Agelastatin A: a novel inhibitor of osteopontin-mediated adhesion, invasion, and colony formation

Effective inhibitors of osteopontin (OPN)-mediated neoplastic transformation and metastasis are still lacking. (-)-Agelastatin A is a naturally occurring oroidin alkaloid with powerful antitumor effects that, in many cases, are superior to cisplatin in vitro. In this regard, past comparative assaying of the two agents against a range of human tumor cell lines has revealed that typically (-)-agelastatin A is 1.5 to 16 times more potent than cisplatin at inhibiting cell growth, its effects being most pronounced against human bladder, skin, colon, and breast carcinomas. In this study, we have investigated the effects of (-)-agelastatin A on OPN-mediated malignant transformation using mammary epithelial cell lines. Treatment with (-)-agelastatin A inhibited OPN protein expression and enhanced expression of the cellular OPN inhibitor, Tcf-4. (-)-Agelastatin A treatment also reduced beta-catenin protein expression and reduced anchorage-independent growth, adhesion, and invasion in R37 OPN pBK-CMV and C9 cell lines. Similar effects were observed in MDA-MB-231 and MDA-MB-435s human breast cancer cell lines exposed to (-)-agelastatin A. Suppression of Tcf-4 by RNA interference (short interfering RNA) induced malignant/invasive transformation in parental benign Rama 37 cells; significantly, these events were reversed by treatment with (-)-agelastatin A. Our study reveals, for the very first time, that (-)-agelastatin A down-regulates beta-catenin expression while simultaneously up-regulating Tcf-4 and that these combined effects cause repression of OPN and inhibition of OPN-mediated malignant cell invasion, adhesion, and colony formation in vitro. We have also shown that (-)-agelastatin A inhibits cancer cell proliferation by causing cells to accumulate in the G(2) phase of cell cycle.

Atomic layer deposition of hafnium oxide dielectrics on silicon and germanium substrates

Hafnium oxide films have been deposited at 250 °C on silicon and germanium substrates by atomic layer deposition (ALD), using tetrakis-ethylmethylamino hafnium (TEMAH) and water vapour as precursors in a modified Oxford Instruments PECVD system. Self-limiting monolayer growth has been verified, characterised by a growth rate of 0.082 nm/ cycle. Layer uniformity is approximately within ±1% of the mean value. MOS capacitors have been fabricated by evaporating aluminium electrodes. CV analysis has been used to determine the bulk and interface properties of the HfO 2, and their dependence on pre-clean schedule, deposition conditions and post-deposition annealing. The dielectric constant of the HfO 2 is typically 18. On silicon, best results are obtained when the HfO 2 is deposited on a chemically oxidised hydrophilic surface. On germanium, best results are obtained when the substrate is nitrided before HfO 2 deposition, using an in-situ nitrogen plasma treatment. © Springer Science+Business Media, LLC 2007.

Fabrication of Sub-micron Active Layer SSOI Substrates using Ion Splitting and Wafer Bonding Technologies

This paper reports the fabrication of SSOI (Silicon on Silicide On Insulator) substrates with active silicon regions only 0.5mum thick, incorporating LPCVD low resistivity tungsten silicide (WSix) as the buried layer. The substrates were produced using ion splitting and two stages of wafer bonding. Scanning acoustic microscope imaging confirmed that the bond interfaces are essentially void-free. These SSOI wafers are designed to be employed as substrates for mm-wave reflect-array diodes, and the required selective etch technology is described together with details of a suitable device.

RAN GTPase is an effector of the invasive/metastatic phenotype induced by osteopontin.

Osteopontin (OPN) is a phosphorylated glycoprotein that binds to alpha v-containing integrins and is important in malignant transformation and cancer. Previously, we have utilized suppressive subtractive hybridization between mRNAs isolated from the Rama 37 (R37) rat mammary cell line and a subclone rendered invasive and metastatic by stable transfection with an expression vector for OPN to identify RAN GTPase (RAN) as the most overexpressed gene, in addition to that of OPN. Here we show that transfection of noninvasive R37 cells with an expression vector for RAN resulted in increased anchorage-independent growth, cell attachment and invasion through Matrigel in vitro, and metastasis in syngeneic rats. This induction of a malignant phenotype was induced independently of the expression of OPN, and was reversed by specifically reducing the expression of RAN using small-interfering RNAs. By using a combination of mutant protein and inhibitors, it was found that RAN signal transduction occurred through the c-Met receptor and PI3 kinase. This study therefore identifies RAN as a novel effector of OPN-mediated malignant transformation and some of its downstream signaling events in a mammary epithelial model of cancer invasion/metastasis.