Mitogenic and antiapoptotic role of constitutive NF-kappaB/Rel activity in pancreatic cancer

Proteasome inhibition activates epidermal growth factor receptor (EGFR) and EGFR-independent mitogenic kinase signaling pathways in pancreatic cancer cells

PURPOSE

In the current study, we investigate the activation of antiapoptotic signaling pathways in response to proteasome inhibitor treatment in pancreatic cancer and evaluate the use of concomitant inhibition of these pathways to augment proteasome inhibitor treatment responses.

EXPERIMENTAL DESIGN

Pancreatic cancer cell lines and mouse flank xenografts were treated with proteasome inhibitor alone or in combination with chemotherapeutic compounds (gemcitabine, erlotinib, and bevacizumab), induction of apoptosis and effects on tumor growth were assessed. The effect of bortezomib (a first-generation proteasome inhibitor) and NPI-0052 (a second-generation proteasome inhibitor) treatment on key pancreatic mitogenic and antiapoptotic pathways [epidermal growth factor receptor, extracellular signal-regulated kinase, and phosphoinositide-3-kinase (PI3K)/AKT] was determined and the ability of inhibitors of these pathways to enhance the effects of proteasome inhibition was assessed in vitro and in vivo.

RESULTS

Our data showed that proteasome inhibitor treatment activates antiapoptotic and mitogenic signaling pathways (epidermal growth factor receptor, extracellular signal-regulated kinase, c-Jun-NH2-kinase, and PI3K/AKT) in pancreatic cancer. Additionally, we found that activation of these pathways impairs tumor response to proteasome inhibitor treatment and inhibition of the c-Jun-NH2-kinase and PI3K/AKT pathways increases the antitumor effects of proteasome inhibitor treatment.

CONCLUSION

These preclinical studies suggest that targeting proteasome inhibitor-induced antiapoptotic signaling pathways in combination with proteasome inhibition may augment treatment response in highly resistant solid organ malignancies. Further evaluation of these novel treatment combinations in clinical trials is warranted.

Apoptotic pathways in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common causes of cancer related death. Despite the advances in understanding of the molecular pathogenesis, pancreatic cancer remains a major unsolved health problem. Overall, the 5-year survival rate is less than 5% demonstrating the insufficiency of current therapies. Most cytotoxic therapies induce apoptosis and PDAC cells have evolved a plethora of molecular mechanisms to assure survival. We will present anti-apoptotic strategies working at the level of the death receptors, the mitochondria or involving the caspase inhibitors of the IAP family. Furthermore, the survival function of the phosphotidylinositol-3' kinase (PI3K)/AKT- and NF-kappaB-pathways are illustrated. A detailed molecular knowledge of the anti-apoptotic mechanisms of PDAC cells will help to improve therapies for this dismal disease and therapeutic strategies targeting the programmed cell death machinery are in early preclinical and clinical development.

ABINs inhibit EGF receptor-mediated NF-kappaB activation and growth of EGF receptor-overexpressing tumour cells

The epidermal growth factor receptor (EGFR) is frequently overexpressed in various tumours of epidermal origin and is held responsible for tumourigenicity and tumour persistence. Increased nuclear factor (NF)-kappaB activity has been suggested to be involved in the malignant behaviour of EGFR-overexpressing cells. However, the mechanisms that regulate EGF-induced NF-kappaB activation are still largely unknown. Here we show that EGF can induce NF-kappaB-dependent gene expression independently from IkappaBalpha degradation or p100 processing in EGFR-overexpressing HEK293T cells. Moreover, EGF-induced NF-kappaB activation could be inhibited by overexpression of ABINs, which were previously identified as intracellular inhibitors of tumour necrosis factor, interleukin-1 and lipopolysaccharide-induced NF-kappaB activation. Knockdown of ABIN-1 by RNA interference boosted the NF-kappaB response upon EGF stimulation. The C-terminal ubiquitin-binding domain containing region of ABINs was crucial and sufficient for NF-kappaB inhibition. Adenoviral gene transfer of ABINs reduced constitutive NF-kappaB activity as well as the proliferation of EGFR-overexpressing A431 and DU145 human carcinoma cells. Altogether, these results demonstrate an important role for an ABIN-sensitive non-classical NF-kappaB signalling pathway in the proliferation of EGFR-overexpressing tumour cells, and indicate a potential use for ABIN gene therapy in the treatment of cancer.

The role of nuclear factor kappaB in pancreatic cancer and the clinical applications of targeted therapy

Pancreatic cancer is one of the leading causes of cancer mortality in the United States. Current therapy for pancreatic cancer involves surgery, chemotherapy, and radiation therapy; however, the 5-year survival rate remains less than 5%. New strategies for treating pancreatic cancer include targeting intracellular signaling that provides survival advantages to cancer cells. One of these targets is the transcription factor nuclear factor (NF) kappaB, which is activated by a variety of mechanisms. Data demonstrate that increased NF-kappaB activity can promote growth and tumorigenesis, inhibit apoptosis, promote angiogenesis, promote invasion and metastasis, and promote chemoresistance in pancreatic cancer. This review explores the roles of NF-JB in these processes and examines the evidence that different NF-kappaB-inhibiting drugs can improve the treatment of pancreatic cancer.

BCL-2 functions as an activator of the AKT signaling pathway in pancreatic cancer

BCL-2 is the prototypic anti-apoptotic protein involved in the regulation of apoptosis. Overexpression of BCL-2 is common in pancreatic cancer and confers resistance to the apoptotic effect of chemo- and radiotherapy. Although these cellular effects of BCL-2 are traditionally related to pathways involving the mitochondrial membrane, we sought to investigate whether BCL-2 is involved in other signaling pathways regulating cell survival and focused on AKT. We examined the effect of overexpression of BCL-2 in the MIA-PaCa-2 human pancreatic cancer cell line on the function and subcellular location of AKT. We observed that the stable subclones of MIA-PaCa-2 overexpressing BCL-2 demonstrated increased activity of AKT as well as IKK (a downstream target of AKT), increasing the transcriptional activity of NF-kappaB. Using immunoprecipitation techniques, we observed co-immunoprecipitation of AKT and BCL-2. Immunocytochemistry demonstrated co-localization of BCL-2 and AKT, which was abrogated by treatment with HA14-1, a small molecule inhibitor of BH-3-mediated protein interaction by BCL-2. Furthermore, treatment with HA14-1 decreased phosphorylation of AKT and increased sensitivity to the apoptotic effect of the chemotherapeutic agent, paclitaxel. These results demonstrate an additional mechanism of regulation of cell survival mediated by BCL-2, namely through AKT activation, in the MIA-PaCa-2 pancreatic cancer cell line. Therefore, directed inhibition of BCL-2 may alter diverse pathways controlling cell survival and overcome the apoptotic resistance that is the hallmark of pancreatic cancer.

Immunohistochemical analysis of changes in signaling pathway activation downstream of growth factor receptors in pancreatic duct cell carcinogenesis

Background

The pathogenesis of pancreatic ductal adenocarcinoma (PDAC) involves multi-stage development of molecular aberrations affecting signaling pathways that regulate cancer growth and progression. This study was performed to gain a better understanding of the abnormal signaling that occurs in PDAC compared with normal duct epithelia.

Methods

We performed immunohistochemistry on a tissue microarray of 26 PDAC, 13 normal appearing adjacent pancreatic ductal epithelia, and 12 normal non-PDAC ducts. We compared the levels of 18 signaling proteins including growth factor receptors, tumor suppressors and 13 of their putative downstream phosphorylated (p-) signal transducers in PDAC to those in normal ductal epithelia.

Results

The overall profiles of signaling protein expression levels, activation states and sub-cellular distribution in PDAC cells were distinguishable from non-neoplastic ductal epithelia. The ERK pathway activation was correlated with high levels of ^S2448p-mTOR (100%, p = 0.05), ^T389p-S6K (100%, p = 0.02 and ^S235/236p-S6 (86%, p = 0.005). Additionally, ^T389p-S6K correlated with ^S727p-STAT3 (86%, p = 0.005). Advanced tumors with lymph node metastasis were characterized by high levels of ^S276p-NFκB (100%, p = 0.05) and ^S9p-GSK3β (100%, p = 0.05). High levels of PKBβ/AKT2, EGFR, as well as nuclear ^T202/Y204p-ERK and ^T180/Y182p-p38 were observed in normal ducts adjacent to PDAC compared with non-cancerous pancreas.

Conclusion

Multiple signaling proteins are activated in pancreatic duct cell carcinogenesis including those associated with the ERK, PKB/AKT, mTOR and STAT3 pathways. The ERK pathway activation appears also increased in duct epithelia adjacent to carcinoma, suggesting tumor micro-environmental effects.

NF-kappaB as a molecular target in the therapy of pancreatic carcinoma

The constitutive activation of the transcription factor nuclear-factor kappa B (NF-kappaB) is a hallmark of many highly malignant tumours such as the pancreatic ductal adenocarcinoma and accounts for profound chemoresistance. Inhibition of NF-kappaB activation has been shown to be a useful strategy for increasing the sensitivity towards cytostatic drug treatment in vitro and in vivo. Moreover, various pharmacological substances (e.g. thalidomide, bortezomib, sulphasalazine) have already entered clinical studies partially showing promising results for certain types of cancer. Further studies will be needed, in particular for pancreatic ductal adenocarcinoma, to evaluate the therapeutic efficacy of appropriate combinations of a NF-kappaB inhibitor and cytostatic drugs.

Cooperation of Ha-ras and Bcl-2 during multistep skin carcinogenesis

Nonmelanoma skin cancer (NMSC) is the most frequently diagnosed cancer in the United States. Deregulation of bcl-2 and ras family members is commonly observed in NMSC. It has been previously demonstrated that simultaneous bcl-2 and Ha-ras gene expression in keratinocytes results in disordered differentiation and resistance to cell death induced by ultraviolet (UV) radiation. It was, therefore, interest to assess the extent of cooperation between bcl-2 and Ha-ras during multistep skin carcinogenesis. The keratin 1 promoter was used to generate HK1.ras and HK1.bcl-2 transgenic mice, which were subsequently crossed to generate HK1.ras/bcl-2 double transgenic mice. The apoptotic index (AI) following UV-irradiation was significantly lower in HK1.bcl-2 and HKI.ras/bcl-2 epidermis compared to control littermates. Interestingly, the AI of HK1.ras/bcl-2 mice was significantly lower than even HK1.bcl-2 mice following UV-irradiation. To investigate the interaction of these oncogenes in skin tumorigenesis, a two-stage chemical carcinogenesis protocol was used to induce tumors. The individual contributions of Ha-ras and bcl-2 to papilloma latency, incidence, and growth rate in HK1.ras/bcl-2 double transgenic mice was marginally additive. Papillomas arising in HK1.ras transgenic mice exhibited the highest rate of apoptosis whereas papillomas arising in the HK1.ras/bcl-2 double transgenic mice exhibited rates of apoptosis that were significantly lower than papillomas arising in either control littermate or HK1.ras mice. Constitutive expression of either Ha-ras or bcl-2 exhibited similar rates of malignant tumor progression and they were not significantly different than control littermates. Importantly, when these two oncoproteins were coexpressed, a significant, and synergistic, increase in malignant transformation was observed.

Tumor transfected with CCL21 enhanced reactivity and apoptosis resistance of human monocyte-derived dendritic cells

Chemokine CCL21 can effectively attract CCR7(+) dendritic cells (DCs), however its role in this event is poorly understood. In this report, we investigated the effect of exogenous CCL21 expressed in breast cancer MCF-7 on human monocyte-derived DCs. CCL21-transfected MCF-7 stimulation prompted DC functions: migration, antigen-uptake and presentation. The stimulated DCs facilitated Th1 type cytokines production, perforin-forming CD8(+) T cell transformation and final T cell-associated clearance of MCF-7. Moreover, the MCF-7-resourced CCL21 protected DCs from apoptosis significantly, involving up-regulations of Bcl-2 expression and NF-kappaB activity, and reduction of caspase-3. This study provides evidence that tumor-derived CCL21 increases the presentation and apoptosis resistance of DCs, suggesting such a mechanism may be useful for the improvement of tumor cell immunogenicity and anti-tumor response.

Sonic hedgehog stimulates mouse embryonic stem cell proliferation by cooperation of Ca2+/protein kinase C and epidermal growth factor receptor as well as Gli1 activation

Hedgehog signaling has an essential role in the control of stem cell growth in embryonic tissues. Therefore, this study examined the effect of sonic hedgehog (Shh) on the self-renewal of mouse embryonic stem (ES) cells and its related mechanisms. Shh increased DNA synthesis blocked by the inhibition of the smoothened receptor. Shh required Gli1 activation to induce the increases in Notch/Hes-1 and Wnt/beta-catenin. Shh increased the intracellular calcium concentration ([Ca(2+)](i)) and protein kinase C (PKC) activity. We show that the Shh-induced increase in the Gli1 mRNA level requires [Ca(2+)](i) and PKC. Shh increased the phosphorylation of epidermal growth factor receptor (EGFR), which is blocked by the matrix metalloproteinase inhibitor. Subsequently, Shh increased the nuclear factor (NF)-kappaB p65 phosphorylation, which was inhibited by blocking PKC and EGFR tyrosine kinase. Shh also increased the level of the cell cycle regulatory proteins in a dose-dependent manner. However, Shh decreased the levels of the cyclin-dependent kinase inhibitory proteins. The effect of Shh on these proteins was inhibited by blocking PKC, EGFR, and NF-kappaB as well as transfection of Gli1 small interfering RNA (siRNA). Finally, Shh-induced progression of the G1/S-phase was blocked by the inhibition of PKC and EGFR tyrosine kinase. In conclusion, Shh stimulates mouse ES cell proliferation through Gli1 activation as well as Ca(2+)/PKC and EGFR. Disclosure of potential conflicts of interest is found at the end of this article.

Effects of the proteasome inhibitor bortezomib on gene expression profiles of pancreatic cancer cells

BACKGROUND

Pancreatic cancer remains a highly chemoresistant malignancy. Gemcitabine is a widely used clinical chemotherapeutic agent against locally advanced and metastatic pancreatic cancer. Proteasome inhibitor bortezomib has been shown to result in enhanced cytotoxicity and apoptosis when used alone or in combination with gemcitabine in pancreatic cancer cell lines.

MATERIALS AND METHODS

To determine the effect of bortezomib on gene expression profile of pancreatic adenocarcinoma cells with different sensitivity to gemcitabine, we used Affymetrix HG U133A 2.0 GeneChip (Santa Clara, CA) and measured changes induced by bortezomib in pancreatic cancer cell lines with high (BxPC-3) and low (PANC-1) sensitivity to gemcitabine, at time points 24 h. Selected genes were subsequently validated by quantitative real-time polymerase chain reaction.

RESULTS

Forty-four common genes in both PANC-1 and BxPC-3 cells were identified as up-regulated (>3-fold) induced by bortezomib analyzed by microarray, which are associated with multiple cytotoxic and cytoprotective effects. Bcl-2 was repressed by bortezomib in both PANC-1 and BxPC-3 cells, while no changes induced in either cell by bortezomib were disclosed in all five members of nuclear factor-kappa B family. Other interesting genes related to apoptosis or drug metabolism, such as TP53 and ABCB1 (mdr1), were not found differentially expressed in common.

CONCLUSIONS

Bortezomib exhibits antitumor effects toward pancreatic cancer in vitro and in vivo. Genes with divergent apoptotic effects are induced by bortezomib, which may become promising targets for pancreatic cancer treatment.

High expression of RelA/p65 is associated with activation of nuclear factor-kappaB-dependent signaling in pancreatic cancer and marks a patient population with poor prognosis

Activation of nuclear factor-kappaB (NF-kappaB) signaling was observed in pancreatic adenocarcinoma cell lines and tumours. However, information on the expression of RelA/p65, the major transcription activating NF-kappaB subunit, in these carcinomas and possible correlations thereof with NF-kappaB activation and patient survival is not available. To provide this missing translational link, we analysed expression of RelA/p65 in 82 pancreatic adenocarcinomas by immunohistochemistry. Moreover, we measured activation of the NF-kappaB pathway in 11 tumours by quantitative PCR for NF-kappaB target genes. We observed strong cytoplasmic or nuclear expression of RelA/p65 in 42 and 37 carcinomas, respectively. High cytoplasmic and nuclear expression of RelA/p65 had negative prognostic impact with 2-year survival rates for patients without cytoplasmic or nuclear RelA/p65 positivity of 41 and 40% and rates for patients with strong cytoplasmic or nuclear RelA/p65 expression of 22 and 20%, respectively. High RelA/p65 expression was correlated to increased expression of NF-kappaB target genes. The observation that high expression of RelA/p65 is correlated to an activation of the NF-kappaB pathway and indicates poor patient survival identifies a patient subgroup that might particularly benefit from NF-kappaB-inhibiting agents in the treatment of pancreatic cancer. Based on our findings, this subgroup could be identified by applying simple immunohistochemical techniques.

Phosphoinositide-3-kinase signaling controls S-phase kinase-associated protein 2 transcription via E2F1 in pancreatic ductal adenocarcinoma cells

The phosphoinositide-3-kinase (PI3K)/AKT signaling pathway controls fundamental processes of cancer cell biology like proliferation and cell survival. The PI3K/AKT pathway is activated in pancreatic ductal adenocarcinoma (PDAC) cells. The molecular mechanisms linking PI3K signaling to the cell cycle machinery in PDAC cells are not investigated in detail. Using the PI3K inhibitor Ly294002 as well as small interfering RNA targeting AKT1 expression, we show that PI3K controls the proliferation and G(1) phase progression of PDAC cells. Gene profiling revealed several important regulators of G(1)-S phase progression controlled by PI3K signaling like p21(Cip1), S-phase kinase-associated protein 2 (SKP2), CDC25a, cyclin A, cyclin D2, CDK2, and cyclin E. We show that the F-box protein SKP2, an oncogene up-regulated in PDAC, is transcriptionally regulated by the PI3K/AKT1 pathway in PDAC cells. At the molecular level, the control of the SKP2 gene by PI3K is due to the regulation of E2F1 binding to the proximal SKP2 gene promoter. The complex and profound connection of PI3K/AKT1 signaling to the cell cycle qualifies this pathway as a suitable target for therapeutic intervention in PDAC.

Targeting signal transduction in pancreatic cancer treatment

Pancreatic cancer is a lethal disease with a 5-year survival rate of 4%. The only opportunity for improved survival continues to be complete surgical resection for those with localized disease. Although chemotherapeutic options are limited for the few patients with resectable disease, this problem is even more magnified in the majority (85%) of patients with unresectable or metastastic disease. Therefore, there is an urgent need for improved therapeutic options. The recent success of inhibitors of signal transduction for the treatment of other cancers supports the need to identify and validate aberrant signaling pathways important for pancreatic tumor growth. This review focuses on the validation of specific signaling networks and the present status of inhibitors of these pathways as therapeutic approaches for pancreatic cancer treatment.

Curcumin potentiates antitumor activity of gemcitabine in an orthotopic model of pancreatic cancer through suppression of proliferation, angiogenesis, and inhibition of nuclear factor-kappaB-regulated gene products

Gemcitabine is currently the best treatment available for pancreatic cancer, but the disease develops resistance to the drug over time. Agents that can either enhance the effects of gemcitabine or overcome chemoresistance to the drug are needed for the treatment of pancreatic cancer. Curcumin, a component of turmeric (Curcuma longa), is one such agent that has been shown to suppress the transcription factor nuclear factor-kappaB (NF-kappaB), which is implicated in proliferation, survival, angiogenesis, and chemoresistance. In this study, we investigated whether curcumin can sensitize pancreatic cancer to gemcitabine in vitro and in vivo. In vitro, curcumin inhibited the proliferation of various pancreatic cancer cell lines, potentiated the apoptosis induced by gemcitabine, and inhibited constitutive NF-kappaB activation in the cells. In vivo, tumors from nude mice injected with pancreatic cancer cells and treated with a combination of curcumin and gemcitabine showed significant reductions in volume (P = 0.008 versus control; P = 0.036 versus gemcitabine alone), Ki-67 proliferation index (P = 0.030 versus control), NF-kappaB activation, and expression of NF-kappaB-regulated gene products (cyclin D1, c-myc, Bcl-2, Bcl-xL, cellular inhibitor of apoptosis protein-1, cyclooxygenase-2, matrix metalloproteinase, and vascular endothelial growth factor) compared with tumors from control mice treated with olive oil only. The combination treatment was also highly effective in suppressing angiogenesis as indicated by a decrease in CD31(+) microvessel density (P = 0.018 versus control). Overall, our results suggest that curcumin potentiates the antitumor effects of gemcitabine in pancreatic cancer by suppressing proliferation, angiogenesis, NF-kappaB, and NF-kappaB-regulated gene products.

Potentiation of the effect of erlotinib by genistein in pancreatic cancer: the role of Akt and nuclear factor-kappaB

The epidermal growth factor receptor (EGFR) is a target of new therapies in most nonhematologic cancers. EGFR blockade alone may not be sufficient for the control of growth and invasion of human pancreas cancer because of the independent activation of Akt and nuclear factor-kappaB (NF-kappaB). The expression of EGFR, Akt, and NF-kappaB was determined in six human pancreatic cancer cell lines. Selected cells for specific expression were treated with erlotinib, genistein, gemcitabine, or the combination. Growth inhibition was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and apoptosis was assayed by ELISA. EGFR, phosphorylated EGFR, phosphorylated Akt, and survivin expressions were determined by immunoblotting. Electrophoretic mobility shift assay was used to evaluate the DNA binding activity of NF-kappaB. Genistein significantly increased (P < 0.05) erlotinib-induced growth inhibition and apoptosis in BxPC-3, CAPAN-2, and AsPC-1 cells. In the BxPC-3 cell line, significant down-regulation of EGFR, phosphorylated Akt, NF-kappaB activation, and survivin was observed in the cells treated with the combination compared with the erlotinib-treated cells. In the HPAC and MIAPaCa cell line, no potentiation of the effects of erlotinib by genistein on cell growth or inhibition of the EGFR/Akt/NF-kappaB was observed. Genistein potentiated growth inhibition and apoptosis of the gemcitabine and erlotinib combination in COLO-357 cell line. Genistein potentiates the growth inhibition and apoptosis induced by erlotinib and gemcitabine in certain pancreatic cancer cells. Akt and NF-kappaB inhibition represents one of the mechanisms for the potentiation of erlotinib- and gemcitabine-induced cell death by genistein.

Synergistic Antitumor Activity of ZD6474, An Inhibitor of Vascular Endothelial Growth Factor Receptor and Epidermal Growth Factor Receptor Signaling, with Gemcitabine and Ionizing Radiation against Pancreatic Cancer

PURPOSE

Standard treatments have modest effect against pancreatic cancer, and current research focuses on agents targeting molecular pathways involved in tumor growth and angiogenesis. This study investigated the interactions between ZD6474, an inhibitor of tyrosine kinase activities of vascular endothelial growth factor receptor-2 and epidermal growth factor receptor (EGFR), gemcitabine, and ionizing radiation in human pancreatic cancer cells and analyzed the molecular mechanisms underlying this combination.

EXPERIMENTAL DESIGN

ZD6474, ionizing radiation, and gemcitabine, alone or in combination, were given in vitro to MIA PaCa-2, PANC-1, and Capan-1 cells and in vivo to MIA PaCa-2 tumor xenografts. The effects of treatments were studied by the evaluation of cytotoxicity, apoptosis, cell cycle, EGFR and Akt phosphorylation, modulation of gene expression of enzymes related to gemcitabine activity (deoxycytidine kinase and ribonucleotide reductase), as well as vascular endothelial growth factor immunohistochemistry and microvessel count.

RESULTS

In vitro, ZD6474 dose dependently inhibited cell growth, induced apoptosis, and synergistically enhanced the cytotoxic activity of gemcitabine and ionizing radiation. Moreover, ZD6474 inhibited phosphorylation of EGFR and Akt and triggered cell apoptosis. PCR analysis showed that ZD6474 increased the ratio between gene expression of deoxycytidine kinase and ribonucleotide reductase. In vivo, ZD6474 showed significant antitumor activity alone and in combination with radiotherapy and gemcitabine, and the combination of all three modalities enhanced MIA PaCA-2 tumor growth inhibition compared with gemcitabine alone.

CONCLUSIONS

ZD6474 decreases EGFR and Akt phosphorylation, enhances apoptosis, favorably modulates gene expression in cancer cells, and acts synergistically with gemcitabine and radiotherapy to inhibit tumor growth. These findings support the investigation of this combination in the clinical setting.

Pancreatic cancer: pathogenesis, prevention and treatment

Pancreatic cancer is the fourth leading cause of cancer death in the United States with a very low survival rate of 5 years. To better design new preventive and/or therapeutic strategies for the fight against pancreatic cancer, the knowledge of the pathogenesis of pancreatic cancer at the molecular level is very important. It has been known that the development and the progression of pancreatic cancer are caused by the activation of oncogenes, the inactivation of tumor suppressor genes, and the deregulation of many signaling pathways among which the EGFR, Akt, and NF-kappaB pathways appear to be most relevant. Therefore, the strategies targeting EGFR, Akt, NF-kappaB, and their downstream signaling could be promising for the prevention and/or treatment of pancreatic cancer. In this brief review, we will summarize the current knowledge regarding the pathogenesis, prevention, and treatment of pancreatic cancer.

Nuclear factor-κB and inhibitor of κB kinase pathways in oncogenic initiation and progression

Abundant data support a key role for the transcription factor nuclear factor-kappaB (NF-kappaB) signaling pathway in controlling the initiation and progression of human cancer. NF-kappaB and associated regulatory proteins such as IkappaB kinase (IKK) are activated downstream of many oncoproteins and there is much evidence for the activation of NF-kappaB-dependent target genes in a variety of solid tumors and hematologic malignancies. This review focuses on the mechanisms by which the NF-kappaB pathway is activated in cancer and on the oncogenic functions controlled by activated NF-kappaB. Additionally, the effects of NF-kappaB activation in tumors relative to cancer therapy are also discussed.

IKKalpha controls p52/RelB at the skp2 gene promoter to regulate G1- to S-phase progression

The IkappaB-inducing kinase (IKK) is composed of two catalytic subunits, IKKalpha and IKKbeta, and a regulatory subunit, IKKgamma. IKK-regulated signaling pathways are believed to promote the proliferation of normal cells as well as the aberrant proliferation of cancer cells. The molecular mechanisms linking the IKK signaling pathway components to the cell cycle machinery are not entirely understood. To study the function(s) of the catalytic subunits of the IKK complex, we used pancreatic cancer cells, with constitutive IKK activity. We show that the G1 phase of the cell cycle is specifically regulated by the IKKalpha subunit, which regulates the stability of the cyclin-dependent kinase inhibitor p27(Kip1). Increased p27(Kip1) protein levels following the transfection of IKKalpha-specific siRNAs are a result of the downregulation of the F-box protein S-phase kinase-associated protein 2 (skp2). Additionally, we demonstrate that IKKalpha signaling regulates the transcription of the skp2 gene by controlling the composition of a RelB-containing NF-kappaB complex. Together, this work defines a novel IKKalpha-regulated growth pathway involving the p52/RelB-dependent transcriptional regulation of the skp2 gene.

Genetics and biology of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer death in the United States with a median survival of <6 mo and a dismal 5-yr survival rate of 3%-5%. The cancer's lethal nature stems from its propensity to rapidly disseminate to the lymphatic system and distant organs. This aggressive biology and resistance to conventional and targeted therapeutic agents leads to a typical clinical presentation of incurable disease at the time of diagnosis. The well-defined serial histopathologic picture and accompanying molecular profiles of PDAC and its precursor lesions have provided the framework for emerging basic and translational research. Recent advances include insights into the cancer's cellular origins, high-resolution genomic profiles pointing to potential new therapeutic targets, and refined mouse models reflecting both the genetics and histopathologic evolution of human PDAC. This confluence of developments offers the opportunity for accelerated discovery and the future promise of improved treatment.

BMS-345541 targets inhibitor of kappaB kinase and induces apoptosis in melanoma: involvement of nuclear factor kappaB and mitochondria pathways

PURPOSE

Constitutive activation of inhibitor of kappaB kinase (IKK) confers melanoma resistance to apoptosis and chemotherapy. Whether IKK is able to serve as a therapeutic target in melanoma is unknown. We explored the possibility of exploiting IKK as a therapeutic target in melanoma by using BMS-345541, a novel compound with a highly selective IKKbeta inhibitory activity, to trigger melanoma cell apoptosis.

EXPERIMENTAL DESIGN

Three human melanoma cell lines (SK-MEL-5, Hs 294T, and A375), all of which have high constitutive IKK activities, served as in vitro and in vivo melanoma models for treatment with BMS-345541. Two known antitumor drugs (temozolomide and bortezomib) were used as parallel controls for evaluation of the therapeutic efficiency and toxicity of BMS-345541. The effects of BMS-345541 on nuclear factor kappaB (NF-kappaB) signaling and on the apoptosis machinery were investigated.

RESULTS

Inhibition of constitutive IKK activity by BMS-345541 resulted in the reduction of NF-kappaB activity, CXCL1 chemokine secretion by cultured melanoma cells and melanoma cell survival in vitro and in vivo. The effect of BMS-345541 on tumor cell growth was through mitochondria-mediated apoptosis, based on the release of apoptosis-inducing factor, dissipation of mitochondrial membrane potential, and reduced ratio of B cell lymphoma gene-2 (Bcl-2)/Bcl-associated X protein (Bax) in mitochondria. The BMS-345541 execution of apoptosis was apoptosis-inducing factor-dependent, but largely caspase-independent.

CONCLUSION

BMS-345541 down-regulation of IKK activity results in mitochondria-mediated apoptosis of tumor cells because the programmed cell death machinery in melanoma cells is highly regulated by NF-kappaB signaling. Therefore, IKK may serve as a potential target for melanoma therapy.

GADD45alpha is highly expressed in pancreatic ductal adenocarcinoma cells and required for tumor cell viability

Pancreatic ductal adenocarcinoma is one of the most common causes of cancer death in the western civilization. Recently, NF-kappaB has been shown to be activated in pancreatic ductal adenocarcinoma through constitutive activation of IkappaB kinase (IKK). Inhibition of NF-kappaB by a super-inhibitor of NF-kappaB--delta-N-IkappaBalpha--resulted in impaired proliferation and induction of apoptosis, suggesting an important role of NF-kappaB in pancreatic tumorigenesis. Downstream target genes of IkappaBalpha have not been elucidated in pancreatic ductal adenocarcinoma in detail. Using expression profiling by cDNA array analysis of pancreatic ductal adenocarcinoma cell lines stably transfected with super-IkappaBalpha, we identified GADD45alpha as a significant regulated gene. GADD45alpha is overexpressed in pancreatic ductal adenocarcinoma at the mRNA and protein level. Using RNAi we show that downregulation of GADD45alpha reduces proliferation and induces apoptosis in pancreatic cancer cells. These findings provide evidence that GADD45alpha contributes to pancreatic cancer cell proliferation and viability.

Nuclear factor-kB signaling pathway constitutively activated in esophageal squamous cell carcinoma cell lines and inhibition of growth of cells by small interfering RNA

Although constitutive nuclear factor (NF)-kappaB activation has been reported in many human tumors, the role of the NF-kappaB pathway in esophageal squamous cell carcinoma (ESCC) has not been known. In this study, NF-kappaB pathway in two ESCC cell lines was investigated using immunocytochemistry, Western blot and reverse transcription-polymerase chain reaction. The activation of NF-kappaB DNA binding was determined by electrophoretic mobility-shift assay. RNA interference was used to specifically inhibit the expression of p65. Growth of cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The results showed that p50, p65, IkappaBalpha p-IkappaBalpha and IkappaB kinase beta were expressed and mainly localized in the cytoplasm. Reverse transcription-polymerase chain reaction results showed the constitutive expressions of p50, p65 and IkappaBalpha mRNA in the two ESCC cell lines. Furthermore, the nuclear extracts revealed that p50 and p65 translocated to the nucleus had DNA-binding activity. Finally, small interfering RNA of p65 decreased the expression of p65, and the viability of cells transfected with p65 small interfering RNA was significantly suppressed at the same concentration of 5-fluorouracil (P < 0.05) compared to untransfected cells. The results of this study showed that there was the constitutively activated NF-kB signaling pathway in the ESCC cell lines. RNA interference targeting at p65 increased the sensitivity of the ESCC cell lines to 5-fluorouracil, suggesting that NF-kappaB might be a good target for cancer treatment.

Oncogenic PI3K deregulates transcription and translation

There have long been indications of a role for PI3K (phosphatidylinositol 3-kinase) in cancer pathogenesis. Experimental data document a requirement for deregulation of both transcription and translation in PI3K-mediated oncogenic transformation. The recent discoveries of cancer-specific mutations in PIK3CA, the gene that encodes the catalytic subunit p110alpha of PI3K, have heightened the interest in the oncogenic potential of this lipid kinase and have made p110alpha an ideal drug target.

Recent advances on the molecular mechanisms involved in pancreatic cancer progression and therapies

This review describes the recent advances in the molecular events involved in pancreatic cancer initiation, progression, and metastasis. Additionally, the importance of deregulated cellular signaling elements as potential targets for developing novel therapeutic strategies against incurable forms of pancreatic cancer is reported. The emphasis is on the critical functions gained by numerous growth factors and their receptors, such as epidermal growth factor receptor, hedgehog signaling, and proangiogenic agents such as vascular endothelial factor and interleukin-8 for the sustained growth, survival, and metastasis of pancreatic cancer cells. The molecular mechanisms associated with antitumoral properties and the clinical benefits of gemcitabine alone or in combination with other cytotoxic agents for the treatment of pancreatic cancer are discussed.

Induction of apoptosis in tumor-associated endothelial cells and therapy of orthotopic human pancreatic carcinoma in nude mice

Although gemcitabine has been accepted as the first-line chemotherapeutic reagent for advanced pancreatic cancer, improvement of response rate and survival is not sufficient and patients often develop resistance. We hypothesized that the inhibition of phosphorylation of epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor (VEGFR) on tumor cells and tumor-associated endothelial cells, combined with gemcitabine, would overcome the resistance to gemcitabine in orthotopic pancreatic tumor animal model. L3.6pl, human pancreatic cancer cells growing in the pancreas, and tumor-associated endothelial cells in microorgan environment highly expressed phosphorylated EGFR, VEGFR, and Akt, which regulates antiapoptotic mechanism. Oral administration of AEE788 (dual tyrosine kinase inhibitor against EGFR and VEGFR) inhibited the phosphorylation of EGFR, VEGFR, and Akt on tumor-associated endothelial cells as well as tumor cells. Although intraperitoneal (i.p.) injection of gemcitabine showed limited inhibitory effect on tumor growth, combination with AEE788 and gemcitabine produced nearly 95% inhibition of tumor growth in parallel with a high level of apoptosis on tumor cells and tumor-associated endothelial cells, and decreased microvascular density and proliferation rate. Collectively, these data indicate that dual inhibition of phosphorylation of EGFR and VEGFR, in combination with gemcitabine, produces apoptosis of tumor-associated endothelial cells and significantly suppresses human pancreatic cancer in nude mice.

Role of inflammation in pancreatic carcinogenesis and the implications for future therapy

BACKGROUND

The link between inflammation and pancreatic cancer has been observed for a number of gastrointestinal neoplasms. This review examines the role of inflammation in pancreatic carcinogenesis and how it can be utilised to develop new therapies against pancreatic cancer.

METHODS

A literature review of Pubmed, Medline and Web of Science databases was undertaken using the key words, pancreatic cancer, inflammation, inducible nitric oxide, interleukins, pro-inflammatory cytokines, cyclooxygenase-2, NF-kappa B, reactive oxygen species, DNA adducts, lipoxygenases, chemoprevention.

RESULTS

Epidemiological evidence and molecular studies both in vitro and in vivo all support the hypothesis that inflammation plays an important in the initiation and progression of pancreatic tumours.

CONCLUSION

Sustained damage caused by chronic inflammation may precede the onset of frank malignancy by a significant interval. As such, suppression of inflammatory changes and oxidative damage, may help delay or even prevent the inception of pancreatic neoplasia.

Constitutive activation of P I3 K-Akt and NF-kappaB during prostate cancer progression in autochthonous transgenic mouse model

BACKGROUND

Cancer progression is usually facilitated by independent growth signals that may lead to increased cell survival and evasion of apoptosis. Phosphatidylinositol 3'-OH kinase (P I3 K)-Akt and transcription factor NF-kappaB are important signaling molecules and key survival factors involved in the control of cell proliferation, apoptosis, and oncogenesis. Although P I3 K-Akt and NF-kappaB have been implicated in the development and progression of prostate cancer, expression of these molecules during progression of autochthonous disease has not been elucidated.

METHODS

Prostate cancer growth and progression in autochthonous transgenic adenocarcinoma of the mouse prostate (TRAMP) mice and male non-transgenic littermates were observed by magnetic resonance imaging (MRI). Expression patterns of P I3 K-Akt, NF-kappaB, I kappaB, and associated signaling molecules during different stages of cancer progression in these mice were examined by Western blot analysis, electrophoretic mobility shift assay (EMSA), enzyme-linked immunoabsorbent assay (ELISA), kinase assay, and immunohistochemistry.

RESULTS

Sequential MRI and gross analysis of prostate gland exhibited increasing prostate volume associated with the development and progression of prostatic adenocarcinoma in TRAMP mice, compared to male non-transgenic littermates. Differential protein expression of P I3 K, phosphorylated-Akt (Ser 473), I kappa Balpha and its phosphorylation, IKK kinase activity, NF-kappaB/p65, p50, DNA binding, and transcriptional-regulated genes, viz., Bc l2, cyclin D1, MMP-9, and VEGF were observed during prostate cancer progression in TRAMP mice, compared to male non-transgenic littermates. Expressions of these molecules were significantly increased during cancer progression observed at 24 and 32 weeks of age.

CONCLUSIONS

Differential expression pattern of P I3 K-Akt, NF-kappaB and I kappaB during prostate cancer progression in TRAMP mice suggest that these molecules represent potential molecular targets for prevention and/or therapeutic intervention.

Inhibitory effects of 12-O-tetradecanoylphorbol-13-acetate alone or in combination with all-trans retinoic acid on the growth of cultured human pancreas cancer cells and pancreas tumor xenografts in immunodeficient mice

Treatment of cultured PANC-1, MIA PaCa-2, and BxPC-3 human pancreatic adenocarcinoma cells with 0.1 to 1.6 nM 12-O-tetradecanoylphorbol-13-acetate (TPA) for 96 h inhibited the proliferation of these cells in a dose-dependent manner, and PANC-1 and MIA PaCa-2 cells were more sensitive to TPA than BxPC-3 cells. Inhibition of proliferation by TPA in PANC-1 cells was associated with an increase in the level of p21, but this was not observed in MIA PaCa-2 or BxPC-3 cells. The TPA-induced increase of p21 in PANC-1 cells was blocked by bisindolylmaleimide or rottlerin (inhibitors of protein kinase C). Studies in NCr-immunodeficient mice with well established PANC-1 tumor xenografts indicated that daily i.p. injections of TPA strongly inhibited tumor growth, increased the percentage of caspase-3-positive cells, and decreased the ratio of mitotic cells to caspase-3-positive cells in the tumors. Studies with BxPC-3 tumors in NCr mice receiving daily i.p. injections of vehicle, TPA, all-trans retinoic acid (ATRA), or a TPA/ATRA combination showed that TPA had an inhibitory effect on tumor growth, but treatment of the animals with the TPA/ATRA combination had a greater inhibitory effect on tumor growth than TPA alone. Treatment with the TPA/ATRA combination resulted in a substantially decreased ratio of the percentage of mitotic cells to the percentage of caspase-3-positive cells in the tumors compared with tumors from the vehicle-treated control animals. The inhibitory effects of TPA on tumor growth occurred at clinically achievable blood levels.

[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.

Cell death pathways in pancreatitis and pancreatic cancer

The understanding of the regulation of apoptosis and necrosis, the two principal cell death pathways, is becoming exceedingly important in investigations of the pathogenesis and treatment of pancreatitis and pancreatic cancer. For example, in acute pancreatitis significant amounts of pancreatic necrosis are associated with increased morbidity and mortality. Thus, determining the key steps regulating necrosis should provide insights into potential therapeutic strategies for improving outcome in these patients. On the other hand, in pancreatic cancer various survival mechanisms act to prevent cell death, resulting in promotion of tumor growth and metastasis. Resistance of pancreatic cancer to apoptosis is the key factor preventing responses to therapies. Investigations of the regulation of cell death mechanisms specific to pancreatic cancer should lead to improvements in our current therapies for this disease. The present review is designed to provide information about cell death pathways in pancreatitis and pancreatic cancer with reference to areas that need further investigation, as well as to provide measurement techniques adapted to pancreatic tissue and cells.

Inhibition of constitutively activated nuclear factor-κB radiosensitizes human melanoma cells

Melanoma tumors and cultured cell lines are relatively resistant to the cytotoxic effects of ionizing radiation, thereby limiting the use of radiotherapy for the clinical treatment of melanoma. New strategies for sensitizing melanoma cells therefore deserve examination. In an attempt to identify and target signaling pathways that contribute to radioresistance, we investigated the role of nuclear factor-κB (NF-κB), a transcription factor known to inhibit apoptosis induced by a variety of stimuli and promote radioresistance. Two human metastatic melanoma cell lines, A375 and MeWo, were used to examine the radiosensitizing effects of inhibitors of the NF-κB pathway. Nuclear extracts from these cell lines were tested for active NF-κB using the electrophoretic mobility shift assay. Both melanoma cell lines had constitutively activated NF-κB as observed by electrophoretic mobility shift assay. In an attempt to reverse NF-κB activity, cells were treated either with vehicle alone (DMSO) or with a proteasome inhibitor Z-Leu-Leu-Leu-H (MG132; 10 μmol/L for 2 hours prior to irradiation) that inhibited both constitutive and radiation-induced NF-κB activity. The clonogenic cell survival assay showed that pretreatment with MG132 enhanced tumor cell radiosensitivity with the survival factor at 2 Gy being reduced from 48 ± 0.8% and 48 ± 1.6% in vehicle-treated cells to 27.7 ± 0.32% and 34.3 ± 0.7% in MG132-treated MeWo and A375 cells, respectively. To test the role of NF-κB in radioresistance more directly, MeWo cells were stably transfected with a dominant-negative mutant IκBα construct, which led to the inhibition of both constitutive and radiation-induced NF-κB activity. A modest restoration of radiosensitivity was also observed in the stably transfected MeWo cells with survival factor at 2 Gy values being reduced from 47 ± 0.8% in parental MeWo cells to 32.9 ± 0.7% in stable transfectants. Because constitutively activated mitogen-activated protein kinase kinase (MEK) pathway has been shown to lead to activated NF-κB, we wanted to determine the relative contribution of activated MEK in the human melanoma cells. To test this, MeWo and A375 melanoma cells were exposed to the MEK inhibitor PD184352. Treatment with PD184352 partially reversed NF-κB activity but did not impart radiation sensitivity to these cells. Our results indicate that activated NF-κB may be one of the pathways responsible for the radioresistance of melanoma cells and that strategies for inhibiting its influence may be useful in restoring the radioresponse of melanomas.

Inflammatory mechanisms contributing to pancreatic cancer development

OBJECTIVE

Pancreatic cancer is the most deadly of all gastrointestinal (GI) malignancies, yet relatively little is known regarding mechanisms of tumor development including the role of inflammation.

SUMMARY BACKGROUND DATA

Chronic pancreatitis (CP) increases the risk of developing cancer by 10- to 20-fold; mediators of the chronic inflammatory process and the surrounding fibrotic stroma likely support a transformation to malignancy, yet the exact mechanisms remain undefined. The purpose of our present study was to determine potential inflammatory components in epithelial and stromal cells that may contribute to both CP and pancreatic cancers.

METHODS

Specimens of normal pancreas, CP, and pancreatic cancer were examined using laser-capture microdissection (LCM), gene array, and immunohistochemistry.

RESULTS

Gene array analysis from LCM-dissected tissues demonstrated: (i) increased expression of interleukin-8 (IL-8), an activator of the inflammatory factor nuclear factor-kappaB (NF-kappaB), and (ii) decreased expression of IkappaB (an inhibitor of NF-kappaB) in CP ductal cells compared with normal ducts. Compared with CP, cancers demonstrated: (i) increased expression of tumor related genes including S100A4, cyclin E1, and epidermal growth factor (EGF) receptor, and (ii) expression of matrix metalloproteinase 2, a pro-invasive factor for tumor cells, which was not present in the CP stroma. Increased staining of both the p50 NF-kappaB subunit and IKKalpha kinase (a protein that allows activation of NF-kappaB) was noted in CP and cancers.

CONCLUSIONS

Our results demonstrate that similar inflammatory components and downstream effectors are present in CP and pancreatic cancers. Importantly, these findings suggest that a common pathway for pancreatic cancer development may be through a chronic inflammatory process including stroma formation. These findings may lead to novel strategies for pancreatic cancer prophylaxis based on inhibition of inflammatory mediators.

To be, or not to be: NF-kappaB is the answer--role of Rel/NF-kappaB in the regulation of apoptosis

During their lifetime, cells encounter many life or death situations that challenge their very own existence. Their survival depends on the interplay within a complex yet precisely orchestrated network of proteins. The Rel/NF-kappaB signaling pathway and the transcription factors that it activates have emerged as critical regulators of the apoptotic response. These proteins are best known for the key roles that they play in normal immune and inflammatory responses, but they are also implicated in the control of cell proliferation, differentiation, apoptosis and oncogenesis. In recent years, there has been remarkable progress in understanding the pathways that activate the Rel/NF-kappaB factors and their role in the cell's decision to either fight or surrender to apoptotic challenge. Whereas NF-kappaB is most commonly involved in suppressing apoptosis by transactivating the expression of antiapoptotic genes, it can promote programmed cell death in response to certain death-inducing signals and in certain cell types. This review surveys our current understanding of the role of NF-kappaB in the apoptotic response and focuses on many developments since this topic was last reviewed in Oncogene 4 years ago. These recent findings shed new light on the activity of NF-kappaB as a critical regulator of apoptosis in the immune, hepatic, epidermal and nervous systems, on the mechanisms through which it operates and on its role in tissue development, homoeostasis and cancer.