Multiple and synergistic deregulations of apoptosis-controlling genes in pancreatic carcinoma cells

Padina boergesenii mediated synthesis of Se-ZnO bimetallic nanoparticles for effective anticancer activity

Introduction

Evaluating the anticancer property of Padina boergesenii mediated bimetallic nanoparticles.

Methods

The present study focuses on synthesizing Se-ZnO bimetallic nanoparticles from an aqueous algal extract of brown algae Padina boergesenii.Synthesized Se-ZnO NPs were characterized by UV, FTIR, SEM-EDS and HRTEM for confirmation along with the anticancer activity by MTT assay.

Results

The UV gave an absorbance peak at 342 and 370 nm, and the FTIR showed functional groups involved in synthesizing Se-ZnO NPs. The TEM micrographs indicated the crystalline nature and confirmed the size of the Se-ZnO NPs to be at an average size of 26.14 nm. Anticancer efficacy against the MCF-7 breast and HepG2 (hepatoblastoma) cell lines were also demonstrated, attaining an IC50 value of 67.9 µg and 74.9 µg/ml respectively, which caused 50% cell death.

Discussion

This work aims to highlight an effective method for delivering bioactive compounds extracted from brown algae and emphasize its future therapeutic prospects. The potential of Selenium-Zinc oxide nanoparticles is of great interest due to the biocompatibility and low toxicity aspects of selenium combined with the cost-effectiveness and sustainability of zinc metal. The presence of bioactive compounds contributed to the stability of the nanoparticles and acted as capping properties.

Endogenous TRAIL-R4 critically impacts apoptotic and non-apoptotic TRAIL-induced signaling in cancer cells

Binding of TRAIL to its death domain-containing receptors TRAIL-R1 and TRAIL-R2 can induce cell death and/or pro-inflammatory signaling. The importance of TRAIL and TRAIL-R1/R2 in tumor immune surveillance and cancer biology has meanwhile been well documented. In addition, TRAIL has been shown to preferentially kill tumor cells, raising hope for the development of targeted anti-cancer therapies. Apart from death-inducing receptors, TRAIL also binds to TRAIL-R3 and TRAIL-R4. Whereas TRAIL-R3 is lacking an intracellular domain entirely, TRAIL-R4 contains a truncated death domain but still a signaling-competent intracellular part. It is assumed that these receptors have anti-apoptotic, yet still not well understood regulatory functions.

To analyze the significance of the endogenous levels of TRAIL-R4 for TRAIL-induced signaling in cancer cells, we stably knocked down this receptor in Colo357 and MDA-MB-231 cells and analyzed the activation of apoptotic and non-apoptotic pathways in response to treatment with TRAIL.

We found that TRAIL-R4 affects a plethora of signaling pathways, partly in an opposite way. While knockdown of TRAIL-R4 in Colo357 strongly increased apoptosis and reduced clonogenic survival, it inhibited cell death and improved clonogenic survival of MDA-MB-231 cells after TRAIL treatment. Furthermore, TRAIL-R4 turned out to be an important regulator of the expression of a variety of anti-apoptotic proteins in MDA-MB-231 cells since TRAIL-R4-KD reduced the cellular levels of FLIPs, XIAP and cIAP2 but upregulated the levels of Bcl-xL. By inhibiting Bcl-xL with Navitoclax, we could finally show that this protein mainly accounts for the acquired resistance of MDA-MB-231 TRAIL-R4-KD cells to TRAIL-induced apoptosis. Analyses of non-apoptotic signaling pathways revealed that in both cell lines TRAIL-R4-KD resulted in a constitutively increased activity of AKT and ERK, while it reduced AKT activity after TRAIL treatment. Furthermore, TRAIL-R4-KD potentiated TRAIL-induced activation of ERK and p38 in Colo357, and NF-κB in MDA-MB-231 cells. Importantly, in both cell lines the activity of AKT, ERK, p38 and NF-κB after TRAIL treatment was higher in TRAIL-R4-KD cells than in respective control cells.

Thus, our data provide evidence for the important regulatory functions of endogenous TRAIL-R4 in cancer cells and improve our understanding of the very complex human TRAIL/TRAIL-R system.

Impact of Extracellular pH on Apoptotic and Non-Apoptotic TRAIL-Induced Signaling in Pancreatic Ductal Adenocarcinoma Cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an important mediator of tumor immune surveillance. In addition, its potential to kill cancer cells without harming healthy cells led to the development of TRAIL receptor agonists, which however did not show the desired effects in clinical trials. This is caused mainly by apoptosis resistance mechanisms operating in primary cancer cells. Meanwhile, it has been realized that in addition to cell death, TRAIL also induces non-apoptotic pro-inflammatory pathways that may enhance tumor malignancy. Due to its late detection and resistance to current therapeutic options, pancreatic ductal adenocarcinoma (PDAC) is still one of the deadliest types of cancer worldwide. A dysregulated pH microenvironment contributes to PDAC development, in which the cancer cells become highly dependent on to maintain their metabolism. The impact of extracellular pH (pHe) on TRAIL-induced signaling in PDAC cells is poorly understood so far. To close this gap, we analyzed the effects of acidic and alkaline pHe, both in short-term and long-term settings, on apoptotic and non-apoptotic TRAIL-induced signaling. We found that acidic and alkaline pHe differentially impact TRAIL-induced responses, and in addition, the duration of the pHe exposition also represents an important parameter. Thus, adaptation to acidic pHe increases TRAIL sensitivity in two different PDAC cell lines, Colo357 and Panc1, one already TRAIL-sensitive and the other TRAIL-resistant, respectively. However, the latter became highly TRAIL-sensitive only by concomitant inhibition of Bcl-xL. None of these effects was observed under other pHe conditions studied. Both TRAIL-induced non-apoptotic signaling pathways, as well as constitutively expressed anti-apoptotic proteins, were regulated by acidic pHe. Whereas the non-apoptotic pathways were differently affected in Colo357 than in Panc1 cells, the impact on the anti-apoptotic protein levels was similar in both cell lines. In Panc1 cells, adaptation to either acidic or alkaline pHe blocked the activation of the most of TRAIL-induced non-apoptotic pathways. Interestingly, under these conditions, significant downregulation of the plasma membrane levels of TRAIL-R1 and TRAIL-R2 was observed. Summing up, extracellular pH influences PDAC cells’ response to TRAIL with acidic pHe adaptation, showing the ability to strongly increase TRAIL sensitivity and in addition to inhibit TRAIL-induced pro-inflammatory signaling.

CD95L Inhibition Impacts Gemcitabine-Mediated Effects and Non-Apoptotic Signaling of TNF-α and TRAIL in Pancreatic Tumor Cells

Despite the potential apoptotic functions, the CD95/CD95L system can stimulate survival as well as pro-inflammatory signaling, particularly through the activation of NFκB. This holds true for the TNF/TNFR and the TRAIL/TRAILR systems. Thus, signaling pathways of these three death ligands converge, yet the specific impact of the CD95/CD95L system in this crosstalk has not been well studied. In this study, we show that gemcitabine stimulates the expression of pro-inflammatory cytokines, such as IL6 and IL8, under the influence of the CD95/CD95L system and the pharmacological inhibitor, sCD95Fc, substantially reduced the expression in two PDAC cell lines, PancTuI-luc and A818-4. The stem cell phenotype was reduced when induced upon gemcitabine as well by sCD95Fc. Moreover, TNF-α as well as TRAIL up-regulate the expression of CD95 and CD95L in both cell lines. Conversely, we detected a significant inhibitory effect of sCD95Fc on the expression of both IL8 and IL6 induced upon TNF-α and TRAIL stimulation. In vivo, CD95L inhibition reduced xeno-transplanted recurrent PDAC growth. Thus, our findings indicate that inhibition of CD95 signaling altered the chemotherapeutic effects of gemcitabine, not only by suppressing the pro-inflammatory responses that arose from the CD95L-positive tumor cells but also from the TNF-α and TRAIL signaling in a bi-lateral crosstalk manner.

TRAIL-receptor 2-a novel negative regulator of p53

TNF-related apoptosis-inducing ligand (TRAIL) receptor 2 (TRAIL-R2) can induce apoptosis in cancer cells upon crosslinking by TRAIL. However, TRAIL-R2 is highly expressed by many cancers suggesting pro-tumor functions. Indeed, TRAIL/TRAIL-R2 also activate pro-inflammatory pathways enhancing tumor cell invasion, migration, and proliferation. In addition, nuclear TRAIL-R2 (nTRAIL-R2) promotes malignancy by inhibiting miRNA let-7-maturation. Here, we show that TRAIL-R2 interacts with the tumor suppressor protein p53 in the nucleus, assigning a novel pro-tumor function to TRAIL-R2. Knockdown of TRAIL-R2 in p53 wild-type cells increases the half-life of p53 and the expression of its target genes, whereas its re-expression decreases p53 protein levels. Interestingly, TRAIL-R2 also interacts with promyelocytic leukemia protein (PML), a major regulator of p53 stability. PML-nuclear bodies are also the main sites of TRAIL-R2/p53 co-localization. Notably, knockdown or destruction of PML abolishes the TRAIL-R2-mediated regulation of p53 levels. In summary, our finding that nTRAIL-R2 facilitates p53 degradation and thereby negatively regulates p53 target gene expression provides insight into an oncogenic role of TRAIL-R2 in tumorigenesis that particularly manifests in p53 wild-type tumors.

Combating pancreatic cancer chemoresistance by triggering multiple cell death pathways

Pancreatic cancer is the fourth most common cause of cancer-associated death in western countries, where the incidence and number of deaths are increasing every year. Intrinsic or acquired resistance of tumor cells to chemotherapy agents is the major reason for failure of traditional cancer treatment. Several factors are implicated in this impressive resistance; however, of these, it is important to highlight the extensive cellular heterogeneity of these tumors. This heterogeneity is linked to a wide range of sensitivity that different clones in the same tumor display to chemotherapeutic agents. Accordingly, recent findings in this field have discovered new therapeutic targets in order to develop new combinatory treatments, as well as to induce several cell death pathways and reduce therapy-threshold and likelihood of future resistance. Accordingly, recent research has focused on targeting mitochondria, an organelle with key roles regulating cell death signaling pathways, such as apoptosis, necroptosis, autophagy, ferroptosis, or parthanatos. These findings - identifying new compounds, alone or in combination, that can target pancreatic ductal adenocarcinoma cell resistance - could be the key to future treatments.

Designed ferritin nanocages displaying trimeric TRAIL and tumor-targeting peptides confer superior anti-tumor efficacy

TRAIL is considered a promising target for cancer therapy because it mediates activation of the extrinsic apoptosis pathway in a tumor-specific manner by binding to and trimerizing its functional receptors, DR4 or DR5. Although recombinant human TRAIL has shown high potency and specificity for killing cancer cells in preclinical studies, it has failed in multiple clinical trials for several reasons, including a very short half-life mainly caused by instability of the monomeric form of TRAIL and rapid renal clearance of the off-targeted TRAIL. To overcome such obstacles, we developed a TRAIL-active trimer nanocage (TRAIL-ATNC) that presents the TRAIL ligand in its trimer-like conformation by connecting it to a triple helix sequence that links to the threefold axis of the ferritin nanocage. We also ligated the tumor-targeting peptide, IL4rP, to TRAIL-ATNC to enhance tumor targeting. The developed TRAIL-ATNCIL4rP showed enhanced agonistic activity compared with monomeric TRAIL. The in vivo serum half-life of TRAIL-ATNCIL4rP was ~ 16-times longer than that of native TRAIL. As a consequence of these properties, TRAIL-ATNCIL4rP exhibited efficacy as an anti-tumor agent in vivo against xenograft breast cancer as well as orthotopic pancreatic cancer models, highlighting the promise of this system for development as novel therapeutics against cancer.

Impact of p53 status on TRAIL-mediated apoptotic and non-apoptotic signaling in cancer cells

Due to their ability to preferentially induce cell death in tumor cells, while sparing healthy cells, TNF-related apoptosis-inducing ligand (TRAIL) and agonistic anti-TRAIL-R1 or anti-TRAIL-R2-specific antibodies are under clinical investigations for cancer-treatment. However, TRAIL-Rs may also induce signaling pathways, which result in malignant progression. TRAIL receptors are transcriptionally upregulated via wild-type p53 following radio- or chemotherapy. Nevertheless, the impact of p53 status on the expression and signaling of TRAIL-Rs is not fully understood. Therefore, we analyzed side by side apoptotic and non-apoptotic signaling induced by TRAIL or the agonistic TRAIL-R-specific antibodies Mapatumumab (anti-TRAIL-R1) and Lexatumumab (anti-TRAIL-R2) in the two isogenic colon carcinoma cell lines HCT116 p53^+/+ and p53^-/-. We found that HCT116 p53^+/+ cells were significantly more sensitive to TRAIL-R-triggering than p53^-/- cells. Similarly, A549 lung cancer cells expressing wild-type p53 were more sensitive to TRAIL-R-mediated cell death than their derivatives with knockdown of p53. Our data demonstrate that the contribution of p53 in regulating TRAIL-R-induced apoptosis does not correlate to the levels of TRAIL-Rs at the plasma membrane, but rather to p53-mediated upregulation of Bax, favouring the mitochondrial amplification loop. Consistently, stronger caspase-9 and caspase-3 activation as well as PARP-cleavage was observed following TRAIL-R-triggering in HCT116 p53^+/+ compared to HCT116 p53^-/- cells. Interestingly, HCT116 p53^+/+ cells showed also a more potent activation of non-canonical TRAIL-R-induced signal transduction pathways like JNK, p38 and ERK1/ERK2 than p53^-/- cells. Likewise, these cells induced IL-8 expression in response to TRAIL, Mapatumumab or Lexatumumab significantly stronger than p53^-/- cells. We obtained similar results in A549 cells with or without p53-knockdown and in the two isogenic colon cancer cell lines RKO p53^+/+ and p53^-/-. In both cellular systems, we could clearly demonstrate the potentiating effects of p53 on TRAIL-R-mediated IL-8 induction. In conclusion, we found that wild-type p53 increases TRAIL-R-mediated apoptosis but simultaneously augments non-apoptotic signaling.

Soluble TRAIL Armed Human MSC As Gene Therapy For Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is still one of the most aggressive adult cancers with an unacceptable prognosis. For this reason novel therapies accounting for PDAC peculiarities, such as the relevant stromal reaction, are urgently needed. Here adipose mesenchymal stromal/stem cells (AD-MSC) have been armed to constantly release a soluble trimeric and multimeric variant of the known anti-cancer TNF-related apoptosis-inducing ligand (sTRAIL). This cancer gene therapy strategy was in vitro challenged demonstrating that sTRAIL was thermally stable and able to induce apoptosis in the PDAC lines BxPC-3, MIA PaCa-2 and against primary PDAC cells. sTRAIL released by AD-MSC relocated into the tumor stroma was able to significantly counteract tumor growth in vivo with a significant reduction in tumor size, in cytokeratin-7+ cells and by an anti-angiogenic effect. In parallel, histology on PDAC specimens form patients (n = 19) was performed to investigate the levels of TRAIL DR4, DR5 and OPG receptors generating promising insights on the possible clinical translation of our approach. These results indicate that adipose MSC can very efficiently vehicle a novel TRAIL variant opening unexplored opportunities for PDAC treatment.

Green synthesis of selenium nanoparticles with extract of hawthorn fruit induced HepG2 cells apoptosis

CONTEXT

Selenium nanoparticles (SeNPs) have attracted worldwide attention due to their unique properties and potential bioactivities. Considering that hawthorn is both a traditional medicine and a common edible food, hawthorn fruit extract (HE) was chosen as a reductant to prepare SeNPs.

OBJECTIVE

SeNPs were synthesized by using an aqueous HE as a reductant and stabilizer. The antitumor activities and potential mechanisms of SeNPs were explored by using a series of cellular assays.

MATERIALS AND METHODS

The HE mediated SeNPs (HE-SeNPs) were examined using various characterisation methods. The cytotoxicity was measured against HepG2 cells after treated with 0, 5, 10 and 20 μg/mL of HE-SeNPs for 24 h. Annexin V-FITC/PI staining analysis was performed to observe the apoptosis of HepG2 cells. Additionally, mitochondrial membrane potential (MMP), intracellular reactive oxygen species (ROS) levels were evaluated. Finally, the protein expression levels of caspase-9 and Bcl-2 were identified by Western blot.

RESULTS

The mono-dispersed and stable SeNPs were prepared with an average size of 113 nm. HE-SeNPs showed obvious antitumor activities towards HepG2 cells with an IC₅₀ of 19.22 ± 5.3 μg/mL. Results from flow cytometry revealed that both early and total apoptosis rates increased after treating with HE-SeNPs. After cells were treated with various concentrations of HE-SeNPs (5, 10 and 20 μg/mL) for 24 h, the total rate increased to 7.3 ± 0.5, 9.7 ± 1.7 and 19.2 ± 1.6%, respectively. Meanwhile, treatment of HE-SeNPs up-regulated intracellular ROS levels and reduced the MMP. In addition, HE-SeNPs induced the up-regulation of caspase-9 and down-regulation of Bcl-2.

DISCUSSION AND CONCLUSIONS

HE-SeNPs induced intracellular oxidative stress and mitochondrial dysfunction to initiate HepG2 cell apoptosis through the mitochondrial pathway. Therefore, HE-SeNPs may be a candidate for further evaluation as a chemotherapeutic agent for human liver cancer.

The novel TRAIL-receptor agonist APG350 exerts superior therapeutic activity in pancreatic cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has raised attention as a novel anticancer therapeutic as it induces apoptosis preferentially in tumor cells. However, first-generation TRAIL-receptor agonists (TRAs), comprising recombinant TRAIL and agonistic receptor-specific antibodies, have not demonstrated anticancer activity in clinical studies. In fact, cancer cells are often resistant to conventional TRAs. Therefore, in addition to TRAIL-sensitizing strategies, next-generation TRAs with superior apoptotic activity are warranted. APG350 is a novel, highly potent TRAIL-receptor agonist with a hexavalent binding mode allowing the clustering of six TRAIL-receptors per drug molecule. Here we report on preclinical in vitro and in vivo studies testing the activity of APG350 on pancreatic ductal adenocarcinoma (PDAC) cells. We found that APG350 potently induced apoptosis of Colo357, PancTuI and Panc89 cells in vitro. In addition, APG350 treatment activated non-canonical TRAIL signaling pathways (MAPK, p38, JNK, ERK1/ERK2 and NF-κB) and induced the secretion of IL-8. Stable overexpression of Bcl-xL inhibited APG350-induced cell death and augmented activation of non-canonical pathways. Intriguingly, pre-treatment of Bcl-xL-overexpressing cells with the BH3-mimic Navitoclax restored their sensitivity to APG350. To study the effects of APG350 on PDAC cells in vivo, we applied two different orthotopic xenotransplantation mouse models, with and without primary tumor resection, representing adjuvant and palliative treatment regimes, respectively. APG350 treatment of established tumors (palliative treatment) significantly reduced tumor burden. These effects, however, were not seen in tumors with enforced overexpression of Bcl-xL. Upon primary tumor resection and subsequent APG350 treatment (adjuvant therapy), APG350 limited recurrent tumor growth and metastases. Importantly, therapeutic efficacy of APG350 treatment was more effective compared with treatment with soluble TRAIL in both models. In conclusion, APG350 represents a promising next-generation TRA for the treatment of PDAC. Moreover, our results suggest that combining APG350 with Navitoclax might be a succesfull strategy for cancers harboring mitochondrial apoptosis resistance.

Should We Keep Walking along the Trail for Pancreatic Cancer Treatment? Revisiting TNF-Related Apoptosis-Inducing Ligand for Anticancer Therapy

Despite recent advances in oncology, diagnosis, and therapy, treatment of pancreatic ductal adenocarcinoma (PDAC) is still exceedingly challenging. PDAC remains the fourth leading cause of cancer-related deaths worldwide. Poor prognosis is due to the aggressive growth behavior with early invasion and distant metastasis, chemoresistance, and a current lack of adequate screening methods for early detection. Consequently, novel therapeutic approaches are urgently needed. Many hopes for cancer treatment have been placed in the death ligand tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) since it was reported to induce apoptosis selectively in tumor cells in vitro and in vivo. TRAIL triggers apoptosis through binding of the trans-membrane death receptors TRAIL receptor 1 (TRAIL-R1) also death receptor 4 (DR4) and TRAIL receptor 2 (TRAIL-R2) also death receptor 5 (DR5) thereby inducing the formation of the death-inducing signaling complex (DISC) and activation of the apoptotic cascade. Unlike chemotherapeutics, TRAIL was shown to be able to induce apoptosis in a p53-independent manner, making TRAIL a promising anticancer approach for p53-mutated tumors. These cancer-selective traits of TRAIL led to the development of TRAIL-R agonists, categorized into either recombinant variants of TRAIL or agonistic antibodies against TRAIL-R1 or TRAIL-R2. However, clinical trials making use of these agonists in various tumor entities including pancreatic cancer were disappointing so far. This is thought to be caused by TRAIL resistance of numerous primary tumor cells, an insufficient agonistic activity of the drug candidates tested, and a lack of suitable biomarkers for patient stratification. Nevertheless, recently gained knowledge on the biology of the TRAIL-TRAIL-R system might now provide the chance to overcome intrinsic or acquired resistance against TRAIL and TRAIL-R agonists. In this review, we summarize the status quo of clinical studies involving TRAIL-R agonists for the treatment of pancreatic cancer and critically discuss the suitability of utilizing the TRAIL-TRAIL-R system for successful treatment.

Role of CCL20 mediated immune cell recruitment in NF-κB mediated TRAIL resistance of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) represents one of the deadliest cancers. From a clinical view, the transcription factor NF-κB is of particular importance, since this pathway confers apoptosis resistance and limits drug efficacy. Whereas the role of the most abundant NF-κB subunit p65/RelA in therapeutic resistance is well documented, only little knowledge of the RelA downstream targets and their functional relevance in TRAIL mediated apoptosis in PDAC is available. In the present study TRAIL resistant and sensitive PDAC cell lines were analyzed for differentially expressed RelA target genes, to define RelA downstream targets mediating TRAIL resistance. The most upregulated target gene was then further functionally characterized. Unbiased genome-wide expression analysis demonstrated that the chemokine CCL20 represents the strongest TRAIL inducible direct RelA target gene in resistant PDAC cells. Unexpectedly, targeting CCL20 by siRNA, blocking antibodies or by downregulation of the sole CCL20 receptor CCR6 had no effect on PDAC cell death or cancer cell migration, arguing against an autocrine role of CCL20 in PDAC. However, by using an ex vivo indirect co-culture system we were able to show that CCL20 acts paracrine to recruit immune cells. Importantly, CCL20-recruited immune cells further increase TRAIL resistance of CCL20-producing PDAC cells. In conclusion, our data show a functional role of a RelA-CCL20 pathway in PDAC TRAIL resistance. We demonstrate how the therapy-induced cross-talk of cancer cells with immune cells affects treatment responses, knowledge needed to tailor novel bi-specific treatments, which target tumor cell as well as immune cells.

Diagnostic value of selected markers and apoptotic pathways for pancreatic cancer

Pancreatic cancer occupies the fourth place as a cause of death from cancer, and the mortality rate is similar to the number of newly detected cases. Due to the late diagnosis, only 5-6% of patients with pancreatic cancer survive for five years. Given that early diagnosis is critical for improving patients' survival rates, there is an urgent need for the discovery and validation of new biomarkers with sufficient sensitivity and specificity to help diagnose pancreatic cancer early. Detection of serum tumor markers (CA19-9, CEA, CA125 and CA242) is conducive to the early diagnosis of pancreatic cancer. The combination of miR-16, miR-196a and CA19-9 plasma level was more effective, especially in early tumor screening. Furthermore, recent studies reported that mainly miR-21, miR-155 and miR-196 were dysregulated in IPMN (intraductal papillary mucinous neoplasms) and PanIN (pancreatic intraepithelial neoplasia) lesions, suggesting their usefulness as early biomarkers of these diseases. The reduced rate of apoptosis plays a crucial role in carcinogenesis, and it is one of the most important characteristics acquired by pancreatic cancer cells, which protects them from attack by the immune system and reduces the effectiveness of pharmacological treatment. This review summarizes the data concerning the clinical utility of selected biomarkers in pancreatic cancer patients. The review mainly focuses on the genetic aspects of signaling pathway disorders associated with apoptosis in the pathogenesis and diagnosis of pancreatic cancer.

The Targeted SMAC Mimetic SW IV-134 is a strong enhancer of standard chemotherapy in pancreatic cancer

Background

Pancreatic cancer is a lethal malignancy that frequently acquires resistance to conventional chemotherapies often associated with overexpression of inhibitors of apoptosis proteins (IAPs). We have recently described a novel means to deliver second mitochondria-derived activator of caspases (SMAC) mimetics selectively to cancer cells employing the sigma-2 ligand/receptor interaction. The intrinsic death pathway agonist SMAC offers an excellent opportunity to counteract the anti-apoptotic activity of IAPs. SMAC mimetics have been used to sensitize several cancer types to chemotherapeutic agents but cancer-selective delivery and appropriate cellular localization have not yet been considered. In our current study, we tested the ability of the sigma-2/SMAC drug conjugate SW IV-134 to sensitize pancreatic cancer cells to gemcitabine.

Methods

Using the targeted SMAC mimetic SW IV-134, inhibition of the X-linked inhibitor of apoptosis proteins (XIAP) was induced pharmacologically and its impact on cell viability was studied alone and in combination with gemcitabine. Pathway analyses were performed by assessing caspase activation, PARP cleavage and membrane blebbing (Annexin-V), key components of apoptotic cell death. Single-agent treatment regimens were compared with combination therapy in a preclinical mouse model of pancreatic cancer.

Results

The sensitizing effect of XIAP interference toward gemcitabine was confirmed via pharmacological intervention using our recently designed, targeted SMAC mimetic SW IV-134 across a wide range of commonly used pancreatic cancer cell lines at concentrations where the individual drugs showed only minimal activity. On a mechanistic level, we identified involvement of key components of the apoptosis machinery during cell death execution. Furthermore, combination therapy proved superior in decreasing the tumor burden and extending the lives of the animals in a preclinical mouse model of pancreatic cancer.

Conclusion

We believe that the strong sensitizing capacity of SW IV-134 in combination with clinically relevant doses of gemcitabine represents a promising treatment option that warrants clinical evaluation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0470-4) contains supplementary material, which is available to authorized users.

Negative control of TRAIL-R1 signaling by transforming growth factor β1 in pancreatic tumor cells involves Smad-dependent down regulation of TRAIL-R1

Pancreatic ductal adenocarcinoma (PDAC) is characterized by both, overexpression of transforming growth factor (TGF)β and resistance of the tumor cells to many apoptosis-inducing stimuli. The latter negatively impacts the outcome of therapeutic efforts and represents one important mechanism which tumor cells utilize to escape the immune surveillance. Since TGFβ acts as a tumor promoter in advanced tumor stages and suppression of apoptosis is a known driver of tumor progression, it is possible that TGFβ functions as a crucial determinant of tumor cell sensitivity to apoptosis in PDAC. Here, we have studied the impact of TGFβ on TNF-related apoptosis inducing ligand (TRAIL)-induced signaling in PDAC cells. In TGFβ-responsive Panc1 and Colo357 cells, TGFβ1 reduced total and plasma membrane-associated levels of TRAIL-R1 but not those of TRAIL-R2. Consistent with the known predominant role of TRAIL-R1 in TRAIL-mediated signaling in PDAC, TGFβ1 inhibited TRAIL-induced DISC formation and apoptosis as well as phosphorylation of MAPKs and IκBα. Similarly, it also reduced signaling of TRAIL-R1 following its specific activation with an agonistic antibody. In contrast, specific TRAIL-R2 signaling remained unchanged. The TGFβ1 effect on TRAIL-R1 expression was mimicked by ectopic expression of a kinase-active version of the TGFβ type I receptor ALK5 (ALK5-T204D) but not by ALK5 double mutant lacking the ability to phosphorylate Smad proteins (RImL45-T204D). Moreover, TGFβ regulation of TRAIL-R1 was absent in two PDAC cell lines lacking the Smad4 gene DPC4 and siRNA-mediated silencing of Smad4 in Smad4-positive Panc1 cells abolished the TGFβ-mediated decrease in TRAIL-R1 expression, together showing that ALK5/Smad4 signaling is crucial for TGFβ regulation of TRAIL-R1 expression. Our results suggest a novel tumor-promoting function of TGFβ1. By downregulating TRAIL-R1, TGFβ1 may not only promote tumor escape from immune surveillance but also negatively impact on TRAIL- or TRAIL-R1-based therapy regimens for treatment of PDAC.

A novel small-molecule IAP antagonist, AZD5582, draws Mcl-1 down-regulation for induction of apoptosis through targeting of cIAP1 and XIAP in human pancreatic cancer

Inhibitor of apoptosis proteins (IAPs) plays an important role in controlling cancer cell survival. IAPs have therefore attracted considerable attention as potential targets in anticancer therapy. In this study, we investigated the anti-tumor effect of AZD5582, a novel small-molecule IAP inhibitor, in human pancreatic cancer cells. Treating human pancreatic cancer cells with AZD5582 differentially induced apoptosis, dependent on the expression of p-Akt and p-XIAP. Moreover, the knockdown of endogenous Akt or XIAP via RNA interference in pancreatic cancer cells, which are resistant to AZD5582, resulted in increased sensitivity to AZD5582, whereas ectopically expressing Akt or XIAP led to resistance to AZD5582. Additionally, AZD5582 targeted cIAP1 to induce TNF-α-induced apoptosis. More importantly, AZD5582 induced a decrease of Mcl-1 protein, a member of the Bcl-2 family, but not that of Bcl-2 and Bcl-xL. Interestingly, ectopically expressing XIAP and cIAP1 inhibited the AZD5582-induced decrease of Mcl-1 protein, which suggests that AZD5582 elicits Mcl-1 decrease for apoptosis induction by targeting of XIAP and cIAP1. Taken together, these results indicate that sensitivity to AZD5582 is determined by p-Akt-inducible XIAP phosphorylation and by targeting cIAP1. Furthermore, Mcl-1 in pancreatic cancer may act as a potent marker to analyze the therapeutic effects of AZD5582.

Inhibition of Human Pancreatic Cancer Cell Proliferation by Devil's Club Oplopanax horridus and Its Polyacetylene Bioactive Compound

Devil's club Oplopanax horridus (DC) is a close relative of ginseng; its inner root and stem bark extract showed antiproliferation activity on human leukemia, ovarian, breast and colon cancer cells. We study here the effects of DC 70% ethanol extract alone, or in combination with cisplatin, gemcitabine, and paclitaxel on pancreatic endocrine HP62 and pancreatic ductal carcinoma PANC-1 and BxPC-3 cells. Antiproliferation activity assay, cell cycle analysis by flow cytometry, apoptosis-related markers by antibody array, and RT-PCR assay were used for this study. DC extract inhibited proliferation of HP62 with IC50 (50% inhibition concentration) at 0.037±0.002% (v/v), PANC-1 at 0.0058 ± 0.0004% and BxPC-3 at 0.021 ± 0.003%. DC at 0.0033% combined with 1 nM of paclitaxel showed inhibition synergy on PANC-1 cells with a combination index of 0.44. Apoptosis focused antibody array profile indicated upregulation of cytochrome C, claspin, cIAP-2 and HTRA2/Omi apoptosis-related markers in DC-treated HP62 and PANC-1. Our data suggest that DC acts through targeting the intrinsic mitochondrial apoptosis pathway in the pancreatic cancer cells. The high antiproliferation potency of DC on PANC-1 is potentially useful as an adjunct therapy for treating pancreatic cancer, which is known for developing resistance to conventional chemotherapeutics.

Pancreatic cancer-specific cell death induced in vivo by cytoplasmic-delivered polyinosine-polycytidylic acid

Polyinosine-polycytidylic acid [pIC] is a synthetic dsRNA that acts as an immune agonist of TLR3 and RLR to activate dendritic and natural killer cells that can kill tumor cells. pIC can also trigger apoptosis in pancreatic ductal adenocarcinoma cells (PDAC) but its mechanism of action is obscure. In this study, we investigated the potential therapeutic activity of a formulation of pIC with polyethylenimine ([pIC](PEI)) in PDAC and investigated its mechanism of action. [pIC](PEI) stimulated apoptosis in PDAC cells without affecting normal pancreatic epithelial cells. Mechanistically, [pIC](PEI) repressed XIAP and survivin expression and activated an immune response by inducing MDA-5, RIG-I, and NOXA. Phosphorylation of AKT was inhibited by [pIC](PEI) in PDAC, and this event was critical for stimulating apoptosis through XIAP and survivin degradation. In vivo administration of [pIC](PEI) inhibited tumor growth via AKT-mediated XIAP degradation in both subcutaneous and quasi-orthotopic models of PDAC. Taken together, these results offer a preclinical proof-of-concept for the evaluation of [pIC](PEI) as an immunochemotherapy to treat pancreatic cancer.

TRAIL-induced expression of uPA and IL-8 strongly enhanced by overexpression of TRAF2 and Bcl-xL in pancreatic ductal adenocarcinoma cells

BACKGROUND

The death ligand, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), induces apoptosis and non-apoptotic signaling in some tumor cells. The purpose of this study was to investigate the roles of the pro-apoptotic TRAIL receptors, TRAIL-R1 and TRAIL-R2, as well as Bcl-xL and TRAF2 in TRAIL-induced expression of the pro-inflammatory cytokine IL-8 and the invasion-promoting protein urokinase (uPA) in pancreatic ductal adenocarcinoma (PDAC) cells.

METHODS

Colo357wt, Colo357/TRAF2, Colo357/Bcl-xL, Panc89 and PancTuI cells were stimulated with TRAIL and uPA and IL-8 expression was detected using real-time PCR. Antagonistic, receptor-specific antibodies were used to investigate the effects of TRAIL-R1 or TRAIL-R2 inhibition.

RESULTS

Dose-dependent increases in uPA and IL-8 expression were detected following TRAIL stimulation in PDAC cells. These effects were inhibited when TRAIL-R1 but not TRAIL-R2 was blocked. Overexpression of TRAF2 or Bcl-xL strongly increased TRAIL-mediated upregulation of uPA and IL-8.

CONCLUSIONS

In PDAC cells, TRAIL strongly induced uPA and IL-8 via TRAIL-R1. This response was further enhanced in cells overexpressing TRAF2 and Bcl-xL. Therefore, inhibition of the non-apoptotic "side-effects" of TRAIL treatments by inactivation of TRAF2 and Bcl-xL might represent additional relevant strategies for the treatment of pancreatic cancer.

Double inhibition of NF-κB and XIAP via RNAi enhances the sensitivity of pancreatic cancer cells to gemcitabine

The majority of patients with pancreatic cancer are resistant to gemcitabine. One of the mechanisms involved is the anti-apoptotic ability of these cells. The median lethal dose (LD50) of gemcitabine for PANC-1 cells was higher than that for Mia PaCa-2 cells and the former had higher nuclear factor-κB (NF-κB) and X-linked inhibitor of apoptosis protein (XIAP) levels. NF-κB contributes to the inhibition of apoptosis by the downregulation of downstream genes, such as XIAP and Bcl-2 and it confers chemoresistance. The two cell lines were infected with NF-κB p65 small interfering RNA (siRNA). p65 protein was effectively downregulated accompanied by the downregulation of XIAP protein. The combination treatment with gemcitabine and p65 siRNA increased the apoptotic rates in both cell lines; however, this was not sufficient. XIAP is involved in apoptosis to a greater extent compated to Bcl-2. XIAP may serve as another factor affecting the sufficiency of chemotherapy. XIAP siRNA was designed to knockdown XIAP. Mia PaCa-2 and PANC-1 cells were co-infected with XIAP siRNA and p65 siRNA. XIAP and p65 proteins were effectively downregulated and the gemcitabine-induced apoptotic rates were significantly increased. These results suggest that XIAP and NF-κB are two important factors conferring the chemoresistance of pancreatic cancer cells, and that their downregulation via RNAi effectively enhances the chemosensitivity of pancreatic cancer cells to gemcitabine.

Relationship between aberrant methylation of FAS promoter and biological behavior of bladder urothelial carcinoma

This study examined the promoter methylation of APO-1/CD95 (Fas) gene in bladder urothelial carcinoma and analyzed the relationship between the Fas promoter methylation and the biological behavior of bladder cancer. Promoter methylation of Fas gene was detected by methylation-specific PCR (MSP) in 4 bladder cancer cell lines, 50 human bladder urothelial carcinoma samples and l0 normal bladder tissue samples. Correlation of the aberrant methylation of Fas promoter with the clinicopathological parameters was statistically analyzed. The results showed that Fas was down-regulated at both mRNA and protein level in bladder cancer cell lines and tissue samples of bladder urothelial carcinoma. The positive rate of Fas protein expression in bladder urothelial carcinoma was 34.0% (17/50), significantly lower than that in normal bladder tissues (70.0%, 7/10) (P<0.01). Fas promoter methylation was detected, and the positive rate of Fas promoter methylation in bladder urothelial carcinoma was 42.0% (21/50), which was obviously higher than that in normal bladder tissues (0.0%, 0/10) (P<0.01). The aberrant methylation of Fas promoter was reversely correlated with Fas protein expression (P<0.05). Furthermore, the positive rates of Fas promoter methylation in high-grade and low-grade bladder urothelial carcinoma were 73.3% (11/15) and 34.2% (12/35), respectively, with significant difference shown (P<0.05). No statistical significance was found in the Fas promoter methylation among different clinical stages of bladder cancer. It was concluded that Fas promoter hypermethylation plays an important role in the pathogenesis of bladder urothelial carcinoma and may serve as a prognostic indicator of bladder urothelial carcinoma.

Omeprazole inhibits proliferation and modulates autophagy in pancreatic cancer cells

BACKGROUND

Omeprazole has recently been described as a modulator of tumour chemoresistance, although its underlying molecular mechanisms remain controversial. Since pancreatic tumours are highly chemoresistant, a logical step would be to investigate the pharmacodynamic, morphological and biochemical effects of omeprazole on pancreatic cancer cell lines.

METHODOLOGY/PRINCIPAL FINDINGS

Dose-effect curves of omeprazole, pantoprazole, gemcitabine, 5-fluorouracil and the combinations of omeprazole and 5-fluorouracil or gemcitabine were generated for the pancreatic cancer cell lines MiaPaCa-2, ASPC-1, Colo357, PancTu-1, Panc1 and Panc89. They revealed that omeprazole inhibited proliferation at probably non-toxic concentrations and reversed the hormesis phenomena of 5-fluorouracil. Electron microscopy showed that omeprazole led to accumulation of phagophores and early autophagosomes in ASPC-1 and MiaPaCa-2 cells. Signal changes indicating inhibited proliferation and programmed cell death were found by proton NMR spectroscopy of both cell lines when treated with omeprazole which was identified intracellularly. Omeprazole modulates the lysosomal transport pathway as shown by Western blot analysis of the expression of LAMP-1, Cathepsin-D and β-COP in lysosome- and Golgi complex containing cell fractions. Acridine orange staining revealed that the pump function of the vATPase was not specifically inhibited by omeprazole. Gene expression of the autophagy-related LC3 gene as well as of Bad, Mdr-1, Atg12 and the vATPase was analysed after treatment of cells with 5-fluorouracil and omeprazole and confirmed the above mentioned results.

CONCLUSIONS

We hypothesise that omeprazole interacts with the regulatory functions of the vATPase without inhibiting its pump function. A modulation of the lysosomal transport pathway and autophagy is caused in pancreatic cancer cells leading to programmed cell death. This may circumvent common resistance mechanisms of pancreatic cancer. Since omeprazole use has already been established in clinical practice these results could lead to new clinical applications.

Targeting apoptosis signaling in pancreatic cancer

The ability to escape apoptosis or programmed cell death is a hallmark of human cancers, for example pancreatic cancer. This can promote tumorigenesis, since too little cell death by apoptosis disturbs tissue homeostasis. Additionally, defective apoptosis signaling is the underlying cause of failure to respond to current treatment approaches, since therapy-mediated antitumor activity requires the intactness of apoptosis signaling pathways in cancer cells. Thus, the elucidation of defects in the regulation of apoptosis in pancreatic carcinoma can result in the identification of novel targets for therapeutic interference and for exploitation for cancer drug discovery.

Simultaneous gene silencing of Bcl-2, XIAP and Survivin re-sensitizes pancreatic cancer cells towards apoptosis

BACKGROUND

Pancreatic ductal adenocarcinoma shows a distinct apoptosis resistance, which contributes significantly to the aggressive nature of this tumor and constrains the effectiveness of new therapeutic strategies. Apoptosis resistance is determined by the net balance of the cells pro-and anti-apoptotic "control mechanisms". Numerous dysregulated anti-apoptotic genes have been identified in pancreatic cancer and seem to contribute to the high anti-apoptotic buffering capacity. We aimed to compare the benefit of simultaneous gene silencing (SGS) of several candidate genes with conventional gene silencing of single genes.

METHODS

From literature search we identified the anti-apoptotic genes XIAP, Survivin and Bcl-2 as commonly upregulated in pancreatic cancer. We performed SGS and silencing of single candidate genes using siRNA molecules in two pancreatic cancer cell lines. Effectiveness of SGS was assessed by qRT-PCR and western blotting. Apoptosis induction was measured by flow cytometry and caspase activation.

RESULTS

Simultaneous gene silencing reduced expression of the three target genes effectively. Compared to silencing of a single target or control, SGS of these genes resulted in a significant higher induction of apoptosis in pancreatic cancer cells.

CONCLUSIONS

In the present study we performed a subliminal silencing of different anti-apoptotic target genes simultaneously. Compared to silencing of single target genes, SGS had a significant higher impact on apoptosis induction in pancreatic cancer cells. Thereby, we give further evidence for the concept of an anti-apoptotic buffering capacity of pancreatic cancer cells.

Analogs of vitamin E epitomized by alpha-tocopheryl succinate for pancreatic cancer treatment: in vitro results induce caution for in vivo applications

OBJECTIVES

alpha-Tocopheryl succinate (alpha-TOS) is thought to be toxic only for cancer cells. We ascertained in vitro alpha-TOS effects on pancreatic cancer (PC) and normal cell growth and verified whether the combination of nontoxic alpha-TOS and 5-fluorouracil (5-FU) doses causes cancer cell death and whether alpha-TOS effects are mediated by the proapoptotic proteins Bax/Bak and/or SMAD4/DPC4 status.

METHODS

Five PC cell lines, myoblasts, normal monocytes, wild-type (WT) and Bax/Bak double knockout mouse embryonic fibroblast (MEF) cells, and permanently SMAD4/DPC4-transfected PSN1 cells were cultured in 1% and 10% fetal calf serums (FCSs), without or with alpha-TOS (5-500 micromol/L). Nontoxic 5-FU (0.0001 mmol/L) and alpha-TOS alone or in combination were also evaluated.

RESULTS

Only PSN1 PC cell line, which had SMAD4/DPC4 homozygous deletion, was sensitive to nontoxic alpha-TOS doses (5 micromol/L in 1% FCS and 50 micromol/L in 10% FCS). A 20-micromol/L alpha-TOS inhibited MEF-WT, not MEF-double knockout growth. Only PSN1 cells were sensitive to nontoxic 5-FU and alpha-TOS combination. SMAD4/DPC4 transfection restored PSN1 resistance to the effects of combined 5-FU and alpha-TOS effects.

CONCLUSIONS

Only a minority of PC cells are sensitive to the antiproliferative effects of alpha-TOS, any sensitivity appearing to be correlated with SMAD4/DPC4 homozygous deletion and Bax/Bak expression.

Molecular mechanism of pancreatic cancer--understanding proliferation, invasion, and metastasis

INTRODUCTION

The purpose of this review is to highlight the molecular mechanisms leading to the development and progression of pancreatic ductal adenocarcinoma (PDAC) with particular emphasis on tumor cell proliferation, local invasion, and metastasis. Recent advances in the field of PDAC biology have shed light on the molecular events that trigger PDAC initiation and maintenance.

RESULTS

It is now clear that apart from the genetic alterations within the tumor cells, interactions of the tumor with its environment are necessary for proliferation and invasion. Interestingly, a number of developmental signaling pathways are reactivated in PDAC. Progress has also been made in the understanding of the molecular events that govern the process of metastasis.

CONCLUSION

Although our understanding of the mechanisms underlying PDAC pathobiology are more advanced than ever, little progress has been made in the clinical treatment of PDAC, and successful bench-to-bedside transfer of knowledge to boost new treatment options is still unsatisfying.

TRAIL signaling is mediated by DR4 in pancreatic tumor cells despite the expression of functional DR5

Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) and agonistic anti-DR4/TRAIL-R1 and anti-DR5/TRAIL-R2 antibodies are currently under clinical investigation for treatment of different malignancies. TRAIL activates DR4 and DR5 and thereby triggers apoptotic and non-apoptotic signaling pathways, but possible different roles of DR4 or DR5 in these responses has poorly been addressed so far. In the present work, we analyzed cell viability, DISC formation as well as IL-8 and NF-kappaB activation side by side in responses to TRAIL and agonistic antibodies against DR4 (mapatumumab) and against DR5 (lexatumumab) in pancreatic ductal adenocarcinoma cells. We found that all three reagents are able to activate cell death and pro-inflammatory signaling. Death-inducing signaling complex (DISC) analysis revealed that mapatumumab and lexatumumab induce formation of homocomplexes of either DR4 or DR5, whereas TRAIL additionally stimulated the formation of heterocomplexes of both receptors. Notably, blocking of receptors using DR4- and DR5-specific Fab fragments indicated that TRAIL exerted its function predominantly via DR4. Interestingly, inhibition of PKC by Goe6983 enabled DR5 to trigger apoptotic signaling in response to TRAIL and also strongly enhanced lexatumumab-mediated cell death. Our results suggest the existence of mechanisms that silence DR5 for TRAIL- but not for agonistic-antibody treatment.

Apoptosis pathways and their therapeutic exploitation in pancreatic cancer

Resistance to apoptosis (programmed cell death) is a characteristic feature of human malignancies including pancreatic cancer, which is one of the leading causes of cancer deaths in the western world. Defects in this intrinsic cell death program can contribute to the multistep process of tumorigenesis, because too little cell death can disturb tissue homeostasis. Further, blockade of apoptosis pathways can cause treatment failure, because intact apoptosis signalling cascades largely mediate therapy-induced cytotoxicity. The elucidation of apoptosis pathways in pancreatic carcinoma over the last decade has resulted in the identification of various molecular defects. How apoptosis pathways can be exploited for the treatment of pancreatic cancer will be discussed in this review.

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.

Bypassing cancer drug resistance by activating multiple death pathways--a proposal from the study of circumventing cancer drug resistance by induction of necroptosis

Cancer drug resistance is a complex, dynamic, and "elusive" system rather than merely a matter of some drug-resistant factors. Current pharmacological approaches aim to restore the efficacy of the standard chemotherapy against drug-resistant cancers via reactivating apoptosis and inhibiting drug transporters, simply because the current available anticancer drugs mostly induce apoptosis and many of them are the substrates/inducers of the drug transporters. However, since there are so many different types of defects in apoptotic pathways as well as numerous drug transporters, which could simultaneously contribute to cancer drug resistance, to succeed in the approach is theoretically possible but practically extremely difficult. To circumvent cancer drug resistance is an alternative choice. Since there are multiple death pathways with molecular mechanisms distinct from each other, we previously proposed that the barriers set up in cancer cells to avoid one pathway were not problems for another. Thus, no matter how dynamic, complex, and "elusive" the resistance occurs along one death pathway (e.g., apoptosis), the resistance would be sequestered within this pathway, and would not affect another death pathway with mechanisms distinct from the former, and vice versa, e.g., apoptotic resistant cancers can be sensitive to an induction of a nonapoptotic death. Indeed, we recently demonstrated that the cancer cells resistant to apoptotic inducers such as anthracycline antibiotics, vinca alkaloids, epipodophylotoxins, were sensitive to necroptotic inducers such as shikonin. Therefore, to bypass cancer drug resistance is principally achievable by simultaneously activating multiple death pathways using combined classes of death inducers (apoptosis, autophagy, necroptosis, etc.). Although each class of death inducers has its own action window and limit in killing cancer cells, a rationalized combination of several classes of death inducers that compliment each other would maximize their efficacy while simultaneously minimizing their weakness. Such "mixed bullets" would probably achieve a good therapeutic efficacy by bypassing cancer drug resistance.

Preclinical characterization of AEG35156/GEM 640, a second-generation antisense oligonucleotide targeting X-linked inhibitor of apoptosis

PURPOSE

Cancer cells can use X-linked inhibitor of apoptosis (XIAP) to evade apoptotic cues, including chemotherapy. The antitumor potential of AEG35156, a novel second-generation antisense oligonucleotide directed toward XIAP, was assessed in human cancer models when given as a single agent and in combination with clinically relevant chemotherapeutics.

EXPERIMENTAL DESIGN

AEG35156 was characterized for its ability to cause dose-dependent reductions of XIAP mRNA and protein in vitro and in vivo, to sensitize cancer cell lines to death stimuli, and to exhibit antitumor activity in multiple human cancer xenograft models as a single agent or in combination with chemotherapy.

RESULTS

AEG35156 reduced XIAP mRNA levels with an EC50 of 8 to 32 nmol/L and decreased XIAP protein levels by >80%. Loss of XIAP protein correlated with increased sensitization to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis in Panc-1 pancreatic carcinoma cells. AEG35156 exhibited potent antitumor activity relative to control oligonucleotides in three human cancer xenograft models (prostate, colon, and lung) and was capable of inducing complete tumor regression when combined with taxanes. Antitumor effects of AEG35156 correlated with suppression of tumor XIAP levels.

CONCLUSIONS

AEG35156 reduces XIAP levels and sensitizes tumors to chemotherapy. AEG35156 is presently under clinical assessment in multiple phase I trials in cancer patients as a single agent and in combination with docetaxel in solid tumors or cytarabine/idarubicin in leukemia.

Inhibition of RIP and c-FLIP enhances TRAIL-induced apoptosis in pancreatic cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has recently emerged as a cancer therapeutic agent because it is capable of preferentially inducing apoptosis in human cancer over normal cells. The majority of human pancreatic cancers, unfortunately, are resistant to TRAIL treatment. Here, we show that the inhibition of caspase-8 cleavage is the most upstream event in TRAIL resistance in pancreatic cancers. TRAIL treatment led to the cleavage of caspase-8 and downstream caspase-9, caspase-3, and DNA fragmentation factor 45 (DFF45) in TRAIL-sensitive pancreatic cancer cell lines (BXPC-3, PACA-2). This caspase-8-initiated caspase cascade, however, was inhibited in TRAIL-resistant pancreatic cancer cell lines (PANC-1, ASPC-1, CAPAN-1, CAPAN-2). The long and short forms of cellular Fas-associated death domain-like interleukin-1beta-converting enzyme-inhibitory protein (c-FLIP(L), c-FLIP(S)) were highly expressed in the TRAIL-resistant as compared to the sensitive cells; knockdown of c-FLIP(L) and c-FLIP(S) by a short hairpin RNA (shRNA) rendered the resistant cells sensitive to TRAIL-induced apoptosis through the cleavage of caspase-8 and activation of the mitochondrial pathway. Receptor-interacting protein (RIP) has been reported in TRAIL-induced activation of NF-kappaB and we show here that knockdown of RIP sensitized the resistant cells to TRAIL-induced apoptosis. These results indicate the role of c-FLIP and RIP in caspase-8 inhibition and thus TRAIL resistance. Treatment of the resistant cells with camptothecin, celecoxib and cisplatin resulted in the downregulation of c-FLIP and caused a synergistic apoptotic effect with TRAIL. These studies therefore suggest that combination treatment with chemotherapy can overcome TRAIL resistance and enhance TRAIL therapeutic efficacy in treating pancreatic cancers.

Expression of the IAP protein family is dysregulated in pancreatic cancer cells and is important for resistance to chemotherapy

Pancreatic cancer is one of the most aggressive human tumors with a 5-year survival rate of only 3% and a striking resistance to chemotherapy and radiotherapy. The search for new therapeutic approaches includes strategies exploiting the deregulation of apoptotic pathways commonly found in cancer cells. The IAP proteins are inhibitors of apoptosis that have altered activity in numerous cancer types and are implicated in resistance to chemotherapy, and therefore are potentially interesting as therapeutic targets. We investigated alterations in the expression of IAPs and their inhibitors in pancreatic adenocarcinoma by using real-time PCR, in situ hybridization and immunohistochemistry. We found differential expression of various IAPs in this malignancy, and particularly we observed overexpression of cIAP-2, survivin, livin and XIAP. We also looked for correlations between the expression of IAPs and resistance to paclitaxel, doxorubicin, CDDP and 5-fluorouracil, and found that resistance to these drugs correlates most significantly with expression of cIAP-2. Using RNAi to downregulate these proteins we further confirmed that the levels of cIAP-2 and XIAP influence the response to the anti-cancer drugs, although only marginally for 5-FU. We conclude that anti-tumor strategies based on the inhibition of particular IAPs can be useful in targeting pancreatic adenocarcinoma.

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

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

Complementary effects of HDAC inhibitor 4-PB on gap junction communication and cellular export mechanisms support restoration of chemosensitivity of PDAC cells

Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease and one of the cancer entities with the lowest life expectancy. Beside surgical therapy, no effective therapeutic options are available yet. Here, we show that 4-phenylbutyrate (4-PB), a known and well-tolerable inhibitor of histone deacetylases (HDAC), induces up to 70% apoptosis in all cell lines tested (Panc 1, T4M-4, COLO 357, BxPc3). In contrast, it leads to cell cycle arrest in only half of the cell lines tested. This drug increases gap junction communication between adjacent T3M-4 cells in a concentration-dependent manner and efficiently inhibits cellular export mechanisms in Panc 1, T4M-4, COLO 357 and BxPc3 cells. Consequently, in combination with gemcitabine 4-PB shows an overadditive effect on induction of apoptosis in BxPc3 and T3M-4 cells (up to 4.5-fold compared to single drug treatment) with accompanied activation of Caspase 8, BH3 interacting domain death agonist (Bid) and poly (ADP-ribose) polymerase family, member 1 (PARP) cleavage. Although the inhibition of the mitogen-activated protein kinase-pathway has no influence on fulminant induction of apoptosis, the inhibition of the JNK-pathway by SP600125 completely abolishes the overadditive effect induced by the combined application of both drugs, firstly reported by this study.

Common and contrasting genomic profiles among the major human lung cancer subtypes

Lung cancer is the leading cause of cancer mortality worldwide. With the recent success of molecularly targeted therapies in this disease, a detailed knowledge of the spectrum of genetic lesions in lung cancer represents a critical step in the development of additional effective agents. An integrated high-resolution survey of regional amplifications and deletions and gene expression profiling of non-small-cell lung cancers (NSCLC) identified 93 focal high-confidence copy number alterations (CNAs), with 21 spanning less than 0.5 Mb with a median of five genes. Most CNAs were novel and included high-amplitude amplification and homozygous deletion events. Pathogenic relevance of these genomic alterations was further reinforced by their recurrence and overlap with focal alterations of other tumor types. Additionally, the comparison of the genomic profiles of the two major subtypes of NSCLC, adenocarcinoma (AC) and squamous cell carcinoma (SCC), showed an almost complete overlap with the exception of one amplified region on chromosome 3, specific for SCC. Among the few genes overexpressed within this amplicon was p63, a known regulator of squamous cell differentiation. These findings suggest that the AC and SCC subtypes may arise from a common cell of origin and they are driven to their distinct phenotypic end points by altered expression of a limited number of key genes such as p63.

Regulation of TRAIL-induced apoptosis by XIAP in pancreatic carcinoma cells

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a promising candidate for cancer therapy because of its relative tumor selectivity. However, many cancers including pancreatic cancer remain resistant towards TRAIL. To develop TRAIL for cancer therapy of pancreatic carcinoma, it will therefore be pivotal to elucidate the molecular mechanisms of TRAIL resistance. Here, we identify X-linked inhibitor of apoptosis (XIAP) as a regulator of TRAIL sensitivity in pancreatic carcinoma cells. Full activation of effector caspases, loss of mitochondrial membrane potential and cytochrome c release following TRAIL treatment were markedly impaired in pancreatic carcinoma cell lines, which poorly responded to TRAIL (PaTuII, PancTu1, ASPC1, DanG), compared to TRAIL-sensitive Colo357 pancreatic carcinoma cells. Stable downregulation of XIAP by RNA interference significantly reduced survival and enhanced TRAIL-induced apoptosis in pancreatic carcinoma cells. Also, downregulation of XIAP significantly increased CD95-induced cell death. Importantly, knockdown of XIAP strongly inhibited clonogenicity of pancreatic cancer cells treated with TRAIL indicating that XIAP promotes clonogenic survival of pancreatic carcinoma cells. Thus, our findings for the first time indicate that targeting XIAP represents a promising strategy to enhance the antitumor activity of TRAIL in pancreatic cancer, which has important clinical implications.

Overexpression of cellular inhibitor of apoptosis protein 2 is an early event in the progression of pancreatic cancer

AIM

To determine the role of two antiapoptotic proteins of the inhibitor of apoptosis protein family, cellular inhibitor of apoptosis protein 1 (cIAP1) and cellular inhibitor of apoptosis protein 2 (cIAP2), in human pancreatic carcinogenesis.

METHODS

mRNA levels were measured in pancreatic tissues and pancreatic cancer cell lines by quantitative reverse transcriptase PCR. Protein expression was assessed in pancreatic cancer cell lines by immunoblotting and in pancreatic tissues by immunohistochemistry, and correlated with pathological and survival data.

RESULTS

cIAP1 expression was constantly high in non-neoplastic pancreatic tissues, in pancreatic intraepithelial neoplasia (PanIN) lesions, as well as in a subset of primary and metastatic pancreatic ductal adenocarcinomas (PDAC), and a preferential cytoplasmatic localisation was observed in the tumour tissues. cIAP1 expression was rare in a cohort of cystic tumours. cIAP2 mRNA levels were significantly higher (2.4 fold) in PDAC than in normal tissues. cIAP2 protein was overexpressed in PDAC, and was detectable in low- and high-grade PanIN lesions. Moreover, cIAP2 was often expressed in pancreatic cystic tumours. cIAP1 and cIAP2 mRNA and protein were detected in all the examined cell lines. Survival analysis revealed a shorter survival in patients with cIAP1/cIAP2-positive tumours.

CONCLUSIONS

cIAP1 might contribute to the regulation of the apoptotic process in the normal and in the neoplastic pancreas, depending on its subcellular localisation. Overexpression of cIAP2 is a common and early event in the progression of pancreatic cancer, and could therefore potentially influence the important pathophysiological aspects of PDAC, such as anoikis or chemoresistance.

Proteomic analysis of chronic pancreatitis and pancreatic adenocarcinoma

BACKGROUND & AIMS

Markers to differentiate among pancreatic adenocarcinoma, chronic pancreatitis, and normal pancreas would be of significant clinical utility. This study was therefore designed to analyze the proteome of such specimens and identify new candidate proteins for differential diagnosis.

METHODS

A PowerBlot analysis with more than 900 well-characterized antibodies was performed with tissue specimens from patients with chronic pancreatitis, pancreatic adenocarcinoma, and normal pancreas. Differential expression of selected proteins was confirmed on a larger scale by quantitative reverse transcription-polymerase chain reaction and immunohistochemistry using tissue arrays.

RESULTS

A total of 30 and 102 proteins showed significant deregulation between normal pancreas when compared with chronic pancreatitis and pancreatic adenocarcinoma, respectively, and although a substantial proportion were found similarly dysregulated in both chronic pancreatitis and pancreatic adenocarcinoma, several proteins were identified as potential disease-specific markers.

CONCLUSIONS

A large number of proteins are differentially expressed in chronic pancreatitis and pancreatic adenocarcinoma compared with normal pancreas. Among these, expression analysis of UHRF1, ATP7A, and aldehyde oxidase 1 in combination could potentially provide a useful additional diagnostic tool for fine-needle aspirated or cytological specimens obtained during endoscopic investigations.

Gemcitabine-mediated apoptosis is associated with increased CD95 surface expression but is not inhibited by DN-FADD in Colo357 pancreatic cancer cells

This study investigates the role of caspase-8 and DN-FADD, an inhibitor of CD95-dependent caspase-8 activation, in gemcitabine-induced apoptosis of Colo357 pancreatic cancer cells. Gemcitabine-mediated apoptosis was monitored by the kinetics of caspase-8 activation and cytochrome c release. Gemcitabine treatment of Colo357 cells increased CD95 surface expression, raising the possibility of the involvement of CD95 in gemcitabine-mediated caspase-8 activation. However, ectopic expression of DN-FADD and treatment of cells with the antagonistic anti-CD95 antibody ZB4 both failed to suppress gemcitabine-induced apoptosis but substantially inhibited CD95-mediated apoptosis. DN-FADD, which surprisingly accumulated in nuclei of Colo357 cells, was unable to block caspase-8 activation mediated by either gemcitabine or CD95. These observations argue against a role of CD95 in gemcitabine-induced caspase-8 activation and reveal that the anti-apoptotic function of DN-FADD differs from caspase-8 inhibition in Colo357 cells.

High-resolution genomic profiles of human lung cancer

Lung cancer is the leading cause of cancer mortality worldwide, yet there exists a limited view of the genetic lesions driving this disease. In this study, an integrated high-resolution survey of regional amplifications and deletions, coupled with gene-expression profiling of non-small-cell lung cancer subtypes, adenocarcinoma and squamous-cell carcinoma (SCC), identified 93 focal copy-number alterations, of which 21 span <0.5 megabases and contain a median of five genes. Whereas all known lung cancer genes/loci are contained in the dataset, most of these recurrent copy-number alterations are previously uncharacterized and include high-amplitude amplifications and homozygous deletions. Notably, despite their distinct histopathological phenotypes, adenocarcinoma and SCC genomic profiles showed a nearly complete overlap, with only one clear SCC-specific amplicon. Among the few genes residing within this amplicon and showing consistent overexpression in SCC is p63, a known regulator of squamous-cell differentiation. Furthermore, intersection with the published pancreatic cancer comparative genomic hybridization dataset yielded, among others, two focal amplicons on 8p12 and 20q11 common to both cancer types. Integrated DNA-RNA analyses identified WHSC1L1 and TPX2 as two candidates likely targeted for amplification in both pancreatic ductal adenocarcinoma and non-small-cell lung cancer.

HGS-ETR1, a fully human TRAIL-receptor 1 monoclonal antibody, induces cell death in multiple tumour types in vitro and in vivo

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a variety of tumour cells through activation of TRAIL-R1 and TRAIL-R2 death signalling receptors. Here, we describe the characterisation and activity of HGS-ETR1, the first fully human, agonistic TRAIL-R1 mAb that is being developed as an antitumour therapeutic agent. HGS-ETR1 showed specific binding to TRAIL-R1 receptor. HGS-ETR1 reduced the viability of multiple types of tumour cells in vitro, and induced activation of caspase 8, Bid, caspase 9, caspase 3, and cleavage of PARP, indicating activation of TRAIL-R1 alone was sufficient to induce both extrinsic and intrinsic apoptotic pathways. Treatment of cell lines in vitro with HGS-ETR1 enhanced the cytotoxicity of chemotherapeutic agents (camptothecin, cisplatin, carboplatin, or 5-fluorouracil) even in tumour cell lines that were not sensitive to HGS-ETR1 alone. In vivo administration of HGS-ETR1 resulted in rapid tumour regression or repression of tumour growth in pre-established colon, non-small-cell lung, and renal tumours in xenograft models. Combination of HGS-ETR1 with chemotherapeutic agents (topotecan, 5-fluorouracil, and irinotecan) in three independent colon cancer xenograft models resulted in an enhanced antitumour efficacy compared to either agent alone. Pharmacokinetic studies in the mouse following intravenous injection showed that HGS-ETR1 serum concentrations were biphasic with a terminal half-life of 6.9–8.7 days and a steady-state volume of distribution of approximately 60 ml kg⁻¹. Clearance was 3.6–5.7 ml⁻¹ day⁻¹ kg⁻¹. These data suggest that HGS-ETR1 is a specific and potent antitumour agent with favourable pharmacokinetic characteristics and the potential to provide therapeutic benefit for a broad range of human malignancies.

The anti-tumor effect of Apo2L/TRAIL on patient pancreatic adenocarcinomas grown as xenografts in SCID mice

Background

Apo2L/TRAIL has considerable promise for cancer therapy based on the fact that this member of the tumor necrosis factor family induces apoptosis in the majority of malignant cells, while normal cells are more resistant. Furthermore, in many cells, when Apo2L/TRAIL is combined with chemotherapy, the effect is synergistic. The majority of this work has been carried out using cell lines. Therefore, investigation of how patient tumors respond to Apo2L/TRAIL can validate and/or complement information obtained from cell lines and prove valuable in the design of future clinical trials.

Methods

We have investigated the Apo2L/TRAIL sensitivity of patient derived pancreatic tumors using a patient tumor xenograft/ SCID mouse model. Mice bearing engrafted tumors were treated with Apo2L/TRAIL, gemcitabine or a combination of both therapies.

Results

Patient tumors grown as xenografts exhibited a spectrum of sensitivity to Apo2L/TRAIL. Both Apo2L/TRAIL sensitive and resistant pancreatic tumors were found, as well as tumors that showed heterogeneity of response. Changes in apoptotic signaling molecules in a sensitive tumor were analyzed by Western blot following Apo2L/TRAIL treatment; loss of procaspase 8, Bid and procaspase 3 was observed and correlated with inhibition of tumor growth. However, in a tumor that was highly resistant to killing by Apo2L/TRAIL, although there was a partial loss of procaspase 8 and Bid in response to Apo2L/TRAIL treatment, loss of procaspase 3 was negligible. This resistant tumor also expressed a high level of the anti-apoptotic molecule Bcl-X_L that, in comparison, was not detected in a sensitive tumor. Importantly, in the majority of these tumors, addition of gemcitabine to Apo2L/TRAIL resulted in a greater anti-tumor effect than either therapy used alone.

Conclusion

These data suggest that in a clinical setting we will see heterogeneity in the response of patients' tumors to Apo2L/TRAIL, including tumors that are highly sensitive as well as those that are resistant. While much more work is needed to understand the molecular basis for this heterogeneity, it is very encouraging, that Apo2L/TRAIL in combination with gemcitabine increased therapeutic efficacy in almost every case and therefore may be a highly effective strategy for controlling human pancreatic cancer validating and expanding upon what has been reported for cell lines.

CD95 and TRAF2 promote invasiveness of pancreatic cancer cells

Pancreatic adenocarcinoma represents a tumor type with extremely poor prognosis. High apoptosis resistance and a strong invasive and early metastatic potential contribute to its highly malignant phenotype. Here we identified the death receptor adaptor molecule TRAF2 as a key player in pancreatic cancer pathophysiology. Using immunohistochemistry and Western blot analysis we found TRAF2 overexpressed in 34 of 36 pancreatic tumor samples as well as in pancreatic tumor cell lines resistant to CD95-mediated apoptosis. The high TRAF2 protein level was not related to chromosomal changes, as monitored by FISH analysis. Instead, the NF-kappaB- and MEK-signaling pathways were involved. Introduction of a TRAF2 expression vector in CD95-sensitive Colo357 cells resulted in (i) resistance to CD95-induced apoptosis; (ii) increased constitutive NF-kappaB and AP-1 activity; and (iii) higher basal secretion of matrix metalloproteinases (MMPs), urokinase-type plasminogen activator (uPA), and IL-8, leading to increased invasiveness. High apoptosis resistance and uPA secretion could be reverted by TRAF2-specific siRNA. Stimulation of TRAF2-overexpressing cells with CD95 ligand led to induction of NF-kappaB and AP-1, enhanced IL-8- and uPA-secretion, and a further increased invasiveness. Thus, TRAF2 overexpression does not only block apoptosis induction by CD95 but also converts this death receptor into a mediator of invasiveness.

Apoptotic Pathways and Therapy Resistance in Human Malignancies

Apoptosis and necrosis are two morphologically distinct forms of cell death that are important for maintaining of cellular homeostasis. Almost all agents can provoke either response when applied to cells; however, the duration of treatment and the dose of the used agents determine which type of death (apoptosis or necrosis) is initiated. The response of tumors to chemo-, radio-, and hormone therapy or to treatment with biologically active agents may depend at least in part on the propensity of these tumors to undergo cell death. Some tumors, e.g., leukemias, small cell lung cancer, and seminomas, respond quickly to first-line therapy; this fast response is thought to result from induction of apoptosis. Solid tumors, on the other hand, usually respond slowly and less effectively, with cell death characterized not only by apoptosis but also by necrosis, or mitotic catastrophe. It is likely that resistance of tumors to treatment might be associated with defects in, or dysregulation of, different steps of the apoptotic pathways. Several attempts were undertaken to use the knowledge of these defects to design new drugs, which might either activate or re-activate the apoptotic machinery of tumor cells. Here we discuss the apoptotic pathways and their role in therapy resistance of human malignancies. Although such studies are still in progress, they offer great promise for future cancer therapy. We hope that some of these agents will turn out to be valuable additions to the future therapeutic arsenal, which will most probably include a combination of conventional cytotoxic drugs and molecular target-based pro-apoptotic drugs.

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.

Mathematical modeling reveals threshold mechanism in CD95-induced apoptosis

Mathematical modeling is required for understanding the complex behavior of large signal transduction networks. Previous attempts to model signal transduction pathways were often limited to small systems or based on qualitative data only. Here, we developed a mathematical modeling framework for understanding the complex signaling behavior of CD95(APO-1/Fas)-mediated apoptosis. Defects in the regulation of apoptosis result in serious diseases such as cancer, autoimmunity, and neurodegeneration. During the last decade many of the molecular mechanisms of apoptosis signaling have been examined and elucidated. A systemic understanding of apoptosis is, however, still missing. To address the complexity of apoptotic signaling we subdivided this system into subsystems of different information qualities. A new approach for sensitivity analysis within the mathematical model was key for the identification of critical system parameters and two essential system properties: modularity and robustness. Our model describes the regulation of apoptosis on a systems level and resolves the important question of a threshold mechanism for the regulation of apoptosis.