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A cell-based fascin bioassay identifies compounds with potential anti-metastasis or cognition-enhancing functions

01 Jan 2013-Journal of Cell Science (The Company of Biologists Ltd)-Vol. 126, Iss: 1

AbstractSUMMARY The actin-bundling protein fascin is a key mediator of tumor invasion and metastasis and its activity drives filopodia formation, cell-shape changes and cell migration. Small-molecule inhibitors of fascin block tumor metastasis in animal models. Conversely, fascin deficiency might underlie the pathogenesis of some developmental brain disorders. To identify fascin-pathway modulators we devised a cell-based assay for fascin function and used it in a bidirectional drug screen. The screen utilized cultured fascin-deficient mutant Drosophila neurons, whose neurite arbors manifest the 'filagree' phenotype. Taking a repurposing approach, we screened a library of 1040 known compounds, many of them FDA-approved drugs, for filagree modifiers. Based on scaffold distribution, molecular-fingerprint similarities, and chemical-space distribution, this library has high structural diversity, supporting its utility as a screening tool. We identified 34 fascin-pathway blockers (with potential anti-metastasis activity) and 48 fascin- pathway enhancers (with potential cognitive-enhancer activity). The structural diversity of the active compounds suggests multiple molecular targets. Comparisons of active and inactive compounds provided preliminary structure-activity relationship information. The screen also revealed diverse neurotoxic effects of other drugs, notably the 'beads-on-a-string' defect, which is induced solely by statins. Statin-induced neurotoxicity is enhanced by fascin deficiency. In summary, we provide evidence that primary neuron culture using a genetic model organism can be valuable for early-stage drug discovery and developmental neurotoxicity testing. Furthermore, we propose that, given an appropriate assay for target-pathway function, bidirectional screening for brain-development disorders and invasive cancers represents an efficient, multipurpose strategy for drug discovery.

Topics: Fascin (63%), Genetic model (53%), Drug discovery (50%)

Summary (2 min read)

Jump to: [SUMMARY][RESULTS][DISCUSSION] and [METHODS]

SUMMARY

  • The actin-bundling protein fascin is a key mediator of tumor invasion and metastasis and its activity drives filopodia formation, cell-shape changes and cell migration.
  • The screen utilized cultured fascin-deficient mutant Drosophila neurons, whose neurite arbors manifest the ‘filagree’ phenotype.
  • The screen also revealed diverse neurotoxic effects of other drugs, notably the ‘beads-on-a-string’ defect, which is induced solely by statins.
  • The causal role of fascin in tumor phenotypes is supported by laboratory studies in which blocking of fascin expression reduced the invasive and/or metastatic properties of colon carcinoma (Hashimoto et al., 2007), glioblastoma multiforme (Hwang et al., 2008), gastric carcinoma (Fu et al., 2009; Kim et al., 2010) and breast carcinoma (Chen et al., 2010; Al-Alwan et al., 2011).
  • These reports point to a role for fascin in regulating neuronal differentiation and synaptic plasticity, which are disrupted in brain-development disorders (Johnston, 2004) and vulnerable during aging (Burke and Barnes, 2006).

RESULTS

  • Drug screen design using the fascin bioassay Filagree is a highly penetrant, quantifiable, pan-neuronal phenotype of fascin-deficient singed-mutant neurons cultured from the developing CNS of Drosophila mature larvae or young pupae (Fig. 1A-C) (Kraft et al., 2006).
  • Note the exaggerated neurite curvature and frequent expansions of neurite width.
  • The 48 fascin-pathway enhancers were split equally between low- and high-potency compounds; the 34 fascin-pathway blockers included 22 low- and 12 high-potency compounds (Fig. 3A).
  • Each set of active compounds is quite diverse, as indicated by its distribution throughout the chemical space of the collection without obvious localization to any particular neighborhood.
  • Consistent with this level of structural diversity, the active compounds represent diverse chemical classes and wide-ranging pharmacological mechanisms of action (supplementary material Tables S2, S3).

DISCUSSION

  • The fascin pathway as a drug-discovery target Motivated by the importance of fascin function in tumor invasion, as well as in brain development and plasticity, the authors designed and conducted a screen for pharmacological modifiers of the fascin pathway.
  • This cell-based assay, with its easily observable morphological read-out, allowed us to cast a wide net, targeting the pathway without trying to predict a priori which molecule (fascin or one of its regulators or mediators) would be the best drug target for modulating fascin function.
  • Because the dissociated neuron cultures are low density by design, with limited cell-cell contact, the effects on neurite trajectory of neuroactive compounds like acetylcholine, adiphenine, baclofen and spiperone cannot be mediated through classical neurotransmission at functional synapses.
  • There is some urgency to address statin-induced cognitive side effects.
  • Thus, two seemingly unconnected medical conditions are linked by genes with dual roles in brain development and tumor biology.

METHODS

  • Fly stocks were maintained at room temperature on corn mealyeast-agar medium obtained from the University of Arizona fly food facility.
  • Molecular fingerprints of each compound were used to measure all pair-wise similarities (Willett et al., 1998; Maggiora and Shanmugasundaram, 2011).
  • While the cells were allowed to settle and adhere for 2 hours at 25°C, eight compounds were each diluted in culture medium as needed for testing at final concentrations of 10 and 50 M (final volume 1 ml).
  • In addition to scoring the filagree phenotype, other effects on neuronal morphology were noted, again only when a significant majority of neurons in the culture displayed a consistent feature.
  • In cases where the scores in the second test were not consistent with the original experiment, the compounds were repeated a third time and the majority score from the three experiments was taken as the definitive outcome.

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A cell-based fascin bioassay identifies compounds with
potential anti-metastasis or cognition-enhancing functions.
Item Type Article
Authors Kraft, Robert; Kahn, Allon; Medina-Franco, José L.; Orlowski,
Mikayla L.; Baynes, Cayla; López-Vallejo, Fabian; Barnard, Kobus;
Maggiora, Gerald M.; Restifo, Linda L.
Citation Kraft et al. (2013). A cell-based fascin bioassay identifies
compounds with potential anti-metastasis or cognition-enhancing
functions. Dis Model Mech 6(1):217-35
DOI 10.1242/dmm.008243
Publisher The Company of Biologists
Journal Disease Models & Mechanisms
Rights © 2012 The Author(s). Published by The Company of Biologists
Ltd. This is an Open Access article distributed under the terms of
the Creative Commons Attribution Non-Commercial Share Alike
License (http://creativecommons.org/licenses/by-nc-sa/3.0).
Download date 09/08/2022 22:41:51
Item License https://creativecommons.org/licenses/by-nc-sa/3.0/
Link to Item http://hdl.handle.net/10150/605272

INTRODUCTION
A highly conserved actin-bundling protein, fascin has diverse roles
in the developmental and physiological regulation of cellular
morphology and function (Kureishy et al., 2002; Jayo and Parsons,
2010; Sedeh et al., 2010; Hashimoto et al., 2011). It is also implicated
in human disease pathogenesis, under both loss-of-function and
gain-of-function conditions, which motivated us to develop a
fascin bioassay for drug discovery. Note that fascin is unrelated to
either the fasciclins or neurofascin, which are members of the
immunoglobulin cell-adhesion molecule superfamily. Fascin drives
the formation of cell-membrane protrusions, including lamellipodia
(Yamashiro et al., 1998), microspikes (Svitkina et al., 2003), filopodia
(Vignjevic et al., 2006) and invadopodia (Li et al., 2010a), in part
because F-actin bundles increase mechanical stiffness (Tseng et al.,
2005; Vignjevic et al., 2006). In addition, fascin-mediated actin
bundling and crosslinking, which are regulated by phosphorylation
(Ono et al., 1997; Aratyn et al., 2007) and the extracellular matrix
(ECM), enhance cell migration (Ono et al., 1997; Yamashiro et al.,
1998; Anilkumar et al., 2003; Jawhari et al., 2003) and ECM
degradation (Li et al., 2010a).
Mammals have three fascin-coding genes, of which Fascin-2 and
Fascin-3 are expressed in narrow domains (Tubb et al., 2000; Tubb
et al., 2002; Shin et al., 2010), whereas Fascin-1 is broadly and
dynamically expressed. Fascin-1 is abundant early in development,
especially in the central nervous system (CNS) and migrating cells,
and is then downregulated as cells mature (De Arcangelis et al.,
2004; Zhang et al., 2008; Zanet et al., 2009; Tang et al., 2010). In
this paper, ‘fascin’ refers to the product of the Fascin-1 genes
(FSCN1 in humans, MIM#602689; Fscn1 in mouse; and singed in
Drosophila, FBgn0003447).
Fascin has a pivotal role in tumor invasion and metastasis
(Machesky and Li, 2010), leading to the proposal that fascin-
blocking drugs might prevent the spread of malignant cancers
(Yoder et al., 2005; Hashimoto et al., 2011). Because most cancer-
related deaths are due to metastases, there is an urgent need for
development of anti-metastasis agents (Sporn, 1996; Sleeman and
Steeg, 2010). For carcinomas from numerous organs, high fascin
Disease Models & Mechanisms
217
Disease Models & Mechanisms 6, 217-235 (2013) doi:10.1242/dmm.008243
1
Department of Neuroscience, University of Arizona, Tucson, AZ 85721, USA
2
Torrey Pines Institute for Molecular Studies, Port St Lucie, FL 34987, USA
3
School of Information: Science, Technology and Arts and Department of
Computer Science, University of Arizona, Tucson, AZ 85721, USA
4
BIO5 Interdisciplinary Research Institute, University of Arizona, Tucson, AZ 85721,
USA
5
Translational Genomics Research Institute, Phoenix, AZ 85004, USA
6
Department of Pharmacology and Toxicology, Arizona Health Sciences Center,
Tucson, AZ 85724, USA
7
Departments of Neurology and Cellular & Molecular Medicine, Arizona Health
Sciences Center, Tucson, AZ 85724, USA
8
Center for Insect Science, Arizona Research Laboratories, University of Arizona,
Tucson, AZ 85721, USA
*Present address: College of Medicine, University of Arizona-Phoenix, 550 E. Van
Buren Street, Phoenix, AZ 85004, USA
Author for correspondence (LLR@neurobio.arizona.edu)
Received 12 January 2012; Accepted 31 July 2012
© 2012. Published by The Company of Biologists Ltd
This is an Open Access article distributed under the terms of the Creative Commons Attribution
Non-Commercial Share Alike License (http://creativecommons.org/licenses/by-nc-sa/3.0), which
permits unrestricted non-commercial use, distribution and reproduction in any medium provided
that the original work is properly cited and all further distributions of the work or adaptation are
subject to the same Creative Commons License terms.
SUMMARY
The actin-bundling protein fascin is a key mediator of tumor invasion and metastasis and its activity drives filopodia formation, cell-shape changes
and cell migration. Small-molecule inhibitors of fascin block tumor metastasis in animal models. Conversely, fascin deficiency might underlie the
pathogenesis of some developmental brain disorders. To identify fascin-pathway modulators we devised a cell-based assay for fascin function and
used it in a bidirectional drug screen. The screen utilized cultured fascin-deficient mutant Drosophila neurons, whose neurite arbors manifest the
‘filagree phenotype. Taking a repurposing approach, we screened a library of 1040 known compounds, many of them FDA-approved drugs, for
filagree modifiers. Based on scaffold distribution, molecular-fingerprint similarities, and chemical-space distribution, this library has high structural
diversity, supporting its utility as a screening tool. We identified 34 fascin-pathway blockers (with potential anti-metastasis activity) and 48 fascin-
pathway enhancers (with potential cognitive-enhancer activity). The structural diversity of the active compounds suggests multiple molecular targets.
Comparisons of active and inactive compounds provided preliminary structure-activity relationship information. The screen also revealed diverse
neurotoxic effects of other drugs, notably the ‘beads-on-a-string’ defect, which is induced solely by statins. Statin-induced neurotoxicity is enhanced
by fascin deficiency. In summary, we provide evidence that primary neuron culture using a genetic model organism can be valuable for early-stage
drug discovery and developmental neurotoxicity testing. Furthermore, we propose that, given an appropriate assay for target-pathway function,
bidirectional screening for brain-development disorders and invasive cancers represents an efficient, multipurpose strategy for drug discovery.
A cell-based fascin bioassay identifies compounds with
potential anti-metastasis or cognition-enhancing
functions
Robert Kraft
1
, Allon Kahn
1,
*, José L. Medina-Franco
2
, Mikayla L. Orlowski
1
, Cayla Baynes
1
, Fabian López-Vallejo
2
,
Kobus Barnard
3,4
, Gerald M. Maggiora
5,6
and Linda L. Restifo
1,4,7,8,‡
RESEARCH ARTICLE
Disease Models & Mechanisms
DMM

expression levels are associated with increased invasiveness and
earlier patient death (Machesky and Li, 2010). Fascin is also
involved in tissue infiltration by circulating tumor cells (Kim et al.,
2009a). Similar associations have been reported for malignant
glioblastomas (Peraud et al., 2003; Roma and Prayson, 2005; Gunal
et al., 2008), which are prone to extensive dispersion within the
CNS (Giese et al., 2003).
The causal role of fascin in tumor phenotypes is supported by
laboratory studies in which blocking of fascin expression reduced
the invasive and/or metastatic properties of colon carcinoma
(Hashimoto et al., 2007), glioblastoma multiforme (Hwang et al.,
2008), gastric carcinoma (Fu et al., 2009; Kim et al., 2010) and breast
carcinoma (Chen et al., 2010; Al-Alwan et al., 2011). Moreover,
migrastatin-family compounds, which are potent inhibitors of
tumor invasion and metastasis in the laboratory (Shan et al., 2005),
bind to fascin and inhibit its actin-bundling activity (Chen et al.,
2010). Thus, the experimental and clinical data strongly suggest
that a fascin bioassay would be of great value for discovery of drugs
with anti-invasion and/or anti-metastasis activity.
Fascin is also required for normal brain development (Yamakita
et al., 2009) (R.K. and L.L.R., unpublished data), plausibly by
regulating neuronal differentiation (Deinhardt et al., 2011; Marín-
Vicente et al., 2011). Fascin insufficiency or dysregulation might
underlie disorders of brain development and plasticity, resulting in
intellectual disability (Kraft et al., 2006). Fascin regulation is likely
to be faulty in the brain-development disorders Rubinstein-Taybi
syndrome (Roelfsema and Peters, 2007) and tuberous sclerosis (Ess,
2006), which are caused by mutations in CREBBP (MIM#600140)
and TSC1 (MIM#605284) or TSC2 (MIM#191092), respectively.
FSCN1 is an upregulated transcriptional target of CREB binding
protein (CREBBP) (Megiorni et al., 2005), whereas fascin protein
is a target of the TSC1-TSC2 complex (Gan et al., 2008).
The connection between fascin and brain plasticity has also been
revealed by unbiased proteomics screens. Reduced fascin levels
were found in two mouse models of absence epilepsy (Ryu et al.,
2007; Ryu et al., 2008) and after long-term memory induction (Li
et al., 2010b). These data suggest that fascin levels are
downregulated by neural activity, perhaps to permit synapse-
structure changes. By contrast, fascin levels were elevated in a
polytransgenic mouse model of Down syndrome (Shin et al.,
2007). This could be a molecular feature of the brain-development
disorder or early-onset neurodegeneration, or both. In a neuron-
culture model of neuroprotection, rapid induction of ischemic
tolerance was associated with ubiquitylation of fascin, which was
subsequently degraded, as well as with transient retraction of
dendritic spines. This is consistent with the idea that fascin removal
allows dissolution of actin bundles, thereby accelerating synapse
remodeling (Meller, 2009). Finally, in a canine model of aging,
slowing of cognitive decline by environment and diet was associated
with reduced levels of fascin carbonyl, a marker of oxidation (Opii
et al., 2008). This suggests that preventing fascin oxidation
contributes to better cognitive performance. These reports point
to a role for fascin in regulating neuronal differentiation and
synaptic plasticity, which are disrupted in brain-development
disorders (Johnston, 2004) and vulnerable during aging (Burke and
Barnes, 2006). Hence, pharmacological enhancers of fascin
expression or function could be beneficial for diverse
neurodevelopmental and cognitive or behavioral conditions.
Loss-of-function Fascin-1 mutations are available in Drosophila
melanogaster and Mus musculus. The targeted Fscn1 disruption in
the mouse causes structural brain abnormalities and high rates of
neonatal death (Yamakita et al., 2009). Drosophila has a single
fascin-coding gene (Bryan et al., 1993; Kureishy et al., 2002), named
singed for the gnarled bristles of mutant flies (Bender, 1960; Cant
et al., 1994; Tilney et al., 1995; Wulfkühle et al., 1998). Wild-type
singed function is also essential for oogenesis (Cant et al., 1994),
blood cell migration (Zanet et al., 2009) and some aspects of brain
dmm.biologists.org
218
Fascin bioassay for compound screening
RESEARCH ARTICLE
TRANSLATIONAL IMPACT
Clinical issue
The findings reported here address two major clinical problems that do not
initially seem related. First, invasive cancers, including most brain tumors,
cause death due to invasion or migration, which are not inhibited by currently
available cancer treatments. Second, developmental brain disorders are not
treatable with drugs that enhance cognitive function. For both of these unmet
medical needs, a major obstacle has been the lack of cellular bioassays for
compound screening. The actin-bundling protein fascin links these two
challenging clinical conditions: excess fascin promotes tumor invasion and
metastasis, whereas insufficient fascin disrupts brain development. Thus, the
fascin pathway represents a highly desirable drug target.
Results
The filagree phenotype of fascin-deficient mutant Drosophila neurons enabled
the authors to develop a bidirectional in vitro cellular bioassay to screen for
drugs that modify the fascin pathway. A library of 1040 known compounds
(NINDS-II) was chosen on the basis of high molecular diversity, and was
screened with the aim of identifying drugs that could be repurposed for new
indications. Of these compounds, 81 were active as fascin-pathway modifiers.
There was wide pharmacological and chemical-structure diversity in each set
of active compounds (34 blockers and 48 enhancers), strongly suggesting that
each set has multiple targets along the fascin pathway. Comparison of closely
related compounds that differ in activity provided structure-activity
relationship (SAR) hypotheses that can be tested in follow-up studies. Notably,
all four of the statin compounds in the library caused a unique, reversible
neurotoxic morphological effect characterized by intraneurite nodules
containing aggregations of organelles [‘beads-on-a-string’ (BOS)]. Fascin
deficiency enhances the sensitivity of neurons to BOS.
Implications and future directions
These findings introduce a conceptually simple cell-based fascin bioassay and
apply it to identify many compounds and preliminary SAR information that
can be pursued for drug development, either by repurposing or lead
optimization. Fascin-pathway blockers could serve as anti-invasion and anti-
metastasis agents for patients with malignant carcinomas or gliomas. Fascin-
pathway enhancers could improve neurocognitive function and behavior in a
subset of children with developmental brain disorders. The potential of fascin-
pathway modifiers warrants testing in various mammalian models of fascin-
sensitive human disease. In addition, bidirectional cell-based screening could
be applied to other important biological pathways with dual functions in brain
development and tumor invasion.
The authors propose that the statin-induced BOS they observed represents
a cellular correlate of statin-associated cognitive side effects experienced by
some patients on statins. Because cholesterol is an essential nutrient in
Drosophila, this system provides a unique opportunity to study statin-
mediated neurotoxicity separately from cholesterol biosynthesis. The authors
demonstration that genetic background impacts the sensitivity of neurons to
statin-induced BOS suggests experiments to identify potential human genetic
risk factors for statin-associated cognitive deficits. More generally, this primary
neuron culture system in Drosophila holds great promise as a neurotoxicity
screening platform with the ability to identify biologically relevant gene-by-
environment interactions.
Disease Models & Mechanisms
DMM

development (R.K. and L.L.R., unpublished data), but not for
viability (Bender, 1960). We discovered that singed mutations cause
a neuronal morphogenesis defect, ‘filagree’, when developing
mutant CNS neurons are cultured in vitro (Kraft et al., 2006).
Filagree neurite arbors have exaggerated clockwise curvature and
erratic variation in neurite caliber, but no reduction in length,
branching or axon-dendrite ratio (Kraft et al., 2006). Filagree
neurons have striking disruptions of their actin cytoskeleton which,
like other singed phenotypes, can be explained by failure of actin
bundling (Cant et al., 1994; Guild et al., 2003; Kraft et al., 2006;
Zanet et al., 2009). Because decreasing fascin function causes
increasing severity of the filagree phenotype, we reasoned that
cultured neurons could provide a cellular bioassay for fascin
function.
The use of a Drosophila cell-based fascin bioassay for drug
discovery is justified by the phylogenetic conservation of fascin
(Hashimoto et al., 2011) and of the pathways underlying cognition
(Greenspan and Dierick, 2004; Inlow and Restifo, 2004; Bolduc and
Tully, 2009), tumor invasion and metastasis (Miles et al., 2011). Here
we present the results of a bidirectional screen for pharmacological
modifiers of the filagree neuronal morphogenesis defect.
RESULTS
Drug screen design using the fascin bioassay
Filagree is a highly penetrant, quantifiable, pan-neuronal
phenotype of fascin-deficient singed-mutant neurons cultured
from the developing CNS of Drosophila mature larvae or young
pupae (Fig. 1A-C) (Kraft et al., 2006). This developmental interval
corresponds to high levels of singed transcript accumulation in
wild-type CNS (Kaitlin L. Bergfield, R.K. and L.L.R., unpublished).
The filagree phenotype is so distinctive and so consistent that
trained observers can easily distinguish singed-mutant versus
wild-type population cultures, typically containing 1500-2000
neurons each. In fact, both humans and a computational method
for neurite-curvature quantification can classify individual
photomicrographs of mutant or wild-type neurons with ≥90%
accuracy (Kraft et al., 2006). To anticipate how much restoration
of function would be required to rescue the fascin-deficient
filagree phenotype, we asked whether filagree is recessive, like
other singed phenotypes. We quantified the neurite-curvature
distributions of wild-type and sn
X2
/+ cultured larval CNS
neurons, which have 100% and 50% of normal fascin function,
respectively (Fig. 1D). The two distributions were statistically
Disease Models & Mechanisms
219
Fascin bioassay for compound screening
RESEARCH ARTICLE
Fig. 1. Genetic and pharmacological modification of
neurite curvature. (A-C,F-I) Phase-contrast images
(60) of neurons cultured for 3 d.i.v. from the CNS of
wandering third instar larvae. Magnification is the same
throughout. (A-C)
Loss-of-function singed mutations
increase neurite curvature and disrupt proximal-to-
distal tapering. (A)
Wild-type (sn
+
/sn
+
), OreR-C
laboratory strain. (B)
A partial loss-of-function
(hypomorphic) mutation (sn
3
/sn
3
) causes a moderate
filagree phenotype. (C)
A null mutation (sn
X2
/Y) causes
a severe filagree phenotype. (D,E)
Mean curvature
distributions of neurite arbors of cultured neurons with
differing genotypes, plotted with soft binning. Normal-
distribution curves were fit to each population and
scaled (y-axis) to the corresponding histograms.
(D)
Genetically marked -MB neurons. The increased
curvature of sn
3
/sn
X2
(blue) neurons is easily seen. The
similarity of sn
X2
/+(red) and sn
+
/sn
+
(green) curvature
distributions demonstrates that filagree is recessive.
(E)
Random CNS neurons. The mean neurite curvature
distribution of sn
3
/sn
3
mutant neurons (magenta) is
significantly increased over that of wild-type (sn
+
/sn
+
,
OreR-C) neurons (green). (F-I)
Exposure to drugs in vitro
can modify the filagree phenotype of fascin-deficient
sn
3
/sn
3
neurons. (F,G)
Two examples of filagree
decreasers (fascin-pathway enhancers): estradiol
propionate, 50
M (E) and Anisindione, 50
M (G).
Neurite curvature, especially of terminal neurites, is
reduced and the smooth proximal-to-distal tapering is
restored. (H,I)
Two examples of filagree increasers
(fascin-pathway blockers): griseofulvin, 50
M (H) and
acetyltryptophan, 50
M (I). Note the exaggerated
neurite curvature and frequent expansions of neurite
width.
Disease Models & Mechanisms
DMM

indistinguishable, whereas neurons from sn
3
/sn
X2
(a near-null
genotype) and sn
X2
/+ were very different (Welchs t-test,
P<110
–18
; Fig. 1D). Therefore, the results show that the singed
neurite-curvature phenotype is recessive and that rescue of
singed-mutant neurite-arbor morphology requires no more than
50% of wild-type fascin function.
A bidirectional drug-screen design requires that the baseline
neuronal morphology be intermediate and distinct from both wild
type (Fig. 1A) and singed-null (sn
X2
/Y; Fig. 1C), allowing detection
of both drug-induced worsening and drug-induced rescue of the
filagree defect (Fig. 1B). The neurite-curvature distributions of the
severe hypomorph, sn
3
/sn
3
(Fig. 1B), and the wild-type (Fig. 1A) were
significantly different (Welchs t-test, P<110
–13
; Fig. 1E), with
greater overlap of distributions than between wild type and sn
3
/sn
X2
(Kraft et al., 2006). This is consistent with the relative function among
the genotypes. Moreover, the sn
3
mutation leaves the fascin open
reading frame intact, allowing small amounts of normal protein to
be produced (Paterson and O’Hare, 1991; Cant et al., 1994). Thus,
sn
3
/sn
3
neurons have a desirable neuronal phenotype, and contain
some wild-type fascin protein that can serve as a drug target.
The striking nature of the filagree defect makes it suitable for
use in a modifier screen based on direct phenotype observation.
Using an approach that parallels genetic-modifier screens
commonly performed with model organisms, we conducted a
chemical screen to identify small molecules that induce obvious
changes in neuronal phenotype. Compounds were tested at 10
M and 50 M by adding them to the cultures at the time of
plating the dissociated neurons, and evaluating their effects on
the filagree phenotype after 3 days in vitro (d.i.v.). Thus, the
neurons were exposed to the drug during the entire period of
neurite-arbor morphogenesis. To facilitate the drug-screening
process, we replaced quantitative analysis of immunostained
images of randomly sampled neurons with holistic scoring by
phase-contrast microscopy of populations of living cells, typically
1500-2000 neurons per ~50-mm
2
culture well.
Selection and diversity analysis of the NINDS-II compound
collection
Inspired by striking examples of new uses for existing drugs, we
took a ‘repurposing’ approach, also called ‘repositioning’ or
‘indication switch’ (Ashburn and Thor, 2004; Dueñas-González et
al., 2008). For example, minoxidil was developed as an oral anti-
hypertensive drug, but is now most popular as a topical treatment
(e.g. Rogaine®) for hair loss (Zins, 1988). More dramatic is the
repurposing of thalidomide, much-maligned for its teratogenic
effects when taken during pregnancy (Ito and Handa, 2012), but
now used to treat multiple myeloma, a bone marrow malignancy
(Palumbo et al., 2008). Repurposing screens have the advantage of
testing compounds whose pharmacology and side-effect profiles
are partially understood.
Because fascin acts in diverse pathways (Jayo and Parsons, 2010;
Hashimoto et al., 2011), modification of the filagree defect could
occur through several potential drug targets, including but not
limited to fascin itself. This called for a chemically diverse screening
library. The new indications, including brain tumors and
neurodevelopmental disorders, made good representation of
neuroactive compounds highly desirable. A collaboration between
the National Institute of Neurological Disorders and Stroke
(NINDS) and the private sector (Heemskerk, 2005) produced a
screening library of 1040 compounds (NINDS-II; supplementary
material Table S1), comprised primarily of FDA-approved drugs
for diverse indications, as well as natural products and laboratory
reagents; many of these compounds are neuroactive. Screens of
the NINDS-II library with various assays and protocols identified
drugs with potential utility for Huntingtons disease, spinomuscular
atrophy, amyotrophic lateral sclerosis (ALS), stroke and familial
dysautonomia (Aiken et al., 2004; Piccioni et al., 2004; Slaugenhaupt
et al., 2004; Stavrovskaya et al., 2004; Rothstein et al., 2005; Vincent
et al., 2005; Wang et al., 2005a; Wang et al., 2005b; Desai et al.,
2006). The antibiotic ceftriaxone was protective in diverse
neurodegeneration assays, leading to Phase III clinical trials for ALS
(Traynor et al., 2006) (ClinicalTrials.gov identifier NCT00349622).
This library does not contain any migrastatin-family compounds.
We evaluated the chemical diversity of the NINDS-II compounds
(Fig. 2) based on: (i) the types and distribution of molecular scaffolds
(Bemis and Murcko, 1996; Singh et al., 2009), (ii) measures of
molecular similarity based on shared substructural features (Willett
et al., 1998) and (iii) the chemical-space distribution of the
compounds (Maggiora and Shanmugasundaram, 2011). The 1040
compounds of the collection are distributed over 617 scaffolds (Fig.
2B), of which 551 are cyclic systems. The highly populated scaffolds
(Fig. 2C) are indoles, pyridines, quinolines and sterols, common
among drug-like small molecules. Indicative of high diversity, 77%
(424) of the cyclic scaffolds are singletons, i.e. populated by a single
compound. From the perspective of the compounds, ~60% of them
cover ~23% of the cyclic scaffolds. In other words, this relatively
small collection allows sampling of a relatively large number of
scaffolds. The molecular fingerprint, based on 166 structural
features (Fig. 2D), of each compound was compared pair-wise with
all others, and the Tanimoto coefficients were computed as
measures of similarity (Maggiora and Shanmugasundaram, 2011).
Overall molecular diversity is inversely proportional to the average
Tanimoto similarity for all pair-wise comparisons. For the NINDS-
II library, low similarity values (mean 0.295; median 0.284) reflect
high diversity and compare favorably to those of the ~1500-
compound DrugBank database (Wishart et al., 2008; Singh et al.,
2009). The distribution of compounds in ‘chemical space,’ where
the similarity of any pair is inversely related to the distance between
them (Maggiora and Shanmugasundaram, 2011), was represented
in a three-dimensional (3D) plot (Fig. 2E,F). The compounds are
spread throughout the space, reflecting the high diversity of the
collection. In summary, the high diversity of the modestly sized
NINDS-II collection make it an efficient tool for conducting the
first compound screen on the basis of the first fascin bioassay.
A bidirectional drug screen reveals diverse fascin-pathway
enhancers and blockers
Of the 1040 compounds tested, 81 (7.8%) were active in the fascin
bioassay at 10 and/or 50 M concentrations, based on holistic
scoring. We identified both drug-induced decreasers and increasers
of the filagree phenotype (Figs 1, 3, 4; Table 1). Filagree decreasers
(fascin-pathway enhancers; supplementary material Table S2)
rescued the neurite-arbor shape defect of fascin-deficient mutant
neurons, allowing them to extend neurites with normal trajectory
and tapering (Fig. 1, compare F and G with A). Filagree increasers
(fascin-pathway blockers; supplementary material Table S3)
dmm.biologists.org
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Fascin bioassay for compound screening
RESEARCH ARTICLE
Disease Models & Mechanisms
DMM

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TL;DR: Understanding the functions and regulation of microtubule dynamics in the growth cone provides new insights into the molecular mechanisms of axon guidance.
Abstract: Precise modulation of the cytoskeleton is involved in a variety of cellular processes including cell division, migration, polarity, and adhesion. In developing post-mitotic neurons, extracellular guidance cues not only trigger signaling cascades that act at a distance to indirectly regulate microtubule distribution, and assembly and disassembly in the growth cone, but also directly modulate microtubule stability and dynamics through coupling of guidance receptors with microtubules to control growth-cone turning. Microtubule-associated proteins including classical microtubule-associated proteins and microtubule plus-end tracking proteins are required for modulating microtubule dynamics to influence growth-cone steering. Multiple key signaling components, such as calcium, small GTPases, glycogen synthase kinase-3β, and c-Jun N-terminal kinase, link upstream signal cascades to microtubule stability and dynamics in the growth cone to control axon outgrowth and projection. Understanding the functions and regulation of microtubule dynamics in the growth cone provides new insights into the molecular mechanisms of axon guidance.

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TL;DR: The fruit fly Drosophila melanogaster has been used for modeling cancer and as an in vivo tool for the validation and/or development of cancer therapeutics and is emerging as a powerful tool for high-throughput screening and should significantly reduce the cost and time associated with drug development.
Abstract: The fruit fly Drosophila melanogaster has been used for modeling cancer and as an in vivo tool for the validation and/or development of cancer therapeutics. The impetus for the use of Drosophila in cancer research stems from the high conservation of its signaling pathways, lower genetic redundancy, short life cycle, genetic amenability, and ease of maintenance. Several cell signaling pathways in Drosophila have been used for cancer drug development. The efficacy of combination therapy and uptake/bioavailability of drugs have also been studied. Drosophila has been validated using several FDA-approved drugs, suggesting a potential application of this model in drug repurposing. The model is emerging as a powerful tool for high-throughput screening and should significantly reduce the cost and time associated with drug development. In this review we discuss the applications of Drosophila in cancer drug development. The advantages and limitations of the model are discussed.

42 citations


Cites background or methods from "A cell-based fascin bioassay identi..."

  • ...Cancer Targets and Pathways Studied in Drosophila for the Validation/Development of Cancer Drugs Cancer Target/Pathway Cancer Type Model Used Refs JAK/STAT Multiple Cells [21,26–28] RET receptor tyrosine kinase MTC Adult fly and larvae [31–33,35] APC/Wnt Colorectal Cells and adult fly [40,42] Notch Leukemia Stem cells [47] Ras Not defined Larval eye antennal disc [22] EGFR Not defined Eye and wing imaginal disc [56] l(2)gl Brain Larvae [60] ALK Neuroblastoma Adult eye [70,71] Fascin Glioma Neurons [76] TFIIH Not defined Larval wing disc [84] Topo II Not defined Adult eye cells [87] Hh Not defined Tissues [89]...

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  • ...To identify the modulators of the fascin pathway, a cell-based bidirectional drug screening assay was developed in Drosophila for the identification of agents with antimetastasis or cognitive-enhancing activities [76]....

    [...]

  • ...Acivicin Inhibited tumor formation in Drosophila by inhibiting CTP synthase [22] Gefitinib and erlotinib Suppressed eye and wing phenotypes induced by EGFR in Drosophila; inhibited dp-ERK1/2 in the eye and wing imaginal discs of wild-type larvae [56] Artemisinin, curcumin Exhibited anticancer activities against brain cancer through generation of reactive oxygen species [60] TAE684, crizotinib Ameliorated the rough-eye phenotype caused by overexpression of hALK and hALK in Drosophila; the effect of crizotinib was less than that of TAE684 [70,71] Imipramine Inhibited fascin pathway in Drosophila; known mediator of tumor invasion and metastasis [76] Triptolide Induced apoptosis in third-instar larval wing discs of Drosophila by inhibiting the ATPase activity of the XPB subunit of TFIIH [84] F14512 Exhibited antiproliferative properties in Drosophila cells; stabilized ternary Topo II– DNA-cleavable complexes at unique sites located in moderately repeated sequences [87] AY9944 Inhibited Hh-induced internalization of the transmembrane protein Ptc as well as the expression of the Hh target gene en; depleted cholesterol from the plasma membrane and its intracellular accumulation in Drosophila tissues [89] Bouvardin Enhanced the effects of radiation in Drosophila larvae through inhibition of the elongation step of protein synthesis [92] Trametinib and fluvastatin Improved tracheal development and reduced over-proliferation and whole-animal toxicity in a Ras–PTEN Drosophila lung cancer model [94]....

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Journal ArticleDOI
TL;DR: Major trends in current drug discovery and their impact on the mining and population of chemical space are reviewed and different approaches to develop screening libraries with confined chemical spaces balancing physicochemical properties are surveyed.
Abstract: Introduction: The concept of chemical space has broad applications in drug discovery. In response to the needs of drug discovery campaigns, different approaches are followed to efficiently populate, mine and select relevant chemical spaces that overlap with biologically relevant chemical spaces. Areas covered: This paper reviews major trends in current drug discovery and their impact on the mining and population of chemical space. We also survey different approaches to develop screening libraries with confined chemical spaces balancing physicochemical properties. In this context, the confinement is guided by criteria that can be divided in two broad categories: i) library design focused on a relevant therapeutic target or disease and ii) library design focused on the chemistry or a desired molecular function. Expert opinion: The design and development of chemical libraries should be associated with the specific purpose of the library and the project goals. The high complexity of drug discovery and the inh...

39 citations


Cites background from "A cell-based fascin bioassay identi..."

  • ...Analysis of the structural diversity of the active compounds suggested the involvement of multiple molecular targets [27]....

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Journal ArticleDOI
TL;DR: The status and key questions surrounding investigations of fascin-1 as a novel, early prognostic biomarker in colorectal cancer are discussed and ongoing pre-clinical research into new migration inhibitory and anti-metastatic compounds that alter the actin cytoskeleton are discussed.
Abstract: Fascin-1 is a filamentous actin-binding protein that crosslinks actin microfilaments into tight, parallel bundles. These bundles are important for the extension of microspikes, filopodia and invadopodia from cell surfaces and for the functionality of these protrusions in cell migration and/or dynamic sensing of the local microenvironment. Fascin-1 is absent in normal colonic epithelium, but its upregulation in colorectal adenomas and adenocarcinomas and its correlation with an aggressive clinical course has piqued the interest of many laboratories with research interests in cancer metastasis. This report summarizes current knowledge of the molecular interactions of fascin-1 in relation to its activities and mechanisms of upregulation in colorectal carcinoma cells. The status and key questions surrounding investigations of fascin-1 as a novel, early prognostic biomarker in colorectal cancer are discussed. Ongoing pre-clinical research into new migration inhibitory and anti-metastatic compounds that alter the actin cytoskeleton, and the goal of targeting fascin-1, is also discussed.

20 citations


Cites background from "A cell-based fascin bioassay identi..."

  • ...The setup of a cell-based assay to screen for small molecules that could rescue the aberrant morphology of fascin-deficientDrosophila neurons [55] has led to the development of a series of thiazole derivative compounds [56]....

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Proceedings ArticleDOI
01 Nov 2015
TL;DR: A microfluidic technology-based tissue-dissociation device has for the first time been designed, fabricated and characterized for the purpose of primary neuronal cell culture of freshly explanted, enzyme-treated Drosophila larval central nervous system into individual, viable neurons capable of robust outgrowth during in vitro culture.
Abstract: A microfluidic technology-based tissue-dissociation device has for the first time been designed, fabricated and characterized for the purpose of primary neuronal cell culture. The system has been utilized for controlled dissociation, under an oscillatory flow field, of freshly explanted, enzyme-treated Drosophila larval central nervous system (CNS) into individual, viable neurons capable of robust outgrowth during in vitro culture. Device dimensions, constriction height and width, and operating conditions, flow-rate amplitude and frequency, have been determined based on video microscopy as well as quantitative analyses of the subsequent neuron-culture results.

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Cites background from "A cell-based fascin bioassay identi..."

  • ...Those cellular models can be used to screen for drugs with potential therapeutic value [4]....

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References
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Journal ArticleDOI
TL;DR: Evidence is provided that primary neuron culture using a genetic model organism can be valuable for early-stage drug discovery and developmental neurotoxicity testing and it is proposed that bidirectional screening for brain-development disorders and invasive cancers represents an efficient, multipurpose strategy for drug discovery.
Abstract: SUMMARY The actin-bundling protein fascin is a key mediator of tumor invasion and metastasis and its activity drives filopodia formation, cell-shape changes and cell migration. Small-molecule inhibitors of fascin block tumor metastasis in animal models. Conversely, fascin deficiency might underlie the pathogenesis of some developmental brain disorders. To identify fascin-pathway modulators we devised a cell-based assay for fascin function and used it in a bidirectional drug screen. The screen utilized cultured fascin-deficient mutant Drosophila neurons, whose neurite arbors manifest the 'filagree' phenotype. Taking a repurposing approach, we screened a library of 1040 known compounds, many of them FDA-approved drugs, for filagree modifiers. Based on scaffold distribution, molecular-fingerprint similarities, and chemical-space distribution, this library has high structural diversity, supporting its utility as a screening tool. We identified 34 fascin-pathway blockers (with potential anti-metastasis activity) and 48 fascin- pathway enhancers (with potential cognitive-enhancer activity). The structural diversity of the active compounds suggests multiple molecular targets. Comparisons of active and inactive compounds provided preliminary structure-activity relationship information. The screen also revealed diverse neurotoxic effects of other drugs, notably the 'beads-on-a-string' defect, which is induced solely by statins. Statin-induced neurotoxicity is enhanced by fascin deficiency. In summary, we provide evidence that primary neuron culture using a genetic model organism can be valuable for early-stage drug discovery and developmental neurotoxicity testing. Furthermore, we propose that, given an appropriate assay for target-pathway function, bidirectional screening for brain-development disorders and invasive cancers represents an efficient, multipurpose strategy for drug discovery.

22 citations


Frequently Asked Questions (1)
Q1. What are the contributions in "A cell-based fascin bioassay identifies compounds with potential anti-metastasis or cognition-enhancing functions" ?

This paper developed a bioassay for drug discovery using the product of the FSCN1 genes, which is a highly conserved actin-bundling protein and has diverse roles in the developmental and physiological regulation of cellular morphology and function.