Cooperativity of Oncogenic K-Ras and Downregulated p16/INK4A in Human Pancreatic Tumorigenesis

Activation of K-ras and inactivation of p16 are the most frequently identified genetic alterations in human pancreatic epithelial adenocarcinoma (PDAC). Mouse models engineered with mutant K-ras and deleted p16 recapitulate key pathological features of PDAC. However, a human cell culture transformation model that recapitulates the human pancreatic molecular carcinogenesis is lacking. In this study, we investigated the role of p16 in hTERT-immortalized human pancreatic epithelial nestin-expressing (HPNE) cells expressing mutant K-ras (K-ras^G12V). We found that expression of p16 was induced by oncogenic K-ras in these HPNE cells and that silencing of this induced p16 expression resulted in tumorigenic transformation and development of metastatic PDAC in an orthotopic xenograft mouse model. Our results revealed that PI3K/Akt, ERK1/2 pathways and TGFα signaling were activated by K-ras and involved in the malignant transformation of human pancreatic cells. Also, p38/MAPK pathway was involved in p16 up-regulation. Thus, our findings establish an experimental cell-based model for dissecting signaling pathways in the development of human PDAC. This model provides an important tool for studying the molecular basis of PDAC development and gaining insight into signaling mechanisms and potential new therapeutic targets for altered oncogenic signaling pathways in PDAC.     

Activated K-ras and INK4a/Arf deficiency cooperate during the development of pancreatic cancer by activation of Notch and NF-κB signaling pathways

Background

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related death in the United States, suggesting that novel strategies for the prevention and treatment of PDAC are urgently needed. K-ras mutations are observed in >90% of pancreatic cancer, suggesting its role in the initiation and early developmental stages of PDAC. In order to gain mechanistic insight as to the role of mutated K-ras, several mouse models have been developed by targeting a conditionally mutated K-ras^G12D for recapitulating PDAC. A significant co-operativity has been shown in tumor development and metastasis in a compound mouse model with activated K-ras and Ink4a/Arf deficiency. However, the molecular mechanism(s) by which K-ras and Ink4a/Arf deficiency contribute to PDAC has not been fully elucidated.

Methodology/Principal Findings

To assess the molecular mechanism(s) that are involved in the development of PDAC in the compound transgenic mice with activated K-ras and Ink4a/Arf deficiency, we used multiple methods, such as Real-time RT-PCR, western blotting assay, immunohistochemistry, MTT assay, invasion, EMSA and ELISA. We found that the deletion of Ink4a/Arf in K-ras^G12D expressing mice leads to PDAC, which is in part mediated through the activation of Notch and NF-κB signaling pathways. Moreover, we found down-regulation of miR-200 family, which could also play important roles in tumor development and progression of PDAC in the compound transgenic mice.

Conclusions/Significance

Our results suggest that the activation of Notch and NF-κB together with the loss of miR-200 family is mechanistically linked with the development and progression of PDAC in the compound K-ras^G12D and Ink4a/Arf deficient transgenic mice.     

RAD001 targeted HUVECs reverses 12-lipoxygenase-induced angiogenesis in oesophageal squamous cell carcinoma

12-LOX plays an important role in the progression of various malignancies. However, the underlying mechanisms of the action of 12-LOX and tumour treatment strategies remain not fully defined. In this study, we investigated the possible roles of 12-LOX in ESCC and explored the new therapeutic target. Approximately 73% of ESCC tissues showed marked up-regulation of 12-LOX, which was associated with poor prognosis. 12-LOX overexpression was positively correlated with the malignant progression of ESCC as demonstrated both in vitro and in vivo. Up-regulation of 12-LOX significantly increased the proliferation of ESCC cells and the xenograft volume. Moreover, 12-LOX up-regulation promoted tube formation of HUVECs and tumour angiogenesis in xenografts. Mechanism investigation indicated that 12-LOX overexpression led to activation of the PI3K/AKT/mTOR pathway and the up-regulation of VEGF in ESCC cells. Subsequent analysis indicated that the RAD001 could reverse the 12-LOX-induced promoting effect on ESCC. Specifically, the application of RAD001 inhibited the proliferation of ESCC cells and the tube-forming ability of HUVECs. In the drug group, the xenografts exhibited significant volume reduction and angiogenesis inhibition. We demonstrated that RAD001 could inhibit HUVEC migration. These findings presented the evidence that RAD001 had distinct roles on HUVECs and could exert anti-tumour effects by targeting not only the PI3K/AKT/mTOR pathway but the angiogenesis in ESCC.     

Trefoil factor 3 promotes pancreatic carcinoma progression via WNT pathway activation mediated by enhanced WNT ligand expression

Pancreatic ductal adenocarcinoma (PDAC) is a major cause of cancer-related mortality with a dismal prognosis that has changed little over the past few decades. Further understanding of the molecular pathology of PDAC progression is urgently required in order to improve the prognosis of patients with PDAC. Herein, it was observed that trefoil factor 3 (TFF3) expression was elevated in PDAC, and was positively correlated with a worse overall patient survival outcome. Forced expression of TFF3 promoted oncogenic functions of PDAC cells in vitro including cell proliferation, survival, foci formation, cancer stem cell-like behavior and invasion, ex vivo colony growth in 3D-Matrigel, and xenograft growth in vivo. Depletion or pharmacological inhibition of TFF3 inhibited these same processes. RNA-Seq analysis and subsequent mechanistic analyses demonstrated that TFF3 increased the expression of various WNT ligands to mediate WNT pathway activation required for TFF3-stimulated PDAC progression. Combined pharmacological inhibition of TFF3 and WNT signaling significantly attenuated PDAC xenograft growth and potentiated the therapeutic efficacy of gemcitabine in both ex vivo and in vivo models. Hence, a mechanistic basis for combined inhibition of pathways enhancing PDAC progression is provided and suggests that inhibition of TFF3 may assist to ameliorate outcomes in PDAC.Subject terms: Oncogenesis, Pancreatic cancer     

Celecoxib and acetylbritannilactone interact synergistically to suppress breast cancer cell growth via COX-2-dependent and -independent mechanisms

The use of celecoxib is associated with a significant decrease in breast cancer risk. However, the long-term use of high-dose celecoxib might be limited owing to cardiovascular side effects. In this study, we found that acetylbritannilactone (ABL), extract from a Chinese medicinal herb, could reduce celecoxib dose and potentiate the growth-inhibitory effect in breast cancer cells. ABL enhanced the apoptotic effect of celecoxib in COX-2-expressing cells, but had little effect in COX-2-negative cells. The apoptosis induced by the combination treatment disappeared when COX-2 was knocked down, whereas the lack of apoptotic effects in COX-2-negative cells was reversed after COX-2 transfection. However, the combination treatment induced a G₀/G₁ phase arrest independent of whether or not the cells expressed COX-2. The G₀/G₁ arrest was attributed to a decreased expression of cyclinD1, cyclinE, CDK2 and CDK6, especially the upregulation of p21. In addition, inhibition of Akt and p38 signaling pathways was required by the synergism, as the constitutively active Akt and p38 protected cells against apoptosis and cell cycle arrest induced by the combination treatment. In vivo, administration of celecoxib and ABL were more effective than the individual agents against xenograft tumor growth. Thus, our data suggested that the combinatorial approach of celecoxib and ABL might be helpful for breast cancer treatment.     

High expression of diffuse panbronchiolitis critical region 1 gene promotes cell proliferation,migration and invasion in pancreatic ductal adenocarcinoma

Diffuse panbronchiolitis critical region 1 (DPCR1) is located in the major histocompatibility complex (MHC) class I. It was reported to be downregulated in invasive pituitary adenoma compared with that in non-invasive tumors, but upregulated in the precursor of gastric carcinogenesis. However, the direct effect of DPCR1 on cancer cells has rarely been reported, and the role DPCR1 in pancreatic ductal adenocarcinoma (PDAC) remains unclear. The clinical sample validation and public data analysis of the present study demonstrated that DPCR1 was upregulated markedly in PDAC and this high expression was negatively correlated with the patient prognosis. Functionally, knocking down DPCR1 in PDAC cell lines inhibited cell proliferation, migration and invasion in vitro. Tumor xenograft experiments further showed that suppression of DPCR1 inhibited tumor growth in vivo. In addition, the results of RNA deep sequencing and qRT-PCR assay showed that DPCR1 participated in PADC progression by regulating nuclear factor-kappa B signaling pathway, suggesting that it might be a novel oncogene in tumor progression and a potential therapeutic target in PDAC as well.     

Synthesis,biological evaluation and docking study of 1,3,4-thiadiazole-thiazolidinone hybrids as anti-inflammatory agents with dual inhibition of COX-2 and 15-LOX

Selective inhibition of both cyclooxygenase-2 (COX-2) and 15-lipooxygenase (15-LOX) may provide good strategy for alleviation of inflammatory disorders while minimizing side effects associated with current anti-inflammatory drugs. The present study describes the synthesis, full characterization and biological evaluation of a series of thiadiazole-thiazolidinone hybrids bearing 5-alk/arylidene as dual inhibitors of these enzymes. Our design was based on merging pharmacophores that exhibit portent anti-inflammatory activities in one molecular frame. 5-(4-hydroxyphenyl)-1,3,4-thiadiazol-2-amine (3) was efficiently synthesized, chloroacetylated and cyclized to give the key 4-thiazolidinone (5). Knovenagel condensation of 5 with different aldehydes afforded the final compounds 6a-m, 7, 8 and 9. These compounds were subjected to in vitro COX-1/COX-2, 15-LOX inhibition assays. Compounds (6a, 6f, 6i, 6l, 6m and 9) with promising potency (IC₅₀ = 70–100 nM) and selectivity index (SI = 220-55) were further tested for in vivo anti-inflammatory activity and effect on gastric mucosa. The most promising compound (6l) inhibits COX-2 enzyme at a nanomolar concentration (IC₅₀ = 70 nM, SI = 220) with simultaneous inhibition of 15-LOX (IC₅₀ = 11 µM). These results are comparable to the potency and selectivity of the standard drugs of both enzymes; celecoxib (COX-2 IC₅₀ = 49 nM, SI = 308) and zileuton (15-LOX IC₅₀ = 15 µM) in one construct. Interestingly three compounds (6a, 6l and 9) exhibited equivalent to or even higher than that of celecoxib in vivo anti-inflammatory activity at 3 h interval with good GIT safety profile. Molecular docking study conferred binding sites of these compounds on COX-2 and 15-LOX. Such type of compounds would represent valuable leads for further investigation and derivatization.     

Feed forward cycle of hypotonic stress-induced ATP release, purinergic receptor activation, and growth stimulation of prostate cancer cells

ATP is released in many cell types upon mechanical strain, the physiological function of extracellular ATP is largely unknown, however. Here we report that ATP released upon hypotonic stress stimulated prostate cancer cell proliferation, activated purinergic receptors, increased intracellular [Ca(2+)](i), and initiated downstream signaling cascades that involved MAPKs ERK1/2 and p38 as well as phosphatidylinositol 3-kinase (PI3K). MAPK activation, the calcium response as well as induction of cell proliferation upon hypotonic stress were inhibited by preincubation with the ATP scavenger apyrase, indicating that hypotonic stress-induced signaling pathways are elicited by released ATP. Hypotonic stress increased prostaglandin E(2) (PGE(2)) synthesis. Consequently, ATP release was inhibited by antagonists of PI3K (LY294002 and wortmannin), phospholipase A(2) (methyl arachidonyl fluorophosphonate (MAFP)), cyclooxygenase-2 (COX-2) (indomethacin, etodolac, NS398) and 5,8,11,14-eicosatetraynoic acid (ETYA), which are involved in arachidonic acid metabolism. Furthermore, ATP release was abolished in the presence of the adenylate cyclase (AC) inhibitor MDL-12,330A, indicating regulation of ATP-release by cAMP. The hypotonic stress-induced ATP release was significantly blunted when the ATP-mediated signal transduction cascade was inhibited on different levels, i.e. purinergic receptors were blocked by suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), the Ca(2+) response was inhibited upon chelation of intracellular Ca(2+) by 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), and ERK1,2 as well as p38 were inhibited by UO126 and SB203580, respectively. In summary our data demonstrate that hypotonic stress initiates a feed forward cycle of ATP release and purinergic receptor signaling resulting in proliferation of prostate cancer cells.     

Hedgehog Promotes Neovascularization in Pancreatic Cancers by Regulating Ang-1 and IGF-1 Expression in Bone-Marrow Derived Pro-Angiogenic Cells

Background

The hedgehog (Hh) pathway has been implicated in the pathogenesis of cancer including pancreatic ductal adenocarcinoma (PDAC). Recent studies have suggested that the oncogenic function of Hh in PDAC involves signaling in the stromal cells rather than cell autonomous effects on the tumor cells. However, the origin and nature of the stromal cell type(s) that are responsive to Hh signaling remained unknown. Since Hh signaling plays a crucial role during embryonic and postnatal vasculogenesis, we speculated that Hh ligand may act on tumor vasculature specifically focusing on bone marrow (BM)-derived cells.

Methodology/Principal Findings

Cyclopamine was utilized to inhibit the Hh pathway in human PDAC cell lines and their xenografts. BM transplants, co-culture systems of tumor cells and BM-derived pro-angiogenic cells (BMPCs) were employed to assess the role of tumor-derived Hh in regulating the BM compartment and the contribution of BM-derived cells to angiogenesis in PDAC. Cyclopamine administration attenuated Hh signaling in the stroma rather than in the cancer cells as reflected by decreased expression of full length Gli2 protein and Gli1 mRNA specifically in the compartment. Cyclopamine inhibited the growth of PDAC xenografts in association with regression of the tumor vasculature and reduced homing of BM-derived cells to the tumor. Host-derived Ang-1 and IGF-1 mRNA levels were downregulated by cyclopamine in the tumor xenografts. In vitro co-culture and matrigel plug assays demonstrated that PDAC cell-derived Shh induced Ang-1 and IGF-1 production in BMPCs, resulting in their enhanced migration and capillary morphogenesis activity.

Conclusions/Significance

We identified the BMPCs as alternative stromal targets of Hh-ligand in PDAC suggesting that the tumor vasculature is an attractive therapeutic target of Hh blockade. Our data is consistent with the emerging concept that BM-derived cells make important contributions to epithelial tumorigenesis.     

An exploratory trial of cyclooxygenase type 2 inhibitor in HIV-1 infection: downregulated immune activation and improved T cell-dependent vaccine responses

Chronic HIV infection is characterized by chronic immune activation and dysfunctional T cells with elevated intracellular cyclic AMP (cAMP), which inhibits the T cell activation capability. cAMP may be induced by prostaglandin E(2) following lipopolysaccharide (LPS)-induced upregulation of cyclooxygenase type 2 (COX-2) in monocytes due to the elevated LPS levels in patients with chronic HIV infection. This hypothesis was tested using celecoxib, a COX-2 inhibitor, for 12 weeks in HIV-infected patients without antiretroviral treatment in a prospective, open, randomized exploratory trial. Thirty-one patients were randomized in the trial; 27 completed the study, including 13 patients on celecoxib. Celecoxib reduced chronic immune activation in terms of CD38 density on CD8(+) T cells (-24%; P = 0.04), IgA levels (P = 0.04), and a combined score for inflammatory markers (P < 0.05). Celecoxib further reduced the inhibitory surface receptor programmed death 1 (PD-1) on CD8(+) T cells (P = 0.01), including PD-1 on the HIV Gag-specific subset (P = 0.02), enhanced the number of CD3(+) CD4(+) CD25(+) CD127(lo/-) Treg or activated cells (P = 0.02), and improved humoral memory recall responses to a T cell-dependent vaccine (P = 0.04). HIV RNA (P = 0.06) and D dimers (P = 0.07) tended to increase in the controls, whereas interleukin-6 (IL-6) possibly decreased in the treatment arm (P = 0.10). In conclusion, celecoxib downmodulated the immune activation related to clinical progression of chronic HIV infection and improved T cell-dependent functions in vivo.     

Clinical,Molecular and Genetic Validation of a Murine Orthotopic Xenograft Model of Pancreatic Adenocarcinoma Using Fresh Human Specimens

Background

Relevant preclinical models that recapitulate the key features of human pancreatic ductal adenocarcinoma (PDAC) are needed in order to provide biologically tractable models to probe disease progression and therapeutic responses and ultimately improve patient outcomes for this disease. Here, we describe the establishment and clinical, pathological, molecular and genetic validation of a murine, orthotopic xenograft model of PDAC.

Methods

Human PDACs were resected and orthotopically implanted and propagated in immunocompromised mice. Patient survival was correlated with xenograft growth and metastatic rate in mice. Human and mouse tumor pathology were compared. Tumors were analyzed for genetic mutations, gene expression, receptor tyrosine kinase activation, and cytokine expression.

Results

Fifteen human PDACs were propagated orthotopically in mice. Xenograft-bearing mice developed peritoneal and liver metastases. Time to tumor growth and metastatic efficiency in mice each correlated with patient survival. Tumor architecture, nuclear grade and stromal content were similar in patient and xenografted tumors. Propagated tumors closely exhibited the genetic and molecular features known to characterize pancreatic cancer (e.g. high rate of KRAS, P53, SMAD4 mutation and EGFR activation). The correlation coefficient of gene expression between patient tumors and xenografts propagated through multiple generations was 93 to 99%. Analysis of gene expression demonstrated distinct differences between xenografts from fresh patient tumors versus commercially available PDAC cell lines.

Conclusions

The orthotopic xenograft model derived from fresh human PDACs closely recapitulates the clinical, pathologic, genetic and molecular aspects of human disease. This model has resulted in the identification of rational therapeutic strategies to be tested in clinical trials and will permit additional therapeutic approaches and identification of biomarkers of response to therapy.     

Novel aryl carboximidamide and 3-aryl-1,2,4-oxadiazole analogues of naproxen as dual selective COX-2/15-LOX inhibitors: Design,synthesis and docking studies

A series of novel naproxen analogues containing 3-aryl-1,2,4-oxadiazoles moiety (4b-g) and their reaction intermediates aryl carboximidamides moiety (3b-g) was synthesized and evaluated in vitro as dual COXs/15-LOX inhibitors. Compounds 3b-g exhibited superior inhibitory activity than celecoxib as COX-2 inhibitors. Compounds 3b-d and 3g were the most potent COX-2 inhibitors with IC₅₀ range of 6.4 – 8.13 nM and higher selectivity indexes (3b, SI = 26.19; 3c, SI = 13.73; 3d, SI = 29.27; 3g, SI = 18.00) comparing to celecoxib (IC₅₀ = 42.60 nM, SI = 8.05). Regarding 15-LOX inhibitory activity, compounds belonging to aryl carboximidamide backbone 3b-e and 3g were the most potent with IC₅₀ range of 1.77–4.91 nM comparing to meclofenamate sodium (IC₅₀ = 5.64 µM). Data revealed that The levels of NO released by aryl carboximidamides 3b-g were more higher than 3-aryl-1,2,4-oxadiazole derivatives 4b-g, which correlated well with their COX-2 inhibitory activities.     

Characterization of spirostanol glycosides and furostanol glycosides from anemarrhenae rhizoma as dual targeted inhibitors of 5-lipoxygenase and Cyclooxygenase-2 by employing a combination of affinity ultrafiltration and HPLC/MS

Background : Modulation of the arachidonic acid (AA) cascade via 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2) represent the two major pathways for treatments of inflammation and pain. The design and development of inhibitors targeting both 5-LOX and COX-2 has gained increasing popularity. As evidenced, 5-LOX and COX-2 dual targeted inhibitors have recently emerged as the front runners of anti-inflammatory drugs with improved efficacy and reduced side effects. Natural products represent a rich resource for the discovery of dual targeted 5-LOX and COX-2 inhibitors. By combining affinity ultrafiltration and high-performance liquid chromatography-mass spectrometry (AUF-LC-MS), an efficient method was developed to identify spirostanol glycosides and furostanol glycosides as the 5-LOX/COX-2 dual inhibitors from saponins extract of Anemarrhenae Rhizoma (SEAR).Methods: A highly efficient method by combining affinity ultrafiltration and high-performance liquid chromatography-mass spectrometry (AUF-LC-MS) was first developed to screen and characterize the 5-LOX/COX-2 dual targeted inhibitors from SEAR. The structures of compounds in the ultrafiltrate were characterized by high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). In addition, in vitro 5-LOX/COX-2 inhibition assays and their dual expression in vivo were performed to confirm the inhibitory activities of the compounds screened by AUF-LC-MS. Molecular docking studies with the corresponding binding energy were obtained which fit nicely to both 5-LOX and COX-2 protein cavities and in agreement with our affinity studies.Results: A total of 5 compounds, timosaponin A-II, timosaponin A-III, timosaponin B-II, timosaponin B-III and anemarrhenasaponin I, were identified as potential 5-LOX/COX-2 dual targeted inhibitors with specific binding values > 1.5 and IC₅₀ ≤ 6.07 μM.Conclusion: The present work demonstrated that spirostanol glycoside and furostanol glycoside were identified as two novel classes of dual inhibitors of 5-LOX/COX-2 enzymes by employing a highly efficient screening method of AUF-LC-MS. These natural products represent a novel class of anti-inflammatory agents with the potential of improved efficacy and reduced side effects.     

A PAUF-neutralizing antibody targets both carcinoma and endothelial cells to impede pancreatic tumor progression and metastasis

Pancreatic adenocarcinoma up-regulated factor (PAUF) is expressed in pancreatic ductal adenocarcinoma (PDAC) and plays an important role in tumor progression and metastasis. Here we evaluate the anti-tumor efficacy of a human monoclonal antibody against PAUF, PMAb83, to provide a therapeutic intervention to treat the disease. PMAb83 reduced tumor growth and distant metastasis in orthotopically xenografted mice of human PDAC cells. PMAb83 treatment retarded proliferation along with weakened aggressiveness traits of the carcinoma cells. AKT/β-catenin signaling played a role in the carcinoma cell proliferation and the treated xenograft tumors exhibited reduced levels of β-catenin and cyclin D1. Moreover PMAb83 abrogated the PAUF-induced angiogenic responses of endothelial cells, reducing the density of CD31⁺ vessels in the treated tumors. In combination with gemcitabine, PMAb83 conferred enhanced survival of xenografted mice by about twofold compared to gemcitabine alone. Taken together, our findings show that PMAb83 treatment decreases the aggressiveness of carcinoma cells and suppresses tumor vascularization, which culminates in mitigated tumor growth and metastasis with improved survival in PDAC mouse models.     

Therapeutically leveraging GABAA receptors in cancer

γ-aminobutyric acid or GABA is an amino acid that functionally acts as a neurotransmitter and is critical to neurotransmission. GABA is also a metabolite in the Krebs cycle. It is therefore unsurprising that GABA and its receptors are also present outside of the central nervous system, including in immune cells. This observation suggests that GABAergic signaling impacts events beyond brain function and possibly human health beyond neurological disorders. Indeed, GABA receptor subunits are expressed in pathological disease states, including in disparate cancers. The role that GABA and its receptors may play in cancer development and progression remains unclear. If, however, those cancers have functional GABA receptors that participate in GABAergic signaling, it raises an important question whether these signaling pathways might be targetable for therapeutic benefit. Herein we summarize the effects of modulating Type-A GABA receptor signaling in various cancers and highlight how Type-A GABA receptors could emerge as a novel therapeutic target in cancer.     

Exploration of Shh and BMP paracrine signaling in a prostate cancer xenograft

Stromal–epithelial signaling is a critical regulator of normal prostate development and has been speculated to play an equally important role in the development and progression of prostate cancer. Sonic hedgehog (Shh) and bone morphogenetic proteins (BMP-4, BMP-7), expressed by the urogenital sinus epithelium and mesenchyme, exert reciprocal and coordinate effects on outgrowth of nascent prostate ducts. Over-expression of Shh in the LNCaP xenograft was shown previously to accelerate tumor growth by a paracrine mechanism. A survey of BMP regulators expressed in the developing prostate revealed increased Noggin and BMP-7 mRNA in the stromal component of Shh over-expressing xenografts. In vitro studies demonstrated that treatment of LNCaP cells with BMP-4 and BMP-s7 induced Id-1 expression and inhibited tumor cell proliferation. The activity of BMP-4 was abrogated by co-addition of Noggin; the activity of BMP-7 was not. Quantitative analysis of BMP signaling revealed ambivalent results: decreased tumor cell expression of the BMP response gene Id-1 but increased staining for phospho-SMAD 1,5, 8. To directly test whether increased xenograft tumor growth could be explained by Noggin-mediated blockade of BMP-2/4 effects on tumor cell proliferation, we generated LNCaP xenografts containing stromal cells over-expressing Noggin. Tumor cells in these xenografts exhibited decreased Id-1 and reduced SMAD phosphorylation, but tumor growth was not altered. We conclude that tumor cell Shh expression can induce significant changes in expression of BMP ligands and inhibitors in the stromal microenvironment but that acceleration of LNCaP xenograft tumor growth by Shh over-expression cannot be attributed solely to increased Noggin expression in the tumor stroma.     

Molecular pathogenesis of pancreatic cancer: advances and challenges

Pancreatic ductal adenocarcinoma (PDAC) is still a devastating and incurable disease with a median survival of 3-6 months and a 5-year survival rate of 1-4% when all stages are considered. Although crucial advances in our understanding of the molecular pathogenesis of the disease have been made, the exceptional aggressiveness of PDAC remains largely unexplained. Some key results will probably direct future PDAC research activities. For example, recent identification of pancreatic tumor stem cells has stimulated the debate over the cell of origin. Further, powerful new genetically engineered mouse models support the concept that stepwise progression of epithelial precursor lesions leads to invasive PDAC as a result of accumulating mutations in K-ras, INK4A/ARF, TP53 and DPC4; these models accentuate the initiating function of the K-ras mutation. Established PDAC exhibits all the classic hallmarks of cancer, including self-sufficiency in growth signals, insensitivity to anti-growth signals, evasion of apoptosis, limitless replicative potential, sustained angiogenesis, tissue invasion, and metastasis. This review provides an overview of the molecular machinery that PDAC utilizes to acquire these tumorigenic capacities. Moreover, recent advances have identified essential elements of key pathways partly recapitulating developmental signals, and of the tumor microenvironment that promotes tumor growth through the complex interplay of its different cellular components. In spite of progress in molecular research, there is still a dichotomy between the encouraging results obtained with targeted interference of numerous oncogenic pathways in vitro and a lack of significant improvement in clinical detection and survival. Thus our primary challenge remains to translate the solid knowledge of genetic and epigenetic alterations in PDAC into clinical tools which can be used for early diagnosis and effective therapy.     

Cyclooxygenase-2 Inhibition Attenuates Abdominal Aortic Aneurysm Progression in Hyperlipidemic Mice

Abdominal aortic aneurysms (AAAs) are a chronic inflammatory disease that increase the risk of life-threatening aortic rupture. In humans, AAAs have been characterized by increased expression of cyclooxygenase-2 and the inactivation of COX-2 prior to disease initiation reduces AAA incidence in a mouse model of the disease. The current study examined the effectiveness of selective cyclooxygenase-2 (COX-2) inhibition on reducing AAA progression when administered after the initiation of AAA formation. AAAs were induced in hyperlipidemic apolipoprotein E-deficient mice by chronic angiotensin II (AngII) infusion and the effect of treatment with the COX-2 inhibitor celecoxib was examined when initiated at different stages of the disease. Celecoxib treatment that was started 1 week after initiating AngII infusion reduced AAA incidence by 61% and significantly decreased AAA severity. Mice treated with celecoxib also showed significantly reduced aortic rupture and mortality. Treatment with celecoxib that was started at a late stage of AAA development also significantly reduced AAA incidence and severity. Celecoxib treatment significantly increased smooth muscle alpha-actin expression in the abdominal aorta and did not reduce expression of markers of macrophage-dependent inflammation. These findings indicate that COX-2 inhibitor treatment initiated after formation of AngII-induced AAAs effectively reduces progression of the disease in hyperlipidemic mice.