Citations

The molecular mechanism of autocrine regulation of vascular endothelial growth factor (VEGF) in chronic lymphocytic leukemia (CLL) B cells is unknown. Here, we report that CLL B cells express constitutive levels of HIF-1α under normoxia. We have examined the status of the von Hippel-Lindau gene product (pVHL) that is responsible for HIF-1α degradation and found it to be at a notably low level in CLL B cells compared with normal B cells. We demonstrate that the microRNA, miR-92-1, overexpressed in CLL B cells, can target the VHL transcript to repress its expression. We found that the stabilized HIF-1α can form an active complex with the transcriptional coactivator p300 and phosphorylated-STAT3 at the VEGF promoter and recruit RNA polymerase II. This is initial evidence that pVHL, without any genetic alteration, can be regulated by microRNA and explains the aberrant autocrine VEGF secretion in CLL.

Endothelial cell proliferation and migration is essential to angiogenesis. Typically, proliferation and chemotaxis of endothelial cells is driven by growth factors such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). VEGF activates phospholipases (PLCs) – specifically PLCγ1 – that are important for tubulogenesis, differentiation and DNA synthesis. However, we show here that VEGF, specifically through VEGFR2, induces phosphorylation of two serine residues on PLCβ3, and this was confirmed in an ex vivo embryoid body model. Knockdown of PLCβ3 in HUVEC cells affects IP3 production, actin reorganization, migration and proliferation; whereas migration is inhibited, proliferation is enhanced. Our data suggest that enhanced proliferation is precipitated by an accelerated cell cycle, and decreased migration by an inability to activate CDC42. Given that PLCβ3 is typically known as an effector of heterotrimeric G-proteins, our data demonstrate a unique crosstalk between the G-protein and receptor tyrosine kinase (RTK) axes and reveal a novel molecular mechanism of VEGF signaling and, thus, angiogenesis.

Abstract Pancreatic adenocarcinoma (PCA) is an almost invariably fatal disease. Recently, it has been shown by several groups as well as ours that insulin-like growth factor-I receptor (IGF-IR) overexpression is related to higher proliferation, survival, angiogenesis, and highly invasive pancreatic tumors. Several studies have been carried out to understand the pathways that lead to growth factor–mediated signaling, but the molecular mechanism of receptor overexpression remains mostly unknown. Treatment with neutralizing antibodies or a specific kinase inhibitor against IGF-IR could block the receptor expression in PCA cells. Furthermore, we also showed that insulin receptor substrate (IRS)-2, but not IRS-1, is involved in regulation of IGF-IR expression, which is most likely not transcriptional control. By blocking mammalian target of rapamycin (mTOR) pathway with rapamycin as well as other biochemical analysis, we defined a unique regulation of IGF-IR expression mediated by protein kinase Cδ (PKCδ) and mTOR pathway. Moreover, we showed that the down-regulation of IGF-IR expression due to IRS-2 small interfering RNA can be compensated by overexpression of dominant-active mutant of PKCδ, suggesting that PKCδ is downstream of IGF-IR/IRS-2 axis. Overall, these findings suggest a novel regulatory role of IRS-2 on the expression of IGF-IR through PKCδ and mTOR in pancreatic cancer cells. [Cancer Res 2009;69(4):1350–7]

Abstract Expression of neuropilin-1 (NRP-1) has been shown in many cancer cells, but its molecular effect on tumorigenesis is largely unknown. In this report, we show that in aggressive types of renal cell carcinoma (RCC), NRP-1 is expressed at a high level. We show that after knockdown of NRP-1 by short hairpin RNA, RCC cells express significantly lower levels of MDM-2 and p63 proteins but higher levels of p53, and exhibit reduced migration and invasion. When implanted in mice, RCC cells with a reduced NRP-1 level have a statistically significant smaller tumor-forming ability than control cells. Also, NRP-1 knockdown RCC cells exhibit a more differentiated phenotype, as evidenced by the expression of epithelial-specific and kidney-specific cadherins, and the inhibition of sonic hedgehog expression participated in this effect. Inhibition of sonic hedgehog expression can be reversed by ΔNp63α overexpression. Our study reveals that NRP-1 helps maintain an undifferentiated phenotype in cancer cells. [Cancer Res 2008;68(21):8667–72]

AbstractIn vertebrates, molecular mechanisms dictate angioblasts' migration and subsequent differentiation into arteries and veins. In this study, we used a microarray screen to identify a novel member of the sucrose nonfermenting related kinase (snrk-1) family of serine/threonine kinases expressed specifically in the embryonic zebrafish vasculature and investigated its function in vivo. Using gain- and loss-of-function studies in vivo, we show that Snrk-1 plays an essential role in the migration, maintenance, and differentiation of angioblasts. The kinase function of Snrk-1 is critical for migration and maintenance, but not for the differentiation of angioblasts. In vitro, snrk-1 knockdown endothelial cells show only defects in migration. The snrk-1 gene acts downstream or parallel to notch and upstream of gridlock during artery-vein specification, and the human gene compensates for zebrafish snrk-1 knockdown, suggesting evolutionary conservation of function.

The neuropilin (Nrp)1 receptor is essential for both nervous and vascular system development. Nrp1 is unusually versatile, because it transmits both chemoattractive and repulsive signals in response to vascular endothelial growth factor (VEGF)-A and class 3 semaphorins, respectively. Both Nrp1 and VEGF receptor 2 undergo ligand-dependent endocytosis. We sought to establish the endocytic pathway of Nrp1 and to determine whether uptake is required for its signaling. Whereas Nrp1 underwent clathrin-dependent endocytosis in response to VEGFA 165 treatment, semaphorin 3C (sema3C) induced lipid raft–dependent endocytosis. The myosin VI PDZ (postsynaptic density 95, Disk large, Zona occludens-1) adaptor protein synectin was essential for Nrp1 trafficking. Sema3C failed to inhibit migration of synectin −/− endothelial cells, mirroring the lower migratory response of these cells to VEGFA 165 . These results show that the endocytic pathway of Nrp1 is determined by its ligand and that the trafficking of Nrp1 is essential for its signaling.

Abstract One of the key challenges in anticancer therapy is the toxicity and poor bioavailability of the anticancer drugs. Nanotechnology can play a pivotal role by delivering drugs in a targeted fashion to the malignant cells that will reduce the systemic toxicity of the anticancer drug. In this report, we show a stepwise development of a nanoparticle-based targeted delivery system for in vitro and in vivo therapeutic application in pancreatic cancer. In the first part of the study, we have shown the fabrication and characterization of the delivery system containing gold nanoparticle as a delivery vehicle, cetuximab as a targeting agent, and gemcitabine as an anticancer drug for in vitro application. Nanoconjugate was first characterized physico-chemically. In vitro targeting efficacy, tested against three pancreatic cancer cell lines (PANC-1, AsPC-1, and MIA Paca2) with variable epidermal growth factor receptor (EGFR) expression, showed that gold uptake correlated with EGFR expression. In the second part, we showed the in vivo therapeutic efficacy of the targeted delivery system. Administration of this targeted delivery system resulted in significant inhibition of pancreatic tumor cell proliferation in vitro and orthotopic pancreatic tumor growth in vivo. Tumor progression was monitored noninvasively by measuring bioluminescence of the implanted tumor cells. Pharmacokinetic experiments along with the quantitation of gold both in vitro and in vivo further confirmed that the inhibition of tumor growth was due to targeted delivery. This strategy could be used as a generalized approach for the treatment of a variety of cancers characterized by overexpression of EGFR. [Cancer Res 2008;68(6):1970–8]

OBJECTIVE—Muscle mitochondrial dysfunction occurs in many insulin-resistant states, such as type 2 diabetes, prompting a hypothesis that mitochondrial dysfunction may cause insulin resistance. We determined the impact of insulin deficiency on muscle mitochondrial ATP production by temporarily depriving type 1 diabetic patients of insulin treatment. RESEARCH DESIGN AND METHODS—We withdrew insulin for 8.6 ± 0.6 h in nine C-peptide–negative type 1 diabetic subjects and measured muscle mitochondrial ATP production and gene transcript levels (gene array and real-time quantitative PCR) and compared with insulin-treated state. We also measured oxygen consumption (indirect calorimetry); plasma levels of glucagon, bicarbonate, and other substrates; and urinary nitrogen. RESULTS—Withdrawal of insulin resulted in increased plasma glucose, branched chain amino acids, nonesterified fatty acids, β-hydroxybutyrate, and urinary nitrogen but no change in bicarbonate. Insulin deprivation decreased muscle mitochondrial ATP production rate (MAPR) despite an increase in whole-body oxygen consumption and altered expression of many muscle mitochondrial gene transcripts. Transcript levels of genes involved in oxidative phosphorylation were decreased, whereas those involved in vascular endothelial growth factor (VEGF) signaling, inflammation, cytoskeleton signaling, and integrin signaling pathways were increased. CONCLUSIONS—Insulin deficiency and associated metabolic changes reduce muscle MAPR and expression of oxidative phosphorylation genes in type 1 diabetes despite an increase in whole-body oxygen consumption. Increase in transcript levels of genes involved in VEGF, inflammation, cytoskeleton, and integrin signaling pathways suggest that vascular factors and cell proliferation that may interact with mitochondrial changes occurred.