Discovery of a series of thiazole derivatives as novel inhibitors of metastatic cancer cell migration and invasion

Article abstract of DOI:10.1021/ml300322n

Effective inhibitors of cancer cell migration and invasion can potentially lead to clinical applications as a therapy to block tumor metastasis, the primary cause of death in cancer patients. To this end, we have designed and synthesized a series of thiazole derivatives that showed potent efficacy against cell migration and invasion in metastatic cancer cells. The most effective compound, 5k, was found to have an IC₅₀ value of 176 nM in the dose-dependent transwell migration assays in MDA-MB-231cells. At a dose of 10 μM, 5k also blocked about 80% of migration in HeLa and A549 cells and 60% of invasion of MDA-MB-231 cells. Importantly, the majority of the derivatives exhibited no apparent cytotoxicity in the clonogenic assays. The low to negligible inhibition of cell proliferation is a desirable property of these antimigration derivatives because they hold promise of low toxicity to healthy cells as potential therapeutic agents. Mechanistic studies analyzing the actin cytoskeleton by microscopy demonstrate that compound 5k substantially reduced cellular f-actin and prevented localization of fascin to actin-rich membrane protrusions. These results suggest that the antimigration activity may result from impaired actin structures in protrusions that are necessary to drive migration.

Full text of DOI:10.1021/ml300322n

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Letter
Discovery of a Series of Thiazole Derivatives as Novel
Inhibitors of Metastatic Cancer Cell Migration and Invasion
Shilong Zheng, Qiu Zhong, Quan Jiang, Madhusoodanan Mottamal, Qiang Zhang,
Naijue Zhu, Matthew E. Burow, Rebecca A. Worthylake, and Guangdi Wang
ACS Med. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/ml300322n • Publication Date (Web): 15 Jan 2013
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Discovery of a Series of Thiazole Derivatives as Novel Inhibi-
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Shilong Zheng,1* Qiu Zhong,2 Quan Jiang,2 Madhusoodanan Mottamal,1 Qiang Zhang,1 Naijue Zhu,2
Matthew E. Burow,3 Rebecca A. Worthylake,4 and Guangdi Wang1, 2*
1Department of Chemistry and 2RCMI Cancer Research Program, Xavier University of Louisiana, 1 Drexel Drive, New
Orleans, LA 70125
3Department of Medicine, Section of Hematology and Medical Oncology, Tulane University School of Medicine, New Orleꢀ
ans, LA 70112
4Department of Oral Biology, Louisiana State University Health Sciences Center, New Orleans, LA 70119
KEYWORDS: Thiazole derivatives, synthesis, anti-migration, anti-invasion, f-actin, fascin.
Supporting Information Placeholder
ABSTRACT: Effective inhibitors of cancer cell migration and invasion can potentially lead to clinical applications as therapy to
block tumor metastasis, the primary cause of death in cancer patients. To this end we have designed and synthesized a series of
thiazole derivatives that showed potent efficacy against cell migration and invasion in metastatic cancer cells. The most effective
compound, 5k, was found to have an IC50 value of 176 nM in the doseꢀdependent transwell migration assays in MDAꢀMBꢀ231cells.
At the dose of 10 ꢁM, 5k also blocked about 80% of migration in HeLa and A549 cells and 60% of invasion of MDAꢀMBꢀ231
cells. Importantly, the majority of the derivatives exhibited no apparent cytotoxicity in the clonogenic assays. The low to negligible
inhibition of cell proliferation is a desirable property of these antiꢀmigration derivatives because they hold promise of low toxicity
to healthy cells as potential therapeutic agents. Mechanistic studies analyzing the actin cytoskeleton by microscopy demonstrate
that compound 5k substantially reduced cellular fꢀactin, and prevented localization of fascin to actinꢀrich membrane protrusions.
These results suggest that the antiꢀmigration activity may result from impaired actin structures in protrusions that are necessary to
drive migration.
Metastasis is the major cause of death in cancer patients:
nearly 90% mortality has been attributed to metastatic spread
of the disease rather than to the primary tumor.1ꢀ3 Decades of
intensive research have focused on the search for therapeutic
solutions targeting cancer cell migration and invasion, and
angiogenesis.4ꢀ7 Metastasis is a complex process, involving
multiple steps that include cancer cell motility, intravasation,
transit and survival in the circulation, extravasation and
growth at a new site. While in theory, inhibition of any of theꢀ
se metastatic stages will prevent the formation of tumors at
remote sites, clinically the window of opportunity to block
metastasis may not be as optimal as one might hope for.8 For
example, stages involving cancer cell survival in the circulaꢀ
tion, arrest and extravasation may not be ideal targets for deꢀ
velopment of therapeutic solutions as these processes appear
to occur relatively fast, in large numbers, and are less vulneraꢀ
ble to drug interference. On the other hand, growth of cancer
cells in secondary sites takes much longer to cause irreversible
damage, thus offering a broader time window for prevention
of metastasis.8,9
drugs such as protease inhibitors, chemokine antagonists, kiꢀ
nase blockers, adhesion modifiers, and antiꢀinflammation
agents.9 Search for improved, more potent and less toxic drugs
for metastasis intervention remains an ongoing effort.
Thiazole is a common structural motif in a large number of
18, 24ꢀ28
antiꢀcancer agents,
including the clinically used
BCR/ABL inhibitor dasatinib for chronic myelogenous leuꢀ
kemia (CML).29 These thiazole derivatives have been reported
to inhibit cancer cell growth and proliferation, and vasculature
formation through a variety of mechanisms and therapeutic
targets. In an effort to design and synthesize new thiazole
compounds for potential antiꢀcancer agents, we have found
that a methyl substitution on the thiazole nitrogen would draꢀ
matically reduce the antiꢀproliferation activity. However, subꢀ
sequent cell motility assay revealed that this structural modifiꢀ
cation allowed the compounds to inhibit cell migration. One
such thiazole derivative (5a) showed strong ability to block
cancer cell migration but exhibited no apparent cellular toxiciꢀ
ty in both cell survival and colony formation assays. This
finding prompted us to design a series of thiazole derivatives
by varying the substitution groups on the thiazole ring. We
report here the preparation and biological activity evaluation
of 37 such derivatives.
Small molecule drugs such as matrix metalloproteinases inꢀ
17ꢀ23
hibitors10ꢀ16 and vascular disrupting agents
have been deꢀ
veloped to block metastasis, so far with only limited clinical
success. Most chemotherapies target cancer cell proliferation
as means to inhibit dissemination, leading to toxicity to
healthy cells as well as acquired resistance in cancer cells. The
metastasisꢀmodifying processes, however, may be more effecꢀ
tively influenced by long term treatment of nonꢀcytotoxic
As shown in Scheme 1, the designed derivatives were synꢀ
thesized following the general procedures as detailed below.
The condensationꢀcyclization of 2ꢀbromoꢀ1ꢀphenylethanone
(1a) and 2ꢀbromoꢀ1ꢀ(2,4ꢀdimethylphenyl)ethanone (1b) with
thiourea afforded near quantitative yield of 2ꢀaminoꢀ4ꢀ
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phenylthiazole (2a) and 2ꢀaminoꢀ4ꢀ(2, 4ꢀdimethylphenyl)
with the carboxylic acids provided the amides 3, and further
alkylation of 3 led to the desired derivatives 4 and their correꢀ
sponding isomers 5.18
thiazole (2b) in refluxing ethanol, respectively.18,30 Following
acylation of 2a and 2b by acyl chloride or direct N,N'ꢀ
dicyclohexylcarbodiimideꢀpromoted coupling of 2a and 2b
1
2
3
Scheme 1. Preparation of a series of thiazole derivatives as novel antiꢀmigration and antiꢀinvasion agents
4
5
6
7
R
R
O
a
b
Br
O
N
N
R
N
H
R1
S
8
NH2
S
9
1
2
3
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1a, R = H
3a R = H, R1 = thiophen-2-yl
3b R = H, R1 = furan-2-yl
3i
3j
R = H, R1 = pyridin-4-yl
R = H, R1 = phenyl
2a, R = H
1b, R = 2,4-dimethyl
2b, R = 2,4-dimethyl
3c R = H, R1 = 4-chlorophenyl
2c, R = 2,4,6-trimethoxy
3d R = H, R1 = 4-bromophenyl
3k R = H, R1 = cyclopentyl
3l
1c, R = 2,4,6-trimethoxy
R = H, R1 = cyclohexyl
R = H, R1 = n-pentyl
3e R = H, R1 =3,4,5-trimethoxyphenyl 3m
3f R = 2,4-dimethyl, R1 = thiophen-2-yl3n R = H, R1 = n-undecyl
3g R = H, R1 = 3,4-dimethoxyphenyl 3o
3h R = H, R1 = pyridin-3-yl
R = 2,4-dimethyl, R1 = phenyl
3p
R = 2,4,6-trimethoxy, R1 = phenyl
R
R
R2
O
N
c
O
N
+
N
R1
S
N
R1
S
R2
5
4
5a R = H, R1 = thiophen-2-yl, R2 = Me
5b R = H, R1 = furan-2-yl, R2 = Me
4a R = H, R1 = 4-bromophenyl, R2 = Me
4b R = 2,4-dimethyl, R1 = thiophen-2-yl, R2 = Me
4c R = H, R1 = 3,4-dimethoxyphenyl, R2 = Me
4d R = H, R1 = furan-2-yl, R2 = Et
5c R = H, R1 = 4-chlorophenyl, R2 = Me
5d R = H, R1 = 4-bromophenyl, R2 = Me
5e R = H, R1 =3,4,5-trimethoxyphenyl, R2 = Me
5f R = 2,4-dimethyl, R1 = thiophen-2-yl, R2 = Me
5g R = H, R1 = 3,4-dimethoxyphenyl, R2 = Me
5h R = H, R1 = pyridin-3-yl, R2 = Me
5i R = H, R1 = thiophen-2-yl, R2 = Et
5j R = H, R1 = phenyl, R2 = Me
5k R = 2,4-dimethyl, R1 = phenyl, R2 = Me
5l R = 2,4,6-trimethoxy, R1 = phenyl, R2 = Me
4e R = H, R1 = phenyl, R2 = Me
4f R = H, R1 = cyclopentyl, R2 = Me
4g R = H, R1 = cyclohexyl, R2 = Me
4h R = H, R1 = n-pentyl, R2 = Me
4i R = H, R1 = n-undecyl, R2 = Me
4j R = 2,4,6-trimethoxy, R1 = phenyl, R2 = Me
Reagents and conditions: (a) thiourea, ethanol, reflux; (b) Method A: R1CO2H, dicyclohexylcarbodimide, DMAP, CH2Cl2, rt;
Method B: R1COCl, DMAP, CH2Cl2, 0 oC ~ rt; (c) i). NaH, THF, 0 oC ~ rt; ii). MeI or EtBr 0 oC ~ rt.
Interestingly, alkylation of 3 formed two different isomers 4
and 5 depending on which nitrogen on amides 3 to take part in
the alkylation. The result showed that the formation ratio of
isomers 4 and 5 was clearly linked to the type of R1 groups in
the amides 3. If R1 groups were alkyl groups, exclusive isoꢀ
mers 4 (4f, 4g, 4h and 4i) were acquired and possible isomers
5 as minor products (< 1%) were found only by GCꢀMS analyꢀ
sis. However, when R1 groups turn into aryl groups, the forꢀ
mation of isomers 5 (5d and 5f) increased significantly to exꢀ
ceed the formation of isomers 4 (4a and 4b) except the ethylaꢀ
tion product of 3b. In fact, most of isomers 5 (5aꢀc, 5e, 5hꢀi
and 5k) were the only purified products obtained, due to negliꢀ
gible amounts of their corresponding isomers 4 as products.
To determine the exact structures of derivative 4e and its
corresponding isomer 5j, single crystals of 4e and 5j were
grown by vapor diffusion of hexane into the dichloromethane
solutions of the compounds and analyzed by Xꢀray crystallogꢀ
raphy (The detailed crystal data are provided in the supporting
information). The results are presented in Figure 1. The Xꢀray
single crystal analysis of isomers 4e and 5j further confirmed
their respective structures.
For derivatives 4 and their corresponding isomers 5, the
structural differences were such that the derivatives 4 had the
thiazole ring moiety whereas isomers 5 contained the thiazolꢀ
2(3H)ꢀyliene ring. The formation of thiazolꢀ2(3H)ꢀyliene ring
of isomers 5 considerably undermined the aromaticity of the
original thiazole ring and further decreased the deshielding of
the thiazole protons by a ring current of πꢀelectrons. Therefore,
the thiazolꢀ2(3H)ꢀyliene ring of isomers 5 showed a relatively
higher field 1H chemical shift (~6.5 ppm) than that of the thiaꢀ
zole ring of the corresponding isomers 4 (~7.1 ppm). The
decrease of aromaticity of the thiazolꢀ2(3H)ꢀyliene ring of
isomers 5 increased their polarity, as reflected in the longer
retention times of derivatives 5 compared to derivatives 4 in
GCꢀMS analysis. Similarly, the Rf value of derivatives 5 was
smaller than that of derivatives 4 in silica gelꢀ based TLC.
4e
5j
Figure 1. ORTEP plot of molecular structures of 4e and 5j.
Table 1. List of all synthetic derivatives with migration
inhibition and colony formation data when MDAꢀMBꢀ231
breast cancer cells were treated with 10 ꢁM derivatives
Compounds Migration
Effect
on
cell
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active 71.4 % inhibition (3g) to a slight (3%) stimulation of
Inhibition (% of proliferation
(colony
(% of
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3
4
5
6
7
8
migration (3d). The activity variation of the amides 3 suggests
that R1 group may be important but not necessary in conferring
the desired antiꢀmigration property. The methylation transforꢀ
mation of the amides 3 (3bꢀf, 3h, 3j, 3o and 3p) to the desired
thiazole derivatives 5 (5bꢀf, 5h, 5j ꢀl) mostly improves the
antiꢀmigration activity of the compounds with the exception of
3a (65.5% inhibition) to 5a (56.7% inhibition) and 3g (81.4%
inhibition) to 5g (64.1% inhibition). This conversion led to the
discovery of the most potent derivatives 5j (87% inhibition,
IC50 = 0.189 ꢁM) and 5k (85.7% inhibition, IC50 = 0.176 ꢁM).
Upon methylation of the amides 3, the resultant isomers 4 (4aꢀ
c, 4e and 4j) have consistently lower activities than those of
the corresponding isomers 5 (5d, 5f, 5g, 5j and 5l). Additionalꢀ
ly, it is noted that replacement of the methyl moiety with an
ethyl group in 5a (56.7% inhibition) slightly increased the
activity of 5i (67.9%).
vehicle control)
formation)
vehicle control)
100.0%
103.6%
110.9%
85.9%
98.8%
95.0%
98.6%
80.9%
67.5%
57.3%
102.8%
95.5%
105.2%
99.8%
103.4%
90.7%
71.5%
100.0%
86.0%
45.5%
34.5%
88.0%
78.0%
103.0%
46.5%
40.9%
18.6%
80.8%
32.3%
31.3%
68.2%
92.7%
75.2%
28.3%
33.7%
59.2%
78.2%
72.2%
43.5%
54.5%
39.2%
54.3%
72.7%
71.4%
80.0%
91.5%
43.3%
77.6%
28.1%
59.7%
26.5%
37.1%
35.9%
62.0%
32.1%
13.0%
14.3%
40.6%
DMSO
2a
2b
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
4a
4b
4c
4d
4e
4f
9
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Given the potent antiꢀmigration efficacy demonstrated by
most of the thiazole derivatives, we decided to study the dose
response of the most potent derivatives to obtain their IC50
values in suppressing the transwell migration of the MDAꢀMBꢀ
231 cells. As shown in Table 2, the IC50 values for the 10
selected derivatives varied from 2.87 ꢁM to 0.176 ꢁM.
85.0%
108.8%
107.7%
97.7%
97.1%
96.5%
123.4%
132.4%
97.5%
127.5%
111.1%
110.4%
85.0%
107.3%
98.2%
63.8%
Table 2. IC50 values for 10 most potent antiꢀmigration
compounds in MDAꢀMBꢀ231 breast cancer cells
4g
4h
4i
4j
5a
5b
5c
5d
5e
5f
5g
5h
5i
Compounds
3a
3i
IC50 (ꢂM)
2.49
2.87
75.4%
102.3%
40.9%
111.5%
97.7%
25.2%
3j
1.29
3n
3o
4e
5c
5i
1.01
0.839
0.366
1.12
We
perꢀ
next
5j
5k
5l
120.9%
94.0%
2.08
5j
5k
0.189
0.176
To determine the effects of the synthesized thiazole derivaꢀ
formed clonogenic assays on the breast cancer cells treated
with the compounds to rule out any indirect effect on cell miꢀ
gration due to cytotoxicity. MDAꢀMBꢀ231 cells were allowed
to grow for 14 days in sixꢀwell plates in the presence or abꢀ
sence of the synthetic compounds at 10 ꢂM. The cell toxicity
data for all derivatives are listed in Table 1 along with antiꢀ
migration data for comparison. Figure 2 shows five examples
of the proliferation and colony formation images of antiꢀ
migration derivativeꢀtreated colonies compared to that of
DMSO treated control cells. The five compounds, 2b, 5j, 3n,
4e, and 5k all inhibited cell migration by over 50% (55% to
86%), yet no apparent cell toxicity was observed when cells
were treated with the derivatives at the same dose of 10 ꢁM
for two weeks, with the exception of 5j, which significantly
inhibited colony formation of the breast cancer cells by 75%
(see also Table 1). A few other antiꢀmigration derivatives did
exhibit moderate level of inhibition of the breast cancer cell
proliferation. For example, derivative 3g blocked both cell
tives on cancer cell migration, we performed transwell migraꢀ
tion assay on each compound using an invasive and metastatic
breast cancer cell line, MDAꢀMBꢀ231. When cells were seedꢀ
ed at a density of 2.5 × 104 in media free of serum in the upper
chamber but containing 5% FBS in the lower chamber, their
ability to migrate in the presence and absence of 10 ꢁM derivꢀ
atives were measured by counting the total number of cells in
the lower chamber after 24 hrs. As shown in Table 1, of the
37 synthetic derivatives, most displayed moderate or potent
antiꢀmigration activity, 19 derivatives showed greater than
50% inhibition, and three most potent derivatives (3g, 5j and
5k) blocked cell migration by over 80%. These results demonꢀ
strate that the synthetic derivatives are effective migration
inhibitors.
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As showed in Table 1, transformed from 2a, 2b and 2c by
condensing with various carboxylic acid or acyl chloride, the
amides 3 exhibited widely variable activities from the most
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migration (81.4%) and colony formation (42.7%). For these icity, also appears to be the most potent compound in blocking
1
2
derivatives cytotoxicity may have partially contributed to their
overall antiꢀmigration effect.
cell invasion.
3
4
DMSO
2b
Migration (HeLa)
Proliferation (HeLa)
5j
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
5
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3n
4e
5k
Figure 3. Effect of selected thiazole derivatives on the migraꢀ
tion and proliferation of HeLa cells.
Figure 2. Clonogenic assay demonstrates no cytotoxicity of
thiazole derivatives that potently inhibit migration of MDAꢀ
MBꢀ231 cells in four out of five selected compounds. Images
of colony formation are shown for cells treated with 1) DMSO,
2) 2b, 3) 5j, 4) 3n, 5) 4e, and 6) 5k.
Migration (A549)
100%
Based on the potent effects of synthetic thiazole derivatives
in blocking migration of MDAꢀMBꢀ231 cells, we selected 10
derivatives with high antiꢀmigration activity but low or negliꢀ
gible cytotoxicity to test their antiꢀmigration activity in another
metastatic cell line, HeLa. For comparison of possible cancer
cell specific mode of action we also included 5j, a potent antiꢀ
migration derivative that also inhibited the proliferation of the
triple negative breast cancer cells. Results are summarized in
Figure 3. The derivatives exhibited excellent antiꢀmigration
activity in HeLa cells, as evidenced by the dramatically reꢀ
duced transwell migration (60ꢀ86% inhibition) when treated
with 10 ꢂM derivatives. While these derivatives demonstrated
similar antiꢀmigration efficacies in MDAꢀMBꢀ231 and HeLa
cells, some differences were noted. For example, the derivative
3n showed 30% inhibition of colony formation in MDAꢀMBꢀ
231 cells but had no apparent cytotoxicity in HeLa cells. On
the other hand, the derivative 5i was not toxic to 231 cells, but
it suppressed the clonogenic capability of HeLa cells by 45%
(Figure 3). Interestingly, the derivative 5j was a strong inhibiꢀ
tor of cell proliferation for both HeLa and MDAꢀMBꢀ231
cells. The derivative that emerged as the most potent antiꢀ
migration agent with no apparent cytotoxicity in both metastatꢀ
ic breast cancer and cervical cancer cell lines was 5k, achievꢀ
ing over 85% inhibition of transwell migration in both cell
lines at the dose of 10 ꢁM. Thus 5k may be further evaluated
for its potential as an antiꢀmigration and antiꢀmetastatic agent.
Additional migration assay of a non small cell lung cancer cell
line, A549 also demonstrated that in the presence of 10 ꢂM 5k,
the metastatic lung cancer cells lost nearly 80% of migratory
capacity (Figure 4).
80%
60%
40%
20%
0%
DMSO
Compound 5k
Figure 4. Derivative 5k strongly inhibits migration of A549, a
metastatic non small cell lung cancer cell line.
Invasion of MDA-MB-231 Cells
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Compounds
Figure 5. Effect of selected thiazole derivatives on the invaꢀ
sion of MDAꢀMBꢀ231 breast cancer cells.
To determine if the synthetic thiazole derivatives block inꢀ
vasion of metastatic cancer cells we performed matrigel invaꢀ
sion assays of MDAꢀMBꢀ231 cells treated with 10 selected
derivatives. As shown in Figure 5, all 10 derivatives exhibited
marked inhibition of matrigel invasion of the breast cancer
cells, with percent invasion reduced to approximately 40ꢀ60 %
of the control at the dose of 10 ꢂM. The derivative 5k, the
most active antiꢀmigration agent without any apparent cytotoxꢀ
An essential component of migration is protrusion of the cell
membrane, which is driven by actin polymerization. Previous
studies have shown that a natural compound known as
migrastatin blocks actin bundling by binding to the actin reguꢀ
latory protein fascin, which is linked to migration in cell culꢀ
ture systems, and metastasis in vivo.
31ꢀ33
While the study by
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fascin
overlay
f-actin
Chen et al showed that migrastatin blocked the actin bundling
activity of fascin using purified proteins in vitro, the effects on
1
2
3
4
5
6
7
8
actin structures in cells were not tested.31 Thus, we tested the
hypothesis that compound 5k interferes with fꢀactin in memꢀ
brane protrusions associated with cell motility. MDAꢀMBꢀ231
cells were serum starved ꢀ/+ 10ꢂM 5k, then stimulated with
serum for 2 hours to induce actinꢀrich membrane protrusions,
which were analyzed by fluorescent microscopy. Figure 6
shows that control cells (DMSOꢀtreated) had robust actinꢀ rich
membrane protrusions, which were significantly reduced in
cells treated with 5k (55% reduction in fꢀactin intensity;
p<0.01). To further probe for a possible role of fascin in the
reduction of actinꢀrich membrane protrusions, we determined
the localization of fascin by immunofluorescence microscopy.
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Figure 7. Immunofluorescence microscopic images of localiꢀ
zation of fascin (green) and fꢀactin (magenta) in MDAꢀMBꢀ
231 cells treated with DMSO (vehicle) or synthetic derivative
5k. Colocalization of fꢀactin and fascin appears as white pixꢀ
els.
control
compound 5k
that strongly suppressed cell motility in metastatic cancer cells.
More importantly, these compounds exhibited no apparent
cytotoxicity as they do not inhibit the ability of metastatic canꢀ
cer cells to form colonies when treated with the migration inꢀ
hibitors. Thus, our study provides a novel type of small moleꢀ
cule therapeutic agents that aim to block cancer cell migration
and invasion without exerting cell toxicity. Furthermore, we
provide evidence that the antiꢀmigration activity of these comꢀ
pounds may be a result of impaired formation of actin strucꢀ
tures in cells, which are known to be necessary for tumor cell
migration and metastasis. Further studies to determine the exꢀ
act antiꢀmigration mechanism are underway.
A
B
600000
control
compound 5k
500000
400000
300000
200000
100000
0
* p<0.01
ASSOCIATED CONTENT
Supporting Information. The Xꢀray single crystal data and exꢀ
perimental procedures for synthesis and characterization of thiaꢀ
zole derivatives, cell culture, in vitro migration assays, clonogenic
assays, invasion assays and fluorescence microscopy are included.
This material is available free of charge via the Internet at
http://pubs.acs.org.
C
AUTHOR INFORMATION
Corresponding Author
Figure 6. Derivative 5k strongly suppresses actinꢀrich memꢀ
brane protrusions in MDAꢀMBꢀ231 cells. Fꢀactin staining in
(A) Control cells (DMSOꢀtreated); or (B) Cells treated with
5k; and (C) Quantitation of fꢀactin intensity in vehicle and 5kꢀ
treated cells.
Tel: 504-520-7824. E-mail: szheng@xula.edu (S.Z.).
Tel: 504-520-5076. E-mail: gwang@xula.edu (G.W.).
Figure 7 shows that in control cells, a pool of fascin is localꢀ
ized within the zone of fꢀactin in the protrusions. This pool of
fascin was notably missing from the actinꢀrich membrane reꢀ
gions in the cells treated with 5k (indicated by arrowheads.)
Thus, our results demonstrate that compound 5k significantly
blocks fꢀactin and is correlated with the absence of fascin in
the membrane protrusions, suggesting that its mechanism of
action is to perturb the actin dynamics required for tumor cell
migration.
Funding
This work was supported by NIH RCMI program through Grant
5G12RR026260ꢀ03; the Louisiana Cancer Research Consortium
(LCRC); Department of Agriculture Grant 58ꢀ6435ꢀ7ꢀ019; and
Office of Naval Research Grant N00014ꢀ99ꢀ1ꢀ0763.
Notes
The authors declare no competing financial interest.
We have designed and synthesized 37 thiazole derivatives as
novel antiꢀmigration and antiꢀinvasion agents. Structural modiꢀ
fication of the substitution groups on the central thiazole ring
led to the identification of several potent migration inhibitors
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