Overexpression of pRB in human pancreatic carcinoma cells: function in chemotherapy-induced apoptosis

Albumin conjugation promotes arsenic trioxide transport through alkaline phosphatase-associated transcytosis in MUC4 wildtype pancreatic cancer cells

Pancreatic cancer (PC) has a poor prognosis due to chemotherapy resistance and unfavorable drug transportation. Albumin conjugates are commonly used as drug carriers to overcome these obstacles. However, membrane-bound glycoprotein mucin 4 (MUC4) has emerged as a promising biomarker among the genetic mutations affecting albumin conjugates therapeutic window. Human serum albumin-conjugated arsenic trioxide (HSA-ATO) has shown potential in treating solid tumors but is limited in PC therapy due to unclear targets and mechanisms. This study investigated the transport mechanisms and therapeutic efficacy of HSA-ATO in PC cells with different MUC4 mutation statuses. Results revealed improved penetration of ATO into PC tumors through conjugated with HSA. However, MUC4 mutation significantly affected treatment sensitivity and HSA-ATO uptake both in vitro and in vivo. Mutant MUC4 cells exhibited over ten times higher IC50 for HSA-ATO and approximately half the uptake compared to wildtype cells. Further research demonstrated that ALPL activation by HSA-ATO enhanced transcytosis in wildtype MUC4 PC cells but not in mutant MUC4 cells, leading to impaired uptake and weaker antitumor effects. Reprogramming the transport process holds potential for enhancing albumin conjugate efficacy in PC patients with different MUC4 mutation statuses, paving the way for stratified treatment using these delivery vehicles.

Reboot: a straightforward approach to identify genes and splicing isoforms associated with cancer patient prognosis

Nowadays, the massive amount of data generated by modern sequencing technologies provides an unprecedented opportunity to find genes associated with cancer patient prognosis, connecting basic and translational research. However, treating high dimensionality of gene expression data and integrating it with clinical variables are major challenges to perform these analyses. Here, we present Reboot, an integrative approach to find and validate genes and transcripts (splicing isoforms) associated with cancer patient prognosis from high dimensional expression datasets. Reboot innovates by using a multivariate strategy with penalized Cox regression (LASSO method) combined with a bootstrap approach, in addition to statistical tests and plots to support the findings. Applying Reboot on data from 154 glioblastoma patients, we identified a three-gene signature (IKBIP, OSMR, PODNL1) whose increased derived risk score was significantly associated with worse patients' prognosis. Similarly, Reboot was able to find a seven-splicing isoforms signature related to worse overall survival in 177 pancreatic adenocarcinoma patients with elevated risk scores after uni- and multivariate analyses. In summary, Reboot is an efficient, intuitive and straightforward way of finding genes or splicing isoforms signatures relevant to patient prognosis, which can democratize this kind of analysis and shed light on still under-investigated cancer-related genes and splicing isoforms.

The necrosome promotes pancreatic oncogenesis via CXCL1 and Mincle-induced immune suppression

Neoplastic pancreatic epithelial cells are believed to die through caspase 8-dependent apoptotic cell death, and chemotherapy is thought to promote tumour apoptosis. Conversely, cancer cells often disrupt apoptosis to survive. Another type of programmed cell death is necroptosis (programmed necrosis), but its role in pancreatic ductal adenocarcinoma (PDA) is unclear. There are many potential inducers of necroptosis in PDA, including ligation of tumour necrosis factor receptor 1 (TNFR1), CD95, TNF-related apoptosis-inducing ligand (TRAIL) receptors, Toll-like receptors, reactive oxygen species, and chemotherapeutic drugs. Here we report that the principal components of the necrosome, receptor-interacting protein (RIP)1 and RIP3, are highly expressed in PDA and are further upregulated by the chemotherapy drug gemcitabine. Blockade of the necrosome in vitro promoted cancer cell proliferation and induced an aggressive oncogenic phenotype. By contrast, in vivo deletion of RIP3 or inhibition of RIP1 protected against oncogenic progression in mice and was associated with the development of a highly immunogenic myeloid and T cell infiltrate. The immune-suppressive tumour microenvironment associated with intact RIP1/RIP3 signalling depended in part on necroptosis-induced expression of the chemokine attractant CXCL1, and CXCL1 blockade protected against PDA. Moreover, cytoplasmic SAP130 (a subunit of the histone deacetylase complex) was expressed in PDA in a RIP1/RIP3-dependent manner, and Mincle--its cognate receptor--was upregulated in tumour-infiltrating myeloid cells. Ligation of Mincle by SAP130 promoted oncogenesis, whereas deletion of Mincle protected against oncogenesis and phenocopied the immunogenic reprogramming of the tumour microenvironment that was induced by RIP3 deletion. Cellular depletion suggested that whereas inhibitory macrophages promote tumorigenesis in PDA, they lose their immune-suppressive effects when RIP3 or Mincle is deleted. Accordingly, T cells, which are not protective against PDA progression in mice with intact RIP3 or Mincle signalling, are reprogrammed into indispensable mediators of anti-tumour immunity in the absence of RIP3 or Mincle. Our work describes parallel networks of necroptosis-induced CXCL1 and Mincle signalling that promote macrophage-induced adaptive immune suppression and thereby enable PDA progression.

CARF (Collaborator of ARF) overexpression in p53-deficient cells promotes carcinogenesis

Collaborator of ARF (CARF), initially identified as a binding partner of ARF (Alternate Reading Frame), has been shown to activate ARF-p53 pathway by multiple ways including stabilization of ARF and p53 tumor suppressor proteins, and transcriptional repression of a p53 antagonist, HDM2. Level of CARF expression was shown to determine fate of cells. Whereas its knockdown caused apoptosis, its over- and super-expressions caused senescence and increase in malignant properties of cancer cells, respectively, and were closely linked to increase and decrease in p53 activity. Using p53-compromised cancer cells, we demonstrate that CARF induces growth arrest when wild type p53 is present and in p53-absence, it promotes carcinogenesis. Biochemical analyses on CARF-induced molecular signaling revealed that in p53-null cells, it caused transcriptional repression of p21(WAF1) leading to increase in CDK4, CDK6, pRb and E2F1 resulting in continued cell cycle progression. Furthermore, it instigated increase in migration and invasion of cancer cells that was marked by upregulation of MMP2, MMP3, MMP9, uPA, several interleukins and VEGF expression. Consistent with these findings, we found that human clinical samples of epithelial and glial cancers (frequently marked by loss of p53 function) possessed high level of CARF expression showing a relationship with cancer aggressiveness. The data demonstrated that CARF could be considered as a diagnostic marker and a therapeutic target in p53-compromised malignancies.

A multistep high-content screening approach to identify novel functionally relevant target genes in pancreatic cancer

In order to foster the systematic identification of novel genes with important functional roles in pancreatic cancer, we have devised a multi-stage screening strategy to provide a rational basis for the selection of highly relevant novel candidate genes based on the results of functional high-content analyses. The workflow comprised three consecutive stages: 1) serial gene expression profiling analyses of primary human pancreatic tissues as well as a number of in vivo and in vitro models of tumor-relevant characteristics in order to identify genes with conspicuous expression patterns; 2) use of ‘reverse transfection array’ technology for large-scale parallelized functional analyses of potential candidate genes in cell-based assays; and 3) selection of individual candidate genes for further in-depth examination of their cellular roles. A total of 14 genes, among them 8 from “druggable” gene families, were classified as high priority candidates for individual functional characterization. As an example to demonstrate the validity of the approach, comprehensive functional data on candidate gene ADRBK1/GRK2, which has previously not been implicated in pancreatic cancer, is presented.

Prevalence and prognostic value of human papillomavirus genotypes in tonsillar squamous cell carcinoma: a Korean multicenter study

BACKGROUND

This study was aimed at investigating the change in the prevalence of human papillomavirus (HPV) genotypes in tonsillar squamous cell carcinoma (TSCC) and the association of the HPV genotype with the prognosis.

METHODS

This multicenter study included 175 patients with TSCC from 3 general hospitals between 1991 and 2009. HPV DNA was detected in paraffin-embedded tissues with genotyping chips. A survival analysis that considered clinicopathological factors, the HPV genotype, and the expression of p53, retinoblastoma protein, p16, and epidermal growth factor receptor (assessed with immunohistochemistry) was performed with Cox regression analysis.

RESULTS

High-risk HPV types were found in 23.4% of the cases. The prevalence of HPV-18 (10.3%) was as high as that of HPV-16 (10.3%). The proportion of high-risk HPV-positive tumors increased from 5.9% in 1991 to 31.6% in 2009. HPV-16 positivity was associated with an advanced stage and lymph node metastasis, whereas HPV-18 positivity was associated with old age and an advanced T stage. The survival analysis showed that old age and T classification were poor prognostic factors, whereas the expressions of various biomarkers were not associated with prognosis. HPV-18-positive cases had a poorer prognosis than HPV-16-positive cases and non-HPV-related TSCC cases. A multivariate analysis revealed that HPV-18 positivity, old age, and an advanced T stage were independent prognostic factors for predicting poor outcomes for patients with TSCC.

CONCLUSIONS

The proportion of HPV-positive tonsillar cancer cases has increased during the last 20 years in the Republic of Korea. The presence of HPV-18 may serve as a biomarker for a poor prognosis.

E2F transcription factors and digestive system malignancies: How much do we know?

The E2F proteins comprise a family of 8 members that function as transcription factors. They are key targets of the retinoblastoma protein (RB) and were initially divided into groups of activators and repressors. Accumulating data suggest that there is no specific role for each individual E2F member. Instead, each E2F can exert a variety of cellular effects, some of which represent opposing ones. For instance, specific E2Fs can activate transcription and repression, promote or hamper cell proliferation, augment or inhibit apoptosis, all being dependent on the cellular context. This complexity reflects the importance that these transcription factors have on a cell’s fate. Thus, delineating the specific role for each E2F member in specific malignancies, although not easy, is a challenging and continuously pursued task, especially in view of potential E2F targeted therapies. Therefore, several reviews are continuously trying to evaluate available data on E2F status in various malignancies. Such reviews have attempted to reach a consensus, often in the simplistic form of oncogenes or tumor suppressor genes for the E2Fs. However they frequently miss spatial and temporal alterations of these factors during tumor development, which should also be considered in conjunction with the status of the regulatory networks that these factors participate in. In the current ‘‘Letter to the Editor’’, we comment on the flaws, misinterpretations and omissions in one such review article published recently in the World Journal of Gastroenterology regarding the role of E2Fs in digestive system malignancies.

Overexpression of IQGAP1 in human pancreatic cancer

BACKGROUND

Pancreatic cancer is a highly aggressive malignant tumor with the lowest survival rate. A better understanding of the molecular mechanisms which contribute to pancreatic cancer occurrence and progression will aid in the development of new approaches to the early diagnosis, prevention, and treatment of this deadly disease. The scaffold protein IQGAP1 shows elevated levels in a variety of cancer types. Currently, we investigated whether or not IQGAP1 is also overexpressed in pancreatic cancer.

METHODS

IQGAP1 expression was examined in pancreatic cancer and normal tissues adjacent to cancerous tissues (adjacent tissues) by Western blotting and real-time RT-PCR as well as in paraffin sections of tissue microarray by immunohistochemistry. The correlations between IQGAP1 expression and various clinicopathological characteristics were analyzed.

RESULTS

Western blotting and real-time RT-PCR revealed that the levels of IQGAP1 protein and mRNA expression in pancreatic cancer tissues were significantly increased compared with adjacent tissues. Immunohistochemistry analysis on tissue microarray showed that IQGAP1 protein expression was significantly higher in pancreatic cancer (80.0%, 48/60) compared with adjacent tissues (18.3%, 11/60) (P<0.001). Moreover, overexpression of IQGAP1 was shown to be associated with the grades of tumor differentiation (P<0.05).

CONCLUSION

The overexpression of IQGAP1 may play an important role in pancreatic cancer occurrence and progression, and IQGAP1 may serve as a novel molecular target for the diagnosis and treatment of pancreatic cancer.

FGFR3 has tumor suppressor properties in cells with epithelial phenotype

Background

Due to frequent mutations in certain cancers, FGFR3 gene is considered as an oncogene. However, in some normal tissues, FGFR3 can limit cell growth and promote cell differentiation. Thus, FGFR3 action appears paradoxical.

Results

FGFR3 expression was forced in pancreatic cell lines. The receptor exerted dual effects: it suppressed tumor growth in pancreatic epithelial-like cells and had oncogenic properties in pancreatic mesenchymal-like cells. Distinct exclusive pathways were activated, STATs in epithelial-like cells and MAP Kinases in mesenchymal-like cells. Both FGFR3 splice variants had similar effects and used the same intracellular signaling. In human pancreatic carcinoma tissues, levels of FGFR3 dropped in tumors.

Conclusion

In tumors from epithelial origin, FGFR3 signal can limit tumor growth, explaining why the 4p16.3 locus bearing FGFR3 is frequently lost and why activating mutations of FGFR3 in benign or low grade tumors of epithelial origin are associated with good prognosis. The new hypothesis that FGFR3 can harbor both tumor suppressive and oncogenic properties is crucial in the context of targeted therapies involving specific tyrosine kinase inhibitors (TKIs). TKIs against FGFR3 might result in adverse effects if used in the wrong cell context.

E2F transcription factors and digestive system malignancies: How much do we know?

E2F family of transcription factors regulates various cellular functions related to cell cycle and apoptosis. Its individual members have traditionally been classified into activators and repressors, based on in vitro studies. However their contribution in human cancer is more complicated and difficult to predict. We review current knowledge on the expression of E2Fs in digestive system malignancies and its clinical implications for patient prognosis and treatment. E2F1, the most extensively studied member and the only one with prognostic value, exhibits a tumor-suppressing activity in esophageal, gastric and colorectal adenocarcinoma, and in hepatocellular carcinoma (HCC), whereas in pancreatic ductal adenocarcinoma and esophageal squamous cell carcinoma may function as a tumor-promoter. In the latter malignancies, E2F1 immunohistochemical expression has been correlated with higher tumor grade and worse patient survival, whereas in esophageal, gastric and colorectal adenocarcinomas is a marker of increased patient survival. E2F2 has only been studied in colorectal cancer, where its role is not considered significant. E2F4’s role in colorectal, gastric and hepatic carcinogenesis is tumor-promoting. E2F8 is strongly upregulated in human HCC, thus possibly contributing to hepatocarcinogenesis. Adenoviral transfer of E2F as gene therapy to sensitize pancreatic cancer cells for chemotherapeutic agents has been used in experimental studies. Other therapeutic strategies are yet to be developed, but it appears that targeted approaches using E2F-agonists or antagonists should take into account the tissue-dependent function of each E2F member. Further understanding of E2Fs’ contribution in cellular functions in vivo would help clarify their role in carcinogenesis.

Toll-like receptor 7 regulates pancreatic carcinogenesis in mice and humans

Pancreatic ductal adenocarcinoma is an aggressive cancer that interacts with stromal cells to produce a highly inflammatory tumor microenvironment that promotes tumor growth and invasiveness. The precise interplay between tumor and stroma remains poorly understood. TLRs mediate interactions between environmental stimuli and innate immunity and trigger proinflammatory signaling cascades. Our finding that TLR7 expression is upregulated in both epithelial and stromal compartments in human and murine pancreatic cancer led us to postulate that carcinogenesis is dependent on TLR7 signaling. In a mouse model of pancreatic cancer, TLR7 ligation vigorously accelerated tumor progression and induced loss of expression of PTEN, p16, and cyclin D1 and upregulation of p21, p27, p53, c-Myc, SHPTP1, TGF-β, PPARγ, and cyclin B1. Furthermore, TLR7 ligation induced STAT3 activation and interfaced with Notch as well as canonical NF-κB and MAP kinase pathways, but downregulated expression of Notch target genes. Moreover, blockade of TLR7 protected against carcinogenesis. Since pancreatic tumorigenesis requires stromal expansion, we proposed that TLR7 ligation modulates pancreatic cancer by driving stromal inflammation. Accordingly, we found that mice lacking TLR7 exclusively within their inflammatory cells were protected from neoplasia. These data suggest that targeting TLR7 holds promise for treatment of human pancreatic cancer.

Prevention of liver carcinogenesis by amarogentin through modulation of G1/S cell cycle check point and induction of apoptosis

Amarogentin, a secoiridoid glycoside, is an active component of the medicinal plant Swertia chirata. In this study, chemopreventive and chemotherapeutic actions of amarogentin were evaluated in a carbon tetrachloride (CCl(4))/N-nitrosodiethylamine (NDEA)-induced liver carcinogenesis mouse model system during continuous and posttreatment schedule. Better survival, no toxicity and increased body weight were noted in amarogentin-treated mice. Reduction in proliferation and increase in apoptosis frequency were evident in amarogentin-treated groups. In carcinogen control group moderate dysplasia, severe dysplasia and hepatocellular carcinoma were evident at 10th, 20th and 30th week, respectively. Amarogentin was found to prevent progression of liver carcinogenesis at mild dysplastic stage. Exposure to CCl(4)/NDEA resulted in upregulation of ppRb807/811, cyclinD1 and cdc25A at 10th week and additional activation of cMyc and mdm2 along with downregulation of LIMD1, p53 and p21 at 20th week. This was followed by activation of ppRb567 and downregulation of Rbsp3 at 30th week. Prevention of carcinogenesis by amarogentin in both groups might be due to cumulative upregulation of LIMD1, RBSP3, p16 and downregulation of cdc25A at 10th week along with activation of p53 and p21 and downregulation of ppRb807/811 and ppRb567 at 20th week, followed by downregulation of cyclinD1, cMyc and mdm2 at 30th week. During carcinogenesis reduction of apoptosis was evident since 20th week. However, amarogentin treatment could significantly induce apoptosis through upregulation of the Bax-Bcl2 ratio, activation of caspase-3 and poly ADP ribose polymerase cleavage. This is the first report of chemopreventive/therapeutic role of amarogentin during liver carcinogenesis through modulation of cell cycle and apoptosis.

Pancreatic cancer: pathobiology, treatment options, and drug delivery

Pancreatic cancer is the fourth leading cause of cancer-related deaths in the USA. The high mortality rate is partly due to lack of effective treatments. This review summarizes the pathobiology and current treatment options for pancreatic cancer. Moreover, the review discusses the opportunities of developing novel therapies for pancreatic cancer provided by the progress in understanding the genetic mutations, tumor microenvironment, cancer stem cells, and drug delivery.

Medical management of pancreatic adenocarcinoma

Pancreatic cancer is the fourth leading cause of cancer death in the United States. In 2008, an estimated 34,290 people died from pancreatic cancer and 37,680 new cases were diagnosed. Despite modern treatment, 90% of patients die within 1 year of diagnosis. Pancreatectomy is still the only potentially curative approach, but most patients have incurable disease by the time they are diagnosed, and fewer than 20% are candidates for surgery. In the present paper the English-language literature addressing the medical management in pancreatic cancer was reviewed. Based on these data we will discuss the role of currently used chemotherapy and target therapy in pancreatic cancer, as well as perspectives of the emerging strategies that are arising in order to improve the outcomes of this complex disease.

The targeted immunocytokine L19-IL2 efficiently inhibits the growth of orthotopic pancreatic cancer

PURPOSE

Effective control of pancreatic cancer has been hampered primarily by the lack of tumor specificity of current treatment modalities. The highly specific antibody-mediated delivery of therapeutic agents to the tumor microenvironment might overcome this problem. We therefore investigated the therapeutic efficacy of the targeted immunocytokine L19-Interleukin-2 (L19-IL2), consisting of the human single-chain Fv antibody L19, which is highly specific for the extradomain B (ED-B) of fibronectin, and the human cytokine IL-2, in pancreatic cancer.

EXPERIMENTAL DESIGN

Therapeutic effects of L19-IL-2, IL-2, and gemcitabine on tumor growth and metastasis were evaluated in orthotopic mouse models for pancreatic cancer. Immunohistochemistry was done to define ED-B expression, tumor necrosis, apoptosis, proliferation, and invasion of macrophages and natural killer (NK) cells. NK cells were depleted by i.v. injection of an anti-asialo-GM-1 antibody.

RESULTS

ED-B is selectively expressed in human pancreatic cancer and in primary tumors and metastases of the mouse models. L19-IL-2 therapy was clearly superior to untargeted IL-2 or gemcitabine and inhibited tumor growth and metastasis with remarkable long-term tumor control. Therapeutic effects were associated with the induction of extensive tumor necrosis and inhibition of tumor cell proliferation. Immunohistochemistry revealed an increase of macrophages and NK cells in the tumor tissue, suggesting immune-mediated mechanisms. The functional relevance of NK cells for the therapeutic effect of the targeted immunocytokine L19-IL-2 was confirmed by NK cell depletion, which completely abolished its antitumor efficacy.

CONCLUSIONS

These preclinical results strongly encourage the initiation of clinical studies using L19-IL-2 in pancreatic cancer.

Tumor suppressor p16INK4a--modulator of glycomic profile and galectin-1 expression to increase susceptibility to carbohydrate-dependent induction of anoikis in pancreatic carcinoma cells

Expression of the tumor suppressor p16(INK4a) after stable transfection can restore the susceptibility of epithelial tumor cells to anoikis. This property is linked to increases in the expression and cell-surface presence of the fibronectin receptor. Considering its glycan chains as pivotal signals, we assumed an effect of p16(INK4a) on glycosylation. To test this hypothesis for human Capan-1 pancreatic carcinoma cells, we combined microarray for selected glycosyltransferase genes with 2D chromatographic glycan profiling and plant lectin binding. Major differences between p16-positive and control cells were detected. They concerned expression of beta1,4-galactosyltransferases (down-regulation of beta1,4-galactosyltransferases-I/V and up-regulation of beta1,4-galactosyltransferase-IV) as well as decreased alpha2,3-sialylation of O-glycans and alpha2,6-sialylation of N-glycans. The changes are compatible with increased beta(1)-integrin maturation, subunit assembly and binding activity of the alpha(5)beta(1)-integrin. Of further functional relevance in line with our hypothesis, we revealed differential reactivity towards endogenous lectins, especially galectin-1. As a result of reduced sialylation, the cells' capacity to bind galectin-1 was enhanced. In parallel, the level of transcription of the galectin-1 gene increased conspicuously in p16(INK4a)-positive cells, and even figured prominently in a microarray on 1996 tumor-associated genes and in proteomic analysis. The cells therefore gain optimal responsiveness. The correlation between genetically modulated galectin-1 levels and anoikis rates in engineered transfectants inferred functional significance. To connect these findings to the fibronectin receptor, galectin-1 was shown to be co-immunoprecipitated. We conclude that p16(INK4a) orchestrates distinct aspects of glycosylation that are relevant for integrin maturation and reactivity to an endogenous effector as well as the effector's expression. This mechanism establishes a new aspect of p16(INK4a) functionality.

Capecitabine in carcinoma of the pancreas

Capecitabine is an oral prodrug of 5-fluorouracil, which is converted to 5-fluorouracil by three sequential enzymatic reactions. The final requisite enzyme, thymidine phosphorylase, is present at consistently higher levels in tumours compared with normal tissues, thereby suggesting that 5-fluorouracil that is delivered in this way may benefit from an element of tumour targeting and thus enhanced selectivity and better tolerability. Capecitabine has been shown to have single-agent activity in advanced carcinoma of the pancreas and to improve response rates and survival when administered in combination with gemcitabine compared with gemcitabine alone. This paper reviews the pharmacology and clinical data that are relevant to the use of capecitabine in pancreatic cancer.

The retinoblastoma protein is required for Ras-induced oncogenic transformation

Most human cancers involve either mutational activation of the Ras oncogenic pathway and/or inactivation of the retinoblastoma tumor suppressor (RB) pathway. Paradoxically, tumors that harbor Ras mutations almost invariably retain expression of a wild-type pRB protein. We explain this phenomenon by demonstrating that Ras-induced oncogenic transformation surprisingly depends on functional pRB protein. Cells lacking pRB are less susceptible to the oncogenic actions of H-RasV12 than wild-type cells and activated Ras has an inhibitory effect on the proliferation of pRB-deficient human tumor cells. In addition, depletion of pRB from Ras-transformed murine cells or human tumor cells that harbor Ras pathway mutations inhibits their proliferation and anchorage-independent growth. In sharp contrast to pRB-/- 3T3 cells, fibroblasts deficient in other pRB family members (p107 and p130) are more susceptible to Ras-mediated transformation than wild-type 3T3 cells. Moreover, loss of pRB in tumor cells harboring a Ras mutation results in increased expression of p107, and overexpression of p107 but not pRB strongly inhibits proliferation of these tumor cells. Together, these findings suggest that pRB and p107 have distinct roles in Ras-mediated transformation and suggest a novel tumor-suppressive role for p107 in the context of activated Ras.

Unique Gene Expression Profile Based on Pathologic Response in Epithelial Ovarian Cancer

Purpose

We investigated whether tumor tissue obtained at diagnosis expresses a specific gene profile that is predictive of findings at second-look surgery in patients with epithelial ovarian cancer (EOC).

Patients and Methods

Tumor tissue obtained at the time of diagnosis was profiled with oligonucleotide microarrays. Class prediction analysis was performed in a training set of 24 patients who had undergone a second-look procedure. The resultant predictive signature was then tested on an independent validation set comprised of 36 patients.

Results

A 93-gene signature referred to as the Chemotherapy Response Profile (CRP) was identified through its association with pathologic complete response. When applied to a separate validation set, the CRP distinguished between patients with unfavorable versus favorable overall survival (median 41 months v not yet reached, respectively, log-rank P = .007), with a median follow-up of 52 months. The signature maintained independent prognostic value in multivariate analysis, controlling for other known prognostic factors such as age, stage, grade, and debulking status. There was no genetic overlap between the CRP and our previously described Ovarian Cancer Prognostic Profile (OCPP), which demonstrated similar prognostic value. The combination of the CRP and OCPP yielded better prognostic discrimination then either profile alone. Genes present in the CRP include BAX, a proapoptotic protein previously associated with chemotherapy response in ovarian cancer.

Conclusion

Identification of a gene expression profile based on pathologic response in EOC provides independent prognostic information and offers potential insights into the mechanism of drug resistance. Efforts to identify a more tailored profile using selected genes from both the CRP and OCPP are underway.

The HTLV-I Tax oncoprotein targets the retinoblastoma protein for proteasomal degradation

Human T-cell leukemia virus type-I (HTLV-I), the etiologic agent of adult T-cell leukemia (ATL), is estimated to affect 10-20 million people worldwide. The transforming ability of HTLV-I has been largely attributed to the viral protein Tax, which modulates the activity of several well-known cell cycle regulators. An important cell cycle regulator, the retinoblastoma (Rb) protein, is often inactivated in many cancers including virally induced cancers. Upon examination of Rb status, we observed a decrease in Rb protein expression in HTLV-1-infected cell lines as well as in ex vivo ATL patient samples. Transient transfection assays indicated that decreased Rb protein levels were Tax dependent. Here, we demonstrate for the first time that Tax directly associates with Rb. This interaction was localized within the B pocket of Rb and the C-terminus of Tax (aa 245-353). Within the C-terminus of Tax, we have identified an LXCXE-like motif, that when mutated resulted in the loss of Tax/Rb interaction. Furthermore, through the use of proteasome inhibitors, such as MG-132, in vivo and proteasome degradation assays in vitro, we found that Tax destabilizes the hypo-phosphorylated (active) form of Rb via the proteasome pathway. Therefore, we propose a model whereby Tax targets Rb to the proteasome by acting as a molecular bridge bringing Rb into contact with the proteasome for degradation.

[Pathogenesis of the ductal pancreatic adenocarcinoma: implications for future therapies?]

Despite the advances in the knowledge of the molecular pathogenesis, pancreatic cancer remains a devastating disease with an 5-year survival rate below 5%. Current therapeutic approaches are not successful in respect to overall survival. There is a need to transfer the knowledge of basic science to new therapeutic strategies. This review describes the disturbed cell cycle control, anti-apoptotic mechanisms, the process of invasion and metastasis and angioneogenesis of pancreatic cancer cells. This knowledge will allow the development of novel therapeutic strategies for the future.

Orthotopic transplantation models of pancreatic adenocarcinoma derived from cell lines and primary tumors and displaying varying metastatic activity

OBJECTIVE

To establish a series of clinically relevant orthotopic transplantation models of human pancreatic adenocarcinoma from both cell lines and primary tumors under uniform experimental conditions.

METHODS

Ten pancreatic cancer cell lines and 12 primary tumors were orthotopically transplanted in SCID mice. The cell lines and xenografts were characterized for K-ras, BRAF, p53, p16, and DPC4 aberrations employing direct sequencing, immunohistochemistry, and Western blotting.

RESULTS

All xenografts showed high intrapancreatic tumorigenicity and extensive local tumor growth, and each showed a unique behavioral and genetic profile. Tumor characteristics were retained during serial passaging. The cell line-derived xenografts represented the entire expected range of histologic differentiation. Although the overall metastatic rate was moderate to high, the metastatic pattern varied; 4 cell lines showed a high metastatic rate to the liver. The primary tumor-derived xenografts retained their similarity to the corresponding original donor tumors with regard to histologic presentation and biologic behavior. K-ras, p53, p16, and DPC4 aberrations were revealed in 80%, 70%, 50%, and 40% of cell lines and 100%, 33%, 75%, and 58% of primary tumor derived xenografts, respectively. No BRAF mutations were present. The metastatic behavior of the xenografts was significantly associated with the degree of histologic differentiation, number of genes altered, and p53 status.

CONCLUSIONS

The new models reflected the wide range of patho-biological features and genetic alterations that characterize human pancreatic cancer and may be used collectively or selectively as a markedly improved in vivo tool for preclinical and molecular studies of pancreatic cancer.

A mouse model of uterine leiomyosarcoma

We are using an approach that is based on the cre/loxP recombination process and involves a binary system of Cre-producing and Cre-responding transgenic mice to achieve ubiquitous or tissue-specific expression of oncoproteins. To develop mouse models of tumorigenesis, Cre-producers are mated with responder animals carrying a dormant oncogene targeted into the 3' untranslated region of the locus encoding cytoplasmic beta-actin (actin cassette). Production of oncoprotein from a bicistronic message is accomplished in bitransgenic progeny by Cre-mediated excision of a segment flanked by loxP sites that is located upstream from the oncogenic sequence. Widespread Cre-dependent activation and expression of an actin-cassette transgene encoding the T antigens of the SV40 early region (SVER) commencing in embryos was compatible with normal development and did not impair viability. However, at approximately 3 months of age, all female animals developed massive uterine leiomyosarcomas, whereas practically all males exhibited enormously enlarged seminal vesicles because of pronounced hyperplasia of the smooth muscle layers. In addition, because of smooth muscle hyperproliferation, marked dilation of the gallbladder was observed in mice of both sexes. To begin exploring aberrant signaling events in the SVER-triggered tumorigenic pathways, we analyzed the expression profile of leiomyosarcomas by DNA microarray analysis.

The expression of retinoblastoma and Sp1 is increased by low concentrations of cyclin-dependent kinase inhibitors

We examined the effect of suboptimal concentrations of cyclin-dependent kinase inhibitors, which do not interfere with cell proliferation, on retinoblastoma expression in hamster (Chinese hamster ovary K1) and human (K562 and HeLa) cells. To achieve this, we used the chemical inhibitors roscovitine and olomoucine (which inhibit CDK2 preferentially), UCN-01 (which also inhibits CDK4/6) and p21 (as an intrinsic inhibitor). All chemical inhibitors and overexpression of p21 strongly induced retinoblastoma protein expression. UCN-01-mediated retinoblastoma expression was caused by an increase in both the levels of retinoblastoma mRNA and the stability of the protein. The expression of the transcription factor Sp1, a retinoblastoma-interacting protein, was also enhanced by all the cyclin-dependent kinase inhibitors tested. However, Sp1 expression was caused by an increase in the levels of Sp1 mRNA without modification in the stability of the protein. By using luciferase experiments, the transcriptional activation of both retinoblastoma and Sp1 promoters by UCN-01 was confirmed. Bisindolylmaleimide I, at concentrations causing a similar or higher inhibition of protein kinase C than UCN-01, provoked a lower activation of retinoblastoma and Sp1 expression. Finally, the effects of cyclin-dependent kinase inhibitors on dihydrofolate reductase gene expression were evaluated. Treatment with UCN-01 increased cellular dihydrofolate reductase mRNA levels, and dihydrofolate reductase enzymatic activity was enhanced by UCN-01, roscovitine, olomoucine and p21, in transient transfection experiments. These results support a mechanism for the self-regulation of retinoblastoma expression, and point to the need to establish the appropriate dose of cyclin-dependent kinase inhibitors as antiproliferative agents in anticancer treatments.

Activated signal transducer and activator of transcription 3 (STAT3) supports the malignant phenotype of human pancreatic cancer

BACKGROUND & AIMS

Constitutive activation of signal transducer and activator of transcription 3 (STAT3) has been implicated in regulation of growth and malignant transformation. We therefore analyzed the expression and biologic significance of STAT3 in human pancreatic cancer cells.

METHODS

Expression and activation of STAT3 were investigated by immunohistochemistry and immunoblotting. Functional inactivation of STAT3 was achieved by stable transfection of dominant-negative STAT3 constructs in 2 pancreatic cancer cell lines and confirmed by electrophoretic mobility shift assay and immunoblotting. Cell proliferation and tumorigenicity were evaluated by cell counting, colony formation in soft agar, and xenotransplantation in nude mice. STAT3-dependent cell cycle distribution was monitored by flow cytometry, immunoprecipitation, immunoblotting, and histone H1 and GST-Rb kinase assays.

RESULTS

Compared with nontransformed human pancreas, activated STAT3 is overexpressed in ductal carcinoma cells but not in ducts from chronic pancreatitis. Constitutive activation was also observed in all human pancreatic cancer cell lines examined. Functional inactivation of STAT3 resulted in significant inhibition of anchorage-dependent and -independent proliferation in vitro and reduced tumor growth in vivo. Cell cycle analysis showed a delay of G(1)/S-phase progression due to inhibition of cyclin-dependent kinase 2 activity based on increased expression of p21(WAF1) in vitro and in vivo. Blocking of the STAT3 upstream activator Janus kinase 2 by tyrphostin also resulted in growth arrest because of delayed G(1)/S-phase progression and increased expression of p21(WAF1).

CONCLUSIONS

On malignant transformation, activated STAT3 promotes cellular proliferation by acceleration of G(1)/S-phase progression and thereby contributes to the malignant phenotype of human pancreatic cancer.

Crystal structure of the retinoblastoma tumor suppressor protein bound to E2F and the molecular basis of its regulation

The retinoblastoma tumor suppressor protein (pRb) regulates the cell cycle, facilitates differentiation, and restrains apoptosis. Furthermore, dysfunctional pRb is thought to be involved in the development of most human malignancies. Many of the functions of pRb are mediated by its regulation of the E2F transcription factors. To understand the structural basis for this regulation, we have determined the crystal structure of a fragment of E2F in complex with the pocket domain of the tumor suppressor protein. The pRb pocket, comprising the A and B cyclin-like domains, is the major focus of tumourigenic mutations in the protein. The fragment of E2F used in our structural studies, residues 409-426 of E2F-1, represents the core of the pRb-binding region of the transcription factor. The structure shows that E2F binds at the interface of the A and B domains of the pocket making extensive interactions with conserved residues from both. We show by solution studies that a second site, probably contained within the "marked box" region of E2F, is responsible for additional interactions with the pRb pocket but is insufficient for complex formation on its own. In addition, we show that the interaction of the core binding fragment of E2F with pRb is inhibited by phosphorylation of the tumor suppressor protein by CDK2cyclin DE. Finally, our data reveal that the tight binding of the human papillomavirus E7 oncoprotein to pRb prevents subsequent interactions with the marked box region of E2F but not with its core binding region.

Restoring apoptosis in pancreatic cancer cells by targeting the nuclear factor-kappaB signaling pathway with the anti-epidermal growth factor antibody IMC-C225

We have previously demonstrated that RelA is constitutively activated in the majority of human pancreatic cancers and plays an important role in tumorigenesis and metastasis. The antiapoptotic gene bcl-xl is a downstream target of RelA, and regulation of bcl-xl transcription is mediated directly by the nuclear factor kappaB (NF-kappaB) binding sites present in the upstream promoter element of the bcl-xl gene. In this study we investigated the effects of inhibition of epidermal growth factor receptor (EGFR) signaling pathway with the anti-EGFR monoclonal antibody IMC-C225 on constitutive NF-kappaB activation and regulation of apoptosis-related genes in human pancreatic cancer cells. We found that activation of EGFR can be blocked with the anti-EGFR antibody IMC-C225 in the human pancreatic cancer cell line MDA Panc-28, leading to a marked decrease in constitutive NF-kappaB DNA binding activity. Our data also suggest that downregulation of NF-kappaB DNA binding activity by IMC-C225 leads to a decrease in bcl-xl and bfl-1 expression. Therefore, targeting the NF-kappaB signaling pathway with an anti-EGFR antibody may be one strategy to restore apoptosis in human pancreatic cancer cells, thereby enhancing the effect of chemotherapy and radiation therapy.