Proteomic Analysis of Pancreatic Ductal Adenocarcinoma Compared with Normal Adjacent Pancreatic Tissue and Pancreatic Benign Cystadenoma

Background: Dual expression of potential biomarkers in both benign and malignant pancreatic tumors was a major obstacle in the development of diagnostic biomarkers of early pancreatic cancer. Methods: To better understand the limitations of potential protein biomarkers in pancreatic cancer, we employed two-dimensional difference gel electrophoresis technology and tandem mass spectrometry to study protein expression profiles in pancreatic cancer tissues, benign pancreatic adenoma and normal adjacent pancreas. Seven differently expressed proteins were selected for validation by Western blot and/or immunohistochemistry. Results: 21 spots were overexpressed and 24 spots were downexpressed in pancreatic cancer compared with benign and normal adjacent tissues. Our study demonstrated that three candidate pancreatic ductal adenocarcinoma biomarkers identified in previous studies, fructose-bisphosphate aldolase A, α-smooth muscle actin and vimentin, were also overexpressed in pancreatic cystadenoma, which might lower their further utility as biomarkers for pancreatic cancer. Aflatoxin B₁ aldehyde reductase (AKR7A2) was confirmed to be only highly expressed in pancreatic cancer, not in normal adjacent pancreas and benign tumors. Conclusions: The protein profile pattern of pancreatic cystadenoma was more similar to normal adjacent pancreas than pancreatic cancer. We identified panels of the upregulated proteins in pancreatic cancer, which have not been reported in prior proteomic studies. AKR7A2 may be a novel potential biomarker for pancreatic cancer.     

Inhibition of Ankyrin-B Expression Reduces Growth and Invasion of Human Pancreatic Ductal Adenocarcinoma

Background: In spite of the increasing knowledge of the molecular pathology of pancreatic ductal adenocarcinoma (PDAC), treatment of this tumor still remains an unresolved problem. Thus, the identification of ‘novel’ genes involved in pancreatic tumor progression is essential for early diagnosis and new treatment regimens of PDAC. Ankyrin-B (ANK2) was identified as being overexpressed in PDAC in a previous study by our group. ANK2 overexpression has been described in several tumors; however, the function of ANK2 in pancreatic carcinoma has not been elucidated. Materials and Methods: In the present study, we confirmed ANK2 overexpression in PDAC and analyzed the effects of ANK2 knockdown in the pancreatic tumor cell line PANC-1. Results: ANK2 silencing reduced the activity of FAK, ERK1/2 and p38. Decreased ANK2 expression restrained migration and invasive potential of PANC-1 cells. Moreover, silencing of ANK2 decreased the proliferation of the pancreatic tumor cells and reduced their tumorigenicity in vitro and in vivo. Conclusion: Our results demonstrate that silencing of ANK2 expression reduced the malignant phenotype of pancreatic cancer cells, indicating that ANK2 represents a potential target for therapy of pancreatic cancer.     

Synergistic activity of gamma-linolenic acid and cytotoxic drugs against pancreatic adenocarcinoma cell lines

Background: γ-Linolenic acid (GLA) is growth inhibitory both in vitro and in vivo, at doses non-toxic to non-cancer cells. Chemotherapeutic agents have limited activity in pancreatic cancer. Interactions between GLA and cytotoxic drugs have not previously been investigated; any synergy might improve the therapeutic effect of these agents. Aim: To investigate possible interactions between GLA and 5-fluorouracil (5-FU) or gemcitabine against pancreatic cancer cell lines in vitro. Methods: Two pancreatic cancer cell lines were exposed to GLA alone and in combination with 5-FU or gemcitabine. Residual viable biomass was measured using the MTT assay and the results analysed by the median effect method of Chou and Talalay [Adv Enzyme Regul 1984;22:27–55]. Results: GLA concentrations of 3.9–125 µg/ml had a synergistic or additive growth inhibitory effect on all tested concentrations of gemcitabine. Synergism was demonstrated between GLA and 5-FU only at concentrations of 62.5–125 µg/ml of 5-FU. Conclusion: GLA has a synergistic effect with gemcitabine at concentrations that correspond to in vivo therapeutic doses. GLA with 5-FU is synergistic only at a tight range of high concentrations of 5-FU. GLA lacks toxic side effects and may be useful in combination with gemcitabine.     

A clinically relevant model of human pancreatic adenocarcinoma identifies patterns of metastasis associated with alterations of the TGF-beta/Smad4 signaling pathway

Genetic alterations impacting the TGF-β/Smad4 pathway are found in nearly all pancreatic adenocarcinomas, and recent reports have identified a relationship between DPC4/Smad4 expression and patient survival. In this study we use a clinically relevant animal model of pancreatic cancer to examine the impact of these genetic changes on the biology of pancreatic cancer. Methods: Using high-density oligonucleotide DNA microarray technology, a comprehensive examination of the components of the TGF-β/Smad4 pathway was performed on three human pancreatic adenocarcinoma cell lines. The in vitro and in vivo growth characteristics of these cell lines was then compared. Finally, using a clinically relevant orthotopic xenograft model of pancreatic cancer, primary tumor growth and metastases were measured for pancreatic tumors derived from each cell line. Results: Examination of the TGF-β/Smad4 pathway components identified that these three cell lines possess molecular profiles consistent with ∼90% of pancreatic adenocarcinoma tumors in patients. A significant discrepancy between in vitro and in vivo growth characteristics of each cell line was identified. When tumors from each cell line were established in nu/nu mice, each cell line exhibited distinct metastatic profiles. Data from these studies is consistent, with clinical observations concerning DPC4/Smad4 and patient outcome. Conclusion: Using an orthotopic model of tumor growth and metastasis identifies distinct metastatic profiles associated with molecular alterations of the TGF-β/Smad4 pathway and provides insight with regard to the biologic consequences of these changes.     

Enhanced ENA-78 and IL-8 Expression in Patients with Malignant Pancreatic Diseases

Background/Aim: Pancreatic cancer is characterized by perineural invasion, early lymph node and liver metastases, and an extremely dismal prognosis. In the present study we aimed at investigating the expression profile of pro-inflammatory and angiogenic CXC chemokines as potential factors contributing to the aggressive biology of this gastrointestinal malignancy. Methods: Protein expression profiles of the CXC chemokines growth-related oncogene alpha (GRO-α/ CXCL1), epithelial cell-derived neutrophil-activating peptide-78 (ENA-78/CXCL5), granulocyte chemoattractant protein-2 (GCP-2/CXCL6), neutrophil-activating protein-2 (NAP-2/CXCL7), and interleukin-8 (IL-8/CXCL8) were assessed by enzyme-linked immunosorbent assay in pancreatic carcinoma, cancer of the papilla of Vater, pancreatic cystadenoma, and chronic pancreatitis specimens. Results: IL-8 and ENA-78 protein expression was most pronounced in pancreatic carcinoma specimens, showing an 11-fold and 17-fold over-expression in comparison with non-affected neighbouring tissues, a 66-fold and 24-fold upregulation compared to pancreatic cystadenoma, and a 6-fold and 9-fold overex-pression with respect to chronic pancreatitis, respectively (p <0.05 between all groups). In addition, a close correlation between IL-8 and ENA-78 protein expression and advanced pancreatic carcinomas in relation to the T category was evident (p < 0.05). Conclusion: Our results demonstrate that ELR+ CXC chemokines are differentially expressed in malignant and non-malignant human pancreatic specimens, suggesting a potential contribution of these chemokines to the pathogenesis of pancreatic carcinoma.     

Pancreatic Stellate Cells Increase the Invasion of Human Pancreatic Cancer Cells through the Stromal Cell-Derived Factor-1/CXCR4 Axis

Aim: Both pancreatic stellate cells (PSCs) and the stromal cell-derived factor-1(SDF-1)/CXCR4 receptor ligand system have important roles in pancreatic cancer progression. This study set out to detect if PSCs express SDF-1 and promote the invasion of pancreatic cancer through the SDF-1/CXCR4 receptor ligand axis. Methods: RT-PCR was performed to detect the expression of SDF-1 and CXCR4 in PSCs, pancreatic cancer lines and cancer tissue samples. ELISA was used to investigate the concentration of SDF-1 in PSC supernatants. An MTT assay was applied to detect the proliferation of pancreatic cancer cells. A transwell chamber migration assay was employed to detect the migration of AsPC-1 cells. An in vitro invasion assay was used to detect the invasion of AsPC-1 cells. Results: CXCR4 expression was detected in PSCs; AsPC-1, SW1990 and BxPC-3 cancer cells; and cancer tissues. SDF-1 was detected in PSCs and cancer tissues, but not in AsPC-1, SW1990 and BxPC-3 cells. SDF-1α protein was found in PSC supernatants. PSC-conditioned media can promote the proliferation, migration and invasion of pancreatic cancer cells. SDF-1 neutralizing antibody or AMD3100 can significantly inhibit these promotive effects. Conclusion: PSCs can secrete SDF-1 and increase the invasion of pancreatic cancer cells through the SDF-1/CXCR4 axis.     

Treatment with 5-fluorouracil enhances radiosensitivity of the human pancreatic cancer cell line MiaPaCa-2

Background and Purpose: Several clinical studies have suggested that the combination of radiation therapy and 5-fluorouracil (5-FU) may improve outcome of patients with pancreatic cancer. However, there are few experimental studies supporting this treatment. Aim of the Study: To examine the radiosensitivity of human pancreatic cancer cells and its modulation by 5-FU. Material and Methods: MiaPaCa-2, PANC-1 and NP-18 cells growing as monolayer culture were treated with radiation and 5-FU. In addition, 5-FU was studied administered either pre- or postradiation, both as pulse or continuous exposure. Cell survival was determined by the in vitro clonogenic assay. Results: In MiaPaCa-2 cell line, both radiation and 5-FU alone reduced cell survival. The addition of 5-FU to radiation caused a significant net decrease of cell survival. Pulse exposure of 5-FU decreased survival after 2 Gy and mean inactivation dose by 1.64; continuous exposure decreased survival after 2 Gy and mean inactivation dose by about 2.4. Timing of 5-FU exposure did not modify survival. However, when adjusting for 5-FU killing effect and cell multiplicity, only continuous exposure significantly enhanced radiation cell killing. Conclusion: Both pulse and continuous exposure increase radiation cell killing, but only continuous exposure may radiosensitize MiaPaCa-2 cells.     

Identification of Genomic Alterations Associated with the Aggressiveness of Pancreatic Cancer Using an Ultra-High-Resolution CGH Array

Background: Genomic alterations present in pancreatic adenocarcinoma have been described only partially. In addition, the relations between these alterations and the aggressiveness of the phenotype remain unknown. Methods: Genomic DNA and total RNA from 5 pancreatic cell lines, of which 2 have an aggressive phenotype and are gemcitabine-resistant (Mia-Paca2 and Panc-1), and 3 less aggressive and gemcitabine-sensitive (Capan-1, Capan-2 and BxPC3), have been purified. DNA abnormalities have been analyzed using an ultra-high-resolution CGH array and mRNA expression was studied with an Affymetrix GeneChip expression array. Results: We identified 573 amplified and 30 deleted genes common to all 5 cell lines. Some of them have already been described, whereas other genes, implicated in signal transduction, apoptosis, cell cycle or cell migration, are described for the first time as being related to this cancer. Comparison of genomic abnormalities between the 2 most aggressive and the 3 less aggressive cell lines led to the identification of 368 genes specifically amplified in the aggressive cell lines. However, no specific gene deletion seems to be associated with the aggressive phenotype. Conclusion: Using a high-resolution approach, we could precisely describe the genomic alterations associated with pancreatic adenocarcinoma and determine those associated with an aggressive phenotype.     

Expression and Clinical Significance of CacyBP/SIP in Pancreatic Cancer

Aims: Calcyclin-binding protein or Siah-1-interacting protein (CacyBP/SIP), a component of the ubiquitin-mediated proteolysis, could bind SKP1-CUL1-F box protein complex and participate in beta-catenin degradation, which was found to be related to the malignant phenotypes of gastric cancer and renal cancer. However, the role of CacyBP/SIP in pancreatic cancer progression still remains unclear. Therefore, the aim of the present study was to investigate the expression and clinical significance of CacyBP/SIP in pancreatic cancer. Methods: Immunohistochemistry was carried out on paraffin-embedded sections of pancreatic cancer and normal pancreatic tissues. In addition, Western blot and semiquantitative RT-PCR were carried out to analyze mRNA and protein expression of CacyBP/SIP in 8 pairs of freshly resected pancreatic cancer and their adjacent nontumorous tissue. Results: CacyBP/SIP expression was significantly increased in pancreatic cancer tissue (28/68 or 41.2%) and correlated with differentiation degree, higher TNM (tumor, node, metastasis) stage and distance metastasis. Also, mRNA and protein expression of CacyBP/SIP were found to be at higher levels in almost all cancer tissues compared to adjacent tissues. Conclusions: CacyBP/SIP protein might play an important role in the process of pancreatic carcinogenesis and high-level CacyBP/SIP expression might be related to the malignant potential of pancreatic cancer.     

ATP-Binding Cassette C Transporters in Human Pancreatic Carcinoma Cell Lines: Upregulation in 5-Fluorouracil-Resistant Cells

Background: Pancreatic cancer is characterized by high resistance to chemotherapy. Such chemoresistance can be mediated by multidrug resistance proteins (MRPs), breast cancer resistance protein (BCRP), and MDR1 P-glycoprotein. However, the contribution of individual MRP isoforms to chemoresistance in pancreatic carcinoma is unclear. We studied ATP-binding cassette (ABC) transporter expression in human pancreatic carcinoma cell lines as compared to primary pancreatic duct cells, and analyzed the MRP expression profile in 5-fluorouracil-resistant cells. Methods: Transporter expression was analyzed by quantitative and qualitative RT-PCR, by immunoblot, and chemoresistance by cytotoxicity assay. Results: Primary pancreatic duct cells expressed MRP1, MRP3, MRP4, and MRP5, but not MRP2 mRNA. The established carcinoma cell lines expressed MRP1, MRP4, and MRP5, most of them also MRP2, MRP3, MRP7, and BCRP, but none contained detectable amounts of MRP6, MRP8, or MRP9 mRNA. Immunoblot analyses demonstrated presence of MRP1, MRP4, and MRP5 protein in all, but MRP3 and BCRP protein only in some of these cells. Compared to parental Capan-1 cells, Capan-1 cells with acquired chemoresistance towards 5-fluorouracil showed an upregulated mRNA and protein expression of MRP3, MRP4, and MRP5. In addition, silencing of MRP5 by RNA interference resulted in enhanced sensitivity of parental Capan-1 cells towards 5-fluorouracil cytotoxicity. Conclusion: MRP3, MRP4, and MRP5 are upregulated in 5-fluorouracil-resistant cells, and MRP5 contributes to 5-FU resistance in pancreatic carcinoma cells.     

Pancreatic cancer cells show lower oleic acid oxidation and their conditioned medium inhibits oleic acid oxidation in human myotubes

Background/Objectives: We aimed to metabolically compare healthy primary human pancreatic epithelial cells (hPEC) to a pancreatic cancer cell line (PANC-1) and explore the effect on energy metabolism of exposing primary human myotubes to conditioned medium from hPEC and PANC-1 cells.MethodsDifferences in metabolism were examined with radiolabeled glucose, oleic acid and lactic acid, and by qPCR. Mass spectrometry-based proteomics was used to study global protein secretion from the two cell types. Pathway analyses were performed.ResultsPANC-1 cells tended to have higher glucose uptake, production of lactic acid, and glucose oxidation compared to hPEC cells. PANC-1 cells had higher uptake but lower oxidation of oleic acid, and mitochondrial reserve capacity from oleic acid was lower in PANC-1 cells. These differences in energy metabolism were reflected by differences in gene expressions and pathway analyses of the secretome. Conditioned medium from PANC-1 cells attenuated oleic acid oxidation in primary human myotubes.ConclusionsMetabolic characterization of the PANC-1 cells revealed a glycolytic phenotype since they had an active glucose oxidation. Furthermore, PANC-1 cells showed a lower oleic acid oxidation and secreted a high amount of proteins into conditioned medium that also induced a reduced oleic acid oxidation in myotubes.     

Ukrain Affects Pancreas Cancer Cell Phenotype in vitro by Targeting MMP-9 and Intra-/Extracellular SPARC Expression

Background/Aims: We investigated whether the anticancer drug Ukrain (UK) is able to modulate the expression of some of the key markers of tumor progression in pancreatic cell carcinoma, in order to assess its potential therapeutic effect. Methods: Three cell lines (HPAF-II, PL45,HPAC) were treated with UK (5,10 and 20 μM) for 48 h, or left untreated. Secreted protein acidic and rich in cysteine (SPARC) mRNA levels were assessed by real-time PCR. Matrix metalloproteinases (MMP)-2 and -9 activity was analyzed by SDS zymography; SPARC protein levels in cell lysates and supernatants were determined by Western blot. Cell cycle was determined by flow cytometric analysis, and invasion by matrigel invasion assay. Results: UK down-regulated MMP-2 and MMP-9, suggesting that UK may decrease pancreatic cancer cell invasion, as confirmed by the matrigel invasion assay. SPARC protein down-regulation in supernatants points to an inhibition by UK of extracellular matrix remodeling in the tumor microenvironment. At the same time, SPARC mRNA and cellular protein level up-regulation suggests that UKcan affect cell proliferation by cell cycle inhibition, showing a cell cycle G2/M arrest in UK-treated cells. Conclusion: Our results suggest that UK modulates two major aspects involved in tumorigenesis of pancreatic cancer cells, such as extracellular matrix remodeling and cell proliferation.     

Gemcitabine Induces the VMP1 -Mediated Autophagy Pathway to Promote Apoptotic Death in Human Pancreatic Cancer Cells

Background/Aim: Autophagy is a degradation process of cytoplasmic cellular constituents. We have described the vacuole membrane protein-1 (VMP1) whose expression triggers autophagy in mammalian cells. The aim of this study was to analyze the role of autophagy in human pancreatic cancer cell death. Methods/Results: Here we show that gemcitabine, the standard chemotherapy for pancreatic cancer, induced autophagy in PANC-1 and MIAPaCa-2 cells, as evidenced by the accumulation of acidic vesicular organelles, the recruitment of microtubule-associated protein-1 light chain-3, and electron microscopy. In addition, gemcitabine treatment induced early expression of VMP1 in cancer cells. Gemcitabine also induced apoptosis detected by morphology, annexin V-positive cells, and cleavage of caspase-3. Surprisingly, 3-methyladenine, an autophagy inhibitor, decreased apoptosis in gemcitabine-treated cells, showing that autophagy leads to cancer cell apoptotic death. Finally, VMP1 knockdown decreased autophagy and apoptosis in gemcitabine-treated cancer cells. Conclusions: The VMP1-autophagy pathway promotes apoptosis in pancreatic cancer cells and mediates gemcitabine-induced cytotoxicity.     

Influence of Cell Cycle Checkpoints and p53 Function on the Toxicity of Temozolomide in Human Pancreatic Cancer Cells

Background: Though an increased efficacy of carmustine and temozolomide (TMZ) has been demonstrated by inactivation of O⁶-methylguanine-DNAmethyltransferase(MGMT) with O⁶-benzyl-guanine (BG) in human pancreatic tumors refractive to alkylating agents, the regulatory mechanisms have not been explored. Methods: The effects of TMZ and BG on apoptosis, cell growth, the mitotic index, cell cycle distribution, and protein expression were studied byTUNEL, cell counting, flow cytometry, and Western blot analysis, respectively. Results: The wt-p53 human pancreatic tumor cell line Capan-2 and p53-efficient mouse embryonic fibroblasts (MEFs) were more responsive to treatment with TMZ + BG than mutant p53 Capan-1 and p53-null MEFs. S phase delay with a subsequent G2/M arrest was observed in Capans in response to BG + TMZ. The G1-to-S transition delay in Capan-2 was associated with p53-dependent apoptosis and was distinctly different from the presumed mismatch repair (MMR) killing operative during the G2/M arrest. The effect of p53on BG +TMZ toxicity was supported by a marked change in apoptosis when p53 function was restored/inactivated. There was an early induction of MMR proteins in p53-efficient lines. Conclusion: p53 provokes a classic proapoptotic response by delaying G1-to-S progression, but it may also facilitate cell killing by enhancing MMR-related cell cycle arrest and cell death.     

Altered glucose metabolism and proteolysis in pancreatic cancer cell conditioned myoblasts: searching for a gene expression pattern with a microarray analysis of 5000 skeletal muscle genes

BACKGROUND AND AIMS: We verified whether conditioned media (CM) from pancreatic cancer cell lines (MIAPaCa2, CAPAN-1, PANC-1, BxPC3) alter glucose metabolism and gene expression profiles (microarray experiment with a platform of 5000 skeletal muscle cDNA) in mice myoblasts. METHODS: Myoblasts were incubated with control or pancreatic cancer CM for 24 and 48 hours. RESULTS: Lactate significantly increased in CM compared with non-conditioned myoblasts. No variations in expression levels of the main genes involved in glycolysis were found in CM myoblasts. Propionyl coenzyme A carboxylase and isocitrate dehydrogenase 3 beta genes, which encode enzymes of the tricarboxylic acid cycle, were overexpressed, while IGFIIR and VAMP5 genes were underexpressed in CM myoblasts. PAFAH1B1 and BCL-2 genes (intracellular signal transduction) and the serine protease cathepsin G (proteolysis), were overexpressed in CM myoblasts. Tyrosine accumulation in CM myoblasts suggested that proteolysis overcomes protein synthesis. Sorcin, actin alpha, troponin T1, and filamin A were underexpressed in CM myoblasts. CONCLUSIONS: Our findings demonstrate that pancreatic cancer cell conditioned media enhanced lactate production and induced proteolysis, possibly by altering expression levels of a large number of genes, not only those involved in protein biosynthesis and degradation or glucose metabolism, but also those involved in the tricarboxylic acid cycle and in vesicle traffic.     

Caffeic Acid Phenethyl Ester Induces Apoptosis of Human Pancreatic Cancer Cells Involving Caspase and Mitochondrial Dysfunction

Aims: This study aimed to investigate the effect of caffeic acid phenethyl ester (CAPE), an active component isolated from honeybee propolis, in inducing apoptosis in human pancreatic cancer cells. Methods: Inhibition of viability of BxPC-3 and PANC-1 cell lines induced by CAPE was estimated by a trypan blue dye exclusion test. The type of cell death in BxPC-3 after CAPE treatment was characterized by observation of morphology, sub-GI DNA content, annexin-V/PI staining, caspase-3 and caspase-7 assay, and DNA agarose gel electrophoresis. Results: CAPE (10 μg/ml) resulted in marked inhibition of viability of BxPC-3 (80.4 ± 4.1%) and PANC-1 (74.3 ± 2.9%) cells. CAPE induced a time-dependent increase in hypodiploid percentage and a significant decrease in mitochondrial transmembrane potential in BxPC-3 cells. It induced morphological changes of typical apoptosis, but no DNA fragmentation was noted by DNA electrophoresis. The inhibition of growth and increased in the proportion of sub-G₁ cells was partially blocked by pretreatment with the pan-caspase inhibitor Z-VAD-fmk (50 μM) in BxPC-3 cells indicating a caspase-related mechanism in CAPE-induced apoptosis. Caspase-3/caspase-7 activity was approximately 2 times greater in CAPE-treated BxPC-3 cells compared with control cells. Conclusions: These results suggest that CAPE is a potent apoptosis-inducing agent. Its action is accompanied by mitochondrial dysfunction and activation of caspase-3/caSpase-7.