Design and synthesis of a tetrahydroisoquinoline-based hydroxamate derivative (ZYJ-34v), an oral active histone deacetylase inhibitor with potent antitumor activity

Article abstract of DOI:10.1111/cbdd.12144

In our previous study, we developed a novel series of tetrahydroisoquinoline-based hydroxamic acid derivatives as histone deacetylase inhibitors (Bioorg Med Chem, 2010, 18, 1761-1772; J Med Chem, 2011, 54, 2823-2838), among which, compound ZYJ-34c (1) was identified and validated as the most potent one with marked in vitro and in vivo antitumor potency (J Med Chem, 2011, 54, 5532-5539.). Herein, further modification in 1 afforded another oral active analog ZYJ-34v (2) with simplified structure and lower molecular weight. Biological evaluation of compound 2 showed efficacious inhibition against histone deacetylase 1, 2, 3, and 6, which was confirmed by Western blot analysis results. Most importantly, compound 2 exhibited similar even more potent in vitro and in vivo antitumor activities relative to the approved histone deacetylase inhibitor SAHA. Structural modification of 1 led to another oral active HDACi 2 with simplified structure and lower molecular weight. Compared with the approved HDACi SAHA, 2 exhibited similar even superior in vitro and in vivo antitumor potency.

Full text of DOI:10.1111/cbdd.12144

Chem Biol Drug Des 2013; 82: 125–130
Research Article
Design and Synthesis of a Tetrahydroisoquinoline-
Based Hydroxamate Derivative (ZYJ-34v), An Oral
Active Histone Deacetylase Inhibitor with Potent
Antitumor Activity
Yingjie Zhang1, Chunxi Liu2, C. James Chou3,
Epigenetic covalent modifications of histone and DNA dra-
matically affect gene expression and cellular activity, and
Xuejian Wang4, Yuping Jia5 and Wenfang Xu1,*
epigenetic disorder could lead to many diseases, espe-
cially cancer. Generally, epigenetic modifications are
1Department of Medicinal Chemistry, School of
Pharmacy, Shandong University, Ji’nan, Shandong,
250012, China
reversible, catalyzed by pairs of enzymes with converse
activity. Among these enzymes, histone deacetylases
(HDACs) have attracted the most attention over the past
decades (1).
2Department of Pharmaceutics, School of Pharmacy,
Shandong University, Ji’nan, Shandong, 250012, China
3Department of Drug Discovery and Biomedical Sciences,
South Carolina College of Pharmacy, Medical University of
South Carolina, Charleston, SC, 29425, USA
4Postdoctoral Workstation, Weifang Biomedical Industry
Park Management Office, Weifang, Shandong, 261205,
China
Histone deacetylase are amidohydrolases with multiple
functions. In cell nuclear, HDACs catalyze the deacetyla-
tion of lysine residues located at the N-terminal of nucleos-
omal histones, which results in condensed chromosomal
DNA and transcriptional repression (2–4). Over the past
few years, kinds of non-histone proteins involved in cell
growth and survival pathways have been identified as
HDAC substrates, such as transcription factors, cytoskele-
tal proteins, molecular chaperones, and nuclear import
factors (5).
5Key Laboratory of Chemical Drugs, Shandong Institute
of Pharmaceutical Industry, Jinan, Shandong, 250101,
China
*Corresponding author: Wenfang Xu, wfxu@yahoo.cn
In our previous study, we developed a novel series of
tetrahydroisoquinoline-based hydroxamic acid deriva-
tives as histone deacetylase inhibitors (Bioorg Med
Chem, 2010, 18, 1761–1772; J Med Chem, 2011, 54,
2823–2838), among which, compound ZYJ-34c (1) was
identified and validated as the most potent one with
marked in vitro and in vivo antitumor potency (J Med
Chem, 2011, 54, 5532–5539.). Herein, further modifica-
tion in 1 afforded another oral active analog ZYJ-34v
(2) with simplified structure and lower molecular
weight. Biological evaluation of compound 2 showed
efficacious inhibition against histone deacetylase 1, 2,
3, and 6, which was confirmed by Western blot analy-
sis results. Most importantly, compound 2 exhibited
similar even more potent in vitro and in vivo antitumor
activities relative to the approved histone deacetylase
inhibitor SAHA.
Eighteen HDAC isoforms, grouped into four classes, are
encoded in the human genome. The enzymes of classes I
(HDACs 1–3 and 8), II (HDACs 4–7, 9 and 10), and IV
(HDAC 11) are Zn2+-dependent metallohydrolases,
whereas the class III HDACs (sirtuins 1–7) utilize NAD+ as
a cofactor. It has been revealed that Zn2+-dependent iso-
zymes, especially class I and class II HDACs, are involved
in tumorigenesis and development, and inhibition of these
isoforms could result in proliferation inhibition, cellular
differentiation, apoptosis, susceptibility to chemotherapy,
antiangiogenesis, and migration inhibition of tumor cells
(6). In this context, categories of histone deacetylase inhib-
itors (HDACI) against Zn2+-dependent HDACs have been
developed. Currently, over 20 HDACI are in clinical trials
as antitumor agents and two of them, SAHA (Figure 1)
and FK228 (Figure 1), are already on the market (7).
Key words: antitumor, histone deacetylases, inhibitor, oral
active, tetrahydroisoquinoline, valproic acid
Abbreviations: CDK, cyclin-dependent kinase; HDAC, his-
tone deacetylase; HDACIs, histone deacetylase inhibitors;
VPA, valproic acid; ZBG, zinc-binding group.
Most HDAC inhibitors, including the intracellular active
form of FK228 (Figure 1), share a common pharmaco-
phore consisting of three domains: a zinc-binding group
(ZBG) that co-ordinates to the catalytic Zn2+ at the bottom
of the active site, a cap group able to interact with the rim
of active site entrance, and a linker that occupies the
active site tunnel and tethers ZBG to cap (Figure 1).
Received 10 December 2012, revised 6 March 2013 and
accepted for publication 2 April 2013
ª 2013 John Wiley & Sons A/S. doi: 10.1111/cbdd.12144
125

Zhang et al.
of VPA in HDACs might be the same binding site of other
co-factors. Therefore, VPA could prevent HDACs from
interaction with other proteins and the subsequent forma-
tion of multiprotein complex, which are crucial for the func-
tion of HDACs (6). Moreover, VPA may possibly act as an
allosteric inhibitor of HDACs. Based on the above hypoth-
esis, we hoped that the introduction of valproyl group
could increase the affinity between 2 and HDACs.
O
H
N
SAHA
(Vorinostat)
HO
N
H
O
O
H
O
NH NH
O
O
O
S
S
O
H
NH
HN
O
O
HS
Intracellular
active form of
FK228
O
HN
NH
H
O
HN
O
HN
SH
H
FK228
(Romidepsin)
O
ꢀ
There is a possibility that the in vivo or intracellular partial
hydrolysis of 2 could release free VPA and compound 3
(Figure 3), which was identified as a moderately potent
HDACI in our previous research (8). If so, there will be
three active components (unhydrolyzed ZYJ-34v, VPA,
and compound 3) performing multiple antitumor effects.
ZBG
Linker
Cap Group
Figure 1: The structures of SAHA and FK228 and the common
pharmacophore of histone deacetylase (HDACs) inhibitor.
O
O
O
R1
N
ꢀ
H
Compared with 1, compound 2 possesses simplified
N
H
H
N
N
N
H
N
HO
O
R2
H
structure, less chiral center, and lower molecular weight,
which are beneficial to its further research and develop-
ment.
HO
O
N
O
O
O
O
ZYJ-34c (1)
ZBG
Linker
Cap group
General structure
O
Simplify
O
HO
O
N
H
N
H
Compound 2 was evaluated against HDAC1, 2, 3, 6 using
Boc-Lys (acetyl)-4-amino-7-methylcoumarin substrate and
against MDA-MB-231 cell lysate using Boc-Lys (triflouro-
acetyl)-4-amino-7-methylcoumarin substrate to profile its
HDACs inhibitory activity and selectivity. Western blot anal-
ysis and in vitro antiproliferative assays were performed to
validate its intracellular HDACs inhibitory activity. Moreover,
in vivo antitumor activity of 2 was assessed in a human
breast carcinoma (MDA-MB-231) xenograft model. SAHA
was used as reference drug in all above-mentioned
assays.
N
HO
O
O
O
Valproic Acid (VPA)
a HDACs inhibitor in clinical trials
ZYJ-34v (2)
Figure 2: General structure of tetrahydroisoquinoline-based
histone deacetylase (HDACs) inhibitor and the design idea of
target compound ZYJ-34v.
According to the HDACI pharmacophore, we previously
designed and synthesized a novel series of tetrahydroiso-
quinoline-based hydroxamate derivatives as HDACI (Fig-
ure 2) (8–10). Among these analogs, compound ZYJ-34c
(1, Figure 2) was identified and validated as the most
potent one with marked in vitro and in vivo antitumor
potency through several rounds of structural optimization
and activity screening (10). In the present study, compound
ZYJ-34v (2, Figure 2) was designed and synthesized by
replacing the R2 group of 1 with the valproyl group. There
are three reasons for us to attempt this replacement:
Methods and Materials
Chemistry
Compound 2 was synthesized following the procedures
described in Scheme 1. The starting material compound 4
could be smoothly obtained according to our previously
published methods (9). Acylation of 4 with VPA and subse-
quent treatment with NH2OK led to the target compound
2 (Scheme 1).
ꢀ
Valproic acid (VPA) is a HDACI in clinical trials. Consider-
ing its hydroxamic acid analog, valpropylhydroxamic acid
exhibited lower class I HDACs inhibitory activity compared
with VPA (11); we hypothesized that VPA inhibited HDACs
by its valproyl group binding with HDACs rather than by its
carboxylic acid group chelating with Zn2+. The binding site
In vitro HDACs inhibition fluorescence assay
The HDACs inhibition fluorescence assays were con-
ducted by the similar method as previously described (9).
O
O
O
O
HO
N
H
H
N
N
N
O
hydrolysis
H
H
HO
O
N
NH
HO
O
O
O
O
ZYJ-34v (2)
3 (moderately potent HDACI )
VPA (a clinical HDACI)
Figure 3: Two possible hydrolytic metabolites of ZYJ-34v.
126
Chem Biol Drug Des 2013; 82: 125–130

Design and Synthesis of a Tetrahydroisoquinoline-Based HDACI
Boc-Lys (acetyl)-4-amino-7-methylcoumarin substrate was
oral gavage for 22 consecutive days, and the blank control
group received an equal volume of PBS solution contain-
ing DMSO. During treatment, subcutaneous tumor volume
and body weight were monitored regularly. After treatment,
mice were killed and dissected to weigh the tumor tissues,
livers, and spleens. All the obtained data were used to
evaluate the antitumor potency and toxicity of compounds.
Data were analyzed by Student’s two-tailed t-test. A P
level <0.05 was considered statistically significant.
used in inhibition assays against class I (HDAC1, HDAC2,
HDAC3) and class IIb (HDAC6), while Boc-Lys (triflouro-
acetyl)-4-amino-7-methylcoumarin substrate for class IIa
(MDA-MB-231 cell lysate). In brief, 10 lL of enzyme solu-
tion was mixed with various concentrations of tested com-
pound (50 lL). Five minutes later, 40 lL of fluorogenic
substrate was added, and the mixture was incubated at
37 °C for 30 min and then stopped by addition of 100 lL
of developer containing trypsin and TSA. After incubation
at 37 °C for 20 min, fluorescence intensity was measured
using a microplate reader at excitation and emission wave-
lengths of 390 and 460 nm, respectively. The inhibition
ratios were calculated from the fluorescence intensity
readings of tested wells relative to those of control wells,
and the IC50 values were calculated using a regression
analysis of the concentration/inhibition data.
Results and Discussions
Chemistry
All reactions were monitored by TLC with 0.25-mm silica
gel plates (60GF-254). UV light, iodine stain, and ferric
chloride were used to visualize the spots. Silica gel or C18
silica gel was used for column chromatography purifica-
tion. All commercially available starting materials, reagents,
and solvents were used without further purification unless
otherwise stated. Melting points were determined uncor-
rected on an electrothermal melting point apparatus. 1H
NMR spectra were recorded on a Bruker DRX spectrome-
ter at 600 MHz, d in parts per million and J in hertz, using
TMS as an internal standard. High-resolution mass spectra
were conducted by Shandong Analysis and Test Center in
Ji’nan, China. ESI-MS spectra were recorded on an API
4000 spectrometer. Compound 2 are >95% pure by
HPLC analysis, performed on a Agilent 1100 HPLC instru-
ment using a Phenomenex Synergi 4l Polar-RP 80A col-
umn (250 mm 9 4.6 mm), eluted with 50% acetonitrile/
50% water (containing 0.1% formic acid) over 30 min, with
detection at 254 nm and a flow rate of 1.0 mL/min.
In vitro antiproliferative assay
In vitro antiproliferative assay was determined by the
MTT (3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetra-
zolium bromide) method as previously described (9).
Briefly, all cell lines were maintained in RPMI1640 medium
containing 10% FBS at 37 °C in 5% CO2 humidified incu-
bator. Cells were passaged the day before dosing into a
96-well cell plate, allowed to grow for a minimum of 4 h
prior to addition of compounds. After compounds addition,
the plates were incubated for an additional 48 h, and then
0.5% MTT solution was added. After further incubation for
4 h, formazan formed from MTT was extracted by DMSO
for 15 min. Absorbance was then determined using an
ELISA reader at 570 nm and the IC50 values were calcu-
lated according to the inhibition ratios.
(S)-Methyl 2-((3-((4-methoxyphenyl)carbamoyl)-1,2,3,4-tet-
rahydroisoquinolin-7-yl)oxy)acetate (4) was synthesized
according to the methods in our previous study (9).
Western blot analysis
For Western blot analysis of acetylated tubulin, acetylated
histone H3, H4, and p21, total protein extracts were sepa-
rated on a polyacrylamide gel, transferred onto polyvinyli-
dene difluoride membranes and blotted as previously
described (12). Protein immunoblots were shown for acet-
ylated tubulin (Sigma, Shanghai, China), acetylated histone
H3 (Sigma), acetylated histone H4 (Sigma), and p21 (Cell
Signaling, Shanghai, China) using b-Actin (Sigma) as a
loading control.
(S)-7-(2-(hydroxyamino)-2-oxoethoxy)-N-(4-methoxyphe-
nyl)-2-(2-propylpentanoyl)-1,2,3,4-tetrahydroisoquinoline-3-
carboxamide (2). At room temperature, to a solution of VPA
(5) (1.32 g, 9.2 mmol) in anhydrous THF (40 mL), was
added Et3N (1.02 g, 10 mmol) followed by 2-(1H-benzo-
triazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate
(TBTU, 3.24 g, 10 mmol). After 15 min, the amine com-
pound 4 (3.33 g, 9.0 mmol) was added. Stirring was contin-
ued until compound 4 disappeared by TLC, then THF was
evaporated with the residue being taken up in EtOAc
(50 mL). The EtOAc solution was washed with saturated
Na2CO3 (3 9 10 mL), 1 N HCl (3 9 10 mL) and brine
(3 9 10 mL), dried over MgSO4, and evaporated under vac-
uum. The obtained crude product was treated with a solu-
tion of NH2OK in anhydrous methanol for 1 h, and then the
solvent was evaporated under vacuum. The residue was
acidified with 2 N HCl until pH 5–6 and then extracted with
EtOAc (3 9 30 mL). The organic layers were combined,
washed with brine (3 9 20 mL), dried over MgSO4, and
evaporated with the residue being purified by C18 reversed-
In vivo MDA-MB-231 xenograft models
In vivo MDA-MB-231 xenograft model was established as
previously described (9). In brief, conventionally cultured
MDA-MB-231 cells were inoculated subcutaneously in the
right flanks of female athymic nude mice (BALB/c-nu, 5–
6 weeks old, Slac Laboratory Animal, Shanghai, China).
About 10 days after injection, tumors were palpable (about
100 mm3) and mice were randomized into treatment and
control groups (seven mice per group). The treatment
groups received 90 mg/kg of compound 2 or SAHA by
Chem Biol Drug Des 2013; 82: 125–130
127

Zhang et al.
phase column chromatography (H2O/MeOH 3:7) to give
desired compound 2 (1.75 g, 39% yield) as a white powder.
1
Mp: 96–98 °C. H-NMR (DMSO-d6, 600 MHz) d 0.67–0.89
(m, 6H, CH3CH2CH2CHCH2CH2CH3), 1.06–1.55 (m, 8H,
CH3CH2CH2CHCH2CH2CH3),
2.96–3.17
(m,
3H,
CH2CHCH2 and PhCH2CH), 3.70 (s, 3H, OCH3), 4.45 (s,
2H, OCH2CO), 4.49–4.94 (m, 3H, NCHCO and PhCH2N),
6.74–6.92 (m, 4H, benzene protons), 7.11–7.15 (m, 1H,
benzene proton), 7.36–7.42 (m, 2H, benzene protons), 8.96
(s, 1H, NHOH), 9.88 (s, 1H, PhNH), 10.82 (s, 1H, NHOH).
HRMS (AP-ESI) m/z calculated for C27H36N3O6 [M + H]+
498.2604, found 498.2611. Retention time: 6.3 min.
Figure 4: Western blot analysis of acetylated tubulin, acetylated
histone H3, acetylated histone H4 and p21 in MDA-MB-231 cell
lines after 24 h treatment with compounds at 1 lM. b-Actin was
used as a loading control.
HDACs inhibition assay
To compare their HDACs inhibitory activity and isoform
selectivity, compound 2 and SAHA were tested against
HDAC1, HDAC2, HDAC3, and HDAC6 using acetylated
substrate. Besides, the class IIa inhibitory activity was eval-
uated against MDA-MB-231 cell lysate using class IIa-spe-
cific triflouroacetylated substrate (13). Results listed in
Table 1 showed that compared to SAHA compound 2
exhibited superior inhibitory capacities against HDAC1 and
HDAC2, while inferior inhibitory capacities against HDAC3
and HDAC6. Neither compound 2 nor SAHA exhibited
obvious inhibition against class IIa HDACs up to 10 lM,
which was consistent with literature information that SAHA
was not active against class IIa HDACs (14). Overall, com-
pound 2 was equipotent to SAHA.
Table 2: Antiproliferative activity of compound 2 with SAHA as
positive control
IC50 (lM)a
Compound MDA-MB-231 HCT116 PC-3 HepG2 MCF-7
2
1.41
1.52
0.63
0.60
2.62
3.97
4.23
6.29
4.76
3.44
SAHA
aValues are the mean of three experiments. The standard deriva-
tions are <20% of the mean.
In vitro antiproliferative activity assay
Western blot analysis
The potent HDACs inhibitory activities of compound 2 pro-
moted us to evaluate its in vitro antiproliferative activity
against several tumor cell lines (Table 2). Overall, the anti-
proliferative activity of compound 2 was similar even supe-
rior to that of SAHA, which correlated well with
aforementioned biological test results.
We also confirmed that compound 2 was cell permeable
and able to inhibit intracellular even nuclear HDACs by
monitoring the acetylation levels of tubulin, histones H3
and H4 in MDA-MB-231 cell line. Acetylated tubulin is a
known target of HDAC6, and histones are the common
targets of HDAC1 and HDAC2. Moreover, the effect on
the expression level of the cyclin-dependent kinase inhibi-
tor p21 was also investigated. Silencing of the tumor sup-
pressor gene p21 through hypoacetylation is a hallmark of
many cancers, and HDACs inhibition in the nucleus could
induce apoptosis via re-establishing expression of p21
(15). As indicated in Figure 4, both compound 2 and
SAHA effectively inhibited deacetylation of tubulin, histone
H3 and H4, and significantly induced increase in the pro-
tein level of p21 at 1 lM after 24 h of treatment.
In vivo antitumor activity assay
Encouraged by its promising in vitro activity, the in vivo
antitumor potency of compound 2 was evaluated in a sub-
cutaneous MDA-MB-231 xenograft model. Tumor growth
inhibition (TGI) and relative increment ratio (T/C) were used
as the evaluation indicators to reveal the antitumor effects
in tumor weight and tumor volume, respectively.
Table 1: Histone
(HDACs) inhibitory activity and iso-
form selectivity of compound
and SAHAa
deacetylase
Class I
Class IIb
HDAC6
Class IIa
Cell lysate
2
Compound
HDAC1
HDAC2
HDAC3
2
37.6 ꢁ 12.1
75.6 ꢁ 11.1
174.8 ꢁ 6.2
256.4 ꢁ 2.1
87.7 ꢁ 11.7
28.4 ꢁ 11.2
675 ꢁ 125
118 ꢁ 11.9
NAb
NAb
SAHA
aAssays were performed in replicate (n ꢂ 2); IC50 (nM) values are shown as mean ꢁ SD.
bNA: not active at 10 lM.
128
Chem Biol Drug Des 2013; 82: 125–130

Design and Synthesis of a Tetrahydroisoquinoline-Based HDACI
Table 3: Effects of compounds
on a mouse MDA-MB-231 xeno-
graft model
Compound
Body weight (g)
Liver weight (g)
Spleen weight (g)
TGIa
T/Ca
Blank control
SAHA (90 mg/kg, po)
2 (90 mg/kg, po)
25.37 ꢁ 1.27
23.23 ꢁ 2.08
25.61 ꢁ 1.41
2.1 ꢁ 0.43
1.69 ꢁ 0.2
1.67 ꢁ 0.58
0.2 ꢁ 0.07
0.17 ꢁ 0.06
0.16 ꢁ 0.06
–
56%
59%
–
52%
49%
TGI, tumor growth inhibition.
aCompared with the control group, all treated groups showed statistically significant (P < 0.05)
TGI and T/C by Student’s two-tailed t-test.
Tumor growth inhibition = (the mean tumor weight of con-
trol group – the mean tumor weight of treated group)/the
mean tumor weight of control group.
treated mice (Table 3), there was no evidence that com-
pound 2 was more toxic than SAHA. In fact, during experi-
ment no obvious body weight loss was detected in mice
treated by compound 2.
Tumor volume (V) was estimated using the equation
(V = ab2/2, where a and b stand for the longest and short-
est diameter, respectively). T/C was calculated according
to the following formula:
Conclusion and Future Directions
Structural modification in our previously discovered potent
HDACI compound 1 led to another oral active HDACI
compound 2 with efficacious inhibitory activity against
HDAC1, HDAC2, HDAC3, and HDAC6. Compared with
the approved HDACI SAHA, compound 2 exhibited similar
even superior in vitro antiproliferative activity and in vivo
antitumor potency in a MDA-MB-231 xenograft model.
Compared with its parent compound 1, compound 2 pos-
sesses more convenient synthetic route and less chiral
center, which facilitates its further research and develop-
ment as a new drug candidate. Currently, related pharma-
cokinetic research of compound 2 is underway to find out
if VPA could be released by in vivo metabolism of com-
pound 2. On the other hand, the simplified structure and
T/C ¼the mean RTV of treated group
=the mean RTV of control group
RTV, namely relative tumor volume = Vt/V0, (Vt: the tumor
volume measured at the end of treatment; V0: the tumor
volume measured at the beginning of treatment).
The data present in Table 3 tumor growth curve (Fig-
ure 5A) and the final tumor volume (Figure 5B) showed
that compound 2 (TGI = 59%, T/C = 49%) possessed
comparable in vivo antitumor activity to the approved drug
SAHA (TGI = 56%, T/C = 52%). According to the final
body weight and the dissected liver and spleen weight of
A
B
Figure 5: (A) Growth curve of implanted MDA-MB-231 xenograft in nude mice. Data are expressed as the mean ꢁ standard deviation.
(B) The picture of dissected MDA-MB-231 tumor tissues. The largest and smallest tumor tissues of every group were omitted.
O
O
O
O
O
N
H
H
N
N
N
OH
g
H
HO
O
O
NH
O
O
O
5
4
2
O
Scheme 1: Reagents and conditions: (a) i). TBTU, Et3N, THF; ii). NH2OK, CH3OH, 32% for two steps.
Chem Biol Drug Des 2013; 82: 125–130
129

Zhang et al.
lower molecular weight of compound 2 leave a margin of
subsequent structural modification to further increase its
activity. We are endeavoring to search more potent HDACI
using compound 2 as the lead.
of cancer: overview and perspectives. Future Med
Chem;4:1439–1460.
8. Zhang Y., Feng J., Liu C., Zhang L., Jiao J., Fang H.,
Su L., Zhang X., Zhang J., Li M., Wang B., Xu W.
(2010) Design, synthesis and preliminary activity assay
of
1,2,3,4-tetrahydroisoquinoline-3-carboxylic
acid
Acknowledgments
derivatives as novel histone deacetylases (HDACs)
inhibitors. Bioorg Med Chem;18:1761–1772.
This study was supported by National Scientific and
Technological Major Project of Ministry of Science and
Technology of China (Grant No. 2011ZX09401-015),
National Natural Science Foundation of China (Grant No.
21172134), Doctoral Foundation of Ministry of Education
of China (Grant No. 20110131110037), Independent
Innovation Foundation of Shandong University, IIFSDU
(Grant No. 2013GN013), and National Cancer Institute of
9. Zhang Y., Feng J., Jia Y., Wang X., Zhang L., Liu C.,
Fang H., Xu W. (2011) Development of tetrahydroiso-
quinoline-based hydroxamic acid derivatives: potent
histone deacetylase inhibitors with marked in vitro and
in vivo antitumor activities. J Med Chem;54:2823–
2838.
10. Zhang Y., Fang H., Feng J., Jia Y., Wang X., Xu W.
(2011) Discovery of a tetrahydroisoquinoline-based hy-
droxamic acid derivative (ZYJ-34c) as histone deacety-
lase inhibitor with potent oral antitumor activities. J
Med Chem;54:5532–5539.
the
National
Institute
of
Health
(Award
No.
R01CA163452).
There is no conflicts of interest.
11. Fass D.M., Shah R., Ghosh B., Hennig K., Norton S.,
Zhao W.N., Reis S.A., Klein P.S., Mazitschek R., Mag-
lathlin R.L., Lewis T.A., Haggarty S.J. (2011) Short-
chain HDAC inhibitors differentially affect vertebrate
development and neuronal chromatin. ACS Med Chem
Lett;2:39–42.
12. Feng J., Fang H., Wang X., Jia Y., Zhang L., Jiao J.,
Zhang J., Gu L., Xu W. (2011) Discovery of N-hydroxy-
4-(3-phenylpropanamido) benzamide derivative 5j, a
novel histone deacetylase inhibitor, as a potential ther-
apeutic agent for human breast cancer. Cancer Biol
Ther;11:477–489.
13. Inks E.S., Josey B.J., Jesinkey S.R., Chou C.J. (2012)
A novel class of small molecule inhibitors of HDAC6.
ACS Chem Biol;7:331–339.
14. Bradner J.E., West N., Grachan M.L., Greenberg E.F.,
Haggarty S.J., Warnow T., Mazitschek R. (2010)
Chemical phylogenetics of histone deacetylases. Nat
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