7 research outputs found
Design and Synthesis of Pironetin Analogue/Colchicine Hybrids and Study of Their Cytotoxic Activity and Mechanisms of Interaction with Tubulin
We here report the synthesis of a
series of 12 hybrid molecules
composed of a colchicine moiety and a pironetin analogue fragment.
The two fragments are connected through an esterāamide spacer
of variable length. The cytotoxic activities of these compounds and
their interactions with tubulin have been investigated. Relations
between the structure and activity are discussed. Since the spacer
is not long enough to permit a simultaneous binding of the hybrid
molecules to the colchicine and pironetin sites on tubulin, a further
feature investigated was whether these molecules would interact with
the latter through the pironetin end (irreversible covalent binding)
or through the colchicine end (reversible noncovalent binding). It
has been found that binding to tubulin may take place preferentially
at either of these ends depending on the length of the connecting
spacer
Synthesis, Characterization, and Application in HeLa Cells of an NIR Light Responsive Doxorubicin Delivery System Based on NaYF<sub>4</sub>:Yb,Tm@SiO<sub>2</sub>āPEG Nanoparticles
Herein, we present a phototriggered
drug delivery system based on light responsive nanoparticles, which
is able to release doxorubicin upon NIR light illumination. The proposed
system is based on upconversion fluorescence nanoparticles of Ī²-NaYF<sub>4</sub>:Yb,Tm@SiO<sub>2</sub>-PEG with a mean diameter of 52 Ā±
2.5 nm that absorb the NIR light and emit UV light. The UV radiation
causes the degradation of photodegradable <i>ortho</i>-nitrobenzyl
alcohol derivates, which are attached on one side to the surface of
the nanoparticles and on the other to doxorubicin. This degradation
triggers the doxorubicin release. This drug delivery system has been
tested ā<i>in vitro</i>ā with HeLa cells.
The results of this study demonstrated that this system caused negligible
cytotoxicity when they were not illuminated with NIR light. In contrast,
under NIR light illumination, the HeLa cell viability was conspicuously
reduced. These results demonstrated the suitability of the proposed
system to control the release of doxorubicin via an external NIR light
stimulus
Novel Colchicine-Site Binders with a Cyclohexanedione Scaffold Identified through a Ligand-Based Virtual Screening Approach
Vascular
disrupting agents (VDAs) constitute an innovative anticancer
therapy that targets the tumor endothelium, leading to tumor necrosis.
Our approach for the identification of new VDAs has relied on a ligand
3-D shape similarity virtual screening (VS) approach using the ROCS
program as the VS tool and as query colchicine and TN-16, which both
bind the Ī±,Ī²-tubulin dimer. One of the hits identified,
using TN-16 as query, has been explored by the synthesis of its structural
analogues, leading to 2-(1-((2-methoxyphenyl)Āamino)Āethylidene)-5-phenylcyclohexane-1,3-dione
(compound <b>16c</b>) with an IC<sub>50</sub> = 0.09 Ā±
0.01 Ī¼M in HMEC-1 and BAEC, being 100-fold more potent than
the initial hit. Compound <b>16c</b> caused cell cycle arrest
in the G2/M phase and interacted with the colchicine-binding site
in tubulin, as confirmed by a competition assay with <i><i>N,N</i></i>ā²<b>-</b>ethylenebisĀ(iodoacetamide)
and by fluorescence spectroscopy. Moreover, <b>16c</b> destroyed
an established endothelial tubular network at 1 Ī¼M and inhibited
the migration and invasion of human breast carcinoma cells at 0.4
Ī¼M. In conclusion, our approach has led to a new chemotype of
promising antiproliferative compounds with antimitotic and potential
VDA properties
Total Synthesis of Amphidinolide K, a Macrolide That Stabilizes FāActin
The total synthesis of (ā)-amphidinolide
K (<b>1</b>) based on asymmetric addition of allylsilane <b>C1</b>ā<b>C8</b> to enal <b>C9</b>ā<b>C22</b> is reported.
The 1,9,18-tris-<i>O</i>-TBDPS ether was converted into
the desired 9,18-dihydroxy acid. Its macrolactonization was accomplished
by the Shiina method. Compound <b>1</b> together with some of
its stereoisomers and analogues were subjected to evaluation of the
possible disruption of the Ī±,Ī²-tubulināmicrotubule
and/or G-actināF-actin equilibria. Compound <b>1</b> behaves
as a stabilizer of actin filaments (F-actin) in vitro
Structural and Biochemical Characterization of the Interaction of Tubulin with Potent Natural Analogues of Podophyllotoxin
Four natural analogues of podophyllotoxin
obtained from the Mexican
medicinal plant <i>Bursera fagaroides</i>, namely, acetyl
podophyllotoxin (<b>2</b>), 5ā²-desmethoxy-Ī²-peltatin
A methyl ether (<b>3</b>), 7ā²,8ā²-dehydro acetyl
podophyllotoxin (<b>4</b>), and burseranin (<b>5</b>),
have been characterized, and their interactions with tubulin have
been investigated. Cytotoxic activity measurements, followed by immunofluorescence
microscopy and flow cytometry studies, demonstrated that these compounds
disrupt microtubule networks in cells and cause cell cycle arrest
in the G2/M phase in the A549 cell line. A tubulin binding assay showed
that compounds <b>1</b>ā<b>4</b> were potent assembly
inhibitors, displaying binding to the colchicine site with <i>K</i><sub>b</sub> values ranging from 11.75 to 185.0 Ć
10<sup>5</sup> M<sup>ā1</sup>. In contrast, burseranin (<b>5</b>) was not able to inhibit tubulin assembly. From the structural
perspective, the ligand-binding epitopes of compounds <b>1</b>ā<b>3</b> have been mapped using STD-NMR, showing that
B and E rings are the major points for interaction with the protein.
The obtained results indicate that the inhibition of tubulin assembly
of this family of compounds is more effective when there are at least
two methoxyl groups at the E ring, along with a <i>trans</i> configuration of the lactone ring in the aryltetralin lignan core
Endowing Indole-Based Tubulin Inhibitors with an Anchor for Derivatization: Highly Potent 3āSubstituted Indolephenstatins and Indoleisocombretastatins
Colchicine site ligands with indole
B rings are potent tubulin
polymerization inhibitors. Structural modifications at the indole
3-position of 1-methyl-5-indolyl-based isocombretastatins (1,1-diarylethenes)
and phenstatins endowed them with anchors for further derivatization
and resulted in highly potent compounds. The substituted derivatives
displayed potent cytotoxicity against several human cancer cell lines
due to tubulin inhibition, as shown by cell cycle analysis, confocal
microscopy, and tubulin polymerization inhibitory activity studies
and promoted cell killing mediated by caspase-3 activation. Binding
at the colchicine site was confirmed by means of fluorescence measurements
of MTC displacement. Molecular modeling suggests that the tropolone-binding
region of the colchicine site of tubulin can adapt to hosting small
polar substituents. Isocombretastatins accepted substitutions better
than phenstatins, and the highest potencies were achieved for the
cyano and hydroxyiminomethyl substituents, with TPI values in the
submicromolar range and cytotoxicities in the subnanomolar range.
A 3,4,5-trimethoxyphenyl ring usually afforded more potent derivatives
than a 2,3,4-trimethoxyphenyl ring
Synthesis and Antimitotic and Tubulin Interaction Profiles of Novel Pinacol Derivatives of Podophyllotoxins
Several pinacol derivatives of podophyllotoxins bearing
different side chains and functions at C-7 were synthesized through
reductive cross-coupling of podophyllotoxone and several aldehydes
and ketones. While possessing a hydroxylated chain at C-7, the compounds
retained their respective hydroxyl group with either the 7Ī±
(podo) or 7Ī² (epipodo) configuration. Along with pinacols, some
C-7 alkylidene and C-7 alkyl derivatives were also prepared. Cytotoxicities
against neoplastic cells followed by cell cycle arrest and cellular
microtubule disruption were evaluated and mechanistically characterized
through tubulin polymerization inhibition and assays of binding to
the colchicine site. Compounds of the epipodopinacol (7Ī²-OH)
series behaved similarly to podophyllotoxin in all the assays and
proved to be the most potent inhibitors. Significantly, 7Ī±-isopropyl-7-deoxypodophyllotoxin
(<b>20</b>), without any hydroxyl function, appeared as a promising
lead compound for a novel type of tubulin polymerization inhibitors.
Experimental results were in overall agreement with modeling and docking
studies performed on representative compounds of each series