Microbe-Specific C3b Deposition in the Horseshoe Crab Complement System in a C2/Factor B-Dependent or -Independent Manner

Complement C3 plays an essential role in the opsonization of pathogens in the mammalian complement system, whereas the molecular mechanism underlying C3 activation in invertebrates remains unknown. To understand the molecular mechanism of C3b deposition on microbes, we characterized two types of C2/factor B homologs (designated TtC2/Bf-1 and TtC2/Bf-2) identified from the horseshoe crab Tachypleus tridentatus. Although the domain architectures of TtC2/Bf-1 and TtC2/Bf-2 were identical to those of mammalian homologs, they contained five-repeated and seven-repeated complement control protein domains at their N-terminal regions, respectively. TtC2/Bf-1 and TtC2/Bf-2 were synthesized and glycosylated in hemocytes and secreted to hemolymph plasma, which existed in a complex with C3 (TtC3), and their activation by microbes was absolutely Mg2+-dependent. Flow cytometric analysis revealed that TtC3b deposition was Mg2+-dependent on Gram-positive bacteria or fungi, but not on Gram-negative bacteria. Moreover, this analysis demonstrated that Ca2+-dependent lectins (C-reactive protein-1 and tachylectin-5A) were required for TtC3b deposition on Gram-positive bacteria, and that a Ca2+-independent lectin (Tachypleus plasma lectin-1) was definitely indispensable for TtC3b deposition on fungi. In contrast, a horseshoe crab lipopolysaccharide-sensitive protease factor C was necessary and sufficient to deposit TtC3b on Gram-negative bacteria. We conclude that plasma lectins and factor C play key roles in microbe-specific TtC3b deposition in a C2/factor B-dependent or -independent manner

ZD6474 reverses multidrug resistance by directly inhibiting the function of P-glycoprotein

P-glycoprotein (P-gp) pumps multiple types of drugs out of the cell, using energy generated from ATP, and confers multidrug resistance (MDR) on cancer cells. ZD6474 is an orally active, selective inhibitor of the vascular endothelial growth factor receptor, epidermal growth factor receptor, and rearranged during transfection tyrosine kinases. This study was designed to examine whether ZD6474 reverses P-gp-mediated MDR in cancer cells. Here, we show that clinically achievable levels of ZD6474 reverse P-gp-mediated MDR of the P-gp-overexpressing cell lines derived from breast cancer, MCF-7/adriamycin (ADR), and human oral epidermoid carcinoma, KBV200 to ADR, docetaxel, and vinorelbine. This ability to reverse the P-gp-mediated resistance is comparable to that of another frequently used reversal agent known as verapamil. ZD6474 itself moderately inhibits the proliferation of both MCF-7 and MCF-7/ADR cells with almost equal activity, but its inhibitory effect is not altered by co-incubation with verapamil, suggesting that ZD6474 may not be a substrate of P-gp. In addition, ZD6474 increases the intracellular accumulation of the P-gp substrate, rhodamine-123, and ADR, by enhancing the uptake and/or decreasing the efflux of these compounds in resistant cells. Further studies show that ZD6474 stimulates ATPase activity in a dose-dependent manner, which is required for the proper function of P-gp. In contrast, ZD6474 does not inhibit the expression level of P-gp. Our results suggest that ZD6474 is capable of reversing MDR in cancer cells by directly inhibiting the function of P-gp, a finding that may have clinical implications for ZD6474

Physical properties of Centaur (60558) 174P/Echeclus from stellar occultations

The Centaur (60558) Echeclus was discovered on March 03, 2000, orbiting between the orbits of Jupiter and Uranus. After exhibiting frequent outbursts, it also received a comet designation, 174P. If the ejected material can be a source of debris to form additional structures, studying the surroundings of an active body like Echeclus can provide clues about the formation scenarios of rings, jets, or dusty shells around small bodies. Stellar occultation is a handy technique for this kind of investigation, as it can, from Earth-based observations, detect small structures with low opacity around these objects. Stellar occultation by Echeclus was predicted and observed in 2019, 2020, and 2021. We obtain upper detection limits of rings with widths larger than 0.5 km and optical depth of $\tau$ = 0.02. These values are smaller than those of Chariklo's main ring; in other words, a Chariklo-like ring would have been detected. The occultation observed in 2020 provided two positive chords used to derive the triaxial dimensions of Echeclus based on a 3D model and pole orientation available in the literature. We obtained $a = 37.0\pm0.6$ km, $b = 28.4 \pm 0.5$ km, and $c= 24.9 \pm 0.4$ km, resulting in an area-equivalent radius of $30.0 \pm 0.5$ km. Using the projected limb at the occultation epoch and the available absolute magnitude ($\rm{H}_{\rm{v}} = 9.971 \pm 0.031$), we calculate an albedo of $p_{\rm{v}} = 0.050 \pm 0.003$. Constraints on the object's density and internal friction are also proposed.Comment: Corrected and typeset versio

Stellar occultations enable milliarcsecond astrometry for Trans-Neptunian objects and Centaurs

Trans-Neptunian objects (TNOs) and Centaurs are remnants of our planetary system formation, and their physical properties have invaluable information for evolutionary theories. Stellar occultation is a ground-based method for studying these small bodies and has presented exciting results. These observations can provide precise profiles of the involved body, allowing an accurate determination of its size and shape. The goal is to show that even single-chord detections of TNOs allow us to measure their milliarcsecond astrometric positions in the reference frame of the Gaia second data release (DR2). Accurated ephemerides can then be generated, allowing predictions of stellar occultations with much higher reliability. We analyzed data from stellar occultations to obtain astrometric positions of the involved bodies. The events published before the Gaia era were updated so that the Gaia DR2 catalog is the reference. Previously determined sizes were used to calculate the position of the object center and its corresponding error with respect to the detected chord and the International Celestial Reference System (ICRS) propagated Gaia DR2 star position. We derive 37 precise astrometric positions for 19 TNOs and 4 Centaurs. Twenty-one of these events are presented here for the first time. Although about 68\% of our results are based on single-chord detection, most have intrinsic precision at the submilliarcsecond level. Lower limits on the diameter and shape constraints for a few bodies are also presented as valuable byproducts. Using the Gaia DR2 catalog, we show that even a single detection of a stellar occultation allows improving the object ephemeris significantly, which in turn enables predicting a future stellar occultation with high accuracy. Observational campaigns can be efficiently organized with this help, and may provide a full physical characterization of the involved object.Comment: 16 pages, 28 figures. The manuscript was accepted and is to be publishe

Vandetanib (Zactima, ZD6474) Antagonizes ABCC1- and ABCG2-Mediated Multidrug Resistance by Inhibition of Their Transport Function

ABCC1 and ABCG2 are ubiquitous ATP-binding cassette transmembrane proteins that play an important role in multidrug resistance (MDR). In this study, we evaluated the possible interaction of vandetanib, an orally administered drug inhibiting multiple receptor tyrosine kinases, with ABCC1 and ABCG2 in vitro.MDR cancer cells overexpressing ABCC1 or ABCG2 and their sensitive parental cell lines were used. MTT assay showed that vandetanib had moderate and almost equal-potent anti-proliferative activity in both sensitive parental and MDR cancer cells. Concomitant treatment of MDR cells with vandetanib and specific inhibitors of ABCC1 or ABCG2 did not alter their sensitivity to the former drug. On the other hand, clinically attainable but non-toxic doses of vandetanib were found to significantly enhance the sensitivity of MDR cancer cells to ABCC1 or ABCG2 substrate antitumor drugs. Flow cytometric analysis showed that vandetanib treatment significantly increase the intracellular accumulation of doxorubicin and rhodamine 123, substrates of ABCC1 and ABCG2 respectively, in a dose-dependent manner (P<0.05). However, no significant effect was shown in sensitive parental cell lines. Reverse transcription-PCR and Western blot analysis showed that vandetanib did not change the expression of ABCC1 and ABCG2 at both mRNA and protein levels. Furthermore, total and phosphorylated forms of AKT and ERK1/2 remained unchanged after vandetanib treatment in both sensitive and MDR cancer cells.Vandetanib is unlikely to be a substrate of ABCC1 or ABCG2. It overcomes ABCC1- and ABCG2-mediated drug resistance by inhibiting the transporter activity, independent of the blockade of AKT and ERK1/2 signal transduction pathways

A phase II study of amrubicin and carboplatin for previously untreated patients with extensive-disease small cell lung cancer

Background: Amrubicin is active in the treatment of extensive-disease small cell lung cancer (ED-SCLC), and carboplatin is an analogue of cisplatin with less non-hematological toxicity. Purpose: The purpose of this study was to determine the efficacy and toxicity of amrubicin and carboplatin combination chemotherapy for previously untreated patients with ED-SCLC. Patients and methods: Eligibility criteria were chemotherapy-naive ED-SCLC patients, performance status 0-1, age ?75, and adequate hematological, hepatic and renal function. Based on the phase I study, the patients received amrubicin 35 mg/m2 i.v. infusion on days 1, 2, and 3, and carboplatin AUC 5 i.v. infusion on day 1. Four cycles of chemotherapy were repeated every 3 weeks. Results: Thirty-five patients were enrolled, and 34 patients were eligible and assessable for response, toxicity, and survival. Patients\u27 characteristics were as follows: male/female = 26/8; performance status 0/1 = 4/30; median age (range) = 64 (41-75); stage IV = 34. Evaluation of responses was 6 complete response, 21 partial response, and 7 stable disease (response rate 79.4 %, 95 % CI 63.6-88.5 %). Grade 3 and 4 leukopenia, neutropenia, and thrombocytopenia occurred in 59, 82, and 26 %, respectively. There were no treatment-related deaths or pneumonitis. Three patients experienced hypotension as an amrubicin infusion reaction. The median progression-free survival time was 6.5 months. The median overall survival time and 1-, 2-, and 3-year survival rates were 15.6 months, and 63, 28, and 7 %, respectively. Conclusions: Amrubicin and carboplatin were effective and tolerable as chemotherapy for previously untreated patients with ED-SCLC. Further investigation of amrubicin and carboplatin is warranted