Genetics and biology of pancreatic ductal adenocarcinoma

Hmga2 is dispensable for pancreatic cancer development, metastasis, and therapy resistance

Expression of the chromatin-associated protein HMGA2 correlates with progression, metastasis and therapy resistance in pancreatic ductal adenocarcinoma (PDAC). Hmga2 has also been identified as a marker of a transient subpopulation of PDAC cells that has increased metastatic ability. Here, we characterize the requirement for Hmga2 during growth, dissemination, and metastasis of PDAC in vivo using conditional inactivation of Hmga2 in well-established autochthonous mouse models of PDAC. Overall survival, primary tumour burden, presence of disseminated tumour cells in the peritoneal cavity or circulating tumour cells in the blood, and presence and number of metastases were not significantly different between mice with Hmga2-wildtype or Hmga2-deficient tumours. Treatment of mice with Hmga2-wildtype and Hmga2-deficient tumours with gemcitabine did not uncover a significant impact of Hmga2-deficiency on gemcitabine sensitivity. Hmga1 and Hmga2 overlap in their expression in both human and murine PDAC, however knockdown of Hmga1 in Hmga2-deficient cancer cells also did not decrease metastatic ability. Thus, Hmga2 remains a prognostic marker which identifies a metastatic cancer cell state in primary PDAC, however Hmga2 has limited if any direct functional impact on PDAC progression and therapy resistance.

Exome-wide analysis identifies three low-frequency missense variants associated with pancreatic cancer risk in Chinese populations

Germline coding variants have not been systematically investigated for pancreatic ductal adenocarcinoma (PDAC). Here we report an exome-wide investigation using the Illumina Human Exome Beadchip with 943 PDAC cases and 3908 controls in the Chinese population, followed by two independent replicate samples including 2142 cases and 4697 controls. We identify three low-frequency missense variants associated with the PDAC risk: rs34309238 in PKN1 (OR = 1.77, 95% CI: 1.48-2.12, P = 5.35 × 10-10), rs2242241 in DOK2 (OR = 1.85, 95% CI: 1.50-2.27, P = 4.34 × 10-9), and rs183117027 in APOB (OR = 2.34, 95% CI: 1.72-3.16, P = 4.21 × 10-8). Functional analyses show that the PKN1 rs34309238 variant significantly increases the level of phosphorylated PKN1 and thus enhances PDAC cells' proliferation by phosphorylating and activating the FAK/PI3K/AKT pathway. These findings highlight the significance of coding variants in the development of PDAC and provide more insights into the prevention of this disease.

Assessment of mutation probabilities of KRAS G12 missense mutants and their long-timescale dynamics by atomistic molecular simulations and Markov state modeling

A mutated KRAS protein is frequently observed in human cancers. Traditionally, the oncogenic properties of KRAS missense mutants at position 12 (G12X) have been considered as equal. Here, by assessing the probabilities of occurrence of all KRAS G12X mutations and KRAS dynamics we show that this assumption does not hold true. Instead, our findings revealed an outstanding mutational bias. We conducted a thorough mutational analysis of KRAS G12X mutations and assessed to what extent the observed mutation frequencies follow a random distribution. Unique tissue-specific frequencies are displayed with specific mutations, especially with G12R, which cannot be explained by random probabilities. To clarify the underlying causes for the nonrandom probabilities, we conducted extensive atomistic molecular dynamics simulations (170 μs) to study the differences of G12X mutations on a molecular level. The simulations revealed an allosteric hydrophobic signaling network in KRAS, and that protein dynamics is altered among the G12X mutants and as such differs from the wild-type and is mutation-specific. The shift in long-timescale conformational dynamics was confirmed with Markov state modeling. A G12X mutation was found to modify KRAS dynamics in an allosteric way, which is especially manifested in the switch regions that are responsible for the effector protein binding. The findings provide a basis to understand better the oncogenic properties of KRAS G12X mutants and the consequences of the observed nonrandom frequencies of specific G12X mutations.

The oncogene KRAS is frequently mutated in various cancers. When the amino acid glycine 12 is mutated, KRAS protein acquires oncogenic properties that result in tumor cell-growth and cancer progression. These mutations prevail especially in the pancreatic ductal adenocarcinoma, which is a cancer with an exceptionally dismal prognosis. To date, there is a limited understanding of the different mutations at the position 12, also regarding whether the different mutations would have different consequences. These discrepancies could have major implications for the future drug therapies targeting KRAS mutant harboring tumors. In this study, we made a critical assessment of the observed frequency of KRAS G12X mutations and the underlying causes for these frequencies. We also assessed KRAS G12X mutant discrepancies on an atomistic level by utilizing state-of-the-art molecular dynamics simulations. We found that the dynamics of the mutants does not only differ from the wild-type protein, but there is also a profound difference among the different mutants. These results emphasize that the different KRAS G12X mutations are not equal, and thereby they suggest that the future research related to mutant KRAS biology should account for these observations.

KRAS: The Critical Driver and Therapeutic Target for Pancreatic Cancer

RAS genes (HRAS, KRAS, and NRAS) comprise the most frequently mutated oncogene family in human cancer. With the highest RAS mutation frequencies seen with the top three causes of cancer deaths in the United States (lung, colorectal, and pancreatic cancer), the development of anti-RAS therapies is a major priority for cancer research. Despite more than three decades of intense effort, no effective RAS inhibitors have yet to reach the cancer patient. With bitter lessons learned from past failures and with new ideas and strategies, there is renewed hope that undruggable RAS may finally be conquered. With the KRAS isoform mutated in 84% of all RAS-mutant cancers, we focus on KRAS. With a near 100% KRAS mutation frequency, pancreatic ductal adenocarcinoma (PDAC) is considered the most RAS-addicted of all cancers. We review the role of KRAS as a driver and therapeutic target in PDAC.

Genetic Alterations of Periampullary and Pancreatic Ductal Adenocarcinoma: An Overview

Pancreatic Ductal AdenoCarcinoma (PDAC) is one of the most lethal malignancies of all solid cancers. Precancerous lesions for PDAC include PanIN, IPMNs and MCNs. PDAC has a poor prognosis with a 5-year survival of approximately 6%. Whereas Periampulary AdenoCarcinoma (PAC) having four anatomic subtypes, pancreatic, Common Bile Duct (CBD), ampullary and duodenum shows relative better prognosis. The highest incidence of PDAC has been reported with black with respect to white population. Similarly, incidence rate of PAC also differs with different ethnic populations. Several lifestyle, environmental and occupational exposures including long-term diabetes, obesity, and smoking, have been linked to PDAC, however, for PAC the causal risk factors were poorly described. It is now clear that PDAC and PAC are a multi-stage process resulting from the accumulation of genomic alterations in the somatic DNA of normal cells as well as inherited mutations. Approximately 10% of PDAC have a familial inheritance. Germline mutations in CDKN2A, BRCA2, STK11, PALB2, PRSS1, etc., as well as certain syndromes have been well associated with predisposition to PDAC. KRAS, CDKN2A, TP53 and SMAD4 are the 4 "mountains" (high-frequency driver genes) which have been known to earliest somatic alterations for PDAC while relatively less frequent in PAC. Our understanding of the molecular carcinogenesis has improved in the last few years due to extensive research on PDAC which was not well explored in case of PAC. The genetic alterations that have been identified in PDAC and different subgroups of PAC are important implications for the development of genetic screening test, early diagnosis, and prognostic genetic markers. The present review will provide a brief overview of the incidence and prevalence of PDAC and PAC, mainly, increased risk in India, the several kinds of risk factors associated with the diseases as well as required genetic alterations for disease initiation and progression.

MT1-MMP as a PET Imaging Biomarker for Pancreas Cancer Management

Pancreatic ductal adenocarcinoma (PDAC) continues to be one of the deadliest cancers for which optimal diagnostic tools are still greatly needed. Identification of PDAC-specific molecular markers would be extremely useful to improve disease diagnosis and follow-up. MT1-MMP has long been involved in pancreatic cancer, especially in tumour invasion and metastasis. In this study, we aim to ascertain the suitability of MT1-MMP as a biomarker for positron emission tomography (PET) imaging. Two probes were assessed and compared for this purpose, an MT1-MMP-specific binding peptide (MT1-AF7p) and a specific antibody (LEM2/15), labelled, respectively, with ⁶⁸Ga and with ⁸⁹Zr. PET imaging with both probes was conducted in patient-derived xenograft (PDX), subcutaneous and orthotopic, PDAC mouse models, and in a cancer cell line (CAPAN-2)-derived xenograft (CDX) model. Both radiolabelled tracers were successful in identifying, by means of PET imaging techniques, tumour tissues expressing MT1-MMP although they did so at different uptake levels. The ⁸⁹Zr-DFO-LEM2/15 probe showed greater specific activity compared to the ⁶⁸Ga-labelled peptide. The mean value of tumour uptake for the ⁸⁹Zr-DFO-LEM2/15 probe (5.67 ± 1.11%ID/g, n=28) was 25-30 times higher than that of the ⁶⁸Ga-DOTA-AF7p ones. Tumour/blood ratios (1.13 ± 0.51 and 1.44 ± 0.43 at 5 and 7 days of ⁸⁹Zr-DFO-LEM2/15 after injection) were higher than those estimated for ⁶⁸Ga-DOTA-AF7p probes (of approximately tumour/blood ratio = 0.5 at 90 min after injection). Our findings strongly point out that (i) the in vivo detection of MT1-MMP by PET imaging is a promising strategy for PDAC diagnosis and (ii) labelled LEM2/15 antibody is a better candidate than MT1-AF7p for PDAC detection.

microRNAs: Novel regulators of the TGF-β pathway in pancreatic ductal adenocarcinoma

We identified that transforming growth factor-β (TGF-β) induces long non-coding RNA (lncRNA) MIR100HG along with its host microRNAs (miRNAs) miR-100 and miR-125b, to regulate its response in pancreatic ductal adenocarcinoma (PDAC). Importantly let-7a, despite originating from MIR100HG, remains unchanged because post-transcriptionally repressed by lin-28 homolog B (LIN28B). A novel method for global miRNA-target discovery identified that miR-100/125b regulates crucial PDAC pathways.

Therapeutic potential of combined BRAF/MEK blockade in BRAF-wild type preclinical tumor models

Background

Mounting evidence suggests that RAF-mediated MEK activation plays a crucial role in paradox MAPK (re)activation, leading to resistance and therapeutic failure with agents hitting a single step along the MAPK cascade.

Methods

We examined the molecular and functional effects of single and combined BRAF (dabrafenib), pan-RAF (RAF265), MEK (trametinib) and EGFR/HER2 (lapatinib) inhibition, using Western Blot and conservative isobologram analysis to assess functional synergism, and explored genetic determinants of synergistic interactions. Immunoprecipitation based assays were used to detect the interaction between BRAF and CRAF. The Mann-Whitney U test was used for comparing quantitative variables.

Results

Here we demonstrated that a combination of MEK and BRAF inhibitors overcomes paradoxical MAPK activation (induced by BRAF inhibitors) in BRAF-wt/RAS-mut NSCLC and PDAC in vitro. This results in growth inhibitory synergism, both in vitro and in vivo, in the majority (65%) of the cellular models analyzed, encompassing cell lines and patient-derived cancer stem cells and organoids. However, RAS mutational status is not the sole determinant of functional synergism between RAF and MEK inhibitors, as demonstrated in KRAS isogenic tumor cell line models. Moreover, in EGFR-driven contexts, paradoxical MAPK (re)activation in response to selective BRAF inhibition was dependent on EGFR family signaling and could be offset by simultaneous EGFR/HER-2 blockade.

Conclusions

Overall, our data indicate that RAF inhibition-induced paradoxical MAPK activation could be exploited for therapeutic purposes by simultaneously targeting both RAF and MEK (and potentially EGFR family members) in appropriate molecular contexts. KRAS mutation per se does not effectively predict therapeutic synergism and other biomarkers need to be developed to identify patients potentially deriving benefit from combined BRAF/MEK targeting.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0820-5) contains supplementary material, which is available to authorized users.

Inflammatory potential of diet and risk of pancreatic cancer in the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial

Inflammation plays a central role in pancreatic cancer etiology and can be modulated by diet. We aimed to examine the association between the inflammatory potential of diet, assessed with the Dietary Inflammatory Index (DII®), and pancreatic cancer risk in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial prospective cohort. Our study included 101,449 participants aged 52-78 years at baseline who completed both baseline questionnaire and a diet history questionnaire. Energy-adjusted DII (E-DII) scores were computed based on food and supplement intake. Cox proportional hazards models and time dependent Cox models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) with participants in the lowest E-DII quintile (most anti-inflammatory scores) as referent. After a median 8.5 years of follow-up, 328 pancreatic cancer cases were identified. E-DII scores were not associated with pancreatic cancer risk in the multivariable model (HRQ5vsQ1  = 0.94; 95% CI = 0.66-1.35; p-trend = 0.43). Time significantly modified the association (p-interaction = 0.01). During follow up <4 years, there was suggestive evidence of an inverse association between E-DII and pancreatic cancer (HRQ5vsQ1  = 0.60; 95% CI = 0.35-1.02; p-trend = 0.20) while there was a significant positive trend in the follow up ≥4 years (HRQ5vsQ1  = 1.31; 95% CI = 0.83-2.08; p-trend = 0.03). Similar results were observed for E-DII from food only. Our study does not support an association between inflammatory potential of diet and pancreatic cancer risk; however, heterogeneous results were obtained with different follow-up times. These divergent associations may result from the influences of undetected disease in the short-term.

Signal-Targeted Therapies and Resistance Mechanisms in Pancreatic Cancer: Future Developments Reside in Proteomics

For patients with metastatic pancreatic cancer that are not eligible for surgery, signal-targeted therapies have so far failed to significantly improve survival. These therapeutic options have been tested in phase II/III clinical trials mostly in combination with the reference treatment gemcitabine. Innovative therapies aim to annihilate oncogenic dependency, or to normalize the tumoural stroma to allow immune cells to function and/or re-vascularisation to occur. Large scale transcriptomic and genomic analysis revealed that pancreatic cancers display great heterogeneity but failed to clearly delineate specific oncogene dependency, besides oncogenic Kras. Beyond these approaches, proteomics appears to be an appropriate approach to classify signal dependency and to identify specific alterations at the targetable level. However, due to difficulties in sampling, proteomic data for this pathology are scarce. In this review, we will discuss the current state of clinical trials for targeted therapies against pancreatic cancer. We will then highlight the most recent proteomic data for pancreatic tumours and their metastasis, which could help to identify major oncogenic signalling dependencies, as well as provide future leads to explain why pancreatic tumours are intrinsically resistant to signal-targeted therapies. We will finally discuss how studies on phosphatidylinositol-3-kinase (PI3K) signalling, as the paradigmatic pro-tumoural signal downstream of oncogenic Kras in pancreatic cancer, would benefit from exploratory proteomics to increase the efficiency of targeted therapies.

The Heterocellular Emergence of Colorectal Cancer

Tissues contain multiple different cell types and can be considered to be heterocellular systems. Signaling between different cells allows tissues to achieve phenotypes that no cell type can achieve in isolation. Such emergent tissue-level phenotypes can be said to 'supervene upon' heterocellular signaling. It is proposed here that cancer is also an emergent phenotype that supervenes upon heterocellular signaling. Using colorectal cancer (CRC) as an example, I review how heterotypic cells differentially communicate to support emergent malignancy. Studying tumors as integrated heterocellular systems - rather than as solitary expansions of mutated cells - may reveal novel ways to treat cancer.

E2F signature is predictive for the pancreatic adenocarcinoma clinical outcome and sensitivity to E2F inhibitors, but not for the response to cytotoxic-based treatments

The main goal of this study was to find out strategies of clinical relevance to classify patients with a pancreatic ductal adenocarcinoma (PDAC) for individualized treatments. In the present study a set of 55 patient-derived xenografts (PDX) were obtained and their transcriptome were analyzed by using an Affymetrix approach. A supervised bioinformatics-based analysis let us to classify these PDX in two main groups named E2F-highly dependent and E2F-lowly dependent. Afterwards their characterization by using a Kaplan-Meier analysis demonstrated that E2F high patients survived significantly less than E2F low patients (9.5 months vs. 16.8 months; p = 0.0066). Then we tried to establish if E2F transcriptional target levels were associated to the response to cytotoxic treatments by comparing the IC50 values of E2F high and E2F low cells after gemcitabine, 5-fluorouracil, oxaliplatin, docetaxel or irinotecan treatment, and no association was found. Then we identified an E2F inhibitor compound, named ly101-4B, and we observed that E2F-higly dependent cells were more sensitive to its treatment (IC50 of 19.4 ± 1.8 µM vs. 44.1 ± 4.4 µM; p = 0.0061). In conclusion, in this work we describe an E2F target expression-based classification that could be predictive for patient outcome, but more important, for the sensitivity of tumors to the E2F inhibitors as a treatment. Finally, we can assume that phenotypic characterization, essentially by an RNA expression analysis of the PDAC, can help to predict their clinical outcome and their response to some treatments when are rationally selected.

In vivo reprogramming drives Kras-induced cancer development

The faithful shutdown of the somatic program occurs in the early stage of reprogramming. Here, we examined the effect of in vivo reprogramming on Kras-induced cancer development. We show that the transient expression of reprogramming factors (1-3 days) in pancreatic acinar cells results in the transient repression of acinar cell enhancers, which are similarly observed in pancreatitis. We next demonstrate that Kras and p53 mutations are insufficient to induce ERK signaling in the pancreas. Notably, the transient expression of reprogramming factors in Kras mutant mice is sufficient to induce the robust and persistent activation of ERK signaling in acinar cells and rapid formation of pancreatic ductal adenocarcinoma. In contrast, the forced expression of acinar cell-related transcription factors inhibits the pancreatitis-induced activation of ERK signaling and development of precancerous lesions in Kras-mutated acinar cells. These results underscore a crucial role of dedifferentiation-associated epigenetic regulations in the initiation of pancreatic cancers.

Pancreatic Ductal Adenocarcinoma: A Strong Imbalance of Good and Bad Immunological Cops in the Tumor Microenvironment

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal cancers with very few available treatments. For many decades, gemcitabine was the only treatment for patients with PDAC. A recent attempt to improve patient survival by combining this chemotherapy with FOLFIRINOX and nab-paclitaxel failed and instead resulted in increased toxicity. Novel therapies are urgently required to improve PDAC patient survival. New treatments in other cancers such as melanoma, non-small-cell lung cancer, and renal cancer have emerged, based on immunotherapy targeting the immune checkpoints cytotoxic T-lymphocyte-associated antigen 4 or programmed death 1 ligand. However, the first clinical trials using such immune checkpoint inhibitors in PDAC have had limited success. Resistance to immunotherapy in PDAC remains unclear but could be due to tissue components (cancer-associated fibroblasts, desmoplasia, hypoxia) and to the imbalance between immunosuppressive and effector immune populations in the tumor microenvironment. In this review, we analyzed the presence of “good and bad immunological cops” in PDAC and discussed the significance of changes in their balance.

TGF-β induces miR-100 and miR-125b but blocks let-7a through LIN28B controlling PDAC progression

TGF-β/Activin induces epithelial-to-mesenchymal transition and stemness in pancreatic ductal adenocarcinoma (PDAC). However, the microRNAs (miRNAs) regulated during this response have remained yet undetermined. Here, we show that TGF-β transcriptionally induces MIR100HG lncRNA, containing miR-100, miR-125b and let-7a in its intron, via SMAD2/3. Interestingly, we find that although the pro-tumourigenic miR-100 and miR-125b accordingly increase, the amount of anti-tumourigenic let-7a is unchanged, as TGF-β also induces LIN28B inhibiting its maturation. Notably, we demonstrate that inactivation of miR-125b or miR-100 affects the TGF-β-mediated response indicating that these miRNAs are important TGF-β effectors. We integrate AGO2-RIP-seq with RNA-seq to identify the global regulation exerted by these miRNAs in PDAC cells. Transcripts targeted by miR-125b and miR-100 significantly overlap and mainly inhibit p53 and cell-cell junctions' pathways. Together, we uncover that TGF-β induces an lncRNA, whose encoded miRNAs, miR-100, let-7a and miR-125b play opposing roles in controlling PDAC tumourigenesis.

Extracellular matrix composition modulates PDAC parenchymal and stem cell plasticity and behavior through the secretome

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers. Its aggressiveness is driven by an intense fibrotic desmoplastic reaction in which the increasingly collagen I-rich extracellular matrix (ECM) and several cell types, including cancer stem cells (CSCs), create a tumor-supportive environment. However, how ECM composition regulates CSC dynamics and their relationship with the principle parenchymal tumor population to promote early invasive growth is not yet characterized. For this, we utilized a platform of 3D organotypic cultures composed of laminin-rich Matrigel, representative of an early tumor, plus increasing concentrations of collagen I to simulate malignant stroma progression. As ECM collagen I increases, CSCs progress from a rapidly growing, vascular phenotype to a slower growing, avascular phase, while maintaining their endothelial-like gene signatures. This transition is supported autocrinically by the CSCs and paracrinically by the parenchymal cells via their ECM-dependent secretomes. Indeed, when growing on an early tumor ECM, the CSCs are dedicated toward the preparation of a vascular niche by (a) activating their growth program, (b) secreting high levels of proangiogenic factors which stimulate both angiogenesis and vasculogenic mimicry, and (c) overexpressing VEGFR-2, which is activated by VEGF secreted by both the CSC and parenchymal cells. On Matrigel, the more differentiated parenchymal tumor cell population had reduced growth but a high invasive capacity. This concerted high local invasion of parenchymal cells into the CSC-derived vascular network suggests that a symbiotic relationship between the parenchymal cells and the CSCs underlies the initiation and maintenance of early PDAC infiltration and metastasis.

The plasticity of pancreatic cancer metabolism in tumor progression and therapeutic resistance

Pancreatic ductal adenocarcinoma (PDA) is an aggressive cancer that is highly refractory to the current standards of care. The difficulty in treating this disease is due to a number of different factors, including altered metabolism. In PDA, the metabolic rewiring favors anabolic reactions which supply the cancer cell with necessary cellular building blocks for unconstrained growth. Furthermore, PDA cells display high levels of basal autophagy and macropinocytosis. KRAS is the driving oncogene in PDA and many of the metabolic changes are downstream of its activation. Together, these unique pathways for nutrient utilization and acquisition result in metabolic plasticity enabling cells to rapidly adapt to nutrient and oxygen fluctuations. This remarkable adaptability has been implicated as a cause of the intense therapeutic resistance. In this review, we discuss metabolic pathways in PDA tumors and highlight how they contribute to the pathogenesis and treatment of the disease.

Yes-associated protein (YAP) in pancreatic cancer: at the epicenter of a targetable signaling network associated with patient survival

Pancreatic ductal adenocarcinoma (PDAC) is generally a fatal disease with no efficacious treatment modalities. Elucidation of signaling mechanisms that will lead to the identification of novel targets for therapy and chemoprevention is urgently needed. Here, we review the role of Yes-associated protein (YAP) and WW-domain-containing Transcriptional co-Activator with a PDZ-binding motif (TAZ) in the development of PDAC. These oncogenic proteins are at the center of a signaling network that involves multiple upstream signals and downstream YAP-regulated genes. We also discuss the clinical significance of the YAP signaling network in PDAC using a recently published interactive open-access database (www.proteinatlas.org/pathology) that allows genome-wide exploration of the impact of individual proteins on survival outcomes. Multiple YAP/TEAD-regulated genes, including AJUBA, ANLN, AREG, ARHGAP29, AURKA, BUB1, CCND1, CDK6, CXCL5, EDN2, DKK1, FOSL1,FOXM1, HBEGF, IGFBP2, JAG1, NOTCH2, RHAMM, RRM2, SERP1, and ZWILCH, are associated with unfavorable survival of PDAC patients. Similarly, components of AP-1 that synergize with YAP (FOSL1), growth factors (TGFα, EPEG, and HBEGF), a specific integrin (ITGA2), heptahelical receptors (P2Y₂R, GPR87) and an inhibitor of the Hippo pathway (MUC1), all of which stimulate YAP activity, are associated with unfavorable survival of PDAC patients. By contrast, YAP inhibitory pathways (STRAD/LKB-1/AMPK, PKA/LATS, and TSC/mTORC1) indicate a favorable prognosis. These associations emphasize that the YAP signaling network correlates with poor survival of pancreatic cancer patients. We conclude that the YAP pathway is a major determinant of clinical aggressiveness in PDAC patients and a target for therapeutic and preventive strategies in this disease.

Yes-associated protein (YAP) signaling contributes to pancreatic cancer progression and is associated with poor patient survival. Previous studies have shown that YAP activates genes involved in cell proliferation to incite tumor growth and metastasis. Enrique Rozengurt and colleagues at University of California Los Angeles review the latest knowledge on YAP signaling and used the open access database The Human Protein Atlas to analyze the gene expression profile and prognosis of 176 patients with pancreatic ductal adenocarcinoma. Activation of upstream or downstream elements of the YAP signaling pathway correlated with shorter survival in patients. Conversely, the activation of signaling pathways that oppose YAP signaling were associated with a more favorable prognosis. These findings highlight YAP signaling pathway components as both prognostic markers and potential targets for developing much needed therapeutic and preventative strategies.

Possible Molecular Markers for the Diagnosis of Pancreatic Ductal Adenocarcinoma

BACKGROUND We aimed to identify pivotal genes and pathways involved in pancreatic ductal adenocarcinoma (PDAC), and explore possible molecular markers for the early diagnosis of the disease. MATERIAL AND METHODS The array data of GSE74629, including 34 PDAC samples and 16 healthy samples, was downloaded from GEO (Gene Expression Omnibus) database. Then, the DEGs (differentially expressed genes) in PDAC samples were compared with healthy samples using limma (linear models for microarray). Gene functional interaction networks were analyzed with Cytoscape and ReactomeFIViz. PPI networks were constructed with Cytoscape software. In addition, PPI (protein-protein interaction) network clustering modules were analyzed with ClusterONE, and the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analyses for modules were performed. RESULTS A total of 630 upregulated and 1,002 downregulated DEGs were identified in PDAC samples compared with healthy samples. Some ribosomal protein genes with higher average correlation in module 0 were enriched in the ribosome pathway. NUP107 (nucleoporin 107 kDa) and NUP160 (nucleoporin 160 kDa) were enriched in module 3. HNRNPU (heterogeneous nuclear ribonucleoprotein U) with higher average correlation in module 8 was enriched in the spliceosome pathway. The ribosome pathway and the spliceosome pathway were significantly enriched in cluster 1 and cluster 2, respectively. CONCLUSIONS Ribosomal protein genes Nup170, Nup160, and HNRNPU, and the ribosome pathway as well as the spliceosome pathway may play important roles in PDAC progression. In addition, ribosomal protein genes Nup170, Nup160, and HNRNPU may be used as possible molecular markers for the early diagnosis of the disease.

Identification and Validation of a Diagnostic and Prognostic Multi-Gene Biomarker Panel for Pancreatic Ductal Adenocarcinoma

Late diagnosis and systemic dissemination essentially contribute to the invariably poor prognosis of pancreatic ductal adenocarcinoma (PDAC). Therefore, the development of diagnostic biomarkers for PDAC are urgently needed to improve patient stratification and outcome in the clinic. By studying the transcriptomes of independent PDAC patient cohorts of tumor and non-tumor tissues, we identified 81 robustly regulated genes, through a novel, generally applicable meta-analysis. Using consensus clustering on co-expression values revealed four distinct clusters with genes originating from exocrine/endocrine pancreas, stromal and tumor cells. Three clusters were strongly associated with survival of PDAC patients based on TCGA database underlining the prognostic potential of the identified genes. With the added information of impact of survival and the robustness within the meta-analysis, we extracted a 17-gene subset for further validation. We show that it did not only discriminate PDAC from non-tumor tissue and stroma in fresh-frozen as well as formalin-fixed paraffin embedded samples, but also detected pancreatic precursor lesions and singled out pancreatitis samples. Moreover, the classifier discriminated PDAC from other cancers in the TCGA database. In addition, we experimentally validated the classifier in PDAC patients on transcript level using qPCR and exemplify the usage on protein level for three proteins (AHNAK2, LAMC2, TFF1) using immunohistochemistry and for two secreted proteins (TFF1, SERPINB5) using ELISA-based protein detection in blood-plasma. In conclusion, we present a novel robust diagnostic and prognostic gene signature for PDAC with future potential applicability in the clinic.

Role of Gene Therapy in Pancreatic Cancer-A Review

Mortality from pancreatic ductal adenocarcinoma (PDAC) has remained essentially unchanged for decades and its relative contribution to overall cancer death is projected to only increase in the coming years. Current treatment for PDAC includes aggressive chemotherapy and surgical resection in a limited number of patients, with median survival of optimal treatment rather dismal. Recent advances in gene therapies offer novel opportunities for treatment, even in those with locally advanced disease. In this review, we summarize emerging techniques to the design and administration of virotherapy, synthetic vectors, and gene-editing technology. Despite these promising advances, shortcomings continue to exist and here will also be highlighted those approaches to overcoming obstacles in current laboratory and clinical research.

BRSK2 induced by nutrient deprivation promotes Akt activity in pancreatic cancer via downregulation of mTOR activity

Neoplastic cells in pancreatic ductual adenocarcinoma (PDAC) survive in an energy-deprived milieu, and hyper-activation of Akt is thought to contribute to the neoplastic cell survival in PDAC. Kras activating mutations, common in PDAC, was believed to be the major driver of Akt activation. However, the inhibitor to Kras was not therapeutic for PDAC patients. This implied that PDAC cells might harbor an intrinsic merit that strengthens Akt activity. Here we showed that BRSK2, a serine/threonine-protein kinase of AMPK family, was induced by nutrient deprivation in PDAC cells and suppressed mTORC1 activity via phosphorylation of tuberous sclerosis complex 2 (TSC2). The suppression of mTORC1 activity in PDAC results in a dominant loss of feedback inhibition on Akt activity by mTORC1, consequently enhancing cell survival. This finding indicates that the intrinsic molecular merit that BRSK2 provides is a survival advantage to PDAC cells and strengthens the invasiveness of these neoplastic cells in energy-deprived environments.

Loss of KDM6A Activates Super-Enhancers to Induce Gender-Specific Squamous-like Pancreatic Cancer and Confers Sensitivity to BET Inhibitors

KDM6A, an X chromosome-encoded histone demethylase and member of the COMPASS-like complex, is frequently mutated in a broad spectrum of malignancies and contributes to oncogenesis with poorly characterized mechanisms. We found that KDM6A loss induced squamous-like, metastatic pancreatic cancer selectively in females through deregulation of the COMPASS-like complex and aberrant activation of super-enhancers regulating ΔNp63, MYC, and RUNX3 oncogenes. This subtype of tumor developed in males had concomitant loss of UTY and KDM6A, suggesting overlapping roles, and points to largely demethylase independent tumor suppressor functions. We also demonstrate that KDM6A-deficient pancreatic cancer is selectively sensitive to BET inhibitors, which reversed squamous differentiation and restrained tumor growth in vivo, highlighting a therapeutic niche for patient tailored therapies.

Do anti-stroma therapies improve extrinsic resistance to increase the efficacy of gemcitabine in pancreatic cancer?

Pancreatic ductal adenocarcinoma (PDAC) is among the most devastating human malignancies, with approximately 20-30% of PDAC patients receiving the surgical resection with curative intent. Although many studies have focused on finding ideal "drug chaperones" that facilitate and/or potentiate the effects of gemcitabine (GEM) in pancreatic cancer, a significant benefit in overall survival could not be demonstrated for any of these combination therapies in PDAC. Given that pancreatic cancer is characterized by desmoplasia and the dual biological roles of stroma in pancreatic cancer, we reassess the importance of stroma in GEM-based therapeutic approaches in light of current findings. This review is focused on understanding the role of stromal components in the extrinsic resistance to GEM and whether anti-stroma therapies have a positive effect on the GEM delivery. This work contributes to the development of novel and promising combination GEM-based regimens that have achieved significant survival benefits for the patients with pancreatic cancer.

Dendron-Grafted Polylysine-Based Dual-Modal Nanoprobe for Ultra-Early Diagnosis of Pancreatic Precancerosis via Targeting a Urokinase-Type Plasminogen Activator Receptor

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer death. Early detection of precancerous pancreatic intraepithelial neoplasia (PanIN) tissues is an urgent challenge to improve the PDAC prognosis. Here, a urokinase-type plasminogen activator receptor (uPAR)-targeted magnetic resonance (MR)/near-infrared fluorescence (NIRF) dual-modal nanoprobe dendron-grafted polylysine (DGL)-U11 for ultra-early detection of pancreatic precancerosis is reported. Because of its good biocompatibility and biodegradability, globular architecture, and well-defined reactive groups, the DGL is chosen as the platform to load with a pancreatic tumor-targeting peptide U11, a magnetic resonance contrast agent Gd3+ -diethylene triamine pentaacetic acid, and a near-infrared fluorescent cyanine dye Cy5.5. The nanoprobe DGL-U11 has several preferable characteristics, such as active peptide targeting to activator receptor, good biocompatibility, dual-modal imaging diagnosis, and well controlled diameter in a range of 15-25 nm. Upon incorporation of the active U11 peptide target to the overexpressed activator receptor uPAR, the targeted nanoprobe DGL-U11 can increase to the earlier PanIN-II stage through in vivo NIRF imaging. Labeled with both MR and NIRF bioimaging reporters, the uPAR-targeted dual-modal nanoprobe is very effective in the targeted imaging of precancerous PanINs and PDAC lesions with high sensitivity and spatial resolution, providing a promising platform to the ultra-early detection of PDAC.

A novel method for RNA extraction from FFPE samples reveals significant differences in biomarker expression between orthotopic and subcutaneous pancreatic cancer patient-derived xenografts

Next-generation sequencing (NGS) can identify and validate new biomarkers of cancer onset, progression and therapy resistance. Substantial archives of formalin-fixed, paraffin-embedded (FFPE) cancer samples from patients represent a rich resource for linking molecular signatures to clinical data. However, performing NGS on FFPE samples is limited by poor RNA purification methods. To address this hurdle, we developed an improved methodology for extracting high-quality RNA from FFPE samples. By briefly integrating a newly-designed micro-homogenizing (mH) tool with commercially available FFPE RNA extraction protocols, RNA recovery is increased by approximately 3-fold while maintaining standard A260/A280 ratios and RNA quality index (RQI) values. Furthermore, we demonstrate that the mH-purified FFPE RNAs are longer and of higher integrity. Previous studies have suggested that pancreatic ductal adenocarcinoma (PDAC) gene expression signatures vary significantly under in vitro versus in vivo and in vivo subcutaneous versus orthotopic conditions. By using our improved mH-based method, we were able to preserve established expression patterns of KRas-dependency genes within these three unique microenvironments. Finally, expression analysis of novel biomarkers in KRas mutant PDAC samples revealed that PEAK1 decreases and MST1R increases by over 100-fold in orthotopic versus subcutaneous microenvironments. Interestingly, however, only PEAK1 levels remain elevated in orthotopically grown KRas wild-type PDAC cells. These results demonstrate the critical nature of the orthotopic tumor microenvironment when evaluating the clinical relevance of new biomarkers in cells or patient-derived samples. Furthermore, this new mH-based FFPE RNA extraction method has the potential to enhance and expand future FFPE-RNA-NGS cancer biomarker studies.

Unique metabolic features of pancreatic cancer stroma: relevance to the tumor compartment, prognosis, and invasive potential

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis. The aggressiveness and therapeutic recalcitrance of this malignancy has been attributed to multiple factors including the influence of an active desmoplastic stroma. How the stromal microenvironment of PDAC contributes to the fatal nature of this disease is not well defined. In the analysis of clinical specimens, we observed diverse expression of the hypoxic marker carbonic anhydrase IX and the lactate transporter MCT4 in the stromal compartment. These stromal features were associated with the epithelial to mesenchymal phenotype in PDAC tumor cells, and with shorter patient survival. Cultured cancer-associated fibroblasts (CAFs) derived from primary PDAC exhibited a high basal level of hypoxia inducible factor 1a (HIF1α) that was both required and sufficient to modulate the expression of MCT4. This event was associated with increased transcription and protein synthesis of HIF1α in CAFs relative to PDAC cell lines, while surprisingly the protein turnover rate was equivalent. CAFs utilized glucose predominantly for glycolytic intermediates, whereas glutamine was the preferred metabolite for the TCA cycle. Unlike PDAC cell lines, CAFs were resistant to glucose withdrawal but sensitive to glutamine depletion. Consistent with the lack of reliance on glucose, CAFs could survive the acute depletion of MCT4. In co-culture and xenograft studies CAFs stimulated the invasive potential and metastatic spread of PDAC cell lines through a mechanism dependent on HIF1α and MCT4. Together, these data indicate that stromal metabolic features influence PDAC tumor cells to promote invasiveness and metastatic potential and associate with poor outcome in patients with PDAC.

A KRAS wild type mutational status confers a survival advantage in pancreatic ductal adenocarcinoma

Background

The KRAS oncogene is a driver mutation and is present in greater than 90% of pancreatic ductal adenocarcinomas (PDAC). A subset of these tumors, however, do not harbor mutations in KRAS (wild type KRAS). Studies have shown that patients with mutated KRAS have a poorer survival on first-line gemcitabine-based chemotherapy compared to wild type KRAS. In this study, we examined a cohort of patients with PDAC at our institution who were either wild type or mutant for the KRAS gene and assessed for differences in survival and response to different chemotherapeutic regimens.

Methods

We examined clinical records of patients treated at the Abramson Cancer Center of the University of Pennsylvania from 2013 to 2017. Patients with a pancreatic mass and a histologic diagnosis of pancreatic or pancreaticobiliary adenocarcinoma were identified. Thirty-nine patients with PDAC who underwent tumor sequencing at Penn Medicine's Center for Personalized Diagnostics (CPD) were selected for further study. Twelve patients were identified whose tumors were KRAS wild type. Twenty-seven patients with PDAC whose tumors harbored KRAS mutations were selected as controls (KRAS mutant).

Results

We noted a longer overall survival (OS) among KRAS wild type patients compared to KRAS mutant patients (P=0.026). This was independent of the age at diagnosis, patient gender, stage of diagnosis, tumor morphology, mismatch repair (MMR) status, and chemotherapeutic regimen.

Conclusions

Similar to previously reported studies, PDAC with a KRAS wild type mutational profile has a better prognosis with a longer OS. This improved prognosis is independent of the protocol utilized in therapy for these patients. Our findings suggest that future clinical trials in pancreatic cancer should take into consideration the presence of KRAS mutations in their pre-planned analysis when assessing the efficacy of a novel therapeutic approach. This may be a crucial factor in trial concepts and outcomes.

Long non-coding RNA XLOC_000647 suppresses progression of pancreatic cancer and decreases epithelial-mesenchymal transition-induced cell invasion by down-regulating NLRP3

BACKGROUND

Long non-coding RNAs (lncRNAs) play an important role in the development and progression of various tumors, including pancreatic cancer (PC). Recent studies have shown that lncRNAs can 'act in cis' to regulate the expression of its neighboring genes. Previously, we used lncRNAs microarray to identify a novel lncRNA termed XLOC_000647 that was down-regulated in PC tissues. However, the expression and function of XLOC_000647 in PC remain unclear.

METHODS

The expression of XLOC_000647 and NLRP3 in PC specimens and cell lines were detected by quantitative real-time PCR. Transwell assays were used to determine migration and invasion of PC cells. Western blot was carried out for detection of epithelial-mesenchymal transition (EMT) markers in PC cells. The effect of XLOC_000647 on PC cells was assessed in vitro and in vivo. The function of NOD-like receptor family pyrin domain-containing 3 (NLRP3) in PC was investigated in vitro. In addition, the regulation of NLRP3 by XLOC_000647 in PC was examined in vitro.

RESULTS

Here, XLOC_000647 expression was down-regulated in PC tissues and cell lines. The expression level of XLOC_000647 was significantly correlated to tumor stage, lymph node metastasis, and overall survival. Overexpression of XLOC_000647 attenuated cell proliferation, invasion, and EMT in vitro and impaired tumor growth in vivo. Further, a significantly negative correlation was observed between XLOC_000647 levels and its genomic nearby gene NLRP3 in vitro and in vivo. Moreover, XLOC_000647 decreased NLRP3 by inhibiting its promoter activity. Knockdown of NLRP3 decreased proliferation of cancer cells, invasion, and EMT in vitro. Importantly, after XLOC_000647 was overexpressed, the corresponding phenotypes of cells invasion and EMT were reversed by overexpression of NLRP3.

CONCLUSIONS

Together, these results indicate that XLOC_000647 functions as a novel tumor suppressor of lncRNA and acts as an important regulator of NLRP3, inhibiting cell proliferation, invasion, and EMT in PC.

MicroRNA-1291 targets the FOXA2-AGR2 pathway to suppress pancreatic cancer cell proliferation and tumorigenesis

Pancreatic cancer is the fourth leading cause of cancer death in the United States. Better understanding of pancreatic cancer biology may help identify new oncotargets towards more effective therapies. This study investigated the mechanistic actions of microRNA-1291 (miR-1291) in the suppression of pancreatic tumorigenesis. Our data showed that miR-1291 was downregulated in a set of clinical pancreatic carcinoma specimens and human pancreatic cancer cell lines. Restoration of miR-1291 expression inhibited pancreatic cancer cell proliferation, which was associated with cell cycle arrest and enhanced apoptosis. Furthermore, miR-1291 sharply suppressed the tumorigenicity of PANC-1 cells in mouse models. A proteomic profiling study revealed 32 proteins altered over 2-fold in miR-1291-expressing PANC-1 cells that could be assembled into multiple critical pathways for cancer. Among them anterior gradient 2 (AGR2) was reduced to the greatest degree. Through computational and experimental studies we further identified that forkhead box protein A2 (FOXA2), a transcription factor governing AGR2 expression, was a direct target of miR-1291. These results connect miR-1291 to the FOXA2-AGR2 regulatory pathway in the suppression of pancreatic cancer cell proliferation and tumorigenesis, providing new insight into the development of miRNA-based therapy to combat pancreatic cancer.

Extracellular Influences: Molecular Subclasses and the Microenvironment in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is the most prevalent form of pancreatic cancer and carries the worst prognosis of all common cancers. Five-year survival rates have not surpassed 6% for some decades and this lack of improvement in outcome urges a better understanding of the PDAC-specific features which contribute to this poor result. One of the most defining features of PDAC known to contribute to its progression is the abundance of non-tumor cells and material collectively known as the stroma. It is now well recognized that the different non-cancer cell types, signalling molecules, and mechanical properties within a tumor can have both tumor-promoting as well as –inhibitory effects. However, the net effect of this intratumour heterogeneity is not well understood. Heterogeneity in the stromal makeup between patients is even less well established. Such intertumour heterogeneity is likely to be affected by the relative contributions of individual stromal constituents, but how these contributions exactly relate to existing classifications that demarcate intertumour heterogeneity in PDAC is not fully known. In this review, we give an overview of the available evidence by delineating the elements of the PDAC stroma and their contribution to tumour growth. We do so by interpreting the heterogeneity at the gene expression level in PDAC, and how stromal elements contribute to, or interconnect, with this.

Induced Pluripotent Stem Cells and Induced Pluripotent Cancer Cells in Cancer Disease Modeling

In 2006, Noble Prize laureate Shinya Yamanaka discovered that a set of transcription factors can reprogram terminally differentiated somatic cells to a pluripotent stem cell state. Since then, induced pluripotent stem cells (iPSCs) have come into the public spotlight. Amidst a growing field of promising clinical uses of iPSCs in recent years, cancer disease modeling has emerged as a particularly promising and rapidly translatable application of iPSCs. Technological advances in genome editing over the past few years have facilitated increasingly rapid progress in generation of iPSCs with clearly defined genetic backgrounds to complement existing patient-derived models. Improved protocols for differentiation of iPSCs, engineered iPSCs and embryonic stem cells (ESCs) now permit the study of disease biology in the majority of somatic cell types. Here, we highlight current efforts to create patient-derived iPSC disease models to study various cancer types. We review the advantages and current challenges of using iPSCs in cancer disease modeling.

Fibroblast Growth Factor 10 in Pancreas Development and Pancreatic Cancer

The tenacious prevalence of human pancreatic diseases such as diabetes mellitus and adenocarcinoma has prompted huge research interest in better understanding of pancreatic organogenesis. The plethora of signaling pathways involved in pancreas development is activated in a highly coordinated manner to assure unmitigated development and morphogenesis in vertebrates. Therefore, a complex mesenchymal-epithelial signaling network has been implicated to play a pivotal role in organogenesis through its interactions with other germ layers, specifically the endoderm. The Fibroblast Growth Factor Receptor FGFR2-IIIb splicing isoform (FGFR2b) and its high affinity ligand Fibroblast Growth Factor 10 (FGF10) are expressed in the epithelium and mesenchyme, respectively, and therefore are well positioned to transmit mesenchymal to epithelial signaling. FGF10 is a typical paracrine FGF and chiefly mediates biological responses by activating FGFR2b with heparin/heparan sulfate (HS) as cofactor. A substantial number of studies using genetically engineered mouse models have demonstrated an essential role of FGF10 in the development of many organs and tissues including the pancreas. During mouse embryonic development, FGF10 signaling is crucial for epithelial cell proliferation, maintenance of progenitor cell fate and branching morphogenesis in the pancreas. FGF10 is also implicated in pancreatic cancer, and that overexpression of FGFR2b is associated with metastatic invasion. A thorough understanding of FGF10 signaling machinery and its crosstalk with other pathways in development and pathological states may provide novel opportunities for pancreatic cancer targeted therapy and regenerative medicine.

Multiplexed in vivo homology-directed repair and tumor barcoding enables parallel quantification of Kras variant oncogenicity

Large-scale genomic analyses of human cancers have cataloged somatic point mutations thought to initiate tumor development and sustain cancer growth. However, determining the functional significance of specific alterations remains a major bottleneck in our understanding of the genetic determinants of cancer. Here, we present a platform that integrates multiplexed AAV/Cas9-mediated homology-directed repair (HDR) with DNA barcoding and high-throughput sequencing to simultaneously investigate multiple genomic alterations in de novo cancers in mice. Using this approach, we introduce a barcoded library of non-synonymous mutations into hotspot codons 12 and 13 of Kras in adult somatic cells to initiate tumors in the lung, pancreas, and muscle. High-throughput sequencing of barcoded Kras HDR alleles from bulk lung and pancreas reveals surprising diversity in Kras variant oncogenicity. Rapid, cost-effective, and quantitative approaches to simultaneously investigate the function of precise genomic alterations in vivo will help uncover novel biological and clinically actionable insights into carcinogenesis.

High expression of diffuse panbronchiolitis critical region 1 gene promotes cell proliferation, migration and invasion in pancreatic ductal adenocarcinoma

Diffuse panbronchiolitis critical region 1 (DPCR1) is located in the major histocompatibility complex (MHC) class I. It was reported to be downregulated in invasive pituitary adenoma compared with that in non-invasive tumors, but upregulated in the precursor of gastric carcinogenesis. However, the direct effect of DPCR1 on cancer cells has rarely been reported, and the role DPCR1 in pancreatic ductal adenocarcinoma (PDAC) remains unclear. The clinical sample validation and public data analysis of the present study demonstrated that DPCR1 was upregulated markedly in PDAC and this high expression was negatively correlated with the patient prognosis. Functionally, knocking down DPCR1 in PDAC cell lines inhibited cell proliferation, migration and invasion in vitro. Tumor xenograft experiments further showed that suppression of DPCR1 inhibited tumor growth in vivo. In addition, the results of RNA deep sequencing and qRT-PCR assay showed that DPCR1 participated in PADC progression by regulating nuclear factor-kappa B signaling pathway, suggesting that it might be a novel oncogene in tumor progression and a potential therapeutic target in PDAC as well.

Complex roles of the stroma in the intrinsic resistance to gemcitabine in pancreatic cancer: where we are and where we are going

Pancreatic ductal adenocarcinoma (PDAC) is among the most devastating human malignancies. The poor clinical outcome in PDAC is partly attributed to a growth-permissive tumor microenvironment. In the PDAC microenvironment, the stroma is characterized by the development of extensive fibrosis, with stromal components outnumbering pancreatic cancer cells. Each of the components within the stroma has a distinct role in conferring chemoresistance to PDAC, and intrinsic chemoresistance has further worsened this pessimistic prognosis. The nucleoside analog gemcitabine (GEM) is usually the recommended first-line chemotherapeutic agent for PDAC patients and is given alone or in combination with other agents. The mechanisms of intrinsic resistance to GEM are an active area of ongoing research. This review highlights the important role the complex structure of stroma in PDAC plays in the intrinsic resistance to GEM and discusses whether antistroma therapy improves the efficacy of GEM. The addition of antistroma therapy combined with GEM is expected to be a novel therapeutic strategy with significant survival benefits for PDAC patients.

Pancreatic HIF2α Stabilization Leads to Chronic Pancreatitis and Predisposes to Mucinous Cystic Neoplasm

BACKGROUND & AIMS

Tissue hypoxia controls cell differentiation in the embryonic pancreas, and promotes tumor growth in pancreatic cancer. The cellular response to hypoxia is controlled by the hypoxia-inducible factor (HIF) proteins, including HIF2α. Previous studies of HIF action in the pancreas have relied on loss-of-function mouse models, and the effects of HIF2α expression in the pancreas have remained undefined.

METHODS

We developed several transgenic mouse models based on the expression of an oxygen-stable form of HIF2α, or indirect stabilization of HIF proteins though deletion of von Hippel-Lindau, thus preventing HIF degradation. Furthermore, we crossed both sets of animals into mice expressing oncogenic KrasG12D in the pancreas.

RESULTS

We show that HIF2α is not expressed in the normal human pancreas, however, it is up-regulated in human chronic pancreatitis. Deletion of von Hippel-Lindau or stabilization of HIF2α in mouse pancreata led to the development of chronic pancreatitis. Importantly, pancreatic HIF1α stabilization did not disrupt the pancreatic parenchyma, indicating that the chronic pancreatitis phenotype is specific to HIF2α. In the presence of oncogenic Kras, HIF2α stabilization drove the formation of cysts resembling mucinous cystic neoplasm (MCN) in humans. Mechanistically, we show that the pancreatitis phenotype is linked to expression of multiple inflammatory cytokines and activation of the unfolded protein response. Conversely, MCN formation is linked to activation of Wnt signaling, a feature of human MCN.

CONCLUSIONS

We show that pancreatic HIF2α stabilization disrupts pancreatic homeostasis, leading to chronic pancreatitis, and, in the context of oncogenic Kras, MCN formation. These findings provide new mouse models of both chronic pancreatitis and MCN, as well as illustrate the importance of hypoxia signaling in the pancreas.

Roles of autophagy and metabolism in pancreatic cancer cell adaptation to environmental challenges

Pancreatic ductal adenocarcinoma (PDAC) displays extensive and poorly vascularized desmoplastic stromal reaction, and therefore, pancreatic cancer (PaCa) cells are confronted with nutrient deprivation and hypoxia. Here, we investigate the roles of autophagy and metabolism in PaCa cell adaptation to environmental stresses, amino acid (AA) depletion, and hypoxia. It is known that in healthy cells, basal autophagy is at a low level, but it is greatly activated by environmental stresses. By contrast, we find that in PaCa cells, basal autophagic activity is relatively high, but AA depletion and hypoxia activate autophagy only weakly or not at all, due to their failure to inhibit mechanistic target of rapamycin. Basal, but not stress-induced, autophagy is necessary for PaCa cell proliferation, and AA supply is even more critical to maintain PaCa cell growth. To gain insight into the underlying mechanisms, we analyzed the effects of autophagy inhibition and AA depletion on PaCa cell metabolism. PaCa cells display mixed oxidative/glycolytic metabolism, with oxidative phosphorylation (OXPHOS) predominant. Both autophagy inhibition and AA depletion dramatically decreased OXPHOS; furthermore, pharmacologic inhibitors of OXPHOS suppressed PaCa cell proliferation. The data indicate that the maintenance of OXPHOS is a key mechanism through which autophagy and AA supply support PaCa cell growth. We find that the expression of oncogenic activation mutation in GTPase Kras markedly promotes basal autophagy and stimulates OXPHOS through an autophagy-dependent mechanism. The results suggest that approaches aimed to suppress OXPHOS, particularly through limiting AA supply, could be beneficial in treating PDAC.NEW & NOTEWORTHY Cancer cells in the highly desmoplastic pancreatic ductal adenocarcinoma confront nutrient [i.e., amino acids (AA)] deprivation and hypoxia, but how pancreatic cancer (PaCa) cells adapt to these conditions is poorly understood. This study provides evidence that the maintenance of mitochondrial function, in particular, oxidative phosphorylation (OXPHOS), is a key mechanism that supports PaCa cell growth, both in normal conditions and under the environmental stresses. OXPHOS in PaCa cells critically depends on autophagy and AA supply. Furthermore, the oncogenic activation mutation in GTPase Kras upregulates OXPHOS through an autophagy-dependent mechanism.

miR-92b-3p acts as a tumor suppressor by targeting Gabra3 in pancreatic cancer

BACKGROUND

MicroRNAs (miRNAs) can act as oncogenes or tumor suppressors by controlling cell proliferation, differentiation, metastasis and apoptosis, and miRNA dysregulation is involved in the development of pancreatic cancer (PC). Our previous study demonstrated that Gabra3 plays critical roles in cancer progression. However, whether Gabra3 is regulated by miRNAs in PC remains unknown.

METHODS

The expression levels of miR-92b-3p and Gabra3 were measured by quantitative PCR (qPCR), immunoblotting, in situ hybridization (ISH) and immunohistochemistry (IHC). The proliferation rate of PC cells was detected by MTS assay. Wound-healing and transwell assays were used to examine the invasive abilities of PC cells. Dual-luciferase reporter assays were used to determine how miR-92b-3p regulates Gabra3. Xenograft mouse models were used to assess the role of miR-92b-3p in PC tumor formation in vivo.

RESULTS

Here, we provide evidence that miR-92b-3p acted as a tumor suppressor in PC by regulating Gabra3 expression. MiR-92b-3p expression levels were lower in PC tissues than corresponding noncancerous pancreatic (CNP) tissues and were associated with a poor prognosis in PC patients. MiR-92b-3p overexpression suppressed the proliferation and invasion of PC cells in both in vivo and in vitro models. Conversely, miR-92b-3p knockdown induced an aggressive phenotype in PC cells. Mechanistically, miR-92b-3p overexpression suppressed Gabra3 expression, which then led to the inactivation of important oncogenic pathways, including the AKT/mTOR and JNK pathways.

CONCLUSION

Our results suggest that miR-92b-3p acted as a tumor suppressor by targeting Gabra3-associated oncogenic pathways; these results provide novel insight into future treatments for PC patients.

PDX1: A Unique Pancreatic Master Regulator Constantly Changes Its Functions during Embryonic Development and Progression of Pancreatic Cancer

Multifunctional activity of the PDX1 gene product is reviewed. The PDX1 protein is unique in that being expressed exclusively in the pancreas it exhibits various functional activities in this organ both during embryonic development and during induction and progression of pancreatic cancer. Hence, PDX1 belongs to the family of master regulators with multiple and often antagonistic functions.

KRAS, YAP, and obesity in pancreatic cancer: A signaling network with multiple loops

Pancreatic ductal adenocarcinoma (PDAC) continues to be a lethal disease with no efficacious treatment modalities. The incidence of PDAC is expected to increase, at least partially because of the obesity epidemic. Increased efforts to prevent or intercept this disease are clearly needed. Mutations in KRAS are initiating events in pancreatic carcinogenesis supported by genetically engineered mouse models of the disease. However, oncogenic KRAS is not entirely sufficient for the development of fully invasive PDAC. Additional genetic mutations and/or environmental, nutritional, and metabolic stressors, e.g. inflammation and obesity, are required for efficient PDAC formation with activation of KRAS downstream effectors. Multiple factors "upstream" of KRAS associated with obesity, including insulin resistance, inflammation, changes in gut microbiota and GI peptides, can enhance/modulate downstream signals. Multiple signaling networks and feedback loops "downstream" of KRAS have been described that respond to obesogenic diets. We propose that KRAS mutations potentiate a signaling network that is promoted by environmental factors. Specifically, we envisage that KRAS mutations increase the intensity and duration of the growth-promoting signaling network. As the transcriptional activator YAP plays a critical role in the network, we conclude that the rationale for targeting the network (at different points), e.g. with FDA approved drugs such as statins and metformin, is therefore compelling.

Duct- and Acinar-Derived Pancreatic Ductal Adenocarcinomas Show Distinct Tumor Progression and Marker Expression

The cell of origin of pancreatic ductal adenocarcinoma (PDAC) has been controversial. Here, we show that identical oncogenic drivers trigger PDAC originating from both ductal and acinar cells with similar histology but with distinct pathophysiology and marker expression dependent on cell of origin. Whereas acinar-derived tumors exhibited low AGR2 expression and were preceded by pancreatic intraepithelial neoplasias (PanINs), duct-derived tumors displayed high AGR2 and developed independently of a PanIN stage via non-mucinous lesions. Using orthotopic transplantation and chimera experiments, we demonstrate that PanIN-like lesions can be induced by PDAC as bystanders in adjacent healthy tissues, explaining the co-existence of mucinous and non-mucinous lesions and highlighting the need to distinguish between true precursor PanINs and PanIN-like bystander lesions. Our results suggest AGR2 as a tool to stratify PDAC according to cell of origin, highlight that not all PanIN-like lesions are precursors of PDAC, and add an alternative progression route to the current model of PDAC development.

SOX9 activity is induced by oncogenic Kras to affect MDC1 and MCMs expression in pancreatic cancer

SRY (sex determining region Y)-box 9 (SOX9) is required for oncogenic Kras-mediated acinar-to-ductal metaplasia (ADM), pancreatic intraepithelial neoplasias (PanINs) and ultimately pancreatic ductal adenocarcinoma (PDAC). However, how oncogenic Kras affects SOX9 activity is not yet understood, and SOX9-associated genes in PDAC are also unknown at all. Here, we investigated the mechanistic link between SOX9 and oncogenic Kras, studied biological function of SOX9, and identified SOX9-related genes and their clinical significance in patients with PDAC. Our studies reveal that oncogenic Kras induces SOX9 mRNA and protein expression as well as phosphorylated SOX9 expression in human pancreatic ductal progenitor cells (HPNE) and pancreatic ductal cells (HPDE). Moreover, oncogenic Kras promoted nuclear translocation and transcriptional activity of SOX9 in these cells. TAK1/IκBα/NF-κB pathway contributed to induction of SOX9 by oncogenic Kras, and SOX9 in turn enhanced NF-κB activation. SOX9 promoted the proliferation of HPNE and PDAC cells, and correlated with minichromosome maintenance complex components (MCMs) and mediator of DNA damage checkpoint 1 (MDC1) expression. The overexpressive MDC1 was associated with less perineural and lymph node invasion of tumors and early TNM-stage of patients. Our results indicate that oncogenic Kras induces constitutive activation of SOX9 in HPNE and HPDE cells, and Kras/TAK1/IκBα/NF-κB pathway and a positive feedback between SOX9 and NF-κB are involved in this inducing process. SOX9 accelerates proliferation of cells and affects MCMs and MDC1 expression. MDC1 is associated negatively with invasion and metastasis of PDAC.

Epithelial-Myeloid cell crosstalk regulates acinar cell plasticity and pancreatic remodeling in mice

Dedifferentiation of acini to duct-like cells occurs during the physiologic damage response in the pancreas, but this process can be co-opted by oncogenic Kras to drive carcinogenesis. Myeloid cells infiltrate the pancreas during the onset of pancreatic cancer, and promote carcinogenesis. Here, we show that the function of infiltrating myeloid cells is regulated by oncogenic Kras expressed in epithelial cells. In the presence of oncogenic Kras, myeloid cells promote acinar dedifferentiation and carcinogenesis. Upon inactivation of oncogenic Kras, myeloid cells promote re-differentiation of acinar cells, remodeling of the fibrotic stroma and tissue repair. Intriguingly, both aspects of myeloid cell activity depend, at least in part, on activation of EGFR/MAPK signaling, with different subsets of ligands and receptors in different target cells promoting carcinogenesis or repair, respectively. Thus, the cross-talk between epithelial cells and infiltrating myeloid cells determines the balance between tissue repair and carcinogenesis in the pancreas.

Lymph node metastases in resected pancreatic ductal adenocarcinoma: predictors of disease recurrence and survival

Background:

Few studies have simultaneously assessed the prognostic value of the multiple classification systems for lymph node (LN) metastases in resected pancreatic ductal adenocarcinoma (PDAC).

Methods:

In 600 patients with resected PDAC, we examined the association of LN parameters (AJCC 7th and 8th editions, LN ratio (LNR), and log odds of metastatic LN (LODDS)) with pattern of recurrence and patient survival using logistic regression and Cox proportional hazards regression, respectively. Regression models adjusted for age, sex, margin status, tumour grade, and perioperative therapy.

Results:

Lymph node metastases classified by AJCC 7th and 8th editions, LNR, and LODDS were associated with worse disease free-survival (DFS) and overall survival (OS) (all P_trend<0.01). American Joint Committee on Cancer 8th edition effectively predicted DFS and OS, while minimising model complexity. Lymph node metastases had weaker prognostic value in patients with positive margins and distal resections (both P_interaction<0.03). Lymph node metastases by AJCC 7th and 8th editions did not predict the likelihood of local disease as the first site of recurrence.

Conclusions:

American Joint Committee on Cancer 8th edition LN classification is an effective and practical tool to predict outcomes in patients with resected PDAC. However, the prognostic value of LN metastases is attenuated in patients with positive resection margins and distal pancreatectomies.

Fibroblast activation protein augments progression and metastasis of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinomas (PDAs) are desmoplastic and can undergo epithelial-to-mesenchymal transition to confer metastasis and chemoresistance. Studies have demonstrated that phenotypically and functionally distinct stromal cell populations exist in PDAs. Fibroblast activation protein-expressing (FAP-expressing) cells act to enhance PDA progression, while α-smooth muscle actin myofibroblasts can restrain PDA. Thus, identification of precise molecular targets that mediate the protumorigenic activity of FAP+ cells will guide development of therapy for PDA. Herein, we demonstrate that FAP overexpression in the tumor microenvironment correlates with poor overall and disease-free survival of PDA patients. Genetic deletion of FAP delayed onset of primary tumor and prolonged survival of mice in the KPC mouse model of PDA. While genetic deletion of FAP did not affect primary tumor weight in advanced disease, FAP deficiency increased tumor necrosis and impeded metastasis to multiple organs. Lineage-tracing studies unexpectedly showed that FAP is not only expressed by stromal cells, but can also be detected in a subset of CD90+ mesenchymal PDA cells, representing up to 20% of total intratumoral FAP+ cells. These data suggest that FAP may regulate PDA progression and metastasis in cell-autonomous and/or non-cell-autonomous fashions. Together, these data support pursuing FAP as a therapeutic target in PDA.