Abnormal expression of Nek2 in pancreatic ductal adenocarcinoma: a novel marker for prognosis

Nek2 is a serine/threonine kinase that has a critical role in mitosis during the cell division process. Despite its importance in centrosome regulation and spindle formation, no direct binders are reported between human pancreatic cancer and Nek2 protein. Our aim in studying Nek2 expression and survival in PDA patients is to determine whether Nek2 is a valuable prognostic factor in PDA tumorigenesis. We found that Nek2 mRNA was elevated in PDA tissues. A high level of expression of Nek2 was significantly correlated with histological differentiation (P=0.042), lymph node metastasis (P=0.003) and tumor stage (P=0.001). Patients with a high Nek2 expression had a significantly worse overall survival (OS) than those patients with low Nek2 expression (P=0.002). Univariate and multivariate analysis revealed that high expression of Nek2 could serve as an independent predictor of poor prognosis. These results indicate that Nek2 could be a promising prognostic molecular marker and an attractive therapeutic target for PDA.

CHD7 expression predicts survival outcomes in patients with resected pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with poor outcomes with current therapies. Gemcitabine is the primary adjuvant drug used clinically, but its effectiveness is limited. In this study, our objective was to use a rationale-driven approach to identify novel biomarkers for outcome in patients with early-stage resected PDAC treated with adjuvant gemcitabine. Using a synthetic lethal screen in human PDAC cells, we identified 93 genes, including 55 genes linked to DNA damage responses (DDR), that demonstrated gemcitabine sensitization when silenced, including CHD7, which functions in chromatin remodeling. CHD7 depletion sensitized PDAC cells to gemcitabine and delayed their growth in tumor xenografts. Moreover, CHD7 silencing impaired ATR-dependent phosphorylation of CHK1 and increased DNA damage induced by gemcitabine. CHD7 was dysregulated, ranking above the 90th percentile in differential expression in a panel of PDAC clinical specimens, highlighting its potential as a biomarker. Immunohistochemical analysis of specimens from 59 patients with resected PDAC receiving adjuvant gemcitabine revealed that low CHD7 expression was associated with increased recurrence-free survival (RFS) and overall survival (OS), in univariate and multivariate analyses. Notably, CHD7 expression was not associated with RFS or OS for patients not receiving gemcitabine. Thus, low CHD7 expression was correlated selectively with gemcitabine sensitivity in this patient population. These results supported our rationale-driven strategy to exploit dysregulated DDR pathways in PDAC to identify genetic determinants of gemcitabine sensitivity, identifying CHD7 as a novel biomarker candidate to evaluate further for individualizing PDAC treatment.

Attenuation of hedgehog acyltransferase-catalyzed sonic Hedgehog palmitoylation causes reduced signaling, proliferation and invasiveness of human carcinoma cells

Overexpression of Hedgehog family proteins contributes to the aetiology of many cancers. To be highly active, Hedgehog proteins must be palmitoylated at their N-terminus by the MBOAT family multispanning membrane enzyme Hedgehog acyltransferase (Hhat). In a pancreatic ductal adenocarcinoma (PDAC) cell line PANC-1 and transfected HEK293a cells Hhat localized to the endoplasmic reticulum. siRNA knockdown showed that Hhat is required for Sonic hedgehog (Shh) palmitoylation, for its assembly into high molecular weight extracellular complexes and for functional activity. Hhat knockdown inhibited Hh autocrine and juxtacrine signaling, and inhibited PDAC cell growth and invasiveness in vitro. In addition, Hhat knockdown in a HEK293a cell line constitutively expressing Shh and A549 human non-small cell lung cancer cells inhibited their ability to signal in a juxtacrine/paracrine fashion to the reporter cell lines C3H10T1/2 and Shh-Light2. Our data identify Hhat as a key player in Hh-dependent signaling and tumour cell transformed behaviour.

mTOR is a promising therapeutical target in a subpopulation of pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal disease, unusually resistant against therapy. It is generally felt that stratification of patients for personalized medicine is the way forward. Here, we report that a subpopulation of PDACs shows strong activation of the mTOR signaling cassette. Moreover, we show that inhibition of mTOR in pancreatic cancer cell lines showing high levels of mTOR signaling is associated with cancer cell death. Finally, we show using fine needle biopsies the existence of a subpopulation of PDAC patients with high activation of the mTOR signaling cassette and provide evidence that inhibition of mTOR might be clinically useful for this group. Thus, our results define an unrecognized subpopulation of PDACs, characterized by high activation of mTOR and show that identification of this specific patient group in the early phase of diagnosis is feasible.

Pancreatic satellite cells derived galectin-1 increase the progression and less survival of pancreatic ductal adenocarcinoma

BACKGROUND

Galectin-1, a member of carbohydrate-binding proteins with a polyvalent function on tumor progression, was found strongly expressed in pancreatic satellite cells (PSCs), which partner in crime with cancer cells and promote the development of pancreatic ductal adenocarcinoma (PDAC). We evaluated the effects of PSCs derived Galectin-1 on the progression of PDAC, as well as the tumor establishment and development in mouse xenografts.

METHODS

The relationship between immunohistochemistry staining intensity of Galectin-1 and clinicopathologic variables were assessed in 66 PDAC tissues, 18 chronic pancreatitis tissues and 10 normal controls. The roles of PSCs isolated from PDAC and normal pancreas on the proliferative activity, MMP2 and MMP9 expression, and the invasion of CFPAC-1 in the co-cultured system, as well as on the tumor establishment and development in mouse xenografts by mixed implanting with CFPAC-1 subcutaneously were evaluated.

RESULTS

Galectin-1 expression was gradually increased from normal pancreas (negative), chronic pancreatitis (weak) to PDAC (strong), in which Galectin-1 expression was also increased from well, moderately to poorly differentiated PDAC. Galectin-1 staining intensity of pancreatic cancer tissue was associated with increase in tumor size, lymph node metastasis, perineural invasion and differentiation and UICC stage, and served as the independent prognostic indicator of poor survival of pancreatic cancer. In vitro and in vivo experiments indicated that TGF-β1 upregulated Galectin-1 expression in PSCs, which could further promotes the proliferative activity, MMP2 and MMP9 expression, and invasion of pancreatic cancer cells, as well as the tumor establishment and growth.

CONCLUSION

Galectin-1 expression in stromal cells of pancreatic cancer suggests that this protein plays a role in the promotion of cancer cells invasion and metastasis and provides a therapeutic target for the treatment of pancreatic cancer.

cAMP inhibits migration, ruffling and paxillin accumulation in focal adhesions of pancreatic ductal adenocarcinoma cells: effects of PKA and EPAC

We demonstrated that increasing intracellular cAMP concentrations result in the inhibition of migration of PANC-1 and other pancreatic ductal adenocarcinoma (PDAC) cell types. The rise of cAMP was accompanied by rapid and reversible cessation of ruffling, by inhibition of focal adhesion turnover and by prominent loss of paxillin from focal adhesions. All these phenomena develop rapidly suggesting that cAMP effectors have a direct influence on the cellular migratory apparatus. The role of two primary cAMP effectors, exchange protein activated by cAMP (EPAC) and protein kinase A (PKA), in cAMP-mediated inhibition of PDAC cell migration and migration-associated processes was investigated. Experiments with selective activators of EPAC and PKA demonstrated that the inhibitory effect of cAMP on migration, ruffling, focal adhesion dynamics and paxillin localisation is mediated by PKA, whilst EPAC potentiates migration.

Aberrant DNA methyltransferase expression in pancreatic ductal adenocarcinoma development and progression

BACKGROUND

Altered gene methylation, regulated by DNA methyltransferases (DNMT) 1, 3a and 3b, contributes to tumorigenesis. However, the role of DNMT in pancreatic ductal adenocarcinoma (PDAC) remains unknown.

METHODS

Expression of DNMT 1, 3a and 3b was detected in 88 Pancreatic ductal adenocarcinoma (PDAC) and 10 normal tissue samples by immunohistochemistry. Changes in cell viability, cell cycle distribution, and apoptosis of PDAC cell lines (Panc-1 and SW1990) were assessed after transfection with DNMT1 and 3b siRNA. Levels of CDKN1A, Bcl-2 and Bax mRNA were assessed by qRT-PCR, and methylation of the Bax gene promoter was assayed by methylation-specific PCR (MSP).

RESULTS

DNMT1, 3a and 3b proteins were expressed in 46.6%, 23.9%, and 77.3% of PDAC tissues, respectively, but were not expressed in normal pancreatic tissues. There was a co-presence of DNMT3a and DNMT3b expression and an association of DNMT1 expression with alcohol consumption and poor overall survival. Moreover, knockdown of DNMT1 and DNMT3b expression significantly inhibited PDAC cell viability, decreased S-phase but increased G1-phase of the cell cycle, and induced apoptosis. Molecularly, expression of CDKN1A and Bax mRNA was upregulated, and the Bax gene promoter was demethylated. However, a synergistic effect of combined DNMT1 and 3b knockdown was not observed.

CONCLUSION

Expression of DNMT1, 3a and 3b proteins is increased in PDAC tissues, and DNMT1 expression is associated with poor prognosis of patients. Knockdown of DNMT1 and 3b expression arrests tumor cells at the G1 phase of the cell cycle and induces apoptosis. The data suggest that DNMT knockdown may be a novel treatment strategy for PDAC.

Anti-tumour efficacy of capecitabine in a genetically engineered mouse model of pancreatic cancer

Capecitabine (CAP) is a 5-FU pro-drug approved for the treatment of several cancers and it is used in combination with gemcitabine (GEM) in the treatment of patients with pancreatic adenocarcinoma (PDAC). However, limited pre-clinical data of the effects of CAP in PDAC are available to support the use of the GEMCAP combination in clinic. Therefore, we investigated the pharmacokinetics and the efficacy of CAP as a single agent first and then in combination with GEM to assess the utility of the GEMCAP therapy in clinic. Using a model of spontaneous PDAC occurring in Kras(G12D); p53(R172H); Pdx1-Cre (KPC) mice and subcutaneous allografts of a KPC PDAC-derived cell line (K8484), we showed that CAP achieved tumour concentrations (∼25 µM) of 5-FU in both models, as a single agent, and induced survival similar to GEM in KPC mice, suggesting similar efficacy. In vitro studies performed in K8484 cells as well as in human pancreatic cell lines showed an additive effect of the GEMCAP combination however, it increased toxicity in vivo and no benefit of a tolerable GEMCAP combination was identified in the allograft model when compared to GEM alone. Our work provides pre-clinical evidence of 5-FU delivery to tumours and anti-tumour efficacy following oral CAP administration that was similar to effects of GEM. Nevertheless, the GEMCAP combination does not improve the therapeutic index compared to GEM alone. These data suggest that CAP could be considered as an alternative to GEM in future, rationally designed, combination treatment strategies for advanced pancreatic cancer.

MAP3K10 promotes the proliferation and decreases the sensitivity of pancreatic cancer cells to gemcitabine by upregulating Gli-1 and Gli-2

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal human malignancies and is regulated by Sonic Hedgehog (Shh) signaling. Recently, MAP3K10 has been shown to regulate Shh signaling, suggesting a role for MAP3K10 in the tumorigenesis of PDAC. We determined the expression status of MAP3K10 in PDAC tissues and cell lines, and analyzed the viability and cell proliferation of PDAC cells with an overexpression or knockdown of MAP3K10 in vitro. MAP3K10 was upregulated in PDAC tissues and cell lines. Overexpression of MAP3K10 promoted the proliferation and decreased the gemcitabine sensitivity of pancreatic cancer cells. In contrast, knockdown of MAP3K10 significantly decreased cell proliferation and sensitized cells to gemcitabine. However, neither overexpression nor knockdown of MAP3K10 affected cell migration. Moreover, overexpression of MAP3K10 resulted in upregulation of Gli-1 and Gli-2 in PDAC cells. Our results indicate a novel and important role for MAP3K10 in the proliferation and chemoresistance of PDAC. Our study suggests that targeting MAP3K10 is a potential strategy for the development of alternative therapies for pancreatic cancers.

Plk1 phosphorylation of orc2 and hbo1 contributes to gemcitabine resistance in pancreatic cancer

Although gemcitabine is the standard chemotherapeutic drug for treatment of pancreatic cancer, almost all patients eventually develop resistance to this agent. Previous studies identified Polo-like kinase 1 (Plk1) as the mediator of gemcitabine resistance, but the molecular mechanism remains unknown. In this study, we show that Plk1 phosphorylation of Orc2 and Hbo1 mediates the resistance to gemcitabine. We show that the level of Plk1 expression positively correlates with gemcitabine resistance, both in pancreatic cancer cells and xenograft tumors. Overexpression of Plk1 increases gemcitabine resistance, while inhibition of Plk1 sensitizes pancreatic cancer cells to gemcitabine treatment. To validate our findings, we show that inhibition of Plk1 sensitizes tumors to gemcitabine treatment in a mouse xenograft study. Mechanistically, we find that Plk1 phosphorylation of Orc2 maintains DNA replication on gemcitabine treatment. Furthermore, Plk1 phosphorylation of Hbo1 transcriptionally increases cFos expression and consequently elevates its target multidrug resistance 1 (MDR1), which was previously reported to confer chemotherapeutic drug resistance. Knockdown of cFos or MDR1 sensitizes gemcitabine-resistant cells to gemcitabine treatment. Finally, pancreatic cancer cells expressing Plk1-unphosphorylatable mutants of Orc2 or Hbo1 are more sensitive to gemcitabine than cells expressing wild-type Orc2 or Hbo1. In short, our study provides a mechanism for Plk1-mediated gemcitabine resistance, suggesting that Plk1 is a promising target for treatment of gemcitabine-resistant pancreatic cancer.

Global identification of peptidase specificity by multiplex substrate profiling

We developed a simple and rapid multiplex substrate-profiling method to reveal the substrate specificity of any endo- or exopeptidase using liquid chromatography-tandem mass spectrometry sequencing. We generated a physicochemically diverse library of peptides by incorporating all combinations of neighbor and near-neighbor amino acid pairs into decapeptide sequences that are flanked by unique dipeptides at each terminus. Addition of a panel of evolutionarily diverse peptidases to a mixture of these tetradecapeptides generated information on prime and nonprime sites as well as on substrate specificity that matched or expanded upon known substrate motifs. This method biochemically confirmed the activity of the klassevirus 3C protein responsible for polypeptide processing and allowed granzyme B substrates to be ranked by enzymatic turnover efficiency using label-free quantitation of precursor-ion abundance. Additionally, the proteolytic secretions from schistosome parasitic flatworm larvae and a pancreatic cancer cell line were deconvoluted in a subtractive strategy using class-specific peptidase inhibitors.

Ribonucleotide reductase M2 does not predict survival in patients with resectable pancreatic adenocarcinoma

BACKGROUND

Ribonucleotide reductase M2 (RRM2) was associated with pancreatic tumor progression and resistance to gemcitabine. This study aimed to determine if RRM2 protein expression was prognostic in patients with resectable pancreatic adenocarcinoma and predictive of adjuvant gemcitabine benefit.

METHODS

117 patients underwent tumor resection for pancreatic adenocarcinoma from 10/1999 to 12/2007. We constructed tissue microarrays from paraffin-embedded tumors and determined RRM2 protein expression using immunohistochemistry and grouped as negative or positive. We estimated overall survival (OS) and progression-free survival (PFS) using the Kaplan-Meier method and examined the prognostic and predictive value of RRM2 expression using Cox proportional hazards model.

RESULTS

RRM2 expression showed no prognostic value in the entire group regarding OS (median OS 30.9 months in RRM2-positive versus 13.7 months in RRM2-negative, P = 0.26) and PFS (median OS 20.6 months in RRM2-positive versus 11.8 months in RRM2-negative, P = 0.46). RRM2 expression did not predict adjuvant gemcitabine benefit in the subgroup of 44 patients who received gemcitabine therapy (median OS 31.2 versus 15.2 months, P = 0.62; median PFS 11.3 versus 14.0 months, P = 0.35). Cox proportional hazards regression showed no prognostic effect of RRM2 expression on OS and PFS in the subgroup of 44 patients. However, the number of positive lymph nodes and perineural invasion were prognostic factors for OS (HR 1.2, P = 0.005) and for PFS (HR 5.5, P = 0.007), respectively.

CONCLUSION

RRM2 protein expression in pancreatic adenocarcinoma is neither prognostic nor predictive of adjuvant gemcitabine benefit in patients with resectable pancreatic adenocarcinoma.

nab-Paclitaxel potentiates gemcitabine activity by reducing cytidine deaminase levels in a mouse model of pancreatic cancer

Nanoparticle albumin-bound (nab)-paclitaxel, an albumin-stabilized paclitaxel formulation, demonstrates clinical activity when administered in combination with gemcitabine in patients with metastatic pancreatic ductal adenocarcinoma (PDA). The limited availability of patient tissue and exquisite sensitivity of xenografts to chemotherapeutics have limited our ability to address the mechanistic basis of this treatment regimen. Here, we used a mouse model of PDA to show that the coadministration of nab-paclitaxel and gemcitabine uniquely demonstrates evidence of tumor regression. Combination treatment increases intratumoral gemcitabine levels attributable to a marked decrease in the primary gemcitabine metabolizing enzyme, cytidine deaminase. Correspondingly, paclitaxel reduced the levels of cytidine deaminase protein in cultured cells through reactive oxygen species-mediated degradation, resulting in the increased stabilization of gemcitabine. Our findings support the concept that suboptimal intratumoral concentrations of gemcitabine represent a crucial mechanism of therapeutic resistance in PDA and highlight the advantages of genetically engineered mouse models in preclinical therapeutic trials.

SIGNIFICANCE

This study provides mechanistic insight into the clinical cooperation observed between gemcitabine and nab-paclitaxel in the treatment of pancreatic cancer.

Multivariate analysis of immunohistochemical evaluation of protein expression in pancreatic ductal adenocarcinoma reveals prognostic significance for persistent Smad4 expression only

Background

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis with a 5-year survival rate of <5% and an average survival of only 6 months. Although advances have been made in understanding the pathogenesis of PDAC in the last decades, overall survival has not changed. Various clinicopathological and immunohistological variables have been associated with survival time but the exact role that these variables play in relation to survival is not clear.

Methods and results

To examine how the variables affected survival independently, multivariate analysis was conducted in a study group of 78 pancreatic ductal adenocarcinomas. The analysis included clinicopathological parameters and protein expression examined by immunohistochemistry of p53, Smad4, Axl, ALDH, MSH2, MSH6, MLH1 and PMS2. Lymph node ratio <0.2 (p = 0.004), tumor free resection margins (p = 0.044) and Smad4 expression (p = 0.004) were the only independent prognostic variables in the multivariate analysis. Expression of the other proteins examined was not significantly related to survival.

Conclusions

Discrepancies with other studies in this regard are likely due to differences in quantification of immunohistochemical staining and the lack of multivariate analysis. It underscores the importance to standardize the methods used for the application of immunohistochemistry in prognostic studies.

[The role of matrix metalloproteinases in pancreatic ductal adenocarcinoma]

Matrix metalloproteinases-7, -9 (MMP) are crucial factors for prognosis of pancreatic ductal adenocarcinoma (PDA). The expressions of MMP-2, 7, 9 increased in 60 patients with PDA and depended from stage of disease. Metastasis and invasive growth of tumor correlated with increase of MMP production and decrease of MMP inhibitors' expression, stimulated invasive growth of tumor.

Overexpression of GalNAc-transferase GalNAc-T3 promotes pancreatic cancer cell growth

O-linked glycans of secreted and membrane-bound proteins have an important role in the pathogenesis of pancreatic cancer by modulating immune responses, inflammation and tumorigenesis. A critical aspect of O-glycosylation, the position at which proteins are glycosylated with N-acetyl-galactosamine on serine and threonine residues, is regulated by the substrate specificity of UDP-GalNAc:polypeptide N-acetylgalactosaminyl-transferases (GalNAc-Ts). Thus, GalNAc-Ts regulate the first committed step in O-glycosylated protein biosynthesis, determine sites of O-glycosylation on proteins and are important for understanding normal and carcinoma-associated O-glycosylation. We have found that one of these enzymes, GalNAc-T3, is overexpressed in human pancreatic cancer tissues and suppression of GalNAc-T3 significantly attenuates the growth of pancreatic cancer cells in vitro and in vivo. In addition, suppression of GalNAc-T3 induces apoptosis of pancreatic cancer cells. Our results indicate that GalNAc-T3 is likely involved in pancreatic carcinogenesis. Modification of cellular glycosylation occurs in nearly all types of cancer as a result of alterations in the expression levels of glycosyltransferases. We report guanine the nucleotide-binding protein, α-transducing activity polypeptide-1 (GNAT1) as a possible substrate protein of GalNAc-T3. GalNAc-T3 is associated with O-glycosylation of GNAT1 and affects the subcellular distribution of GNAT1. Knocking down endogenous GNAT1 significantly suppresses the growth/survival of PDAC cells. Our results imply that GalNAc-T3 contributes to the function of O-glycosylated proteins and thereby affects the growth and survival of pancreatic cancer cells. Thus, substrate proteins of GalNAc-T3 should serve as important therapeutic targets for pancreatic cancers.

Inhibition of focal adhesion kinase by PF-562,271 inhibits the growth and metastasis of pancreatic cancer concomitant with altering the tumor microenvironment

Current therapies for pancreatic ductal adenocarcinoma (PDA) target individual tumor cells. Focal adhesion kinase (FAK) is activated in PDA, and levels are inversely associated with survival. We investigated the effects of PF-562,271 (a small-molecule inhibitor of FAK/PYK2) on (i) in vitro migration, invasion, and proliferation; (ii) tumor proliferation, invasion, and metastasis in a murine model; and (iii) stromal cell composition in the PDA microenvironment. Migration assays were conducted to assess tumor and stromal cell migration in response to cellular factors, collagen, and the effects of PF-562,271. An orthotopic murine model was used to assess the effects of PF-562,271 on tumor growth, invasion, and metastasis. Proliferation assays measured PF-562,271 effects on in vitro growth. Immunohistochemistry was used to examine the effects of FAK inhibition on the cellular composition of the tumor microenvironment. FAK and PYK2 were activated and expressed in patient-derived PDA tumors, stromal components, and human PDA cell lines. PF-562,271 blocked phosphorylation of FAK (phospho-FAK or Y397) in a dose-dependent manner. PF-562,271 inhibited migration of tumor cells, cancer-associated fibroblasts, and macrophages. Treatment of mice with PF-562,271 resulted in reduced tumor growth, invasion, and metastases. PF-562,271 had no effect on tumor necrosis, angiogenesis, or apoptosis, but it did decrease tumor cell proliferation and resulted in fewer tumor-associated macrophages and fibroblasts than control or gemcitabine. These data support a role for FAK in PDA and suggest that inhibitors of FAK may contribute to efficacious treatment of patients with PDA.

[Expression of dihydropyrimidine dehydrogenase negatively correlated with the prognosis of pancreatic ductal adenocarcinoma]

OBJECTIVE

To detect the expression of dihydropyrimidine dehydrogenase (DPD) in pancreatic ductal adenocarcinoma (PDAC), and to investigate the relationships between DPD expression and the prognosis of PDAC.

METHODS

Immunohistochemistry and tissue microarray techniques were used to exam the expression of DPD in the cancerous tissue in 156 patients admitted from January 2005 to December 2009, including 89 males and 67 females, with the age ranging from 35 to 81 years. The median age was 55 years.

RESULTS

With the positive rate of DPD 55.1%, the expression of DPD was correlated with the differentiation (P = 0.001), TNM staging of tumor (P = 0.021). No relationship was observed between the vessel invasion (P = 0.265), lymphatic metastasis (P = 0.123), neural invasion (P = 0.598) and DPD expression. In the follow-up 117 patients the overall median survival time was 14.2 months, in 58 cases expressed negative, the median survival time was 20.6 months; 39 cases expressed "+" and "++", the median survival time was 12.3 months; 20 cases expressed "+++", the median survival time was 6.8 months. The expression of DPD in pancreatic cancer was correlated with the prognosis of patients, those with higher expression pattern exhibited shorter survival time (P < 0.05). Univariate survival analysis revealed that DPD expression, TNM staging, lymphatic metastasis and neural invasion were factors related to prognosis (P < 0.05), while differentiation levels and vessel invasion were not. Multivariate survival analysis revealed that DPD expression (P = 0.002), lymphatic metastasis (P = 0.000) were two independent prognostic factors.

CONCLUSIONS

The expression levels of DPD was correlated to differentiation levels of pancreatic cancer and TNM staging; those with higher expression of DPD showed shorter survival time. DPD expression, lymphatic metastasis were independent prognostic factors for pancreatic cancer.

Spatial regulation of RhoA activity during pancreatic cancer cell invasion driven by mutant p53

The ability to observe changes in molecular behavior during cancer cell invasion in vivo remains a major challenge to our understanding of the metastatic process. Here, we demonstrate for the first time, an analysis of RhoA activity at a subcellular level using FLIM-FRET (fluorescence lifetime imaging microscopy-fluorescence resonance energy transfer) imaging in a live animal model of pancreatic cancer. In invasive mouse pancreatic ductal adenocarcinoma (PDAC) cells driven by mutant p53 (p53(R172H)), we observed a discrete fraction of high RhoA activity at both the leading edge and rear of cells in vivo which was absent in two-dimensional in vitro cultures. Notably, this pool of active RhoA was absent in noninvasive p53(fl) knockout PDAC cells, correlating with their poor invasive potential in vivo. We used dasatanib, a clinically approved anti-invasive agent that is active in this model, to illustrate the functional importance of spatially regulated RhoA. Dasatanib inhibited the activity of RhoA at the poles of p53(R172H) cells in vivo and this effect was independent of basal RhoA activity within the cell body. Taken together, quantitative in vivo fluorescence lifetime imaging illustrated that RhoA is not only necessary for invasion, but also that subcellular spatial regulation of RhoA activity, as opposed to its global activity, is likely to govern invasion efficiency in vivo. Our findings reveal the utility of FLIM-FRET in analyzing dynamic biomarkers during drug treatment in living animals, and they also show how discrete intracellular molecular pools might be differentially manipulated by future anti-invasive therapies.

Gamma-secretase complexes regulate the responses of human pancreatic ductal adenocarcinoma cells to taxanes

BACKGROUND/AIM

It was previously reported that γ-secretase inhibitors (GSIs) enhance taxane-induced mitotic arrest and apoptosis in colon cancer cells. To enable the development of taxane-based chemotherapy for pancreatic ductal adenocarcinoma (PDAC), this study investigated the molecular mechanisms by which γ-secretase (GS) complexes regulate taxane sensitivity.

MATERIALS AND METHODS

The effect of GS complexes on taxane-induced apoptosis in PDAC cells was evaluated by a cell cycle analysis. GS complexes were examined with small interference RNAs targeted to GS complex-related genes.

RESULTS

GSIs and silencing of presenilin 1 (PS1) did not affect cell proliferation but resulted in enhanced taxane-induced G(2)/M accumulation and apoptosis. Silencing of the Notch gene did not induce these effects. However, PS2-specific silencing suppressed proliferation and taxane-induced apoptosis.

CONCLUSION

Data from this study indicate that GS complexes regulate the response of PDAC to taxanes through GS-dependent and GS-independent mechanisms.

Mutational profiling of kinases in human tumours of pancreatic origin identifies candidate cancer genes in ductal and ampulla of vater carcinomas

Background

Protein kinases are key regulators of cellular processes (such as proliferation, apoptosis and invasion) that are often deregulated in human cancers. Accordingly, kinase genes have been the first to be systematically analyzed in human tumors leading to the discovery that many oncogenes correspond to mutated kinases. In most cases the genetic alterations translate in constitutively active kinase proteins, which are amenable of therapeutic targeting. Tumours of the pancreas are aggressive neoplasms for which no effective therapeutic strategy is currently available.

Methodology/Principal Findings

We conducted a DNA-sequence analysis of a selected set of 35 kinase genes in a panel of 52 pancreatic exocrine neoplasms, including 36 pancreatic ductal adenocarcinoma, and 16 ampulla of Vater cancer. Among other changes we found somatic mutations in ATM, EGFR, EPHA3, EPHB2, and KIT, none of which was previously described in cancers.

Conclusions/Significance

Although the alterations identified require further experimental evaluation, the localization within defined protein domains indicates functional relevance for most of them. Some of the mutated genes, including the tyrosine kinases EPHA3 and EPHB2, are clearly amenable to pharmacological intervention and could represent novel therapeutic targets for these incurable cancers.

Mutations of LKB1 gene in pancreatic ductal adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine in hamsters

To evaluate an involvement of LKB1 gene alteration during pancreatic carcinogenesis, mutations in the LKB1 gene in hamster pancreatic duct adenocarcinomas (PDAs) induced by N-nitrosobis(2-oxopropyl)amine (BOP) were investigated. Female Syrian golden hamsters received 30 mg/kg of BOP followed by repeated exposure to an augmentation pressure regimen consisting of a choline-deficient diet combined with DL-ethionine then L-methionine and a further administration of 20 mg/kg BOP. A total of 10 PDAs obtained 10 weeks after beginning the experiment were examined for mutations using reverse transcription (RT)-polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) analysis. Mutations were detected in 3 out of the 10 PDAs (30.0%). Sequence analysis revealed the identity of these mutations to be a CCC to CCT (Pro to Pro) transition at codon 221, a CCG to CAG (Pro to Gln) transversion at codon 324 and a GAC to GGC (Asp to Gly) transition at codon 343. The LKB1 gene may be involved in the development of PDAs induced by BOP in hamsters.

Use of IHC and newly designed matriptase inhibitors to elucidate the role of matriptase in pancreatic ductal adenocarcinoma

Matriptase, also known as MT-SP1, is a type II transmembrane serine protease strongly implicated in both the development and progression of a variety of epithelial cancers. Evidence comes from studies of its expression in human cancers and from mouse models of spontaneous cancer. Matriptase is considered to be a major activator of two key stimulators of invasive growth, namely hepatocyte growth factor/scatter factor and urokinase-type plasminogen activator. The aim of this study was to examine the role of matriptase in pancreatic ductal adenocarcinoma by expression analysis and functional assays in vitro. Immunohistochemical analysis of matriptase performed on microtissue arrays and large samples of 55 pancreatic ductal adenocarcinomas and on 31 samples of normal pancreatic ducts revealed that although matriptase expression differed greatly in both malignant and normal ductal pancreatic tissue, matriptase scores were significantly (p=0.02) elevated in pancreatic ductal adenocarcinoma compared to normal pancreatic ducts. To evaluate the role of matriptase during development of pancreatic cancer, we studied the effects of newly designed matriptase inhibitors on the processing of the zymogen of urokinase-type plasminogen activator in the human adenocarcinoma cell lines AsPC-1 and BxPC-3. In both cell lines, at 1 microM, all matriptase inhibitors completely prevented zymogen activation. At lower inhibitor concentrations, the degree of inhibition of zymogen processing correlated with the affinities of the inhibitors towards matriptase indicating that this is a specific result of matriptase inhibition. Furthermore, matriptase inhibitors reduced the phosphorylation of the HGF receptor/cMet and the overall cellular invasiveness of the human pancreatic adenocarcinoma cell line AsPC-1. Our findings demonstrate for the first time that matriptase may be involved in the progression of pancreatic ductal adenocarcinoma and that matriptase inhibition may contribute to preventing the progression of this devastating disease.

Prognostic value of thymidine phosphorylase expression for pancreatic cancer

BACKGROUND/AIMS

Thymidine phosphorylase (TP) has an angiogenic activity, but the prognostic value of TP has not been fully validated for pancreatic cancer. The aim of this study was to evaluate TP expression according to clinicopathological parameters to define its prognostic value for pancreatic cancer.

METHODOLOGY

Forty-three patients with pancreatic ductal adenocarcinoma were examined retrospectively. TP expression and intratumoral microvessel density (IMD) were evaluated by immunohistochemistry. TP expression was analyzed according to clinicopathological parameters.

RESULTS

Twenty-eight (65%) of 42 cases showed diffuse cytoplasmic and nucleic TP staining. IMD was significantly higher in TP-positive tumors than in TP-negative tumors (27.7 +/- 8.9 vs. 18.1 +/- 4.4, p < 0.01). TP levels were significantly higher in T3 and T4 tumors than in T1 and T2 tumors (56% vs. 9.3%, respectively, p < 0.05). Patients with TP-positive tumors more frequently developed hepatic recurrence than those with TP-negative tumors after resection (p < 0.01). Patients with TP-positive tumors had a shorter survival than patients with TP-negative tumors (p < 0.05).

CONCLUSION

TP expression can be used as a predictor of hepatic recurrence and as an unfavorable prognostic factor for pancreatic cancer.

K-Ras promotes angiogenesis mediated by immortalized human pancreatic epithelial cells through mitogen-activated protein kinase signaling pathways

Activating point mutations in the K-Ras oncogene are among the most common genetic alterations in pancreatic cancer, occurring early in the progression of the disease. However, the function of mutant K-Ras activity in tumor angiogenesis remains poorly understood. Using human pancreatic duct epithelial (HPDE) and K-Ras4B(G12V)-transformed HPDE (HPDE-KRas) cells, we show that activated K-Ras significantly enhanced the production of angiogenic factors including CXC chemokines and vascular endothelial growth factor (VEGF). Western blot analysis revealed that K-Ras activation promoted the phosphorylation of Raf/mitogen-activated protein kinase kinase-1/2 (MEK1/2) and expression of c-Jun. MEK1/2 inhibitors, U0126 and PD98059, significantly inhibited the secretion of both CXC chemokines and VEGF, whereas the c-Jun NH(2)-terminal kinase inhibitor SP600125 abrogated only CXC chemokine production. To further elucidate the biological functions of oncogenic K-Ras in promoting angiogenesis, we did in vitro invasion and tube formation assays using human umbilical vein endothelial cells (HUVEC). HUVEC cocultured with HPDE-KRas showed significantly enhanced invasiveness and tube formation as compared with either control (without coculture) or coculture with HPDE. Moreover, SB225002 (a CXCR2 inhibitor) and 2C3 (an anti-VEGF monoclonal antibody) either alone or in a cooperative manner significantly reduced the degree of both Ras-dependent HUVEC invasiveness and tube formation. Similar results were obtained using another pair of immortalized human pancreatic duct-derived cells, E6/E7/st and its oncogenic K-Ras variant, E6/E7/Ras/st. Taken together, our results suggest that angiogenesis is initiated by paracrine epithelial secretion of CXC chemokines and VEGF downstream of activated oncogenic K-Ras, and that this vascular maturation is in part dependent on MEK1/2 and c-Jun signaling.