[Show abstract][Hide abstract] ABSTRACT: Triple negative breast cancer (TNBC) is an aggressive form of breast cancer with no effective targeted therapy. Inducible nitric oxide synthase (iNOS) is associated with poor survival in breast cancer patients by increasing tumor aggressiveness. This work aimed to investigate the potential of iNOS inhibitors as a targeted therapy for TNBC. We hypothesized that inhibition of endogenous iNOS would decrease TNBC aggressiveness by reducing tumor initiation and metastasis through modulation of epithelial-mesenchymal transition (EMT)-inducing factors.
iNOS protein levels were determined in 83 human TNBC tissue and correlated with clinical outcome. Proliferation, mammosphere-forming efficiency, migration, EMT transcription factors were assessed in vitro after iNOS inhibition. Endogenous iNOS targeting was evaluated as potential therapy in TNBC mouse models.
High endogenous iNOS expression was associated with worse prognosis in TNBC patients by gene expression as well as immunohistochemical analysis. Selective iNOS (1400 W) and pan-NOS (L-NMMA and L-NAME) inhibitors diminished cell proliferation, cancer stem cell self-renewal, and cell migration in vitro, together with inhibition of EMT transcription factors (Snail, Slug, Twist1, and Zeb1). Impairment of hypoxia-inducible factor 1α, endoplasmic reticulum stress (IRE1α/XBP1) and the crosstalk between activating transcription factor 3 / activating transcription factor 4 and transforming growth factor β was observed. iNOS inhibition significantly reduced tumor growth, the number of lung metastases, tumor-initiation, and self-renewal.
Based on the effectiveness of L-NMMA in decreasing tumor growth and enhancing survival rate in TNBC, we propose a targeted therapeutic clinical trial by re-purposing the pan-NOS inhibitor L-NMMA, which has been extensively investigated for cardiogenic shock as an anti-cancer therapeutic.
Full-text · Article · Dec 2015 · Breast Cancer Research
[Show abstract][Hide abstract] ABSTRACT: AMP-activated protein kinase (AMPK), a critical fuel-sensing enzyme, regulates the metabolic effects of various hormones. Neurotensin (NT) is a 13-amino acid peptide predominantly localized in enteroendocrine (EE) cells of the small bowel and released by fat ingestion. Increased fasting plasma levels of pro-NT (a stable NT precursor fragment produced in equimolar amounts relative to NT) are associated with an increased risk of diabetes, cardiovascular disease and mortality; however, the mechanisms regulating NT release are not fully defined. We previously reported that inhibition of the mTOR complex 1 (mTORC1) increases NT secretion and gene expression through activation of the MEK/ERK pathway. Here, we show that activation of AMPK increases NT secretion from endocrine cell lines (BON and QGP-1) and isolated mouse crypt cells enriched for NT-positive cells. In addition, plasma levels of NT increase in mice treated with AICAR (5-aminoimidazole-4-carboxamide riboside), a pharmacologic AMPK activator. siRNA-mediated knockdown of AMPKα decrease, whereas overexpression of the subunit significantly enhances NT secretion from BON cells treated with AMPK activators or oleic acid. Similarly, siRNA knockdown of the upstream AMPK kinases, liver kinase B1 (LKB1) and Ca(2+)-calmodulin-dependent protein kinase kinase 2 (CaMKK2), also attenuate NT release and AMPK phosphorylation. Moreover, AMPK activation increases NT secretion through inhibition of mTORC1 signaling. Together, our findings show that AMPK activation enhances NT release through inhibition of mTORC1 signaling thus demonstrating an important cross-talk regulation for NT secretion.
No preview · Article · Nov 2015 · Molecular Endocrinology
[Show abstract][Hide abstract] ABSTRACT: Purpose:
Chemotherapy-induced cognitive impairment (CICI) is a common sequelae of cancer therapy. Recent preclinical observations have suggested that CICI can be mediated by chemotherapy-induced plasma protein oxidation, which triggers TNF-α mediated CNS damage. This study evaluated sodium-2-mercaptoethane sulfonate (Mesna) co-administration with doxorubicin to reduce doxorubicin-induced plasma protein oxidation and resultant cascade of TNF-α, soluble TNF receptor levels and related cytokines.
Thirty-two evaluable patients were randomized using a crossover design to receive mesna or saline in either the first or second cycle of doxorubicin in the context of a standard chemotherapy regimen for either non-Hodgkin lymphoma or breast cancer. Mesna (360 mg/m2) or saline administration occurred 15 minutes prior and three hours post doxorubicin. Pre-treatment and post-treatment measurements of oxidative stress, TNF-α and related cytokines were evaluated during the two experimental cycles of chemotherapy.
Co-administration of mesna with chemotherapy reduced post-treatment levels of TNF-related cytokines and TNF-receptor 1 (TNFR1) and TNF-receptor 2 (TNFR2) (p = 0.05 and p = 0.002, respectively). Patients with the highest pre-treatment levels of each cytokine and its receptors were the most likely to benefit from mesna co-administration.
The extracellular anti-oxidant mesna, when co-administered during a single cycle of doxorubicin, reduced levels of TNF-α and its receptors after that cycle of therapy, demonstrating for the first time a clinical interaction between mesna and doxorubicin, drugs often coincidentally co-administered in multi-agent regimens. These findings support further investigation to determine whether rationally-timed mesna co-administration with redox active chemotherapy may prevent or reduce the cascade of events that lead to CICI.
[Show abstract][Hide abstract] ABSTRACT: Fatty acid synthase (FASN), a lipogenic enzyme, is upregulated in colorectal cancer (CRC). Increased de novo lipid synthesis is thought to be a metabolic adaptation of cancer cells that promotes survival and metastasis; however, the mechanisms for this phenomenon are not fully understood. We show that FASN plays a role in regulation of energy homeostasis by enhancing cellular respiration in CRC. We demonstrate that endogenously synthesized lipids fuel fatty acid oxidation, particularly during metabolic stress, and maintain energy homeostasis. Increased FASN expression is associated with a decrease in activation of energy-sensing pathways and accumulation of lipid droplets in CRC cells and orthotopic CRCs. Immunohistochemical evaluation demonstrated increased expression of FASN and p62, a marker of autophagy inhibition, in primary CRCs and liver metastases compared to matched normal colonic mucosa. Our findings indicate that overexpression of FASN plays a crucial role in maintaining energy homeostasis in CRC via increased oxidation of endogenously synthesized lipids. Importantly, activation of fatty acid oxidation and consequent downregulation of stress-response signaling pathways may be key adaptation mechanisms that mediate the effects of FASN on cancer cell survival and metastasis, providing a strong rationale for targeting this pathway in advanced CRC.
[Show abstract][Hide abstract] ABSTRACT: Neurotensin (NTS), localized predominantly to the small bowel, stimulates the growth of a variety of cancers, including neuroendocrine tumors (NETs), mainly through its interaction with the high-affinity NTS receptor 1 (NTSR1). Here, we observed increased expression of NTSR1 in almost all tested clinical NET samples, but not in normal tissues. Through RT-PCR analysis, we found that the expression of NTSR1 and NTSR2 was either variable (NTSR1) or absent (NTSR2) in human NET cell lines. In contrast, NTSR3 and NTS were expressed in all NET cells. Treatment with 5-aza-2'-deoxycytidine, a demethylating agent, increased levels of NTSR1 and NTSR2 suggesting that DNA methylation contributes to NTSR1/2 expression patterns, which was confirmed by methylation analyses. In addition, we found that knockdown of NTSR1 decreased proliferation, expression levels of growth-related proteins, and anchorage-independent growth of BON human carcinoid cells. Moreover, stable silencing of NTSR1 suppressed BON cell growth, adhesion, migration and invasion. Our results show that high expression of NTSR1 is found in clinical NETs and that promoter methylation is an important mechanism controlling the differential expression of NTSR1 and silencing of NTSR2 in NET cells. Furthermore, knockdown of NTSR1 in BON cells suppressed oncogenic functions suggesting that NTSR1 contributes to NET tumorigenesis.
[Show abstract][Hide abstract] ABSTRACT: The intestinal mucosa undergoes a continual process of proliferation, differentiation and apoptosis, which is regulated by multiple signaling pathways. Notch signaling is critical for the control of intestinal stem cell maintenance and differentiation. However, the precise mechanisms involved in the regulation of differentiation are not fully understood. Previously, we have shown that tuberous sclerosis 2 (TSC2) positively regulates the expression of the goblet cell differentiation marker, MUC2, in intestinal cells. Using transgenic mice constitutively expressing a dominant negative TSC2 allele, we observed that TSC2 inactivation increased mTORC1 and Notch activities, and altered differentiation throughout the intestinal epithelium, with a marked decrease in the goblet and Paneth cell lineages. Conversely, treatment of mice with either Notch inhibitor dibenzazepine (DBZ) or mTORC1 inhibitor rapamycin significantly attenuated the reduction of goblet and Paneth cells. Accordingly, knockdown of TSC2 activated, whereas knockdown of mTOR or treatment with rapamycin decreased, the activity of Notch signaling in the intestinal cell line LS174T. Importantly, our findings demonstrate that TSC2/mTORC1 signaling contributes to the maintenance of intestinal epithelium homeostasis by regulating Notch activity.
Preview · Article · Feb 2015 · Cell Death & Disease
[Show abstract][Hide abstract] ABSTRACT: The majority of deaths from all cancers, including colorectal cancer (CRC), is a result of tumor metastasis to distant organs. To date, an effective and safe system capable of exclusively targeting metastatic cancers that have spread to distant organs or lymph nodes does not exist. Here, we constructed multifunctional RNA nanoparticles, derived from the three-way junction (3WJ) of bacteriophage phi29 motor pRNA, to target metastatic cancer cells in a clinically relevant mouse model of CRC metastasis. The RNA nanoparticles demonstrated metastatic tumor homing without accumulation in normal organ tissues surrounding metastatic tumors. The RNA nanoparticles simultaneously targeted CRC cancer cells in major sites of metastasis, such as liver, lymph nodes and lung. Our results demonstrate the therapeutic potential of these RNA nanoparticles as a delivery system for the treatment of CRC metastasis.
[Show abstract][Hide abstract] ABSTRACT: Autophagy is a tightly regulated lysosomal degradation pathway for maintaining cellular homeostasis and responding to stresses. Beclin 1 and its interacting proteins, including the class III phosphatidylinositol-3 kinase Vps34, play crucial roles in autophagy regulation in mammals. We identified nuclear receptor binding factor 2 (Nrbf2) as a Beclin 1-interacting protein from Becn1-/-;Becn1-EGFP/+ mouse liver and brain. We also found that Nrbf2-Beclin 1 interaction required the N-terminus of Nrbf2. We next used human retinal pigment epithelial cell line RPE-1 as a model system and showed that transiently knocking down Nrbf2 by siRNA increased autophagic flux under both nutrient-rich and starvation conditions. To investigate the mechanism by which Nrbf2 regulates autophagy, we demonstrated that Nrbf2 interacted and colocalized with Atg14L, suggesting that Nrbf2 is a component of the Atg14L-containing Beclin 1-Vps34 complex. Moreover, ectopically expressed Nrbf2 formed cytosolic puncta that were positive for isolation membrane markers. These results suggest that Nrbf2 is involved in autophagosome biogenesis. Furthermore, we showed that Nrbf2 deficiency led to increased intracellular phosphatidylinositol-3 phosphate levels as well as diminished Atg14L-Vps34/Vps15 interactions, suggesting that Nrbf2-mediated Atg14L-Vps34/Vps15 interactions likely inhibit Vps34 activity. Therefore, we propose that Nrbf2 may interact with the Atg14L-containing Beclin 1-Vps34 protein complex to modulate protein-protein interactions within the network, leading to suppression of Vps34 activity, autophagosome biogenesis and autophagic flux. This work reveals a novel aspect of the intricate mechanism for the Beclin 1-Vps34 protein-protein interaction network to achieve precise control of autophagy.
Preview · Article · Aug 2014 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: The intestinal mucosa undergoes a continual process of proliferation, differentiation and apoptosis, which is regulated by multiple signaling pathways. Previously, we have shown that the nuclear factor of activated T-cells 5 (NFAT5) is involved in the regulation of intestinal enterocyte differentiation. Here, we show that treatment with sodium chloride (NaCl), which activates NFAT5 signaling, increased mTORC1 repressor REDD1 protein expression and inhibited mTOR signaling; these alterations were attenuated by knockdown of NFAT5. Knockdown of NFAT5 activated mTOR signaling and significantly inhibited REDD1 mRNA expression and protein expression. Consistently, overexpression of NFAT5 increased REDD1 expression. In addition, knockdown of REDD1 activated mTOR and Notch signaling, whereas treatment with mTOR inhibitor rapamycin repressed Notch signaling and increased the expression of the goblet cell differentiation marker mucin2 (MUC2). Moreover, knockdown of NFAT5 activated Notch signaling and decreased MUC2 expression, while overexpression of NFAT5 inhibited Notch signaling and increased MUC2 expression. Our results demonstrate a role for NFAT5 in the regulation of mTOR signaling in intestinal cells. Importantly, these data suggest that NFAT5 participates in the regulation of intestinal homeostasis via the suppression of mTORC1/Notch signaling pathway.
Full-text · Article · Jul 2014 · Molecular Biology of the Cell
[Show abstract][Hide abstract] ABSTRACT: Background:
Targeting growth factor and survival pathways may delay endocrine-resistance in estrogen receptor-positive breast cancer.
Materials & methods:
A pilot Phase II study adding sorafenib to endocrine therapy in 11 patients with metastatic estrogen receptor-positive breast cancer was conducted. Primary end point was response by RECIST after 3 months of sorafenib. Secondary end points included safety, time to progression and biomarker modulation. The study closed early owing to slow accrual.
Eight out of 11 patients had progressive disease on study entry and three had stable disease. Of the ten evaluable patients, seven experienced stable disease (70%) and three experienced progressive diseas (30%), with a median time to progression of 6.1 months (8.4 months in the seven patients on tamoxifen). The serum samples demonstrated a significant reduction in VEGF receptor 2 and PDGF receptor-α. Microarray analysis identified 32 suppressed genes, no induced genes and 29 enriched Kyoto Encyclopedia of Genes and Genomes pathways.
The strategy of adding a targeted agent to endocrine therapy upon resistance may be worthwhile testing in larger studies.