bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Transitions in a Self-Assembled Ge Quantum Dot/Si Superlattice Measured by Photoreflectance Spectroscopy
Authors: Lee Chie-In , Lu Yan-Ten , Su Yan-Kuin , Chang Shoou-Jinn , Hwang Jenn-Shyong , Chang Chung-Chih
Published: September 2005

We report the first room-temperature photoreflectance (PR) measurement for self-assemble Ge quantum dot/Si superlattice grown by chemical vapor deposition (CVD) system. The relevant critical energies of transitions are obtained through fitting the PR spectrum. They are in good agreement with the result of theoretical calculations for the wetting layer with strain and a quantum dot of disk shape.
Second-Harmonic-Generation Microscopy Using Excitation Beam with Controlled Polarization Pattern to Determine Three-Dimensional Molecular Orientation
Authors: Yoshiki Keisuke , Hashimoto Mamoru , Araki Tsutomu
Published: September 2005

We have developed a second-harmonic-generation (SHG) microscope using an excitation beam with a controlled polarization pattern in order to detect three-dimensional molecular orientation. The electric field at the focus is controlled three-dimensionally by modifying the polarization distribution with a parallel-aligned nematic-liquid-crystal spatial-light-modulator without any mechanical moving parts. We demonstrated that the SHG signal from an Achilles tendon, sliced so that collagen fibers were aligned parallel to the optical axis, excited by a radially polarized beam was higher than those excited by linearly polarized beams. The possibility of determinating three-dimensional molecular orientation was thus shown.
Unidirectional Laser Emission from Spiral Microcavity Utilizing Conducting Polymer
Authors: Fujii Akihiko , Nishimura Tetsuharu , Yoshida Yuichi , Yoshino Katsumi , Ozaki Masanori
Published: September 2005

Spiral microdisks based on a conducting polymer have been fabricated on quartz substrates and their emission properties have been studied. A unidirectional red laser emission from a spiral microcavity with a poly( p-phenylenevinylene) derivative has been observed by pulsed photopumping.
Buckling Test under Axial Compression for Multiwall Carbon Nanotubes
Authors: Nishio Mitsumasa , Akita Seiji , Nakayama Yoshikazu
Published: September 2005

We have investigated buckling phenomena under axial compression for multiwall carbon nanotubes with the same outer diameter with different wall thicknesses obtained by the extraction of inner shells. According to the Euler's buckling model described by the continuum model, Young's moduli of the nanotube before and after the extraction of the inner shells were evaluated to be 0.77 and 0.80 TPa, respectively. This good agreement between the two values indicates that the classical continuum model is effective for describing the mechanical behaviors of multiwall nanotubes.
Time-Resolved Measurement of Charging on Hole Bottoms of SiO2 Wafer Exposed to Plasma Etching in a Pulsed Two-Frequency Capacitively Coupled Plasma
Authors: Ohmori Takeshi , Goto Takeshi Kamata , Kitajima Takeshi , Makabe Toshiaki
Published: September 2005

We experimentally demonstrate a time chart of the shading either of electrons or positive ions on a topologically patterned wafer exposed to plasma etching by synchronized measurements of bottom-charging potential in a SiO2 hole, current components incident on the wafer, and optical emission CT in the interface in a pulsed two frequency capacitively coupled plasma. The present paper gives a history of charging affected dynamically by an instantaneous electrical response on the bottom.
Guided Mode Lasing from Hollow Square Microcavity with Round Inner Corners
Authors: Moon Hee-Jong , Kang Dong-Yun , Hyun Kyung-Sook
Published: September 2005

We propose guided modes in a hollow square microcavity having round inner corners and investigate the characteristics of these guided modes using a ray-optics model, in which the guided modes are formed by the total internal reflection of light at inner and outer flat boundaries. For a given order of guided modes, the optical path length decreases linearly as the thickness of the hollow square cavity decreases at a fixed outer size. The slope of variation in the optical path length increases with the mode order. Multiple mode orders can be realized with fixed inner and outer sizes by adjusting the curvature radius of round inner corners. We experimentally demonstrated the lasing of the proposed guided modes by using an inner-etched thin square capillary.
Novel Discharge Logic Gate for Reducing the Number of Scanning Drive Circuits of Plasma Display Panel
Authors: Ryeom Jeongduk
Published: September 2005

A new discharge logic gate plasma display panel for the cost reduction of circuitry is proposed. A DC discharge NOT-AND gate that executes horizontal scanning is installed in the surroundings of the panel. The address discharge is induced by the output discharge of the logic gate, which is called DC–AC floating discharge. A driving experiment with the test plasma display panel that uses this discharge logic gate technology is performed. From the results, the operation of the discharge logic gate is verified and a maximum addressing margin of about 70 V is obtained.
High-Critical-Temperature Sm- and Nd-Based Superconductors Produced by Metal Organic Deposition Using Trifluoroacetates and Pentafluoropropionates
Authors: Araki Takeshi , Hirabayashi Izumi
Published: September 2005

Superconducting films for wire, tape, and microwave filter applications require a high critical temperature (Tc) and current density (Jc). Therefore, superconducting systems based on La, Nd, and Sm produced by low-cost non-vacuum metal organic deposition using trifluoroacetates (TFA-MOD) are eagerly awaited. These systems are reported to have excellentTcvalues of over 94 K, but esterification between trifluoroacetates and methanol leads to lowTcvalues in the TFA-MOD process. Two recent studies on carbon expulsion during calcining and on a quasi-liquid network model during firing suggest new effective chemicals and we successfully prepared Nd- and Sm-based superconductors using pentafluoropropionic acid. The best Nd- and Sm-based films exhibitedTcof 93.4 and 93.9 K andJcof 3.4 and 5.1 MA/cm2(77 K, 0 T), as measured by the inductive method, respectively. The film thicknesses were 133 and 181 nm, respectively.
Preparation of VO2 Films with Metal–Insulator Transition on Sapphire and Silicon Substrates by Inductively Coupled Plasma-Assisted Sputtering
Authors: Okimura Kunio , Kubo Naotaka
Published: September 2005

We have achieved single phase crystalline VO2 film growth on sapphire (0001) and Si(100) substrates by the introduction of inductively coupled plasma (ICP)-assisted sputtering with an internal coil. The VO2 film on Si substrate showed a metal–insulater (M–I) transition at a temperature of 60°C with three orders of change in resistivity, with a small hysteresis width of 2.2°C for temperature. On the other hand, we could not eliminate vanadium oxides with excess oxygen such as V2O5 and V3O7 from stoichiometric VO2 in conventional reactive magnetron sputtering, regardless of the control maintained over the deposition conditions. The growth of VO2 film under a relatively wide range of deposition conditions in ICP-assisted sputtering is expected to aid in the development of integrated devices based on the M–I transition that is due to strong electron correlation.
Microwave-Excited High-Density Plasma Column Sustained along Metal Rod at Negative Voltage
Authors: Kousaka Hiroyuki , Umehara Noritsugu , Ono Kouichi , Xu Junqi
Published: September 2005

We have studied the mechanism of a microwave-excited plasma column sustained along a graphite rod at a negative voltage. It was confirmed that an Ar plasma column is extended longer along the rod axis by increasing the negative voltage. Langmuir probe measurement showed that the electron density was higher than 1011 cm-3 at a gas pressure of 4.5 Pa with an incident microwave power of 200 W and a negative voltage of -240 V. Significantly localized electromagnetic fields were detected near the rod surface, indicating that surface waves propagated along the axis of the conductive (or nondielectric) graphite rod.
Synthesis of Carbon Nanocoils by Two-step Growth Method Using Microwave Plasma-Enhanced Chemical Vapor Deposition
Authors: Tanaka Kei , Yoshimura Masamichi , Okamoto Atsuto , Ueda Kazuyuki
Published: September 2005

Carbon nanocoils (CNCs) have been synthesized by a two-step growth method using microwave plasma-enhanced chemical vapor deposition (MPECVD). At the first growth step, Si nanorods are grown on the Si substrate covered with a PtPd thin film of 2 nm thickness. At the second growth step, an Fe thin film of 1 nm thickness is deposited on the nanorods and the CNCs are successfully synthesized by MPECVD. The CNCs are grown together with carbon nanotubes (CNTs), and the yield of CNCs is about 10%. The mechanism underlying coil formation is explained by the anisotropy of incident ion flux into the deposited Fe catalyst on the nanorods.
Implementation of Tapered Multimode Interference Lightwave Combiner on Silicon-on-Insulator Substrate with Negligible Back-Reflection
Authors: Wu Zhigang , Nakamura Kazuhiko , Honda Soichiro , Utaka Katsuyuki , Edura Tomohiko , Tsutsui Ken , Wada Yasuo
Published: September 2005

We fabricated and experimentally evaluated 2×1 tapered multimode interference (MMI) combiners on silicon-on-insulator (SOI) substrates. The tapered MMI combiner we previously proposed is expected to be free from the reflection problem usually existed in a conventional rectangular MMI coupler, and such a negligible back-reflection property was actually verified. As one of its applications, we implemented a Mach–Zehnder (MZ) modulator using the tapered MMI combiner, which is often equipped with semiconductor optical amplifiers (SOAs) for ultrahigh-speed photonic switching devices and those SOAs are quite sensitive to the back-reflection.
Terahertz Near-Field Imaging Using Enhanced Transmission through a Single Subwavelength Aperture
Authors: Ishihara Kunihiko , Ikari Tomofumi , Minamide Hiroaki , Shikata Jun-ichi , Ohashi Keishi , Yokoyama Hiroyuki , Ito Hiromasa
Published: September 2005

We demonstrate terahertz (THz) near-field imaging using resonantly enhanced transmission of THz-wave radiation (λ∼200 µm) through a bull's eye structure (a single subwavelength aperture surrounded by concentric periodic grooves in a metal plate). The bull's eye structure shows extremely large enhanced transmission, which has the advantage for a single subwavelength aperture. The spatial resolution for the bull's eye structure (with an aperture diameterd=100 µm) is evaluated in the near-field region, and a resolution of 50 µm (corresponding to λ/4) is achieved. We obtain the THz near-field images of the subwavelength metal pattern with a spatial resolution below the diffraction limit.
Heat shock-induced attenuation of hydroxyl radical generation and mitochondrial aconitase activity in cardiac H9c2 cells
Authors: Ilangovan Govindasamy , Venkatakrishnan C. D. , Bratasz Anna , Osinbowale Sola , Cardounel Arturo J. , Zweier Jay L. , Kuppusamy Periannan
Published: September 2005

A mild heat shock (hyperthermia) protects cells from apoptotic and necrotic deaths by inducing overexpression of various heat shock proteins (Hsps). These proteins, in combination with the activation of the nitric oxide synthase (NOS) enzyme, play important roles in the protection of the myocardium against a variety of diseases. In the present work we report that the generation of potent reactive oxygen species (ROS), namely ·OH in cardiac H9c2 cells, is attenuated by heat shock treatment (2 h at 42°C). Western blot analyses showed that heat shock treatment induced overexpression of Hsp70, Hsp60, and Hsp25. The observed ·OH was found to be derived from the superoxide (O2−·) generated by the mitochondria. Whereas the manganese superoxide dismutase (MnSOD) activity was increased in the heat-shocked cells, the mitochondrial aconitase activity was reduced. The mechanism of O2−· conversion into ·OH in mitochondria is proposed as follows. The O2−· leaked from the electron transport chain, oxidatively damages the mitochondrial aconitase, releasing a free Fe2+. The aconitase-released Fe2+ combines with H2O2 to generate ·OH via a Fenton reaction and the oxidized Fe3+ recombines with the inactivated enzyme after being reduced to Fe2+ by other cellular reductants, turning it over to be active. However, in heat-shocked cells, because of higher MnSOD activity, the excess H2O2 causes irreversible damage to the mitochondrial aconitase enzyme, thus inhibiting its activity. In conclusion, we propose that attenuation of ·OH generation after heat shock treatment might play an important role in reducing the myocardial ischemic injury, observed in heat shock-treated animals.
Impact of caveolin-1 knockout on NANC relaxation in circular muscles of the mouse small intestine compared with longitudinal muscles
Authors: El-Yazbi Ahmed F. , Cho Woo Jung , Boddy Geoffrey , Schulz Richard , Daniel Edwin E.
Published: September 2005

Recently, we showed that caveolin-1 (cav1) knockout mice (Cav1−/− mice) have impaired nitric oxide (NO) function in the longitudinal muscle (LM) layer of the small intestine. The defect was a reduced responsiveness of the muscles to NO compensated by an increase in the function of apamin-sensitive, nonadrenergic, noncholinergic (NANC) mediators. In the present study, we examined similarly the effects of cav1 knockout on the relaxation in circular muscle (CM) of the mouse small intestine. CM of Cav1−/− mice also showed defective NO function, but less than in LM, as well as more activation of apamin-sensitive NANC mediators. CM of Cav1−/− mice, like LM, lacked cav1 but retained small amounts of cav3 and caveolae in the outer CM layer. In addition, we also examined the effects of a soluble guanylate cyclase inhibitor, 1 H-[1,2,4]oxadiazolo-[4,3-α]quinazolin-1-one (ODQ), on electric field stimulation (EFS)-mediated relaxation in both LM and CM. ODQ had an effect similar to the block of NO synthesis. Moreover, we compared the actions of two NO donors in the LM and CM of control and Cav1−/− mice. Similar to LM, CM of Cav1−/− mice showed a reduced responsiveness to the NO donors sodium nitroprusside and S-nitroso- N-acetyl penicillamine. However, both ODQ and apamin blocked the inhibitory effects of the NO donors in LM, whereas apamin had no effect in CM. In conclusion, cav1 knockout affects NO function in both LM and CM, but its effects in CM differ significantly.
An Extrasynaptic GABAA Receptor Mediates Tonic Inhibition in Thalamic VB Neurons
Authors: Jia Fan , Pignataro Leonardo , Schofield Claude M. , Yue Minerva , Harrison Neil L. , Goldstein Peter A.
Published: September 2005

Whole cell patch-clamp recordings were obtained from thalamic ventrobasal (VB) and reticular (RTN) neurons in mouse brain slices. A bicuculline-sensitive tonic current was observed in VB, but not in RTN, neurons; this current was increased by the GABAA receptor agonist 4,5,6,7-tetrahydroisothiazolo-[5,4-c]pyridine-3-ol (THIP; 0.1 μM) and decreased by Zn2+ (50 μM) but was unaffected by zolpidem (0.3 μM) or midazolam (0.2 μM). The pharmacological profile of the tonic current is consistent with its generation by activation of GABAA receptors that do not contain the α1 or γ2 subunits. GABAA receptors expressed in HEK 293 cells that contained α4β2δ subunits showed higher sensitivity to THIP (gaboxadol) and GABA than did receptors made up from α1β2δ, α4β2γ2s, or α1β2γ2s subunits. Western blot analysis revealed that there is little, if any, α3 or α5 subunit protein in VB. In addition, co-immunoprecipitation studies showed that antibodies to the δ subunit could precipitate α4, but not α1 subunit protein. Confocal microscopy of thalamic neurons grown in culture confirmed that α4 and δ subunits are extensively co-localized with one another and are found predominantly, but not exclusively, at extrasynaptic sites. We conclude that thalamic VB neurons express extrasynaptic GABAA receptors that are highly sensitive to GABA and THIP and that these receptors are most likely made up of α4β2δ subunits. In view of the critical role of thalamic neurons in the generation of oscillatory activity associated with sleep, these receptors may represent a principal site of action for the novel hypnotic agent gaboxadol.
Gefitinib (“Iressa”, ZD1839), an Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor, Reverses Breast Cancer Resistance Protein/ABCG2–Mediated Drug Resistance
Authors: Nakamura Yoichi , Oka Mikio , Soda Hiroshi , Shiozawa Ken , Yoshikawa Megumi , Itoh Akiko , Ikegami Yoji , Tsurutani Junji , Nakatomi Katsumi , Kitazaki Takeshi , Doi Seiji , Yoshida Hisahiro , Kohno Shigeru
Published: September 2005

Gefitinib (“Iressa”, ZD1839) is an orally active, selective epidermal growth factor receptor tyrosine kinase inhibitor, and the single agent is clinically effective in non–small cell lung cancer. Although gefitinib combined with various cytotoxic agents has been reported to enhance cytotoxicity in vitro and in mouse models, the mechanism remains undetermined. Here, to explore the mechanism with topoisomerase I inhibitors, we focused on the efflux pump of the breast cancer resistance protein (BCRP/ABCG2), and then examined whether gefitinib restored drug sensitivity in multidrug-resistant cancer cells overexpressing BCRP. We used PC-6 human small cell lung cancer cells and multidrug-resistant PC-6/SN2-5H cells selected with SN-38 of the active metabolite of irinotecan, and BCRP-overexpressing MCF-7/MX cells selected with mitoxantrone and BCRP cDNA transfectant MCF-7/clone 8 cells. Drug sensitivity against anticancer drugs was determined by tetrazolium dye assay, and intracellular topotecan accumulation by FACScan. The topotecan transport study was done using the plasma membrane vesicles of PC-6/SN2-5H cells. The resistant PC-6/SN2-5H cells overexpressed BCRP but not epidermal growth factor receptor mRNA. Ten micromoles of gefitinib reversed topotecan, SN-38, and mitoxantrone resistance, and increased the intracellular topotecan accumulation in the resistant cells but not in the parental cells. Furthermore, gefitinib inhibited the topotecan transport into the vesicles, and the Ki value was 1.01 ± 0.09 μmol/L in the Dixon plot analysis, indicating direct inhibition of BCRP by gefitinib. However, gefitinib was not transported into the vesicles with the high-performance liquid chromatography method. These results indicate that gefitinib reverses BCRP-mediated drug resistance by direct inhibition other than competitive inhibition as a BCRP substrate. Combination of gefitinib and topoisomerase I inhibitors could be clinically effective in cancers expressing BCRP.
Tid-1 Interacts with the von Hippel-Lindau Protein and Modulates Angiogenesis by Destabilization of HIF-1α
Authors: Bae Moon-Kyoung , Jeong Joo-Won , Kim Se-Hee , Kim Soo-Young , Kang Hye Jin , Kim Dong-Min , Bae Soo-Kyung , Yun Il , Trentin Grace A. , Rozakis-Adcock Maria , Kim Kyu-Won
Published: September 2005

The von Hippel-Lindau protein (pVHL) is a major tumor suppressor protein and also associated with the inhibition of angiogenesis via HIF-1α ubiquitination and proteasomal degradation. To further elucidate the biological activity of pVHL in angiogenesis, pVHL-interacting proteins were screened using the yeast two-hybrid system. We found that a mouse homologue of the long form of Drosophila tumor suppressor l(2)tid, Tid-1L, directly interacts with pVHL in vitro and in vivo. Furthermore, Tid-1L protein; enhanced the interaction between HIF-1α and pVHL, leading to the destabilization of HIF-1α protein; therefore, Tid-1L protein decreased vascular endothelial growth factor expression and inhibited angiogenesis in vivo and in vitro. These findings propose that Tid-1L may play a critical role in pVHL-mediated tumor suppression by modulating the pVHL-dependent HIF-1α stability.
Individual Variation of Somatic Gene Mutability in Relation to Cancer Susceptibility: Prospective Study on Erythrocyte Glycophorin A Gene Mutations of Atomic Bomb Survivors
Authors: Kyoizumi Seishi , Kusunoki Yoichiro , Hayashi Tomonori , Hakoda Masayuki , Cologne John B. , Nakachi Kei
Published: September 2005

It has previously been reported that hemizygous mutant fraction (Mf) at the glycophorin A (GPA) locus in erythrocytes increased with radiation dose in heterozygotes among Hiroshima and Nagasaki atomic bomb survivors. In the present study, we analyzed the relationship between GPA Mf and cancer risk using newly developed cancers among previously cancer-free subjects whose GPA Mf had been measured between 1988 and 1996. Among 1,723 survivors (1,117 in Hiroshima and 606 in Nagasaki), we identified 186 subjects who developed a first cancer by the end of 2000. We compared the radiation dose responses of GPA Mf between cancer and cancer-free groups using a linear-quadratic model fit by multiple regression analysis in combination with age, sex, and city. The slope of the GPA Mf dose-response curve was significantly higher in the cancer group than in the cancer-free group among Hiroshima subjects. Moreover, no significant difference of GPA Mf between cancer and cancer-free groups was found in unexposed controls in the two cities. The same conclusions were obtained using a linear dose-response model and by further analysis using Cox regression of cancer incidence. These findings suggest that there might be interindividual variation in mutability of somatic genes and that Hiroshima survivors who have higher mutability in response to radiation exposure would be expected to have a higher probability of suffering radiation-related cancer.
Increased Expression of the E3-Ubiquitin Ligase Receptor Subunit βTRCP1 Relates to Constitutive Nuclear Factor-κB Activation and Chemoresistance in Pancreatic Carcinoma Cells
Authors: Müerköster Susanne , Arlt Alexander , Sipos Bence , Witt Maike , Großmann Maike , Klöppel Günter , Kalthoff Holger , Fölsch Ulrich R. , Schäfer Heiner
Published: September 2005

The permanent activation of the transcription factor nuclear factor-κB (NF-κB) in pancreatic cancer cells is associated with a profound resistance towards chemotherapy. In the present study, we show that chemoresistant pancreatic cancer cell lines exhibiting constitutive NF-κB activity (i.e., PancTu-1, BxPc3, and Capan-1) express significantly elevated levels of the E3-ubiquitin ligase receptor subunit βTRCP1, compared with pancreatic carcinoma cell lines lacking constitutive NF-κB activity and chemoresistance (i.e., PT45-P1 and T3M4). If transfected with βTRCP1, PT45-P1 cells exhibit an elevated NF-κB activity and become less sensitive towards anticancer drug treatment (i.e., etoposide). Conversely, blockade of βTRCP1 expression in PancTu-1 cells by transfection with a vector-expressed small interfering RNA reduces NF-κB activation and chemoresistance. In PancTu-1 cells, βTRCP1 expression is inhibited, at least in part, by the interleukin-1 (IL-1) receptor(I) antagonist, whereas stimulation of PT45-P1 cells with IL-1β resulted in an increased expression of βTRCP1, and transfection of this cell line with βTRCP1 induced IL-1β secretion in a NF-κB–dependent fashion. Thus, via its close and mutual link to IL-1β secretion, βTRCP1 expression might substantially contribute to the persistent, IL-1β–dependent activation of NF-κB in pancreatic carcinoma cells. In support of this, βTRCP1 expression is detectable at considerable levels in a great number of pancreatic ductal adenocarcinoma specimens, along with an intense staining for activated NF-κB. Altogether, our findings of the elevated βTRCP1 expression in pancreatic carcinoma cells pinpoint to another important mediator of constitutive NF-κB activation and thereby of chemoresistance.
Elevated Serum Levels of Stromal-Derived Factor-1α Are Associated with Increased Osteoclast Activity and Osteolytic Bone Disease in Multiple Myeloma Patients
Authors: Zannettino Andrew C.W. , Farrugia Amanda N. , Kortesidis Angela , Manavis Jim , To L. Bik , Martin Sally K. , Diamond Peter , Tamamura Hirokazu , Lapidot Tsvee , Fujii Nobutaka , Gronthos Stan
Published: September 2005

Multiple myeloma (MM) is an incurable plasma cell (PC) malignancy able to mediate massive destruction of the axial and craniofacial skeleton. The aim of this study was to investigate the role of the potent chemokine, stromal-derived factor-1α (SDF-1α) in the recruitment of osteoclast precursors to the bone marrow. Our studies show that MM PC produce significant levels of SDF-1α protein and exhibit elevated plasma levels of SDF-1α when compared with normal, age-matched subjects. The level of SDF-1α positively correlated with the presence of multiple radiological bone lesions in individuals with MM, suggesting a potential role for SDF-1α in osteoclast precursor recruitment and activation. To examine this further, peripheral blood–derived CD14+ osteoclast precursors were cultured in an in vitro osteoclast-potentiating culture system in the presence of recombinant human SDF-1α. Although failing to stimulate an increase in TRAP+, multinucleated osteoclast formation, our studies show that SDF-1α mediated a dramatic increase in both the number and the size of the resorption lacunae formed. The increased osteoclast motility and activation in response to SDF-1α was associated with an increase in the expression of a number of osteoclast activation–related genes, including RANKL, RANK, TRAP, MMP-9, CA-II, and Cathepsin K. Importantly, the small-molecule CXCR4-specific inhibitor, 4F-Benzoyl-TE14011 (T140), effectively blocked osteoclast formation stimulated by the myeloma cell line, RPMI-8226. Based on these findings, we believe that the synthesis of high levels of SDF-1α by MM PC may serve to recruit osteoclast precursors to local sites within the bone marrow and enhance their motility and bone-resorbing activity. Therefore, we propose that inhibition of the CXCR4-SDF-1α axis may provide an effective means of treatment for MM-induced osteolysis.
Flavonoid Structure-Activity Studies Identify 6-Prenylchrysin and Tectochrysin as Potent and Specific Inhibitors of Breast Cancer Resistance Protein ABCG2
Authors: Ahmed-Belkacem Abdelhakim , Pozza Alexandre , Muñoz-Martínez Francisco , Bates Susan E. , Castanys Santiago , Gamarro Francisco , Di Pietro Attilio , Pérez-Victoria José M.
Published: September 2005

Overexpression of breast cancer resistance protein ABCG2 confers multidrug resistance in cancer cells. The GF120918-sensitive drug efflux activity of human wild-type (R482) ABCG2-transfected cells was used for rational screening of inhibitory flavonoids and establishment of structure-activity relationships. Flavones were found more efficient than flavonols, isoflavones, and flavanones. Differentially substituted flavone derivatives indicated positive OH effects at position 5, in contrast to positions 3 and 7. A methoxy at position 7 was slightly positive in tectochrysin, whereas a strong positive effect was produced by prenylation at position 6. The potency of 6-prenylchrysin was comparable with that of GF120918 (IC50 = 0.3 μmol/L). Both 6-prenylchrysin and tectochrysin seemed specific for ABCG2 because no interaction was detected with either P-glycoprotein or MRP1. The ABCG2 resistance profile in vitro is altered by mutation at amino acid 482. The R482T mutation limited the effect of prenylation on ABCG2 inhibition. Whereas GF120918 strongly inhibited the ATPase activity of wild-type ABCG2, neither 6-prenylchrysin nor tectochrysin altered the activity. In contrast, all three inhibitors stimulated the ATPase activity of mutant ABCG2. 6-Prenylchrysin at 0.5 μmol/L efficiently sensitized the growth of wild-type ABCG2-transfected cells to mitoxantrone, whereas higher concentrations were required for the mutant ones. In contrast, 1 μmol/L tectochrysin was sufficient to fully sensitize mutant ABCG2-transfected cells, whereas higher concentrations were required for the wild-type ones. Both flavones exhibited a lower intrinsic cytotoxicity than GF120918 and were apparently not transported by ABCG2. 6-Prenylchrysin and tectochrysin therefore constitute new and promising inhibitors for the reversal of ABCG2-mediated drug transport.
Altered IFNγ Signaling and Preserved Susceptibility to Activated Natural Killer Cell–Mediated Lysis of BCR/ABL Targets
Authors: Cebo Christelle , Voutsadakis Ioannis A. , Da Rocha Sylvie , Bourhis Jean-Henri , Jalil Abdelali , Azzarone Bruno , Turhan Ali G. , Chelbi-Alix Mounira , Chouaib Salem , Caignard Anne
Published: September 2005

Previous studies have shown that BCR/ABL oncogene, the molecular counterpart of the Ph1 chromosome, could represent a privileged target to natural killer (NK) cells. In the present study, we showed that activated peripheral NK cells killed high-level BCR/ABL transfectant UT-7/9 derived from the pluripotent hematopoietic cell line UT-7 with a high efficiency. To further define the mechanisms controlling BCR/ABL target susceptibility to NK-mediated lysis, we studied the effect of IFNγ, a key cytokine secreted by activated NK cells, on the lysis of these targets. Treatment of UT-7, UT-7/neo, and low BCR/ABL transfectant UT-7/E8 cells with IFNγ resulted in a dramatic induction of human leukocyte antigen class I (HLA-I) molecules and subsequently in their reduced susceptibility to NK-mediated cytolysis likely as a consequence of inhibitory NK receptors engagement. In contrast, such treatment neither affected HLA-I expression on transfectants expressing high level of BCR/ABL (UT-7/9) nor modulated their lysis by NK cells. Our data further show that the high-level BCR/ABL in UT-7/9 cells display an altered IFNγ signaling, as evidenced by a decrease in IFN regulatory factor-1 (IRF-1) and signal transducers and activators of transcription (STAT) 1 induction and activation in response to IFNγ, whereas this pathway is normal in UT-7 and UT-7/E8 cells. A decreased HLA-I induction and nuclear phospho-STAT1 nuclear translocation were also observed in blasts from most chronic myelogenous leukemia patients in response to IFNγ. These results outline the crucial role of IFNγ in the control of target cell susceptibility to lysis by activated NK cells and indicate that the altered response to IFNγ in BCR/ABL targets may preserve these cells from the cytokine-induced negative regulatory effect on their susceptibility to NK-mediated lysis.
The Androgen Derivative 5α-Androstane-3β,17β-Diol Inhibits Prostate Cancer Cell Migration Through Activation of the Estrogen Receptor β Subtype
Authors: Guerini Vittoria , Sau Daniela , Scaccianoce Eugenia , Rusmini Paola , Ciana Paolo , Maggi Adriana , Martini Paolo G.V. , Katzenellenbogen Benita S. , Martini Luciano , Motta Marcella , Poletti Angelo
Published: September 2005

Prostate cancer growth depends, in its earlier stages, on androgens and is usually pharmacologically modulated with androgen blockade. However, androgen-ablation therapy may generate androgen-independent prostate cancer, often characterized by an increased invasiveness. We have found that the 5α-reduced testosterone derivative, dihydrotestosterone (the most potent natural androgen) inhibits cell migration with an androgen receptor–independent mechanism. We have shown that the dihydrotestosterone metabolite 5α-androstane-3β,17β-diol (3β-Adiol), a steroid which does not bind androgen receptors, but efficiently binds the estrogen receptor β (ERβ), exerts a potent inhibition of prostate cancer cell migration through the activation of the ERβ signaling. Very surprisingly, estradiol is not active, suggesting the existence of different pathways for ERβ activation in prostate cancer cells. Moreover, 3β-Adiol, through ERβ, induces the expression of E-cadherin, a protein known to be capable of blocking metastasis formation in breast and prostate cancer cells. The inhibitory effects of 3β-Adiol on prostate cancer cell migration is counteracted by short interfering RNA against E-cadherin. Altogether, the data showed that (a) circulating testosterone may act with estrogenic effects downstream in the catabolic process present in the prostate, and (b) that the estrogenic effect of testosterone derivatives (ERβ-dependent) results in the inhibition of cell migration, although it is apparently different from that linked to estradiol on the same receptor and may be protective against prostate cancer invasion and metastasis. These results also shed some light on clinical observations suggesting that alterations in genes coding for 3β-hydroxysteroid dehydrogenases (the enzymes responsible for 3β-Adiol formation) are strongly correlated with hereditary prostate cancer.
Identification of Src-Specific Phosphorylation Site on Focal Adhesion Kinase: Dissection of the Role of Src SH2 and Catalytic Functions and Their Consequences for Tumor Cell Behavior
Authors: Brunton Valerie G. , Avizienyte Egle , Fincham Valerie J. , Serrels Bryan , Metcalf Chester A. , Sawyer Tomi K. , Frame Margaret C.
Published: September 2005

Src tyrosine kinase expression and activity are elevated during colon cancer progression. How this contributes to the malignant phenotype is not fully understood. We show that in KM12C colon carcinoma cells, expression of kinase-deficient Src proteins (SrcMF and Src251) does not alter cell growth. Src kinase activity is required for turnover of cell-matrix adhesions and, in particular, the Src-dependent phosphorylation of focal adhesion kinase (FAK) is required for their disassembly. Surprisingly, we found that expression of SrcMF or Src251 resulted in increased tyrosine phosphorylation of FAK on Tyr407, Tyr576, Tyr577, and Tyr861, which are considered to be Src kinase substrates. This Src kinase–independent phosphorylation of FAK required an intact Src SH2 domain that mediates association of Src and FAK at peripheral adhesions. Use of a novel highly potent and selective Src kinase inhibitor AP23464 combined with experiments in Src/Fyn/Yes–deficient fibroblasts showed that increased phosphorylation of FAK in cells expressing SrcMF did not require Src-like kinases. However, specific phosphorylation on Tyr925 of FAK was not evident in SrcMF- or Src251-expressing cells, and lack of Src kinase–dependent phosphorylation on this site was associated with impaired adhesion turnover. Our data show that Src kinase activity is required for adhesion turnover associated with cell migration in cancer cells and that, in addition to the catalytic activity, Src also acts as an adaptor to recruit other kinases that can phosphorylate key substrates including FAK. These studies have implications for tumor progression with respect to the use of Src kinase inhibitors.
Expression and Nuclear Location of the Transcriptional Repressor Kaiso Is Regulated by the Tumor Microenvironment
Authors: Soubry Adelheid , van Hengel Jolanda , Parthoens Eef , Colpaert Cecile , Van Marck Eric , Waltregny David , Reynolds Albert B. , van Roy Frans
Published: September 2005

Kaiso is a BTB/POZ zinc finger protein originally described as an interaction partner of p120ctn. In cultured cell lines, Kaiso is found almost exclusively in the nucleus, where it generally acts as a transcriptional repressor. Here, we describe the first in situ immunolocalization studies of Kaiso expression in normal and cancerous tissues. Surprisingly, we found striking differences between its behavior in monolayers of different cell lines, three-dimensional cell culture systems, and in vivo. Although nuclear localization was sometimes observed in tissues, Kaiso was more often found in the cytoplasm, and in some cell types it was absent. In general, Kaiso and p120ctn did not colocalize in the nucleus. To examine this phenomenon more carefully, tumor cells exhibiting strong nuclear Kaiso staining in vitro were injected into nude mice and grown as xenografts. The latter showed a progressive translocation of Kaiso towards the cytoplasm over time, and even complete loss of expression, especially in the center of the tumor nodules. When xenografted tumors were returned to cell culture, Kaiso was re-expressed and was once again found in the nucleus. Translocation of Kaiso to the cytoplasm and down-regulation of its levels were also observed under particular experimental conditions in vitro, such as formation of spheroids and acini. These data strongly imply an unexpected influence of the microenvironment on Kaiso expression and localization. As transcriptional repression is a nuclear event, this phenomenon is likely a crucial factor in the regulation of Kaiso function.
Extensive Chromosomal Instability in Rad51d-Deficient Mouse Cells
Authors: Smiraldo Phillip G. , Gruver Aaron M. , Osborn Joshua C. , Pittman Douglas L.
Published: September 2005

Homologous recombination is a double-strand break repair pathway required for resistance to DNA damage and maintaining genomic integrity. In mitotically dividing vertebrate cells, the primary proteins involved in homologous recombination repair are RAD51 and the five RAD51 paralogs, RAD51B, RAD51C, RAD51D, XRCC2, and XRCC3. In the absence of Rad51d, human and mouse cells fail to proliferate, and mice defective for Rad51d die before birth, likely as a result of genomic instability and p53 activation. Here, we report that a p53 deletion is sufficient to extend the life span of Rad51d-deficient embryos by up to 6 days and rescue the cell lethal phenotype. The Rad51d−/− Trp53−/− mouse embryo–derived fibroblasts were sensitive to DNA-damaging agents, particularly interstrand cross-links, and exhibited extensive chromosome instability including aneuploidy, chromosome fragments, deletions, and complex rearrangements. Additionally, loss of Rad51d resulted in increased centrosome fragmentation and reduced levels of radiation-induced RAD51-focus formation. Spontaneous frequencies of sister chromatid exchange were not affected by the absence of Rad51d, but sister chromatid exchange frequencies did fail to be induced upon challenge with the DNA cross-linking agent mitomycin C. These findings support a crucial role for mammalian RAD51D in normal development, recombination, and maintaining mammalian genome stability.
Epidermal Expression of the Translation Inhibitor Programmed Cell Death 4 Suppresses Tumorigenesis
Authors: Jansen Aaron P. , Camalier Corinne E. , Colburn Nancy H.
Published: September 2005

Programmed cell death 4 (Pdcd4) is a novel repressor of in vitro transformation. Pdcd4 directly inhibits the helicase activity of eukaryotic translation initiation factor 4A, a component of the translation initiation complex. To ascertain whether Pdcd4 suppresses tumor development in vivo, we have generated transgenic mice that overexpress Pdcd4 in the epidermis (K14-Pdcd4). K14-regulated Pdcd4 expression caused a neonatal short-hair phenotype due to early catagen entry compared with matched wild-type siblings. In response to the 7,12-dimethylbenz(a)anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA) mouse skin carcinogenesis protocol, K14-Pdcd4 mice showed significant reductions in papilloma formation, carcinoma incidence, and papilloma-to-carcinoma conversion frequency compared with wild-type mice. The translational efficiency of an mRNA engineered to form a structured 5′ untranslated region (UTR) was attenuated in primary keratinocytes when Pdcd4 was overexpressed. Pdcd4 inhibited by 46% TPA-induced activator protein-1 (AP-1)–dependent transcription, an event required for tumorigenesis. CDK4 and ornithine decarboxylase (ODC) are candidates for Pdcd4-regulated translation as their mRNAs contain 5′structured UTRs. In K14-Pdcd4 primary keratinocytes expressing activated Ha-Ras to mimic DMBA-initiated epidermis, ODC and CDK4 protein levels were decreased by 40% and 46%, respectively. Expression of a protein encoded by 5′ unstructured mRNA showed no change. These results extend to an in vivo model the observations that Pdcd4 inhibits both translation initiation and AP-1 activation while decreasing benign tumor development and malignant progression. The K14-Pdcd4 mice seem to validate translation initiation as a novel target for cancer prevention.
p210BCR-ABL inhibits SDF-1 Chemotactic Response via Alteration of CXCR4 Signaling and Down-regulation of CXCR4 Expression
Authors: Geay Jean-Francois , Buet Dorothée , Zhang Yanyan , Foudi Adlen , Jarrier Peggy , Berthebaud Magali , Turhan Ali G. , Vainchenker William , Louache Fawzia
Published: September 2005

It has been shown that p210BCR-ABL significantly impairs CXCR4 signaling. We report here that the migratory response to SDF-1 was profoundly altered in blast crisis, whereas chronic-phase CD34+ cells migrated normally to this chemokine. This migratory defect was associated with a low CXCR4 membrane expression. In vitro STI-571 treatment of CD34+ cells from patients in blast crisis markedly increased the CXCR4 transcript and CXCR4 membrane expression. Because p210BCR-ABL frequently increases with disease progression, we determined the effects of high and low p210BCR-ABL expression on CXCR4 protein in the granulocyte macrophage colony-stimulating factor–dependent human cell line MO7e. p210BCR-ABL expression distinctly alters CXCR4 protein through two different mechanisms depending on its expression level. At low expression, a signaling defect was detected with no modification of CXCR4 expression. However, higher p210BCR-ABL expression induced a marked down-regulation of CXCR4 that is related to its decreased transcription. The effect of p210BCR-ABL required its tyrosine kinase activity. Collectively, these data indicate that p210BCR-ABL could affect CXCR4 by more than one mechanism and suggest that down-regulation of CXCR4 may have important implications in chronic myelogenous leukemia pathogenesis.
Role of Checkpoint Kinase 1 in Preventing Premature Mitosis in Response to Gemcitabine
Authors: Morgan Meredith A. , Parsels Leslie A. , Parsels Joshua D. , Mesiwala Alefiyah K. , Maybaum Jonathan , Lawrence Theodore S.
Published: September 2005

The deoxycytidine analogue 2′,2′-difluoro-2′-deoxycytidine (gemcitabine) is a potent radiation sensitizer in a variety of solid tumors and tumor cell lines. Previous studies have shown that radiosensitization by gemcitabine is accompanied by simultaneous depletion of dATP pools (through ribonucleotide reductase inhibition) and accumulation in the S-phase of the cell cycle. Because of the importance of cell cycle redistribution in gemcitabine-mediated radiosensitization, we investigated the role of checkpoint kinase (Chk) 1 and Chk2 in gemcitabine-induced cell cycle arrest. We hypothesized that gemcitabine might induce Chk1 or Chk2 signal transduction pathways that mediate S-phase arrest. We found that radiosensitizing concentrations of gemcitabine induced accumulation of phosphorylated Chk1 and Chk2 and down-regulation of Cdc25A in BxPC-3 (10 nmol/L), Panc-1 (100 nmol/L), A549 (30 nmol/L), RKO (30 nmol/L), and SW620 (30 nmol/L) cells. Depletion of Chk1 from Panc-1 cells prevented the down-regulation of Cdc25A in response to gemcitabine. Furthermore, Chk1 depletion permitted Panc-1 and SW620 cells treated with gemcitabine to enter mitosis despite incomplete DNA synthesis. However, depletion of neither Chk1 nor Chk2 abrogated the inhibition of DNA synthesis in response to gemcitabine. These results provide evidence that Chk1 negatively regulates entry into mitosis in response to gemcitabine. Furthermore, these data imply that Chk1 acts to coordinate the cell cycle with DNA synthesis, thus preventing premature mitotic entry in gemcitabine-treated cells.
Inactivation of Anthracyclines by Cellular Peroxidase
Authors: Reszka Krzysztof J. , Wagner Brett A. , Teesch Lynn M. , Britigan Bradley E. , Spitz Douglas R. , Burns C. Patrick
Published: September 2005

The anticancer anthracyclines, doxorubicin and daunorubicin, are highly cytotoxic to both cancer and normal cells. In this work, we have investigated the capacity of cellular myeloperoxidase to inactivate these agents. We show that incubation of human leukemia HL-60 cells with the anthracyclines in the presence of hydrogen peroxide and nitrite causes irreversible oxidation of the drugs, suggesting an extensive modification of their chromophores. Methimazole, 4-aminobenzoic acid hydrazide, or azide inhibits the reaction, suggesting that it is mediated by the cellular myeloperoxidase, an enzyme naturally present in large amounts in HL-60 cells. In contrast to the intact drugs, the oxidatively transformed anthracyclines were substantially less cytotoxic for HL-60 (assayed by apoptosis) and PC3 prostate cancer cells and H9c2 rat cardiac myoblasts in vitro (assayed by clonogenic survival), indicating that the oxidative metabolism of these agents leads to their inactivation. Using tandem mass spectrometry, we identified two specific metabolic products of the anthracycline degradation, 3-methoxyphthalic acid and 3-methoxysalicylic acid. These two metabolic products were obtained as authentic compounds and were nontoxic to HL-60 leukemic cells and cardiac myocytes. These findings may have important implications for the cellular pharmacology of anthracyclines and for clinical oncology.
Human High Molecular Weight Melanoma-Associated Antigen Mimicry by Mouse Anti-Idiotypic Monoclonal Antibody MK2-23: Enhancement of Immunogenicity of Anti-Idiotypic Monoclonal Antibody MK2-23 by Fusion with Interleukin 2
Authors: Wang Xinhui , Ko Eric C. , Peng Liaomin , Gillies Stephen D. , Ferrone Soldano
Published: September 2005

To overcome unresponsiveness to the self-high molecular weight melanoma-associated antigen (HMW-MAA) in hosts with constitutive HMW-MAA expression, we have used as immunogen the anti-idiotypic monoclonal antibody (mAb) MK2-23, which mimics the antigenic determinant recognized by the anti-HMW-MAA mAb 763.74. In a phase I/II clinical trial, anti-idiotypic mAb MK2-23, conjugated to keyhole limpet hemocyanin (KLH) as a carrier and given with Bacillus Calmette-Guerin (BCG) as an adjuvant, elicited HMW-MAA-specific antibodies in about 60% of the immunized melanoma patients. The immune response was associated with survival prolongation. However, safety and standardization issues associated with the use of KLH and BCG in the clinical setting have prompted us to develop alternative immunization strategies. Conjugation of human interleukin 2 (IL-2) to mAb MK2-23 variable regions covalently linked to human immunoglobulin constant regions enhanced mAb MK2-23 immunogenicity in BALB/c mice to an extent similar to that induced by mAb MK2-23 conjugated to KLH and given with Freund's adjuvant. As determined by the level of serum antibodies and delayed-type hypersensitivity responses to HMW-MAA-bearing melanoma cells, immunization of mice with the MK2-23-IL-2 fusion protein elicited more robust humoral and cellular responses, respectively, than immunization with KLH-conjugated mAb MK2-23 and separate administration of IL-2. The immunogenicity of the fusion protein is dependent on IL-2 conjugation, because immunization of mice with either mAb MK2-23 or chimeric mAb MK2-23, in combination with IL-2, was not as effective in eliciting HMW-MAA-specific immune responses. These results suggest that the MK2-23-IL-2 fusion protein represents a useful immunogen to implement active specific immunotherapy in patients with melanoma, because it bypasses the requirement for KLH conjugation and adjuvant administration.