LGR5 and Nanog identify stem cell signature of pancreas beta cells which initiate pancreatic cancer

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Stereospecific NANOG PEST Stabilization by Pin1

NANOG protein levels correlate with stem cell pluripotency. NANOG concentrations fluctuate constantly with low NANOG levels leading to spontaneous cell differentiation. Previous literature implicated Pin1, a phosphorylation-dependent prolyl isomerase, as a key player in NANOG stabilization. Here, using NMR spectroscopy, we investigate the molecular interactions of Pin1 with the NANOG unstructured N-terminal domain that contains a PEST sequence with two phosphorylation sites. Phosphorylation of NANOG PEST peptides increases affinity to Pin1. By systematically increasing the amount of cis PEST conformers, we show that the peptides bind tighter to the prolyl isomerase domain (PPIase) of Pin1. Phosphorylation and cis Pro enhancement at both PEST sites lead to a 5-10-fold increase in NANOG binding to the Pin1 WW domain and PPIase domain, respectively. The cis-populated NANOG PEST peptides can be potential inhibitors for disrupting Pin1-dependent NANOG stabilization in cancer stem cells.

Comprehensive Investigation Illustrates the Role of M2 Macrophages and Its Related Genes in Pancreatic Cancer

Background and Objectives: M2 macrophages play an important role in cancers. Our study aimed to illustrate the effect of M2 macrophages in pancreatic cancer (PC). Materials and Methods: The open-access data used for analysis were downloaded from The Cancer Genome Atlas Program database, as well as some online databases. R software was mainly used for data analysis based on the specific packages. Results: Here, we comprehensively investigated the role of M2 macrophages and their related genes in PC. We performed the biological enrichment of M2 macrophages in PC. Meanwhile, we identified adenosine A3 receptor (TMIGD3) as the interest gene for further analysis. The single-cell analysis showed that was mainly expressed in the Mono/Macro cells based on the data from multiple data cohorts. Biological investigation showed that TMIGD3 was primarily enriched in angiogenesis, pancreas-beta cells and TGF-beta signaling. Tumor microenvironment analysis indicated that TMIGD3 was positively correlated with monocyte_MCPCOUNTER, NK cell_MCPCOUNTER, macrophages M2_CIBERSORT, macrophage_EPIC, neutrophil_TIMER and endothelial cell_MCPCOUNTER. Interestingly, we determined that all the immune functions quantified by single sample gene set enrichment analysis algorithms were activated in the patients with high TMIGD3 expression. Conclusions: Our results provide a novel direction for the research focused on the M2 macrophages in PC. Meanwhile, TMIGD3 was identified as an M2 macrophage-related biomarker for PC.

A Comprehensive Characterization of Stemness in Cell Lines and Primary Cells of Pancreatic Ductal Adenocarcinoma

The aim of this study is to provide a comprehensive characterization of stemness in pancreatic ductal adenocarcinoma (PDAC) cell lines. Seventeen cell lines were evaluated for the expression of cancer stem cell (CSC) markers. The two putative pancreatic CSC phenotypes were expressed heterogeneously ranging from 0 to 99.35% (median 3.46) for ESA+CD24+CD44+ and 0 to 1.94% (median 0.13) for CXCR4+CD133+. Cell lines were classified according to ESA+CD24+CD44+ expression as: Low-Stemness (LS; <5%, n = 9, median 0.31%); Medium-Stemness (MS; 6−20%, n = 4, median 12.4%); and High-Stemness (HS; >20%, n = 4, median 95.8%) cell lines. Higher degree of stemness was associated with in vivo tumorigenicity but not with in vitro growth kinetics, clonogenicity, and chemo-resistance. A wide characterization (chemokine receptors, factors involved in pancreatic organogenesis, markers of epithelial−mesenchymal transition, and secretome) revealed that the degree of stemness was associated with KRT19 and NKX2.2 mRNA expression, with CD49a and CA19.9/Tie2 protein expression, and with the secretion of VEGF, IL-7, IL-12p70, IL-6, CCL3, IL-10, and CXCL9. The expression of stem cell markers was also evaluated on primary tumor cells from 55 PDAC patients who underwent pancreatectomy with radical intent, revealing that CXCR4+/CD133+ and CD24+ cells, but not ESA+CD24+CD44+, are independent predictors of mortality.

Understanding pancreatic cancer stem cells and their role in carcinogenesis: a narrative review

OBJECTIVE

The purpose of this review article is to describe the pathogenesis of pancreatic cancer and to better understand the role of abnormal stem cells in the development of pancreatic cancer.

BACKGROUND

Pancreatic cancer is a highly fatal disease that is caused by the uncontrolled proliferation of pancreatic exocrine or neuroendocrine glands. It is believed that pancreatic cancers arise from a small population of abnormal cancer stem cells (CSCs) that promote tumorigenesis, tumor metastasis and therapeutic resistance. The molecular markers CD133, CXCR4, DCLK1, c-MET, ABCG2 and Lgr5 are routinely used to detected and observe the behaviours of pancreatic cancer stem cells (PCSCs).

METHODS

A comprehensive search was performed on PubMed, Google Scholar, Scopus, Clinicaltrials.gov and Web of Science using related keywords. Articles focusing on PCSCs and pancreatic cancer pathogenesis, biochemistry and clinical trials were selected.

CONCLUSIONS

Although very little is known about the exact cause of pancreatic cancer, PCSCs seem to play an important role in carcinogenesis. Mutated biochemical cascades include Sonic Hedgehog, K-RAS-JNK, DLL4/Notch and Nodal/Activin. Several clinical trials are trying to determine if the transplantation of hematopoietic stem cell or peripheral stem cells could be useful for the treatment of such an aggressive tumor.

A new pancreatic adenocarcinoma-derived organoid model of acquired chemoresistance to FOLFIRINOX: First insight of the underlying mechanisms

BACKGROUND INFORMATION

Although improvements have been made in the management of pancreatic adenocarcinoma (PDAC) during the past 20 years, the prognosis of this deadly disease remains poor with an overall 5-year survival under 10%. Treatment with FOLFIRINOX, a combined regimen of 5-fluorouracil, irinotecan (SN-38) and oxaliplatin, is nonetheless associated with an excellent initial tumour response and its use has allowed numerous patients to go through surgery while their tumour was initially considered unresectable. These discrepancies between initial tumour response and very low long-term survival are the consequences of rapidly acquired chemoresistance and represent a major therapeutic frontier. To our knowledge, a model of resistance to the combined three drugs has never been described due to the difficulty of modelling the FOLFIRINOX protocol both in vitro and in vivo. Patient-derived tumour organoids (PDO) are the missing link that has long been lacking in the wide range of epithelial cancer models between 2D adherent cultures and in vivo xenografts. In this work we sought to set up a model of PDO with resistance to FOLFIRINOX regimen that we could compare to the paired naive PDO.

RESULTS

We first extrapolated physiological concentrations of the three drugs using previous pharmacodynamics studies and bi-compartmental elimination models of oxaliplatin and SN-38. We then treated PaTa-1818x naive PDAC organoids with six cycles of 72 h-FOLFIRINOX treatment followed by 96 h interruption. Thereafter, we systematically compared treated organoids to PaTa-1818x naive organoids in terms of growth, proliferation, viability and expression of genes involved in cancer stemness and aggressiveness.

CONCLUSIONS

We reproductively obtained resistant organoids FoxR that significantly showed less sensitivity to FOLFORINOX treatment than the PaTa-1818x naive organoids from which they were derived. Our resistant model is representative of the sequential steps of chemoresistance observed in patients in terms of growth arrest (proliferation blockade), residual disease (cell quiescence/dormancy) and relapse.

SIGNIFICANCE

To our knowledge, this is the first genuine in vitro model of resistance to the three drugs in combined therapy. This new PDO model will be a great asset for the discovery of acquired chemoresistance mechanisms, knowledge that is mandatory before offering new therapeutic strategies for pancreatic cancer.

The plasticity of pancreatic cancer stem cells: implications in therapeutic resistance

The ever-growing perception of cancer stem cells (CSCs) as a plastic state rather than a hardwired defined entity has evolved our understanding of the functional and biological plasticity of these elusive components in malignancies. Pancreatic cancer (PC), based on its biological features and clinical evolution, is a prototypical example of a CSC-driven disease. Since the discovery of pancreatic CSCs (PCSCs) in 2007, evidence has unraveled their control over many facets of the natural history of PC, including primary tumor growth, metastatic progression, disease recurrence, and acquired drug resistance. Consequently, the current near-ubiquitous treatment regimens for PC using aggressive cytotoxic agents, aimed at ‘‘tumor debulking’’ rather than eradication of CSCs, have proven ineffective in providing clinically convincing improvements in patients with this dreadful disease. Herein, we review the key hallmarks as well as the intrinsic and extrinsic resistance mechanisms of CSCs that mediate treatment failure in PC and enlist the potential CSC-targeting ‘natural agents’ that are gaining popularity in recent years. A better understanding of the molecular and functional landscape of PCSC-intrinsic evasion of chemotherapeutic drugs offers a facile opportunity for treating PC, an intractable cancer with a grim prognosis and in dire need of effective therapeutic advances.

Development and Clinical Validation of a Seven-Gene Prognostic Signature Based on Multiple Machine Learning Algorithms in Kidney Cancer

About a third of patients with kidney cancer experience recurrence or cancer-related progression. Clinically, kidney cancer prognoses may be quite different, even in patients with kidney cancer at the same clinical stage. Therefore, there is an urgent need to screen for kidney cancer prognosis biomarkers. Differentially expressed genes (DEGs) were identified using kidney cancer RNA sequencing data from the Gene Expression Omnibus (GEO) database. Biomarkers were screened using random forest (RF) and support vector machine (SVM) models, and a multigene signature was constructed using the least absolute shrinkage and selection operator (LASSO) regression analysis. Univariate and multivariate Cox regression analyses were performed to explore the relationships between clinical features and prognosis. Finally, the reliability and clinical applicability of the model were validated, and relationships with biological pathways were identified. Western blots were also performed to evaluate gene expression. A total of 50 DEGs were obtained by intersecting the RF and SVM models. A seven-gene signature (RNASET2, EZH2, FXYD5, KIF18A, NAT8, CDCA7, and WNT7B) was constructed by LASSO regression. Univariate and multivariate Cox regression analyses showed that the seven-gene signature was an independent prognostic factor for kidney cancer. Finally, a predictive nomogram was established in The Cancer Genome Atlas (TCGA) cohort and validated internally. In tumor tissue, RNASET2 and FXYD5 were highly expressed and NAT8 was lowly expressed at the protein and transcription levels. This model could complement the clinicopathological characteristics of kidney cancer and promote the personalized management of patients with kidney cancer.

Ecdysteroid Derivatives that Reverse P-Glycoprotein-Mediated Drug Resistance

The expression of multidrug resistance P-glycoprotein (P-gp) by cancer cells represents one of the major drawbacks to successful cancer therapy. Accordingly, the development of drugs that inhibit the activity of this transporter remains a major challenge in cancer drug discovery. In this context, several new ecdysteroid derivatives have been synthesized and evaluated as P-gp inhibitors. Two of them (compounds 9 and 14) were able to resensitize CEM^Vbl100 and LoVo^Doxo resistant cell lines to vinblastine and doxorubicin, respectively. Indeed, both compounds 9 and 14 increased the cellular accumulation of rhodamine 123 in cells expressing P-gp and stimulated basal P-glycoprotein-ATPase activity at a 1 μM concentration, demonstrating their interference with the transport of other substrates in a competitive mode. Moreover, in a medulloblastoma cell line (DAOY), compounds 9 and 14 reduced the side population representing cancer stem cells, which are characterized by a high expression of ABC drug transporters. Further, in DAOY cells, the same two compounds synergized with cisplatin and vincristine, two drugs used commonly in the therapy of medulloblastoma. Molecular docking studies on the homology-modeled structure of the human P-glycoprotein provided a rationale for the biological results, validating the binding mode within the receptor site, in accordance with lipophilicity data and observed structure-activity relationship information. Altogether, the present results endorse these derivatives as promising P-gp inhibitors, and they may serve as candidates to reverse drug resistance in cancer cells.

Islets and pancreatic ductal adenocarcinoma - An opportunity for translational research from the 'Bench to the Bedside'

The islet-acinar axis is of prime importance to the optimal functioning of the human pancreas. Not only is this inter-relationship important for normal physiological processes, it is also relevant in diseased states, including chronic pancreatitis and pancreatic ductal adenocarcinoma (PDAC). Early experiments, nearly 4 decades ago, explored the role of islets in the development and progression of PDAC. These led to further studies that provided compelling evidence to support the role of islets and their hormones in PDAC. This association presents oncologists with therapeutic options not only for managing, but potentially preventing PDAC, a cancer that is well known for its poor patient outcomes. This review will discuss the accumulated evidence regarding the role of islets and their hormones in PDAC and highlight areas for future research.

EMT and Stemness-Key Players in Pancreatic Cancer Stem Cells

Metastasis and tumor progression are the major cause of death in patients suffering from pancreatic ductal adenocarcinoma. Tumor growth and especially dissemination are typically associated with activation of an epithelial-to-mesenchymal transition (EMT) program. This phenotypic transition from an epithelial to a mesenchymal state promotes migration and survival both during development and in cancer progression. When re-activated in pathological contexts such as cancer, this type of developmental process confers additional stemness properties to specific subsets of cells. Cancer stem cells (CSCs) are a subpopulation of cancer cells with stem-like features that are responsible for the propagation of the tumor as well as therapy resistance and cancer relapse, but also for circulating tumor cell release and metastasis. In support of this concept, EMT transcription factors generate cells with stem cell properties and mediate chemoresistance. However, their role in pancreatic ductal adenocarcinoma metastasis remains controversial. As such, a better characterization of CSC populations will be crucial in future development of therapies targeting these cells. In this review, we will discuss the latest updates on the mechanisms common to pancreas development and CSC-mediated tumor progression.

Pancreatic duct-like cell line derived from pig embryonic stem cells: expression of uroplakin genes in pig pancreatic tissue

The isolation of a cell line, PICM-31D, with phenotypic characteristics like pancreatic duct cells is described. The PICM-31D cell line was derived from the previously described pig embryonic stem cell-derived exocrine pancreatic cell line, PICM-31. The PICM-31D cell line was morphologically distinct from the parental cells in growing as a monolayer rather than self-assembling into multicellular acinar-like structures. The PICM-31D cells were propagated for over a year at split ratios of 1:3 to 1:10 at each passage without change in phenotype or growth rate. Electron microscopy showed the cells to be a polarized epithelium of cuboidal cells joined by tight junction-like adhesions at their apical/lateral aspect. The cells contained numerous mucus-like secretory vesicles under their apical cell membrane. Proteomic analysis of the PICM-31D's cellular proteins detected MUC1 and MUC4, consistent with mucus vesicle morphology. Gene expression analysis showed the cells expressed pancreatic ductal cell-related transcription factors such as GATA4, GATA6, HES1, HNF1A, HNF1B, ONECUT1 (HNF6), PDX1, and SOX9, but little or no pancreas progenitor cell markers such as PTF1A, NKX6-1, SOX2, or NGN3. Pancreas ductal cell-associated genes including CA2, CFTR, MUC1, MUC5B, MUC13, SHH, TFF1, KRT8, and KRT19 were expressed by the PICM-31D cells, but the exocrine pancreas marker genes, CPA1 and PLA2G1B, were not expressed by the cells. However, the exocrine marker, AMY2A, was still expressed by the cells. Surprisingly, uroplakin proteins were prominent in the PICM-31D cell proteome, particularly UPK1A. Annexin A1 and A2 proteins were also relatively abundant in the cells. The expression of the uroplakin and annexin genes was detected in the cells, although only UPK1B, UPK3B, ANXA2, and ANXA4 were detected in fetal pig pancreatic duct tissue. In conclusion, the PICM-31D cell line models the mucus-secreting ductal cells of the fetal pig pancreas.

Phytochemicals, withaferin A and carnosol, overcome pancreatic cancer stem cells as c-Met inhibitors

Receptor tyrosine kinases (RTKs) are pharmaceutically attractive targets due to their fundamental role in tumor formation. The hallmark of pancreatic cancer is its high mortality rate attributed to the existence of cancer stem cell (CSC) subpopulations which result in therapy resistance and recurrence. c-Met is a known pancreatic CSC marker that belongs to the family of RTKs. To surmount the hurdles related to ligand-independent c-Met activation, we aimed to elucidate the inhibitory mechanisms of withaferin A (WA) and carnosol (CA) as two hit phytochemicals against c-Met kinase domain. Both tested compounds attenuated HGF-mediated proliferation across various established c-Met⁺ cancer cell lines and altered cell cycle distribution accompanied by apoptosis induction. Scratch assay confirmed the anti-migratory activity of WA and CA in AsPC-1 cells. The blockade of HGF-driven cellular growth and motility was reflected by the suppression of c-Met phosphorylation and its downstream pro-survival pathway Akt. Further studies showed that the administration of WA and CA diminished the sphere-formation and clonogenic potential which was validated by down-regulation of pluripotency maintaining genes (oct-4 and nanog), demonstrating their potentiality to target pancreatic CSCs. As more than 60% of anti-cancer drugs are composed of natural product-derived inhibitors known as fourth generation inhibitors, our present data suggest that WA and CA may hold promise to eradicate CSCs in c-Met-dependent cancers.

Not only stem cells, but also mature cells, particularly neuroendocrine cells, may develop into tumours: time for a paradigm shift

Stem cells are considered the origin of neoplasms in general, and malignant tumours in particular, and the stage at which the stem cells stop their differentiation determines the degree of malignancy. However, there is increasing evidence supporting an alternative paradigm. Tumours may develop by dedifferentiation from mature cells able to proliferate. Studies of gastric carcinogenesis demonstrate that mature neuroendocrine (NE) cells upon long-term overstimulation may develop through stages of hyperplasia, dysplasia, and rather benign tumours, into highly malignant carcinomas. Dedifferentiation of cells may change the histological appearance and impede the identification of the cellular origin, as seen with gastric carcinomas, which in many cases are dedifferentiated neuroendocrine tumours. Finding the cell of origin is important to identify risk factors for cancer, prevent tumour development, and tailor treatment. In the present review, we focus not only on gastric tumours, but also evaluate the role of neuroendocrine cells in tumourigenesis in two other foregut-derived organs, the lungs and the pancreas, as well as in the midgut-derived small intestine.

Cancer Stemness, Immune Cells, and Epithelial-Mesenchymal Transition Cooperatively Predict Prognosis in Colorectal Carcinoma

BACKGROUND

Tumor tissues consist of heterogeneous cancer cells and stroma cells, including cancer stem cells and immune cells. Epithelial-mesenchymal transition (EMT) programs closely associate with acquisition of stemness. We investigated for the first time the clinical significance of combining cancer stem cells, immune cells, and EMT traits.

MATERIALS AND METHODS

In 419 colorectal carcinomas, stem-cell markers (Nanog, Lgr5, CD44v6, ALDH1A1), EMT markers (E-cadherin, Snail), and immune-cell markers (CD3⁺, CD4⁺ or CD8⁺ T lymphocytes, CD20⁺ B lymphocytes, CD68⁺ macrophages) were detected in tumor center (TC) and tumor invasive front by an immunohistochemical method. Unsupervised hierarchical clustering analysis was performed to group the data according to correlation analyses. Survival analysis and chi-square test were performed to explore the significance of this clustering.

RESULTS

There were correlations among the expression of Nanog, Lgr5, CD44v6, and immune cell counts (P < .05). Nanog, Lgr5, CD44v6, and ALDH1A1 positively related to E-cadherin or Snail (P < .05). A cluster (termed cluster SIE) based on cancer stemness markers (Nanog, Lgr5, CD44v6, ALDH1A1 in TC), EMT markers (E-cadherin, Snail in TC), and immune-cell markers (CD4⁺ and CD8⁺ T-lymphocyte counts in TC, and CD68⁺ macrophages in tumor invasive front) could significantly predict 5-year survival (P = .040). Multivariate Cox proportional hazard model showed that only tumor, node, metastasis classification system stage and cluster SIE were independent prognostic predictors (hazard ratio = 1.920; 95% confidence interval, 1.082-3.407; P = .026).

CONCLUSION

Cancer stemness, immune state, and EMT programs should be considered as a whole. Cluster SIE was an independent predictor for 5-year survival of patients with colorectal cancer.

Insulin-Deficient Mouse β-Cells Do Not Fully Mature but Can Be Remedied Through Insulin Replacement by Islet Transplantation

Insulin receptor (IR) insufficiency in β-cells leads to impaired insulin secretion and reduced β-cell hyperplasia in response to hyperglycemia. Selective IR deficiency in β-cells in later embryological development may lead to compensatory β-cell hyperplasia. Although these findings suggest insulin signaling on the β-cell is important for β-cell function, they are confounded by loss of signaling by the insulinlike growth factors through the IR. To determine whether insulin itself is necessary for β-cell development and maturation, we performed a characterization of pancreatic islets in mice with deletions of both nonallelic insulin genes (Ins1-/-Ins2-/-). We immunostained neonatal Ins1-/-Ins2-/- and Ins1+/+Ins2+/+ pancreata and performed quantitative polymerase chain reaction on isolated neonatal islets. Insulin-deficient islets had reduced expression of factors normally expressed in maturing β-cells, including muscoloaponeurotic fibrosarcoma oncogene homolog A, homeodomain transcription factor 6.1, and glucose transporter 2. Ins1-/-Ins2-/-β-cells expressed progenitor factors associated with stem cells or dedifferentiated β-cells, including v-myc avian myolocytomatosis viral oncogene lung carcinoma derived and homeobox protein NANOG. We replaced insulin by injection or islet transplantation to keep mice alive into adulthood to determine whether insulin replacement was sufficient for the completed maturation of insulin-deficient β-cells. Short-term insulin glargine (Lantus®) injections partially rescued the β-cell phenotype, whereas long-term replacement of insulin by isogenic islet transplantation supported the formation of more mature β-cells. Our findings suggest that tightly regulated glycemia, insulin species, or other islet factors are necessary for β-cell maturation.

Ovarian Cancer Stem Cells: Unraveling a Germline Connection

Ovarian cancer is most lethal among gynecological cancers with often fatal consequences due to lack of effective biomarkers and relapse, which propels ovarian cancer research into unique directions to establish solid targeted therapeutics. "Ovarian stem cells" expressing germline pluripotent markers serve as novel paradigm with potential to address infertility, menopause, and probably influence tumor initiation. Cancer stem cells (CSCs) pose vital role in tumor recurrence and hence it is extremely important to study them with respect to ovarian stem cells across various cancer stages and normal ovaries. Pluripotent (OCT4, NANOG, SOX2, SSEA1, and SSEA4), germline (IFITM3, VASA/DDX4), and cancer stem (CD44, LGR5) cell specific markers were characterized for protein and mRNA expression in tumor tissues to understand their distribution in the surface epithelium and ovarian cortex in benign, borderline, and high-grade malignant stages. To elucidate whether pluripotent ovarian germline stem cells and CSCs are common subset of stem cells in tumor tissues, VASA was colocalized with known pluripotent stem (OCT4, SSEA1, SSEA4) and CSC (CD44, LGR5) specific markers by confocal microscopy. Single, smaller spherical (≤5 μm), and larger elliptical fibroblast like (≥10 μm) cells (also in clusters or multiples) were detected implying probable functional behavioral significance of cells in tumor initiation and metastasis across various cancer stages. Cells revealed characteristic staining pattern in ovarian surface epithelium (OSE) and cortex regions exclusive for each marker. Co-expression studies revealed specific subpopulations existing simultaneously in OSE and cortex and that a dynamic hierarchy of (cancer) stem cells with germline properties prevails in normal ovaries and cancer stages. Novel insights into CSC biology with respect to ovarian and germline stem cell perspective were obtained. Understanding molecular signatures and distribution within ovarian tissue may enable identification of precise tumor-initiating CSC populations and signaling pathways thus improving their efficient targeting and strategies to prevent their dissemination causing fatal relapse.

Pancreatic Cancer: Molecular Characterization, Clonal Evolution and Cancer Stem Cells

Pancreatic Ductal Adenocarcinoma (PDAC) is the fourth most common cause of cancer-related death and is the most lethal of common malignancies with a five-year survival rate of <10%. PDAC arises from different types of non-invasive precursor lesions: intraductal papillary mucinous neoplasms, mucinous cystic neoplasms and pancreatic intraepithelial neoplasia. The genetic landscape of PDAC is characterized by the presence of four frequently-mutated genes: KRAS, CDKN2A, TP53 and SMAD4. The development of mouse models of PDAC has greatly contributed to the understanding of the molecular and cellular mechanisms through which driver genes contribute to pancreatic cancer development. Particularly, oncogenic KRAS-driven genetically-engineered mouse models that phenotypically and genetically recapitulate human pancreatic cancer have clarified the mechanisms through which various mutated genes act in neoplasia induction and progression and have led to identifying the possible cellular origin of these neoplasias. Patient-derived xenografts are increasingly used for preclinical studies and for the development of personalized medicine strategies. The studies of the purification and characterization of pancreatic cancer stem cells have suggested that a minority cell population is responsible for initiation and maintenance of pancreatic adenocarcinomas. The study of these cells could contribute to the identification and clinical development of more efficacious drug treatments.

A novel inhibitory anti-invasive MAb isolated using phenotypic screening highlights AnxA6 as a functionally relevant target protein in pancreatic cancer

Background:

Discovery and validation of new antibody tractable targets is critical for the development of new antibody therapeutics to address unmet needs in oncology.

Methods:

A highly invasive clonal variant of the MDA-MB-435S cell line was used to generate monoclonal antibodies (MAbs), which were screened for anti-invasive activity against aggressive cancer cells in vitro. The molecular target of selected inhibitory MAb 9E1 was identified using immunoprecipitation/liquid chromatography-tandem mass spectrometry. The potential anti-tumour effects of MAb 9E1 were investigated in vitro together with immunohistochemical analysis of the 9E1 target antigen in normal and cancer tissues.

Results:

MAb 9E1 significantly decreases invasion in pancreatic, lung squamous and breast cancer cells and silencing of its target antigen, which was revealed as AnxA6, leads to markedly reduced invasive capacity of pancreatic and lung squamous cancer in vitro. IHC using MAb 9E1 revealed that AnxA6 exhibits a high prevalence of membrane immunoreactivity across aggressive tumour types with restricted expression observed in the majority of normal tissues. In pancreatic ductal adenocarcinoma, high AnxA6 IHC score correlated with the presence of tumour budding at the invasive front of tumours (P=0.082), the presence of perineural invasion (P= <0.0001) and showed a weak correlation with reduced survival (P=0.2242).

Conclusions:

This study highlights the use of phenotypic hybridoma screening as an effective strategy to select a novel function-blocking MAb, 9E1 with anti-cancer activity in vitro. Moreover, through characterisation of the 9E1 target antigen, AnxA6, our findings support further investigation of AnxA6 as a potential candidate target for antibody-mediated inhibition of pancreatic cancer.

Small Nucleolar Noncoding RNA SNORA23, Up-Regulated in Human Pancreatic Ductal Adenocarcinoma, Regulates Expression of Spectrin Repeat-Containing Nuclear Envelope 2 to Promote Growth and Metastasis of Xenograft Tumors in Mice

BACKGROUND & AIMS

Small nucleolar noncoding RNAs (snoRNAs) regulate function of ribosomes, and specific snoRNAs are dysregulated in some cancer cells. We investigated dysregulation of snoRNAs in pancreatic ductal adenocarcinoma (PDAC) cells.

METHODS

We investigated snoRNA expression in PDAC cell lines by complementary DNA microarray and quantitative reverse transcription polymerase chain reaction. In PDAC (n = 133), intraductal papillary mucinous neoplasm (n = 16), mucinous cystic neoplasm-associated PDAC (n = 1), and non-tumor pancreas (n = 8) and liver (n = 3) tissues from subjects who underwent surgical resection, levels of snoRNA were measured by quantitative reverse transcription polymerase chain reaction and compared with clinicopathologic parameters and survival times determined by Kaplan-Meier analysis. To examine snoRNA function, PDAC cells were transfected with snoRNA-antisense oligonucleotides flanked with amido-bridged nucleic acids, or snoRNA-expression plasmids, and analyzed in proliferation, colony formation, spheroid formation, and invasion assays. To identify snoRNA-related factors, cells were analyzed by gene expression and proteomic profiling and immunoblot assays. Mice were given intrasplenic injections of MIA PaCa2- or Suit2-HLMC cells; tumor-bearing nude mice were then given 3 weekly injections of an antisense oligonucleotides against SNORA23, a H/ACA-box type snoRNA, and tumor growth and metastasis to liver, blood, and pancreas were analyzed.

RESULTS

Levels of SNORA23 increased and accumulated at the nucleolus in highly metastatic MIA PaCa2- or Suit2-HLMC cells compared with their parental cells. We detected SNORA23 in human PDAC specimens but not in non-tumor pancreatic tissue. PDAC level of SNORA23 correlated with invasion grade and correlated inversely with disease-free survival time of patients. Expression of SNORA23 in PDAC cells increased their invasive activity and colony formation, and spheroid formation was inhibited by SNORA23 knockdown. In gene expression and proteomic profile analyses, we found SNORA23 to increase expression of spectrin repeat-containing nuclear envelope 2 (SYNE2) messenger RNA and protein. Knockdown of SYNE2 in PDAC cells reduced their invasive activities and anchor-independent survival. Administration of SNORA23 antisense oligonucleotides to mice slowed growth of xenograft tumors, tumor expression of SYNE2, tumor cell dissemination, and metastasis to liver.

CONCLUSIONS

We found expression of the snoRNA SNORA23, which mediates sequence-specific pseudouridylation of ribosomal RNAs, to be increased in human PDAC tissues compared with non-tumor tissues, and levels to correlate with tumor invasion grade and patient survival time. SNORA23 increases expression of SYNE2, possibly through modulation of ribosome biogenesis, to promote PDAC cell survival and invasion, and growth and metastasis of xenograft tumors in mice.

Concise Review: NANOG in Cancer Stem Cells and Tumor Development: An Update and Outstanding Questions

The homeobox domain transcription factor NANOG, a key regulator of embryonic development and cellular reprogramming, has been reported to be broadly expressed in human cancers. Functional studies have provided strong evidence that NANOG possesses protumorigenic attributes. In addition to promoting self-renewal and long-term proliferative potential of stem-like cancer cells, NANOG-mediated oncogenic reprogramming may underlie clinical manifestations of malignant disease. In this review, we examine the molecular origin, expression, biological activities, and mechanisms of action of NANOG in various malignancies. We also consider clinical implications such as correlations between NANOG expression and cancer prognosis and/or response to therapy. We surmise that NANOG potentiates the molecular circuitry of tumorigenesis, and thus may represent a novel therapeutic target or biomarker for the diagnosis, prognosis, and treatment outcome of cancer. Finally, we present critical pending questions relating NANOG to cancer stem cells and tumor development.

New insights into pancreatic cancer stem cells

Pancreatic cancer (PC) has been one of the deadliest of all cancers, with almost uniform lethality despite aggressive treatment. Recently, there have been important advances in the molecular, pathological and biological understanding of pancreatic cancer. Even after the emergence of recent new targeted agents and the use of multiple therapeutic combinations, no treatment option is viable in patients with advanced cancer. Developing novel strategies to target progression of PC is of intense interest. A small population of pancreatic cancer stem cells (CSCs) has been found to be resistant to chemotherapy and radiation therapy. CSCs are believed to be responsible for tumor initiation, progression and metastasis. The CSC research has recently achieved much progress in a variety of solid tumors, including pancreatic cancer to some extent. This leads to focus on understanding the role of pancreatic CSCs. The focus on CSCs may offer new targets for prevention and treatment of this deadly cancer. We review the most salient developments in important areas of pancreatic CSCs. Here, we provide a review of current updates and new insights on the role of CSCs in pancreatic tumor progression with special emphasis on DclK1 and Lgr5, signaling pathways altered by CSCs, and the role of CSCs in prevention and treatment of PC.

Profiles of cancer stem cell subpopulations in cholangiocarcinomas

Cholangiocarcinomas (CCAs) comprise a mucin-secreting form, intrahepatic or perihilar, and a mixed form located peripherally. We characterized cancer stem cells (CSCs) in CCA subtypes and evaluated their cancerogenic potential. CSC markers were investigated in 25 human CCAs in primary cultures and established cell lines. Tumorigenic potential was evaluated in vitro or in xenografted mice after s.c. or intrahepatic injection in normal and cirrhotic (carbon tetrachloride-induced) mice. CSCs comprised more than 30% of the tumor mass. Although the CSC profile was similar between mucin-intrahepatic and mucin-perihilar subtypes, CD13(+) CSCs characterized mixed-intrahepatic, whereas LGR5(+) characterized mucin-CCA subtypes. Many neoplastic cells expressed epithelial-mesenchymal transition markers and coexpressed mesenchymal and epithelial markers. In primary cultures, epithelial-mesenchymal transition markers, mesenchymal markers (vimentin, CD90), and CD13 largely predominated over epithelial markers (CD133, EpCAM, and LGR5). In vitro, CSCs expressing epithelial markers formed a higher number of spheroids than CD13(+) or CD90(+) CSCs. In s.c. tumor xenografts, tumors dominated by stromal markers were formed primarily by CD90(+) and CD13(+) cells. By contrast, in intrahepatic xenografts in cirrhotic livers, tumors were dominated by epithelial traits reproducing the original human CCAs. In conclusion, CSCs were rich in human CCAs, implicating CCAs as stem cell-based diseases. CSC subpopulations generate different types of cancers depending on the microenvironment. Remarkably, CSCs reproduce the original human CCAs when injected into cirrhotic livers.

Fat, epigenome and pancreatic diseases. Interplay and common pathways from a toxic and obesogenic environment

The worldwide obesity epidemic is paralleled by a rise in the incidence of pancreatic disorders ranging from "fatty" pancreas to pancreatitis and cancer. Body fat accumulation and pancreatic dysfunctions have common pathways, mainly acting through insulin resistance and low-grade inflammation, frequently mediated by the epigenome. These mechanisms are affected by lifestyle and by the toxic effects of fat and pollutants. An early origin is common, starting in pediatric age or during the fetal life in response to nutritional factors, endocrine disruptor chemicals (EDCs) or parental exposure to toxics. A "fatty pancreas" is frequent in obese and is able to induce pancreatic damage. The fat is a target of EDCs and of the cytotoxic/mutagenic effects of heavy metals, and is the site of bioaccumulation of lipophilic and persistent pollutants related with insulin resistance and able to promote pancreatic cancer. Increased Body Mass Index (BMI) can act as independent risk factor for a more severe course of acute pancreatitis and obesity is also a well-known risk factor for pancreatic cancer, that is related with BMI, insulin resistance, and duration of exposure to the toxic effects of fat and/or of environmental pollutants. All these mechanisms involve gene-environment interactions through epigenetic factors, and might be manipulated by primary prevention measures. Further studies are needed, pointing to better assess the interplays of modifiable factors on both obesity and pancreatic diseases, and to verify the efficacy of primary prevention strategies involving lifestyle and environmental exposure to toxics.

Dynamic distribution of ERK, p38 and JNK during the development of pancreatic ductal adenocarcinoma

We recently discovered that oncogenic c-kit is highly expressed concomitantly with the development of pancreatic ductal adenocarcinoma (PDAC). Since oncogenic c-kit may activate major pathways of protein tyrosine phosphorylation, we decided to investigate this issue in the major protein phosphorylation cascades. In normal pancreas labeling with antiphosphorylated ERK1/2 (pERK1/2) antibody was mainly confined to islets of Langerhans in close overlapping with insulin containing cells. Phosphorylated p38 (pp38) showed a similar pattern of distribution, while only weak labeling was evident for pJNK and no labeling of pMEK was observed. As expected, general ERK1/2 (gERK1/2), general p38 (gp38), general JNK (gJNK) as well as general MEK (gMEK) were all evident in islets of Langerhans and in the exocrine tissue. In early development of PDAC, pERK1/2 and pp38 retained their localization in islets of Langerhans. Intensive staining of pERK1/2 was also evident in the cancerous ducts, while the labeling with antibodies to pp38 was more moderate. While pJNK staining in islets of Langerhans was weak, with no labeling in the cancerous ducts, antibodies to gJNK revealed intensive staining suggesting the weak staining of pJNK is not due to the lack of the enzyme. In a more advanced stage of PDAC the carcinomas were clearly stained with pERK1/2 and pp38, while moderate staining with pJNK was also evident. In liver metastases, the cancer cells were heavily labeled with all three phospho-MAPKs. It should be noted that the localization of all three kinases was mainly in the cell nuclei. In the more advanced stage of PDAC, heavy labeling was evident using antibodies to gERK1/2, gp38, gJNK and gMEK. However, no labeling to pMEK was evident in parallel sections. Our data suggest that both in normal and cancerous pancreas, most of the MAPK activities are located in islets of Langerhans and cancerous ducts. It is suggested that using inhibitors to protein kinases may attenuate the progression of the disease.

TADG-12 as an early marker in the development of pancreatic ductal adenocarcinoma (PDAC): involvement of insulin containing cells

TADG-12 is a serine protease that was characterized as expressed in ovarian and gastric carcinomas. Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers and its late detection results in poor prognosis. Therefore, we decided to examine whether TADG-12 appears early in PDAC development. In normal pancreas, pale to moderate immunostaining is present in islets of Langerhans, while exocrine tissue and ducts are free from labeling. In contrast, in cancer patients, who still preserve the integrity of the exocrine and the endocrine tissues, a pronounced immunolabelling of TADG-12 was evident mainly located in the insulin containing β cells. In a more progressive stage of the disease TADG-12 was also evident in the deteriorated exocrine tissue. TADG-12 was also heavily labeled in islets of Langerhans, which were embedded in the stroma of the residual pancreatic tissue. Again, there was a considerable overlap between the labeling of insulin and TADG-12 in these islets. Close correlation between insulin and TADG-12 was also evident in islets of Langerhans surrounded by adipose cells. The TADG-12 labeled was confined to the cytoplasm and the membrane of the cells. In the progressive stage of PDAC, the cancerous ducts were clearly labeled with TADG-12 with no labeling of insulin. At high magnification the TADG-12 clearly labeled the cytoplasm and the cell wall membrane of duct cells, while the nuclei remained unstained upon incubation with antibodies to TADG-12. The present findings may assist in early detection of PDAC as well as targeting of TADG-12 in order to attenuate the rapid progression of the disease.

CD24 and Nanog identify stem cells signature of ovarian epithelium and cysts that may develop to ovarian cancer

Ovarian cancer is the most lethal gynecological cancer. There is a general debate whether ovarian cancer is an intrinsic or an imported disease. We investigated whether in normal morphological appearance and in early stages of ovarian tumorgenesis typical cancer cell markers such as CD24 and Nanog are expressed. In 25% of normal appearing ovaries of post-menopausal women there was co-localization of CD24 and Nanog in the walls of the ovarian cysts, leaving the epithelial cells on the surface of these ovaries free of Nanog or CD24 expression. In benign ovarian tumors 37% of specimens were positive to CD24 and Nanog labeling while 26% of them were localized in the cyst walls. In contrast, in serous borderline tumors 79% specimens were labeled with CD24, 42% of them were localized in cysts and in 32% of them showed co-localization with CD24 and Nanog was evident: the rest were labeled in the ovarian epithelial cells. In serous ovarian carcinomas 81% specimens were labeled with CD24 antibodies. In 45% of them co-localization with Nanog was evident in the bulk of the cancerous tissue. In mucinous carcinomas no labeling with CD24 or Nanog was evident. In view of the synergistic effect of CD24 and Nanog expressed in malignant cancer development in other systems, it is suggested that such an analysis can be valuable for early detection of ovarian cancer. Moreover, the abundance of these markers in cysts in the development of ovarian cancer may suggest that they present an intrinsic source of the development of the highly malignant disease. Finally, since CD24 is exposed on the surface of the cancer cells, it may be highly beneficial to target these cells with antibodies to CD24 conjugated to cytotoxic drugs for more efficient treatment of this malignant disease.

Modulation of c-kit expression in pancreatic adenocarcinoma: a novel stem cell marker responsible for the progression of the disease

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers because of late symptoms and resistance to chemotherapy and radiation therapy. We have investigated the appearance of c-kit, a stem cell marker, in both normal adult pancreatic tissue and in cancerous tissue. Apart from some very pale staining of islets of Langerhans, normal pancreas was devoid of staining with antibodies to c-kit. In contrast, in cancerous tissue that still preserves the overall integrity of the pancreatic tissue, there was a clear labeling in islets of Langerhans, which seemed to be co-localized with insulin containing β cells. In other cases, where the pancreatic tissue was completely deteriorated, intensive labeling was clearly evident in remnants of both the exocrine and the endocrine tissues. The duct cells of the adenocarcinoma were moderately but clearly labeled with antibodies to c-kit. In contrast, in metastasis of PDAC, very intensive labeling of c-kit was evident. The location of KRAS, which is strongly associated with PDAC, was also analyzed at the initial stages of the disease, when islets of Langerhans still preserve their integrity to a large extent. KRAS was found exclusively in islets of Langerhans and overlapped in its location with insulin and c-kit expressing cells. It is suggested that the modulation of the expression of c-kit, visualized by antibodies to the oncogene molecule, may play an important role in the formation and progression of PDAC. The absence of c-kit in normal pancreas and its appearance in PDAC is probably due to a mutational event, which probably allows conversion of the β cells into cancer stem cells (CSC). Co-expression of both c-kit and KRAS, typical markers for CSC with overlapping with insulin in islets of Langerhans, strongly support the notion that β-cells play a central role in the development of PDAC. The use of specific drugs that can attenuate the kinase activity of c-kit or target KRAS expressing cancer cells should be tested in order to attenuate the progression of this lethal disease.

Cytoplasmic expression of LGR5 in pancreatic adenocarcinoma

Background: CD133 has been identified as a cancer stem cell marker for pancreatic ductal adenocarcinoma. Although leucine-rich-repeat-containing G-protein-coupled receptor 5 (LGR5), a marker of intestinal stem cells, has been shown to be on a higher level of the stem cell hierarchy than CD133, the expression and function of LGR5 in pancreatic cancer tissue remains unclear. This study investigated tissue expression of LGR5 and CD133 in resected pancreatic cancer tissue.

Methods: LGR5 and CD133 expression was immunohistochemically examined in 9 patients with pancreatic ductal adenocarcinoma who underwent resection.

Results: LGR5 was expressed in the cytoplasm of pancreatic cancer cells in 4 of 9 cases. CD133 was not detected in cancerous tissue. In non-neoplastic tissue, LGR5 was expressed in the basolateral membrane of a subset of endocrine cells. Conversely, CD133 was expressed in the apical membrane of small duct cells. Co-localization of LGR5 and CD133 was not found in either neoplastic or non-neoplastic tissue. LGR5 expression in pancreatic cancer cells showed no statistically significant correlation with survival after surgery.

Conclusion: We have demonstrated that LGR5 is expressed in the cytoplasm of pancreatic adenocarcinoma cells, and the basolateral membrane of a subset of endocrine cells of the human pancreas. Further investigation is required to clarify any prognostic significance of LGR5 expression.

Knockdown of Oct4 and Nanog expression inhibits the stemness of pancreatic cancer cells

Pancreatic cancer is notorious for its difficult diagnosis at early stage and poor recurrence-free prognosis. This study aimed to investigate the possible involvement of Oct4 and Nanog in pancreatic cancer. The high expressions of Oct4 and Nanog in human pancreatic cancer tissues were found to indicate a worse prognostic value of patients. The pancreatic cancer stem cells (PCSCs) that isolated from PANC-1 cell line by flow cytometry exhibited high expressions of Oct4 and Nanog. To investigate whether Oct4 and Nanog play crucial role in maintaining the stemness of PCSCs, double knockdown of Oct4 and Nanog demonstrated that Oct4 and Nanog significantly reduced proliferation, migration, invasion, chemoresistance, and tumorigenesis of PCSCs in vitro and in vivo. The altered expression of the genes related to pancreatic carcinogenesis, metastasis, drug resistance and epithelial-mesenchymal transdifferentiation (EMT) might affect the biological characteristics of PCSCs. Our results suggest that Oct4 and Nanog may serve as a potential marker of prognosis and a novel target of therapy for pancreatic cancer.