A Novel Approach to Targeted Oncologic Therapy - Co-culture Viability of Polymer Prodrug Conjugation to Mesenchymal Stem Cells

Background/Purpose: Conjugation of polymer prodrugs to tumor homing cells, such as Mesenchymal Stem Cells (MSCs), could provide a vehicle for actively targeted delivery of polymer prodrugs. Methods: Human Bone Marrow MSCs were conjugated to either a doxorubicin polymer prodrug or free doxorubicin and were co-cultured with T-cells. Viability was assessed through the use of a Vi-cell counter. In Vivo Migration Analysis was performed NOD SCID mice implanted with subcutaneous MDA MB-231 breast cancer xenografts. Following tumor establishment, mice were injected via lateral tail vein injection with either saline or polymer loaded MSCs. Five days following stem cell injection, mice were euthanized, tumors were harvested and sections were analyzed using fluorescent microscopy and immuno-histochemical staining for cd105. Results: T-cell viability was reduced when co-cultured with MSCs conjugated to free doxorubicin although cells co-cultured with MSCs conjugated to doxorubicin polymer did not exhibit reduced viability. Polymer loaded MSCs displayed intact tumor homing migratory ability in vivo (Figure 1). Conclusion: MSCs conjugated to doxorubicin released the drug, resulting in reduced neighboring T-cells viability. MSCs loaded with polymer maintained their migratory capacity were able to migrate to tumors in vivo. MSCs therefore represent a potential vehicle for targeted drug delivery. Future work will focus on developing methods for releasing the drug upon successful delivery to the target in vivo

In Vivo Evaluation of a Biomimetic Polymer-Doxorubicin Conjugate for Cancer Therapy

This poster will describe a novel polymer pro-drug platform designed for conjugation and delivery of chemotherapeutics. Specifically, polymer pro-drugs were prepared from functional polymer zwitterions and doxorubicin (DOX), and evaluated in vivo to assess toxicological, pharmacokinetic and therapeutic properties. The biocompatible polymer scaffold (PolyMPC) consists of zwitterionic phosphorylcholine pendent groups, which mimic the natural hydrophilic moieties of phospholipids in cell membranes, and hydrazone linkages that allow for pH-triggered release of DOX. PolyMPC-DOX pro-drugs were isolated as dry solids using a facile strategy that allows for precise control of molecular weight and DOX incorporation. In vivo toxicity of PolyMPC and PolyMPC-DOX was assessed in a murine model. The maximum tolerated dose of the pro-drug was five times greater than that of free DOX, while PolyMPC alone exhibited no toxicity even at a dose of 800 mg/kg. A pharmacokinetic study in tumor-bearing mice demonstrated a significant increase in circulation half-life of conjugated DOX (t1/2=2 hours) compared to free DOX (t1/2=15 minutes), with conjugated DOX detectable in blood serum for longer than 24 hours. This pronounced enhancement in circulation time was attributed to the macromolecular scaffold, which precludes rapid renal clearance compared to native DOX. Examination of mice given PolyMPC-DOX five days after injection in the PK study showed a three-fold increase of drug accumulated in tumor tissue compared to that of mice treated with free DOX and drug accumulation in off-target organs was reduced for mice given DOX conjugate. The therapeutic efficacy of the PolyMPC-DOX conjugates was then assessed in an orthotopic murine breast cancer model. The treatment group given PolyMPC-DOX exhibited a two-fold increase in overall survival and a significant reduction in average tumor volume compared to the free DOX and saline control groups. A study evaluating the therapeutic efficacy of PolyMPC-DOX in a human ovarian xenograft tumor model is ongoing

Efficacy of PolyMPC–DOX Prodrugs in 4T1 Tumor-Bearing Mice

We report the <i>in vivo</i> efficacy, in tumor-bearing mice, of cancer prodrugs consisting of poly­(methacryloyloxyethyl phosphorylcholine) (polyMPC) conjugated to doxorubicin (DOX). Our synthesis of polyMPC–DOX conjugates established prodrugs with tunable drug loading, pH sensitive release kinetics, and a maximum tolerated dose in the range of 30–50 mg/kg (DOX equivalent) in healthy mice. Here we show prolonged circulation of polyMPC–DOX, with a measured <i>in vivo</i> half-life (<i>t</i>_1/2) 8 times greater than that of the free drug. We observed reduced drug uptake in healthy tissue, and 2–3 times enhanced drug accumulation in tumors for polyMPC–DOX prodrugs compared to free DOX, using BALB/c mice bearing 4T1 tumors. Prolonged survival and reduced tumor growth were observed in mice receiving the polyMPC–DOX prodrug treatment. Moreover, we evaluated immunogenicity of polyMPC–DOX prodrugs by examining complete blood count (CBC) and characteristic cytokine responses, demonstrating no apparent innate or adaptive immune system response

Disulfide Cross-Linked Phosphorylcholine Micelles for Triggered Release of Camptothecin

A series of block copolymers based on 2-methacryloyloxyethyl phosphorylcholine (MPC) were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. Incorporation of dihydrolipoic acid (DHLA) into the hydrophobic block led to formation of block copolymer micelles in water. The micelles were between 15 and 30 nm in diameter, as characterized by dynamic light scattering (DLS), with some size control achieved by adjusting the hydrophobic/hydrophilic balance. Cross-linked micelles were prepared by disulfide formation, and observed to be stable in solution for weeks. The micelles proved amenable to disassembly when treated with a reducing agent, such as dithiothreitol (DTT), and represent a potential delivery platform for chemotherapeutic agents. As a proof-of-concept, camptothecin (CPT) was conjugated to the polymer scaffold through a disulfide linkage, and release of the drug from the micelle was monitored by fluorescence spectroscopy. These CPT-loaded prodrug micelles showed a reduction in release rate compared to physically encapsulated CPT. The use of disulfide conjugation facilitated drug release under reducing conditions, with a half-life (<i>t</i>_1/2) of 5.5 h in the presence of 3 mM DTT, compared to 28 h in PBS. The toxicity of the micellar prodrugs was evaluated in cell culture against human breast (MCF7) and colorectal (COLO205) cancer cell lines

Evaluation of PolyMPC–Dox Prodrugs in a Human Ovarian Tumor Model

A polymer prodrug, composed of doxorubicin (Dox) conjugated covalently to poly­(methacryloyloxyethyl phosphorylcholine) (polyMPC), was evaluated for the treatment of human ovarian tumors in animals. PolyMPC–Dox prodrugs were prepared using facile conjugation chemistry to yield conjugates soluble in water and injectable saline, with a Dox loading of ∼19 weight percent. Toxicity evaluation showed that polyMPC was well-tolerated in mice at doses up to 800 mg/kg, confirming the biocompatibility of the polymer carrier at a high concentration. Additionally, the polyMPC–Dox prodrug was well-tolerated in animals at a Dox equivalent dose of 10 mg/kg, greater than twice the maximum tolerated dose of free Dox (∼4 mg/kg) in the same mouse strain. In a human ovarian tumor model (SKOV-3), polyMPC–Dox accumulated in tumors at twice the level of free Dox, with no additional off-target organ uptake, a result of improved pharmacokinetics afforded by the prodrug and passive targeting attributed to an enhanced permeability and retention effect. When administered to human ovarian tumor-bearing mice using a recurring dosing regimen comparable to that used clinically, polyMPC–Dox significantly retarded tumor growth relative to treatment with free Dox. Moreover, animals treated with multiple doses of polyMPC–Dox (eight total doses) exhibited enhanced survival, with a notably reduced incidence of toxicity or adverse events relative to mice treated with free Dox. These in vivo results demonstrate advantages of treating human ovarian tumors with polyMPC–Dox, including reduced systemic toxicity, improved drug accumulation in tumors, and enhanced therapeutic efficacy

Search for intermediate mass black hole binaries in the first observing run of Advanced LIGO

International audienceDuring their first observational run, the two Advanced LIGO detectors attained an unprecedented sensitivity, resulting in the first direct detections of gravitational-wave signals produced by stellar-mass binary black hole systems. This paper reports on an all-sky search for gravitational waves (GWs) from merging intermediate mass black hole binaries (IMBHBs). The combined results from two independent search techniques were used in this study: the first employs a matched-filter algorithm that uses a bank of filters covering the GW signal parameter space, while the second is a generic search for GW transients (bursts). No GWs from IMBHBs were detected; therefore, we constrain the rate of several classes of IMBHB mergers. The most stringent limit is obtained for black holes of individual mass 100  M⊙, with spins aligned with the binary orbital angular momentum. For such systems, the merger rate is constrained to be less than 0.93  Gpc−3 yr−1 in comoving units at the 90% confidence level, an improvement of nearly 2 orders of magnitude over previous upper limits

First low-frequency Einstein@Home all-sky search for continuous gravitational waves in Advanced LIGO data

International audienceWe report results of a deep all-sky search for periodic gravitational waves from isolated neutron stars in data from the first Advanced LIGO observing run. This search investigates the low frequency range of Advanced LIGO data, between 20 and 100 Hz, much of which was not explored in initial LIGO. The search was made possible by the computing power provided by the volunteers of the Einstein@Home project. We find no significant signal candidate and set the most stringent upper limits to date on the amplitude of gravitational wave signals from the target population, corresponding to a sensitivity depth of 48.7  [1/Hz]. At the frequency of best strain sensitivity, near 100 Hz, we set 90% confidence upper limits of 1.8×10-25. At the low end of our frequency range, 20 Hz, we achieve upper limits of 3.9×10-24. At 55 Hz we can exclude sources with ellipticities greater than 10-5 within 100 pc of Earth with fiducial value of the principal moment of inertia of 1038  kg m2

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

International audienceSpinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signal-to-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far

Open data from the first and second observing runs of Advanced LIGO and Advanced Virgo

Advanced LIGO and Advanced Virgo are monitoring the sky and collecting gravitational-wave strain data with sufficient sensitivity to detect signals routinely. In this paper we describe the data recorded by these instruments during their first and second observing runs. The main data products are gravitational-wave strain time series sampled at 16384 Hz. The datasets that include this strain measurement can be freely accessed through the Gravitational Wave Open Science Center at http://gw-openscience.org, together with data-quality information essential for the analysis of LIGO and Virgo data, documentation, tutorials, and supporting software