ONCOLOGY REPORTS 27: 455-460, 2012
Abstract. Histone acetylation is one of the key chromatin
modifications that control gene transcription during develop-
ment and tumorigenesis. Recently, it was reported that the
histone deacetylase inhibitor, Trichostatin A (TSA), induces
growth arrest and apoptosis in tumors. However, the molecular
mechanisms responsible for its antitumor effects are not clear.
The purpose of this study was to investigate the effect of TSA
on human oral squamous carcinoma cells and to determine the
mechanisms underlying the antitumor activity of TSA. MTT
assays showed that TSA inhibited cell proliferation in YD-10B
cells. TSA also effectively arrested cell cycle progression at the
G2/M phase through the up-regulation of p21waf expression,
down-regulation of Cyclin B1 and reduction of the inhibitory
phophorylation of Cdc2. In addition, mitochondrial membrane
destruction was induced by a 48 h TSA treatment. TSA also
induced cytochrome c release and proteolytic activation of
caspase 3 and caspase 7 in YD-10B cells. Taken together, these
observations in YD-10B oral cancer cells reveal the potential
value of TSA in inhibiting oral tumor growth.
Histone deacetylases (HDACs) which induce hydrolysis of the
ε-amino acetyl moiety on specific acetylated lysine residues
within core histones, are known to repress transcription by
associating with gene promoters (1). A number of findings
suggest that the transcriptional repression of tumor-suppressor
genes by the overexpression and aberrant recruitment of
HDACs to their promoter region could be a common phenom-
enon in tumor onset and progression (2). On the contrary,
histone deacetylase inhibitors (HDIs) induce the accumulation
of acetylated histones, resulting in the relaxation of chromatin
structure and greater accessibility to the transcriptional
machinery. HDIs elicit multiple biological effects based on how
they alter the acetylation patterns of histones and non-histone
TSA, one of the most common HDIs with a hydroxamic
acidic group, is a potent inhibitor of HDACs (6). Recently, TSA
has been reported to have inhibitory effects on cell prolifera-
tion, cell migration and to induce apoptosis in various cancer
cell lines (7-12). One of the most notable effects of TSA on
transformed cells is its ability to halt cell cycle transition. The
combined increase of cyclin-dependent kinase (Cdk) inhibi-
tors, such as p21waf and the decrease of cyclins in response to
TSA activity may account for the reduced Cdk activity and
may cause cell cycle arrest. TSA-induced p21waf expression
is independent of p53 and correlates with the altered expres-
sion of proteins associated with the p21waf promoter, including
an increase in the acetylation of histones (13,14). It has been
reported that TSA induces apoptosis through the mitochondrial
pathway by elevating Bax protein levels, causing the release
of cytochrome c from mitochondria and activating the caspase
cascade. Additionally, the overexpression of either Bcl-2 or
Bcl-XL, which protect mitochondria, inhibit TSA-induced
apoptosis (12). Alternatively, TSA has been demonstrated to
trigger caspase-independent apoptosis in human gastric cancer
cells and non-small cell lung carcinoma cells (15,16).
In general, the underlying mechanisms of TSA in oral
cancer have not been fully elucidated. In this study, we
examined the effects of TSA on cell proliferation, cell cycle
progression and cell death in YD-10B cells. We found that
TSA induced the accumulation of acetylated histones in
YD-10B cells, leading to the suppression of proliferation and
the induction of apoptosis. This evidence provides a molecular
basis for the treatment of oral cancer patients with this phar-
The histone deacetylase inhibitor, Trichostatin A,
induces G2/M phase arrest and apoptosis in
YD-10B oral squamous carcinoma cells
TRINH DUC ANH1, MEE-YOUNG AHN1, SOO-A KIM2, JUNG-HOON YOON1 and SANG-GUN AHN1
1Department of Pathology, Chosun University College of Dentistry, Gwangju 501-759; 2Department of Biochemistry,
Dongguk University College of Oriental Medicine, Gyeongju 780-714, Republic of Korea
Received August 4, 2011; Accepted September 16, 2011
Correspondence to: Dr Sang-Gun Ahn or Dr Jung-Hoon Yoon,
Department of Pathology, Chosun University School of Dentistry,
375 Seosuk-Dong, Dong-gu, Gwangju 501-759, Republic of Korea
Abbreviations: HDACs, histone deacetylases; HDIs, histone
deacetylase inhibitors; TSA, Trichostatin A; Cdk2, cyclin-dependent
kinase 2; Plk1, polo-like kinase 1; PARP, poly(ADP-ribose) poly-
merase; Ac-H3, acetylation of histone H3; Bcl-2, B-cell lymphoma 2;
Bax, Bcl-2-associated X protein
Key words: histone deacetylases, Trichostatin A, cell cycle,
apoptosis, oral cancer
ANH et al: TSA EFFECTS IN AN ORAL CANCER CELL LINE
Materials and methods
Reagents and antibodies. Trichostatin A (TSA) was purchased
from Sigma Chemical Co. (St. Louis, MO). Antibodies directed
against Bax, Bcl-2, pro-caspase 3, pro-caspase 7, actin, Plk1
and Cyclin B1 were purchased from Santa Cruz Biotechnology
(Santa Cruz, CA). Antibodies directed against PARP, cleaved
caspase 3, cleaved caspase 7, cleaved caspase 9, p21waf, cyto-
chrome C, acetylated histone H3, p-Cdc2 and p-Cdc25c were
supplied by Cell Signaling Technology (Beverly, MA).
Cell culture. YD-10B oral squamous carcinoma cells were
purchased from the Korean Cell Line Bank. These cells were
cultured in RPMI-1640 medium (Gibco-BRL) with 10 % FBS
(Gibco-BRL), 100 U/ml penicillin and 100 µg/ml strepto-
mycin (Invitrogen, Carlsbad, CA) in humid air with 5% CO2
MTT assay. YD-10B cells (1x105 per well) were seeded into
12-well plates. After drug treatment, 3-(4,5-dimethylthiazol-
2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) solution
(5 mg/ml in PBS) was added and cells were incubated at
37˚C for 3 h. The culture medium was subsequently aspirated
and acid isopropanol [0.04 mol/l hydrogen chloride (HCl) in
isopropanol] was added to dissolve the dark blue crystals. The
optical density value of the dissolved solute was then measured
using a Microplate Autoreader (Bio-Tek Instruments Inc.,
Winooski, VT) at a wavelength of 570 nm.
Histone deacetylase activity and Cdc2/Cyclin B kinase
activity assays. YD-10B cells were treated with the indicated
concentrations of TSA for 48 h. Next, cells were harvested,
and whole cell protein was extracted using RIPA lysis buffer.
Protein concentrations were identified by a BCA kit. Histone
deacetylase activity was measured using the SensoLyte® 520
HDAC Activity Assay kit (AnaSpec, Inc.) and Cdc2/Cyclin B
kinase activity was assessed using CycLex Cdc2-Cyclin B
Kinase Assay kit (Biotium, Inc., Hayward, CA). Experimental
procedures were performed according to the manufacturer's
Cell cycle analysis. After TSA treatment, cells were harvested
by trypsinization, washed once in ice-cold 1X PBS, centrifuged
at 300 x g and the resulting cell pellets were fixed in 75%
ethanol. Fixed cells were subsequently stained with 250 µl of
propidium iodide (PI) solution (20 µg/ml PI, 200 µg/ml DNase-
free RNase A in 1X PBS) for 30 min at 37˚C. DNA content
was analyzed usinga Cell LabQuanta SC Flow Cytometer
(Beckman Coulter) with an excitation wavelength of 488 nm.
Western blot analysis. YD-10B cells were treated with TSA
for 48 h, washed with PBS and harvested in lysis buffer.
Samples containing equal amounts of protein were loaded into
each lane of a SDS-polyacrylamide gel for electrophoresis and
were subsequently transferred onto a polyvinylidene difluoride
(PVDF) membrane. After blocking, membranes were incu-
bated with the indicated antibody.
DAPI staining. Cells were seeded onto glass coverslips in
24-well plates. Forty-eight hours after TSA treatment, cells
were stained with 1 µg/ml DAPI for 10 min at room tempera-
ture. Later, the coverslips containing cells were mounted onto
microscope slides using mounting solution and were analyzed
by fluorescence microscopy.
Mitochondrial membrane potential determination. YD-10B
cells were cultured on glass coverslips in 6-well plates and were
treated with different doses of TSA for 48 h. The mitochondrial
membrane potential was detected using JC-1 mitochondrial
membrane potential detection kit from Biotium, Inc. Pictures
were captured using an Olympus IX71 fluorescent microscope.
Flow cytometry assay for apoptosis. YD-10B cells (1x104/ml)
were treated with various concentration of TSA for 48 h.
Next, cells were harvested with trypsin, stained with both
Annexin V-FITC and PI according to the manufacturer's
protocol (Invitrogen) and were analyzed using the Cell Lab
Quanta SC flow cytometer (Beckman Coulter).
Statistical analysis. The data obtained from the different
groups are expressed as mean ± SD. All statistical calculations
were carried out using Microsoft Excel. Values of P<0.05 were
considered to indicate significant differences.
Effect of TSA on YD-10B cell proliferation. To explore the
effects of TSA on cell proliferation in oral squamous carci-
noma cells, YD-10B cells were treated with TSA at various
concentrations (0.05-5 µM) for 24 and 48 h and proliferation
was measured using MTT assay. Treatment with TSA inhibited
the proliferation of YD-10B cells in a dose- and time-depen-
dent manner (Fig. 1A). Changes in cell morphology showed
numerous dead and floating cells following treatment with
either 1 or 2 µM of TSA for 48 h (Fig. 1B). These results indi-
cate that TSA induces anti-growth and/or cell-killing effects
in YD-10B cells.
Effect of TSA on HDAC activity in YD-10B cells. We next
examined whether HDAC activity is important for the anti-
proliferative effect of TSA in YD-10B cells. Following
incubation with the indicated concentrations of TSA for 48 h,
HDAC activity assays were performed on whole cell extracts.
TSA strongly inhibited HDAC activity in a dose-dependent
manner (Fig. 2A). Furthermore, Western blot analysis revealed
that TSA dramatically enhanced the acetylation of histone H3
in YD-10B cells after treatment with 1 or 2 µM TSA (Fig. 2B).
These results suggest that modifying the epigenetic status
of chromatin is involved in mediating the effects of TSA in
Cell cycle arrest effect of TSA in YD-10B cells. To determine
the effects of TSA on the cell cycle, YD-10B cells were treated
with TSA for 48 h and the cell cycle phase distribution was
analyzed by flow cytometry. As shown in Fig. 3A and B,
TSA treatment resulted in an increased number of cells in the
G2/M phase (13.13-40.44%) with a concomitant reduction of
cells in the G1 phase (79.39-27.94%). These data indicate that
TSA effectively induces cell cycle arrest at the G2/M phase in
ONCOLOGY REPORTS 27: 455-460, 2012
Figure 1. Effect of TSA on cell proliferation. YD-10B cells were treated with TSA for 24 or 48 h. (A) Cell proliferation was analyzed by the MTT assay (◆, 24 h;
◼, 48 h). (B) Morphological changes in YD-10B cells after TSA treatment for 48 h (0, 0.2, 1.0 or 2.0 µM). Pictures were taken with a phase contrast microscope
at x100 magnification.
Figure 2. The inhibitory effect of TSA on HDAC activity. YD-10B cells were treated with TSA for 48 h. (A) The whole-cell extract was subsequently used for
an HDAC activity assay or (B) Western blot analysis to detect the acetylation of histone H3 (Ac-H3).
Figure 3. Effect of TSA on cell cycle progression. YD-10B cells were treated with the indicated doses of TSA for 48 h. After fixation with 70% ethanol, cells were
stained with PI and analyzed by FACS. (A) Changes in cell phase distribution between various concentrations of TSA. (B) Proportion of cells in G2/M phase. Error
bars indicate ± SD values. *P<0.001 compared to control. (C) YD-10B cells were treated with TSA for 48 h, after which whole cell protein was extracted, and the
expression of G2/M-related proteins was analyzed by Western blotting. (D) Whole-cell protein was used to examine the activity of the Cdc2/Cyclin B complex.
**P<0.01 compared to control.
ANH et al: TSA EFFECTS IN AN ORAL CANCER CELL LINE
We next examined the expression cell cycle proteins that
regulate G2/M in TSA-treated YD-10B cells. Western blot
analysis showed that TSA enhanced p21waf expression and
inhibited Cyclin B1 and Cdc2 (Fig. 3C). The expression level of
p21waf was gradually elevated in cells treated with 2 µM TSA,
whereas Cyclin B1 expression was inhibited at a concentration
of only 0.2 µM TSA. In addition, TSA displays an inhibitory
effect on the phosphorylation of Cdc25c and Cdc2 at doses of
1 or 2 µM. Plk1, which is one of the most important G2/M cell
cycle regulatory proteins, was also inhibited by low-dose TSA
treatment (Fig. 3C).
To examine whether TSA affects Cdc2/Cyclin B activity,
we performed Cdc2/Cyclin B kinase activity assays. The
activity of the Cdc2/Cyclin B complex was clearly repressed
by TSA in a dose-dependent manner (Fig. 3D). Taken together,
TSA appears to arrest cell cycle progression at the G2/M phase
through regulation of Plk1-modulated Cdc2/Cyclin B complex
Characterization of TSA-induced cell death. To explore the
involvement of mitochondria in the cell death inducing the
effect of TSA in YD-10B cells, we examined the mitochon-
drial membrane potential. Cells were incubated with TSA
for 48 h prior to mitochondria staining and fluorescence
microscopy was used to observe changes in mitochondrial
membrane potential. Control cells, which have high mitochon-
drial transmembrane potential, displayed red fluorescence in
mitochondria, whereas apoptotic or unhealthy cells showed
only green fluorescence. Upon treatment with 1 or 2 µM of
TSA, the mitochondrial membrane was damaged, resulting in
alterations to membrane permeability (Fig. 4A). Furthermore,
DAPI staining of the nucleus revealed condensation of nuclei,
which is indicative of cell death after 48 h treatment with 1 or
2 µM TSA (Fig. 4B).
Next, flow cytometry was used to analyze apoptosis in
response to TSA treatment. YD-10B cells were incubated with
TSA for 48 h before dual-staining with Annexin V and PI.
TSA induced early and late stage apoptosis, especially at a
concentration of 2 µM, which resulted in an increase of over
20% compared to control (Fig. 5A). These finding suggest that
TSA induces apoptosis in YD-10B cells.
We also examined the expression of apoptosis related
proteins in TSA-treated cells. Because cytochrome c and
Bcl-2 family members play an important role in mitochondria-
dependent apoptosis, we used Western blot analysis to assay the
expression of these proteins. Both the expression of Bax and
the amount of cytochrome c detected in the cytosol increased
in a dose-dependent manner in response to TSA treatment.
Cytochrome c levels began to increase at a low concentra-
tion of TSA (0.2 µM). Immunoblot analysis clearly showed a
concentration-dependent activation of caspase 3 and caspase 7,
as indicated by the disappearance of a band at 35-kDa, which
represents pro-caspase 7. The activation of caspase 7 led to the
cleavage of a 119-kDa poly(ADP-ribose) polymerase (PARP)
protein to produce an 89-kDa fragment, whereas untreated
cells did not show any PARP cleavage (Fig. 5B). These results
suggest that TSA induces mitochondria-dependent apoptosis
in YD-10B cells.
Oral cancer is one of the fastest growing malignancies, and it
is particularly dangerous because of a high risk of producing
secondary tumors. There are several types of oral cancers,
of which 90% are classified as squamous cell carcinomas
(17). Despite enormous efforts for improvement, survival
rates have remained unchanged over 20 years due to a lack
of markers for early prognosis and the failure of advanced
tumors to respond to chemotherapy (18). In this study, we
evaluated the effect of TSA as a therapeutic for oral squamous
Recently, growing evidence suggests that the inhibition of
HDACs is a promising new strategy in cancer therapy. Various
HDAC inhibitors have been shown to exhibit this potent anti-
tumor activity both in vitro and in vivo. Depending on the cell
type, HDAC inhibitors have been demonstrated to arrest cells
at G0/G1 or G2/M. One such inhibitor, TSA, induced G2/M
cell cycle arrest and apoptosis in HeLa and Tca8113 cell lines
(8,13). Consistent with these reports, our present study shows
Figure 4. Effect of TSA on the mitochondrial membrane potential and cell
death. (A) YD-10B cells were treated with TSA for 48 h prior to analysis
using the JC-1 mitochondrial potential detection kit. (B) Cells were incubated
with TSA for 48 h before fixation with ethanol and DAPI staining. The lower
panel indicates the percentage of apoptotic cells. Pictures were taken by fluo-
rescence microscopy (a, b, c and d represent concentrations of 0, 0.2, 1.0 and
2.0 µM of TSA, respectively).
ONCOLOGY REPORTS 27: 455-460, 2012
that TSA induces G2/M cell cycle arrest and apoptosis in
YD-10B oral squamous carcinoma cells.
Although TSA exhibits antitumor activity, little is known
about its molecular mechanism of action. A recent report
showed that TSA enhanced the acetylation of histone H3 on the
p21waf promoter and induced its expression (8,14). In this study,
we show that TSA induces the expression of p21waf, down-regu-
lates Cyclin B and decreases the inhibitory phosphorylation of
Cdc25c. The inhibition of Cyclin B expression and dephos-
phorylation of Cdc2 was observed with a low dose (0.2 µM) of
TSA, but p21waf expression was altered only upon incubation
with a high dose of TSA (2 µM). Thus, it appears that p21waf is
not the unique regulator determining Cdc2/Cyclin B complex
activity in YD-10B cells. Plk1 has emerged as a potential target
of HDACs, due to its wide-ranging effects on G2/M cell cycle
regulation. As a kinase, Plk1 alters the phosphorylation status
of numerous substrates, including Cyclin B and Cdc25c. Plk1
is responsible for the nuclear translocation of Cyclin B during
the onset of the transition from the G2 phase to mitosis (19,20).
Moreover, Plk1 plays an important role in the nuclear import
of Cdc25c by way of Ser198 phosphorylation. In turn, Cdc25c
directly activates Cdc2, facilitating the movement of cells
through the G2 checkpoint. In addition to regulating Cyclin B
and Cdc25c, Plk1 also promotes the degradation of Wee1
and Myt1 proteins, which are suppressors of Cdc2, thereby
contributing to the activation of the Cdc2/Cyclin B complex
(21,22). In this study, Plk1 expression was inhibited by TSA,
even at low doses (0.2 µM). Therefore, the sensitive response
of Plk1 to TSA may account for the decrease we observed in
the activation of the phosphorylation of Cdc25C and of Cdc2
in response to a low dose of TSA (0.2 µM).
HDACs inhibitors promote an open state of chromatin
via neutralizing charges in the histone backbone with acetyl
groups, which leads to the transcriptional activation of various
genes that induce the repression of tumor cell growth and
make tumor cells more susceptible to DNA damaging agents
(anti-cancer drugs, oxidants, UV) (5,23). In the present study,
we found a marked increase in the acetylation of histone H3
after TSA treatment, suggesting that TSA strongly induces
DNA relaxation. Moreover, MTT assays revealed that TSA
significantly inhibits the proliferation of YD-10B cells in a
dose-dependent manner. Cell morphology and DAPI staining
of the nucleus revealed typical characteristics of apoptosis,
such as cell shrinkage and condensed DNA, especially at
higher doses of TSA.
HDAC inhibitors have been demonstrated to induce
apoptosis through both mitochodrial-dependent and death
ligand-dependent pathways. Furthermore, the altered expres-
sion of several pro-and anti-apoptotic intracellular genes by
HDAC inhibitors has been reported (24-26). However, the
expression pattern of pro-and anti-apoptotic proteins seems
to be cell-type-dependent. For example, TSA decreased the
expression of Bcl-2, while expression of the pro-apoptotic
factor, Bax, was increased in hepatoma cells (27). In contrast,
the expression of Bcl-2 and Bax was unaffected by TSA treat-
ment in glioma cells (28). Therefore, an understanding of the
exact mechanisms by which TSA regulates the genes involved
in apoptosis is needed in oral squamous cell carcinomas.
We clearly demonstrate that TSA induces apoptosis in
YD-10B cells by regulating a series of apoptosis-associated
genes, including caspase 3 and caspase 7. We also observed
a concentration-dependent increase of Bax levels and the
loss of the mitochondrial membrane potential in TSA-treated
YD-10B cells. However, TSA did not affect the expression of
Bcl-2. In addition, Western blot analysis confirmed an increase
in the level of cytochrome c present in the cytosol. These data
suggest that TSA induces cell death through the activation of
mitochondria-dependent pathways in YD-10B cells. Although
we did not examine caspase 9 activation, we observed cleavage
of caspase 7 and caspase 3, which correlated with the decrease
of pro-caspase 7 and pro-caspase 3. Additionally, the similar
cleaving pattern observed between the caspases and PARP in
Figure 5. Effects of TSA on apoptosis. (A) YD-10B cells were treated with the indicated doses of TSA for 48 h. Following harvest, cells were stained with
both Annexin V and PI and were analyzed by FACS. (B) The whole-cell or cytosolic (for cytochrome c) protein was extracted and the expression of apoptotic
proteins was monitored by Western blot analysis.
ANH et al: TSA EFFECTS IN AN ORAL CANCER CELL LINE Download full-text
response to TSA treatment suggests that active caspase 7 and
caspase 3 are responsible for the proteolytic cleavage of PARP.
However, it remains unclear which pathway(s) drive the apop-
totic response to TSA. Our data show that cytochrome c levels
were greatly increased, but Bax expression increased only
slightly, indicating that the mitochondrial pathway may not be
solely responsible for TSA-mediated apoptosis. In fact, TSA
has also been reported to stimulate the modulation of death
receptors, leading to Fas- or TNF-mediated apoptosis (12,29).
Furthermore, TSA was found to induce caspase-independent
cell death via the activation of the apoptosis-inducing factor
(AIF) pathway in human gastric cancer cells and non-small
cell lung carcinoma cells (15,16). Clearly, further studies are
required to verify the mechanisms driving apoptotic cell death
in YD-10B cells in response to TSA treatment.
Our study provides evidence that the HDAC inhibitor TSA,
potently inhibits the proliferation of YD-10B cells in vitro,
causing both apoptosis and cell cycle arrest. Thus, TSA is a
novel and promising strategy for inhibiting tumor growth in
patients with oral cancer.
This research was supported by Basic Science Research Program
(20110004555) through the National Research Foundation of
Korea (NRF) and the National Research Foundation of Korea
(NRF) funded by the Ministry of Education, Science and
Technology (No. R13-2008-010-00000-0).
1. Berger SL: The complex language of chromatin regulation
during transcription. Nature 447: 407-412, 2007.
2. Ropero S and Esteller M: The role of histone deacetylases
(HDACs) in human cancer. Mol Oncol 1: 19-25, 2007.
3. Shankar S and Srivastava RK: Histone deacetylase inhibitors:
mechanisms and clinical significance in cancer: HDAC inhibitor-
induced apoptosis. Adv Exp Med Biol 615: 261-298, 2008.
4. Moradei O, Vaisburg A and Martell RE: Histone deacetylase
inhibitors in cancer therapy: new compounds and clinical update
of benzamide-type agents. Curr Top Med Chem 8: 841-858, 2008.
5. Bolden JE, Peart MJ and Johnstone RW: Anticancer activities of
histone deacetylase inhibitors. Nat Rev Drug Discov 5: 769-784,
6. Marks PA and Xu WS: Histone deacetylase inhibitors: potential
in cancer therapy. J Cell Biochem 107: 600-608, 2009.
7. Yoshikawa M, Hishikawa K, Idei M and Fujita T: Trichostatin a
prevents TGF-beta1-induced apoptosis by inhibiting ERK acti-
vation in human renal tubular epithelial cells. Eur J Pharmacol
642: 28-36, 2010.
8. Yao J, Duan L, Fan M and Wu X: NF-kB signaling pathway is
involved in growth inhibition, G2/M arrest and apoptosis induced
by Trichostatin A in human tongue carcinoma cells. Pharmacol
Res 54: 406-413, 2006.
9. Pan L, Lu J, Wang X, Han L, Zhang Y, Han S and Huang B:
Histone deacetylase inhibitor trichostatin a potentiates doxo-
rubicin-induced apoptosis by up-regulating PTEN expression.
Cancer 109: 1676-1688, 2007.
10. Jang ER, Kim YJ, Myung SC, Kim W and Lee CS: Different
effect of protein kinase B/Akt and extracellular signal-regulated
kinase inhibition on trichostatin A-induced apoptosis in epithelial
ovarian carcinoma cell lines. Mol Cell Biochem 353: 1-11, 2011.
11. Zhou C, Qiu L, Sun Y, Healey S, Wanebo H, Kouttab N, Di W,
Yan B and Wan Y: Inhibition of EGFR/PI3K/AKT cell survival
pathway promotes TSA's effect on cell death and migration in
human ovarian cancer cells. Int J Oncol 29: 269-278, 2006.
12. Kim HR, Kim EJ, Yang SH, Jeong ET, Park C, Lee JH, Youn MJ,
So HS and Park R: Trichostatin A induces apoptosis in lung
cancer cells via simultaneous activation of the death receptor-
mediated and mitochondrial pathway. Exp Mol Med 38: 616-624,
13. Noh EJ, Lim DS, Jeong G and Lee JS: An HDAC inhibitor,
trichostatin A, induces a delay at G2/M transition, slippage of
spindle checkpoint, and cell death in a transcription-dependent
manner. Biochem Biophys Res Commun 378: 326-331, 2009.
14. Nishioka C, Ikezoe T, Yang J, Koeffler HP and Yokoyama A:
Inhibition of MEK/ERK signaling synergistically potentiates
histone deacetylase inhibitor-induced growth arrest, apoptosis
and acetylation of histone H3 on p21waf1 promoter in acute
myelogenous leukemia cell. Leukemia 22: 1449-1452, 2008.
15. Wu ZQ, Zhang R, Chao C, Zhang JF and Zhang YQ: Histone
deacetylase inhibitor trichostatin A induced caspase-independent
apoptosis in human gastric cancer cell. Chin Med J (Engl) 120:
16. Hajji N, Wallenborg K, Vlachos P, Nyman U, Hermanson O and
Joseph B: Combinatorial action of the HDAC inhibitor tricho-
statin A and etoposide induces caspase-mediated AIF-dependent
apoptotic cell death in non-small cell lung carcinoma cells.
Oncogene 27: 3134-3144, 2008.
17. Jemal A, Siegel R, Xu J and Ward E: Cancer statistics, 2010. CA
Cancer J Clin 60: 277-300, 2010.
18. Massano J, Regateiro FS, Januário G and Ferreira A: Oral
squamous cell carcinoma: review of prognostic and predictive
factors. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 102:
19. Glover DM, Hagan IM and Tavares AA: Polo-like kinases: a team
that plays throughout mitosis. Genes Dev 12: 3777-3787, 1998.
20. Donaldson MM, Tavares AA, Hagan IM, Nigg EA and
Glover DM: The mitotic roles of Polo-like kinase. J Cell Sci 114:
21. Liu XS, Song B and Liu X: The substrates of Plk1, beyond the
functions in mitosis. Protein Cell 1: 999-1010, 2010.
22. Lens SM, Voest EE and Medema RH: Shared and separate
functions of polo-like kinases and aurora kinases in cancer. Nat
Rev Cancer 10: 825-841, 2010.
23. Kim MS, Baek JH, Chakravarty D, Sidransky D and Carrier F:
Sensitization to UV-induced apoptosis by the histone deacetylase
inhibitor trichostatin A (TSA). Exp Cell Res 306: 94-102, 2005.
24. Acharya MR, Sparreboom A, Venitz J and Figg WD: Rational
development of histone deacetylase inhibitors as anticancer
agents: a review. Mol Pharmacol 68: 917-932, 2005.
25. Monneret C: Histone deacetylase inhibitors. Eur J Med Chem
40: 1-13, 2005.
26. Roh MS, Kim CW, Park BS, Kim GC, Jeong JH, Kwon HC,
Suh DJ, Cho KH, Yee SB and Yoo YH: Mechanism of histone
deacetylase inhibitor trichostatin A induced apoptosis in human
osteosarcoma cells. Apoptosis 9: 583-589, 2004.
27. Herold C, Ganslmayer M, Ocker M, Hermann M, Geerts A,
Hahn EG and Schuppan D: The histone-deacetylase inhibitor
trichostatin A blocks proliferation and triggers apoptotic
programs in hepatoma cells. J Hepatol 36: 233-240, 2002.
28. Sawa H, Murakami H, Ohshima Y, Sugino T, Nakajyo T, Kisanuki T,
Tamura Y, Satone A, Ide W, Hashimoto I and Kamada H: Histone
deacetylase inhibitors such as sodium butyrate and trichostatin A
induce apoptosis through an increase of the bcl-2-related protein
Bad. Brain Tumor Pathol 18: 109-114, 2001.
29. Shankar S, Singh TR, Fandy TE, Luetrakul T, Ross DD and
Srivastava RK: Interactive effects of histone deacetylase
inhibitors and TRAIL on apoptosis in human leukemia cells:
Involvement of both death receptor and mitochondrial pathways.
Int J Mol Med 16: 1125-1138, 2005.