Pancreatic cancer

Pancreatic intraepithelial neoplasia and ductal adenocarcinoma induced by DMBA in mice: effects of alcohol and caffeine

PURPOSE

To evaluate the effects of alcohol and caffeine in a pancreatic carcinogenesis mouse model induced by 7,12-dimethylbenzantracene (DMBA), according to the PanIN classification system.

METHODS

120 male, Mus musculus, CF-1 mice were divided into four groups. Animals received either water or caffeine or alcohol or alcohol + caffeine in their drinking water. In all animals, 1 mg of DMBA was implanted into the head of the pancreas. After 30 days, euthanasia was performed; excised pancreata were then fixed in formalin, stained with hematoxylin-eosin and categorized as follows: normal ducts, reactive hyperplasia, PanIN-1A, PanIN-1B, PanIN-2, PanIN-3 or adenocarcinoma.

RESULTS

PanIN lesions were verified in all groups. Adenocarcinoma was detected in 15% of animals in the caffeine group, 16.6% in the water group, 23.8% in the alcohol + caffeine group and 52.9% in the alcohol group (P<0.05).

CONCLUSIONS

The experimental pancreatic carcinogenesis mouse model using DMBA effectively induces PanIN lesions and pancreatic adenocarcinoma. This study verified the association between alcohol use and pancreatic adenocarcinoma; caffeine did not present the same effect.

Human pancreatic duct epithelial cell model for KRAS transformation

Mutations on the KRAS gene occur early during pancreatic duct cell carcinogenesis and have been identified in up to 90% of ductal adenocarcinoma. However, the functional role of KRAS mutations in the malignant transformation of normal pancreatic duct epithelial cells into cancer cells remains unknown. We have developed an in vitro model for KRAS transformation using near-normal HPV-16E6E7-immortalized human pancreatic ductal epithelial (HPDE-E6E7) cells. The expression of mutant KRAS(G12V) in HPDE cells by retroviral transduction resulted in weak tumorigenic transformation, with tumors formed in 50% of immune-deficient scid mice implanted by these KRAS-transformed cells. The model provides an opportunity to dissect further the molecular and cellular mechanisms associated with human pancreatic duct cell carcinogenesis.

Gene expression profiles in primary pancreatic tumors and metastatic lesions of Ela-c-myc transgenic mice

Background

Pancreatic carcinoma usually is a fatal disease with no cure, mainly due to its invasion and metastasis prior to diagnosis. We analyzed the gene expression profiles of paired primary pancreatic tumors and metastatic lesions from Ela-c-myc transgenic mice in order to identify genes that may be involved in the pancreatic cancer progression. Differentially expressed selected genes were verified by semi-quantitative and quantitative RT-PCR. To further evaluate the relevance of some of the selected differentially expressed genes, we investigated their expression pattern in human pancreatic cancer cell lines with high and low metastatic potentials.

Results

Data indicate that genes involved in posttranscriptional regulation were a major functional category of upregulated genes in both primary pancreatic tumors (PT) and liver metastatic lesions (LM) compared to normal pancreas (NP). In particular, differential expression for splicing factors, RNA binding/pre-mRNA processing factors and spliceosome related genes were observed, indicating that RNA processing and editing related events may play critical roles in pancreatic tumor development and progression. High expression of insulin growth factor binding protein-1 (Igfbp1) and Serine proteinase inhibitor A1 (Serpina1), and low levels or absence of Wt1 gene expression were exclusive to liver metastatic lesion samples.

Conclusion

We identified Igfbp1, Serpina1 and Wt1 genes that are likely to be clinically useful biomarkers for prognostic or therapeutic purposes in metastatic pancreatic cancer, particularly in pancreatic cancer where c-Myc is overexpressed.

An in vivo platform for translational drug development in pancreatic cancer

Effective development of targeted anticancer agents includes the definition of the optimal biological dose and biomarkers of drug activity. Currently available preclinical models are not optimal to this end. We aimed at generating a model for translational drug development using pancreatic cancer as a prototype. Resected pancreatic cancers from 14 patients were xenografted and expanded in successive groups of nude mice to develop cohorts of tumor-bearing mice suitable for drug therapy in simulated early clinical trials. The xenografted tumors maintain their fundamental genotypic features despite serial passages and recapitulate the genetic heterogeneity of pancreatic cancer. The in vivo platform is useful for integrating drug screening with biomarker discovery. Passages of tumors in successive cohorts of mice do not change their susceptibility to anticancer agents and represent a perpetual live bank, facilitating the application of new technologies that will result in the creation of an integrated stable database of tumor-drug response data and biomarkers.

Intraperitoneal gemcitabine pharmacokinetics: a pilot and pharmacokinetic study in patients with advanced adenocarcinoma of the pancreas

BACKGROUND

The pyrimidine analogue gemcitabine (2', 2'-difluorodeoxycitidine, dFdC) is active against pancreatic cancer, and its high clearance (CL(tb)) and low incidence of local toxicity make it an excellent candidate for evaluation as intraperitoneal (IP) therapy. We designed a dosing schema that used multiple sequential exchanges of a peritoneal dialysate containing dFdC in an effort to produce prolonged IP dFdC exposure.

METHODS

As part of a study involving multi-modality therapy for advanced pancreatic adenocarcinoma, patients were treated with four 6-h IP dwells of dFdC (50 mg/m(2) in 2 l) over a 24-h period. A second 24-h cycle of IP dFdC therapy was repeated 1 week later. Each exchange of dialysate contained 50 mg/m(2) dFdC in 2 l of commercial 1.5% dextrose dialysis solution. Plasma and peritoneal fluid were analyzed by HPLC to determine concentrations of dFdC and its inactive metabolite 2', 2' difluorodeoxyuridine (dFdU). Clinical data were recorded to note drug toxicity and response.

RESULTS

Nine patients underwent IP dFdC therapy, and eight were able to receive two cycles. There were no recorded significant toxicities. Low plasma dFdC concentrations (<1 microg/ml) were present transiently in seven of nine patients, and dFdC was not detectable in the plasma of the other two. Plasma dFdU concentrations were low but increased gradually until 12 h and then declined little if any. IP dFdC concentrations declined rapidly, and dFdC was seldom measurable prior to administration of the next scheduled 6-h dwell. dFdU concentrations in peritoneal fluid were very low (<0.5 microg/ml) throughout treatment. The mean area under the concentration versus time curve (AUC) for dFdC in peritoneal fluid was 182 microg/ml x h, which was approximately 70x the AUC of dFdC reported in the ascites of a patient undergoing systemic dFdC therapy.

CONCLUSIONS

IP dFdC was well tolerated, and no significant toxicities were noted. The rapid decrease in peritoneal dFdC concentrations and low concentrations of IP dFdU imply almost total absorption of IP-administered dFdC. Little, if any, dFdC could be detected in plasma, but the steady-state plasma dFdU concentrations also imply absorption and inactivation of virtually all IP-administered dFdC. These findings are consistent with the known high CL(tb) and low incidence of local toxicity of dFdC and argue for its further evaluation as a drug for IP therapy.

Evaluation of matrix metalloproteinase 7 in plasma and pancreatic juice as a biomarker for pancreatic cancer

Differentiating between periampullary carcinoma and chronic pancreatitis with an inflammatory mass is difficult. Consequently, 6% to 9% of pancreatic resections for suspected carcinoma are done inappropriately for chronic pancreatitis. Here, we test if matrix metalloproteinase 7 (MMP-7), a secreted protease frequently expressed in pancreatic carcinoma, can be measured in plasma, pancreatic, and duodenal juice, and if it can distinguish between periampullary carcinoma and chronic pancreatitis. Ninety-four patients who underwent pancreatic surgery for a (peri)pancreatic neoplasm (n = 63) or chronic pancreatitis (n = 31) were analyzed. Median plasma MMP-7 levels were significantly higher in carcinoma (1.95 ng/mL; interquartile range, 0.81-3.22 ng/mL) compared with chronic pancreatitis and benign disease (0.83 ng/mL; interquartile range, 0.25-1.21 ng/mL; P < 0.01). MMP-7 levels in pancreatic juice were higher, although not significantly, in carcinoma (62 ng/mg protein; interquartile range, 18-241 ng/mg protein) compared with chronic pancreatitis and benign disease (23 ng/mg protein; interquartile range, 8.5-99 ng/mg protein; P = 0.17). MMP-7 levels in duodenal juice were universally low. At an arbitrary cutoff of 1.5 ng/mL in plasma, positive and negative predictive values were 83% and 57%, respectively, values comparable to those of today's most common pancreatic tumor marker, carbohydrate antigen 19-9 (CA19-9; 83% and 53%, respectively). Positive and negative likelihood ratios for plasma MMP-7 were 3.35 and 0.52, respectively. The area under the receiver operating characteristic curve for MMP-7 was 0.73 (95% confidence interval, 0.63-0.84) and for CA19-9, 0.75 (95% confidence interval, 0.64-0.85). Combined MMP-7 and CA19-9 assessment gave a positive predictive value of 100%. Thus, plasma MMP-7 levels discriminated between patients with carcinoma and those with chronic pancreatitis or benign disease. The diagnostic accuracy of plasma MMP-7 alone is not sufficient to determine treatment strategy in patients with a periampullary mass, but combined evaluation of plasma MMP-7 with CA19-9 and other markers may be clinically useful.

Probing pancreatic disease using tissue optical spectroscopy

Pancreatic adenocarcinoma, one of the leading causes of cancer death in the United States, has a five-year survival rate of only 4%. Present detection methods do not provide accurate diagnosis in the disease's early stages. To investigate whether optical spectroscopy could potentially aid in early diagnosis and improve survival rates, reflectance and fluorescence spectroscopies were employed for the first time in a limited pilot study to probe freshly excised human pancreatic tissues (normal, pancreatitis, and adenocarcinoma) and in vivo human pancreatic cancer xenografts in nude mice. In human pancreatic tissues, measurements were associated with endogenous fluorophores NAD(P)H and collagen, as well as tissue optical properties, with larger relative collagen content detected in adenocarcinoma and pancreatitis than normal. Good correspondence was observed between spectra from adenocarcinoma and cancer xenograft tissues. Reflectance data indicated that adenocarcinoma had higher reflectance in the 430- to 500-nm range compared to normal and pancreatitis tissues. The observed significant differences between the fluorescence and reflectance properties of normal, pancreatitis, and adenocarcinoma tissues present an opportunity for future statistical validation on a larger patient pool and indicate a potential application of multimodal optical spectroscopy to differentiate between diseased and normal pancreatic tissue states.

Epithelial to mesenchymal transition: expression of the regulators snail, slug, and twist in pancreatic cancer

PURPOSE

Epithelial to mesenchymal transitions are vital for tumor growth and metastasis. Several inducers of epithelial to mesenchymal transition are transcription factors that repress E-cadherin expression, such as Snail, Slug, and Twist. In this study, we aimed to examine the expression of these transcription factors in pancreatic cancer.

EXPERIMENTAL DESIGN

The expression of Snail, Slug, and Twist was detected by immunohistochemistry in tissue samples from patients with pancreatic ductal adenocarcinoma. Five human pancreatic cancer cell lines (AsPC-1, Capan-1, HPAF-2, MiaPaCa-2, and Panc-1) were analyzed by reverse transcription-PCR, real-time PCR, and Western blotting. An orthotopic nude mouse model of pancreatic cancer was applied for in vivo experiments.

RESULTS

Seventy-eight percent of human pancreatic cancer tissues showed an expression of Snail, and 50% of the patients displayed positive expression of Slug. Twist showed no or only weak expression. Snail expression was higher in undifferentiated cancer cell lines (MiaPaCa-2 and Panc-1) than in more differentiated cell lines (Capan-1, HPAF-2, AsPC-1). Expression of Slug was detected in all cell lines with different intensities. Twist was not expressed. After exposure to hypoxia, the Twist gene was activated in all five pancreatic cancer cell lines.

CONCLUSIONS

The transcription factors Snail and Slug are expressed in pancreatic cancer but not in normal tissue, suggesting a role in the progression of human pancreatic tumors. Twist, activated by hypoxia, may play an important role in the invasive behavior of pancreatic tumors.

Basics of TGF-beta and pancreatic cancer

Pancreatic cancer is the 4th leading cause of cancer-related death in the United States. The number of diagnoses per year equals the number of deaths per year, making it the deadliest of all malignancies. Modern advances and breakthroughs in molecular oncology have allowed researchers to gain a better understanding of the mechanisms responsible for the pathogenesis of this disease. The transforming growth factor-beta (TGF-beta) pathway is one of the signaling systems that has been identified as a major contributor. TGF-beta plays a paradoxical role as both a tumor suppressor and a tumor promoter in pancreatic cancer. The purpose of this review is to provide the practicing clinician a thorough review of this molecule and its associated signaling partners in the context of its duplicitous role and behavior in patients with pancreatic cancer.

Application of surface-enhanced laser desorption/ionization time-of-flight mass spectrometry for early detection of pancreatic cancer

Pancreatic cancer is a devastating and lethal disease. Early detection continues to be a serious, unsolved problem. However, proteomics is emerging as a powerful new tool for the diagnosis of pancreatic cancer. Surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) is a new technique that allows for rapid high-throughput screening of protein expression in clinical samples. The progress and challenges in applying SELDI-TOF MS to protein biomarker discovery in pancreatic cancer are reviewed in this paper.

Mechanisms of Disease: chronic inflammation and cancer in the pancreas—a potential role for pancreatic stellate cells?

Late diagnosis and ineffective therapeutic options mean that pancreatic ductal adenocarcinoma (PDA) is one of the most lethal forms of human cancer. The identification of genetic alterations facilitated the launch of the Pancreatic Intraepithelial Neoplasm nomenclature, a standardized classification system for pancreatic duct lesions, but the factors that contribute to the development of such lesions and their progression to high-grade neoplasia remain obscure. Age, smoking, obesity and diabetes confer increased risk of PDA, and the presence of chronic pancreatitis is a consistent risk factor for pancreatic cancer. It is hypothesized that chronic inflammation generates a microenvironment that contributes to malignant transformation in the pancreas, as is known to occur in other organs. Pancreatic stellate cells (PSCs) are the main mediator of fibrogenesis during chronic pancreatitis, but their contribution to the development of PDA has not been elucidated. Data now suggest that PSCs might assume a linking role in inflammation-associated carcinogenesis through their ability to communicate with inflammatory cells, acinar cells, and pancreatic cancer cells in a complicated network of interactions. In this Review, the role of PSCs in the process of inflammation-associated carcinogenesis is discussed and new potential treatment options evaluated.

Assessment of celecoxib pharmacodynamics in pancreatic cancer

Cyclooxygenase-2 (COX-2) inhibitors are being developed as chemopreventive and anticancer agents. This study aimed to determine the biological effect of the COX-2 inhibitor celecoxib in pancreatic cancer as an early step to the further development of the agent in this disease. Eight patients scheduled for resection of an infiltrating adenocarcinoma of the pancreas were randomized to receive celecoxib at a dose of 400 mg twice daily or placebo for 5 to 15 days before the surgery. In addition, carcinomas from nine additional patients were xenografted in nude mice, expanded, and treated with vehicle or celecoxib for 28 days. Celecoxib markedly decreased the intra-tumor levels of prostaglandin E2 in patient carcinomas and in the heterotransplanted xenografts. However, this effect did not result in inhibition of cell proliferation or microvessel density (as assessed by Ki67 and CD31 staining). In addition, a panel of markers, including bcl-2, COX-1, COX-2, and VEGF, did not change with treatment in a significant manner. Furthermore, there was no evidence of antitumor effects in the xenografted carcinomas. In summary, celecoxib efficiently inhibited the synthesis of prostaglandin E2 both in pancreatic cancer surgical specimens and in xenografted carcinomas but did not exert evident antitumor, antiproliferative, or antiangiogenic effect as a single agent. The direct pancreatic cancer xenograft model proved to be a valuable tool for drug evaluation and biological studies and showed similar results to those observed in resected pancreatic cancer specimens.

Molecular genetics of pancreatic intraepithelial neoplasia

BACKGROUND

Recent evidence suggests that noninvasive precursor lesions, classified as pancreatic intraepithelial neoplasia (PanIN), can progress to invasive pancreatic cancer. This review will discuss the major genetic alterations in PanIN lesions.

METHODS

A comprehensive review of the literature was performed in order to find studies on the molecular profile of human PanIN lesions. In addition, recent publications on genetically engineered mouse models of preinvasive neoplasia and pancreatic cancers were reviewed.

RESULTS

PanINs demonstrate abnormalities at the genomic (DNA), transcriptomic (RNA), and proteomic levels, and there is a progressive accumulation of molecular alterations that accompany the histological progression from low-grade PanIN-1A to high-grade PanIN-3 lesions. Molecular changes in PanINs can be classified as "early" (KRAS2 mutations, telomere shortening, p21(WAF1/CIP1) up-regulation, etc.), "intermediate" (cyclin D1 up-regulation, expression of proliferation antigens, etc.), or "late" (BRCA2 and TP53 mutations, DPC4/SMAD4/MADH4 inactivation, etc.). All the genetic changes observed in PanINs are also found in invasive ductal adenocarcinomas, where they usually occur at a higher frequency. Genetically engineered mice expressing mutant Kras in the pancreas, with or without additional genetic alterations, provide a unique in vivo platform to study the pancreatic cancer progression model.

CONCLUSIONS

Molecular studies have been instrumental in establishing that PanIN lesions are the noninvasive precursors for invasive ductal adenocarcinomas. The availability of molecular date provides the basis for designing rational early detection strategies and therapeutic intervention trials before pancreatic neoplasms invade, with the intention of alleviating the dismal prognosis associated with this disease.

Development of two novel benzoylphenylurea sulfur analogues and evidence that the microtubule-associated protein tau is predictive of their activity in pancreatic cancer

In this work, we evaluated two lead compounds, referred to as SG410 and SG430, obtained from a screen of sulfur benzoylphenylurea analogues, against in vitro and in vivo models of pancreas cancer. Both drugs showed a similar mechanism of action profile, with SG410 being more potent as an inhibitor of tubulin assembly. We determined the best in vivo administration schedule and tested SG410 and SG430 in nine cases of a novel platform of direct pancreas cancer xenografts. Both compounds had antiproliferative activity in vitro in the low nanomolar range, but only SG410 showed significant activity in vivo. Administration of SG410 resulted in significant tumor growth delay in five of nine groups tested. In a direct comparison in three of the cases, SG410 was at least as efficacious as docetaxel. We also sought markers that would be predictive of the efficacy of these agents, and we found such a marker in microtubule-associated protein tau (MAPT). This protein enhances the assembly and stability of microtubules. In both the cell lines and the direct human xenografts, MAPT mRNA and protein levels correlated well. There was also a statistically significant inverse correlation between MAPT expression and sensitivity to the tested agents. In summary, the novel sulfur benzoylphenylurea SG410 showed activity inversely related to MAPT expression in a preclinical model of pancreatic cancer comparable with that observed with docetaxel, another microtubule-targeting agent.

Precursor lesions of pancreatic cancer: molecular pathology and clinical implications

BACKGROUND

Pancreatic cancer is a lethal disease, with near uniform 5-year mortality rates. The key to improving survival of pancreatic cancer rests upon early detection of this neoplasm at a resectable, and hence potentially curable, stage.

METHODS

We review the current state of the literature vis-à-vis the three common precursor lesions of pancreatic adenocarcinoma: pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasm, and mucinous cystic neoplasm. We also discuss two clinical scenarios of emerging importance, namely asymptomatic pancreatic cysts ('pancreatic incidentalomas') and the significance of precursor lesions in familial pancreatic cancer kindreds.

RESULTS

Pancreatic intraepithelial neoplasias are the microscopic precursor lesions of pancreatic adenocarcinomas, while intraductal papillary mucinous neoplasms and mucinous cystic neoplasms are macroscopic, cystic precursor lesions. All three noninvasive entities demonstrate a multistep morphologic and genetic progression that culminates in frank invasive adenocarcinoma. Despite these commonalities, each precursor lesion harbors a unique repertoire of clinicopathologic and genetic characteristics that has an impact on natural history and prognosis of these lesions. Due to improvements in radiological techniques, asymptomatic pancreatic cysts are being increasingly discovered in the general population; intraductal papillary mucinous neoplasms and mucinous cystic neoplasms are the most common underlying histology in resected incidentalomas of the pancreas. Pancreatic asymptomatic cysts present an enormous challenge in terms of accurate diagnosis and management stratification. Incorporating molecular signatures of cystic precursor lesions into the diagnostic algorithm will likely become a standard of care for asymptomatic pancreatic cysts. High-risk individuals from familial pancreatic cancer kindreds are another group of individuals where knowledge of precursor lesions has had a therapeutic impact; sensitive imaging technologies have enabled the identification and subsequent resection of pancreatic cancer precursors in these high-risk individuals, preventing the progression to invasive cancer.

CONCLUSIONS

Precursor lesions of pancreatic adenocarcinomas represent a unique opportunity for diagnosis and intervention for a malignancy with near uniform lethality. Further studies on these precursors will enable the development of rational early detection and therapeutic strategies in order to ameliorate pancreatic cancer survival.

Targeting the apoptotic machinery in pancreatic cancers using small-molecule antagonists of the X-linked inhibitor of apoptosis protein

Resistance to apoptosis is a hallmark of many solid tumors, including pancreatic cancers, and may be the underlying basis for the suboptimal response to chemoradiation therapies. Overexpression of a family of inhibitor of apoptosis proteins (IAP) is commonly observed in pancreatic malignancies. We determined the therapeutic efficacy of recently described small-molecule antagonists of the X-linked IAP (XIAP) in preclinical models of pancreatic cancer. Primary pancreatic cancers were assessed for XIAP expression by immunohistochemistry, using a pancreatic cancer tissue microarray. XIAP small-molecule antagonists ("XAntag"; compounds 1396-11 and 1396-12) and the related compound 1396-28 were tested in vitro in a panel of human pancreatic cancer cell lines (Panc1, Capan1, and BxPC3) and in vivo in s.c. xenograft models for their ability to induce apoptosis and impede neoplastic growth. In addition, pancreatic cancer cell lines were treated with XAntags in conjunction with either tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or with radiation to determine potential synergy for such dual targeting of the apoptotic machinery. XIAP was overexpressed in 14 of 18 (77%) of primary pancreatic cancers. The XAntags1396-11 and 1396-12, but not the inactive isomer 1396-28, induced profound apoptosis in multiple pancreatic cancer cell lines tested in vitro, with a IC(50) in the range of 2 to 5 mumol/L. Mechanistic specificity of the XAntags for the baculoviral IAP repeat-2 domain of XIAP was shown by preferential activation of downstream "effector" caspases (caspase-3 and caspase-7) versus the upstream "initiator" caspase-9. S.c. BxPC3 xenograft growth in athymic mice was significantly inhibited by monotherapy with XAntags; treated xenografts showed marked apoptosis and increased cleavage of caspase-3. Notably, striking synergy was demonstrable when XAntags were combined with either TRAIL or radiation therapy, as measured by growth inhibition in vitro and reduced colony formation in soft agar of pancreatic cancer cell lines, at dosages where these therapeutic modalities had minimal to modest effects when used alone. Finally, XAntags in combination with the standard-of-care agent for advanced pancreatic cancer, gemcitabine, resulted in significantly greater inhibition of in vitro growth than gemcitabine alone. Our results confirm that pharmacologic inhibition of XIAP is a potent therapeutic modality in pancreatic cancers. These antagonists are independently capable of inducing pancreatic cancer cell death and also show synergy when combined with proapoptotic ligands (TRAIL), with radiation, and with a conventional antimetabolite, gemcitabine. These preclinical results suggest that targeting of the apoptotic machinery in pancreatic cancers with XAntags is a promising therapeutic option that warrants further evaluation.

MicroRNA expression alterations are linked to tumorigenesis and non-neoplastic processes in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is known for its very poor overall prognosis. Accurate early diagnosis and new therapeutic modalities are therefore urgently needed. We used 377 feature microRNA (miRNA) arrays to investigate miRNA expression in normal pancreas, chronic pancreatitis, and PDAC tissues as well as PDAC-derived cell lines. A pancreatic miRNome was established comparing the data from normal pancreas with a reference set of 33 human tissues. The expression of miR-216 and -217 and lack of expression of miR-133a were identified as characteristic of pancreas tissue. Unsupervised clustering showed that the three pancreatic tissues types can be classified according to their respective miRNA expression profiles. We identified 26 miRNAs most prominently misregulated in PDAC and a relative quantitative reverse transcriptase-polymerase chain reaction index using only miR-217 and -196a was found to discriminate normal pancreas, chronic pancreatitis and cancerous tissues, establishing a potential utility for miRNAs in diagnostic procedures. Lastly, comparing differentially expressed genes from PDAC with predicted miRNA target genes for the top 26 miRNAs, we identified potential novel links between aberrant miRNA expression and known target genes relevant to PDAC biology. Our data provides novel insights into the miRNA-driven pathophysiological mechanisms involved in PDAC development and offers new candidate targets to be exploited both for diagnostic and therapeutic strategies.

The role of positron emission tomography in the management of pancreatic cancer

The role of positron emission tomography (PET) and PET/computed tomography (CT) in the assessment of a patient presenting with cancer of the pancreas is discussed in the overall context of the management of this condition. The clinical limitations persist, with many patients presenting late with unresectable disease and poor prospects for novel drug therapies. PET and PET/CT are best at diagnosing and staging but are relatively inefficient in the detection of nodal disease. The detection of late disease manifestations such as metastatic spread is often of little clinical consequence. PET/CT may be considered as a first-line imaging investigation but evidence for this approach needs to accrue. Overall detection sensitivity at diagnosis varies between 90% and 95% and specificity from 82% to 100%, whereas for staging, sensitivity data vary from 61% to 100% and specificity data from 67% to 100%.

Surgical bypass versus endoscopic stenting for malignant gastroduodenal obstruction: a decision analysis

The treatment options for palliating malignant gastroduodenal obstruction include open gastrojejunostomy (OGJ), laparoscopic gastrojejunostomy (LGJ), and endoscopic stenting (ES). The aim of this study was to compare the clinical outcomes and costs among ES, OGJ, and LGJ in patients who present with gastroduodenal obstruction from advanced upper gastrointestinal tract cancer. We designed a model for patients with malignant gastroduodenal obstruction. We analyzed success rates, complication rates and costs of the three treatment modalities: ES, OGJ, and LGJ. Baseline outcomes and costs were based on published reports. Success was defined as no major procedure-related and long-term complications over a 1-month period. Failure of therapy was defined as recurrent symptoms or death due to a procedural complication. Sensitivity analyses and cost-effectiveness analyses for the various strategies were performed. ES resulted in the lowest mortality rate and the lowest cost of the three treatment options analyzed. Mortality in the OGJ group was 2.1 times that in the ES cohort and 1.8 times that in the LGJ cohort. Sensitivity analyses confirmed ES as the dominant strategy. In conclusion, ES is the preferred treatment for palliation of duodenal obstruction due to advanced upper gastrointestinal tract cancer.

Pancreatic cancer genetic epidemiology consortium

We have organized the Pancreatic Cancer Genetic Epidemiology (PACGENE) Consortium to identify susceptibility genes in familial pancreatic cancer (FPC). The Consortium comprises seven data collection centers, a statistical genetics core, and a pathology/archival genotyping core. We recruit kindreds containing two or more affected blood relatives ascertained through incident pancreatic adenocarcinoma cases, physician referrals, and/or through Internet recruitment. Accrual to a database containing core clinical, demographic, lifestyle, and family history information from questionnaires is ongoing, along with biospecimen collection. To date, 13,147 patients have been screened for family history, of whom 476 (50% male) probands and 1,912 of their adult (99% unaffected) relatives have been enrolled. Of these, 379 kindreds meet criteria for FPC, having at least two first-degree relatives with pancreatic cancer. Cumulative incidence curves using available age of diagnosis (onset) among and affected relatives were compared with those for incident pancreatic cancer cases reported to 13 U.S. Surveillance Epidemiology and End Results (SEER) sites from 1973 to 2000 (N = 72,700). The mean age +/- SD at diagnosis among 466 PACGENE probands and 670 affected relatives was 64.1 +/- 11.8 and was 65.4 +/- 11.6 for the subset of 369 FPC probands and 429 relatives. Both samples were significantly younger than the mean age at diagnosis in the SEER population (70.0 +/- 12.1 years; differences in curves versus SEER, P < 0.001). Age at diagnosis (excluding probands) in FPC kindreds does not decrease with increasing number of affected individuals. In our sample, younger age at diagnosis was observed whether we grouped probands by recruitment sites that predominantly recruited through high-risk referrals, or through screening all pancreatic cancer patients for family history. Linkage studies are ongoing. The PACGENE Consortium will be a valuable family-based resource that will greatly enhance genetic epidemiology research in pancreatic cancer.

Pancreatic cancer in the general population: Improvements in survival over the last decade

BACKGROUND

It is unknown whether the improved survival seen at high-volume centers has been translated to all patients with pancreatic cancer.

OBJECTIVE

To use the Surveillance, Epidemiology, and End Results (SEER) database to evaluate population-based trends in surgical resection and survival.

METHODS

All patients diagnosed with pancreatic cancer from 1988-1999 were identified. The survival and proportion of patients undergoing surgical resection were compared for each of three equal time periods.

RESULTS

There were 24,016 patients with pancreatic cancer. 19,533 had stage data available. 9% had localized, 29% had regional, and 62% had distant disease. Resection rates increased for patients with localized and regional disease over the three time periods. Survival increased for patients with regional and distant disease. For regional pancreatic cancer patients, 2-year survival increased from 9.5% to 13.5% (p < 0.0001) and from 21.5% to 28.9% following surgical resection (p = 0.002). For resected local/regional pancreatic cancer, the year of diagnosis was and independent predictor of improved survival (p = 0.0001).

CONCLUSIONS

SEER patients with regional and distant pancreatic cancer have improved survival over the past decade in both unadjusted and adjusted models. The improvement is most striking for patients with regional disease and reflects increased resection rates and improved resection techniques over time.

Diagnóstico y estadificación del carcinoma de páncreas (I)

Carcinoma of the pancreas is a neoplasm with a poor prognosis that is diagnosed in the advanced stages in most patients. Given that surgical resection is the only potentially curative treatment for this disease, it is of the utmost importance to appropriately select the group of patients with initial stage pancreatic tumors that have not extended and can therefore be resected. Several different imaging techniques can be used for this purpose: ultrasonography (US), computed tomography (CT), magnetic resonance (MR), as well as the recent additions of endoscopic ultrasonography (EUS) and positron emission tomography (PET). Other techniques, such as laparoscopy and laparoscopic ultrasonography, also play a role in the diagnosis and staging of these patients. Continual technological developments in each of the above-mentioned techniques have led to reiterated updates in the scientific literature throughout the last two decades. This review aims to evaluate each of these techniques and present diagnostic algorithms reflected in the literature in order to achieve the greatest diagnostic accuracy in determining the extent of the disease so that unnecessary surgery can be avoided in cases not susceptible to resection.

Quality of life after pancreaticoduodenectomy for ductal adenocarcinoma of the pancreatic head

BACKGROUND

This study examined quality of life (QoL) after classical partial pancreaticoduodenectomy (PPD) and pylorus-preserving pancreaticoduodenectomy (PPPD) in patients with adenocarcinoma of the pancreatic head, and also evaluated the influence of extended lymphadenectomy (ELA).

METHODS

Between January 1993 and March 2004, QoL was analysed in a prospective single-centre study that included 91 patients. Thirty-four patients underwent PPD and 57 had a PPPD. Seventy patients had an ELA and 21 underwent regional lymphadenectomy (RLA). QoL was assessed using the European Organization for Research and Treatment of Cancer QLQ-C30 questionnaire and a pancreatic cancer-specific module. Data were collected before operation and for 24 months after surgery.

RESULTS

The overall 5-year survival rate was 18 percent for all patients and 21 percent in those who had an R0 resection. QoL was impaired for 3-6 months after surgery and then recovered to preoperative levels. There was no significant difference in long-term survival after PPD versus PPPD and ELA versus RLA. Patients who had ELA reported clinically significant higher levels of diarrhoea and pain. PPPD showed a disadvantage in terms of pain.

CONCLUSION

The surgical techniques of resection and reconstruction did not affect QoL, but extended lymphadenectomy was associated with an impairment in QoL.

Depletion of Jab1 inhibits proliferation of pancreatic cancer cell lines

Jab1 overexpression is observed in many human cancers, but its physiological significance remains to be investigated. We reduced the level of Jab1 expression in pancreatic cancer cell lines, MIA PaCa-2 and PANC-1 by the RNA interference and found that Jab1-knockdown resulted in impaired cell proliferation and enhanced apoptosis regardless of the genotype of the tumor suppressor p53. This growth inhibition was rescued by the introduction of siRNA-resistant mouse Jab1 cDNA. Jab1-knocked-down cells expressed a higher level of c-myc, and additional depletion of c-myc rescued cells from Jab1-knockdown-mediated growth suppression. Thus, Jab1 overexpression contributes to pancreatic cancer cell proliferation and survival. Jab1 could be a novel target in cancer therapy.

Molecular biomarkers: their increasing role in the diagnosis, characterization, and therapy guidance in pancreatic cancer

The rapidly expanding knowledge of the pathogenesis of pancreatic cancer at the molecular level is providing new targets for disease characterization, early diagnosis, and drug discovery and development. Gene mutation analysis has provided insight on the pathogenesis and progression from preinvasive lesions to invasive cancer. Gene and protein expression profiling has advanced our understanding of pancreatic ductal adenocarcinoma identifying genes that are highly expressed in pancreatic cancers, providing more insight into the clinicopathologic features of pancreatic cancer, and revealing novel features related to the process of tissue invasion by these tumors. The increasing knowledge of the pathway activation profile in pancreatic cancer is yielding new targets but also new markers to select patients and guide and predict therapy efficacy. The discovery of genetic factors of which the presence predisposes pancreatic cancer to successful targeting, such as the association of BRCA2/Fanconi anemia genes defects and sensitivity to mitomycin C, will eventually lead to a more individualized treatment approach. In summary, several decades of intensive research have originated multiple factors or biomarkers that are likely to be helpful in the diagnosis, characterization, and therapy selection of pancreatic cancer patients. A deep understanding of the relative relevance of each biomarker will be key to efficiently diagnose this disease and direct our patients towards the drugs more likely to be of benefit based on their particular profile. The development of new preclinical models is of paramount importance to achieve these goals.

Pancreatic cancer initially presenting with a pseudocyst at the splenic flexure

Pancreatic cancer and pancreatitis associated pseudocyst are not uncommon disorders. However, occurrence of the cancer with an initial manifestation of pseudocyst has been rarely reported. Surgery was performed on a 44-year-old male patient for an abscess-like cavity situated at the mesenteric side of the colon and extending from the splenic flexure to the descending colon. The lesion was verified as a pseudocyst with fat necrosis due to leakage of pancreatic fluid. When further surgery was carried out 1 month later in order to manage the drainage site of the pancreatic fluid, cancer of the pancreas body was detected proximal to the drainage site. The cancer was a moderately differentiated ductal adenocarcinoma with wide peripancreatic infiltration. It is thought that the cancer-associated duct obstruction caused a local pancreatitis resulting in a large communicating pseudocyst, although the exact mechanism remains unresolved. The present case may be instructive in showing physicians that a pseudocyst may obscure the presence of pancreatic cancer.

New and emerging radiosensitizers and radioprotectors

The combination of chemotherapy and radiation has led to clinical breakthroughs in several disease sites, and current work continues to define optimum combinations of proven chemotherapy as well as more recently available, noncytotoxic agents. Administration of systemic therapies allows modulation of radiation response to improve tumor control (radiosensitization) or to prevent normal tissue toxicity (radioprotection). Substantial progress has been made in identifying the targets of standard chemotherapeutic radiation sensitizers and protectors as well as in the introduction of a new generation of molecularly targeted therapies in combination with radiation. We have reviewed the most recent, predominantly early phase clinical trials combining systemic agents with radiation. Although the proof of an improved schedule ultimately needs to come from well-run Phase III trials, the search among schedules could be shortened by the use of surrogate endpoints such as presence of active drug metabolites in the tumor. This has been accomplished only in a few cases and needs to become a more standard part of radiation sensitizer and protector trials.

Characterization of pancreatic lesions from MT-tgf alpha, Ela-myc and MT-tgf alpha/Ela-myc single and double transgenic mice

In order to identify good animal models for investigating therapeutic and preventive strategies for pancreatic cancer, we analyzed pancreatic lesions from several transgenic models and made a series of novel findings. Female MT-tgfα mice of the MT100 line developed pancreatic proliferation, acinar-ductal metaplasia, multilocular cystic neoplasms, ductal adenocarcinomas and prominent fibrosis, while the lesions in males were less severe. MT-tgfα-ES transgenic lines of both sexes developed slowly progressing lesions that were similar to what was seen in MT100 males. In both MT100 and MT-tgfα-ES lines, TGFα transgene was expressed mainly in proliferating ductal cells. Ela-myc transgenic mice with a mixed C57BL/6, SJL and FVB genetic background developed pancreatic tumors at 2–7 months of age, and half of the tumors were ductal adenocarcinomas, similar to what was reported originally by Sandgren et al [1]. However, in 20% of the mice, the tumors metastasized to the liver. MT100/Ela-myc and MT-tgfα-ES/Ela-myc double transgenic mice developed not only acinar carcinomas and mixed carcinomas as previously reported but also various ductal-originated lesions, including multilocular cystic neoplasms and ductal adenocarcinomas. The double transgenic tumors were more malignant and metastasized to the liver at a higher frequency (33%) compared with the Ela-myc tumors. Sequencing of the coding region of p16ink4, k-ras and Rb cDNA in small numbers of pancreatic tumors did not identify mutations. The short latency for tumor development, the variety of tumor morphology and the liver metastases seen in Ela-myc and MT-tgfα/Ela-myc mice make these animals good models for investigating new therapeutic and preventive strategies for pancreatic cancer.

Determination of sequential mutation accumulation in pancreas and bile duct brushing cytology

Neoplastic progression is characterized by clonal expansion of tumor cells associated with accumulation of mutational damage. The timing of mutation acquisition could be of value in distinguishing preneoplastic conditions from early and advanced cancer as well as characterizing tumor aggressiveness and treatment response. Using quantitative methods applied to microdissected cell clusters selected according to cytomorphologic features, we sought to demonstrate the feasibility and efficacy for determining the time and course of mutation accumulation in pancreatobiliary cytology specimens. In all, 40 pancreatic duct and 21 biliary brushing cytology specimens were retrieved from the cytology database. Xylene-resistant markings were placed on the slide underside and coverslips removed. Clusters of benign, atypical and malignant cells were manually microdissected and DNA extracted. Mutations (allelic imbalance) (loss of heterozygosity) were quantitatively determined for a broad panel of 15 markers (1p, 3p, 5q, 9p, 10q, 17p, 17q, 21q, 22q) as well as point mutation in K-ras-2 using PCR/capillary electrophoresis. Time course was based on earlier mutations having a higher proportion of mutant DNA for a particular marker. The descending frequency of detectable mutational involvement in pancreatic cytology was K-ras-2 point mutation (58%), 3p25-26 and 17q21 (35%), 5q23 (33%), 1p36 (28%), followed by the remaining molecular markers. The descending frequency of mutational content in bile duct cytology was 17p13, 1p36, 3p25-26, and 5q23 followed by remaining molecular markers. K-ras-2 point mutation was not seen in bile duct specimens. While there was overlap in the spectrum of mutational markers in pancreatic duct and biliary brushing cytology, the temporal profile was significantly different (P<0.001). Pancreatic and biliary neoplasia progression involves distinct subset of accumulated defined mutations. Determination of timing of the mutational damage in cytologic material could be incorporated in the work-up and help in making a more definitive diagnosis of malignancy in pancreatobiliary cytology specimens.

Proteomic classification of pancreatic adenocarcinoma tissue using protein chip technology

BACKGROUND & AIMS

Pancreatic adenocarcinoma is a most devastating cancer that presents late and is rapidly progressive. This study aimed to identify unique, tissue-specific protein biomarkers capable of differentiating pancreatic adenocarcinoma (PC) from adjacent uninvolved pancreatic tissue (AP), benign pancreatic disease (B), and nonmalignant tumor tissue (NM).

METHODS

Tissue samples representing PC (n = 31), AP (n = 44), and B (n = 19) tissue were analyzed on hydrophobic protein chip arrays by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. Training models were developed using logistic regression and validated using the 10-fold cross-validation approach.

RESULTS

The hydrophobic protein chip array revealed 13 protein peaks differentially expressed between PC and AP (receiver operating characteristic [ROC] area under the curve [AUC], 0.64-0.85), 8 between PC and B (ROC AUC, 0.67-0.78), and 12 between PC and NM tissue (ROC AUC, 0.63-0.81). Logistic regression and cross-validation identified overlapping panels of peaks to develop a training model that distinguished PC from AP (77.4% sensitivity, 84.1% specificity), B (83.9% sensitivity, 78.9% specificity), and NM tissue (58.1% sensitivity, 90.5% specificity). The final panels selected correctly classified 80.6% of PC and 88.6% of AP samples (ROC AUC, 0.92), 93.5% of PC and 89.5% of B samples (ROC AUC, 0.99), and 71.0% of PC and 92.1% of NM samples (ROC AUC, 0.91).

CONCLUSIONS

This study used surface-enhanced laser desorption/ionization time-of-flight mass spectrometry to discover a number of protein panels that can distinguish effectively between pancreatic adenocarcinoma, benign, and adjacent pancreatic tissue. Identification of these proteins will add to our understanding of the biology of pancreatic cancer. Furthermore, these protein panels may have important diagnostic implications.

The inherited genetics of pancreatic cancer and prospects for secondary screening

It is estimated that pancreatic cancer has a familial component in approximately 5-10% of cases. Some of these cases are part of a defined cancer syndrome with a known gene mutation but in the remaining the causative gene remains unknown. In recent years, a better understanding of the molecular events that occur in the progression model of pancreatic cancer has lead to the development of secondary screening programmes with the aim of identifying early precursor lesions or pre-invasive cancer at a stage amenable to curative resection. High-risk groups who have an inherited predisposition for pancreatic cancer form the ideal group to study in developing a robust screening programme. Multimodality screening using computed tomography and endoluminal ultrasound in combination with molecular analysis of pancreatic juice are proving promising as diagnostics tools or at least serving as predictors of risk over a defined period.

¿Cuáles son los principales errors que cometemos los cirujanos en el tratamiento del cáncer de páncreas?

The present review identifies two major conceptual errors. Therapeutic nihilism, which should be discounted in view of the results currently achieved by surgery, and noncentralization, since better results have been demonstrated, both in terms of morbidity and mortality and in survival, in high-volume centers than in low volume centers. The present review also identifies errors in management, the most important of which are: undervaluing the medical record, which is of great utility and continues to be the pillar on which the entire diagnostic process is based; the systematic use of preoperative biliary drainage, which used to be considered mandatory but should be used highly selectively in patients with severe jaundice or biliary tract infections, and viewing preoperative imaging tests as unreliable, when current radiological techniques, particularly helical computed tomography (CT), are highly reliable in establishing tumor resectability and consequently they should be used in all treatment planning. Moreover, because radiological tests are highly reliable, laparoscopic staging has lost diagnostic value; obtaining a preoperative histological diagnosis, which is not mandatory except when neoadjuvant therapy is planned or when tumors requiring nonsurgical treatment are suspected; undervaluing the use of surgical palliation, since this technique provides better long-term results than nonsurgical palliation, and consequently still plays a role in patients with good general health status and prolonged life expectancy; systematically performing gastrojejunostomy with bilio-enteric bypass, as this procedure should only be performed in tumors of the uncus or when there is imminent biliary or gastroduodenal obstruction; the use of supraradical surgical techniques such as regional, total or extensive pancreatectomy, since these techniques do not prolong survival after resection. Furthermore, the use of vascular resections would only be justified if resection with disease-free margins could be performed; undervaluing close postoperative monitoring within specialized units since this is the key to reducing morbidity and mortality rates in this type of surgery; and lastly when an intraoperative pancreatic incidentaloma is present, performing diagnostic maneuvers such as biopsy or pancreatic mobilization, since these procedures hamper subsequent radiological interpretation and possible surgical intervention.

The effect of a Frequently Asked Questions module on a pancreatic cancer Web site patient/family chat room

The Internet provides access to health information and a supportive community with similar illness concerns. Securing accurate information about treatment and prognosis is important to those with pancreatic cancer given its high mortality and short survival. The purpose of this descriptive-comparative study was to determine the effect of a Frequently Asked Questions (FAQ) module on postings in the chat room of a pancreatic cancer Web site. Six hundred postings were analyzed. Three themes were isolated: information seeking, giving, or both; support seeking, giving, or both; and reporting status or death. Information included treatments, nutrition, prognosis, end-of-life care, cost of care, symptoms, and support (social, emotional, spiritual, or physical). A greater proportion of postings sought information after the FAQ module was added, although questions about medical treatment decreased, whereas questions about prognosis and end-of-life care nearly doubled. There was no difference in the proportion of postings addressing support. Medical treatment was the most common treatment reported and pain was the most common symptom reported. This study supported the addition of a FAQ module to a pancreatic cancer Web site and revealed the need for information regarding pain management and care giving at the end of life.

Germ layers to organs: Using Xenopus to study “later” development

The amphibian embryo is a highly successful model system with great promise for organogenesis research. Since the late 1800s, amphibians have been employed to understand vertebrate development and since the 1950s, the African clawed frog Xenopus laevis has been the amphibian of choice. In the past two decades, Xenopus has led the way forward in, among other things, identifying transcription factors, gene regulatory networks and inter- and intracellular signaling pathways that control early development (from fertilization through gastrulation and neurulation). Perhaps the best measure of how successful Xenopus has been as a model for early mammalian development is the observation that much of the knowledge gleaned from Xenopus studies has subsequently directly translated to discoveries of similar mechanisms operating in mouse development. Despite this great success in early development, research on organogenesis in Xenopus has lagged behind the mouse. However, recent technical advances now make Xenopus amenable for studies on later development, including organogenesis. Here, we discuss why Xenopus is well suited for such research and, we believe, permits addressing questions that have been difficult to approach using other model systems. We also highlight how Xenopus researchers have already begun studying a number of major organs, pancreas, liver, kidney and heart, and suggest how Xenopus might contribute more to these areas in the near future.

In vivo disruption of TGF-beta signaling by Smad7 leads to premalignant ductal lesions in the pancreas

TGF-beta has been postulated to play an important role in the development of pancreatic cancers. More than 50% of human pancreatic cancers bear mutations of Sma- and Mad-related protein (Smad) 4, a critical protein required for TGF-beta signaling. To evaluate the in vivo function of TGF-beta in the development of pancreatic cancers, we generated a transgenic mouse model with pancreas-specific expression of Smad7, a specific inhibitor of TGF-beta signaling. Through the use of elastase I promoter, we directed the tissue specific expression of exogenous Smad7. Consistently, the exogenous Smad7 was detected only in the pancreas in the transgenic mice, and, furthermore, phosphorylation of Smad2 was blocked in the pancreatic tissues. At 6 months of age, most transgenic animals developed premalignant ductal lesions in the pancreas, with characteristics of pancreatic intraepithelial neoplasia (PanIN), a precursor to invasive pancreatic cancers. The premalignant lesions of the pancreas were accompanied by accelerated proliferation of the ductal epithelium and acinar cells, as well as increased fibrosis around the ductal lesions. This study not only demonstrated that in vivo inactivation of TGF-beta signaling is implicated in the development of early stage of pancreatic cancers, but also provided a promising animal model useful for the investigation and intervention of pancreatic cancers in humans.

Enhancement of antitumor immunity of dendritic cells pulsed with heat-treated tumor lysate in murine pancreatic cancer

Cancer vaccines using dendritic cells (DCs) have been shown to induce antitumor immunity and have recently been applied to non-immunogenic cancers, such as pancreatic cancer. In this study, we utilized DCs loaded with heat-treated tumor lysate (HTL-DC) as a vaccine in order to stimulate antitumor immunity in a murine pancreatic cancer model and compared them to DCs loaded with tumor lysate (TL-DC). The poorly immunogenic mouse ductal pancreatic cancer cell line PANC02 with syngeneic mouse strain C57BL/6 was used as a model. Inducible heat shock proteins (HSPs) were significantly increased in HTL (HSP70 and HSP90). Tumor size measurements indicated that HTL-DC induced stronger tumor suppression than unpulsed DC or TL-DC (43% reduction in tumor volume compared to control group). T cell proliferation assay and IFN-gamma ELISPOT assay showed that T cell activation increased in the following order: DC<TL-DC<HTL-DC. Furthermore, repeated HTL-DC vaccinations led to higher expansion of IFN-gamma-secreting T cells. Cytotoxicity assay revealed that HTL-DC were more efficient in priming PANC02-specific T cells. Our study identifies HTL as an effective source of tumor-associated antigens (TAAs) for pulsing DCs, and demonstrates that HTL-DC can generate a stronger and broader T cell response against fatal cancers, such as pancreatic cancer.

Biomarker discovery from pancreatic cancer secretome using a differential proteomic approach

Quantitative proteomics can be used as a screening tool for identification of differentially expressed proteins as potential biomarkers for cancers. Candidate biomarkers from such studies can subsequently be tested using other techniques for use in early detection of cancers. Here we demonstrate the use of stable isotope labeling with amino acids in cell culture (SILAC) method to compare the secreted proteins (secretome) from pancreatic cancer-derived cells with that from non-neoplastic pancreatic ductal cells. We identified 145 differentially secreted proteins (>1.5-fold change), several of which were previously reported as either up-regulated (e.g. cathepsin D, macrophage colony stimulation factor, and fibronectin receptor) or down-regulated (e.g. profilin 1 and IGFBP-7) proteins in pancreatic cancer, confirming the validity of our approach. In addition, we identified several proteins that have not been correlated previously with pancreatic cancer including perlecan (HSPG2), CD9 antigen, fibronectin receptor (integrin beta1), and a novel cytokine designated as predicted osteoblast protein (FAM3C). The differential expression of a subset of these novel proteins was validated by Western blot analysis. In addition, overexpression of several proteins not described previously to be elevated in human pancreatic cancer (CD9, perlecan, SDF4, apoE, and fibronectin receptor) was confirmed by immunohistochemical labeling using pancreatic cancer tissue microarrays suggesting that these could be further pursued as potential biomarkers. Lastly the protein expression data from SILAC were compared with mRNA expression data obtained using gene expression microarrays for the two cell lines (Panc1 and human pancreatic duct epithelial), and a correlation coefficient (r) of 0.28 was obtained, confirming previously reported poor associations between RNA and protein expression studies.

Genome-wide aberrations in pancreatic adenocarcinoma

Chromosomal instability, manifesting as copy number alterations (CNAs), is characteristic of pancreatic adenocarcinoma. We used bacterial artificial chromosome (BAC) array-based comparative genomic hybridization (aCGH) to examine the pancreatic adenocarcinoma genome for submicroscopic amplifications and deletions. Profiles of 33 samples (17 first-passage xenografts and 16 cell lines) identified numerous chromosomal regions with CNAs, including losses at 1p36.33 approximately p34.3, 1p13.3 approximately p13.2, 3p26, 3p25.2 approximately p22.3, 3p22.1 approximately p14.1, 4q28.3, 4q31, 4q35.1, 5q14.3, 6p, 6q, 8p23.3 approximately p12, 9p, 9q22.32 approximately q31.1, 13q33.2, 15q11.2, 16p13.3, 17p, 18q11.21 approximately q23 , 19p13.3 approximately p13.12, 19q13.2, 21p, 21q, and 22p, 22q and gains at 7p21.1 approximately p11.2, 7q31.32, 7q33, 8q11.1 approximately q24, 11p13, 14q22.2, 20p12.2, and 20q11.23 approximately q13.33. Novel regions containing CNAs were identified and refined by combining the increased resolution of our BAC CGH array with a statistical algorithm developed for assigning significance values to altered BACs across samples. A subset of array-based CNAs was validated using polymerase chain reaction-based techniques, immunohistochemistry and fluorescence in situ hybridization. BAC aCGH proved to be a powerful genome-wide strategy to identify molecular alterations in pancreatic cancer and to distinguish differences between cell line and xenograft aberration profiles. These findings should greatly facilitate further research in understanding the pathogenesis of this lethal disease, and could lead to the identification of novel therapeutic targets and biomarkers for early detection.

A new mouse model of pancreatic cancer: PTEN gets its Akt together

PTEN (phosphatase and tensin homolog deleted on chromosome 10) is a negative regulator of the oncogenic PI3-K/Akt signaling pathway. Loss-of-function mutations of PTEN are seen in several human solid cancers. A murine model of conditional Pten inactivation in the pancreas is described that leads to acquisition of a profound metaplastic ductal phenotype accompanied by loss of differentiated acinar units. Evidence is presented for a centroacinar cell origin of the metaplastic "neoductules." These mice also develop invasive pancreatic adenocarcinomas at a low frequency, and provide a unique in vivo platform for exploring the role of PI3-K/Akt signaling in pancreatic neoplasia.

Concordant loss of MTAP and p16/CDKN2A expression in pancreatic intraepithelial neoplasia: evidence of homozygous deletion in a noninvasive precursor lesion

The p16INK4A/CDKN2A (p16) gene on chromosome 9p21 is inactivated in >90% of invasive pancreatic cancers. In 40% of pancreatic cancers the p16 gene is inactivated by homozygous deletion, in 40% by an intragenic mutation coupled with loss of the second allele, and in 10-15% by hypermethylation of the p16 gene promoter. Immunohistochemical labeling for the p16 gene product parallels gene status, but does not provide information of the mechanism of p16 gene inactivation. The methylthioadenosine phosphorylase gene (MTAP) gene also resides on chromosome 9p21, approximately 100 kb telomeric to the p16 gene. The MTAP gene is frequently contained within p16 homozygous deletions, producing concordant loss of both p16 and MTAP gene expression. Concordant loss of both p16 and MTAP protein expression can therefore be used as a surrogate marker for p16 homozygous deletion. Here we immunolabeled a series of pancreatic intraepithelial neoplasia (PanIN) lesions of various histologic grades for the p16 and MTAP gene products using a high-throughput PanIN tissue microarray (TMA) format. We demonstrate concordant loss of p16 and MTAP protein expression in 6/73 (8%) PanINs, including five high-grade lesions and one low-grade lesion. Immunolabeling for both p16 and MTAP protein expression provides a tool to evaluate tissues with intact morphology for p16 gene homozygous deletions. The concordant loss of expression of both genes in PanIN lesions demonstrates that homozygous deletions of the p16 tumor suppressor gene can occur in noninvasive precursor lesions.

In vitro modeling of human pancreatic duct epithelial cell transformation defines gene expression changes induced by K-ras oncogenic activation in pancreatic carcinogenesis

Genetic analysis of pancreatic ductal adenocarcinomas and their putative precursor lesions, pancreatic intraepithelial neoplasias (PanIN), has shown a multistep molecular paradigm for duct cell carcinogenesis. Mutational activation or inactivation of the K-ras, p16(INK4A), Smad4, and p53 genes occur at progressive and high frequencies in these lesions. Oncogenic activation of the K-ras gene occurs in >90% of pancreatic ductal carcinoma and is found early in the PanIN-carcinoma sequence, but its functional roles remain poorly understood. We show here that the expression of K-ras(G12V) oncogene in a near diploid HPV16-E6E7 gene immortalized human pancreatic duct epithelial cell line originally derived from normal pancreas induced the formation of carcinoma in 50% of severe combined immunodeficient mice implanted with these cells. A tumor cell line established from one of these tumors formed ductal cancer when implanted orthotopically. These cells also showed increased activation of the mitogen-activated protein kinase, AKT, and nuclear factor-kappaB pathways. Microarray expression profiling studies identified 584 genes whose expression seemed specifically up-regulated by the K-ras oncogene expression. Forty-two of these genes have been reported previously as differentially overexpressed in pancreatic cancer cell lines or primary tumors. Real-time PCR confirmed the overexpression of a large number of these genes. Immunohistochemistry done on tissue microarrays constructed from PanIN and pancreatic cancer samples showed laminin beta3 overexpression starting in high-grade PanINs and occurring in >90% of pancreatic ductal carcinoma. The in vitro modeling of human pancreatic duct epithelial cell transformation may provide mechanistic insights on gene expression changes that occur during multistage pancreatic duct cell carcinogenesis.

Trp53R172H and KrasG12D cooperate to promote chromosomal instability and widely metastatic pancreatic ductal adenocarcinoma in mice

To define the genetic requirements for pancreatic ductal adenocarcinoma (PDA), we have targeted concomitant endogenous expression of Trp53(R172H) and Kras(G12D) to the mouse pancreas, revealing the cooperative development of invasive and widely metastatic carcinoma that recapitulates the human disease. The primary carcinomas and metastases demonstrate a high degree of genomic instability manifested by nonreciprocal translocations without obvious telomere erosion-hallmarks of human carcinomas not typically observed in mice. No mutations were discovered in other cardinal tumor suppressor gene pathways, which, together with previous results, suggests that there are distinct genetic pathways to PDA with different biological behaviors. These findings have clear implications for understanding mechanisms of disease pathogenesis, and for the development of detection and targeted treatment strategies.

Suppressing orthotopic pancreatic tumor growth with a fiber-modified adenovector expressing the TRAIL gene from the human telomerase reverse transcriptase promoter

An adenoviral vector with RGD-modified fibers and expressing the human tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) gene from the human telomerase reverse transcriptase (hTERT) promoter (designated Ad/TRAIL-F/RGD) was constructed, and its antitumor activity was evaluated in vitro and in vivo. An in vitro study showed that treatment with Ad/TRAIL-F/RGD elicited a high rate of apoptosis in human pancreatic and colon cancer cell lines that were either susceptible or resistant to conventional adenovectors. In vivo study showed that direct administration of Ad/TRAIL-F/RGD to an orthotopic implantation tumor model established in the pancreatic tails of nu/nu mice significantly suppressed tumor growth: tumors in the animals treated with Ad/TRAIL-F/RGD were approximately eight times smaller than those in animals treated with a control vector. We also evaluated hTERT promoter activity and the effect of Ad/TRAIL-F/RGD on mesenchymal stem cells. Our results showed that transgene expression from the hTERT promoter in human bone marrow mesenchymal stem cells was minimal. No adverse effect was observed in mesenchymal stem cells treated with Ad/TRAIL-F/RGD. Together, our results suggest that Ad/TRAIL-F/RGD could become a potent therapeutic agent for the management of pancreatic cancer.

Activation of phosphatidylinositol 3-kinase and extracellular signal-regulated kinase is required for glial cell line-derived neurotrophic factor-induced migration and invasion of pancreatic carcinoma cells

Pancreatic carcinoma cells exhibit a pronounced tendency to invade along and into intra- and extrapancreatic nerves, even at early stages of the disease. The neurotrophic factor glial cell line-derived neurotrophic factor (GDNF) has been shown to promote pancreatic cancer cell invasion. Here, we demonstrate that pancreatic carcinoma cell lines, such as PANC-1, expressed the RET and GDNF family receptor alpha receptor components for GDNF and that primary pancreatic tumor samples, derived from carcinomas with regional lymph node metastasis, exhibited marked expression of the mRNA encoding the RET51 isoform. Moreover, GDNF was an efficacious and potent chemoattractant for pancreatic carcinoma cells as examined in in vitro and in vivo model systems. Treatment of PANC-1 cells with GDNF resulted in activation of the monomeric GTPases N-Ras, Rac1, and RhoA, in activation of the mitogen-activated protein kinases extracellular signal-regulated kinase (ERK) and c-Jun NH(2)-terminal kinase (JNK) and in activation of the phosphatidylinositol 3-kinase/Akt pathway. Both inhibition of the Ras-Raf-MEK (mitogen-activated protein/ERK kinase)-ERK cascade by either stable expression of dominant-negative H-Ras(N17) or addition of the MEK1 inhibitor PD98059 as well as inhibition of the phosphatidylinositol 3-kinase pathway by LY294002 prevented GDNF-induced migration and invasion of PANC-1 cells. These results demonstrate that pancreatic tumor cell migration and possibly perineural invasion in response to GDNF is critically controlled by activation of the Ras-Raf-MEK-ERK and the phosphatidylinositol 3-kinase pathway.

Expression of inducible nitric oxide synthase and cyclooxygenase-2 in pancreatic adenocarcinoma: Correlation with microvessel density

AIM: Cyclooxygenases (COX) are key enzymes for conversion of arachidonic acid to prostaglandins. Nitric oxide synthase (NOS) is the enzyme responsible for formation of nitric oxide. Both have constitutive and inducible isoforms. The inducible isoforms (iNOS and COX-2) are of great interest as regulators of tumor angiogenesis, tumorigenesis and inflammatory processes. This study was to clarify their role in pancreatic adenocarcinomas.

METHODS: We investigated the immunohistochemical iNOS and COX-2 expression in 40 pancreatic ductal adenocarcinomas of different grade and stage. The results were compared with microvessel density and clinicopathological data.

RESULTS: Twenty-one (52.5%) of the cases showed iNOS expression, 15 (37.5%) of the cases were positive for COX-2. The immunoreaction was heterogeneously distributed within the tumors. Staining intensity was different between the tumors. No correlation between iNOS and COX-2 expression was seen. There was no relationship with microvessel density. However, iNOS positive tumors developed more often distant metastases and the more malignant tumors showed a higher COX-2 expression. There was no correlation with other clinicopathological data.

CONCLUSION: Approximately half of the cases expressed iNOS and COX-2. These two enzymes do not seem to be the key step in angiogenesis or carcinogenesis of pancreatic adenocarcinomas. Due to a low prevalence of COX-2 expression, chemoprevention of pancreatic carcinomas by COX-2 inhibitors can only achieve a limited success.

Mouse models of pancreatic cancer: the fur is finally flying!

Pancreatic cancer remains one of the most lethal of all human malignancies. Until recently, preclinical studies have been hampered by the absence of mouse models faithfully recapitulating critical elements of the human disease. However, recent months have witnessed a flurry of activity with respect to prospective mouse models. This progress now allows the evaluation of novel strategies for early detection, chemoprevention, and therapy and also provides new insights regarding the potential for differentiated and undifferentiated cell types to act as cells of origin for pancreatic ductal adenocarcinoma.