Background & Aims As in other tumor types, progression of pancreatic cancer may require a functionally unique population of cancer stem cells. Although such cells have been identified in many invasive cancers, is not clear whether they emerge during early or late stages of tumorigenesis. Using mouse models and human pancreatic cancer cell lines, we investigated whether pre-invasive pancreatic neoplasia contains a subpopulation of cells with distinct morphologies and cancer stem cell-like properties. Methods Pancreatic tissue samples were collected from the KCPdx1, KPCPdx1, and KCiMist1 mouse models of pancreatic intraepithelial neoplasia (PanIN) and analyzed by confocal and electron microscopy, lineage tracing, and fluorescence-activated cell sorting. Subpopulations of human PDAC cells were similarly analyzed and also used in cDNA microarray analyses. Results The microtubule regulator DCLK1 marked a morphologically distinct and functionally unique population of pancreatic cancer-initiating cells. These cells displayed morphologic and molecular features of gastrointestinal tuft cells. Cells that expressed DCLK1 also expressed high levels of ATAT1, HES1, HEY1, IGF1R, and ABL1, and manipulation of these pathways in PDAC cell lines inhibited their clonogenic potential. Pharmacologic inhibition of γ–secretase activity reduced the abundance of these cells in murine PanIN, in a manner that correlated with inhibition of PanIN progression. Conclusions Human PDAC cells and pancreatic neoplasms in mice contain morphologically and functionally distinct subpopulations that have cancer stem cell-like properties. These populations can be identified at the earliest stages of pancreatic tumorigenesis, and provide new cellular and molecular targets for pancreatic cancer treatment and/or chemoprevention.

BackgroundThe complexity and heterogeneity of the human plasma proteome have presented significant challenges in the identification of protein changes associated with tumor development. Refined genetically engineered mouse (GEM) models of human cancer have been shown to faithfully recapitulate the molecular, biological, and clinical features of human disease. Here, we sought to exploit the merits of a well-characterized GEM model of pancreatic cancer to determine whether proteomics technologies allow identification of protein changes associated with tumor development and whether such changes are relevant to human pancreatic cancer.Methods and FindingsPlasma was sampled from mice at early and advanced stages of tumor development and from matched controls. Using a proteomic approach based on extensive protein fractionation, we confidently identified 1,442 proteins that were distributed across seven orders of magnitude of abundance in plasma. Analysis of proteins chosen on the basis of increased levels in plasma from tumor-bearing mice and corroborating protein or RNA expression in tissue documented concordance in the blood from 30 newly diagnosed patients with pancreatic cancer relative to 30 control specimens. A panel of five proteins selected on the basis of their increased level at an early stage of tumor development in the mouse was tested in a blinded study in 26 humans from the CARET (Carotene and Retinol Efficacy Trial) cohort. The panel discriminated pancreatic cancer cases from matched controls in blood specimens obtained between 7 and 13 mo prior to the development of symptoms and clinical diagnosis of pancreatic cancer.ConclusionsOur findings indicate that GEM models of cancer, in combination with in-depth proteomic analysis, provide a useful strategy to identify candidate markers applicable to human cancer with potential utility for early detection.

The incidence of cholangiocellular carcinoma (CCC) is increasing worldwide. Using a transgenic mouse model, we found that expression of the intracellular domain of Notch 1 (NICD) in mouse livers results in the formation of intrahepatic CCCs. These tumors display features of bipotential hepatic progenitor cells, indicating that intrahepatic CCC can originate from this cell type. We show that human and mouse CCCs are characterized by high expression of the cyclin E protein and identified the cyclin E gene as a direct transcriptional target of the Notch signaling pathway. Intriguingly, blocking γ-secretase activity in human CCC xenotransplants results in downregulation of cyclin E expression, induction of apoptosis, and tumor remission in vivo.

Background & Aims The Notch signaling pathway is required for the expansion of undifferentiated pancreatic progenitor cells during embryonic development and has been implicated in the progression of pancreatic ductal adenocarcinoma (PDAC). The interaction of Notch ligands with their receptors promotes a γ-secretase-dependent cleavage of the Notch receptor and release of the Notch intracellular domain, which translocates to the nucleus and activates transcription. We investigated the role of this pathway in PDAC progression. Methods We tested the effects of a γ-secretase inhibitor (GSI) that blocks Notch signaling in PDAC cell lines and a genetically engineered mouse model of PDAC (Kras p53 L/+ mice). Results Notch signaling was activated in PDAC precursors and advanced tumors. The GSI inhibited the growth of premalignant pancreatic duct-derived cells in a Notchdependent manner. Additionally, in a panel of over 400 human solid tumor-derived cell lines, PDAC cells, as a group, were more sensitive to the GSI than any other tumor type. Finally, the GSI completely inhibited tumor development in the genetically engineered model of invasive PDAC (p<0.005 χ2 test; compared with mice exposed to vehicle). Conclusions These results suggest that Notch signaling is required for PDAC progression. Pharmacologic targeting of this pathway offers therapeutic potential in this treatment-refractory malignancy.

The urine test differentiates CC from PSC and other BBD and may provide a new diagnostic non-invasive tool for PSC surveillance and CC detection.

The telomere hypothesis of cancer initiation indicates that telomere shortening initiates cancer by induction of chromosomal instability. To test whether this hypothesis applies to human hepatocellular carcinoma (HCC), we analyzed the telomere length of hepatocytes in cytological smears of fine-needle biopsies of liver tumors from patients with cirrhosis (n ‫؍‬ 39). The tumors consisted of 24 HCC and 15 regenerative nodules as diagnosed by combined histological and cytological diagnostics. In addition, we analyzed the telomere length of hepatocytes in HCC and surrounding noncancerous liver tissue within individual patients in another cohort of 10 patients with cirrhosis. Telomere length analysis of hepatocytes was correlated with tumor pathology and ploidy grade of the tumors, which was analyzed by cytophotometry. Telomeres were significantly shortened in hepatocytes of HCC compared to hepatocytes in regenerative nodules or surrounding noncancerous liver tissue. Hepatocyte telomere shortening in HCC was independent of the patient's age. There was no overlap in mean telomere lengths of individual samples when comparing HCC with regenerative nodules or noncancerous surrounding liver. Within the HCC group, telomeres were significantly shorter in hepatocytes of aneuploid tumors compared to diploid tumors. In conclusion, our data suggest that the telomere hypothesis of cancer initiation applies to human HCC and that cell type-specific telomere length analysis might indicate the risk of HCC development. (HEPATOLOGY 2004;40:80 -86.) L iver cirrhosis is the major risk factor for the development of hepatocellular carcinoma (HCC), and the incidence of HCC in cirrhotic patients is 3% to 6% annually. 1-3 One of the common features of human epithelial cancer is the prevalence of chromosomal instability (CIS). 4 As in other epithelial cancers, HCCs show a high incidence of CIS. 5 A current hypothesis is that telomere shortening and loss of telomere function play a role in the induction of CIS. 6,7 The main function of telomeres is the capping of chromosomal ends. 8 Due to the "end-replication problem" of DNA polymerase, telomeres shorten during each round of cell division. 9 Telomere shortening limits the proliferative capacity of primary human cells to a finite number of cell divisions 10 and appears to restrain the regenerative capacity of tissues and organs in aging and chronic diseases. 7 In the liver, hepatocyte telomere shortening has been linked to cirrhosis formation. 11 When telomeres reach a critically short length, they lose capping function, resulting in chromosomal fusions. 12 When cells with fused chromosomes enter the cell cycle, these fusions will be disrupted during mitosis, resulting in the breakage of chromosomes and chromosomal gains and losses. 13 This phenomenon has been termed the fusion-bridge-breakage cycle and might contribute to the induction of CIS and cancer in the aged. 13 In line with this hypothesis, the initiation of cancer is increased by telomere shortening in telomerase-deficient mice. 1...

Telomere shortening and inactivation of cell cycle checkpoints characterize carcinogenesis. Whether these molecular features coincide at specific stages of human hepatocarcinogenesis is unknown. The preneoplasia-carcinoma sequence of human HCC is not well defined. Small cell changes (SCC) and large cell changes (LCC) are potential precursor lesions. We analyzed hepatocellular telomere length, the prevalence of DNA damage, and the expression of p21 and p16 in biopsy specimens of patients with chronic liver disease (n ‫؍‬ 27) that showed different precursor lesions and/or HCC: liver cirrhosis (n ‫؍‬ 25), LCC (n ‫؍‬ 26), SCC (n ‫؍‬ 13), and HCC (n ‫؍‬ 13). The study shows a decrease in telomere length in nondysplastic cirrhotic liver compared with normal liver and a further significant shortening of telomeres in LCC, SCC, and HCC. HCC had the shortest telomeres, followed by SCC and LCC. Hepatocytes showed an increased p21 labeling index (p21-LI) at the cirrhosis stage, which remained elevated in most LCC. In contrast, most SCC and HCC showed a strongly reduced p21-LI. Similarly, p16 was strongly expressed in LCC but reduced in SCC and not detectable in HCC. ␥H2AX-DNA-damage-foci were not detected in LCC but were present in SCC and more frequently in HCC. These data indicate that LCC and SCC represent clonal expansions of hepatocytes with shortened telomeres. Conclusion: The inactivation of cell cycle checkpoints coincides with further telomere shortening and an accumulation of DNA damage in SCC and HCC, suggesting that SCC represent more advanced precursor lesions compared with LCC. (HEPATOLOGY 2007;45:968-976.) H CC represents the fifth most common neoplasm in humans. 1 Treatment options for HCC patients are limited, and the disease is often diagnosed at an advanced stage. 2 The molecular pathogenesis of hepatocarcinogenesis is poorly understood, 3 thus impairing the development of molecular markers, efficient screening procedures, and molecular therapies.HCC rarely evolve in noncirrhotic liver but the risk sharply increases at the cirrhosis stage of chronic liver diseases, with the yearly incidence of HCC ranging from Gastroenterology, Hepatology, and Endocrinology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany. E-mail: Rudolph.Lenhard@MH-hannover.de; fax: 0049-511-532-6998, or to: Massimo Roncalli, Department of Pathology, University of Milan and IRCCS Humanitas Clinical Institute, Via Manzoni 56, 20089 Rozzano (Milan), Italy. E-mail: massimo.roncalli@unimi.it; fax: 0039-02-82244791. Copyright © 2007 (2) small cell changes/dysplasia (SCC). 13,14 Whether both of these lesions represent true precursor lesions and which of these precursors is more closely related to HCC are intensely debated. [7][8][9][10][11][12] On the molecular level, HCC are characterized by massive chromosomal instability (CIN) in more than 95% of cases, 15-17 and telomere shortening 18,19 and loss of p53-checkpoint function in more than 70% of the cases. 3,20 Experimental data from telomerase-deficient mic...

Telomere dysfunction induces two types of cellular response: cellular senescence and apoptosis. We analysed the extent to which the cellular level of telomere dysfunction and p53 gene status affect these cellular responses in mouse liver using the experimental system of TRF2 inhibition by a dominant-negative version of the protein (TRF2 DBDM ). We show that the level of telomere dysfunction correlates with the level of TRF2 DBDM protein expression resulting in chromosomal fusions, aberrant mitotic figures and aneuploidy of liver cells. These alterations provoked p53-independent apoptosis, but a strictly p53-dependent senescence response in distinct populations of mouse liver cells depending on the cellular level of TRF2 DBDM expression. Apoptosis was associated with higher expression of TRF2 DBDM , whereas cellular senescence was associated with low levels of TRF2 DBDM expression. Our data provide experimental evidence that induction of senescence or apoptosis in vivo depends on the cellular level of telomere dysfunction and differentially on p53 gene function.