Molecular genetic basis of pancreatic adenocarcinoma

B-Lymphocytes in the Pathophysiology of Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma is highly infiltrated by B lymphocytes but the relevance of these immune cells in tumor development has been surprisingly overlooked until recently. Based on available evidence from other solid tumors, interaction between B lymphocytes and neoplastic cells is probably not uniformly stimulatory or inhibitory. Although presentation of tumor antigens to T cells and production of antitumor immunoglobulins might intuitively suggest a prominent tumor suppressive activity, specific subsets of B lymphocytes can secrete growth factors for neoplastic cells and immunosuppressive cytokines thus promoting escape from immunosurveillance and cancer progression. Because many of these mechanisms might also be implicated in the development of PDAC, and immune-modulation of B-cell activity is nowadays possible at different levels, determining the role of B-lymphocytes in this lethal cancer becomes of utmost importance to design novel therapeutic strategies. This review aims to discuss the emerging role of B cells in PDAC tumorigenesis, progression, and associated stromal reaction.

Targeting the Stroma in the Management of Pancreatic Cancer

Pancreatic cancer (PC) presents extremely aggressive tumours and is associated with poor survival. This is attributed to the unique features of the tumour microenvironment (TME), which is known to create a dense stromal formation and poorly immunogenic condition. In particular, the TME of PC, including the stromal cells and extracellular matrix, plays an essential role in the progression and chemoresistance of PC. Consequently, several promising agents that target key components of the stroma have already been developed and are currently in multiple stages of clinical trials. Therefore, the authors review the latest available evidence on novel stroma-targeting approaches, highlighting the potential impact of the stroma as a key component of the TME in PC.

Molecular Targeted Intervention for Pancreatic Cancer

Pancreatic cancer (PC) remains one of the worst cancers, with almost uniform lethality. PC risk is associated with westernized diet, tobacco, alcohol, obesity, chronic pancreatitis, and family history of pancreatic cancer. New targeted agents and the use of various therapeutic combinations have yet to provide adequate treatments for patients with advanced cancer. To design better preventive and/or treatment strategies against PC, knowledge of PC pathogenesis at the molecular level is vital. With the advent of genetically modified animals, significant advances have been made in understanding the molecular biology and pathogenesis of PC. Currently, several clinical trials and preclinical evaluations are underway to investigate novel agents that target signaling defects in PC. An important consideration in evaluating novel drugs is determining whether an agent can reach the target in concentrations effective to treat the disease. Recently, we have reported evidence for chemoprevention of PC. Here, we provide a comprehensive review of current updates on molecularly targeted interventions, as well as dietary, phytochemical, immunoregulatory, and microenvironment-based approaches for the development of novel therapeutic and preventive regimens. Special attention is given to prevention and treatment in preclinical genetically engineered mouse studies and human clinical studies.

Inherited variability in a master regulator polymorphism (rs4846126) associates with survival in 5-FU treated colorectal cancer patients

BACKGROUND

Treatment with 5-fluorouracil (5-FU) is known to improve survival in many cancers including colorectal cancer. Response to the treatment, overall survival and recurrence show inter-individual variation.

METHODS

In this study we employed a strategy to search eQTL variants influencing the expression of a large number of genes. We identified four single nucleotide polymorphisms, defined as master regulators of transcription, and genotyped them in a set of 218 colorectal cancer patients undergoing adjuvant 5-FU based therapy.

RESULTS

Our results showed that the minor allele variant of the rs4846126 polymorphism was associated with poor overall and progression-free survival. Patients that were homozygous for the variant allele showed an over two fold increased risk of death (HR 2.20 95%CI 1.05-4.60) and progression (HR 2.88, 95% 1.47-5.63). The integration of external information from publicly available gene expression repositories suggested that the rs4846126 polymorphism deserves further investigation. This variant potentially regulates the gene expression of 273 genes with some of them possibly associated to the patient's response to 5-FU treatment or colorectal cancer.

CONCLUSIONS

Present results show that mining of public data repositories in combination with own data can be a fruitful approach to identify markers that affect therapy outcome. In particular, a genetic screen of master regulators may help in order to search for the polymorphisms involved in treatment response in cancer patients.

Prognostic significance of XB130 expression in surgically resected pancreatic ductal adenocarcinoma

Background

XB130 is a newly discovered adaptor protein for intracellular signal transduction; it is involved in gene regulation, cell proliferation, cell survival, cell migration, and tumorigenesis. However, its expression and role in pancreatic ductal adenocarcinoma (PDAC) have not been investigated. The present study was designed to clarify the prognostic significance of XB130 expression in PDAC.

Methods

A total of 76 consecutive patients with surgically resected PDAC were retrospectively reviewed. XB130 expression was detected by immunohistochemical analysis on the paraffin-embedded tumour sections. Correlation between the expression of XB130 and clinicopathological parameters was analyzed.

Results

XB130 expression was significantly upregulated in PDAC(56.5%, 43/76) compared to normal pancreas (0%, 0/15; P < 0.05). Increased XB130 expression was correlated with lymph node metastasis (P = 0.017), distant metastasis (P = 0.0024), high tumour-node-metastasis (TNM) stage (P =0.001), and high tumour grade (P = 0.013). The survival of 43 patients with high XB130 expression was significantly worse than that of the 33 patients with low XB130 expression (P = 0.001). Univariate analysis showed that high XB130 expression (P = 0.0045), tumour size (P = 0.024), distant metastasis (P = 0.003), TNM stage (P = 0.002) and lymphatic metastasis (P = 0.016) were independent prognostic factors of postoperative survival. Multivariate analysis using the Cox proportional hazards model showed that high XB130 expression and distant metastasis (P = 0.0239) were significant independent risk factors.

Conclusions

XB130 was overexpressed in the PDAC. XB130 is a promising pathological marker for the prediction of outcome in patients with PDAC.

A chronocoulometric LNA sensor for amplified detection of K-ras mutation based on site-specific DNA cleavage of restriction endonuclease

An amplified chronocoulometric Locked nucleic acid (LNA) sensor (CLS) for selective electrochemical detection of K-ras mutation was developed based on site-specific DNA cleavage of restriction endonuclease EcoRI. Thiolated-hairpin LNA probe with palindrome structure of stem was immobilized on the gold nanoparticles modified gold electrode (NG/AuE). It can be cleaved by EcoRI in the absence of K-ras mutation-type DNA (complementary with the loop part of hairpin probe), but cannot be cleaved in the presence of mutation-type DNA. The difference before and after enzymatic cleavage was then monitored by chronocoulometric biosensor. Electrochemical signals are generated by chronocoulometric interrogation of Hexaammineruthenium (III) chloride (RuHex) that quantitatively binds to surface-confined hairpin LNA probe via electrostatic interactions. The results suggested this CLS had a good specificity to distinguish the K-ras mutation-type, wild-type and non-complementary sequence. There was a good linear relationship between the charge and the logarithmic function of K-ras mutation-type DNA concentration. The detection limit had been estimated as 0.5 fM. It is possible to qualitatively and quantitatively detect K-ras point mutation in pancreatic cancer.

RAD51 as a potential biomarker and therapeutic target for pancreatic cancer

Chemotherapy is a very important therapeutic strategy for cancer treatment. The failure of conventional and molecularly targeted chemotherapeutic regimes for the treatment of pancreatic cancer highlights a desperate need for novel therapeutic interventions. Chemotherapy often fails to eliminate all tumor cells because of intrinsic or acquired drug resistance, which is the most common cause of tumor recurrence. Overexpression of RAD51 protein, a key player in DNA repair/recombination has been observed in many cancer cells and its hyperexpression is implicated in drug resistance. Recent studies suggest that RAD51 overexpression contributes to the development, progression and drug resistance of pancreatic cancer cells. Here we provide a brief overview of the available pieces of evidence in support of the role of RAD51 in pancreatic tumorigenesis and drug resistance, and hypothesize that RAD51 could serve as a potential biomarker for diagnosis of pancreatic cancer. We discuss the possible involvement of RAD51 in the drug resistance associated with epithelial to mesenchymal transition and with cancer stem cells. Finally, we speculate that targeting RAD51 in pancreatic cancer cells may be a novel approach for the treatment of pancreatic cancer.

FAM190A rearrangements provide a multitude of individualized tumor signatures and neo-antigens in cancer

We found FAM190A transcripts to have internal rearrangements in 40% (19/48) of unselected human cancers. Most of these tumors (84%) had in-frame structures, 94% of which involved deletion of exon 9. The FAM190A gene is located at 4q22.1 in a region of common fragility, FRA4F. Although normally stable in somatic cells, common fragile sites can be hotspots of rearrangement in cancer. The genomic deletion patterns observed at some sites, including FRA4F at 4q22.1, are proposed to be the result of selection for disrupted tumor-suppressor genes. Our evidence, however, indicated additional patterns for FAM190A. We found genomic deletions accounted for some FAM190A in-frame structures, and cases pre-selected for FAM190A genomic deletions had a yet higher prevalence of FAM190A rearrangements. Our evidence of widespread in-frame heterozygous and homozygous rearrangements affecting this gene in tumors of multiple types leads speculation on structural grounds that the mutant forms may retain, provide new, or possibly convey dominant-negative functions. Although a functionally uncharacterized gene, it is evolutionary conserved across vertebrates. In addition to its potential oncogenic role, the in-frame deletions predict the formation of cancer-specific FAM190A peptide sequences (neo-antigens) with potential diagnostic and therapeutic usefulness.

Influence of cell cycle checkpoints and p53 function on the toxicity of temozolomide in human pancreatic cancer cells

BACKGROUND

Though an increased efficacy of carmustine and temozolomide (TMZ) has been demonstrated by inactivation of O(6)-methylguanine-DNA methyltransferase (MGMT) with O(6)-benzyl-guanine (BG) in human pancreatic tumors refractive to alkylating agents, the regulatory mechanisms have not been explored.

METHODS

The effects of TMZ and BG on apoptosis, cell growth, the mitotic index, cell cycle distribution, and protein expression were studied by TUNEL, cell counting, flow cytometry, and Western blot analysis, respectively.

RESULTS

The wt-p53 human pancreatic tumor cell line Capan-2 and p53-efficient mouse embryonic fibroblasts (MEFs) were more responsive to treatment with TMZ + BG than mutant p53 Capan-1 and p53-null MEFs. S phase delay with a subsequent G2/M arrest was observed in Capans in response to BG + TMZ. The G1-to-S transition delay in Capan-2 was associated with p53-dependent apoptosis and was distinctly different from the presumed mismatch repair (MMR) killing operative during the G2/M arrest. The effect of p53 on BG + TMZ toxicity was supported by a marked change in apoptosis when p53 function was restored/inactivated. There was an early induction of MMR proteins in p53-efficient lines.

CONCLUSION

p53 provokes a classic proapoptotic response by delaying G1-to-S progression, but it may also facilitate cell killing by enhancing MMR-related cell cycle arrest and cell death.

Pdx-1-driven overexpression of aurora a kinase induces mild ductal dysplasia of pancreatic ducts near islets in transgenic mice

OBJECTIVES

To further explore the oncogenic activity of Aurora A kinase while attempting to develop a useful mouse model for pancreatic cancer, Aurora A kinase was targeted to pancreatic duodenal homeobox gene-1 (Pdx-1)-positive cells.

METHODS

Aurora A kinase overexpression was targeted to mouse pancreas tissues using the Pdx-1 promoter in a transgenic model. The pancreas tissues of 7- to 11-month-old transgenic animals were evaluated for metastatic adenocarcinomas, preinvasive ductal neoplasia, or other histological anomalies.

RESULTS

Examination of pancreatic tissue from Pdx-1-Aurora A transgenic mice revealed abnormalities, such as mild islet cell hyperplasia, lymphocytic infiltration, and general dysplasia between ductal/islet cell interfaces. However, most tissues from these transgenic mice were normal.

CONCLUSIONS

The overexpression of Aurora A can potentially initiate the development of mild abnormalities in pancreatic tissue; however, neither preinvasive ductal neoplasia nor fully metastatic adenocarcinomas were observed. Combining the Pdx-1-Aurora A transgenic model with other genetic alterations may provide additional insight.

Lessons from Tarceva in pancreatic cancer: where are we now, and how should future trials be designed in pancreatic cancer?

PURPOSE OF REVIEW

The recent advances in the use of targeted therapy in pancreatic cancer are based on the knowledge of genetic alterations that occur during pancreatic carcinogenesis. We describe the repository of frequent alterations targeting tumour suppressor genes and oncogenes. We focus our attention on the epidermal growth factor receptor signalling pathway, which can be activated through different alterations and seems to play a central role in the cell transformation. Multiple targeted drugs have been developed against different partners of this network trying to improve the treatment of pancreatic cancer patients.

RECENT FINDINGS

Tarceva has obtained approval in the USA and Europe for metastatic pancreatic cancer with a modest increase of median survival and a 6% increase in 1-year survival rates, suggesting that only a small fraction of patients truly benefit from it. The comparison with lung and colon cancer suggests that Kras mutations could be a predictive marker of resistance. Other promising drugs targeting different partners of the epidermal growth factor receptor signalling pathway could play a synergistic role with Tarceva as inhibitors of mTOR, mitogen-activated protein kinase kinase 1, and nuclear factor-kappaB or can directly turn down Ras.

SUMMARY

The biology of the epidermal growth factor receptor, mitogen-activated protein kinase, PI3K/mTOR network suggests that a combination of drugs targeting simultaneously different partners should improve survival.

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.

Potential role of Jun activation domain-binding protein 1 as a negative regulator of p27kip1 in pancreatic adenocarcinoma

Reduced expression of p27 has been associated with poor prognosis in most human cancers, including pancreatic adenocarcinoma. Jun activation domain-binding protein 1 (JAB1), an activator protein (AP-1) coactivator, previously implicated in p27 degradation, is overexpressed in various tumors and correlates with low p27 expression. We examined JAB1 and p27 in normal and neoplastic pancreatic tissues. Increased JAB1 expression was seen in pancreatic carcinoma samples but not in paired normal pancreatic tissues. Immunohistochemical analysis using tissue microarrays showed that JAB1 was overexpressed in all 32 (100%) pancreatic adenocarcinoma samples tested, predominantly nuclear in 23 (72%) samples and predominantly cytoplasmic in 9 (28%) tumors. When 10% was used as a cutoff for p27 positivity, p27 was expressed in 11 (34%) of tumors; however, p27 expression was localized in the nuclei of tumor cells in only 4 (13%) of the samples. Overexpression of the JAB1 in the pancreatic carcinoma cell lines Panc-1, Mia PaCa-2, and Panc-28 resulted in decreased p27 expression. Conversely, down-regulation of JAB1 by short interfering RNA substantially increased p27 expression and inhibited progression from G(1) to S phase of the cell cycle. Interestingly, JAB1-mediated p27 degradation was not impaired when S-phase kinase-interacting protein 2 (Skp2), an F-box protein required for the ubiquitination and consequent degradation of p27, was silenced. Thus, JAB1 may have an Skp2-independent p27 degradation mechanism in pancreatic cancer cells. These findings suggest that JAB1 overexpression is involved in the pathogenesis of pancreatic cancer through JAB1-mediated p27 degradation and that control of JAB1 expression is a novel therapeutic target in patients with pancreatic adenocarcinomas.

Identifying allelic loss and homozygous deletions in pancreatic cancer without matched normals using high-density single-nucleotide polymorphism arrays

Recent advances in oligonucleotide arrays and whole-genome complexity reduction data analysis now permit the evaluation of tens of thousands of single-nucleotide polymorphisms simultaneously for a genome-wide analysis of allelic status. Using these arrays, we created high-resolution allelotype maps of 26 pancreatic cancer cell lines. The areas of heterozygosity implicitly served to reveal regions of allelic loss. The array-derived maps were verified by a panel of 317 microsatellite markers used in a subset of seven samples, showing a 97.1% concordance between heterozygous calls. Three matched tumor/normal pairs were used to estimate the false-negative and potential false-positive rates for identifying loss of heterozygosity: 3.6 regions (average minimal region of loss, 720,228 bp) and 2.3 regions (average heterozygous gap distance, 4,434,994 bp) per genome, respectively. Genomic fractional allelic loss calculations showed that cumulative levels of allelic loss ranged widely from 17.1% to 79.9% of the haploid genome length. Regional increases in "NoCall" frequencies combined with copy number loss estimates were used to identify 41 homozygous deletions (19 first reports), implicating an additional 13 regions disrupted in pancreatic cancer. Unexpectedly, 23 of these occurred in just two lines (BxPc3 and MiaPaCa2), suggesting the existence of at least two subclasses of chromosomal instability (CIN) patterns, distinguished here by allelic loss and copy number changes (original CIN) and those also highly enriched in the genomic "holes" of homozygous deletions (holey CIN). This study provides previously unavailable high-resolution allelotype and deletion breakpoint maps in widely shared pancreatic cancer cell lines and effectively eliminates the need for matched normal tissue to define informative loci.

External imaging of CCND1, MYC, and KRAS oncogene mRNAs with tumor-targeted radionuclide-PNA-peptide chimeras

In 2005, breast cancer will kill approximately 40,410 women in the U.S., and pancreatic cancer will kill approximately 31,800 men and women in the U.S. Clinical examination and mammography, the currently accepted breast cancer screening methods, miss almost half of breast cancers in women younger than 40 years, approximately one-quarter of cancers in women aged 40-49 years, and one-fifth of cancers in women over 50 years old. Pancreatic cancer progresses rapidly, with only 1% of patients surviving more than 5 years after diagnosis. However, if the disease is diagnosed when it is localized, the 5-year survival is approximately 20%. It would be beneficial to detect breast cancer and pancreatic cancer at the earliest possible stage, when multimodal therapy with surgery, radiotherapy, and chemotherapy have the greatest chance of prolonging survival. Human estrogen receptor-positive breast cancer cells typically display elevated levels of Myc protein due to overexpression of MYC mRNA, elevated cyclin D1 protein due to overexpression of CCND1 mRNA, and elevated insulin-like growth factor 1 receptor (IGF1R) due to overexpression of IGF1R mRNA. We hypothesized that scintigraphic detection of MYC or CCND1 peptide nucleic acid (PNA) probes with an IGF1 peptide loop on the C-terminus, and a Tc-99m-chelator peptide on the N-terminus, could measure levels of MYC or CCND1 mRNA noninvasively in human IGF1R-overexpressing MCF7 breast cancer xenografts in immunocompromised mice. Similarly, human pancreatic cancer cells typically display elevated levels of KRAS mRNA and elevated IGF1R. Hence, we also hypothesized that a KRAS Tc-99m-chelator PNA-peptide probe could detect overexpression of KRAS mRNA in pancreatic cancer xenografts by scintigraphic imaging, or by positron emission tomography (PET) with a KRAS Cu-64-chelator PNA-peptide. Human MCF7 breast cancer xenografts in immunocompromised mice were imaged scintigraphically 4-24 h after tail-vein administration of MYC or CCND1 Tc-99m-chelator PNA-peptides, but not after administration of mismatch controls. Similarly, human Panc-1 pancreatic cancer cells xenografts were imaged scintigraphically 4 and 24 h after tail-vein administration of a KRAS Tc-99m-chelator PNA-peptide, and AsPC1 xenografts were imaged by PET 4 and 24 h after tail-vein adminstration of a KRAS Cu-64-chelator PNA-peptide. The radioprobes distributed normally to the kidneys, livers, tumors, and other tissues. External molecular imaging of oncogene mRNAs in solid tumors with radiolabel-PNA-peptide chimeras might in the future provide additional genetic characterization of pre-invasive and invasive breast cancers.

Ductal origin of pancreatic adenocarcinomas induced by conditional activation of a human Ha-ras oncogene in rat pancreas

Pancreatic ductal adenocarcinoma is one of the most debilitating malignancies in humans. Currently, radiation and chemotherapy are ineffective, with median survival times after treatment of <12 months. Animal models that reflect the human condition and can be used to explore screening and therapeutic approaches are clearly desirable. One feature of human pancreatic adenocarcinoma is an exceedingly high frequency of K-ras mutation. The present study was conducted to determine if targeted activation of a human oncogenic-ras transgene in rat pancreas would induce carcinomas correspondent to human pancreatic ductal adenocarcinomas. We established transgenic (Hras250) rats in which expression of a human Ha-rasG12V oncogene is regulated by the Cre/lox system. Targeted pancreatic activation of the transgene was accomplished by injection of Cre-carrying adenovirus into the pancreatic ducts and acini through the common bile duct. Adenoviral infection of injected animals was exclusive to the pancreas; infected cells could be identified in duct, intercalated duct, centroacinar and, less frequently, acinar cells, but not in endocrine islet cells. Four weeks after injection, proliferative lesions in the duct epithelium, intercalated ducts and centroacinar cells, but not acinar cells, were widespread. Tumorigenesis in other tissues was not observed. Most lesions, including atypical duct proliferative lesions, PanIN-like lesions and carcinomas, were positive for cytokeratins 19 and 7, cyclooxygenase 2 and MMP-7 but negative for amylase and chymotrypsin. Many adenocarcinoma lesions were positive for EGF and EGFR. Duct epithelial and atypical duct proliferative lesions and carcinoma lesions were all positive for transduced Ha-rasG12V oncogene expression. The cytogenesis of pancreatic ductal type carcinoma was depicted. This model exhibits important similarities to the human disease and promises to advance our understanding of the behavior of pancreas adenocarcinomas and expedite screening and therapy.

Activation of Ras/Raf protects cells from melanoma differentiation-associated gene-5-induced apoptosis

Melanoma differentiation-associated gene-5 (mda-5) was the first molecule identified in nature whose encoded protein embodied the unique structural combination of an N-terminal caspase recruitment domain and a C-terminal DExD/H RNA helicase domain. As suggested by its structure, cumulative evidences documented that ectopic expression of mda-5 leads to growth inhibition and/or apoptosis in various cell lines. However, the signaling pathways involved in mda-5-mediated killing have not been elucidated. In this study, we utilized either genetically modified cloned rat embryo fibroblast cells overexpressing different functionally and structurally distinct oncogenes or human pancreatic and colorectal carcinoma cells containing mutant active ras to resolve the role of the Ras/Raf signaling pathway in mda-5-mediated growth inhibition/apoptosis induction. Rodent and human tumor cells containing constitutively activated Raf/Raf/MEK/ERK pathways were resistant to mda-5-induced killing and this protection was antagonized by intervening in this signal transduction cascade either by directly inhibiting ras activity using an antisense strategy or by targeting ras-downstream factors, such as MEK1/2, with the pharmacological inhibitor PD98059. The present findings provide a further example of potential cross-talk between growth-inhibitory and growth-promoting pathways in which the ultimate balance of these factors defines cellular homeostasis, leading to survival or induction of programmed cell death.

A pooled analysis of second primary pancreatic cancer

Studies of pancreatic cancer in the setting of second primary malignant neoplasms can provide etiologic clues. An international multicenter study was carried out using data from 13 cancer registries with a registration period up to year 2000. Cancer patients were followed up from the initial cancer diagnosis, and the occurrence of second primary malignant neoplasms was compared with expected values derived from local rates, adjusting for age, sex, and period of diagnosis. Results from individual registries were pooled by use of a fixed-effects model. People were at higher risk of developing pancreatic cancer within 10 years of a diagnosis of cancers of the pharynx, stomach, gallbladder, larynx, lung, cervix, corpus uteri, bladder, and eye and 10 years or later following a diagnosis of cancers of the stomach, colon, gallbladder, breast, cervix, placenta, corpus uteri, ovary, testis, bladder, kidney, and eye, as well as Hodgkin's and non-Hodgkin's lymphomas. Pancreatic cancer was connected with smoking-related cancers, confirming the etiologic role of tobacco. The associations with uterine and ovarian cancers suggest that reproductive factors might be implicated in pancreatic carcinogenesis. The elevated pancreatic cancer risk in young patients observed among several types of cancer implies a role of genetic factors. Radiotherapy is also suggested as a risk factor.

Methionine-stress: A pleiotropic approach in enhancing the efficacy of chemotherapy

Malignant cells fail to utilize homocysteine (HCYS) in place of methionine (MET) and they are dependent on exogenous MET for growth. In animals, reduction of plasma MET to <5 microM can be induced by combined dietary restriction of MET and administration of L-methionine-alpha-deamino-gamma-lyase (methioninase). This treatment, termed as MET-stress, inhibits the growth of brain tumor xenografts in athymic mice and enhances the efficacy of DNA alkylating chemotherapeutic agents. The response of tumors to MET-stress depends on their mutational status, however, it always involves inhibition of CDK1 and in most cases the upregulation of p21, p27, GADDs and 14-3-3sigma in response to upregulation of TGF-beta, IRF-1, TNF-alpha, Rb and/or MDA-7 and the downregulation of PI3K, RAS and NF-kappaB. Although inhibition of the cell cycle and mitosis is not necessarily dependent on the tumor's p53 status, the expression of p21, GADD45 and apoptosis related genes (BAX, BCL-2) are regulated by wt-p53, in addition to their regulation by TGF-beta or MDA-7 in mutated p53 tumors. Mutational variability determines the mode of death (mitotic catastrophe versus apoptosis) in tumor cells subjected to MET-stress. The increase of the efficacy of alkylating agents is related to marked inhibition of O6-methylguanine-DNA methyltransferase (MGMT) expression, the induction of cell cycle check points and the inhibition of pro-survival pathways by MET-stress.

Modulation of cell cycle and gene expression in pancreatic tumor cell lines by methionine deprivation (methionine stress): implications to the therapy of pancreatic adenocarcinoma

The effect of methionine deprivation (methionine stress) on the proliferation, survival, resistance to chemotherapy, and regulation of gene and protein expression in pancreatic tumor lines is examined. Methionine stress prevents successful mitosis and promotes cell cycle arrest and accumulation of cells with multiple micronuclei with decondensed chromatin. Inhibition of mitosis correlates with CDK1 down-regulation and/or inhibition of its function by Tyr(15) phosphorylation or Thr(161) dephosphorylation. Inhibition of cell cycle progression correlates with loss of hyperphosphorylated Rb and up-regulation of p21 via p53 and/or transforming growth factor-beta (TGF-beta) activation depending on p53 status. Although methionine stress-induced toxicity is not solely dependent on p53, the gain in p21 and loss in CDK1 transcription are more enhanced in wild-type p53 tumors. Up-regulation of SMAD7, a TGF-beta signaling inhibitor, suggests that SMAD7 does not restrict the TGF-beta-mediated induction of p21, although it may prevent up-regulation of p27. cDNA oligoarray analysis indicated a pleiotropic response to methionine stress. Cell cycle and mitotic arrest is in agreement with up-regulation of NF2, ETS2, CLU, GADD45alpha, GADD45beta, and GADD45gamma and down-regulation of AURKB, TOP2A, CCNA, CCNB, PRC1, BUB1, NuSAP, IFI16, and BRCA1. Down-regulation of AREG, AGTR1, M-CSF, and EGF, IGF, and VEGF receptors and up-regulation of GNA11 and IGFBP4 signify loss of growth factor support. PIN1, FEN1, and cABL up-regulation and LMNB1, AREG, RhoB, CCNG, TYMS, F3, and MGMT down-regulation suggest that methionine stress sensitizes the tumor cells to DNA-alkylating drugs, 5-fluorouracil, and radiation. Increased sensitivity of pancreatic tumor cell lines to temozolomide is shown under methionine stress conditions and is attributed in part to diminished O(6)-methylguanine-DNA methyltransferase and possibly to inhibition of the cell cycle progression.

Insulin receptor substrate is a mediator of phosphoinositide 3-kinase activation in quiescent pancreatic cancer cells

Phosphoinositide 3-kinase (PI3K) is activated in pancreatic cancer cells and plays a central role in their proliferation, survival, and drug resistance. Although the mechanism is unclear, PI3K activation in these cells could be due to physical interaction between its regulatory subunit (p85) and specific tyrosine kinases or their mediators. Consistent with this possibility, PI3K was precipitated with anti-phosphotyrosine antibodies and Akt phosphorylation was blocked by the tyrosine kinase inhibitors SU6656 and PD158780 in quiescent pancreatic cancer cells. Pull-down assays with a fusion protein (GST-p85NC-SH2), and coimmunoprecipitation studies, indicated that the insulin receptor substrate (IRS), and not the epidermal growth factor and insulin-like growth factor receptors or the Src tyrosine kinase, was physically associated with PI3K in these cells. Our data also indicated that SU6656 and PD158780 inhibited Akt activation in pancreatic cancer cells by interfering with the ability of IRS-1 to recruit PI3K. Furthermore, IRS-1 was phosphorylated on a p85-binding site (Y(612)), and IRS-specific small interfering RNA potently inhibited activation of PI3K and Akt in transfected cells. Taken together, these observations indicate that IRS is a mediator of PI3K activation in quiescent pancreatic cancer cells.

Targeted virus replication plus immunotherapy eradicates primary and distant pancreatic tumors in nude mice

Pancreatic cancer is an aggressive neoplasm with no current viable, effective treatment options. In the majority of cases, at first diagnosis, pancreatic cancer has already become metastatic so that conventional treatment regimens provide minimal, if any, clinical benefit in prolonging life or ameliorating the negative prognosis of this disease. These harsh realities underscore the need for developing improved treatment paradigms for this cancer, with gene therapy and immunotherapy currently being evaluated as potential therapeutic options. We currently describe an adenovirus-based therapy for successfully managing pancreatic cancer, the cancer terminator virus (CTV), which is founded on targeted induction of viral replication from a cancer-specific progression elevated gene-3 (PEG-3) promoter (PEG-Prom) and immune modulation by IFN-gamma. The PEG-Prom functions selectively in cancer cells of diverse lineages compared with their normal cellular counterparts. In the CTV, the PEG-Prom drives expression of the adenoviral early region 1A (E1A) gene, necessary for virus replication, with IFN-gamma simultaneously being expressed from the E3 region. Infection of normal cells and pancreatic cancer cells with the CTV confirmed cancer cell-selective adenoviral replication, robust IFN-gamma production coupled with virus replication, growth inhibition, and apoptosis induction. Infection of established pancreatic tumors in nude mice with the CTV promoted viral replication, IFN-gamma production, and activation of antitumor immunity resulting in complete eradication of both primary and distant tumors, curing animals of disease. The CTV provides a novel reagent for treating pancreatic and other human cancers with potential for eliminating both primary tumors and metastatic disease.

Unique aspects of mda-7/IL-24 antitumor bystander activity: establishing a role for secretion of MDA-7/IL-24 protein by normal cells

Melanoma differentiation associated gene-7 (mda-7) was cloned using subtraction hybridization from terminally differentiated human melanoma cells. Based on structural and functional properties, mda-7 is now recognized as interleukin-24 (IL-24), a new member of the expanding IL-10 gene family. Unique properties of mda-7/IL-24 include its ability to selectively induce growth suppression, apoptosis and radiosensitization in diverse human cancer cells, without causing similar effects in normal cells. The utility of mda-7/IL-24, administered by means of a replication-incompetent adenovirus, as a gene therapy for cancer has recently received validation in patients, highlighting an important phenomenon initially observed in pancreatic tumor cells, namely a 'potent bystander apoptosis-inducing effect' in adjacent tumor cells not initially receiving this gene product. We presently investigated the contribution of mda-7/IL-24 secreted by normal cells in mediating this 'bystander effect', and document that normal cells induced to produce mda-7/IL-24 following infection with recombinant adenoviruses expressing this cytokine secrete mda-7/IL-24, which modifies the anchorage-independent growth, invasiveness, survival and sensitivity to radiation of cancer cells that contain functional IL-20/IL-22 receptors, but not in cancer cells that lack a complete set of receptors. Moreover, the combination of secreted mda-7/IL-24 and radiation engenders a 'bystander antitumor effect' not only in inherently mda-7/IL-24 or radiation-sensitive cancer cells, but also in tumor cells overexpressing the antiapoptotic proteins bcl-2 or bcl-x(L) and displaying resistance to either treatment alone. The present studies provide definitive evidence that secreted mda-7/IL-24 from normal cells can induce direct antitumor and radiation-enhancing effects that are dependent on the presence of canonical receptors for this cytokine on tumor cells. Moreover, we now describe a novel means of enhancing mda-7/IL-24's therapeutic potential by targeting normal cells to produce and release this cancer-specific apoptosis-inducing cytokine, a strategy that could be employed as an innovative way of using this unique gene product for treating metastatic disease.

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.

The antagonistic regulation of human MUC4 and ErbB-2 genes by the Ets protein PEA3 in pancreatic cancer cells: implications for the proliferation/differentiation balance in the cells

The human transmembrane mucin MUC4 is aberrantly expressed in 75% of pancreatic ductal adenocarcinomas, whereas no expression is found in normal pancreas. Therefore MUC4 appears as a useful biological marker for the diagnosis of ductal adenocarcinomas. Since rat Muc4 was shown to interact with ErbB-2 tyrosine kinase receptor and to either promote cell survival and differentiation or cell proliferation, it is postulated that MUC4 may also participate in pancreatic carcinogenesis. Our aim was to investigate in parallel the role of the Ets factor PEA3 in MUC4 and ErbB-2 transcriptional regulation in pancreatic cancer cells. Two MUC4-expressing WD (well-differentiated) (CAPAN-1 and -2) and one MUC4-non-expressing poorly differentiated (PANC-1) cell lines were used. The three cell lines express ErbB-2 at different levels. By co-transfection and site-directed mutagenesis, we show that PEA3 is a transactivator of the MUC4 promoter and that the -216 and -2368 PEA3 binding sites of the MUC4 promoter are essential. We also demonstrate that PEA3 acts in synergy with c-Jun and specificity protein 1 to transactivate the proximal region of the MUC4 promoter and increase MUC4 mRNA levels in WD cells. These results suggest that MUC4 is a new target gene of the Ets factor PEA3 in pancreatic cancer cells. In contrast, PEA3 represses the transcriptional activity of two fragments of the ErbB-2 promoter in a dose-dependent manner and decreases the endogenous ErbB-2 mRNA levels in WD cell lines. Thus, PEA3, by its capacity to up-regulate the epithelial marker MUC4 and to down-regulate the ErbB-2 oncogene, appears as a key regulator of the differentiation/proliferation balance in pancreatic cancer cells.

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.

Detection of Ki-ras mutations in tissue and plasma samples of patients with pancreatic cancer using PNA-mediated PCR clamping and hybridisation probes

In the present study, we combined the PCR-clamping approach with melting curve analysis using mutant specific hybridisation probes and wild-type specific peptide nucleic acids (PNAs) to determine the genotypes of the most frequent point mutation in codon 12 of the proto-oncogene Ki-ras in tissue and plasma samples of patients with pancreatic cancer. The sensitivity of our assay was 1–5 × 10⁻⁵. The melting curve analysis of tissue samples of four patients revealed two valine mutations, one none-valine mutation and one wild-type sequence. Ki-ras alterations were found in 28% of DNAs (18 out of 64) of nonrelated plasma samples of 10 patients with ductal adenocarcinoma of the pancreas. The valine mutation was the predominantly detected gene alteration (83%). Out of ten patients investigated, four patients (40%) became positive during clinical observation with respect to Ki-ras mutation. All four patients exhibited progressive disease and high levels of tumour marker CA 19-9. In conclusion, the one-step procedure discribed may be a useful clinical tool for analysing Ki-ras point mutations in tissue and plasmas samples. In addition, this method can be adapted for simultanous detection of multiple mutations and quantitation.

Prognostic significance of activated Akt expression in pancreatic ductal adenocarcinoma

PURPOSE

Akt is a serine/threonine kinase that plays a central role in tumorigenesis. Among the members of Akt family, Akt2 is associated with the development of human cancers. The present study was designed to clarify the prognostic significance of Akt2 and activated Akt expression in pancreatic ductal adenocarcinoma (PDAC). In addition, activated extracellular signal-regulated kinase 1 and 2 (ERK1/2) and the proliferation activity of tumor cells detected by Ki-67 immunohistochemistry were examined.

EXPERIMENTAL DESIGN

Immunohistochemical analysis was performed on paraffin-embedded specimens from 65 patients with PDAC; 36 males and 29 females with ages ranging from 48 to 79 years (median, 66 years) of age. Expression levels of Akt2, phosphorylated Akt (p-Akt), and phosphorylated ERK 1/2 (p-ERK 1/2) were categorized as either weaker (low intensity) or equal to stronger (high intensity) compared with those in the endothelial cells of the same specimens. For Ki-67 immunohistochemistry, cases were divided into two groups: level 1, Ki-67 labeling index (LI), <20%; level 2, Ki-67 LI, > or = 20%.

RESULTS

Twenty-six (42.6%), 28 (45.9%), 39 (63.9%), and 46 (75.4%) of the tumors showed high intensity of Akt2, p-Akt, and p-ERK 1/2 expression, and Ki-67 LI level 2, respectively. A significant positive correlation was observed between Akt2 and p-Akt expression (P < 0.01). Multivariate analysis revealed that p-Akt expression, Ki-67 LI, and histological differentiation are independent prognosticators for PDAC.

CONCLUSIONS

p-Akt expression is a significant prognostic indicator for PDAC. Inhibition of Akt is a possible molecular approach for treatment of PDAC.

Mechanistic aspects of mda-7/IL-24 cancer cell selectivity analysed via a bacterial fusion protein

The human mda-7/IL-24 gene product is normally expressed in melanocytes and certain lymphocyte populations. Loss of expression, a distinctive feature of many tumor suppressor genes, has been documented at RNA and protein levels in association with melanoma progression both in vitro as well as in human tumor-derived material. The MDA-7/IL-24 protein undergoes post-translational processing, including removal of an amino-terminal 48-residue signal peptide and extensive glycosylation prior to its secretion by producing cells. Its inherent cytokine properties have been documented in multiple reports, which have identified and characterized its cognate receptors and activation of the JAK/STAT signaling pathway following ligand/receptor docking. A notable and incompletely understood property of MDA-7/IL-24 is its ability to induce apoptosis in transformed cells, while having marginal growth suppressive effects on normal primary or immortalized cell lines. MDA-7/IL-24 has been delivered to cells, tumor xenografts and patients in clinical trials via a nonreplicating adenovirus (Ad.mda-7). Studies utilizing eukaryotically expressed and purified MDA-7/IL-24 protein from several sources have recapitulated some of the molecule's reported properties including receptor binding and JAK/STAT activation. Here, we report the properties and characteristics of a bacterially expressed and purified GST-MDA-7 fusion protein. These studies reveal that GST-MDA-7 retains its cancer-selective apoptosis-inducing properties, thereby providing a new reagent that will assist in defining the mechanism of action of this novel cytokine. In addition, retention of tumor-specific activity of GST-MDA-7 suggests that this protein may also have therapeutic applications.

Molecular therapy in pancreatic adenocarcinoma

Pancreatic cancer is one of the commonest causes of death from cancer. Despite therapy with surgery, conventional chemotherapy, and radiation, 5-year survival for patients with this diagnosis remains poor. However, advances in the molecular understanding of this malignant disease over the past 5 years might lead to new treatment strategies. Strategies of gene therapy, antiangiogenic treatments, immunotherapy, and signal-transduction inhibition are in preclinical development. This review presents an overview of molecular therapy in pancreatic cancer.

Adenovirus-mediated retinoblastoma 94 gene transfer induces human pancreatic tumor regression in a mouse xenograft model

PURPOSE

Gene transfer of a truncated variant of the retinoblastoma (RB) gene encoding a M(r) 94000 protein that lacks the NH(2)-terminal 112 amino acid residues, termed RB94, has been shown to inhibit proliferation of several human tumor cell types. We have assessed its therapeutic effectiveness on pancreatic cancer, one of the most aggressive and therapy-resistant types of cancer. For this purpose, preclinical studies aimed to evaluate the therapeutic potential of RB94 gene transfer in pancreatic cancer were carried out.

EXPERIMENTAL DESIGN

We have compared the antiproliferative effects of adenovirus-mediated gene transfer of RBwt and RB94 at the in vitro and in vivo levels in three RB-positive human pancreatic tumor cell lines: (a). NP-9; (b). NP-18; and (c). NP-31. We have also examined their effects on cell cycle and their capacity to induce apoptosis.

RESULTS

In vitro results indicate that RB94 gene transfer has stronger antiproliferative effects compared with RBwt. RB94 transduction correlated with accumulation at the S-G(2) phase of the cell cycle in the three cell lines tested and induction of apoptosis in two of them. In vivo studies show significant decreases in the growth rate of tumors treated with Ad-RB94 when compared with those treated with Ad-RBwt. Moreover, terminal deoxynucleotidyl transferase-mediated nick end labeling analyses of Ad-RB94-treated tumor sections revealed that only RB94 is able to significantly induce apoptosis.

CONCLUSIONS

RB94 gene expression has antiproliferative effects also in human pancreatic tumor cells, being more effective than wild-type RB in preventing tumor growth.

The PI 3-kinase/Akt signaling pathway is activated due to aberrant Pten expression and targets transcription factors NF-κB and c-Myc in pancreatic cancer cells

The persistent activation of signaling cascades results in dramatic consequences that include loss of cellular growth control and neoplastic transformation. We show here that phosphoinositide 3-kinase (PI 3-kinase) and its mediator Akt were constitutively activated in pancreatic cancer and that this might be due to the aberrant expression of their natural antagonist MMAC/PTEN. Indeed, our results show that MMAC/PTEN expression was either lost or significantly reduced in five of eight cell lines and in twelve of seventeen tumor specimens examined. That the poor expression of MMAC/PTEN in pancreatic cancer cells could be due to promoter methylation was indicated by methylation-specific PCR analysis. Our studies also indicated that PI 3-kinase targeted two important transcription factors in pancreatic cancer cells. The ability of constitutively activated NF-kappaB to induce gene expression and the stabilization of c-MYC protein by decreased phosphorylation of Thr58 were both dependent on PI 3-kinase activity. When pancreatic cancer cells were treated with a peptide antagonist of NF-kappaB nuclear translocation, or stably transfected with a dominant-negative mutant of MYC, their proliferation was markedly inhibited. Taken together, these data indicate that the aberrant expression of MMAC/PTEN contributes to the activation of the PI 3-kinase/Akt pathway and its transcription factor mediators in pancreatic cancer.

Abnormal Fhit protein expression and high frequency of microsatellite instability in sporadic colorectal cancer

The role of Fhit protein in the oncogenesis of colorectal cancer is still in debate. Recent studies have revealed that reduced Fhit protein expression is associated with a deficiency of the mismatch repair protein. One hundred and twenty unselected patients who underwent curative resection for sporadic colorectal cancer in a three-year period were evaluated for microsatellite instability (MSI) using six microsatellite markers, and for the presence of Fhit and mismatch repair (MMR) proteins (Mlh1 and Msh2) by means of immunostaining. The relations between these markers were analysed. Reduced or absent Fhit expression was noted in 18 out of 118 patients. This altered expression was significantly higher in right-sided cancer (P = 0.005), mucinous tumours (P = 0.005) and in poorly differentiated histological types (P = 0.0001). MSI was found in 22 out of 109 patients, more so in right-sided cancer (P = 0.0001), poorly differentiated histology (P = 0.0001), and mucinous tumours (P = 0.0001). No association was found with TNM stage. MSI was present in 66.7% of tumours with altered Fhit expression and in only 10% of tumours with preserved or intermediate Fhit expression (P = 0.0001). Of the tumours with reduced or absent Fhit expression, 72.2% had loss of nuclear Mlh1 or Msh2 expression compared with only 14% of the preserved or intermediate Fhit expression tumours (P = 0.0001). These results support the hypothesis that deficiency in a MMR gene could be a cause of the high frequency of alterations in Fhit expression, and they permit the suggestion that FHIT gene alteration may be part of the genetic pathway involving MSI through which some colorectal cancers arise.

Effect of FHIT gene replacement on growth, cell cycle and apoptosis in pancreatic cancer cells

The human FHIT gene is altered or lost in many cancers and FHIT has been shown to be a tumor suppressor. However, the mechanism of tumor suppression by the FHIT gene remains unclear. FHIT expression is lost in primary pancreatic cancer and human pancreatic cancer cell lines. To gain insight into the function of FHIT gene, we replaced the FHIT gene in a FHIT-null pancreatic cancer cell line, and established stable fhit-expressing clones. Expression of the exogenous fhit was at similar levels as in other cultured cell lines and fhit protein was found predominantly associated with perinuclear area. fhit replacement resulted in reduced cell proliferation in transfected Panc-1 cells. Cell cycle distribution analysis indicated increased accumulation of G(0)/G(1) phase cells in transfected clones indicating a retardation of cell cycle progression. We observed specific up-regulation of cdc2 and cyclin D3 upon fhit replacement. Furthermore, Bcl-2 family members Bad, Bak, and Bcl-xS protein levels were increased in FHIT transfected clones when compared with Panc-1 cells. Multiplex RT-PCR of apoptosis pathway related genes revealed that Bcl-2 is absent and Bcl- xS message increases in FHIT transfected clones. Our data suggested that exogenous expression of FHIT in Panc-1 cells affects genes regulating cell cycle arrest and apoptosis, and these molecular changes may contribute to the tumor suppressor activity of the FHIT gene.

Fhit expression in human gastric adenomas and intramucosal carcinomas: correlation with Mlh1 expression and gastric phenotype

The fragile histidine triad (FHIT) gene, encompassing the FRA3B fragile site at chromosome 3p14.2, is a candidate tumour suppressor gene involved in a variety of tumours, including gastric carcinomas. Recently, it has been reported that the FHIT gene may be a target of damage in some of mismatch-deficient tumours. To clarify further the role of the Fhit protein in gastric carcinogenesis, we investigated whether Fhit expression in early gastric neoplasia is associated with mismatch repair protein expression and cellular phenotype. Fhit, Mlh1 and phenotypic expression were evaluated immunohistochemically in 87 early gastric neoplasias, comprising 32 adenomas and 55 intramucosal carcinomas, resected by endoscopic mucosal resection therapy. Significant loss or reduction of Fhit expression was noted in four (12.5%) of the 32 adenomas and 21 (38.2%) of the 55 intramucosal carcinomas. The rate of abnormal Fhit expression was significantly higher in intramucosal carcinomas than in adenomas (P=0.021). Moreover, reduced Fhit expression was found to be significantly associated with loss of Mlh1 expression in early gastric neoplasia (P=0.0011). Furthermore, we also detected a significant association between reduced Fhit expression and gastric phenotype (P=0.0018). These results suggested that reduced Fhit expression occurs in the early stage of gastric carcinogenesis and could be correlated with a lack of Mlh1 expression and gastric phenotype.

Terminally modified oligodeoxynucleotides directed against p53 in an orthotopic xenograft model: a novel adjuvant treatment strategy for pancreatic ductal carcinoma

OBJECTIVES

Investigation of a terminally modified oligodeoxynucleotide (ODN) directed against p53 mRNA (p53-3' polyethylene glycol-5' tocopherol ODN as a novel drug for pancreatic ductal carcinoma therapy in vitro and in vivo.

METHODS

The impact of lipophilic modifications at the 5' end of p53-directed ODNs on cellular uptake was analyzed in vitro using proliferation assays, fluorescence-activated cell sorting analysis, and confocal laser scanning microscopy. The in vivo effects of p53-PT-ODN on the growth of orthotopically xenografted human pancreatic ductal carcinoma cells (PancTuI) were studied in SCID beige mice. Distribution was examined in vitro and in vivo using Cy3-labeled ODNs.

RESULTS

Terminally modified p53-PT-ODN showed excellent cellular uptake without using transfection reagents. Microscopically detectable levels of p53-PT-ODN were reached in vivo within 3 hours after intraperitoneal injection, even in extraperitoneal organs. At this time, Cy3-labeled p53-PT-ODN was found in solid tumor formations. We observed a significant inhibition of tumor growth (50%) in vivo at low doses of p53-PT-ODN, whereas at high doses, 2 of 9 animals had no detectable tumors at necropsy. When p53-PT-ODN was injected on the day of tumor cell inoculation, the growth inhibition of solid tumors was significantly stronger compared with that with delayed treatment.

CONCLUSIONS

p53-Directed modified ODNs might be of therapeutic value in pancreatic ductal carcinoma, particularly as adjuvant therapy after pancreatic tumor resection.

Systematic isolation of genes differentially expressed in normal and cancerous tissue of the pancreas

BACKGROUND

There is increasing knowledge about the genetic basis of pancreatic cancer (PaCa). Tumor suppressor genes (TSGs; e.g. p53 and DPC4) and oncogenes (e.g. K-ras) have been shown to be involved in the development of PaCa. However, the extent of chromosomal changes (gains and losses) implicates that many more genes may be involved in the multistep progression of PaCa. Identification of these genes is essential for understanding the molecular events in the development of PaCa.

METHODS

We assembled public and proprietary libraries of more than 4 million expressed sequence tags using newly developed software tools.

RESULTS

We identified a total of 249 genes with specific expression patterns in normal and cancerous tissue of the pancreas. Of these, 27 genes were found to be preferentially expressed in normal tissue of the pancreas, while 222 genes showed significant upregulation of expression in PaCa. Of the 249 genes, 232 (93.2%) were found to represent known human genes or putative human homologues of genes characterized previously in other species, while 17 (6.8%) represent putative new genes.

CONCLUSION

These genes may represent a valuable source to identify novel TSGs and oncogenes involved in the carcinogenesis of PaCa.

Expression of Fhit, Mlh1, and P53 protein in human gallbladder carcinoma

There is limited information on the molecular changes involved in the pathogenesis of gallbladder carcinoma (GBC). The Fragile Histidine Triad (FHIT) gene, encompassing the FRA3B fragile site at chromosome 3p14.2, is a candidate tumor suppressor gene in a variety of human malignancies. Recent studies have suggested that Fhit inactivation can be a consequence of defects in mismatch repair proteins. We analyzed Fhit and Mlh1 protein expressions using immunohistochemical methods in 20 GBCs and three gallbladder adenomas (GBAs) to elucidate the role of Fhit protein in gallbladder carcinogenesis. In addition, we examined whether Fhit and Mlh1 protein expressions correlated with P53 expression and clinicopathological findings. Significant loss or reduction in Fhit expression was noted in nine (45%) of the GBCs and one of the GBAs. Loss of Mlh1 protein expression was detected in six (30%) of the GBCs and one of the GBAs. Reduced Fhit expression was significantly associated with the absence of Mlh1 protein expression in the GBCs and the GBAs (p=0.0186). P53 overexpression was present in 11 (55%) of the GBCs, but none of the GBAs. Fhit and Mlh1 protein expressions were not significantly associated with P53 expression and clinicopathological findings. These results suggested that reduced Fhit expression might be involved in the development of GBC and be correlated with Mlh1 expression.

Increased PDX-1 expression is associated with outcome in patients with pancreatic cancer

BACKGROUND

During pancreatic development, pancreatic duodenal homeobox gene-1 (PDX-1) is expressed in pancreatic duct cells that have the potential to differentiate into islets. Therefore, PDX-1 is thought to be a marker of de-differentiated cells with the capacity to redifferentiate into several pancreatic cell types. We analyzed PDX-1 expression in human pancreatic cancer specimens, pancreatic cancer cell lines, and the effects of forced expression of PDX-1 in pancreatic cancer cells.

METHODS

Thirty-five pancreatic adenocarcinomas were immunohistochemically stained with a polyclonal rabbit antibody against mouse PDX-1. Correlations with tumor characteristics were made with chi-squared analysis. The influence of clinicopathologic factors on survival was assessed. The expression of PDX-1 in pancreatic cancer cells was examined. Replication-deficient recombinant adenoviruses were constructed by the cosmid-adenoviral DNA terminal protein complex method. PANC-1 cells were infected with Ad-pdx-1 or Ad-LacZ. PANC-1 cells that were infected with adenovirus were used in a cell growth assay and a migration assay and for morphologic analysis.

RESULTS

Interestingly, 43% of pancreatic cancers were positive for PDX-1 expression, and 57% of pancreatic cancers were negative (normal pancreatic exocrine tissue shows little or no staining for PDX-1). Lymph node metastasis (P =.02) and histologic grade (P =.04) were correlated significantly with PDX-1 expression. Patients with positive PDX-1 had a significantly worse prognosis than those patients with negative PDX-1 (P =.02). Importantly, PDX-1 was an independent variable that effected overall survival (P =.03). Pancreatic cancer cell lines showed no PDX-1 expression. There were no significant differences in cell proliferation or morphologic condition between Ad-pdx-1- and Ad-lacZ-infected PANC-1 cells. However, Ad-pdx-1-infected PANC-1 cells did show a significantly higher migration rate than Ad-lacZ-infected PANC-1 cells.

CONCLUSIONS

Re-expression of PDX-1 may represent a return to a more de-differentiated state by more aggressive pancreatic cancers and may also represent an important new tumor marker for these aggressive cancers.

Zoledronic acid induces antiproliferative and apoptotic effects in human pancreatic cancer cells in vitro

Bisphosphonates (BPs) are an emerging class of drugs mostly used in the palliative care of cancer patients. We investigated the in vitro activity of the most potent antiresorptive BP, zoledronic acid (ZOL), on the growth and survival of three human pancreatic cancer (PC) cell lines (BxPC-3, CFPAC-1 and PANC-1). Pancreatic cancer frequently has a dysregulated p21(ras) pathway and therefore appears to be a suitable target for BPs that interfere with the prenylation of small GTP-binding proteins such as p21(ras). We found that ZOL induces growth inhibition (IC(50):10-50 micro M) and apoptotic death of PC cells. The proapoptotic effect was correlated to cleavage/activation of caspase-9 and poly(ADP)-ribose polymerase, but not of caspase-3. Moreover, we studied the p21(ras) signalling in cells exposed to ZOL and detected a reduction of p21(ras) and Raf-1 content and functional downregulation of the terminal enzyme ERK/MAPkinase and of the pKB/Akt survival pathway. Finally, we observed that ZOL induces significant cytoskeletal rearrangements. In conclusion, we demonstrated that ZOL induces growth inhibition and apoptosis on PC cells and interferes with growth and survival pathways downstream to p21(ras). These findings might be relevant for expanding application of BPs in cancer treatment.

A population-based study of Ashkenazi Jewish women's attitudes toward genetic discrimination and BRCA1/2 testing

PURPOSE

The Human Genome Project continues to produce an increasing number of genetic susceptibility tests. Some of these genetic tests target social or ethnic groups who are at increased risk of developing a disease. The Ashkenazi Jewish community is one ethnic group that is an ongoing subject of genetic investigation. We assessed the attitudes of a population-based sample of Ashkenazi Jewish women toward breast-ovarian cancer susceptibility testing (BRCA 1/2). In particular, we assessed concerns about group discrimination, perceptions of the advantages and disadvantages of testing, and the relationship between concerns about discrimination and the potential benefits of genetic testing.

METHODS

A telephone survey of a population-based sample of 200 Jewish women.

RESULTS

A minority of women (17%) in this study expressed concern or discomfort with Jews being offered testing. Most women believed there were scientific reasons for testing Jews (71%), and only 5% of women felt that research that focused on Jews was bad for Jews as a group. Increased concern about genetic discrimination was associated with women who were highly educated (odds ratio 2.68). Forty percent of women surveyed were interested in testing, 40% were not interested, and 20% were uncertain about whether they would obtain testing. Increased interest in genetic testing was associated with a desire to obtain information about children's risk of disease and valuing information for its own sake.

CONCLUSIONS

The majority of a population-based sample of Jewish women did not express concerns about group discrimination resulting from genetic testing. Women who are highly educated are more concerned about genetic discrimination. There is significant variation among Jewish women's interest in breast cancer susceptibility testing.

Reduced Fhit expression is associated with mismatch repair deficiency in human advanced colorectal carcinoma

The Fragile Histidine Triad gene, encompassing the FRA3B fragile site at chromosome 3p14.2, is a candidate tumour suppressor gene involved in multiple tumour types including colorectal carcinomas. Recently, it has been reported that the Fragile Histidine Triad gene may be a target of damage in a fraction of mismatch deficient tumours. To explore this hypothesis, we analysed both Fragile histidine triad and mismatch repair protein (Msh2 and Mlh1) expression using immumohistochemical methods in 52 advanced colorectal carcinomas (19 well-, 17 moderately-, and 16 poorly-differentiated). In addition, we examined whether the Fragile histidine triad and mismatch repair protein expression correlated with p53 expression and clinicopathological findings. Significant loss or reduction of Fragile histidine triad expression was noted in 18 of the 52 (34.6%) advanced colorectal carcinomas: 2 (10.5%) well-differentiated, 3 (17.6%) moderately-differentiated, 13 (81.3%) poorly-differentiated carcinomas, the frequency being significantly higher in the latter than that in the former two (P<0.0001). Loss of mismatch repair protein (mainly, Mlh1) expression was detected in 21 of the 52 (40.4%) colorectal carcinomas. Moreover, reduced Fragile histidine triad expression was significantly associated with absence of mismatch repair protein expression in the advanced colorectal carcinomas (P<0.0001). However, the Fragile histidine triad and mismatch repair protein expression was not significantly associated with p53 expression. These results suggested that reduced Fragile histidine triad expression might be correlated with mismatch repair expression, but not with p53 expression.

Cytogenetic and molecular genetic evolution of chronic myeloid leukemia

Chronic myeloid leukemia (CML) is genetically characterized by the presence of the reciprocal translocation t(9;22)(q34;q11), resulting in a BCR/ABL gene fusion on the derivative chromosome 22 called the Philadelphia (Ph) chromosome. In 2-10% of the cases, this chimeric gene is generated by variant rearrangements, involving 9q34, 22q11, and one or several other genomic regions. All chromosomes have been described as participating in these variants, but there is a marked breakpoint clustering to chromosome bands 1p36, 3p21, 5q13, 6p21, 9q22, 11q13, 12p13, 17p13, 17q21, 17q25, 19q13, 21q22, 22q12, and 22q13. Despite their genetically complex nature, available data indicate that variant rearrangements do not confer any specific phenotypic or prognostic impact as compared to CML with a standard Ph chromosome. In most instances, the t(9;22), or a variant thereof, is the sole chromosomal anomaly during the chronic phase (CP) of the disease, whereas additional genetic changes are demonstrable in 60-80% of cases in blast crisis (BC). The secondary chromosomal aberrations are clearly nonrandom, with the most common chromosomal abnormalities being +8 (34% of cases with additional changes), +Ph (30%), i(17q) (20%), +19 (13%), -Y (8% of males), +21 (7%), +17 (5%), and monosomy 7 (5%). We suggest that all these aberrations, occurring in >5% of CML with secondary changes, should be denoted major route abnormalities. Chromosome segments often involved in structural rearrangements include 1q, 3q21, 3q26, 7p, 9p, 11q23, 12p13, 13q11-14, 17p11, 17q10, 21q22, and 22q10. No clear-cut differences as regards type and prevalence of additional aberrations seem to exist between CML with standard t(9;22) and CML with variants, except for slightly lower frequencies of the most common changes in the latter group. The temporal order of the secondary changes varies, but the preferred pathway appears to start with i(17q), followed by +8 and +Ph, and then +19. Molecular genetic abnormalities preceding, or occurring during, BC include overexpression of the BCR/ABL transcript, upregulation of the EVI1 gene, increased telomerase activity, and mutations of the tumor suppressor genes RB1, TP53, and CDKN2A. The cytogenetic evolution patterns vary significantly in relation to treatment given during CP. For example, +8 is more common after busulfan than hydroxyurea therapy, and the secondary changes seen after interferon-alpha treatment or bone marrow transplantation are often unusual, seemingly random, and occasionally transient. Apart from the strong phenotypic impact of addition of acute myeloid leukemia/myelodysplasia-associated translocations and inversions, such as inv(3)(q21q26), t(3;21)(q26;q22), and t(15;17)(q22;q12-21), in CML BC, only a few significant differences between myeloid and lymphoid BC are discerned, with i(17q) and TP53 mutations being more common in myeloid BC and monosomy 7, hypodiploidy, and CDKN2A deletions being more frequent in lymphoid BC. The prognostic significance of the secondary genetic changes is not uniform, although abnormalities involving chromosome 17, e.g., i(17q), have repeatedly been shown to be ominous. However, the clinical impact of additional cytogenetic and molecular genetic aberrations is most likely modified by the treatment modalities used.

Cell-specific transgene expression from a widely transcribed promoter using Cre/lox in mice

Mice carrying two or more transgenes are used frequently to evaluate oncogene interactions during carcinogenesis. However, neoplastic transformation typically results in reduced expression both of differentiation-specific genes and of transgenes that use their promoters. In contrast, the more widely expressed metallothionein (MT) gene remains expressed at a high level in certain neoplasms, including those developing in pancreas. We have developed a system to maintain high-level, tissue-specific transgene expression during pancreatic carcinogenesis that uses Cre recombinase and a lox site-containing target transgene. Cre was expressed in pancreatic acinar cells under control of the elastase promoter (EL). Cre-mediated target transgene recombination placed a previously silent open-reading frame, encoding rat transforming growth factor alpha (TGFalpha), under control of the MT gene promoter. As long as DNA rearrangement does not occur in other cell types that express MT, TGFalpha expression will be restricted to acinar cells. Development of an effective target transgenic mouse required evaluation of multiple lineages to identify one with sufficient TGFalpha expression to induce pancreatic lesions after transgene rearrangement.

Genetic evolution in the metastatic progression of human pancreatic cancer studied by CGH

Metastases are thought to be derived from emerging clones within primary tumors. Although the concept of the clonal evolution of cancer is well defined, the genetic grounds and significance of this process in human cancer progression are still poorly understood. To gain insight into the genetic basis and clonal evolution underlying the metastatic progression of human pancreatic cancer in vivo, we analyzed by comparative genomic hybridization (CGH) chromosomal imbalances in seven metastases originated in nude mice and their three corresponding orthotopically xenografted human pancreatic tumors. All metastases were found to be closely related to the corresponding orthotopic implant, adding many additional changes to the already altered copy number profile of the pancreatic tumors. Recurrent metastasis-specific alterations included gains at 16cen-q22 and 17q21-qter. CGH results from paired specimens strongly suggest that the majority of additional genetic alterations present in metastases are likely to be present in subclones in the primary tumor.

A combinatorial approach for selectively inducing programmed cell death in human pancreatic cancer cells

Pancreatic cancer is an extremely aggressive neoplasm whose incidence equals its death rate. Despite intensive analysis, the genetic changes that mediate pancreatic cancer development and effective therapies for diminishing the morbidity associated with this disease remain unresolved. Through subtraction hybridization, we have identified a gene associated with induction of irreversible growth arrest, cancer reversion, and terminal differentiation in human melanoma cells, melanoma differentiation associated gene-7 (mda-7). Ectopic expression of mda-7 when using a recombinant adenovirus, Ad.mda-7, results in growth suppression and apoptosis in a broad spectrum of human cancers with diverse genetic defects, without exerting deleterious effects in normal human epithelial or fibroblast cells. Despite the apparently ubiquitous antitumor effects of mda-7, pancreatic carcinoma cells are remarkably refractory to Ad.mda-7 induced growth suppression and apoptosis. In contrast, the combination of Ad.mda-7 with antisense phosphorothioate oligonucleotides, which target the K-ras oncogene (a gene that is mutated in 85 to 95% of pancreatic carcinomas), induces a dramatic suppression in growth and a decrease in cell viability by induction of apoptosis. In mutant K-ras pancreatic carcinoma cells, programmed cell death correlates with expression and an increase, respectively, in MDA-7 and BAX proteins and increases in the ratio of BAX to BCL-2 proteins. Moreover, transfection of mutant K-ras pancreatic carcinoma cells with an antisense K-ras expression vector and infection with Ad.mda-7 inhibits colony formation in vitro and tumorigenesis in vivo in nude mice. These intriguing observations demonstrate that a combinatorial approach, consisting of a cancer-specific apoptosis-inducing gene and an oncogene inactivation strategy, may provide the foundation for developing an effective therapy for pancreatic cancer.

Stepwise progression of centrosome defects associated with local tumor growth and metastatic process of human pancreatic carcinoma cells transplanted orthotopically into nude mice

Recent evidence indicates that loss of centrosome integrity may be a major cause of genetic instability underlying various human cancers. The aim of this study was to define the role of centrosome defects during the in vivo tumor progression of pancreatic carcinoma using an orthotopic implantation model. Injection of Suit-2 human pancreatic cancer cells into the pancreata of nude mice reproduced the pattern of local tumor growth and distant metastasis observed in humans. Pancreatic xenografts, peritoneal disseminations, and hepatic metastases were harvested, and tumor cells were examined for centrosomes by immunofluorescence microscopy. Centrosome abnormalities, characterized by increased numbers of centrosomes, were detected in only a small fraction of parental Suit-2 cells in culture, whereas the frequency was markedly increased in cells isolated from the pancreatic xenografts. Abnormal centrosome numbers were found at higher frequencies in metastatic foci than in pancreatic xenografts. A significant positive correlation existed between the fraction of cells with multiple centrosomes and that with multipolar mitotic spindles, suggesting a functional involvement of aberrant centrosomes in spindle disorganization and chromosome missegregation. In addition, the increased frequency of abnormal centrosomes was associated with an enhanced degree of chromosomal instability. These findings suggest a novel model of pancreatic tumor progression whereby a stepwise increase in the magnitude of centrosomal abnormalities confers an increased chance for aberrant mitotic events, thus accelerating genetic instability and causing the tumor to progress to a more advanced stage.