Moderate activation of the apoptosis inhibitor bcl-xL worsens the prognosis in pancreatic cancer

A risk signature based on endoplasmic reticulum stress-associated genes predicts prognosis and immunity in pancreatic cancer

Introduction: The involvement of endoplasmic reticulum (ER) stress in cancer biology is increasingly recognized, yet its role in pancreatic cancer (PC) remains unclear. This study aims to elucidate the impact of ER stress on prognosis and biological characteristics in PC patients. Methods: A bioinformatic analysis was conducted using RNA-seq data and clinicopathological information from PC patients in the TCGA and ICGC databases. The ER stress-associated gene sets were extracted from MSigDB. ER stress-associated genes closely linked with overall survival (OS) of PC patients were identified via log-rank test and univariate Cox analysis, and further narrowed by LASSO method. A risk signature associated with ER stress was formulated using multivariate Cox regression and assessed through Kaplan-Meier curves, receiver operating characteristic (ROC) analyses, and Harrell's concordance index. External validation was performed with the ICGC cohort. The single-sample gene-set enrichment analysis (ssGSEA) algorithm appraised the immune cell infiltration landscape. Results: Worse OS in PC patients with high-risk signature score was observed. Multivariate analysis underscored our ER stress-associated signature as a valuable and independent predictor of prognosis. Importantly, these results based on TCGA were further validated in ICGC dataset. In addition, our risk signature was closely associated with homeostasis, protein secretion, and immune regulation in PC patients. In particular, PC microenvironment in the high-risk cluster exhibited a more immunosuppressive status. At last, we established a nomogram model by incorporating the risk signature and clinicopathological parameters, which behaves better in predicting prognosis of PC patients. Discussion: This comprehensive molecular analysis presents a new predictive model for the prognosis of PC patients, highlighting ER stress as a potential therapeutic target. Besides, the findings indicate that ER stress can have effect modulating PC immune responses.

Splicing alterations in pancreatic ductal adenocarcinoma: a new molecular landscape with translational potential

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal cancers worldwide, mainly due to its late diagnosis and lack of effective therapies, translating into a low 5-year 12% survival rate, despite extensive clinical efforts to improve outcomes. International cooperative studies have provided informative multiomic landscapes of PDAC, but translation of these discoveries into clinical advances are lagging. Likewise, early diagnosis biomarkers and new therapeutic tools are sorely needed to tackle this cancer. The study of poorly explored molecular processes, such as splicing, can provide new tools in this regard. Alternative splicing of pre-RNA allows the generation of multiple RNA variants from a single gene and thereby contributes to fundamental biological processes by finely tuning gene expression. However, alterations in alternative splicing are linked to many diseases, and particularly to cancer, where it can contribute to tumor initiation, progression, metastasis and drug resistance. Splicing defects are increasingly being associated with PDAC, including both mutations or dysregulation of components of the splicing machinery and associated factors, and altered expression of specific relevant gene variants. Such disruptions can be a key element enhancing pancreatic tumor progression or metastasis, while they can also provide suitable tools to identify potential candidate biomarkers and discover new actionable targets. In this review, we aimed to summarize the current information about dysregulation of splicing-related elements and aberrant splicing isoforms in PDAC, and to describe their relationship with the development, progression and/or aggressiveness of this dismal cancer, as well as their potential as therapeutic tools and targets.

Modulation of Ca2+ signaling by antiapoptotic Bcl-2 versus Bcl-xL: From molecular mechanisms to relevance for cancer cell survival

Members of the Bcl-2-protein family are key controllers of apoptotic cell death. The family is divided into antiapoptotic (including Bcl-2 itself, Bcl-xL, Mcl-1, etc.) and proapoptotic members (Bax, Bak, Bim, Bim, Puma, Noxa, Bad, etc.). These proteins are well known for their canonical role in the mitochondria, where they control mitochondrial outer membrane permeabilization and subsequent apoptosis. However, several proteins are recognized as modulators of intracellular Ca²⁺ signals that originate from the endoplasmic reticulum (ER), the major intracellular Ca²⁺-storage organelle. More than 25 years ago, Bcl-2, the founding member of the family, was reported to control apoptosis through Ca²⁺ signaling. Further work elucidated that Bcl-2 directly targets and inhibits inositol 1,4,5-trisphosphate receptors (IP₃Rs), thereby suppressing proapoptotic Ca²⁺ signaling. In addition to Bcl-2, Bcl-xL was also shown to impact cell survival by sensitizing IP₃R function, thereby promoting prosurvival oscillatory Ca²⁺ release. However, new work challenges this model and demonstrates that Bcl-2 and Bcl-xL can both function as inhibitors of IP₃Rs. This suggests that, depending on the cell context, Bcl-xL could support very distinct Ca²⁺ patterns. This not only raises several questions but also opens new possibilities for the treatment of Bcl-xL-dependent cancers. In this review, we will discuss the similarities and divergences between Bcl-2 and Bcl-xL regarding Ca²⁺ homeostasis and IP₃R modulation from both a molecular and a functional point of view, with particular emphasis on cancer cell death resistance mechanisms.

Molecular signaling in pancreatic ductal metaplasia: emerging biomarkers for detection and intervention of early pancreatic cancer

Pancreatic ductal metaplasia (PDM) is the transformation of potentially various types of cells in the pancreas into ductal or ductal-like cells, which eventually replace the existing differentiated somatic cell type(s). PDM is usually triggered by and manifests its ability to adapt to environmental stimuli and genetic insults. The development of PDM to atypical hyperplasia or dysplasia is an important risk factor for pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDA). Recent studies using genetically engineered mouse models, cell lineage tracing, single-cell sequencing and others have unraveled novel cellular and molecular insights in PDM formation and evolution. Those novel findings help better understand the cellular origins and functional significance of PDM and its regulation at cellular and molecular levels. Given that PDM represents the earliest pathological changes in PDA initiation and development, translational studies are beginning to define PDM-associated cell and molecular biomarkers that can be used to screen and detect early PDA and to enable its effective intervention, thereby truly and significantly reducing the dreadful mortality rate of PDA. This review will describe recent advances in the understanding of PDM biology with a focus on its underlying cellular and molecular mechanisms, and in biomarker discovery with clinical implications for the management of pancreatic regeneration and tumorigenesis.

Bcl-xL DNAzymes promote radiosensitivity and chemosensitivity in colorectal cancer cells via enhancing apoptosis

Background

RNA-cleaving deoxyribozymes (DNAzymes) are catalytic deoxyribonucleic acid molecules that have become a promising new class of gene suppressors by binding and cleaving target mRNA. This study investigated whether DNAzymes targeting Bcl-xL enhanced the effectiveness of radiotherapy and chemotherapy in colorectal cancer (CRC) cells.

Methods

Two types of CRC cells, SW480 and SW837, were transfected with five DNAzymes. Cell viability, Bcl-xL expression and apoptosis were examined. SW480 xenograft model was used to examine the combined effects of Bcl-xL DNAzymes and 5-FU (or X-rays) on tumor growth.

Results

Three Bcl-xL DNAzymes, DT882, DT883, and DT884 were identified to be effective in suppressing Bcl-xL expression and causing cell apoptosis. Furthermore, DT882 combined with 5-FU or radiotherapy addictively promoted cell apoptosis and significantly inhibited the growth of SW480 xenografts in vivo.

Conclusions

These results suggest that Bcl-xL DNAzymes can enhance the radiosensitivity and chemosensitivity in CRC cells via inducing apoptosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40360-022-00553-x.

The Role of Mitochondria in the Chemoresistance of Pancreatic Cancer Cells

The first-line chemotherapies for patients with unresectable pancreatic cancer (PC) are 5-fluorouracil (5-FU) and gemcitabine therapy. However, due to chemoresistance the prognosis of patients with PC has not been significantly improved. Mitochondria are essential organelles in eukaryotes that evolved from aerobic bacteria. In recent years, many studies have shown that mitochondria play important roles in tumorigenesis and may act as chemotherapeutic targets in PC. In addition, according to recent studies, mitochondria may play important roles in the chemoresistance of PC by affecting apoptosis, metabolism, mtDNA metabolism, and mitochondrial dynamics. Interfering with some of these factors in mitochondria may improve the sensitivity of PC cells to chemotherapeutic agents, such as gemcitabine, making mitochondria promising targets for overcoming chemoresistance in PC.

Research advances of intracellular mechanisms underlying gemcitabine resistance in pancreatic cancer

Pancreatic cancer is one of the most deadly malignant tumors that endanger human health, and pancreatic ductal adenocarcinoma (PDAC) is the most common histological type. Due to the lack of specific clinical symptoms, physical signs, and effective screening biomarkers for early stage PDAC, only 15%-20% of patients are qualified for surgical resection. Consequently, gemcitabine (GEM)-based monotherapy or combination therapy is still the most important or even the only treatment option. However, the overall response rate of PDAC to GEM is less than 20%, and GEM resistance is one of the most important factors affecting the efficacy of chemotherapy. At present, the mechanism of GEM resistance has not been clarified, which may involve congenital and acquired regulation. The heterogeneity of PDAC further increases its complexity. However, regulation of intracellular signaling pathways is the ultimate event to induce GEM resistance. This article will review the recent advances in research of GEM metabolism and regulation of signaling pathways in PDAC cells, and discuss potential GEM chemosensitization strategies, in order to improve the effective rate of chemotherapy and the outcome.

The anti-cancer effect of flaxseed lignan derivatives on different acute myeloid leukemia cancer cells

Flaxseeds have been known for their anti-cancerous effects due to the high abundance of lignans released upon ingestion. The most abundant lignan, secoisolariciresinol diglucoside (SDG), is ingested during the dietary intake of flax, and is then metabolized in the gut into two mammalian lignan derivatives, Enterodiol (END) and Enterolactone (ENL). These lignans were previously reported to possess anti-tumor effects against breast, colon, and lung cancer. This study aims to investigate the potential anti-cancerous effect of the flaxseed lignans SDG, END and ENL on acute myeloid leukemia cells (AML) in vitro and to decipher the underlying molecular mechanism. AML cell lines, (KG-1 and Monomac-1) and a normal lymphoblastic cell line were cultured and treated with the purified lignans. ENL was found to be the most promising lignan, as it exhibits a significant selective dose- and time-dependent cytotoxic effect in both AML cell lines, contrary to normal cells. The cytotoxic effects observed were attributed to apoptosis induction, as revealed by an increase in Annexin V staining of AML cells with increasing ENL concentrations. The increase in the percentage of cells in the pre-G phase, in addition to cell death ELISA analysis, validated cellular and DNA fragmentation respectively. Analysis of protein expression using western blots confirmed the activation of the intrinsic apoptotic pathway upon ENL treatment. This was also accompanied by an increase in ROS production intracellularly. In conclusion, this study demonstrates that ENL has promising anti-cancer effects in AML cell lines in vitro, by promoting DNA fragmentation and the intrinsic apoptotic pathway, highlighting the protective health benefits of flax seeds in leukemia.

Structural Insights into PROTAC-Mediated Degradation of Bcl-xL

The Bcl-2 family of proteins, such as Bcl-xL and Bcl-2, play key roles in cancer cell survival. Structural studies of Bcl-xL formed the foundation for the development of the first Bcl-2 family inhibitors and FDA approved drugs. Recently, Proteolysis Targeting Chimeras (PROTACs) that degrade Bcl-xL have been proposed as a therapeutic modality with the potential to enhance potency and reduce toxicity versus antagonists. However, no ternary complex structures of Bcl-xL with a PROTAC and an E3 ligase have been successfully determined to guide this approach. Herein, we report the design, characterization, and X-ray structure of a VHL E3 ligase-recruiting Bcl-xL PROTAC degrader. The 1.9 Å heterotetrameric structure, composed of (ElonginB:ElonginC:VHL):PROTAC:Bcl-xL, reveals an extensive network of neo-interactions, between the E3 ligase and the target protein, and between noncognate parts of the PROTAC and partner proteins. This work illustrates the challenges associated with the rational design of bifunctional molecules where interactions involve composite interfaces.

Novel tumor suppressor role of miRNA-876 in cholangiocarcinoma

Cholangiocarcinoma (CCA) is a rare, highly invasive malignancy, and its incidence is increasing globally. MicroRNAs (miRNAs) mediate a wide array of cellular and biological processes and are dysregulated in various tumors. The functional and biological roles of miRNAs in CCA have not been fully elucidated. In this study, we show that miR-876 expression levels and copy number are significantly attenuated in the TCGA cohort of CCA tissue samples. TCGA expression data was consistent with the observed substantial decrease in miR-876 expression in patient samples and CCA cell lines. In-silico algorithm databases revealed BCL-XL as a potential target of miR-876. We observed miR-876 expression to be downregulated, whereas, BCL-XL upregulated in CCA cell lines. BCL-XL was identified as a direct functional target of miR-876 in CCA. miR-876-mediated reduction of BCL-XL regulated cell survival, induced apoptosis and caspase 3/7 expression in CCA. BCL-XL overexpression reversed the miR-876 mediated effect on CCA cell growth and apoptosis. Stable overexpression of miR-876 produced potent tumor suppressor activity and in vivo tumor cell growth reduction. Overexpression of miR-876 in a patient-derived xenograft (PDX) cell line significantly suppressed BCL-XL expression and spheroid formation with a concomitant induction of caspase 3/7 activity and apoptosis. This study demonstrates a novel tumor suppressor role for miR-876 in CCA, identifies BCL-XL as an actionable target, and suggests a potential therapeutic role for miR-876 in CCA.

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.

Potential Benefits of Annona muricata in Combating Cancer: A Review

The incidence of cancer is increasing each year, which generates concerns regarding the efficacy of the current treatment options. This has caused patients to seek alternatives to complement or to replace surgery, chemotherapy and radiotherapy. Annona muricata and other plants have been shown to have promising compounds that can be utilised in the treatment of cancer. Native to the tropical and subtropical parts of the world, A. muricata plant extracts contain compounds that are particularly effective against cancer cells. In light of increasing concerns regarding the limitations of cancer treatment in hospitals, this review attempts to highlight the benefits of A. muricata and its potential to be integrated as one of the treatment options against cancer.

Increased Bcl-xL Expression in Pancreatic Neoplasia Promotes Carcinogenesis by Inhibiting Senescence and Apoptosis

BACKGROUND & AIMS

Bcl-xL, an anti-apoptotic Bcl-2 family protein, is overexpressed in 90% of pancreatic ductal adenocarcinoma (PDAC) cases. However, Bcl-xL expression in pancreatic intraepithelial neoplasias (PanINs) and its significance in PDAC carcinogenesis remain unclear. The aim of this study was to elucidate the significance of Bcl-xL expression in PanINs.

METHODS

We investigated the expression levels of Bcl-xL in pancreas-specific KrasG12D (P-KrasG12D) mice and human PanINs and PDAC. We examined the impact of Bcl-xL expression on Kras-mutated pancreatic neoplasia using Bcl-xL-overexpressing P-KrasG12D mice and Bcl-xL-knockout P-KrasG12D mice.

RESULTS

In P-KrasG12D mice, the number of PanINs increased and their grades progressed with age. In total, 55.6% of these mice developed PDAC at 12-14 months. According to the immunohistochemistry of mouse pancreas and human resected specimens, Bcl-xL expression was increased significantly in PanIN-1 compared with that in normal pancreatic ducts, and augmented further with the progression of pancreatic neoplasia in PanIN-2/3 and PDAC. Oncogene-induced senescence was observed frequently in PanIN-1, but rarely was detected in PanIN-2/3 and PDAC. Bcl-xL overexpression significantly accelerated the progression to high-grade PanINs and PDAC and reduced the survival of P-KrasG12D mice. Bcl-xL overexpression in P-KrasG12D mice suppressed oncogene-induced senescence in PanIN-1 and inhibited apoptosis in PanIN-3. Bcl-xL deficiency in P-KrasG12D mice induced cellular senescence in PanIN-2/3.

CONCLUSIONS

Bcl-xL expression increases with the progression from PanIN-1 to PDAC, whereas oncogene-induced senescence decreases. Bcl-xL overexpression increases PDAC incidence rates by inhibiting oncogene-induced senescence and apoptosis in PanINs. Conversely, Bcl-xL deficiency induced senescence in PanINs. Anti-Bcl-xL treatments may have the potency to suppress the progression from PanINs to PDAC.

Bcl-xL promotes metastasis independent of its anti-apoptotic activity

Bcl-xL suppresses mitochondria-mediated apoptosis and is frequently overexpressed in cancer to promote cancer cell survival. Bcl-xL also promotes metastasis. However, it is unclear whether this metastatic function is dependent on its anti-apoptotic activity in the mitochondria. Here we demonstrate that Bcl-xL promotes metastasis independent of its anti-apoptotic activity. We show that apoptosis-defective Bcl-xL mutants and an engineered Bcl-xL targeted to the nucleus promote epithelial–mesenchymal transition, migration, invasion and stemness in pancreatic neuroendocrine tumour (panNET) and breast cancer cell lines. However, Bcl-xL proteins targeted to the mitochondria or outside of the nucleus do not have these functions. We confirm our findings in spontaneous and xenograft mouse models. Furthermore, Bcl-xL exerts metastatic function through epigenetic modification of the TGFβ promoter to increase TGFβ signalling. Consistent with these findings, we detect nuclear Bcl-xL in human metastatic panNETs. Taken together, the metastatic function of Bcl-xL is independent of its anti-apoptotic activity and its residence in the mitochondria.

Bcl-xL is an anti-apoptotic protein that has also been implicated in metastasis. In this study, the authors show that nuclear Bcl-xL promotes metastasis by regulating TGFβ signaling, which is independent of the anti-apoptotic activity of Bcl-xL.

Mitochondrial transcription factor a worsens the clinical course of patients with pancreatic cancer through inhibition of apoptosis of cancer cells

OBJECTIVE

Mitochondrial transcription factor A (mtTFA) is mandatory for both the transcription and maintenance of mitochondrial DNA. This study aimed to investigate the significance of mtTFA expression in pancreatic ductal adenocarcinoma (PDAC).

METHODS

Surgical specimens from 93 patients with PDAC who all underwent pancreatectomy were immunohistochemically stained using a polyclonal anti-mtTFA antibody. The relationship between the expression of mtTFA, clinicopathologic factors, and prognosis of these patients were evaluated.

RESULTS

Positive mtTFA expression was significantly associated with lymphovascular invasion and metastatic recurrence in the liver and correlated with an advanced surgical stage. A univariate analysis showed that the patients with positive mtTFA expression had a significantly shorter survival time than those patients with negative mtTFA expression, and a multivariate analysis revealed that mtTFA expression was one of the independent prognostic factors in patients with PDAC. Positive mtTFA expression was significantly correlated with a low apoptotic index but not significantly correlated with the mind bomb homolog-1 (MIB-1) index.

CONCLUSIONS

The expression mtTFA worsens the clinical course of patients with PDAC through the inhibition of apoptosis of PDAC cells and is an independent marker for the poor prognosis of the patients with PDAC after pancreatectomy. Mitochondrial transcription factor A may be a novel target for the treatment of PDAC.

Evaluation of Bcl-2, Bcl-x and Cleaved Caspase-3 in Malignant Peripheral Nerve Sheath Tumors and Neurofibromas

AIMS: To study the expression of Bcl-2, Bcl-x, as well the presence of cleaved caspase-3 in neurofibromas and malignant peripheral nerve sheath tumors. The expression of Bcl-2 and Bcl-x and the presence of cleaved caspase 3 were compared to clinicopathological features of malignant peripheral nerve sheath tumors and their impact on survival rates were also investigated. MATERIALS AND METHODS: The evaluation of Bcl-2, Bcl-x and cleaved caspase-3 was performed by immunohistochemistry using tissue microarrays in 28 malignant peripheral nerve sheath tumors and 38 neurofibromas. Immunoquantification was performed by computerized digital image analysis. CONCLUSIONS: Apoptosis is altered in neurofibromas and mainly in malignant peripheral nerve sheath tumors. High levels of cleaved caspase-3 are more common in tumors with more aggressive histological features and it is associated with lower disease free survival of patients with malignant peripheral nerve sheath tumors.

Phenethyl isothiocyanate inhibits proliferation and induces apoptosis in pancreatic cancer cells in vitro and in a MIAPaca2 xenograft animal model

Pancreatic cancer is often diagnosed at an advanced stage and it has a poor prognosis that points to an increased need to develop effective chemoprevention strategies for this disease. We examined the ability of phenethyl isothiocyanate (PEITC), a naturally occurring isothiocyanate found in cruciferous vegetables, to inhibit the growth of pancreatic cancer cells in vitro and in a MIAPaca2 xenograft animal model. Exposure to PEITC inhibited pancreatic cancer cell growth in a dose-dependent manner, with an IC50 of approximately 7 μmol/L. PEITC treatment induced G2/M phase cell cycle arrest, downregulated the antiapoptotic proteins Bcl-2 and Bcl-XL, upregulated the proapoptotic protein Bak, and suppressed Notch 1 and 2 levels. In addition, treatment with PEITC induced cleavage of poly-(ADP-ribose) polymerase and led to increased cytoplasmic histone-associated DNA fragmentation and subdiploid (apoptotic) fraction in pancreatic cancer cells. Oral administration of PEITC suppressed the growth of pancreatic cancer cells in a MIAPaca2 xenograft animal model. Our data show that PEITC exerts its inhibitory effect on pancreatic cancer cells through several mechanisms, including G2/M phase cell cycle arrest and induction of apoptosis, and supports further investigation of PEITC as a chemopreventive agent for pancreatic cancer.

ARC is highly expressed in nasopharyngeal carcinoma and confers X-radiation and cisplatin resistance

Apoptosis repressor with caspase recruitment domain (ARC), an inhibitor of apoptosis, is primarily expressed in terminally differentiated tissues. Recent studies have revealed that ARC is highly expressed in a variety of human cancer cell lines and epithelial-derived cancers, which suggests that ARC plays an important role in the process of carcinogenesis. However, whether ARC is involved in the development of nasopharyngeal carcinoma (NPC) and the various roles it plays in NPC remain unclear. In the present study, we examined the expression of ARC in NPC cell lines and NPC tissues and the relationship between its subcellular expression and clinicopathological grade; moreover, we explored the effect of this protein on radiation resistance and chemoresistance in NPC cells. We found that cytoplasmic ARC was expressed at high levels in NPC tissues, at moderate levels in severe atypical hyperplasia and at low levels in benign nasopharyngeal tissues. High expression of cytoplasmic and nuclear ARC was correlated with advanced local invasion. However, only a small amount of nuclear ARC was expressed in NPC in contrast to cytoplasmic ARC. We also found that attenuation of ARC expression by miRNA resulted in decreased X-radiation and cisplatin resistance in NPC CNE-2 cells. In contrast, overexpression of ARC resulted in increased X-radiation and cisplatin resistance in NPC 6-10B cells. Furthermore, we demonstrated that ARC appears to be critical for blocking the activation of casapse-8 and casapse-2 in NPC cells subjected to X-radiation or cisplatin. These results suggest that high expression of ARC plays an important role in the pathogenesis of NPC and leads to X-radiation and cisplatin resistance in NPC.

Control of cellular Bcl-xL levels by deamidation-regulated degradation

Deamidation of two asparagines activates a conditional PEST sequence to target Bcl-xL for degradation.

The cellular concentration of Bcl-x_L is among the most important determinants of treatment response and overall prognosis in a broad range of tumors as well as an important determinant of the cellular response to several forms of tissue injury. We and others have previously shown that human Bcl-x_L undergoes deamidation at two asparaginyl residues and that DNA-damaging antineoplastic agents as well as other stimuli can increase the rate of deamidation. Deamidation results in the replacement of asparginyl residues with aspartyl or isoaspartyl residues. Thus deamidation, like phosphorylation, introduces a negative charge into proteins. Here we show that the level of human Bcl-x_L is constantly modulated by deamidation because deamidation, like phosphorylation in other proteins, activates a conditional PEST sequence to target Bcl-x_L for degradation. Additionally, we show that degradation of deamidated Bcl-x_L is mediated at least in part by calpain. Notably, we present sequence and biochemical data that suggest that deamidation has been conserved from the simplest extant metazoans through the human form of Bcl-x_L, underscoring its importance in Bcl-x_L regulation. Our findings strongly suggest that deamidation-regulated Bcl-x_L degradation is an important component of the cellular rheostat that determines susceptibility to DNA-damaging agents and other death stimuli.

Cellular levels of the pro-survival protein Bcl-x_L are an important determinant of cellular susceptibility to many death stimuli, including most cancer therapies. We previously showed that human Bcl-x_L undergoes deamidation – the conversion of two neutral asparaginyl side-chains into negatively charged aspartyl side-chains – a process that occurs spontaneously but is accelerated by the treatment of tumor cells with DNA-damaging agents. Here, we show that deamidation activates a hitherto undetected signal sequence within Bcl-x_L that targets it for degradation by a pathway involving the proteolytic enzyme calpain. This increased degradation of Bcl-x_L, and the consequent enhanced cellular susceptibility to programmed cell death, may contribute to the ability of DNA-damaging agents to kill tumors. We also demonstrate that deamidation of Bcl-x_L has likely been conserved from the simplest metazoans to humans, underscoring the importance of deamidation in the regulation of Bcl-x_L.

Behavior of solvent-exposed hydrophobic groove in the anti-apoptotic Bcl-XL protein: clues for its ability to bind diverse BH3 ligands from MD simulations

Bcl-XL is a member of Bcl-2 family of proteins involved in the regulation of intrinsic pathway of apoptosis. Its overexpression in many human cancers makes it an important target for anti-cancer drugs. Bcl-XL interacts with the BH3 domain of several pro-apoptotic Bcl-2 partners. This helical bundle protein has a pronounced hydrophobic groove which acts as a binding region for the BH3 domains. Eight independent molecular dynamics simulations of the apo/holo forms of Bcl-XL were carried out to investigate the behavior of solvent-exposed hydrophobic groove. The simulations used either a twin-range cut-off or particle mesh Ewald (PME) scheme to treat long-range interactions. Destabilization of the BH3 domain-containing helix H2 was observed in all four twin-range cut-off simulations. Most of the other major helices remained stable. The unwinding of H2 can be related to the ability of Bcl-XL to bind diverse BH3 ligands. The loss of helical character can also be linked to the formation of homo- or hetero-dimers in Bcl-2 proteins. Several experimental studies have suggested that exposure of BH3 domain is a crucial event before they form dimers. Thus unwinding of H2 seems to be functionally very important. The four PME simulations, however, revealed a stable helix H2. It is possible that the H2 unfolding might occur in PME simulations at longer time scales. Hydrophobic residues in the hydrophobic groove are involved in stable interactions among themselves. The solvent accessible surface areas of bulky hydrophobic residues in the groove are significantly buried by the loop LB connecting the helix H2 and subsequent helix. These observations help to understand how the hydrophobic patch in Bcl-XL remains stable in the solvent-exposed state. We suggest that both the destabilization of helix H2 and the conformational heterogeneity of loop LB are important factors for binding of diverse ligands in the hydrophobic groove of Bcl-XL.

The N-terminal helix of Bcl-xL targets mitochondria

Anti- and pro-apoptotic Bcl-2 family members regulate the mitochondrial phase of apoptotic cell death. The mitochondrial targeting mechanisms of Bcl-2 family proteins are tightly regulated. Known outer mitochondrial membrane targeting sequences include the C-terminal tail and central helical hairpin. Bcl-xL also localizes to the inner mitochondrial membrane, but these targeting sequences are unknown. Here we investigate the possibility that the N-terminus of Bcl-xL also contains mitochondrial targeting information. Amino acid residues 1-28 of Bcl-xL fused to EGFP are sufficient to target mitochondria. Although positive charges and helical propensity are required for targeting, similar to import sequences the N-terminus is not sufficient for efficient mitochondrial import.

LCL124, a cationic analog of ceramide, selectively induces pancreatic cancer cell death by accumulating in mitochondria

Treatment of pancreatic cancer that cannot be surgically resected currently relies on minimally beneficial cytotoxic chemotherapy with gemcitabine. As the fourth leading cause of cancer-related death in the United States with dismal survival statistics, pancreatic cancer demands new and more effective treatment approaches. Resistance to gemcitabine is nearly universal and appears to involve defects in the intrinsic/mitochondrial apoptotic pathway. The bioactive sphingolipid ceramide is a critical mediator of apoptosis initiated by a number of therapeutic modalities. It is noteworthy that insufficient ceramide accumulation has been linked to gemcitabine resistance in multiple cancer types, including pancreatic cancer. Taking advantage of the fact that cancer cells frequently have more negatively charged mitochondria, we investigated a means to circumvent resistance to gemcitabine by targeting delivery of a cationic ceramide (l-t-C6-CCPS [LCL124: ((2S,3S,4E)-2-N-[6'-(1″-pyridinium)-hexanoyl-sphingosine bromide)]) to cancer cell mitochondria. LCL124 was effective in initiating apoptosis by causing mitochondrial depolarization in pancreatic cancer cells but demonstrated significantly less activity against nonmalignant pancreatic ductal epithelial cells. Furthermore, we demonstrate that the mitochondrial membrane potentials of the cancer cells were more negative than nonmalignant cells and that dissipation of this potential abrogated cell killing by LCL124, establishing that the effectiveness of this compound is potential-dependent. LCL124 selectively accumulated in and inhibited the growth of xenografts in vivo, confirming the tumor selectivity and therapeutic potential of cationic ceramides in pancreatic cancer. It is noteworthy that gemcitabine-resistant pancreatic cancer cells became more sensitive to subsequent treatment with LCL124, suggesting that this compound may be a uniquely suited to overcome gemcitabine resistance in pancreatic cancer.

The Immunohistochemical Expression of STAT3, Bcl-xL, and MMP-2 Proteins in Colon Adenoma and Adenocarcinoma

Background/Aims

Signal transducers and activators of transcription (STATs) are a family of transcription factors that are activated in response to cytokines and growth factors. STAT3 activation has been implicated in modulating the activity of downstream mediators, such as Bcl-xL and matrix metalloproteinase-2 (MMP-2). The aim of this study was to investigate the immunohistochemical expression of STAT3, B-cell lymphoma-extra large (Bcl-xL), and MMP-2 proteins according to histopathological parameters in colon adenocarcinomas, including lymph node metastasis, tumor differentiation, the TNM stage and the tumor size.

Methods

Immunohistochemical staining with monoclonal STAT3, Bcl-xL, and MMP-2 antibodies was performed on paraffin-embedded specimens from 20 colon adenomas and 39 adenocarcinomas.

Results

The expression of STAT3, Bcl-xL, and MMP-2 was increased in the adenocarcinomas as compared with the adenomas (p<0.001). STAT3 expression was stronger in tumors with a distant metastasis than in tumors without a distant metastasis (p=0.012). A larger tumor size was related to an increase in STAT3 expression (p=0.035).

Conclusions

STAT3, Bcl-xL, and MMP-2 may play important roles in the tumorigenesis of colorectal carcinoma. STAT3 may be indicative of a poor prognosis due to its correlation with distant metastases and a larger tumor size.

Down-regulation of STAT3 expression by vector-based small interfering RNA inhibits pancreatic cancer growth

AIM: To evaluate the effect of RNA interference (RNAi) mediated silence of signal transduction and activation of transcription (STAT)3 on the growth of human pancreatic cancer cells both in vitro and in vivo.

METHODS: STAT3 specific shRNA was used to silence the expression of STAT3 in pancreatic cancer cell line SW1990. The anti-growth effects of RNAi against STAT3 were studied in vitro and in experimental cancer xenografts in nude mice. The potential pathways involved in STAT3 signaling were detected using reverse transcription polymerase chain reaction and western blotting.

RESULTS: The expression of the STAT3 was inhibited using RNAi in SW1990 cells. RNAi against STAT3 inhibited cell proliferation, induced cell apoptosis and significantly reduced the levels of CyclinD1 and Bcl-xL when compared with parental and control vector-transfected cells. In vivo experiments showed that RNAi against STAT3 inhibited the tumorigenicity of SW1990 cells and significantly suppressed tumor growth when it was directly injected into tumors.

CONCLUSION: STAT3 signaling pathway plays an important role in the progression of pancreatic cancer, and silence of STAT3 gene using RNAi technique may be a novel therapeutic option for treatment of pancreatic cancer.

Downregulation of STAT3 signaling induces apoptosis but also promotes anti-apoptotic gene expression in human pancreatic cancer cell lines

Signal transducer and activator of transcription 3 (STAT3) is a key regulator of cytokine signaling pathways that regulates gene expression. In pancreatic cancer, constitutive activation of STAT3 contributes to oncogenesis by preventing apoptosis through upregulation of anti-apoptotic proteins. We have examined the inhibition of STAT3 as a potential therapeutic approach in pancreatic cancer. siRNA targeting STAT3 was used to evaluate the role of STAT3 in modulating the expression of Survivin/BIRC5 and BCL-xL in the pancreatic cancer cell lines PANC-1 and BxPC-3 and induction of apoptosis. Expression of STAT3, Survivin/BIRC5, and BCL-xL on mRNA and protein level was measured by real-time RT-PCR and Western blot analysis 24, 48, and 72 h after transfection. STAT3 downregulation resulted in a decrease of cell viability in both cell lines and induced apoptosis in BxPC-3 cells. Despite significant inhibition of STAT3, the expression of the anti-apoptotic genes Survivin/BIRC5 and BCL-xL were not subsequently downregulated. Even more, the cell line BxPC-3 shows a significant increase of Survivin/BIRC5 and BCL-xL mRNA after 48-72 h as a result of STAT3 downregulation. Inactivation of STAT3 in pancreatic cancer cell lines induces apoptosis but also may promote the expression of anti-apoptotic genes.

MicroRNA-203 expression as a new prognostic marker of pancreatic adenocarcinoma

BACKGROUND

Detection of aberrant microRNA (miR) expression may contribute to diagnosis and prognosis of various cancers. The aim of this study is to evaluate the correlation between miR-203 expression and prognosis of patients with pancreatic adenocarcinoma after curative resection.

METHODS

A total of 113 formalin-fixed paraffin-embedded tissue samples of pancreatic adenocarcinoma, 20 samples of chronic pancreatitis, and 8 samples of normal pancreas were obtained. We investigated the association of miR-203 expression measured by quantitative reverse-transcription polymerase chain reaction assays with clinicopathological parameters and survival times.

RESULTS

miR-203 was overexpressed in pancreatic adenocarcinoma samples compared with chronic pancreatitis (P < 0.001) and normal pancreas (P = 0.001) samples. An association between miR-203 expression and clinicopathological factors of pancreatic adenocarcinoma was not observed. On univariate analysis, the high-miR-203 group and the subgroup (20%) of cases with the highest miR-203 overexpression had significantly shorter survival time (P = 0.048 and P = 0.024, respectively). Multivariate analysis revealed that miR-203 expression was an independent predictor of poor prognosis in cases with no residual tumor (relative risk 2.298, P = 0.027).

CONCLUSIONS

miR-203 expression is a new prognostic marker in pancreatic adenocarcinoma patients.

Preclinical studies of apogossypolone, a novel pan inhibitor of bcl-2 and mcl-1, synergistically potentiates cytotoxic effect of gemcitabine in pancreatic cancer cells

OBJECTIVE

Overexpression of antiapoptotic Bcl-2 family proteins confers resistance to conventional therapy in pancreatic cancer patients. Apogossypolone (ApoG2) is an analogue of (-)-gossypol, exhibiting binding activity with Ki values of 35 nmol/L for Bcl-2 and 25 nmol/L for Mcl-1. The present study was designed to test our hypothesis whether inactivation of Bcl-2 family of proteins using ApoG2 could sensitize pancreatic cancer cells to the cytotoxic effect of gemcitabine.

METHODS

Two pancreatic cancer cell lines were treated with ApoG2, gemcitabine, and their combination; cytotoxicity and apoptosis was confirmed by MTT and histone/DNA enzyme-linked immunosorbent assay. Coimmunoprecipitation experiments were performed to elucidate the mechanism of action of ApoG2. In vivo efficacy of ApoG2 was evaluated in a xenograft model to confirm its therapeutic benefit with gemcitabine.

RESULTS

When ApoG2 was combined with gemcitabine, increased cytotoxicity and apoptosis was evident. Coimmunoprecipitation experiment revealed that ApoG2 blocks the heterodimerization of Mcl-1/Bax and Bcl-2/Bim in cells. Furthermore, administration of ApoG2 with gemcitabine resulted in a statistically higher antitumor activity compared with either ApoG2 or gemcitabine alone in a severe combined immunodeficiency mouse xenograft model.

CONCLUSIONS

Apogossypolone, which functions as a potent pan-Bcl-2 family inhibitor, seems therapeutically promising for future translational studies including the treatment of pancreatic cancer.

S100A4 mRNA is a diagnostic and prognostic marker in pancreatic carcinoma

OBJECTIVE

The aim of this study is to evaluate the clinical significance of S100A4 mRNA expression in pancreatic cancer.

MATERIALS AND METHODS

We obtained invasive ductal carcinoma (IDC) cells from ten lesions, intraductal papillary mucinous neoplasm (IPMN) cells from 20 lesions, and normal ductal cells from 20 normal pancreatic tissues by laser microdissection of frozen tissues. S100A4 expression was examined in the microdissected cells and in formalin-fixed paraffin-embedded (FFPE) samples of 87 pancreatic cancers by quantitative reverse transcription-polymerase chain reaction.

RESULTS

IDC cells expressed higher levels of S100A4 than IPMN cells (P = 0.002) and normal ductal cells (P < 0.001), although the difference between IPMN cells and normal ductal cells was not statistically significant (P = 0.070). Analysis of FFPE samples revealed that high S100A4 expression was significantly associated with a shorter overall survival (P = 0.023). In immunohistochemical analysis, the extent of S100A4 mRNA expression was significantly correlated with the expression of S100A4 protein (P = 0.028).

CONCLUSION

S100A4 could be a marker for malignancy in pancreatic tumors and for poor prognosis in patients with pancreatic cancer.

Emerging drugs in the treatment of pancreatic cancer

BACKGROUND

Pancreatic cancer is the fourth leading cause of cancer-related death in the US. However, there is a growing belief that novel biological agents could improve survival of patients with this cancer. Gemcitabine-based chemotherapy remains the cornerstone treatment for advanced pancreatic cancers. So far, the current targeted agents that have been used in combination with gemcitabine have failed to improve clinical outcomes. This failure may stem from the heterogeneous molecular pathogenesis of pancreatic cancers, which involves several oncogenic pathways and defined genetic mutations.

OBJECTIVE

The aims of this review are: i) to define the existing treatments available at present for patients with pancreatic cancers in the neo-adjuvant, adjuvant, locally advanced and metastatic settings; ii) to highlight the molecular heterogeneity of the cancers and the rationale for targeting specific oncogenic pathways; iii) to give an overview of targeted agents that may potentially have an impact in the treatment of pancreatic cancers.

CONCLUSIONS

Molecular pathogenesis of pancreatic cancer involves several pathways and defined genetic mutations. Targeting these complex molecular pathways with a combination of novel biological and chemotherapeutic agents could potentially improve patient outcome.

ApoG2 inhibits antiapoptotic Bcl-2 family proteins and induces mitochondria-dependent apoptosis in human lymphoma U937 cells

Lymphoma is one of the most common types of hematological malignancies and proteins from the Bcl-2 family are highly expressed in human lymphomas. Apogossypolone (ApoG2), the most potent gossypol derivative, has been classified as a novel small-molecule inhibitor of antiapoptotic Bcl-2 family proteins. Here, we assessed the in-vitro cytotoxicity of ApoG2 on human U937 lymphoma cells, and explored the underlying intracellular molecular mechanisms of ApoG2. Using the WST-8 assay, we found that ApoG2 inhibited growth of U937 cells in a dose-dependent and time-dependent manner, and the IC50 values were 30.08, 14.81, and 9.26 mumol/l for 24, 48, and 72 h treatments, respectively. ApoG2 also induced apoptosis in U937 cells, as noted through changes in morphological characteristics, including cellular internucleosomal DNA fragmentation and the appearance of a sub-G1 apoptotic peak. Treatment with ApoG2 downregulated Bcl-xL and Mcl-1 protein expression and blocked the binding of Bcl-2 with Bax protein. Furthermore, ApoG2 led to an abundant release of cytochrome c from mitochondria and a five-fold increase in the activity of caspase-3 and caspase-9. Taken together, our results suggest that ApoG2 could effectively suppress the growth of human lymphoma cell line U937 through the inhibition of the antiapoptotic Bcl-2 family proteins and the induction of mitochondria-dependent apoptotic cell death.

Genome-wide array-based comparative genomic hybridization analysis of pancreatic adenocarcinoma: identification of genetic indicators that predict patient outcome

We analyzed the subchromosomal numerical aberrations of 44 surgically resected pancreatic adenocarcinomas by array-based comparative genomic hybridization. The aberration profile ranged widely between cases, suggesting the presence of multiple or complementary mechanisms of evolution in pancreatic cancer, and was associated with lymph node metastasis and venous or serosal invasion. A large number of small loci, previously uncharacterized in pancreatic cancer, showed non-random loss or gain. Frequent losses at 1p36, 4p16, 7q36, 9q34, 11p15, 11q13, 14q32-33, 16p13, 17p11-13, 17q11-25, 18q21-tel, 19p13, 21q22 and 22q11-12, and gains at 1q25, 2p16, 2q21-37, 3q25, 5p14, 5q11-13, 7q21, 7p22, 8p22, 8q21-23, 10q21, 12p13, 13q22, 15q13-22 and 18q11 were identified. Sixteen loci were amplified recurrently. We identified novel chromosomal alterations that were significantly associated with a range of malignant phenotypes. Gain of LUNX, HCK, E2F1 and DNMT3b at 20q11, loss of p73 at 1p36 and gain of PPM1D at 17q23 independently predicted patient outcome. Expression profiling of amplified genes identified Smurf1 and TRRAP at 7q22.1, BCAS1 at 20q13.2-3, and VCL at 10q22.1 as potential novel oncogenes. Our results contribute to a complete description of genomic structural aberrations and the identification of potential therapeutic targets and genetic indicators that predict patient outcome in pancreatic adenocarcinoma.

Constitutively activated nuclear factor-kappaB, but not induced NF-kappaB, leads to TRAIL resistance by up-regulation of X-linked inhibitor of apoptosis protein in human cancer cells

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis in most, but not all, cancer cells. The molecular factors regulating the sensitivity to TRAIL are still incompletely understood. The transcription factor nuclear factor-kappaB (NF-kappaB) has been implicated, but its exact role is controversial. We studied different cell lines displaying varying responses to TRAIL and found that TRAIL can activate NF-kappaB in all our cancer cell lines regardless of their TRAIL sensitivity. Inhibition of NF-kappaB via adenoviral expression of the IkappaB-alpha super-repressor only sensitized the TRAIL-resistant pancreatic cancer cell line Panc-1. Panc-1 cells harbor constitutively activated NF-kappaB, pointing to a possible role of preactivated NF-kappaB in protection from TRAIL. Furthermore, we could reduce X-linked inhibitor of apoptosis protein (XIAP) levels in Panc-1 cells by inhibition of constitutively activated NF-kappaB and sensitize Panc-1 cells to TRAIL by RNA interference against XIAP. These results implicate elevated XIAP levels caused by high basal NF-kappaB activity in TRAIL resistance and suggest that therapeutic strategies involving TRAIL can be abetted by inhibition of NF-kappaB and/or XIAP only in tumor cells with constitutively activated NF-kappaB.

Distinct promoters mediate constitutive and inducible Bcl-XL expression in malignant lymphocytes

Bcl-X(L) is a Bcl-2-related survival protein that is essential for normal development. Bcl-X(L) expression is rapidly induced by a wide range of survival signals and many cancer cells constitutively express high levels. The Bcl-X gene has a complex organization with multiple promoters giving rise to RNAs with alternate 5' non-coding exons. Here we have investigated the mechanisms that control basal and induced expression of Bcl-X(L) in B-lymphoma cells. Antisense experiments demonstrated that Bcl-X(L) was essential for survival of Akata6 B-lymphoma cells. The levels of RNAs containing the IB Bcl-X non-coding exon, derived from the distal 1B promoter, correlated with basal expression of Bcl-X(L) in primary malignant B cells and this promoter was highly active in B-cell lines. The activity of this promoter was largely dependent on a single Ets binding site and Ets family proteins were bound at this promoter in intact cells. CD40 ligand (CD40L)-induced cell survival was associated with increased Bcl-X(L) expression and accumulation of exon IA-containing RNAs, derived from the proximal 1A promoter. Nuclear factor-kappaB (NF-kappaB) inhibition prevented induction of Bcl-X(L) protein and exon IA-containing RNAs by CD40L. Therefore, the distal Bcl-X 1B promoter plays a critical role in driving constitutive expression-mediated via Ets family proteins in malignant B cells, whereas NF-kappaB plays a central role in the induction of Bcl-X(L) in response to CD40 signalling via the proximal 1A promoter.

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.

Sodium butyrate sensitises human pancreatic cancer cells to both the intrinsic and the extrinsic apoptotic pathways

Pancreatic cancer is characterised by a highly malignant phenotype with a marked resistance to conventional therapies and to apoptotic activators. Here, we demonstrate that sodium butyrate (NaBt), an inhibitor of histone deacetylases, sensitises human pancreatic cancer cell lines to both mitochondria- and Fas-mediated apoptosis. The analysis of anti-apoptotic and pro-apoptotic members of the Bcl-2 family in untreated pancreatic cancer cell lines shows a generalised low expression of Bcl-2 and a strong expression of Bcl-xL. NaBt treatment results in a marked down-regulation of Bcl-xL expression, mitochondrial membrane depolarization, cytochrome c release from mitochondria, activation of caspase-9 and -3 and apoptosis induction. Furthermore, NaBt sensitises pancreatic cancer cells to Fas-mediated apoptosis as well. In fact, the combined treatment with NaBt and the agonistic antibody anti-Fas (CH11) is able to induce apoptosis at an early time, in which neither NaBt nor CH11 alone induce apoptosis. Down-regulation of FLIP and activation of caspase-8 allow apoptosis to occur. These findings suggest that sodium butyrate could represent a good candidate for the development of new therapeutic strategies aimed at improving chemotherapy and immunotherapy in pancreatic cancer.

Promoting apoptosis as a strategy for cancer drug discovery

Apoptosis is deregulated in many cancers, making it difficult to kill tumours. Drugs that restore the normal apoptotic pathways have the potential for effectively treating cancers that depend on aberrations of the apoptotic pathway to stay alive. Apoptosis targets that are currently being explored for cancer drug discovery include the tumour-necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptors, the BCL2 family of anti-apoptotic proteins, inhibitor of apoptosis (IAP) proteins and MDM2.

Nonpeptidic small-molecule inhibitor of Bcl-2 and Bcl-XL, (-)-Gossypol, enhances biological effect of genistein against BxPC-3 human pancreatic cancer cell line

OBJECTIVES

In pancreatic cancer, several important survival molecules such as EGFR, NF-kappaB, and Bcl-2 or Bcl-XL are highly activated. Thus, agents that inhibit NF-kappaB activation, together with agents that directly inhibit Bcl-2 or Bcl-XL protein function, may lead to enhanced cell killing. (-)-Gossypol, a natural polyphenolic compound isolated from cottonseeds, is a dual and potent small-molecule inhibitor of Bcl-2 and Bcl-XL proteins, with a Ki value in the 300-600 nM range for both proteins.

METHODS

: The BxPC-3 human pancreatic cell line was used in this study. (-)-Gossypol was dissolved in DMSO at 20 mmol/L as stock solution, and genistein was dissolved in 0.1 M Na2CO3 to make a 10 mM stock solution. For cell viability, apoptosis, and NF-kappaB studies, MTT assay, histone/DNA ELISA, and Electrophoretic Mobility Shift Assay (EMSA) were used, respectively. Coimmunoprecipitation experiments were designed to study Bcl-XL/Bim heterodimerization, and Western blots to study cytochrome c release.

RESULTS

(-)-Gossypol showed a concentration-dependent growth inhibition effect against BxPC-3 pancreatic cancer cell line and induced apoptosis with no effect on normal peripheral blood lymphocytes. Results from coimmunoprecipitation experiments indicate that the effect of (-)-gossypol is mediated, at least, in part via disrupting the heterodimerization of Bcl-XL with Bim in BxPC-3 pancreatic cancer cells. (-)-Gossypol completely disrupts Bcl-XL/Bim heterodimerization with no change in the total Bcl-XL or Bim protein, indicating that (-)-gossypol treatment does not affect the levels of Bcl-XL and Bim proteins. We have previously shown that genistein, a prominent soy isoflavone, transcriptionally down-regulates Bcl-2, Bcl-XL, VEGF, MMP-9, and uPAR via inhibiting NF-kappaB activity. In this study, genistein down-regulated NF-kappaB DNA binding activity and inhibited the growth of BxPC-3 pancreatic cancer cells. In addition, the combination of (-)-gossypol with genistein showed significantly greater growth inhibition compared with either agent alone.

CONCLUSION

From these results, we conclude that inhibition of NF-kappaB activity and direct inhibition of Bcl-2 or Bcl-XL function should serve as a novel strategy for pancreatic cancer therapy.

Molecular prognostic markers in pancreatic cancer: a systematic review

Pancreatic cancer is one of the most lethal tumours of the gastrointestinal tract. The ability to predict which patients would benefit most from surgical intervention and/or chemotherapy would be a great clinical asset. Considerable research has focused on identifying molecular events in pancreatic carcinogenesis, and their correlation with clinicopathological variables of pancreatic tumours and survival. This systematic review examined evidence from published manuscripts looking at molecular markers in pancreatic cancer and their correlation with tumour stage and grade, response to chemotherapy and long-term survival. A literature search was undertaken using PubMed and MEDLINE search engines, using the keywords p53, p21, p16, p27, SMAD4, K-ras, cyclin D1, Bax, Bcl-2, EGFR, EGF, c-erbB2, HB-EGF, TGFbeta, FGF, MMP, uPA, cathepsin, heparanase, E-cadherin, laminins, integrins, TMSF, CD44, cytokines, angiogenesis, VEGF, IL-8, beta-catenin, DNA microarray, and gene profiling. A bewildering number of biomarkers are currently under evaluation. For the most part, the evidence regarding their application as prognostic indicators is conflicting. The advent of gene microarray and mass spectrometric protein profiling offers the potential to examine many different biomarkers simultaneously. This 'protein/gene signature' could revolutionise work in this field and allow researchers to develop accurate and reproducible predictions of survival based on protein or gene profiles.

Bcl-XL protein levels determine apoptotic index in pancreatic carcinoma

OBJECTIVES

The present study was designed to analyze the expression of the major antiapoptotic molecules Bcl-2, Bcl-XL and the proapoptotic Bax in pancreatic ductal carcinoma and their correlation to the extent of apoptosis.

METHODS

Tissue samples were obtained from patients (age, 27-78 years) having surgery for pancreatic cancer. Normal pancreatic tissue away from the main tumor mass was also analyzed. The levels of Bcl-2, Bcl-XL, and Bax mRNA expression were analyzed by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR). The presence of corresponding proteins was determined by immunohistochemistry (IHC). The apoptotic index was determined by terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay.

RESULTS

A total of 25 cases were analyzed. The apoptotic index (percentage) ranged from 0.0% to 1.8%, with a median of 0.26. Semiquantitative RT-PCR revealed variable mRNA expression, with the Bcl-2/Bax ratio ranging from 0.2 to 1.5 and the Bcl-XL/Bax ratio ranging from 0.3 to 1.8. There was no correlation of mRNA levels with the apoptotic index. Immunohistochemical analysis showed positive Bcl-2, Bax, Bcl-XL expression in 20%, 72%, and 92% of cancer samples; however, their levels were variable. Spearman rank correlation coefficient test revealed a significant inverse association for the Bcl-XL IHC score and apoptotic index (P < 0.05). In contrast, Bcl-2, Bax protein levels did not show any association with the apoptotic index. However, as compared with the normal pancreas, Bcl-2, Bcl-XL, Bax were overexpressed in most of the pancreatic cancer samples (Mann-Whitney U test, P < 0.01).

CONCLUSION

In pancreatic cancer, there is an upregulation of all the apoptotic regulatory molecules and the apoptotic index is chiefly determined by Bcl-XL protein levels.

Predominant Bcl-XL knockdown disables antiapoptotic mechanisms: tumor necrosis factor-related apoptosis-inducing ligand-based triple chemotherapy overcomes chemoresistance in pancreatic cancer cells in vitro

Pancreatic cancer is lethal because of its invasiveness, rapid progression, and profound resistance to chemotherapy and radiation therapy. To identify the molecular mechanisms underlying this, we have examined the expression and potency of three major death receptors: tumor necrosis factor receptor (TNF-R), TNF-related apoptosis-inducing ligand receptor (TRAIL-R), and Fas in mediating cytotoxicity in four invasive pancreatic cancer cell lines. We have analyzed the expression of major antiapoptotic factors, cell cycle regulators and death receptor decoys (DcR) in comparison with normal pancreas tissues and five other human malignant tumor cell lines. We have found that different pancreatic cancer cell lines coexpress high-level TRAIL-R, Fas, and TNF-R1 but are strongly resistant to apoptosis triggered by the death receptors. DcR2 and DcR3 overexpression may partly contribute to the resistance of pancreatic cancer cells to TRAIL-R- and Fas-mediated cytotoxicity. Bcl-XL and Bcl-2 are predominantly overexpressed in pancreatic cancer cell lines, respectively. Bcl-XL is also predominantly overexpressed in prostate, colorectal, and intestinal cancer cells. The knockdown of the predominant Bcl-XL overexpression significantly reduces the viability of pancreatic cancer cells to TNFalpha- and TRAIL-mediated apoptosis by sublethal-dose single and combined antitumor drugs, including geldanamycin, PS-341, Trichostatin A, and doxorubicine. Geldanamyin and PS-341 synergistically block NFkappaB activation, suppress Akt/PKB pathway, and down-regulate Bcl-XL, Bcl-2, cIAP-1, and cyclin D1 expression. This combined regimen dramatically enhances TRAIL cytotoxic effects and breaks through chemoresistance. Bcl-XL plays a vital role in pancreatic cancer chemoresistance. Geldanamycin, PS-341, and TRAIL triple combination may be a novel therapeutic strategy for pancreatic cancer.

(−)-Gossypol acts directly on the mitochondria to overcome Bcl-2- and Bcl-XL-mediated apoptosis resistance

Aberrant overexpression of antiapoptotic members of the Bcl-2 protein family, including Bcl-2 and Bcl-XL, contributes to malignant transformation and subsequent resistance to traditional chemotherapeutics. Thus, these proteins represent attractive targets for novel anticancer agents. The small molecule, gossypol, was initially investigated as a contraceptive agent, but subsequently has been shown to possess anticancer properties in vitro and in vivo. Recently gossypol has been found to bind to Bcl-XL and, with less affinity, to Bcl-2. Here we investigate the ability of the (−) enantiomer of gossypol, (−)-gossypol, to overcome the apoptosis resistance conferred by Bcl-2 or Bcl-XL overexpression in Jurkat T leukemia cells. (−)-Gossypol potently induced cell death in Jurkat cells overexpressing Bcl-2 (IC50, 18.1 ± 2.6 μmol/L) or Bcl-XL (IC50, 22.9 ± 3.7 μmol/L). Vector-transfected control cells were also potently killed by (−)-gossypol (IC50, 7.0 ± 2.7 μmol/L). By contrast, the chemotherapy drug etoposide only induced efficient killing of vector-transfected cells (IC50, 9.6 ± 2.3μmol/L). Additionally, (−)-gossypol was more efficient than etoposide at inducing caspase-3 activation and phosphatidylserine externalization in the setting of Bcl-2 or Bcl-XL overexpression. (−)-Gossypol-induced apoptosis was associated with Bak activation and release of cytochrome c from mitochondria, suggesting a mitochondrial-mediated apoptotic mechanism. Moreover, (−)-gossypol treatment of isolated mitochondria purified from Bcl-2-overexpressing cells also resulted in cytochrome c release, indicating a possible direct action on Bcl-2 present in the mitochondrial outer membrane. Taken together, these results suggest that (−)-gossypol is a potent and novel therapeutic able to overcome apoptosis resistance by specifically targeting the activity of antiapoptotic Bcl-2 family members. (−)-Gossypol may be a promising new agent to treat malignancies that are resistant to conventional therapies.

Survival of patients with periampullary carcinoma is predicted by lymph node 8a but not by lymph node 16b1 status

BACKGROUND

The aim of this study was to assess the impact of metastatic disease in lymph nodes 8a and 16b1 (as defined by the Japanese Pancreas Society) on survival in patients with periampullary malignancy.

METHODS

Patients undergoing resection for primary pancreatic ductal adenocarcinoma or intrapancreatic bile duct adenocarcinoma were identified from a prospective database (September 1997-May 2003).

RESULTS

Thirteen of 54 and ten of 44 evaluable patients had metastatic involvement of lymph nodes 8a and 16b1 respectively. Metastatic involvement of lymph node 8a was associated with a significantly shorter median survival (197 versus 470 days; P = 0.003) but metastatic involvement of lymph node 16b1 did not affect survival (457 versus 503 days; P = 0.185). Multivariate analysis showed lymph node 8a status to be the strongest predictor of outcome (P = 0.006). Median survival of those with metastatic lymph node 8a was not significantly different from that of 81 patients with overt metastatic periampullary cancer at the time of diagnosis (98 days; P = 0.072)

CONCLUSION

Lymph node 8a was an independent prognostic factor in patients with periampullary malignancy, but lymph node 16b1 was not. Survival in those with metastatic lymph node 8a was not significantly different from that in patients with metastatic disease at presentation. Preoperative determination of lymph node 8a status may have important implications in selecting patients for treatment.

Comprehensive analysis of matrix metalloproteinase and tissue inhibitor expression in pancreatic cancer: increased expression of matrix metalloproteinase-7 predicts poor survival

PURPOSE

To enable the design of improved inhibitors of matrix metalloproteinases (MMPs) for the treatment of pancreatic cancer, the expression profiles of a range of MMPs and tissue inhibitors of MMPs (TIMPs) were determined.

EXPERIMENTAL DESIGN

Nine MMPs (MMPs 1-3, 7-9, 11, 12, and 14) and three TIMPs (TIMPs 1-3) were examined in up to 75 pancreatic ductal adenocarcinomas and 10 normal pancreata by immunohistochemistry. Eighteen additional pancreatic ductal adenocarcinomas and an additional eight normal pancreata were also analyzed by real-time reverse transcription-PCR and additionally for MMP-15.

RESULTS

There was increased expression by immunohistochemistry for MMPs 7, 8, 9, and 11 and TIMP-3 in pancreatic cancer compared with normal pancreas (P < 0.0001, 0.04, 0.0009, 0.005, and 0.0001, respectively). Real-time reverse transcription-PCR showed a significant increase in mRNA levels for MMP-11 in tumor tissue compared with normal pancreatic tissue (P = 0.0005) and also significantly reduced levels of MMP-15 (P = 0.0026). Univariate analysis revealed that survival was reduced by lymph node involvement (P = 0.0007) and increased expression of MMP-7 (P = 0.005) and (for the first time) MMP-11 (P = 0.02) but not reduced by tumor grade, tumor diameter, positive resection margins, adjuvant treatment, or expression of the remaining MMPs and TIMPs. On multivariate analysis, only MMP-7 predicted shortened survival (P < 0.05); however, increased MMP-11 expression was strongly associated with lymph node involvement (P = 0.0073).

CONCLUSIONS

We propose that the principle specificity for effective inhibitors of MMPs in pancreatic cancer should be for MMP-7 with secondary specificity against MMP-11. Moreover, these studies indicate that MMP-7 expression is a powerful independent prognostic indicator and potentially of considerable clinical value.

Sequence and helicity requirements for the proapoptotic activity of Bax BH3 peptides

Overexpression of the antiapoptotic proteins Bcl-2 and Bcl-XL is commonly observed in human malignancies and contributes to chemotherapy and radiation resistance. Bcl-2 and Bcl-XL inhibit apoptosis by binding to proapoptotic proteins such as Bax, thereby preventing chemotherapy-induced or radiation-induced release of cytochrome c from mitochondria and subsequent activation of the caspase protease cascade. Efforts to inhibit Bcl-2 or Bcl-XL function in tumor cells have focused on developing agents to inhibit the interactions of these proteins with proapoptotic proteins. Peptides derived from the BH3 domains of proapoptotic proteins have been shown to disrupt the interactions of Bcl-2 and Bcl-XL with key binding partners in cell-free reactions and to promote cellular apoptosis. However, less is known about the targets of BH3 peptides in intact cells as well as the sequence, length, and conformational requirements for peptide biological activity. In this report, we show that cell-permeable Bax BH3 peptides physically disrupt Bax/Bcl-2 heterodimerization in intact cells and that this disruption correlates with peptide-induced cell death. A point-mutant, control peptide that failed to disrupt intracellular Bax/Bcl-2 interactions also failed to promote apoptosis. To determine important sequence, length, and structural requirements for peptide activity, we generated and systematically analyzed the biological activities of 17 Bax BH3 peptide variants. Peptides were quantitatively examined for their ability to inhibit Bax/Bcl-2 and Bax/Bcl-XL heterodimerization in vitro and to promote cytochrome c release from mitochondria isolated from Jurkat, HL-60, U937, and PC-3 cells. Our results define 15 amino acids as the minimal length required for Bax BH3 peptide biological activity and show that amino acids COOH terminal to the BH3 core sequence are less critical than those located NH2 terminal to the core. In addition, circular dichroism spectroscopy revealed that high α-helical content generally correlated with, but was not sufficient for, peptide activity. Taken together, these studies provide a basis for future optimization of Bax BH3 peptide as a therapeutic anticancer agent.