Culture of human main pancreatic duct epithelial cells

The long coding RNA AFAP1-AS1 promotes tumor cell growth and invasion in pancreatic cancer through upregulating the IGF1R oncogene via sequestration of miR-133a

Long non-coding RNAs (lncRNAs) have been shown to play a significant role in the progression of many cancers, including pancreatic cancer (PC). However, the biological function and regulatory mechanisms of lncRNAs in PC remains largely unclear. The aim of this study was to identify and evaluate the potential functions of lncRNAs in PC and reveal the underlying mechanisms of their effects. Screening of published microarray data (GEO accession Nos. GSE16515 and GSE32688), revealed lncRNA AFAP1-AS1 to be one of the most upregulated lncRNAs in PC tissues. High expression of AFAP1-AS1 was correlated with advanced stages, tumor size and lymph node metastasis, as well as with poorer overall survival in patients with PC. Functionally, knockdown of AFAP1-AS1 by transfection with siRNA inhibited the proliferative and invasive capacities of PaCa-2 and SW1990 PC cells, promoted apoptosis of PC cells in vitro, and impaired in-vivo tumorigenicity. In particular, it was hypothesized that AFAP1-AS1 may act as a competitive endogenous RNA (ceRNA), effectively becoming a sink for miR-133a whose expression was found to be downregulated in PC tissues and cell lines, and which was negatively correlated with the expression of AFAP1-AS1. We also found that the IGF1R oncogene which is an important regulator of MEK/ERK signaling pathway, was positively regulated by AFAP1-AS1 through ameliorating miR-133a-mediated IGF1R repression in PC tissues. Moreover, we demonstrated that knockdown of IGF1R by transfection with si-IGF1R suppressed cell proliferation, invasion and migration of PaCa-2 and SW1990 PC cells, suggesting that IGF1R may function as an oncogene in PC cells. Further investigations revealed that miR-133a reversed the biological effects of AFAP1-AS1 on PC cells. Collectively, the findings provide new evidence that AFAP1-AS1 could regulate the progression of pancreatic cancer by acting as a ceRNA, and suggest it has potential for use as both a biomarker for the early detection PC and for the development of individualized therapies for PC.

Biphenotypic Differentiation of Pancreatic Cancer in 3-Dimensional Culture

OBJECTIVE

Pancreatic ductal adenocarcinoma (PDAC) is the third most common cause of cancer death in the United States. Improved characterized models of PDAC are needed for drug screening.

METHODS

We grew 4 established pancreatic cancer cell lines in hanging drop cultures to produce spheroids. We also grew organoids from explanted xenografted PDAC and surgically resected primary PDAC. We performed transmission and scanning electron microscopy and compared findings with those of the normal pancreatic duct. We also performed single-cell cloning to determine the potential options for differentiation.

RESULTS

Spheroids contained tight junctions and desmosomes but lacked zymogen granules, as expected. The former features were present in normal pancreatic duct but absent from PDAC cell lines grown in standard 2-dimensional culture. Spheroids functionally excluded macromolecules in whole mounts. Cells on the surface of PDAC spheroids were carpeted by microvilli except for rare cells with prominent stereocilia. Carpets of microvilli were also seen in low passage organoids produced from xenografts and surgically resected human PDAC, in addition to normal human pancreatic duct. We performed single-cell cloning and resulting spheroids produced both cell phenotypes at the same approximate ratios as those from bulk cultures.

CONCLUSIONS

Pancreatic cancer spheroids/organoids are capable of biphenotypic differentiation.

MicroRNA-323-3p inhibits cell invasion and metastasis in pancreatic ductal adenocarcinoma via direct suppression of SMAD2 and SMAD3

Pancreatic ductal adenocarcinoma (PDAC), which accounts for 96% of all pancreatic cancer cases, is characterized by rapid progression, invasion and metastasis. Transforming growth factor-beta (TGF-β) signaling is an essential pathway in metastatic progression and microRNAs (miRNA) play central roles in the regulation of various biological and pathologic processes including cancer metastasis. However, the molecular mechanisms involved in regulation of miRNAs and activation of TGF-β signaling in PDAC remain to be established. The results of this study suggested that miR-323-3p expression in PDAC tissues and cell lines was significantly decreased compared to levels in normal pancreatic tissues and primary cultured pancreatic duct epithelial cells. Further investigation revealed that miR-323-3p directly targeted and suppressed SMAD2 and SMAD3, both key components in TGF-β signaling. Lower levels of miR-323-3p predicted poorer prognosis in patients with PDAC. Ectopic overexpression of miR-323-3p significantly inhibited, while silencing of miR-323-3p increased the migration and invasion abilities of PDAC cells in vitro. Moreover, using an in vivo mouse model, we demonstrated that overexpressing of miR-323-3p significantly reduced, while knockdown of miR-323-3p enhanced lung metastatic colonization of PANC-1 cells. Furthermore, miR-323-3p-induced TGF-b signaling inhibition and cell motility suppression were partially rescued by overexpressing of Smad2 and Smad3 in PDAC cells. Our findings suggest that re-expression of miR-323-3p might offer a novel therapeutic target against metastasis in patients with PDAC.

MiR-1181 inhibits stem cell-like phenotypes and suppresses SOX2 and STAT3 in human pancreatic cancer

Recent studies have shown that cancer stem cells (CSCs) play an important role in the development of pancreatic cancer. Multiple oncogenes and signaling pathways have been confirmed to participate in the stemness maintenance and tumorigenicity of CSCs, including sex-determining region Y-box 2 (SOX2) and signal transduction and activation of transcription 3 (STAT3), which may provide novel therapeutic targets on pancreatic cancer. Here, we reported in pancreatic cancer tissues and cells that miR-1181 expression was markedly downregulated, and the low miR-1181 expression was associated with poorer overall survival and disease-free survival in pancreatic cancer patients. Furthermore, overexpression of miR-1181 inhibited, whereas downregulation of miR-1181 promoted, CSCs-like phenotypes in vitro and tumorigenicity in vivo in pancreatic cancer cells. Moreover, we demonstrated that miR-1181 directly suppressed SOX2 and STAT3 expression, resulting in downregulation of SOX2 and inhibition of the STAT3 pathway. Hence, our results suggest that miR-1181 plays a vital role in inhibiting the CSCs-like phenotypes in pancreatic cancer and might represent a potential target for anti-pancreatic cancer.

In vitro models of pancreatic cancer for translational oncology research

BACKGROUND: Pancreatic cancer is a disease of near uniform fatality and the overwhelming majority of patients succumb to their advanced malignancy within a few months of diagnosis. Despite considerable advances in our understanding of molecular mechanisms underlying pancreatic carcinogenesis, this knowledge has not yet been fully translated into clinically available treatment strategies that yield significant improvements in disease free or overall survival. OBJECTIVE: Cell line-based in vitro model systems provide powerful tools to identify potential molecular targets for therapeutic intervention as well as for initial pre-clinical evaluation of novel drug candidates. Here we provide a brief overview of recent literature on cell line-based model systems of pancreatic cancer and their application in the search for novel therapeutics against this vicious disease. CONCLUSION: While in vitro models of pancreatic cancer are of tremendous value for genetic studies and initial functional screenings in drug discovery, they carry several imanent drawbacks and are often poor in predicting therapeutic response in humans. Therefore, in most instances they are successfully exploited to generate hypothesis and identify molecular targets for novel therapeutics, which are subsequently subject to further in-depth characterization using more advanced in vivo model systems and clinical trials.

Gene expression patterns in pancreatic tumors, cells and tissues

Background

Cancers of the pancreas originate from both the endocrine and exocrine elements of the organ, and represent a major cause of cancer-related death. This study provides a comprehensive assessment of gene expression for pancreatic tumors, the normal pancreas, and nonneoplastic pancreatic disease.

Methods/Results

DNA microarrays were used to assess the gene expression for surgically derived pancreatic adenocarcinomas, islet cell tumors, and mesenchymal tumors. The addition of normal pancreata, isolated islets, isolated pancreatic ducts, and pancreatic adenocarcinoma cell lines enhanced subsequent analysis by increasing the diversity in gene expression profiles obtained. Exocrine, endocrine, and mesenchymal tumors displayed unique gene expression profiles. Similarities in gene expression support the pancreatic duct as the origin of adenocarcinomas. In addition, genes highly expressed in other cancers and associated with specific signal transduction pathways were also found in pancreatic tumors.

Conclusion

The scope of the present work was enhanced by the inclusion of publicly available datasets that encompass a wide spectrum of human tissues and enabled the identification of candidate genes that may serve diagnostic and therapeutic goals.

Stimulation of human colonic epithelial cells by leukemia inhibitory factor is dependent on collagen-embedded fibroblasts in organotypic culture

The colonic epithelium undergoes a continuous cycle of proliferation, differentiation, and apoptosis. To characterize factors important for colonic homeostasis and its dysregulation, human fetal colonic epithelial cells were isolated and seeded on a collagen type I matrix with embedded colonic fibroblasts. The epithelial cells rapidly spread from clusters and proliferated, and within 3 days, a columnar layer of polarized epithelium surrounded the surface of the constricted collagen matrix. The polarized enterocytes developed brush borders, tight junctions and desmosomes, and goblet and enteroendocrine cells were present. A balance of growth and differentiation was maintained for several weeks in the presence of collagen-embedded fibroblasts and a complex mixture of growth factors. Leukemia inhibitory factor (LIF) was critical for proliferation of enterocytes and inhibited expression of the differentiation marker carbonic anhydrase II. In the presence of LIF, the relative number of goblet cells remained stable, whereas enteroendocrine relative cell number declined. LIF-stimulated epithelial cells remained dependent on the presence of fibroblasts in the matrix. In combination with stem cell factor and endothelin 3, LIF induced formation of disorganized structures of stratified and semi-stratified cells, suggesting that the homeostatic balance in the normal human colon requires cooperation with differentiation-inducing factors.

Angiotensin II evokes calcium-mediated signaling events in isolated dog pancreatic epithelial cells

INTRODUCTION

Calcium-activated chloride conductance has been identified in normal pancreatic duct cells. Recent in vitro evidence suggests that angiotensin II (AngII) stimulates pancreatic secretion in both cystic fibrosis (CFPAC) and transformed pancreatic cells.

AIMS

To investigate calcium-mediated stimulatory effects of AngII in both nontransformed dog pancreatic duct epithelial (DPDE) and CFPAC cells.

METHODS

Western blots were performed in both cells seeking AngII receptors. In additional studies, DPDE and CFPAC cells were grown on vitrogen-coated glass cover slips and loaded with Indo-1-AM dye. Cells were placed in a confocal microscope's perfusion chamber and perfused with 100 microM AngII or ATP (control). Cells were excited with UV light, and intracellular calcium ([Ca+2]i) was read using fluorescence emission at 405 and 530 nm. Finally, single channels in the DPDE cells were examined using cell-attached patch clamps. Current amplitude histograms provided estimates of the conductance and open probability of channels.

RESULTS

Western blots demonstrated presence of both AT and AT AngII receptors in DPDE and CFPAC cells; the density of AT receptors appeared lower than that of AT receptors. Basal intracellular calcium concentrations did not differ between DPDE (109 +/- 11 nM) and CFPAC (103 +/- 8 nM) cells. AngII significantly increased measured intracellular calcium concentrations in both DPDE (909 +/- 98 nM) and CFPAC (879 +/- 207 nM) cells, as did ATP (DPDE = 1722 +/- 228 nM; CFPAC = 1522 +/- 245 nM). In the patch clamp studies, a variety of different channels were observed; they appeared to be an 11pS nonselective cation (NSC) channel, a 4.6pS Na+ channel, a 3pS anion channel, and an 8pS chloride channel. The latter channel had characteristics similar to cystic fibrosis transmembrane conductance regulator (CFTR). Apical or basolateral application of AngII activated both the 11pS NSC and the 3pS channels.

CONCLUSION

In nontransformed DPDE and CFPAC cells, specific AngII receptors mediate increases in [Ca ]. The latter effect of AngII may elicit activation of calcium-mediated chloride channels, suggesting a role for AngII as an alternative mediator of pancreatic ductal secretion.

Pancreatic cell lines: a review

Pancreatic cancer has an extremely poor prognosis and lacks early diagnostic and therapeutic possibilities, mainly because of its silent course and explosive fatal outcome. The histogenesis of the disease and early biochemical and genetic alterations surrounding carcinogenesis are still controversial. In vitro studies offer a useful tool to study physiologic, pathophysiologic, differentiation, and transformation processes of cells and to understand some of these shortcomings. The extreme difficulties in isolating individual pancreatic cells and their purification by maintaining their native characteristics have limited research in this area. This review is intended to present and discuss the current availability of rodent and pancreatic cell lines, their differences as well as the difficulties, limitations, and characteristics of these cultured cells. Discussed are in vitro models; ductal, islet, and acinar cell culture; cell differentiation; cell transformation, including genetic and chromosomal alterations; as well as tumor cell markers. Also addressed are the advantages and problems associated with the cell culture in humans and rodents. Advancements in tissue culture technique and molecular biology offer steady progress in this important line of research. The improved methods not only promise the establishment of beta-cell cultures for the treatment of diabetes, but also for studying sequential genetic alterations during pancreatic carcinogenesis and in understanding the tumor cell origin.

Establishment of human pancreatic ductal cells in a long-term culture

Cultivation and preservation of human pancreatic ductal cells have remained a challenge. With a defined culture medium and refinement of culturing techniques, we have been able to maintain human pancreatic ductal cells without any genetic manipulation in culture for more than 16 months. Freshly isolated ductal fragments were placed on a rocker in M3:5 medium free of collagen for 14 days to remove fibroblasts and endocrine cells before allowing them to attach. The cells produced an excessive amount of mucin and expressed the duct specific cytokeratins (CK) 7 and 19, DU-PAN2, CA19-9, carbonic anhydrase II (CA II), and secretin receptors. During the course of the culture, however, the cells gradually lost the expression of CA II, secretin receptors, DU-PAN2, and CA 19-9 and assumed an undifferentiated phenotype, which showed an upregulation of transforming growth factor alpha (TGFalpha) and epidermal growth factor receptor (EGFR), an increase in the expression of Ki-67, and an increased binding to Phaseolus vulgaris leucoagglutinin (PHA-L) and tomato lectin. These ductal cells present a useful source with which to study physiologic aspects of ductal cells including differentiation.

Immortal human pancreatic duct epithelial cell lines with near normal genotype and phenotype

Immortal epithelial cell lines were previously established after transduction of the HPV16-E6E7 genes into primary cultures of normal pancreatic duct epithelial cells. Single clones were isolated that demonstrated near normal genotype and phenotype. The proliferation of HPDE6-E6E7c7 and c11 cells is anchorage-dependent, and they were nontumorigenic in SCID mice. The cell lines demonstrated many phenotypes of normal pancreatic duct epithelium, including mRNA expression of carbonic anhydrase II, MUC-1, and cytokeratins 7, 8, 18, and 19. These cells have normal Ki-ras, p53, c-myc, and p16(INK4A) genotypes. Cytogenetic studies demonstrated losses of 3p, 10p12, and 13q14, the latter included the Rb1 gene. The wild-type p53 protein was detectable at very low levels consistent with the presence of E6 gene product, and the lack of functional p53 pathway was confirmed by the inability for gamma-irradiation to up-regulate p53 and p21waf1/cip1 protein. The p110/Rb protein level was also not detectable consistent with the expression of E7 protein and haploid loss of Rb1 gene. Despite this, the proliferation of both c7 and c11 cells were markedly inhibited by transforming growth factor-beta1. This was associated with up-regulation of p21cip1/waf1 but not p27kip1. Further studies showed that p130/Rb2 and cyclin D3 were expressed, suggesting that p130/Rb2 may have partially assumed the maintenance of G(1) cell cycle checkpoint regulation. These results indicate that except for the loss of p53 functional pathway, the two clones of HPDE6-E6E7 cells demonstrated a near normal genotype and phenotype of pancreatic duct epithelial cells. These cell lines will be useful for future studies on the molecular basis of pancreatic duct cell carcinogenesis and islet cell differentiation.

Growth factors, receptors, and molecular alterations in pancreatic cancer. Putting it all together

Because of the dismal prognosis of advanced ductal pancreatic adenocarcinoma, recent investigational strategies have focused on improved detection and therapeutic intervention in early-stage pancreatic cancer. The obvious cost constraints of screening populations at risk but with a low tumor yield will restrict screening protocols to only the highest risk groups (hereditary pancreatitis = age 50, certain hereditary pancreatic cancer kindreds). The vast majority of patients, either lacking or exhibiting an inherited predisposition to pancreatic cancer, will continue to present with disease not resectable for cure. The authors believe that the best hope for these patients lies in the further delineation of the integrative pathophysiology driving tumor growth; this would facilitate the future development of a computer program or other modality that would predict the dominant pathways driving the growth and spread of each tumor based on its "molecular profile." This article reviews the authors' current knowledge regarding the growth factors, receptors, and molecular alterations driving uncontrolled proliferation, local invasion, and metastatic spread of these tumors. The current and potential contributions of studies in cohorts with an inherited predisposition to pancreatic cancer to this pathophysiologic model are also discussed. The future strategy for incorporating this information into a working pathophysiologic road map with clinical relevance is subsequently outlined.