Inhibition of Hedgehog signaling enhances delivery of chemotherapy in a mouse model of pancreatic cancer

KRAS, Hedgehog, Wnt and the twisted developmental biology of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterized by near-universal mutations in KRAS and frequent deregulation of crucial embryonic signalling pathways, including the Hedgehog (Hh) and Wnt-β-catenin cascades. The creation of mouse models that closely resemble the human disease has provided a platform to better understand when and in which cell types these pathways are misregulated during PDAC development. Here we examine the central part that KRAS plays in the biology of PDAC, and how the timing and location of Hh and Wnt-β-catenin signalling dictate the specification and oncogenic properties of PDAC.

The extracellular matrix in digestive cancer

The extracellular components of the cancer microenvironment play a critical role in tumor initiation, progression and invasion. In this review we examine the normal formation and function of the basement membrane and extracellular matrix. We characterize the interactions between the matrix and the epithelium and explore the causes and consequences of the extracellular remodeling that accompanies carcinogenesis. Finally, we address the therapeutic possibilities of incorporating matrix as well as epithelial strategies in the management of digestive cancer.

Delivering nanomedicine to solid tumors

Recent advances in nanotechnology have offered new hope for cancer detection, prevention, and treatment. While the enhanced permeability and retention effect has served as a key rationale for using nanoparticles to treat solid tumors, it does not enable uniform delivery of these particles to all regions of tumors in sufficient quantities. This heterogeneous distribution of therapeutics is a result of physiological barriers presented by the abnormal tumor vasculature and interstitial matrix. These barriers are likely to be responsible for the modest survival benefit offered by many FDA-approved nanotherapeutics and must be overcome for the promise of nanomedicine in patients to be realized. Here, we review these barriers to the delivery of cancer therapeutics and summarize strategies that have been developed to overcome these barriers. Finally, we discuss design considerations for optimizing the delivery of nanoparticles to tumors.

Interaction of stellate cells with pancreatic carcinoma cells

Pancreatic cancer is characterized by its late detection, aggressive growth, intense infiltration into adjacent tissue, early metastasis, resistance to chemo- and radiotherapy and a strong “desmoplastic reaction”. The dense stroma surrounding carcinoma cells is composed of fibroblasts, activated stellate cells (myofibroblast-like cells), various inflammatory cells, proliferating vascular structures, collagens and fibronectin. In particular the cellular components of the stroma produce the tumor microenvironment, which plays a critical role in tumor growth, invasion, spreading, metastasis, angiogenesis, inhibition of anoikis, and chemoresistance. Fibroblasts, myofibroblasts and activated stellate cells produce the extracellular matrix components and are thought to interact actively with tumor cells, thereby promoting cancer progression. In this review, we discuss our current understanding of the role of pancreatic stellate cells (PSC) in the desmoplastic response of pancreas cancer and the effects of PSC on tumor progression, metastasis and drug resistance. Finally we present some novel ideas for tumor therapy by interfering with the cancer cell-host interaction.

Half-antibody functionalized lipid-polymer hybrid nanoparticles for targeted drug delivery to carcinoembryonic antigen presenting pancreatic cancer cells

Current chemotherapy regimens against pancreatic cancer are met with little success as poor tumor vascularization significantly limits the delivery of oncological drugs. High-dose targeted drug delivery, through which a drug delivery vehicle releases a large payload upon tumor localization, is thus a promising alternative strategy against this lethal disease. Herein, we synthesize anti-carcinoembryonic antigen (CEA) half-antibody conjugated lipid-polymer hybrid nanoparticles and characterize their ligand conjugation yields, physicochemical properties, and targeting ability against pancreatic cancer cells. Under the same drug loading, the half-antibody targeted nanoparticles show enhanced cancer killing effect compared to the corresponding nontargeted nanoparticles.

Dynamic interplay between the collagen scaffold and tumor evolution

The extracellular matrix (ECM) is a key regulator of cell and tissue function. Traditionally, the ECM has been thought of primarily as a physical scaffold that binds cells and tissues together. However, the ECM also elicits biochemical and biophysical signaling. Controlled proteolysis and remodeling of the ECM network regulate tissue tension, generate pathways for migration, and release ECM protein fragments to direct normal developmental processes such as branching morphogenesis. Collagens are major components of the ECM of which basement membrane type IV and interstitial matrix type I are the most prevalent. Here we discuss how abnormal expression, proteolysis and structure of these collagens influence cellular functions to elicit multiple effects on tumors, including proliferation, initiation, invasion, metastasis, and therapy response.

Immunogenicity of SEREX-identified antigens and disease outcome in pancreatic cancer

Despite spontaneous or vaccination-induced immune responses, pancreatic cancer remains one of the most deadly immunotherapy-resistant malignancies. We sought to comprehend the spectrum of pancreatic tumor-associated antigens (pTAAs) and to assess the clinical relevance of their immunogenicity. An autologous SEREX-based screening of a cDNA library constructed from a pancreatic T3N0M0/GIII specimen belonging to a long-term survivor (36 months) revealed 18 immunogenic pTAA. RT-PCR analysis displayed broad distribution of the identified antigens among normal human tissues. PNLIPRP2 and MIA demonstrated the most distinct pancreatic cancer-specific patterns. ELISA-based screening of sera for corresponding autoantibodies revealed that although significantly increased, the immunogenicity of these molecules was not a common feature in pancreatic cancer. QRT-PCR and immunohistochemistry characterized PNLIPRP2 as a robust acinar cell-specific marker whose decreased expression mirrored the disappearance of parenchyma in the diseased organ, but was not related to the presence of PNLIPRP2 autoantibodies. Analyses of MIA-known to be preferentially expressed in malignant cells-surprisingly revealed an inverse correlation between intratumoral gene expression and the emergence of autoantibodies. MIA(high) patients were autoantibody-negative and had shorter median survival when compared with autoantibody-positive MIA(low) patients (12 vs. 34 months). The observed pTAA spectrum comprised molecules associated with acinar, stromal and malignant structures, thus presenting novel targets for tumor cell-specific therapies as well as for approaches based on the bystander effects. Applying the concept of cancer immunoediting to interpret relationships between gene expression, antitumor immune responses, and clinical outcome might better discriminate between past and ongoing immune responses, consequently enabling prognostic stratification of patients and individual adjustment of immunotherapy.

Tumors as organs: complex tissues that interface with the entire organism

Solid tumors are not simply clones of cancer cells. Instead, they are abnormal organs composed of multiple cell types and extracellular matrix. Some aspects of tumor development resemble processes seen in developing organs, whereas others are more akin to tissue remodeling. Some microenvironments, particularly those associated with tissue injury, are favorable for progression of mutant cells, whereas others restrict it. Cancer cells can also instruct surrounding tissues to undergo changes that promote malignancy. Understanding the complex ways in which cancer cells interact with their surroundings, both locally in the tumor organ and systemically in the body as a whole, has implications for effective cancer prevention and therapy.

Cyclopamine and hedgehog signaling: chemistry, biology, medical perspectives

When Odysseus left the devastated city of Troy after ten years of siege he could not foresee the perils he still had to face. The encounter with the cyclops, a giant with only one eye placed in the middle of its forehead, was doubtlessly one of the creepiest and most dangerous of his adventures. In the end, Odysseus could only escape with the help of a sheep. Whether Homers cyclops was inspired by the observation of terribly malformed neonates remains speculative. However, when sheep herders in Idaho in the middle of the 20th century faced an increasing number of cyclops-like sheep in their herds, a unique cascade of chemical, biological, and medicinal discoveries was initiated. This Minireview tells this story and shows its impact on modern biomedical research.

Stromal CD10 and SPARC expression in ductal carcinoma in situ (DCIS) patients predicts disease recurrence

The current classification of ductal carcinoma in situ (DCIS) is based on nuclear grade, architectural differentiation and the presence of necrosis that does not adequately predict the likelihood of recurrence after breast conserving therapy; therefore, there is a critical need to identify novel predictors of DCIS progression. Ninety seven cases of DCIS were included in the study. CD10 and SPARC expression in tumor stroma was assessed by standard immunoperoxidase method with ani-CD 10 and anti-SPARC antibodies. The staining was scored semi-quantitatively as negative, weak or strong. Statistical analysis was performed using the Fisher's exact test. Multivariable analysis was conducted utilizing Exact Logistic Regression software (SAS 9.1 and LogExact). A significant association was observed between the recurrence status and time to recurrence with expression of CD10 (p < 0.001) and SPARC (p < 0.001). When combining both SPARC and CD10 expression there was a strong correlation with the shortest time to recurrence. Stromal CD10 and SPARC expression are new markers of an increased risk for DCIS recurrence, independent of commonly assessed clinical parameters. Thus, stromal CD10 and SPARC expression levels are promising markers of DCIS recurrence and warrant evaluation in larger prospective studies.

The marine compound spongistatin 1 targets pancreatic tumor progression and metastasis

Treatment of pancreatic cancer remains a major challenge and new anticancer drugs are urgently required. Our study presents the marine natural compound spongistatin 1 as a promising experimental drug. Spongistatin 1 was applied in an orthotopic in vivo model of human pancreatic cancer. Spongistatin 1 significantly reduced tumor growth, which correlates with a strong apoptosis induction (DNA-fragmentation) and long-term effects on clonogenic survival of pancreatic tumor cells (L3.6pl) in vitro. In addition, the formation of metastasis was reduced in spongistatin 1-treated mice, which is in line with a diminished MMP-9 activity in tumor tissue determined by zymography. Based on the pronounced efficacy of spongistatin 1, the underlying mechanisms were studied in more detail. In vitro adhesion, as well as migration, and invasion assays showed spongistatin 1 to influence these critical steps in the metastatic cascade. Furthermore, spongistatin 1 induced anoikis in L3.6pl cells. Exposure to spongistatin 1 leads to phosphorylation, and thus inactivation of the antiapoptotic protein Bcl-2 in pancreatic tumor cells. siRNA experiments silencing Bcl-2 suggest a role of Bcl-2 in anoikis and cell migration. Taken together, spongistatin 1 not only proved to be a potent experimental drug but also served as a chemical tool to examine the role of the antiapoptotic protein Bcl-2 in pancreas carcinoma, thereby supporting the hypothesis of a link between apoptosis signaling and metastasis.

The role of radiotherapy in locally advanced pancreatic carcinoma

The prognosis for locally advanced pancreatic carcinoma remains dismal despite advances in chemotherapy and radiotherapy over the past few decades. The use of radiotherapy for pancreatic carcinoma is often disputed because of the hypothesis that patients with pancreatic cancer die from distant metastases. It is well accepted that the greatest chance for cure of pancreatic cancer involves surgical resection of the primary tumor. However, there is much controversy about the role of radiotherapy in local disease control. The aim of this Review is to discuss data from the available studies, both prospective and retrospective, that evaluate treatment options for locally advanced pancreatic cancer. We focus on the benefits associated with local therapies, including radiotherapy and surgical resection, as they relate to improved local disease control, prolonged overall survival and improved symptom control.

Gemcitabine plus bevacizumab compared with gemcitabine plus placebo in patients with advanced pancreatic cancer: phase III trial of the Cancer and Leukemia Group B (CALGB 80303)

PURPOSE

The combination of gemcitabine plus bevacizumab produced a 21% response rate and a median survival of 8.8 months in a multicenter phase II trial in patients with metastatic pancreatic cancer. These encouraging data led Cancer and Leukemia Group B (CALGB) to conduct a double-blind, placebo-controlled, randomized phase III trial of gemcitabine/bevacizumab versus gemcitabine/placebo in advanced pancreatic cancer patients.

PATIENTS AND METHODS

Eligible patients had no prior therapy for advanced disease, Eastern Cooperative Oncology Group (ECOG) performance status 0 to 2, no tumor invasion of adjacent organs, and no increased bleeding risk. The primary end point was overall survival. Patients were stratified by performance status, extent of disease, and prior radiotherapy. Patients received gemcitabine at 1,000 mg/m(2) over 30 minutes on days 1, 8, and 15 every 28 days and bevacizumab at 10 mg/kg or placebo on days 1 and 15 every 28 days.

RESULTS

Between June 2004 and April 2006, 602 patients were enrolled onto the study and 535 were treated. Median overall survival was 5.8 months for gemcitabine/bevacizumab and 5.9 months for gemcitabine/placebo (P = .95). Median progression-free survival was 3.8 and 2.9 months, respectively (P = .07). Overall response rates were 13% and 10%, respectively. Patients with a performance status of 0, 1, and 2 survived a median of 7.9, 4.8, and 2.4 months, respectively. The only statistically significant differences in grades 3 and 4 toxicity occurred for hypertension (10% v 3%; P < .001) and proteinuria (5% v 1%; P = .002); venous thrombosis grade > or = 3 was equivalent in both arms (14% and 15%, respectively).

CONCLUSION

The addition of bevacizumab to gemcitabine does not improve survival in advanced pancreatic cancer patients.

Integrated preclinical and clinical development of mTOR inhibitors in pancreatic cancer

BACKGROUND

The purpose of this work was to determine the efficacy of inhibiting mammalian target of rapamycin (mTOR) in pancreatic cancer preclinical models and translate preclinical observations to the clinic.

METHODS

Temsirolimus (20 mg Kg(-1) daily) was administered to freshly generated pancreatic cancer xenografts. Tumour growth inhibition was determined after 28 days. Xenografts were characterised at baseline by gene expression and comparative genomic hybridisation. Patients with advanced, gemcitabine-resistant pancreatic cancer were treated with sirolimus (5 mg daily). The primary end point was 6-month survival rate (6mSR). Correlative studies included immunohistochemistry assessment of pathway expression in baseline tumours, drug pharmacokinetics (PKs), response assessment by FDG-PET and pharmacodynamic effects in peripheral-blood mononuclear cells (PBMCs).

RESULTS

In all, 4 of 17 xenografts (23%) responded to treatment. Sensitive tumours were characterised by gene copy number variations and overexpression of genes leading to activation of the PI3K/Akt/mTOR pathway. Activation of p70S6K correlated with drug activity in the preclinical studies. Sirolimus was well tolerated in the clinic, showed predictable PKs, exerted pathway inhibition in post-treatment PBMCs and resulted in a 6mSR of 26%. No correlation, however, was found between activated p70S6K in tumour tissues and anti-tumour effects.

CONCLUSION

Sirolimus activity in pancreatic cancer was marginal and not predicted by the selected biomarker.

Targeting Notch signaling in pancreatic cancer

IMPORTANCE OF THE FIELD

With some 220,000 new cases/year in the world, pancreatic adenocarcinoma is the fourth highest cause of death by cancers. Among newly diagnosed patients about 210,000 will die within 9 months following diagnosis. Therefore, effective adjuncts to current treatment strategies are necessary. Because embryological signaling pathways are upregulated in pancreatic adenocarcinoma, they represent potential targets for future therapies.

AREAS COVERED IN THIS REVIEW

Our aim is to present the Notch pathway, and to describe its involvement in pancreatic pathophysiology/carcinogenesis. This pathway appeared as a prime target for pancreatic cancer therapy. In the light of the crosstalk of Notch with other survival/embryologic pathways, drugs affecting more than one pathway may have to be combined.

WHAT THE READER WILL GAIN

Drugs against gamma-secretases could thus serve in cancer treatment and can be combined with drugs targeting survival pathways interplaying with Notch such as Hedgehog.

TAKE HOME MESSAGE

Downregulation of Notch contributes to the inhibition and apoptosis of pancreatic cancer cells whereas Hedgehog inhibition will allow for enhanced delivery of drugs to the tumor. Both pathway inhibitors appear to have synergistic effects for future therapeutics for pancreatic adenocarcinoma, once safety issues of compounds are overcome.

Modulators of the hedgehog signaling pathway

Since its discovery by C. Nüsslein-Volhard and E. F. Wieschaus, hedgehog (hh) signaling has come a long way. Today it is regarded as a key regulator in embryogenesis where it governs processes like cell proliferation, differentiation, and tissue patterning. Furthermore, in adults it is involved in the maintenance of stem cells, and in tissue repair and regeneration. But hh signaling has a second-much darker-face: it plays an important role in several types of human cancers where it promotes growth and enables proliferation of tumor stem cells. The etiology of medulloblastoma and basal cell carcinoma is tightly linked to aberrant hh activity, but also cancers of the prostate, the pancreas, the colon, the breasts, rhabdomyosarcoma, and leukemia, are dependent on irregular hh activity. Recent clinical studies have shown that hh signaling can be the basis of an important new class of therapeutic agents with far-reaching implications in oncology. Thus, modulation of hh signaling by means of small molecules has emerged as a valuable tool in combating these hh-dependent cancers. Cyclopamine, a unique natural product with a fascinating history, was the first identified inhibitor of hh signaling and its story is closely linked to the progress in the whole field. In this review we will trace the story of cyclopamine, give an overview on the biological modes of hh signaling both in untransformed and malignant cells, and finally present potent modulators of the hh pathway-many of them already in clinical studies. For more than 30 years now the knowledge on hh signaling has grown steadily-an end to this development is far from being conceivable.

Systemic administration of polymeric nanoparticle-encapsulated curcumin (NanoCurc) blocks tumor growth and metastases in preclinical models of pancreatic cancer

Curcumin or diferuloylmethane is a yellow polyphenol extracted from the rhizome of turmeric (Curcuma longa). A large volume (several hundreds) of published reports has established the anticancer and chemopreventative properties of curcumin in preclinical models of every known major cancer type. Nevertheless, the clinical translation of curcumin has been significantly hampered due to its poor systemic bioavailability, which mandates that patients consume up to 8 to 10 g of the free drug orally each day to achieve detectable levels in circulation. We have engineered a polymeric nanoparticle encapsulated curcumin formulation (NanoCurc) that shows remarkably higher systemic bioavailability in plasma and tissues compared with free curcumin upon parenteral administration. In xenograft models of human pancreatic cancer established in athymic mice, administration of parenteral NanoCurc significantly inhibits primary tumor growth in both subcutaneous and orthotopic settings. The combination of parenteral NanoCurc with gemcitabine results in enhanced tumor growth inhibition versus either single agent, suggesting an additive therapeutic influence in vivo. Furthermore, this combination completely abrogates systemic metastases in orthotopic pancreatic cancer xenograft models. Tumor growth inhibition is accompanied by significant reduction in activation of nuclear factor-kappaB, as well as significant reduction in expression of matrix metalloproteinase-9 and cyclin D1, in xenografts treated with NanoCurc and gemcitabine. NanoCurc is a promising new formulation that is able to overcome a major impediment for the clinical translation of curcumin to cancer patients by improving systemic bioavailability, and by extension, therapeutic efficacy.

Genetics of biliary tract cancers and emerging targeted therapies

Biliary tract cancers (BTC), which encompass intra- and extrahepatic cholangiocarcinomas and gallbladder carcinomas, are a genetically diverse collection of cancers. Evidence suggests distinct models of molecular and pathologic progression, and a growing body of genetics data points to a heterogeneous collection of underlying mutations in key oncogenes and tumor suppressor genes. Although tumor genetics have been used to tailor individual treatment regimens and guide clinical decision making in other cancers, these principles have not been applied in BTC. Recent clinical trials with targeted therapies seem promising, although the relationships between subsets of patients with positive responses to therapy and tumor genetics remain unexplored. Here, we summarize the molecular pathogenesis and genetics of BTCs and animal modeling and relate these to recent and ongoing clinical trials with targeted agents.

Functional magnetic resonance imaging in an animal model of pancreatic cancer

AIM

To test the hypotheses that diffusion weighed (DW)- and transcatheter intraarterial perfusion (TRIP)-magnetic resonance imaging (MRI) can each be used to assess regional differences in tumor function in an animal pancreatic cancer model.

METHODS

VX2 tumors were implanted in pancreata of 6 rabbits. MRI and digital subtraction angiography (DSA) were performed 3 wk following implantation. With a 2-French catheter secured in the rabbit's gastroduodenal artery, each rabbit was transferred to an adjacent 1.5T MRI scanner. DW- and TRIP-MRI were performed to determine if necrotic tumor core could be differentiated from viable tumor periphery. For each, we compared mean differences between tumor core/periphery using a 2-tailed paired t-test (alpha = 0.05). Imaging was correlated with histopathology.

RESULTS

Tumors were successfully grown in all rabbits, confirmed by necropsy. On DW-MRI, mean apparent diffusion coefficient (ADC) value was higher in necrotic tumor core (2.1 +/- 0.3 mm(2)/s) than in viable tumor periphery (1.4 +/- 0.5 mm(2)/s) (P < 0.05). On TRIP-MRI, mean perfusion values was higher in tumor periphery (110 +/- 47 relative units) than in tumor core (66 +/- 31 relative units) (P < 0.001).

CONCLUSION

Functional MRI can be used to differentiate necrotic from viable tumor cells in an animal pancreatic cancer model using ADC (DW-MRI) and perfusion (TRIP-MRI) values.

Arsenic antagonizes the Hedgehog pathway by preventing ciliary accumulation and reducing stability of the Gli2 transcriptional effector

Aberrant Hedgehog (Hh) pathway activation has been implicated in cancers of diverse tissues and organs, and the tumor growth-inhibiting effects of pathway antagonists in animal models have stimulated efforts to develop pathway antagonists for human therapeutic purposes. These efforts have focused largely on cyclopamine derivatives or other compounds that mimic cyclopamine action in binding to and antagonizing Smoothened, a membrane transductory component. We report here that arsenicals, in contrast, antagonize the Hh pathway by targeting Gli transcriptional effectors; in the short term, arsenic blocks Hh-induced ciliary accumulation of Gli2, the primary activator of Hh-dependent transcription, and with prolonged incubation arsenic reduces steady-state levels of Gli2. Arsenicals active in Hh pathway antagonism include arsenic trioxide (ATO), a curative agent in clinical use for acute promyelocytic leukemia (APL); in our studies, ATO inhibited growth of Hh pathway-driven medulloblastoma allografts derived from Ptch+/-p53-/- mice within a range of serum levels comparable to those achieved in treatment of human APL. Arsenic thus could be tested rapidly as a therapeutic agent in malignant diseases associated with Hh pathway activation and could be particularly useful in such diseases that are inherently resistant or have acquired resistance to cyclopamine mimics.

Dasatinib inhibits the development of metastases in a mouse model of pancreatic ductal adenocarcinoma

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is a highly invasive and metastatic disease for which conventional treatments are of limited efficacy. A number of agents in development are potential anti-invasive and antimetastatic agents, including the Src kinase inhibitor dasatinib. The aim of this study was to assess the importance of Src in human PDAC and to use a genetically engineered mouse model of PDAC to determine the effects of dasatinib on PDAC progression.

METHODS

Src expression and activity was measured by immunohistochemistry in 114 human PDACs. Targeting expression of Trp53(R172H) and Kras(G12D) to the mouse pancreas results in the formation of invasive and metastatic PDAC. These mice were treated with dasatinib, and disease progression monitored. Cell lines were derived from mouse PDACs, and in vitro effects of dasatinib assessed.

RESULTS

Src expression and activity were up-regulated in human PDAC and this correlated with reduced survival. Dasatinib inhibited the migration and invasion of PDAC cell lines, although no effects on proliferation were seen at concentrations that inhibited Src kinase activity. In addition, dasatinib significantly inhibited the development of metastases in Pdx1-Cre, Z/EGFP, LSL-Kras(G12D/+), LSL-Trp53(R172H/+) mice. However, there was no survival advantage in the dasatinib-treated animals owing to continued growth of the primary tumor.

CONCLUSIONS

This study confirms the importance of Src in human PDAC and shows the usefulness of a genetically engineered mouse model of PDAC for assessing the activity of potential antimetastatic agents and suggests that dasatinib should be evaluated further as monotherapy after resection of localized invasive PDAC.

Drosophila as a novel therapeutic discovery tool for thyroid cancer

BACKGROUND

Multiple endocrine neoplasia type II (MEN2) is a rare but aggressive cancer for which no effective treatment currently exists. A Drosophila model was developed to identify novel genetic modifier loci of oncogenic RET, as well as to provide a whole animal system to rapidly identify compounds that suppressed RET-dependent MEN2. ZD6474 (Vandetanib), currently in phase III trials, suppressed tumorigenesis in MEN2 model flies, demonstrating for the first time the effectiveness of a Drosophila-based whole animal model for identifying therapeutically useful compounds.

SUMMARY

Clinical data suggest that drug mono-therapy for MEN2 and other cancers typically yield only moderate benefits as patients develop drug resistance and suffer from drug-induced pathway feedback. Combinations of drugs that target different nodes of the oncogenic pathway are an effective way to prevent resistance as well as feedback. Identifying the optimal drug-dose combinations for therapy poses a significant challenge in existing mouse models. Fly models offer a means to quickly and effectively identify drug combinations that are well tolerated and potently suppress the MEN2 phenotype. This approach may also identify differences in therapeutic responses between the two subtypes of MEN2--MEN2A and MEN2B--providing additional therapeutic insights.

CONCLUSIONS

Fly models have proven useful for identifying known drugs as well as novel compounds that, as single agents or in combinations, effectively suppress the MEN2 syndrome. These findings validate the use of fly models for both drug discovery as well as identification of useful drug combinations. In the future, rapid pairing of new genomic information with increasingly complex fly models will aid us in efforts to further tailor drug treatments toward personalized medicine.

Learning from Jekyll to control Hyde: Hedgehog signaling in development and cancer

The Hedgehog (Hh) cascade controls cell proliferation, differentiation and patterning of tissues during embryogenesis but is largely suppressed in the adult. The Hh pathway can become reactivated in cancer. Here, we assimilate data from recent studies to understand how and when the Hh pathway is turned on to aid the neoplastic process. Hh signaling is now known to have a role in established tumors, enabling categorization of tumors based on the role Hh signaling plays in their growth. This categorization has relevance for prognosis and targeted therapeutics. In the first category, abnormal Hh signaling initiates the tumor. In the second category, Hh signaling helps maintain the tumor. In the third category, Hh signaling is implicated but its role is not yet defined.

Gemcitabine intercellular diffusion mediated by gap junctions: new implications for cancer therapy

Background

Solid tumors are often poorly vascularized, with cells that can be 100 μm away from blood vessels. These distant cells get less oxygen and nutrients and are exposed to lower doses of chemotherapeutic agents. As gap junctions allow the passage of small molecules between cells, we tested the possibility that the chemotherapeutic agent gemcitabine can diffuse through gap junctions in solid tumors.

Results

We first showed with a dye transfer assay that the glioblastoma and the osteosarcoma cells used in this study have functional gap junctions. These cells were genetically engineered to express the herpes simplex virus thymidine kinase (TK), and induced a "bystander effect" as demonstrated by the killing of TK-negative cells in presence of the nucleoside analogue ganciclovir (GCV). The ability of gemcitabine to induce a similar bystander effect was then tested by mixing cells treated with 3 μM gemcitabine for 24 hours with untreated cells at different ratios. In all cell lines tested, bystander cells were killed with ratios containing as low as 5% treated cells, and this toxic effect was reduced in presence of α-glycyrrhetinic acid (AGA), a specific gap junction inhibitor. We also showed that a 2- or a 24-hour gemcitabine treatment was more efficient to inhibit the growth of spheroids with functional gap junctions as compared to the same treatment made in presence of AGA. Finally, after a 24-hour gemcitabine treatment, the cell viability in spheroids was reduced by 92% as opposed to 51% in presence of AGA.

Conclusion

These results indicate that gemcitabine-mediated toxicity can diffuse through gap junctions, and they suggest that gemcitabine treatment could be more efficient for treating solid tumors that display gap junctions. The presence of these cellular channels could be used to predict the responsiveness to this nucleoside analogue therapy.

Development of an orthotopic model of invasive pancreatic cancer in an immunocompetent murine host

PURPOSE

The most common preclinical models of pancreatic adenocarcinoma utilize human cells or tissues that are xenografted into immunodeficient hosts. Several immunocompetent, genetically engineered mouse models of pancreatic cancer exist; however, tumor latency and disease progression in these models are highly variable. We sought to develop an immunocompetent, orthotopic mouse model of pancreatic cancer with rapid and predictable growth kinetics.

EXPERIMENTAL DESIGN

Cell lines with epithelial morphology were derived from liver metastases obtained from Kras(G12D/+);LSL-Trp53(R172H/+);Pdx-1-Cre mice. Tumor cells were implanted in the pancreas of immunocompetent, histocompatible B6/129 mice, and the mice were monitored for disease progression. Relevant tissues were harvested for histologic, genomic, and immunophenotypic analysis.

RESULTS

All mice developed pancreatic tumors by two weeks. Invasive disease and liver metastases were noted by six to eight weeks. Histologic examination of tumors showed cytokeratin-19-positive adenocarcinoma with regions of desmoplasia. Genomic analysis revealed broad chromosomal changes along with focal gains and losses. Pancreatic tumors were infiltrated with dendritic cells, myeloid-derived suppressor cells, macrophages, and T lymphocytes. Survival was decreased in RAG(-/-) mice, which are deficient in T cells, suggesting that an adaptive immune response alters the course of disease in wild-type mice.

CONCLUSIONS

We have developed a rapid, predictable orthotopic model of pancreatic adenocarcinoma in immunocompetent mice that mimics human pancreatic cancer with regard to genetic mutations, histologic appearance, and pattern of disease progression. This model highlights both the complexity and relevance of the immune response to invasive pancreatic cancer and may be useful for the preclinical evaluation of new therapeutic agents.

Targeting Hedgehog--a cancer stem cell pathway

The Hedgehog (Hh) pathway has been implicated in a wide variety of human tumors, and early clinical trials with pathway antagonists have validated Hh signaling as a bona fide anticancer target. Despite these encouraging results, several issues surrounding the basic biology of the Hh pathway in human cancers remain unclear. These include the influence of specific oncogenic events on Hh signal transduction, the precise mode of Hh signaling (i.e., autocrine or paracrine) that occurs within human tumors, and the best means to inhibit aberrant pathway activity in the clinical setting. The cancer stem cell (CSC) hypothesis may explain a number of clinical phenomena, such as unchecked self-renewal and the development of metastatic disease, and to some extent, the Hh signaling pathway has been implicated in all of these processes. Therefore, Hh pathway inhibitors may also represent some of the first agents to formally examine the CSC hypothesis in the clinical setting. The diverse nature of Hh signaling in human cancers suggests that disease-specific factors must be carefully considered to identify the optimal use of novel pathway inhibitors.

Serum tumor markers in pancreatic cancer-recent discoveries

The low prevalence of pancreatic cancer remains an obstacle to the development of effective screening tools in an asymptomatic population. However, development of effective serologic markers still offers the potential for improvement of diagnostic capabilities, especially for subpopulations of patients with high risk for pancreatic cancer. The accurate identification of patients with pancreatic cancer and the exclusion of disease in those with benign disorders remain important goals. While clinical experience largely dismissed many candidate markers as useful markers of pancreatic cancer, CA19-9 continues to show promise. The present review highlights the development and the properties of different tumor markers in pancreatic cancer and their impact on the diagnostic and treatment of this aggressive disease.

Hedgehog signaling controls mesenchymal growth in the developing mammalian digestive tract

Homeostasis of the vertebrate digestive tract requires interactions between an endodermal epithelium and mesenchymal cells derived from the splanchnic mesoderm. Signaling between these two tissue layers is also crucial for patterning and growth of the developing gut. From early developmental stages, sonic hedgehog (Shh) and indian hedgehog (Ihh) are secreted by the endoderm of the mammalian gut, indicative of a developmental role. Further, misregulated hedgehog (Hh) signaling is implicated in both congenital defects and cancers arising from the gastrointestinal tract. In the mouse, only limited gastrointestinal anomalies arise following removal of either Shh or Ihh. However, given the considerable overlap in their endodermal expression domains, a functional redundancy between these signals might mask a more extensive role for Hh signaling in development of the mammalian gut. To address this possibility, we adopted a conditional approach to remove both Shh and Ihh functions from early mouse gut endoderm. Analysis of compound mutants indicates that continuous Hh signaling is dispensable for regional patterning of the gut tube, but is essential for growth of the underlying mesenchyme. Additional in vitro analysis, together with genetic gain-of-function studies, further demonstrate that Hh proteins act as paracrine mitogens to promote the expansion of adjacent mesenchymal progenitors, including those of the smooth muscle compartment. Together, these studies provide new insights into tissue interactions underlying mammalian gastrointestinal organogenesis and disease.

Y-box binding protein-1 is a novel molecular target for tumor vessels

Y-box binding protein-1 (YB-1) is a member of the cold shock protein family and functions in transcription and translation. Many reports indicate that YB-1 is highly expressed in tumor cells and is a marker for tumor aggressiveness and clinical prognosis. Here, we show clear evidence that YB-1 is expressed in the angiogenic endothelial cells of various tumors, such as glioblastoma, esophageal cancer, gastric cancer, colon cancer, and lung cancer, as well as in tumor cells. YB-1 was highly expressed in glomeruloid microvascular endothelial cells of brain tumors and microvessels in the desmoplastic region around multiple solid tumors. On the other hand, no or low YB-1 expression was observed in normal angiogenic endothelial cells from fetal kidney, newborn lung, and placenta. The endothelial cells in inflammatory regions of granulomas were also weakly labeled. Knockdown of YB-1 expression by small-interfering RNA induced G1 cell cycle arrest and inhibited the growth of human umbilical vein endothelial cells stimulated by growth factors. Taken together, YB-1 plays an important role in the growth of not only tumor cells but also tumor-associated endothelial cells, suggesting that YB-1 is a promising target for cancer therapy.

New frontiers in pancreatic cancer research

Pancreatic adenocarcinoma (PDA) is a highly lethal and aggressive malignancy with high mortality rates. It is critical to evaluate novel therapeutic strategies and targets for the treatment of this disease. In this article, the authors describe the important areas of focus in pancreatic cancer research, recent advances in these areas, and novel approaches that have the potential to bring about positive patient outcomes in this lethal disease. This article also focuses on recent developments in identifying new, more sensitive, and more specific blood biomarkers with potential use in the early detection of PDA.

Hedgehog signaling is critical for normal liver regeneration after partial hepatectomy in mice

Distinct mechanisms are believed to regulate growth of the liver during fetal development and after injury in adults, because the former relies on progenitors and the latter generally involves replication of mature hepatocytes. However, chronic liver injury in adults increases production of Hedgehog (Hh) ligands, developmental morphogens that control progenitor cell fate and orchestrate various aspects of tissue construction during embryogenesis. This raises the possibility that similar Hh-dependent mechanisms also might regulate adult liver regeneration. The current analysis of murine liver regeneration after 70% partial hepatectomy (PH), an established model of adult liver regeneration, demonstrated that PH induced production of Hh ligands and activated Hh signaling in liver cells. Treatment with a specific Hh signaling inhibitor interfered with several key components of normal liver regeneration, significantly inhibiting progenitor responses, matrix remodeling, proliferation of hepatocytes and ductular cells, and restoration of liver mass. These global inhibitory effects on liver regeneration dramatically reduced survival after PH.

CONCLUSION

Mechanisms that mediate liver organogenesis, such as Hh pathway activation, are retained and promote reconstruction of adult livers after injury.

Organ-, inflammation- and cancer specific transcriptional fingerprints of pancreatic and hepatic stellate cells

Background

Tissue fibrosis is an integral component of chronic inflammatory (liver and pancreas) diseases and pancreatic cancer. Activated pancreatic- (PSC) and hepatic- (HSC) stellate cells play a key role in fibrogenesis. To identify organ- and disease-specific stellate cell transcriptional fingerprints, we employed genome-wide transcriptional analysis of primary human PSC and HSC isolated from patients with chronic inflammation or cancer.

Methods

Stellate cells were isolated from patients with pancreatic ductal adenocarcinoma (n = 5), chronic pancreatitis (n = 6), liver cirrhosis (n = 5) and liver metastasis of pancreatic ductal adenocarcinoma (n = 6). Genome-wide transcriptional profiles of stellate cells were generated using our 51K human cDNA microarray platform. The identified organ- and disease specific genes were validated by quantitative RT-PCR, immunoblot, ELISA, immunocytochemistry and immunohistochemistry.

Results

Expression profiling identified 160 organ- and 89 disease- specific stellate cell transcripts. Collagen type 11a1 (COL11A1) was discovered as a novel PSC specific marker with up to 65-fold higher expression levels in PSC compared to HSC (p < 0.0001). Likewise, the expression of the cytokine CCL2 and the cell adhesion molecule VCAM1 were confined to HSC. PBX1 expression levels tend to be increased in inflammatory- vs. tumor- stellate cells. Intriguingly, tyrosine kinase JAK2 and a member of cell contact-mediated communication CELSR3 were found to be selectively up-regulated in tumor stellate cells.

Conclusions

We identified and validated HSC and PSC specific markers. Moreover, novel target genes of tumor- and inflammation associated stellate cells were discovered. Our data may be instrumental in developing new tailored organ- or disease-specific targeted therapies and stellate cell biomarkers.

The benefits and challenges associated with the use of drug delivery systems in cancer therapy

The use of drug delivery systems as nanocarriers for chemotherapeutic agents can improve the pharmacological properties of drugs by altering drug pharmacokinetics and biodistribution. Among the many drug delivery systems available, both micelles and liposomes have gained the most attention in recent years due to their clinical success. There are several formulations of these nanocarrier systems in various stages of clinical trials, as well as currently clinically approved liposomal-based drugs. In this review, we discuss these drug carrier systems, as well as current efforts that are being made in order to further improve their delivery efficacy through the incorporation of targeting ligands. In addition, this review discusses aspects of drug resistance attributed to the remodeling of the extracellular matrix that occurs during tumor development and progression, as well as to the acidic, hypoxic, and glucose-deprived tumor microenvironment. Finally, we address future prospective approaches to overcoming drug resistance by further modifications made to these drug delivery systems, as well as the possibility of coencapsulation/coadministration of various drugs aimed to surmount some of these microenvironmental-influenced obstacles for efficacious drug delivery in chemotherapy.

Small molecule modulation of HH-GLI signaling: current leads, trials and tribulations

Many human sporadic cancers have been recently shown to require the activity of the Hedgehog-GLI pathway for sustained growth. The survival and expansion of cancer stem cells is also HH-GLI dependent. Here we review the advances on the modulation of HH-GLI signaling by small molecules. We focus on both natural compounds and synthetic molecules that target upstream pathway components, mostly SMOOTHENED, and those that target the last steps of the pathway, the GLI transcription factors. In this review we have sought to provide some bases for useful comparisons, listing original assays used and sources to facilitate comparisons of IC50 values. This area is a rapidly expanding field where biology, medicine and chemistry intersect, both in academia and industry. We also highlight current clinical trials, with positive results in early stages. While we have tried to be exhaustive regarding the molecules, not all data is in the public domain yet. Indeed, we have opted to avoid listing chemical structures but these can be easily found in the references given. Finally, we are hopeful that the best molecules will soon reach the patients but caution about the lack of investment on compounds that lack tight IP positions. While the market in developed nations is expected to compensate the investment and risk of making HH-GLI modulators, other sources or plans must be available for developing nations and poor patient populations. The promise of curing cancer recalls the once revered dream of El Dorado, which taught us that not everything that GLI-tters is gold.

Tumor-initiated inflammation overrides protective adaptive immunity in an induced melanoma model in mice

We studied the effect of the immune system on two differentially aggressive melanomas developing in mice on conditional deletion of the INK4A/ARF tumor suppressor gene, with concomitant expression of oncogene H-Ras(G12V) and a natural cancer-germline tumor antigen (TA). "Slow progressor" melanomas contained no activated T lymphocytes (TL). In contrast, "aggressive" melanomas were infiltrated by activated TLs lacking effector molecules and expressing high levels of PD-1, indicating an exhausted phenotype. Aggressive melanomas were also infiltrated by immature myeloid cells (IMC). Infiltration was associated with local inflammation and systemic Th2/Th17-oriented chronic inflammation that seemed to impair further activation of TLs, as tumor-specific T cells adoptively transferred into mice bearing aggressive melanomas were poorly activated and failed to infiltrate the melanoma. This immunosuppression also led to the incapacity of these mice to reject inoculated TA-positive tumors, in contrast to slow-progressing melanoma-bearing mice, which were responsive. To test the role of adaptive immunity in tumor progression, we induced melanomas in immunodeficient RagKO compound mice. These mice developed aggressive but not slow-progressing melanomas at a higher frequency and with a shorter latency than immunocompetent mice. Immunodeficient mice also developed abnormal inflammation and infiltration of IMCs in a manner similar to immunocompetent mice, indicating that this phenotype was not dependent on adaptive immunity. Therefore, tumor-intrinsic factors distinguishing the two melanoma types control the initiation of inflammation, which was independent of adaptive immunity. The latter delayed development of aggressive melanomas but was overridden by inflammation.

Chronic cisplatin treatment promotes enhanced damage repair and tumor progression in a mouse model of lung cancer

Chemotherapy resistance is a major obstacle in cancer treatment, yet the mechanisms of response to specific therapies have been largely unexplored in vivo. Employing genetic, genomic, and imaging approaches, we examined the dynamics of response to a mainstay chemotherapeutic, cisplatin, in multiple mouse models of human non-small-cell lung cancer (NSCLC). We show that lung tumors initially respond to cisplatin by sensing DNA damage, undergoing cell cycle arrest, and inducing apoptosis-leading to a significant reduction in tumor burden. Importantly, we demonstrate that this response does not depend on the tumor suppressor p53 or its transcriptional target, p21. Prolonged cisplatin treatment promotes the emergence of resistant tumors with enhanced repair capacity that are cross-resistant to platinum analogs, exhibit advanced histopathology, and possess an increased frequency of genomic alterations. Cisplatin-resistant tumors express elevated levels of multiple DNA damage repair and cell cycle arrest-related genes, including p53-inducible protein with a death domain (Pidd). We demonstrate a novel role for PIDD as a regulator of chemotherapy response in human lung tumor cells.

Establishment of six new human biliary tract carcinoma cell lines and identification of MAGEH1 as a candidate biomarker for predicting the efficacy of gemcitabine treatment

The aim of this study was to establish new biliary tract carcinoma (BTC) cell lines and identify predictive biomarkers for the potential effectiveness of gemcitabine therapy. Surgical specimens of BTC were transplanted directly into immunodeficient mice to establish xenografts, then subjected to in vitro cell culture. The gemcitabine sensitivity of each cell line was determined and compared with the genome-wide gene expression profile. A new predictive biomarker candidate was validated using an additional cohort of gemcitabine-treated BTC cases. From 55 BTC cases, we established 19 xenografts and six new cell lines. Based on their gemcitabine sensitivity, 10 BTC cell lines (including six new and four publicly available ones) were clearly categorized into two groups, and MAGEH1 mRNA expression in the tumor cells showed a significant negative correlation with their sensitivity to gemcitabine. Immunohistochemically, MAGEH1 protein was detected in three (50%) out of six sensitive cell lines, and four (100%) out of four resistant cell lines. In the validation cohort of gemcitabine-treated recurrence cases, patients were categorized into "effective" and "non-effective" groups according to the RECIST guidelines for assessment of chemotherapeutic effects. MAGEH1 protein expression was detected in two (40%) out of five "effective" cases and all four (100%) "non-effective" cases. We have established a new BTC bioresource that covers a wide range of biological features, including drug sensitivity, and is linked with clinical information. Negative expression of MAGEH1 protein serves as a potential predictive marker for the effectiveness of gemcitabine therapy in BTC.

Molecular mechanism of pancreatic cancer--understanding proliferation, invasion, and metastasis

INTRODUCTION

The purpose of this review is to highlight the molecular mechanisms leading to the development and progression of pancreatic ductal adenocarcinoma (PDAC) with particular emphasis on tumor cell proliferation, local invasion, and metastasis. Recent advances in the field of PDAC biology have shed light on the molecular events that trigger PDAC initiation and maintenance.

RESULTS

It is now clear that apart from the genetic alterations within the tumor cells, interactions of the tumor with its environment are necessary for proliferation and invasion. Interestingly, a number of developmental signaling pathways are reactivated in PDAC. Progress has also been made in the understanding of the molecular events that govern the process of metastasis.

CONCLUSION

Although our understanding of the mechanisms underlying PDAC pathobiology are more advanced than ever, little progress has been made in the clinical treatment of PDAC, and successful bench-to-bedside transfer of knowledge to boost new treatment options is still unsatisfying.

Cell line-based platforms to evaluate the therapeutic efficacy of candidate anticancer agents

Efforts to discover new cancer drugs and predict their clinical activity are limited by the fact that laboratory models to test drug efficacy do not faithfully recapitulate this complex disease. One important model system for evaluating candidate anticancer agents is human tumour-derived cell lines. Although cultured cancer cells can exhibit distinct properties compared with their naturally growing counterparts, recent technologies that facilitate the parallel analysis of large panels of such lines, together with genomic technologies that define their genetic constitution, have revitalized efforts to use cancer cell lines to assess the clinical utility of new investigational cancer drugs and to discover predictive biomarkers.

Smac mimetic increases chemotherapy response and improves survival in mice with pancreatic cancer

Failure of chemotherapy in the treatment of pancreatic cancer is often due to resistance to therapy-induced apoptosis. A major mechanism for such resistance is the expression and activity of inhibitors of apoptosis proteins (IAP). Smac (second mitochondria-derived activator of caspase) is a mitochondrial protein that inhibits IAPs. We show that JP1201, a Smac mimetic, is a potent enhancer of chemotherapy in robust mouse models of pancreatic cancer. Combination of JP1201 with gemcitabine reduced primary and metastatic tumor burden in orthotopic xenograft and syngenic tumor models, induced regression of established tumors, and prolonged survival in xenograft and transgenic models of pancreatic cancer. The effect of JP1201 was phenocopied by XIAP small interfering RNA in vitro and correlated with elevated levels of tumor necrosis factor alpha protein in vivo. The continued development of JP1201 and other strategies designed to enhance therapy-induced apoptosis in pancreatic cancer is warranted.

New promising drug targets in cancer- and metastasis-initiating cells

The unique properties of cancer- and metastasis-initiating cells endowed with a high self-renewal and aberrant differentiation potential (including their elevated expression levels of anti-apoptotic factors, multidrug transporters, and DNA repair and detoxifying enzymes) might be associated with their resistance to current clinical cancer therapies and disease recurrence. The eradication of cancer- and metastasis-initiating cells by molecular targeting of distinct deregulated signaling elements that might contribute to their sustained growth, survival, and treatment resistance, therefore, is of immense therapeutic interest. These novel targeted approaches should improve the efficacy of current therapeutic treatments against highly aggressive, metastatic, recurrent, and lethal cancers.