Shereen Keleg

Invasion and metastasis in pancreatic cancer.

Pancreatic cancer remains a challenging disease with an overall cumulative 5-year survival rate below 1%. The process of cancer initiation, progression and metastasis is still not understood well. Invasion and tumor metastasis are closely related and both occur within a tumour-host microecology, where stroma and tumour cells exchange enzymes and cytokines that modify the local extracellular matrix, stimulate cell migration, and promote cell proliferation and tumor cell survival. During the last decade considerable progress has been made in understanding genetic alterations of genes involved in local and systemic tumor growth. The most important changes occur in genes which regulate cell cycle progression, extracellular matrix homeostasis and cell migration. Furthermore, there is growing evidence that epigenetic factors including angiogenesis and lymphangiogenesis may participate in the formation of tumor metastasis. In this review we highlight the most important genetic alterations involved in tumor invasion and metastasis and further outline the role of tumor angiogenesis and lymphangiogenesis in systemic tumor dissemination.

Indian hedgehog signaling pathway: Expression and regulation in pancreatic cancer

Pancreatic cancer is an aggressive malignancy that exhibits a number of genetic and epigenetic alterations. Indian hedgehog (Ihh) and its 2 signaling receptors, patched (Ptc) and smoothened (Smo), are involved in pancreatic development and regulation of β‐cell function as well as in certain human tumors. In the current study, we analyzed the expression, distribution and function of Ihh and its receptors in pancreatic cancer. Quantitative RT‐PCR and immunohistochemistry were utilized to analyze the expression, localization and transcriptional regulation of Ihh, Ptc and Smo. The effects of inhibition and stimulation of the hedgehog signaling pathway on pancreatic cancer cell growth were examined by the MTT cell growth assay. By quantitative RT‐PCR, Ihh, Ptc and Smo mRNA levels were increased 35‐, 1.2‐ and 1.6‐fold, respectively, in pancreatic cancer tissues in comparison to normal pancreatic tissues. By immunohistochemistry, Ihh, Ptc and Smo were expressed in the islet cells of normal and cancerous tissues and in pancreatic cancer cells. The growth of pancreatic cancer cells was dose‐dependently inhibited by the hedgehog antagonist cyclopamine through G0/G1 arrest. In contrast, Ihh agonists exhibited no significant effect on pancreatic cancer cell growth. TGF‐β1 repressed Ihh transcription in a TGF‐β1‐responsive pancreatic cancer cell line, but had no effect on the other tested cell lines. In conclusion, Ihh and its receptors Ptc and Smo are expressed in pancreatic cancer, and blockage of hedgehog signaling results in inhibition of pancreatic cancer cell growth, suggesting that aberrant activation of the Ihh signaling pathway contributes to tumor development in this malignancy.

Adrenomedullin is induced by hypoxia and enhances pancreatic cancer cell invasion.

Adrenomedullin (ADM) is synthesized by different types of cells and acts by binding calcitonin receptor‐like receptor (CRLR) and members of the receptor activity‐modifying protein (RAMP) family. In this study, the expression and functional role of ADM and its signaling components were investigated in pancreatic adenocarcinoma (PDAC). By QRT‐PCR, median mRNA levels of ADM and CRLR were 1.5‐ and 2.4‐fold higher, respectively, in PDAC tissues compared to normal pancreatic tissues. By immunohistochemistry, ADM, CRLR, RAMP1 and RAMP2, but not RAMP3, were expressed in pancreatic cancer cells. ADM serum levels were significantly increased in PDAC patients compared to healthy controls and chronic pancreatitis (CP) patients, with an area under the ROC curve of 0.83 and 0.98, respectively. At a cut‐off level of 30.6 ng/ml, the specificity of ADM to differentiate PDAC from controls and CP patients was 85.5 and 83.6%, with a sensitivity of 80 and 100%. All 5 evaluated pancreatic cancer cells lines expressed ADM, CRLR, RAMP1 and RAMP2, whereas RAMP3 was expressed in only 1/5 pancreatic cancer cell lines. ADM was strongly induced by hypoxia and significantly increased invasiveness in 3/5 human pancreatic cancer cells. Blocking of CRLR decreased invasiveness in 4/5 human pancreatic cancer cells. In addition, rADM slightly up‐regulated vascular endothelial growth factor secretion in 3/5 cell lines. In conclusion, ADM is induced by hypoxia and over‐expressed in PDAC and might therefore serve as a potential tumor marker. Furthermore, ADM increases invasiveness of some pancreatic cancer cells and might influence angiogenesis, suggesting that blocking this pathway might have a therapeutic potential.

FXYD3 is overexpressed in pancreatic ductal adenocarcinoma and influences pancreatic cancer cell growth

The expression and localization of FXYD domain containing ion transport regulator 3 (FXYD3), a transmembrane protein that acts as a chloride channel or chloride channel regulator, was analyzed in pancreatic tissues derived from donors and patients suffering from chronic pancreatitis (CP) or pancreatic ductal adenocarcinoma (PDAC) as well as in pancreatic cancer cells using QRT‐PCR, laser‐capture microdissection and microarray analysis, in situ hybridization and immunohistochemistry. FXYD3 antisense expressing T3M4 pancreatic cancer cells were generated and compared to control cells using anchorage‐dependent and independent growth assays, and xenotransplantation into nude mice. FXYD3 mRNA levels were 3.4‐fold increased in PDAC tissues compared to donor specimens (p = 0.006), and 3.9‐fold increased in microdissected cancer cells compared to normal pancreatic ductal cells (p = 0.02). FXYD3 was localized in the tubular complexes and PanIN lesions of both CP and PDAC, as well as in pancreatic cancer cells. Downregulation of FXYD3 by stable antisense transfection increased significantly the doubling time of T3M4 pancreatic cancer cells from 44 ± 2 hr to 55 ± 12 hr (p = 0.02). Nude mice transplanted with antisense transfected cells displayed a significant increase in tumor doubling time from 3.3 days ± 1.0 to 4.3 days ± 0.43 (p = 0.058). Anchorage‐independent growth and sensitivity to 5‐fluorouracil, gemcitabine and cisplatin as well as to MgCl2 were not dependent on the level of FXYD3 expression. In conclusion, overexpression of FXYD3 in pancreatic cancer may contribute to the proliferative activity of this malignancy.

Regulation and functional role of the Runt-related transcription factor-2 in pancreatic cancer

Recent evidence suggests that Runt-related transcription factors play a role in different human tumours. In the present study, the localisation of the Runt-related transcription factor-2 (Runx2), its transcriptional activity, as well as its regulation of expression was analysed in human pancreatic ductal adenocarcinoma (PDAC). Quantitative real-time PCR and immunohistochemistry were used for Runx2 expression and localisation analysis. Runt-related transcription factor-2 expression was silenced using specific siRNA oligonucleotides in pancreatic cancer cells (Panc-1) and immortalised pancreatic stellate cells (IPSCs). Overexpression of Runx2 was achieved using a full-length expression vector. TGF-β1, BMP2, and other cytokines were assessed for their potential to regulate Runx2 expression. There was a 6.1-fold increase in median Runx2 mRNA levels in PDAC tissues compared to normal pancreatic tissues (P<0.0001). Runt-related transcription factor-2 was localised in pancreatic cancer cells, tubular complexes, and PanIN lesions of PDAC tissues as well as in tumour-associated fibroblasts/stellate cells. Coculture of IPSCs and Panc-1 cells, as well as treatment with TGF-β1 and BMP2, led to increased Runx2 expression in Panc-1 cells. Runt-related transcription factor-2 overexpression was associated with decreased MMP1 release as well as decreased growth and invasion of Panc-1 cells. These effects were reversed by Runx2 silencing. In conclusion, Runx2 is overexpressed in PDAC, where it is regulated by certain cytokines such as TGF-β1 and BMP2 in an auto- and paracrine manner. In addition, Runx2 has the potential to regulate the transcription of extracellular matrix modulators such as SPARC and MMP1, thereby influencing the tumour microenvironment.

Actinin-4 expression in primary and metastasized pancreatic ductal adenocarcinoma.

Objectives: Actinin-4 is an actin-bundling protein that probably has a tumor-promoting potential in several solid tumors. The present study analyzed the expression of actinin-4 in the pancreas, in localized and metastasized pancreatic ductal adenocarcinoma (PDAC), and the correlation with clinical outcome. Methods: Pancreatic ductal adenocarcinoma tissue from 38 patients, 15 lymph node and 10 liver metastases, normal pancreas, and 4 PDAC cell lines, were examined by immunohistochemistry, and actinin-4 expression was quantified by immunofluorescence analysis. Results: In the normal pancreas, actinin-4 was most prominently expressed in ductal cells. In PDAC, tumor cells exhibited strong but differential cytoplasmic immunoreactivity for actinin-4. A multivariate analysis revealed actinin-4 immunoreactivity, advanced age, and undifferentiated grade as significant prognostic factors associated with worse survival after PDAC resection. Cells metastasized to lymph nodes or to the liver exhibited no significant increase of actinin-4 compared with the primary tumors. A nuclear staining was observed neither in any of the PDAC samples nor in the 4 cell lines. In PDAC cells, actinin-4 localized to dynamic actin structures and to invadopodia. Conclusions: Actinin-4 expression levels significantly correlate with worse survival after PDAC resection. Although actinin-4 has been reported to promote lymph node metastases, there was no enhanced expression in PDAC metastases.

Localization of the human hedgehog-interacting protein (Hip) in the normal and diseased pancreas

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with a poor prognosis. Previously, it has been shown that Indian hedgehog (Ihh) and its two signaling receptors patched (Ptc) and smoothened (Smo) are involved in the pathogenesis of chronic pancreatitis (CP) and PDAC. In the current study we analyzed the expression, distribution, and function of another component of this signaling pathway, the human hedgehog‐interacting protein (Hip), in the normal pancreas, CP and PDAC utilizing real‐time quantitative reverse transcription‐polymerase chain reaction (QRT‐PCR), immunohistochemistry, immunofluorescence, Hip siRNA transfection, cell growth assays, and cell cycle analysis. By QRT‐PCR, Hip mRNA levels were fifteenfold and fourteenfold increased in CP (nu2009=u200922) and PDAC (nu2009=u200931) tissues, respectively, compared to normal pancreatic tissues (n=20) and correlated with glioma associated antigen (Gli1) but not Ptc or Protein kinase A (PKA) mRNA levels. Only SU‐8686 and BxPC‐3 pancreatic cancer cells expressed Hip mRNA, whereas expression was below the level of detection in the other six pancreatic cancer cell lines tested. As shown by immunohistochemistry, Hip was expressed in normal pancreatic tissues mainly in the cytoplasm of islet cells and in smooth muscle cells of blood vessels. In contrast, in CP and PDAC there was a different distribution and staining intensity within the islets. Moreover, Hip immunoreactivity was observed in the tubular complexes, PanIN 1–3 lesions, as well as in pancreatic cancer cells. Incubation of pancreatic cancer cell lines with recombinant Hip revealed a growth inhibitory effect in SU‐8686 and Capan‐1 pancreatic cancer cells and no effect on cell growth in the other tested cell lines. In addition, silencing of Hip expression using specific siRNA molecules increased the growth of SU‐8686 cells. In conclusion, Hip is expressed in the normal pancreas, CP and PDAC tissues. The different pattern of Hip expression and abnormal localization in the diseased pancreas suggest that the enhanced activation of hedgehog signaling in CP and PDAC is—at least in part—due to the aberrant responsiveness and expression of Hip in these diseases.

Establishment and Characterization of a Highly Tumourigenic and Cancer Stem Cell Enriched Pancreatic Cancer Cell Line as a Well Defined Model System

Standard cancer cell lines do not model the intratumoural heterogeneity situation sufficiently. Clonal selection leads to a homogeneous population of cells by genetic drift. Heterogeneity of tumour cells, however, is particularly critical for therapeutically relevant studies, since it is a prerequisite for acquiring drug resistance and reoccurrence of tumours. Here, we report the isolation of a highly tumourigenic primary pancreatic cancer cell line, called JoPaca-1 and its detailed characterization at multiple levels. Implantation of as few as 100 JoPaca-1 cells into immunodeficient mice gave rise to tumours that were histologically very similar to the primary tumour. The high heterogeneity of JoPaca-1 was reflected by diverse cell morphology and a substantial number of chromosomal aberrations. Comparative whole-genome sequencing of JoPaca-1 and BxPC-3 revealed mutations in genes frequently altered in pancreatic cancer. Exceptionally high expression of cancer stem cell markers and a high clonogenic potential in vitro and in vivo was observed. All of these attributes make this cell line an extremely valuable model to study the biology of and pharmaceutical effects on pancreatic cancer.

Comparative analysis of tumorbiology and CD133 positivity in primary and recurrent pancreatic ductal adenocarcinoma

In over 70% of the cases, patients with curative surgery and adjuvant chemotherapy for pancreatic ductal adenocarcinoma (PDAC) develop recurrent tumors. The cancer stem cell (CSC) hypothesis suggests that CSCs are chemoresistant and enriched in recurrent tumors. This study analyzes tumorbiology, expression of the metastasis-promoting CXCR4 and actinin-4, and of the CSC marker CD133 in primary and recurrent PDAC. Twenty-six patients underwent resection for primary and recurrent PDAC and most developed tumor recurrence within 2xa0years. In 81% the histologic tumor grade was unchanged. Immunohistochemistry could be performed with 15 pairs of primary and recurrent PDAC. The mean Ki-67 proliferation index increased (Pxa0=xa00.06). About 30% of tumor cells were positive for CXCR4 and almost all tumor cells expressed actinin-4, but there were neither significant changes in the expression levels in recurrent PDAC, nor specifically enhanced levels in metastases. The prominent CD133 pattern was an apical membrane staining of inflammatorily altered, non-neoplastic ductal structures equally observed in primary and recurrent PDAC. The membrane CD133 positivity was consistently absent in neoplastic PDAC cells. Cytoplasmic CD133 positivity was extremely rare (0.85 and 0.34 cells/cm2 in primary and recurrent PDAC, respectively; Pxa0=xa00.07). Tumor grade is mainly unchanged and the expression of CXCR4, actinin-4 and CD133 are not enhanced in recurrent PDAC. The apical membrane CD133 positivity of normal and inflammatorily altered ductal structures and its lack in tumor cells bring the role of CD133 as a specific CSC marker in PDAC into question.

BGLAP is expressed in pancreatic cancer cells and increases their growth and invasion

BackgroundBone gamma-carboxyglutamate protein (BGLAP; osteocalcin) is a small, highly conserved molecule first identified in the mineralized matrix of bone. It has been implicated in the pathophysiology of various malignancies. In this study, we analyzed the expression and role of BGLAP in the normal human pancreas, chronic pancreatitis (CP), and pancreatic ductal adenocarcinoma (PDAC) using quantitative RT-PCR, immunohistochemistry, immunocytochemistry and enzyme immunoassays, as well as cell proliferation and invasion assays. Gene silencing was carried out using specific siRNA molecules.ResultsCompared to the normal pancreas, BGLAP mRNA and protein levels were not significantly different in CP and PDAC tissues. BGLAP was faintly present in the cytoplasm of normal acinar cells but was strongly expressed in the cytoplasm and nuclei of tubular complexes and PanIN lesions of CP and PDAC tissues. Furthermore, BGLAP expression was found in the cancer cells in PDAC tissues as well as in 4 cultured pancreatic cancer cell lines. TNFalpha reduced BGLAP mRNA and protein expression levels in pancreatic cancer cell lines. In addition, BGLAP silencing led to reduction of both cell growth and invasion in those cells.ConclusionBGLAP is expressed in pancreatic cancer cells, where it potentially increases pancreatic cancer cell growth and invasion through autocrine and/or paracrine mechanisms.