Synthesis and biological evaluation of arylcinnamide linked combretastatin-A4 hybrids as tubulin polymerization inhibitors and apoptosis inducing agents

Article abstract of DOI:10.1016/j.bmcl.2016.03.049

A series of new molecules have been designed based on a hybridization approach by combining the arylcinnamide and combretastatin pharmacophores. These were synthesized and evaluated for their cytotoxic activity, effect on inhibition of tubulin polymerization and apoptosis inducing ability. Most of the conjugates exhibited significant cytotoxic activity against some representative human cancer cell lines and two of the conjugates 6i and 6p displayed potent cytotoxicity with GI₅₀ values of 56 nM and 31 nM respectively against the human breast cancer cell line (MCF-7). SAR studies revealed that 3,4-substitution on the phenyl ring of the cinnamide moiety is beneficial for enhanced cytotoxicity. Moreover, G2/M cell cycle arrest was induced by these conjugates (6i and 6p) apart from tubulin polymerization inhibition (IC₅₀ of 1.97 μM and 1.05 μM respectively). Further, mitochondrial membrane potential, Annexin V-FITC and caspase-9 activation assays suggested that these conjugates induce cell death by apoptosis. Docking studies revealed that these conjugates interact and bind at the colchicine binding site of the tubulin.

Full text of DOI:10.1016/j.bmcl.2016.03.049

Accepted Manuscript
Synthesis and Biological Evaluation of Arylcinnamide linked Combretastatin-
A4 hybrids as Tubulin Polymerization Inhibitors and Apoptosis Inducing
Agents
Ahmed Kamal, Bajee Shaik, V. Lakshma Nayak, A.V. Subba Rao, B. Nagaraju,
Ch. Ratna Reddy, Jeevak Sopanrao Kapure, Abdullah Alarifi
PII:
S0960-894X(16)30269-4
DOI:
http://dx.doi.org/10.1016/j.bmcl.2016.03.049
BMCL 23692
Reference:
Bioorganic & Medicinal Chemistry Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
5 November 2015
26 February 2016
14 March 2016
Please cite this article as: Kamal, A., Shaik, B., Lakshma Nayak, V., Subba Rao, A.V., Nagaraju, B., Ratna Reddy,
Ch., Kapure, J.S., Alarifi, A., Synthesis and Biological Evaluation of Arylcinnamide linked Combretastatin-A4
hybrids as Tubulin Polymerization Inhibitors and Apoptosis Inducing Agents, Bioorganic & Medicinal Chemistry
Letters (2016), doi: http://dx.doi.org/10.1016/j.bmcl.2016.03.049
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Synthesis and Biological Evaluation of Arylcinnamide linked
Combretastatin-A4 hybrids as Tubulin Polymerization Inhibitors and
Apoptosis Inducing Agents
Ahmed Kamal,*a,b,c Bajee Shaik,a V. Lakshma Nayak,a A.V. Subba Rao,a B. Nagaraju,a Ch.
Ratna Reddy a and Jeevak Sopanrao Kapure b Abdullah Alarific
aMedicinal Chemistry and Pharmacology, CSIR-Indian Institute of Chemical Technology,
Hyderabad 500007, India
bDepartment of Medicinal Chemistry, National Institute of Pharmaceutical Education and
Research (NIPER), Hyderabad 500 037, India
cChemistry Department, College of Science, King Saud University, Riyadh 11451,Saudi Arabia
Abstract: A series of new molecules have been designed based on a hybridization approach by
combining the arylcinnamide and combretastatin pharmacophores. These were synthesized and
evaluated for their cytotoxic activity, effect on inhibition of tubulin polymerization and apoptosis
inducing ability. Most of the conjugates exhibited significant cytotoxic activity against some
representative human cancer cell lines and two of the conjugates 6i and 6p displayed potent
cytotoxicity with GI50 values of 56 nM and 31 nM respectively against the human breast cancer
cell line (MCF-7). SAR studies revealed that 3,4-substitution on the phenyl ring of the cinnamide
moiety is beneficial for enhanced cytotoxicity. Moreover, G2/M cell cycle arrest was induced by
these conjugates (6i and 6p) apart from tubulin polymerization inhibition (IC50 of 1.97 µM and
1.05 µM respectively). Further, mitochondrial membrane potential, Annexin V-FITC and
caspase-9 activation assays suggested that these conjugates induce cell death by apoptosis.
Docking studies revealed that these conjugates interact and bind at the colchicine binding site of
the tubulin.
Keywords: CA-4, Cinnamides, Conjugate, Cytotoxicity, Cell cycle, Tubulin polymerization.
,a,bCorresponding authors. Tel.: +91-40-27193157; fax: +91-40-27193189 (A.K.); e-mail:
ahmedkamal@iict.res.in (A. Kamal).
1

Microtubules are protein biopolymers formed through polymerization of heterodimers of
α and β tubulins. Tubulin, a globular protein, has emerged as one of the valuable molecular
targets in anticancer drug discovery. Tubulin plays a pivotal role in many cellular processes such
as maintenance of skeletal integrity of cell, cell signaling and segregation of chromosomes
during mitosis.1,2 Several chemical compounds are known to target the microtubule dynamics by
binding to different domains of the tubulin protein and prevent the polymerization or
depolymerization of the microtubules resulting in mitotic spindle arrest.3 In nature,
combretastatins are isolated from the bark of the South African tree Combretum caffrum, which
are well known to effectively bind at the colchicine site of the tubulin and inhibit the
polymerization resulting in the arrest of cell proliferation.4 Combretastatin A-4 (CA-4, 1, Fig. 1)
is the lead compound of this class with high cytotoxic potency against murine lymphocytic
leukemia, human ovarian and colon cancers. However it suffers from limitation of poor aqueous
solubility and to overcome this, prodrug CA-4P (2, Fig. 1) and other synthetic analogues have
been developed, which are undergoing clinical trials.5-9
The structure activity relationship studies of CA-4 suggested the importance of
trimethoxy substitution on ring A and the crucial role played by cis-configuration of the olefinic
bond to impart activity for this well-established pharmacophoric structure. The ring B has been
reported to be tolerant for structural modification for enhancing the pharmacological profile of
the molecule. Particularly, the aminocombretastatins such as AVE-8063 (3, Fig. 1), AVE-8062
(4, Fig. 1) with an amino and amino-serine groups replacing the hydroxyl group at the C-3
position of ring B showed potent inhibition of tubulin polymerization activity and cytotoxicity.
In recent years antitumor activity of cinnamic acid derivatives was explored by many research
groups.10-13 Phenylcinnamide derivative 8H (5, Fig. 1), initially identified by Hergenrother as a
potential anticancer agent,14 induces G2/M-phase cell cycle arrest and cell death in cancer cell
lines. We surmised that by integrating the phenylcinnamide pharmacophore onto the
combretastatin framework may furnish new anticancer agents with enhanced activity. Our efforts
along this direction validated this hypothesis and the results are presented in the following
sections.
2

Figure 1: Tubulin polymerization inhibitors.
The synthesis of cinnamamide linked combretastatin conjugates (6a-q) was accomplished as
illustrated in Scheme 1. The key intermediate, silyl protected nitrobenzaldehyde (9) was prepared
by nitration of isovanillin (7) with nitronium tetrafluoroborate (NO2BF4) in CH2Cl2 at -40 °C to
give 2-nitro isovanillin (8), followed by the free OH group was protected with TBS-Cl in
CH2Cl2 using imidazole as base. The silyl protected nitrobenzaldehyde (9) was subjected to
Wittig reaction with 3,4,5-trimethoxybenzyl triphenylphosphonium bromide (10) in the presence
of sodium hydride to provide a mixture of nitro [Z]-stilbene (11) and [E]-stilbene (12)17. The
nitro [Z]-stilbene (11) was subjected to reduction with zinc-ammonium formate to give the
corresponding amino [Z]-stilbene (13). The amino stilbene was coupled with different substituted
cinnamic acid chlorides (15a-o) [generated from the corresponding cinnamic acids (14a-o)] in
the presence of triethyl amine to afford the silyl protected cinnamamide linked combretastatin
conjugates (16a-o). The later on deprotection with TBAF afforded the desired conjugates (6a-q).
All the new compounds were characterized by standard spectroscopic analysis.
3

Scheme 1: Reagents and conditions: (a) NO2BF4, CH2Cl2, -40 °C; (b) TBSCl, imidazole,
CH2Cl2, 0 °C to rt; (c) NaH, CH2Cl2, 0 °C to rt 12 h; (d) Zn, HCO2NH4, MeOH, rt, 6 h; (e)
4

(COCl)2, CH2Cl2, DMF(cat), 0 °C to rt, 3 h; (f) Et3N, THF,0 °C to rt, 3 h; (g) TBAF, CH2Cl2, 0
°C, 1 h.
The arylcinnamide linked combretastatin-A4 hybrids (6a-q) were then evaluated for their
cytotoxic activity against selected human cancer cell lines like; MCF-7 (breast-ER positive),
DU-145 (prostate), Hop-62, HeLa (cervical), K562 (LIKK), SK-OV-3, Colo-205 (colon),
MAIPa-Ca-2 by using Sulforhodamine B (SRB) method.18,19 The results of this cytotoxicity data
expressed as GI50 values in comparison with CA-4 is summarized in Table 1. Interestingly, these
hybrids showed considerable cytotoxic activity against most of the cell lines with subnanomolar
to micromolar range. Moreover, all the compounds (6a-q) showed more pronounced activity
against MCF-7 cancer cells compared to other cell lines tested with only a few exceptions.
Among them, 6i and 6p exhibited enhanced cytotoxic activity than CA-4 against MCF-7 cancer
cell lines with GI50 values of 0.056 μM and 0.031 μM respectively.
Table 1: Cytotoxic activity (aGI50 in µM) data of compounds, 6a-q by SRB method.
S.No
bMCF7 cDU145 dHOP62 eHeLa
fK562
gSK-
OV-3
0.097
17.6
>100
0.082
17.0
62.6
47.5
>100
0.099
0.096
7.9
hColo205 iMIA-
PaCa-2
0.063
59.5
11.6
0.083
0.072
55.5
0.070
>100
96.4
0.085
0.085
54.1
0.082
65.4
>100
0.060
0.061
79.4
0.0949
18.1
>100
0.0787
15.7
0.094
0.098
>100
0.091
0.097
24.9
13.4
>100
>100
18.0
0.098
93.9
>100
0.098
40.8
>100
78.1
>100
29.9
0.098
23.5
0.097
46.3
>100
14.3
74.0
64.5
nd
6a
6b
6c
6d
6e
10.3
>100
67.6
38.8
6f
0.066
83.7
0.083
>100
0.060
0.072
0.075
0.085
0.117
64.7
43.0
24.0
>100
7.5
0.090
0.099
0.090
15.9
23.5
58.0
6g
6h
6i
6j
6k
6l
6m
6n
6o
6p
6q
CA-4
>100
0.090
0.079
0.084
0.031
17.1
>100
0.099
0.098
0.096
0.086
>100
>100
0.089
74.9
0.056
0.060
0.095
0.074
0.095
19.4
0.094
0.093
0.096
0.082
23.7
0.094
1.8
71.3
49.2
46.8
52.6
0.097
29.8
20.9
31.6j
0.050
0.031
0.079
0.033
0.079
0.045
0.095
0.046
0.044
43.6
0.091
29.2
14.9
0.089
0.099
28.0
24.8
76.0
0.025
0.15j
0.008
0.031j
a
b
c
Note: Concentration of drug causing 50% inhibition of cell growth, Human breast cancer,
d
e
f
g
Human prostate cancer, Human lung cancer, Human cervical cancer, Human leukemia,
5

h
i
j
Human ovarian cancer, Human colon cancer Human pancreatic, NSC 613729, nd= not
determind.
In general, the antiproliferative activities of the tested compounds were more pronounced
against MCF-7 and DU-145 cells as compared with the other cancer cell lines. Moreover, many
derivatives (6a-b, 6d-e, 6i-m and 6o-q) were more active than CA-4 in SK-OV-3 cell line. Many
of the tested compounds such as 6a, 6d, 6j, 6l, 6o and 6p possessed the excellent overall potency
with GI50 values of 0.063-13.4, 0.06-18, 0.06-0.09, 0.03-0.09 and 0.04-14.3 and 0.03-74 µM
against the tested cell lines.
As the congeners in the tested series differ only on the nature and position of substituents on the
cinnamide-aryl ring, a qualitative analysis of structure-acivity relationship may be advanced as
follows. Most notably, compounds possessing free OH or NH2 groups on the cinnamide and
exhibited higher potency in general (6a, 6j, 6l, 6m and 6o). This may be the result of either a
better binding at the cellular target or facile transport across the cell membrane. When the OH
group was masked with methyl (6b) and propargyl (6c) groups, significant loss of activity was
observed. Enhanced in antiproliferative activity was observed when fluorine (6g) was replaced
with nitro (6e) group on para position cinnamide aryl ring. Loss of activity was observed by
increasing halogen size from fluorine (6g) to chlorine (6f). The presence 4-trifluoromethyl (6h)
groups on the cinnamide aryl ring resulted in complete loss of activity. Two of the most active
compounds 6i and 6p possess electronically dissimilar substituents (OMe and F) at the 3 and 4-
positions of the cinnamide aryl ring. Thus it is appearent that the electronic nature of the
cinnamide ring is not affecting the activity. Compound 6p is notable for its excellent
antiproliferative activity, which is superior to the positive control CA-4, against MCF-7, DU-
145, HOP-62 and K562 cell lines. The most cytotoxic hybrids 6i and 6p were taken up for
detailed biological studies, such as effect on inhibition of tubulin polymerization and apoptosis
induction, and the results are described below.
Cytotoxic agents generally alter the regulation of the cell cycle resulting in the arrest of cell
division in various phases, thereby decreasing the growth and proliferation of cancerous cells.20
Cytotoxicity assay showed that the test compounds 6i and 6p induced significant inhibition of
breast cancer cells with GI50 values 0.056 and 0.031 μM respectively. It was of interest to
examine cell-cycle alterations caused by these conjugates in MCF-7 cancer cells to understand
6

the phase distribution. In this study, MCF-7 cells were treated with compounds, 6i and 6p at 50
and 100 nM concentrations for 48 h. The data obtained clearly indicated that these compounds
(6i and 6p) showed G2/M cell cycle arrest when compared to untreated control (Fig. 2).
Figure 2: Cell cycle analysis of 6i and 6p on MCF-7 cells. A: Control cells (MCF-7), B: CA-4
(50 nM), C: 6i (50 nM), D: 6i (100 nM), E: 6p (50 nM) and F: 6p (100 nM).
Table 2: Effect of compounds 6i, 6p, and CA-4 on cell-cycle phase distribution in MCF-7 cells
Sample
Sub G1 %
2.40
G0/G1 %
85.30
S %
3.10
1.43
G2/M %
8.44
A: Control (MCF-7)
B: CA-4 (50 nM)
2.71
56.19
37.41
7

2.56
3.65
2.99
3.07
78.55
28.16
70.02
27.47
2.86
0.35
1.46
0.52
15.25
64.29
23.58
66.13
B: 6i (50 nM)
C: 6i (100 nM)
D: 6p (50 nM)
E: 6p (100 nM)
In general G2/M cell cycle arrest is strongly associated with inhibition of the tubulin
21
polymerization and since compounds 6i and 6p cause cell cycle arrest at G2/M phase, it was
considered of interest to investigate their microtubule inhibitory function.
Figure 3: Effect of conjugates 6i and 6p on tubulin polymerization: tubulin polymerization was
monitored by the increase in fluorescence at 360 nm (excitation) and 420 nm (emission) for 1 h
at 37 °C. All the compounds were included at a final concentration of 3 µM. CA-4 was used as a
positive control. Values indicated are the mean ± SD of two different experiments performed in
triplicates.
8

Tubulin subunits are known to heterodimerize and self-assemble to form microtubules in a time
dependent manner. The progression of tubulin polymerization22,23 was thus examined by
monitoring the increase in fluorescence emission at 420 nm (excitation wavelength is 360 nm) in
384 well plate for 1 h at 37 °C with and without the conjugate at 3 µM concentration in
comparison with CA-4 as a reference. The test compounds (6i and 6p) significantly inhibited
tubulin polymerization by 69.25 and 73.71 % respectively, whereas CA-4 exhibited 72.18 %
inhibition (Fig. 3). This was followed by evaluation of IC50 values for these compounds and the
results are shown in Table 2. The test compounds 6i and 6p showed significant tubulin-assembly
inhibition with IC50 values of 1.97 and 1.05 µM respectively and this data indicates that the IC50
value of 6p is better than that of CA-4 (IC50 =1.48 µM).
Table 3: Inhibition of tubulin polymerization (IC50) of compounds 6i, 6p and CA-4.
Compound
IC50 a ± SD (in µM)
1.97±0.02
1.05±0.07
1.48±0.05
6i
6p
CA-4
Note: a Concentration of drug to inhibit 50% of tubulin assembly.
The maintenance of mitochondrial membrane potential (∆Ψm) is significant for mitochondrial
integrity and bioenergetic function.24 Mitochondrial changes, including loss of mitochondrial
membrane potential (∆Ψm) are key events that take place during drug-induced apoptosis.
Mitochondrial injury by compounds 6i and 6p was evaluated by detecting drops in mitochondrial
membrane potential (ΔΨm). In this study we have investigated the involvement of mitochondria
in the induction of apoptosis by these compounds. After 48 h of drug treatment with these
compounds, it was observed that they reduced mitochondrial membrane potential (ΔΨm) of
MCF-7 cells, assessed by JC-1 staining (Fig. 4). The apoptotic effect of 6i and 6p was also
evaluated by Annexin V FITC/PI (AV/PI) dual staining assay25 to examine the occurrence of
phosphatidylserine externalization and also to understand whether it is due to physiological
apoptosis or nonspecific necrosis.
9

Figure 4: Compounds 6i and 6p triggers mitochondrial injury. Drops in membrane potential
(ΔΨm) was assessed by JC-1 staining of MCF-7 cells treated with test compound and samples
were then subjected to flow cytometry analysis on a FACScan (Becton Dickinson) in the FL1,
FL2 channel to detect mitochondrial potential. A: Control cells (MCF-7), B: CA-4 (50 nM), C: 6i
(50 nM), D: 6i (100 nM), E: 6p (50 nM) and F: 6p (100 nM).
10

Figure 5: Annexin V-FITC staining. A: Control cells (MCF-7), B: CA-4 (50 nM), C: 6i (50 nM),
D: 6i (100 nM), E: 6p (50 nM) and F: 6p (100 nM).
Table 4: Distribution of apoptotic cells in Annexin-V FITC experiment.
Sample
UL %
0.88
UR %
0.95
LL%
97.50
63.83
80.75
69.11
LR %
0.66
A: Control
8.13
24.49
12.03
22.45
3.55
B: CA-4 (50 nM)
C: 6i (50 nM)
D: 6i (100 nM)
6.38
0.84
1.26
7.19
11

1.43
1.38
22.79
26.03
69.31
66.43
6.48
6.16
E: 6p (50 nM)
F: 6p (100 nM)
In this study MCF-7 cells were treated with these compounds for 48 h at 50 and 100 nM
concentrations to examine the apoptotic effect. The percentage of apoptotic cells (upper right and
lower right quadrant of Fig. 3) were increased significantly in treated cells. Results indicated that
compounds 6i and 6p showed 12.87 and 29.27 % (upper right and lower right of Fig. 5) at 50 nM
concentration, whereas they exhibited 29.64 and 32.19 % (upper right and lower right of Fig. 5)
apoptosis at 100 nM concentration respectively for 48 h.
The activation of caspases play an important role in the process of programmed cell death or
apoptosis. Caspases, or cysteine aspartic protease, are a family of cysteine proteases that are
crucial mediators of apoptosis. The MCF-7 cells lack endogenous caspase-3, whereas caspase-9
plays an important role in mediating drug-induced apoptosis.26 MCF-7 cells were treated with
these compounds (6i and 6p) at 100 nM concentration for 48 h. The results demonstrate that
there is 2-3 fold induction in caspase-9 activity when compared to untreated control (Fig. 6),
thereby suggesting that they have the ability to induce cell death by apoptosis in MCF-7 cells.
Figure 6: Effect of compounds 6i and 6p on caspase-9 activity; MCF-7 breast cancer cells were
treated with these compounds at 100 nM concentration for 48 h. Values indicated are the mean ±
SD of two different experiments performed in triplicates.
12

The hybrids synthesized in the present study are designed based on the combretastatin A-4
scaffold, which is well known inhibitor of tubulin polymerization that targets the colchicine
site.27
6i
6p
Figure 7(A): Interaction of the conjugate 6i and 6p with colchicines binding site of tubulin. The
probable hydrogen bonds found were shown in red color. This figure has been generated using
the software PYMOL from the tubulin-colchicine crystal structure.
Figure 7 (B): Overlapping of conjugate 6i (green), 6p (red) and combretastatin A-4 (orange)
Figure 7 (C): Overlay of conjugate 6i (green), 6p (red) and colchicines (yellow). 6i and 6p is
expected to bind in Colchicines-binding domain with different orientation. β-tubulin shows in
pink color and α-tubulin shows in blue color.
13

Docking studies were performed for promising conjugates (6i and 6p) of the series to investigate
the possible binding mode on the colchicine binding site of the tubulin. Coordinates of protein
structure of tubulin-colchicine were obtained from the Protein Data Bank (PDB ID 3E22).
Docking was accomplished into the colchicine binding site of tubulin using AutoDock 4.2
software. Fig. 7(A) shows that trimethoxyphenyl ring of 6i is buried in the hydrophobic pocket
by βLys254, βLeu255, βAla250, βLeu252, βAla316, βLeu248 and βCys241 residues located in
the β-tubulin in a similar manner to that of trimethoxyphenyl group of the colchicine.
Dimethoxyphenyl ring of cinnamide moiety is buried at α,β interface of the tubulin surrounded
by αTyr224, αAsn101, Gly11 and βLeu248. Cinnamide group and B-ring of combretastatin A-4
is also buried at α,β interface of the tubulin and surrounded by βLys352, βThr353, αSer178,
αThr179, αAla180 βAsn258 and αVal181. Whereas the methoxy groups of dimethoxyphenyl
ring established hydrogen bonding interaction with βLys254. In case of 6p, trimethoxyphenyl
ring is buried in hydrophobic pocket surrounded by βCys241, βLeu242, βLeu248, βLys352,
βAla250, βAla316, βThr353 residues located in β-tubulin. Cinnamide group and B-ring of
combretastatin A-4 are buried at α,β interface of the tubulin similar to that of conjugate 6i and
surrounded by βLys252, βLeu255, βAsn350, α Ala180, α Asn101 and α Val181. Diflurophenyl
ring is buried more towards α-tubulin and surrounded by αSer178, αThr179, αGly11 and
αTyr224. Fig. 7 (B) shows molecular docking pose of 6i and 6p overlaying with combretastatin
A-4, whereas Fig. 7 (C) shows that proposed binding pose of 6i (green) and 6p (red) share
similar binding site as of colchicine (yellow) with different orientation where α-tubulin shown in
blue and β-tubulin shown in red color. These studies suggest that conjugate 6i and 6p can
interact with both α-and β-tubulin in colchicine binding pocket.
In conclusion, a new series of CA-4 linked arylcinnamide conjugates (6a-q) have been
synthesized and evaluated for their cytotoxic potential against selected human cancer cell lines.
All the synthesized compounds showed potent cytotoxic activity against the tested cancer cell
lines and two of them (6i and 6p) showed GI50 values 0.056 and 0.031 µM, respectively against
MCF-7 cancer cell line. Flow cytometric analysis of these compounds showed the arrest of the
cell cycle in the G2/M phase leading to caspase dependent apoptotic cell death. These active
compounds (6i and 6p) showed potent inhibition of tubulin polymerization with IC50 values 1.97
and 1.05 µM, respectively. Further studies like, loss of mitochondrial membrane potential,
significant activation and cleavage of caspase-9 activity and Annexin V-FITC assay suggested
14

that cytotoxic efficacy of these compounds is mainly due to inhibition of tubulin polymerization
and subsequent apoptosis. Moreover, docking experiments showed that 6i and 6p interact and
bind efficiently at the colchicine-binding site of tubulin. The results demonstrate that both 6i and
6p are promising leads and could be taken up for further structural modifications in the
development of improved tubulin polymerization inhibitors
Acknowledgement
B.S, A.V.S, and C.R.R, acknowledge CSIR, New Delhi for the award of senior research
fellowship. We also acknowledge CSIR for financial support under the 12th Five Year plan
project “Affordable Cancer Therapeutics (ACT)” (CSC0301) and King Saud University, Riyadh
(Saudi Arabia).
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Synthesis and Biological Evaluation of Arylcinnamide linked Combretastatin-
A4 hybrids as Tubulin Polymerization Inhibitors and Apoptosis Inducing
Agents
Ahmed Kamal, Bajee Shaik, V. Lakshma Nayak, A.V. Subba Rao, B. Nagaraju, Ch. Ratna
Reddy, Jeevak Sopanrao Kapure, Abdullah Alarifi
17