Differential impact of cytoplasmic vs. nuclear RAD51 expression on breast cancer progression and patient prognosis.

RAD51 recombinase is one of the DNA damage repair proteins associated with breast cancer risk. Apart from its function to maintain genomic integrity within the cell nucleus, RAD51 localized to the cytoplasm has also been implicated in breast malignancy. However, limited information exists on the roles of cytoplasmic vs. nuclear RAD51 in breast cancer progression and patient prognosis. In the present study, the association of cytoplasmic and nuclear RAD51 with clinical outcomes of patients with breast cancer was analyzed, revealing that elevated cytoplasmic RAD51 expression was associated with breast cancer progression, including increased cancer stage, grade, tumor size, lymph node metastasis and chemoresistance, along with reduced patient survival. By contrast, elevated nuclear RAD51 expression largely had the inverse effect. Results from in vitro investigations supported the cancer­promoting effect of RAD51, showing that overexpression of RAD51 promoted breast cancer cell growth, chemoresistance and metastatic ability, while knockdown of RAD51 repressed these malignant behaviors. The current data suggest that differential expression of subcellular RAD51 had a distinct impact on breast cancer progression and patient survival. Specifically, cytoplasmic RAD51 in contrast to nuclear RAD51 was potentially an adverse marker in breast cancer.

IL-1RA promotes oral squamous cell carcinoma malignancy through mitochondrial metabolism-mediated EGFR/JNK/SOX2 pathway.

BACKGROUND: Interleukin-1 receptor antagonist (IL-1RA), a member of the IL-1 family, has diverse roles in cancer development. However, the role of IL-1RA in oral squamous cell carcinoma (OSCC), in particular the underlying mechanisms, remains to be elucidated. METHODS: Tumor tissues from OSCC patients were assessed for protein expression by immunohistochemistry. Patient survival was evaluated by Kaplan-Meier curve analysis. Impact of differential IL-1RA expression on cultured OSCC cell lines was assessed in vitro by clonogenic survival, tumorsphere formation, soft agar colony formation, and transwell cell migration and invasion assays. Oxygen consumption rate was measured by Seahorse analyzer or multi-mode plate reader. PCR array was applied to screen human cancer stem cell-related genes, proteome array for phosphorylation status of kinases, and Western blot for protein expression in cultured cells. In vivo tumor growth was investigated by orthotopic xenograft in mice, and protein expression in xenograft tumors assessed by immunohistochemistry. RESULTS: Clinical analysis revealed that elevated IL-1RA expression in OSCC tumor tissues was associated with increased tumor size and cancer stage, and reduced survival in the patient group receiving adjuvant radiotherapy compared to the patient group without adjuvant radiotherapy. In vitro data supported these observations, showing that overexpression of IL-1RA increased OSCC cell growth, migration/invasion abilities, and resistance to ionizing radiation, whereas knockdown of IL-1RA had largely the opposite effects. Additionally, we identified that EGFR/JNK activation and SOX2 expression were modulated by differential IL-1RA expression downstream of mitochondrial metabolism, with application of mitochondrial complex inhibitors suppressing these pathways. Furthermore, in vivo data revealed that treatment with cisplatin or metformin-a mitochondrial complex inhibitor and conventional therapy for type 2 diabetes-reduced IL-1RA-associated xenograft tumor growth as well as EGFR/JNK activation and SOX2 expression. This inhibitory effect was further augmented by combination treatment with cisplatin and metformin. CONCLUSIONS: The current study suggests that IL-1RA promoted OSCC malignancy through mitochondrial metabolism-mediated EGFR/JNK activation and SOX2 expression. Inhibition of this mitochondrial metabolic pathway may present a potential therapeutic strategy in OSCC.

ADSCs stimulated by resistin promote breast cancer cell malignancy via CXCL5 in a breast cancer coculture model.

The tumor microenvironment represents one of the main obstacles in breast cancer treatment owing to the presence of heterogeneous stromal cells, such as adipose-derived stem cells (ADSCs), that may interact with breast cancer cells and promote cancer development. Resistin is an adipocytokine associated with adverse breast cancer progression; however, its underlying mechanisms in the context of the breast tumor microenvironment remain largely unidentified. Here, we utilized a transwell co-culture model containing patient-derived ADSCs and breast cancer cell lines to investigate their potential interaction, and observed that breast cancer cells co-cultured with resistin-treated ADSCs (R-ADSCs) showed enhanced cancer cell growth and metastatic ability. Screening by proteome arrays revealed that C-X-C motif chemokine ligand 5 (CXCL5) was released in the conditioned medium of the co-culture system, and phosphorylated ERK was increased in breast cancer cells after co-culture with R-ADSCs. Breast cancer cells treated with the recombinant proteins of CXCL5 showed similarly enhanced cell migration and invasion ability as occurred in the co-culture model, whereas application of neutralizing antibodies against CXCL5 reversed these phenomena. The orthotopic xenograft in mice by breast cancer cells after co-culture with R-ADSCs had a larger tumor growth and more CXCL5 expression than control. In addition, clinical analysis revealed a positive correlation between the expression of resistin and CXCL5 in both tumor tissues and serum specimens of breast cancer patients. The current study suggests that resistin-stimulated ADSCs may interact with breast cancer cells in the tumor microenvironment via CXCL5 secretion, leading to breast cancer cell malignancy.

CD44 Mediates Oral Squamous Cell Carcinoma-Promoting Activity of MRE11 via AKT Signaling.

Oral cancer is one of the highest-incidence malignancies worldwide, with the occurrence of oral squamous cell carcinoma (OSCC) being the most frequently diagnosed form. A barrier for oral cancer management may arise from tumor cells that possess properties of cancer stemness, which has been recognized as a crucial factor in tumor recurrence and metastasis. As such, understanding the molecular mechanisms underlying these tumor cells may provide insights for improving cancer treatment. MRE11 is the core protein of the RAD50/MRE11/NBS1 complex with a primary role in DNA damage repair, and it has been diversely associated with tumor development including OSCC. In this study, we aimed to investigate the engagement of CD44, a cancer stemness marker functioning in the control of cell growth and motility, in OSCC malignancy under the influence of MRE11. We found that overexpression of MRE11 enhanced CD44 expression and tumorsphere formation in OSCC cells, whereas knockdown of MRE11 reduced these phenomena. In addition, the MRE11-promoted tumorsphere formation or cell migration ability was compromised in OSCC cells carrying siRNA that targets CD44, as was the MRE11-promoted AKT phosphorylation. These were further supported by analyzing clinical samples, where higher CD44 expression was associated with lymph node metastasis. Additionally, a positive correlation between the expression of MRE11 and CD44, or that of CD44 and phosphorylated AKT, was observed in OSCC tumor tissues. Finally, the expression of CD44 was found to be higher in the metastatic lung nodules from mice receiving tail vein-injection with MRE11-overexpressing OSCC cells compared with control mice, and a positive correlation between CD44 and phosphorylated AKT was also observed in these metastatic lung nodules. Altogether, our current study revealed a previously unidentified mechanism linking CD44 and AKT in MRE11-promoted OSCC malignancy, which may shed light to the development of novel therapeutic strategies in consideration of this new pathway in OSCC.

Reduced tissue and serum resistin expression as a clinical marker for esophageal squamous cell carcinoma.

Esophageal cancer is one of the most common malignancies and leading cause of cancer-associated mortality worldwide. However, the molecular mechanisms underlying esophageal cancer progression and the development of clinical tools for effective diagnosis remain unclear. Resistin, which was originally identified as an adipose tissue-secretory factor, has been associated with obesity-related diseases, including certain types of cancer. Thus, the present study aimed to investigate the expression levels of resistin in tissue and serum specimens from patients with esophageal squamous cell carcinoma (ESCC) to determine the potential biological effects of resistin on ESCC cells. The results demonstrated that both tissue and serum resistin levels were significantly lower in patients with ESCC compared with healthy controls. In addition, resistin expression was positively associated with the body mass index of patients with ESCC. In vitro studies revealed that resistin inhibited the migratory ability of ESCC cells, while having no effect on ESCC cell proliferation. Taken together, these results suggest that resistin may have the potential to be developed into a clinical marker for ESCC. However, further studies are required to investigate resistin receptor expression and determine the potential involvement of resistin-associated biological pathways, which may provide insight for future development of targeted therapies for resistin-mediated ESCC.

MRE11 as a molecular signature and therapeutic target for cancer treatment with radiotherapy.

MRE11, the core of the MRE11/RAD50/NBS1 complex, is one of key DNA damage response proteins. Increasing evidence suggests that its expression in cancer cells is critical to developing radioresistance; as such, MRE11 is an emerging marker for targeted radiosensitization strategies. Elevated MRE11 in tumor tissues has been associated with poor survival in patients undergoing radiotherapy, although in some cancer types, the opposite has been noted. The recent discovery of ionizing radiation-induced truncation of MRE11, which decreases its efficacy, may explain some of these paradoxical findings. The progress of research on the biological modulation of MRE11 expression is also discussed, with the potential application of small molecule or large molecule inhibitors of MRE11 for enhancing radiosensitivity. Current research has further highlighted both nuclease and non-nuclease activities of MRE11 in cancer cells treated with ionizing radiation, and differentiation between these is essential to verify the targeting effects of radiosensitizing agents. These updates clarify our understanding of how MRE11 expression may be utilized in future stratification of cancer patients for radiotherapy, and how it may be leveraged in shaping novel radiosensitization strategies.

Adipocytokines visfatin and resistin in breast cancer: Clinical relevance, biological mechanisms, and therapeutic potential.

Obesity is one of the major modifiable risk factors in breast cancer, with obese adipose tissue showing a pathological role in breast cancer development and malignancy via the release of secretory factors, such as proinflammatory cytokines and adipocytokines. The current article focuses on visfatin and resistin, two such adipocytokines that have emerged over the last two decades as leading breast cancer promoting factors in obesity. The clinical association of circulating visfatin and resistin with breast cancer and their biological mechanisms are reviewed, in addition to their role in the context of tumor-stromal interactions in the breast cancer microenvironment. Recent findings have unraveled several mediators of visfatin and resistin that are involved in the crosstalk between breast cancer cells and adipose tissue in the breast tumor microenvironment, including growth differentiation factor 15 (GDF15), interleukin 6 (IL-6), and toll-like receptor 4 (TLR4). Finally, current therapeutics targeting visfatin and resistin and their respective pathways are discussed, including future therapeutic strategies such as new drug design or neutralizing peptides that target extracellular visfatin or resistin. These hold promise in the development of novel breast cancer therapies and are of increasing relevance as the prevalence of obesity-related breast cancer increases worldwide.

Visfatin Enhances Breast Cancer Progression through CXCL1 Induction in Tumor-Associated Macrophages.

Visfatin, an adipocytokine highly expressed in breast tumor tissues, is associated with breast cancer progression. Recent studies showed that adipocytokines mediate tumor development through adipocytokine tumor-stromal interactions in the tumor microenvironment. This study focused on the interaction between one key stromal constituent-tumor-associated macrophages-and visfatin. Pretreatment of THP-1 and peripheral blood mononuclear cells (PBMCs) with recombinant visfatin resulted in M2-polarization determined by CD163 and CD206 expression. Indirect co-culture with visfatin-treated THP-1 (V-THP-1) promoted the viability, migration, tumorsphere formation, EMT, and stemness of breast cancer cells. Cytokine array identified an increased CXCL1 secretion in V-THP-1 conditioned medium and recombinant CXCL1 enhanced cell migration and invasion, which were abrogated by the CXCL1-neutralizing antibody. Additionally, visfatin induced pERK in THP-1 cells and clinical samples confirmed a positive CXCL1/pERK correlation. In an orthotopic mouse model, the tumor bioluminescent signal of luciferase-expressing MDA-MB-231 (Luc-MDA-MB-231) cells co-cultured with V-THP-1 and the expression of proliferation marker Ki67 were significantly higher than that co-cultured with THP-1. Furthermore, tail vein-injected Luc-MDA-MB-231 pretreated with V-PBMCs conditioned medium metastasized to lungs more frequently compared to control, and this was reversed by CXCL1 blocking antibody. In summary, this study demonstrated that visfatin enhanced breast cancer progression via pERK/CXCL1 induction in macrophages.

3'-hydroxy-4'-methoxy-ß-methyl-ß-nitrostyrene inhibits tumorigenesis in colorectal cancer cells through ROS-mediated DNA damage and mitochondrial dysfunction.

The ß-nitrostyrene family has been shown to suppress cell proliferation and induce apoptosis in types of various cancers. However, the mechanisms underlying the anticancer effects of ß-nitrostyrenes in colorectal cancer remain poorly understood. In this study, we synthesized a ß-nitrostyrene derivative, CYT-Rx20 (3'-hydroxy-4'-methoxy-ß-methyl-ß-nitrostyrene), and investigated its anticancer activities in human colorectal cancer cells both in vitro and in vivo. Our findings showed that treatment with CYT-Rx20 reduced cell viability and induced DNA damage in colorectal cancer cells. In addition, CYT-Rx20 induced cell cycle arrest of colorectal cancer cells at the G2/M phase and upregulated the protein expression of phospho-ERK, cyclin B1, phospho-cdc2 (Tyr15), aurora A, and aurora B, while it downregulated the expression of cdc25A and cdc25C. Furthermore, we found that CYT-Rx20 caused accumulation of intracellular reactive oxygen species (ROS) and reduction of mitochondrial membrane potential. The effects of CYT-Rx20 on cell viability, DNA damage, and mitochondrial membrane potential were reversed by pretreatment with the thiol antioxidant N-acetyl-L-cysteine (NAC), suggesting that ROS-mediated DNA damage and mitochondrial dysregulation play a critical role in these events. Finally, the nude mice xenograft study showed that CYT-Rx20 significantly reduced tumor growth of implanted colorectal cancer cells accompanied by elevated protein expression of aurora A, aurora B, γH2AX, phosphor-ERK, and MDA in the tumor tissues. Taken together, these results suggest that CYT-Rx20 may potentially be developed as a novel ß-nitrostyrene-based anticancer agent for colorectal cancer.

Extracellular Visfatin-Promoted Malignant Behavior in Breast Cancer Is Mediated Through c-Abl and STAT3 Activation.

PURPOSE: Visfatin is an adipocytokine involved in cellular metabolism, inflammation, and cancer. This study investigated the roles of extracellular visfatin in breast cancer, and explored underlying mechanisms in clinical and experimental settings. EXPERIMENTAL DESIGN: Associations of serum visfatin with clinicopathologic characteristics and patient survival were assessed with Cox regression models and Kaplan-Meier analyses. Effects of extracellular visfatin on cultured breast cancer cells were examined, followed by in vivo investigation of tumor growth and metastasis in xenograft animal models. Imatinib and Stattic were used to inhibit c-Abl and STAT3 activation, respectively. RESULTS: Breast cancer patients with high serum visfatin levels were associated with advanced tumor stage, increased tumor size and lymph node metastasis, and poor survival. Elevated phosphorylation of c-Abl and STAT3 in breast tumor tissues were correlated with high serum visfatin levels in patients. Visfatin-promoted in vitro cell viability and metastatic capability were suppressed by imatinib (c-Abl inhibitor) and Stattic (STAT3 inhibitor). Increased in vivo cell invasiveness was observed in zebrafish xenografted with visfatin-pretreated breast cancer cells. Tumor growth and lung metastasis occurred in visfatin-administered mice xenografted with breast cancer cells. Tail vein-injected mice with visfatin-pretreated breast cancer cells showed increased lung metastasis, which was suppressed by imatinib. CONCLUSIONS: Serum visfatin levels in breast cancer patients reveal potential prognostic values, and our findings that visfatin promoted breast cancer through activation of c-Abl and STAT3 may provide an important molecular basis for future design of targeted therapies that take into account different serum visfatin levels in breast cancer. Clin Cancer Res; 22(17); 4478-90. ©2016 AACR.

The synthetic ß-nitrostyrene derivative CYT-Rx20 induces breast cancer cell death and autophagy via ROS-mediated MEK/ERK pathway.

The ß-nitrostyrene family has been shown to suppress cancer cell proliferation and induce programmed cell death. However, mechanisms underlying ß-nitrostyrenes remain less evaluated. Here, we synthesized a ß-nitrostyrene derivative, CYT-Rx20, and characterized its anticancer effect and involving mechanisms in breast cancer. We found that CYT-Rx20 arrested breast cancer cells at G2/M phase and decreased cell viability by activating the caspase cascade, accompanying with increases of poly (ADP-ribose) polymerase (PARP) cleavage and γ-H2AX expression. On the other hand, up-regulation of Beclin-1, ATG5, and LC-3 was observed in CYT-Rx20-induced autophagy, which was evidently shown by transmission electron microscopy. In addition to these, CYT-Rx20-induced breast cancer cell death, intracellular reactive oxygen species (ROS) formation and expression of phospho-ERK1/2, Beclin-1, and LC-3 were significantly reversed in the presence of N-acetyl-l-cysteine (NAC), a thiol antioxidant. Furthermore, the cytotoxicity of CYT-Rx20 was enhanced by co-treatment with the autophagy inhibitor chloroquine or bafilomycin A1, suggesting that an incomplete autophagy process could deteriorate CYT-Rx20-induced cytotoxicity. In nude mice xenograft study, CYT-Rx20 significantly reduced orthotopic tumor growth. Immunohistochemical analysis revealed elevated expression of phospho-ERK1/2 and LC-3 in tumor tissues of the mice treated with CYT-Rx20. Together, we propose that CYT-Rx20 may have potential to be further developed into a ß-nitrostyrene-based anticancer compound for the treatment of breast cancer.

Identification of Id1 as a downstream effector for arsenic-promoted angiogenesis via PI3K/Akt, NF-κB and NOS signaling.

Exposure to arsenic is known to be a risk factor for various types of cancer. Apart from its carcinogenic activity, arsenic also shows promoting effects on angiogenesis, a crucial process for tumor growth. Yet, the mechanism underlying arsenic-induced angiogenesis is not fully understood. In this study, we aimed at investigating the involvement of inhibitor of DNA binding 1 (Id1) and the associated signal molecules in the arsenic-mediated angiogenesis. Our initial screening revealed that treatment with low concentrations of arsenic (0.5-1 µM) led to multiple cellular responses, including enhanced endothelial cell viability and angiogenic activity as well as increased protein expression of Id1. The arsenic-induced angiogenesis was suppressed in the Id1-knocked down cells compared to that in control cells. Furthermore, arsenic-induced Id1 expression and angiogenic activity were regulated by PI3K/Akt, NF-κB, and nitric oxide synthase (NOS) signaling. In summary, our current data demonstrate for the first time that Id1 mediates the arsenic-promoted angiogenesis, and Id1 may be regarded as an antiangiogenesis target for treatment of arsenic-associated cancer.

High Id1 expression, a generally negative prognostic factor, paradoxically predicts a favorable prognosis for adjuvant paclitaxel plus cisplatin therapy in surgically treated lung cancer patients.

Adjuvant chemotherapy is commonly given to surgically treated non-small-cell lung cancer (NSCLC) patients. However, the prerequisite for chemotherapy needs to be scrutinized in order to maximize the benefits to patients. In this study, we observed that NSCLC cells with high Id1 protein expression were vulnerable to the treatment of paclitaxel and cisplatin. In addition, paclitaxel and cisplatin caused Id1 protein degradation through ubiquitination. In the nude mice xenograft model, the tumor growth was reduced to a large degree in the Id1-overexpressing group upon treatment with paclitaxel and cisplatin. Furthermore, immunohistochemical staining for Id1 followed by Kaplan-Meier survival analysis showed that surgically treated NSCLC patients with high Id1 expression in primary tumor tissues had better disease-free and overall survivals after adjuvant paclitaxel and cisplatin chemotherapy. In summary, our current data suggest that Id1, a generally negative prognostic factor, predicts a favorable prognosis in the case of surgically treated NSCLC patients receiving the definitive adjuvant chemotherapy. The distinct role of Id1 reported in this study may arise from the phenomenon of Id1 dependence of NSCLC cells for survival, which renders the cancer cells additionally susceptive to the adjuvant chemotherapy with paclitaxel and cisplatin.

The synthetic flavonoid WYC02-9 inhibits cervical cancer cell migration/invasion and angiogenesis via MAPK14 signaling.

OBJECTIVE: Development of flavonoids as potential chemotherapeutic agents for cervical cancer may open new avenues in anticancer drug design. In this study, the cytotoxic activity and anti-migration/invasion/angiogenesis efficiency of the synthetic flavonoid WYC02-9 on cervical cancer and the underlying mechanisms are explored. METHODS: XTT cell viability assay, apoptosis assays, cell cycle analysis, and immunoblotting analysis were applied to study the biologic activity of WYC02-9. Anchorage independent soft agar assay and xenograft nude mouse model were applied to study the anti-tumor effect of WYC02-9 in vivo. Wound healing assay, transwell invasion assay, and gelatin zymography analysis were applied to study the effect of WYC02-9 on cancer cell migration and invasion. Tube formation analysis, zebrafish angiogenesis model, and nude mice Matrigel plug angiogenesis assay were applied to study the effect of WYC02-9 on angiogenesis. RESULTS: WYC02-9 induced cytotoxicity on cervical cancer cells by promoting apoptosis and G2/M cell cycle arrest. WYC02-9 inhibited cervical cancer cell migration/invasion and angiogenesis in vitro and in vivo via MAPK14 pathway. CONCLUSION: WYC02-9 significantly inhibited cervical cancer cell proliferation/migration/invasion and angiogenesis in vitro and in vivo. WYC02-9 may be a promising drug candidate for cervical cancer chemotherapy.

Role of cystatin C in amyloid precursor protein-induced proliferation of neural stem/progenitor cells.

The amyloid precursor protein (APP) is well studied for its role in Alzheimer disease. However, little is known about its normal function. In this study, we examined the role of APP in neural stem/progenitor cell (NSPC) proliferation. NSPCs derived from APP-overexpressing Tg2576 transgenic mice proliferated more rapidly than NSPCs from the corresponding background strain (C57Bl/6xSJL) wild-type mice. In contrast, NSPCs from APP knock-out (APP-KO) mice had reduced proliferation rates when compared with NSPCs from the corresponding background strain (C57Bl/6). A secreted factor, identified as cystatin C, was found to be responsible for this effect. Levels of cystatin C were higher in the Tg2576 conditioned medium and lower in the APP-KO conditioned medium. Furthermore, immunodepletion of cystatin C from the conditioned medium completely removed the ability of the conditioned medium to increase NSPC proliferation. The results demonstrate that APP expression stimulates NSPC proliferation and that this effect is mediated via an increase in cystatin C secretion.

Size and sulfation are critical for the effect of heparin on APP processing and Aß production.

Alzheimer's disease is associated with abnormal accumulation of Aß, which is produced from the ß-amyloid precursor protein (APP) by the ß-site APP-cleaving enzyme (BACE1) and γ-secretase. Our previous studies showed that heparin can decrease APP processing by decreasing the levels of BACE1 and ADAM10. In this study, we examined the effects of glycosaminoglycans (GAGs) on APP processing and Aß production with the aim of understanding the specificity of the effects. Various GAG analogs were incubated with primary cortical cells derived from APP (SW)Tg2576 mice and the level of APP, proteolytic products of APP and APP-cleavage enzymes were measured. The effect of GAGs on APP processing was both size- and sulfation-dependent. 6-O-Sulfation was important for the effect on APP processing as heparin lacking 6-O sulfate were less potent than native heparin. However, deletion of carboxyl groups on heparin had no significant effect on APP processing. Our studies suggest that there is structural specificity to the effect of GAGs on APP processing and that certain GAGs have a greater effect on Aß production than others. This suggests that it might be possible to alter the structure of GAGs to achieve more specific inhibitors of APP processing that can cross the blood-brain barrier.

Effects of heparin and enoxaparin on APP processing and Aß production in primary cortical neurons from Tg2576 mice.

BACKGROUND: Alzheimer's disease (AD) is caused by accumulation of Aß, which is produced through sequential cleavage of ß-amyloid precursor protein (APP) by the ß-site APP cleaving enzyme (BACE1) and γ-secretase. Enoxaparin, a low molecular weight form of the glycosaminoglycan (GAG) heparin, has been reported to lower Aß plaque deposition and improve cognitive function in AD transgenic mice. METHODOLOGY/PRINCIPAL FINDINGS: We examined whether heparin and enoxaparin influence APP processing and inhibit Aß production in primary cortical cell cultures. Heparin and enoxaparin were incubated with primary cortical cells derived from Tg2576 mice, and the level of APP and proteolytic products of APP (sAPPα, C99, C83 and Aß) was measured by western blotting. Treatment of the cells with heparin or enoxaparin had no significant effect on the level of total APP. However, both GAGs decreased the level of C99 and C83, and inhibited sAPPα and Aß secretion. Heparin also decreased the level of ß-secretase (BACE1) and α-secretase (ADAM10). In contrast, heparin had no effect on the level of ADAM17. CONCLUSIONS/SIGNIFICANCE: The data indicate that heparin and enoxaparin decrease APP processing via both α- and ß-secretase pathways. The possibility that GAGs may be beneficial for the treatment of AD needs further study.

Is BACE1 a suitable therapeutic target for the treatment of Alzheimer's disease? Current strategies and future directions.

Alzheimer's disease (AD) is characterized by the extracellular deposition of the beta-amyloid protein (Abeta). Abeta is a fragment of a much larger precursor protein, the amyloid precursor protein (APP). Sequential proteolytic cleavage of APP by beta-secretase and gamma-secretase liberates Abeta from APP. The aspartyl protease BACE1 (beta-site APP-cleaving enzyme 1) catalyses the rate-limiting step in the production of Abeta, and as such it is considered to be a major target for drug development in Alzheimer's disease. However, the development of a BACE1 inhibitor therapy is problematic for two reasons. First, BACE1 has been found to have important physiological roles. Therefore, inhibition of the enzyme could have toxic consequences. Second, the active site of BACE1 is relatively large, and many of the bulky compounds that are needed to inhibit BACE1 activity are unlikely to cross the blood-brain barrier. This review focuses on the structure BACE1, current therapeutic strategies based on developing active-site inhibitors, and new approaches to therapy involving targeting the expression or post-translational regulation of BACE1.

Effect of heparin on APP metabolism and Abeta production in cortical neurons.

BACKGROUND: The beta-site APP cleaving enzyme 1 (BACE1) is a major target for drug design in Alzheimer's disease. BACE1 binds strongly to heparin and other glycosaminoglycans, and there is evidence that the enzyme may interact with proteoglycans in vivo. Several studies suggest that heparin or heparan sulfate analogues may have value as therapeutic agents for the treatment of AD. OBJECTIVE: To determine whether heparin can inhibit Abeta production in cortical neurons by inhibiting BACE1. METHODS: Cortical neurons from APP (SW) Tg2576 mice were incubated with heparin and the amount of APP processing and Abeta production were measured by enzyme-linked immunosorbent assay and Western blotting. RESULTS: Treatment of cortical neurons with heparin inhibited Abeta secretion. However, this effect was not mediated via inhibition of BACE1. CONCLUSIONS: Heparin or other glycosaminoglycans may have value for the treatment of Alzheimer's disease. However, the data do not support the view that a heparin-induced decrease in Abeta secretion is due to inhibition of BACE1.

p53 mediates nitric oxide-induced apoptosis in murine neural progenitor cells.

Studies have shown that nitric oxide (NO)-induced apoptosis is mediated by a variety of cellular signaling pathways. However, the information is relatively limited to neural progenitor cells (NPCs). In this study, the role of p53 in the NO-induced apoptosis was examined in an in vitro model of NPCs. Comparisons were made between NPCs derived from either wild type or p53 knockout mice brain stimulated by diethylenetriamine/nitric oxide adduct (DETA/NO), an established NO donor that constantly releases NO through its known first order pharmacological kinetics and prolonged half-life. We found that treatment by DETA/NO both time- and dose-dependently induced a significant increase of apoptosis in wild type NPCs, while p53 knockout NPCs were resistant to the DETA/NO challenge. In addition, the DETA/NO-triggered alteration of mitochondrial membrane permeability, cleavage of caspase-9/3, and expression of pro-apoptotic Bcl-2 family members noxa and puma occurred in wild type NPCs but not in p53 knockout NPCs. Our current results suggest a central role of p53 in the NO-induced apoptotic pathway in NPCs, which may hence provide new insights into the regulation of cell death in NPCs that respond to overproduction of NO in injured brain.