells KRAS mutations represent a driver event of pancreatic ductal adenocarcinoma. Targeting this pathway leads to tumour regression, but the frequency of relapse indicates that a fraction of tumour cells survives even in the absence of oncogenic signalling. Using a Kras /p53 mouse model of pancreatic cancer, in which the expression of oncogenic Kras can be switched off, Giulio Draetta and colleagues show that the subpopulation of dormant tumour cells that survives oncogene ablation and is responsible for tumour relapse is dependent on oxidative phosphorylation (OXPHOS) for survival. These cells show high sensitivity to OXPHOS inhibitors, which can inhibit tumour recurrence, suggesting that combined targeting of the KRAS pathway and mitochondrial respiration might be effective in the treatment of pancreatic cancer. Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers in western countries, with a median survival of 6 months and an extremely low percentage of long-term surviving patients. KRAS mutations are known to be a driver event of PDAC 1 , but targeting mutant KRAS has proved challenging 2 . Targeting oncogene-driven signalling pathways is a clinically validated approach for several devastating diseases 3 , 4 . Still, despite marked tumour shrinkage, the frequency of relapse indicates that a fraction of tumour cells survives shut down of oncogenic signalling 5 , 6 . Here we explore the role of mutant KRAS in PDAC maintenance using a recently developed inducible mouse model of mutated Kras 1 ( Kras G12D , herein KRas) in a p53 LoxP/WT background. We demonstrate that a subpopulation of dormant tumour cells surviving oncogene ablation (surviving cells) and responsible for tumour relapse has features of cancer stem cells and relies on oxidative phosphorylation for survival. Transcriptomic and metabolic analyses of surviving cells reveal prominent expression of genes governing mitochondrial function, autophagy and lysosome activity, as well as a strong reliance on mitochondrial respiration and a decreased dependence on glycolysis for cellular energetics. Accordingly, surviving cells show high sensitivity to oxidative phosphorylation inhibitors, which can inhibit tumour recurrence. Our integrated analyses illuminate a therapeutic strategy of combined targeting of the KRAS pathway and mitochondrial respiration to manage pancreatic cancer.

BACKGROUNDPancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies, with unpredictable responses to chemotherapy. Approaches to assay patient tumors before treatment and identify effective treatment regimens based on tumor sensitivities are lacking. We developed an organoid-based platform (OBP) to visually quantify patient-derived organoid (PDO) responses to drug treatments and associated tumor-stroma modulation for personalized PDAC therapy.METHODSWe retrospectively quantified apoptotic responses and tumor-stroma cell proportions in PDOs via 3D immunofluorescence imaging through annexin A5, α-smooth muscle actin (α-SMA), and cytokeratin 19 (CK-19) levels. Simultaneously, an ex vivo organoid drug sensitivity assay (ODSA) was used to measure responses to standard-of-care regimens. Differences between ODSA results and patient tumor responses were assessed by exact McNemar's test.RESULTSImmunofluorescence signals, organoid growth curves, and Ki-67 levels were measured and authenticated through the OBP for up to 14 days. ODSA drug responses were not different from patient tumor responses, as reflected by CA19-9 reductions following neoadjuvant chemotherapy (P = 0.99). PDOs demonstrated unique apoptotic and tumor-stroma modulation profiles (P < 0.0001). α-SMA/CK-19 ratio levels of more than 1.0 were associated with improved outcomes (P = 0.0179) and longer parental patient survival by Kaplan-Meier analysis (P = 0.0046).CONCLUSIONHeterogenous apoptotic drug responses and tumor-stroma modulation are present in PDOs after standard-of-care chemotherapy. Ratios of α-SMA and CK-19 levels in PDOs are associated with patient survival, and the OBP could aid in the selection of personalized therapies to improve the efficacy of systemic therapy in patients with PDAC.FUNDINGNIH/National Cancer Institute grants (K08CA218690, P01 CA117969, R50 CA243707-01A1, U54CA224065), the Skip Viragh Foundation, the Bettie Willerson Driver Cancer Research Fund, and a Cancer Center Support Grant for the Flow Cytometry and Cellular Imaging Core Facility (P30CA16672).

The therapeutic resistance of pancreatic ductal adenocarcinoma (PDAC) is partly ascribed to ineffective delivery of chemotherapy to cancer cells. We hypothesized that physical properties at vascular, extracellular, and cellular scales influence delivery of and response to gemcitabine-based therapy. We developed a method to measure mass transport properties during routine contrast-enhanced CT scans of individual human PDAC tumors. Additionally, we evaluated gemcitabine infusion during PDAC resection in 12 patients, measuring gemcitabine incorporation into tumor DNA and correlating its uptake with human equilibrative nucleoside transporter (hENT1) levels, stromal reaction, and CT-derived mass transport properties. We also studied associations between CT-derived transport properties and clinical outcomes in patients who received preoperative gemcitabine-based chemoradiotherapy for resectable PDAC. Transport modeling of 176 CT scans illustrated striking differences in transport properties between normal pancreas and tumor, with a wide array of enhancement profiles. Reflecting the interpatient differences in contrast enhancement, resected tumors exhibited dramatic differences in gemcitabine DNA incorporation, despite similar intravascular pharmacokinetics. Gemcitabine incorporation into tumor DNA was inversely related to CT-derived transport parameters and PDAC stromal score, after accounting for hENT1 levels. Moreover, stromal score directly correlated with CT-derived parameters. Among 110 patients who received preoperative gemcitabine-based chemoradiotherapy, CT-derived parameters correlated with pathological response and survival. Gemcitabine incorporation into tumor DNA is highly variable and correlates with multiscale transport properties that can be derived from routine CT scans. Furthermore, pretherapy CT-derived properties correlate with clinically relevant endpoints. Clinicaltrials.gov NCT01276613. Lustgarten Foundation (989161), Department of Defense (W81XWH-09-1-0212), NIH (U54CA151668, KCA088084).