| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Experimental Therapeutics |
The Johns Hopkins Oncology Center, Baltimore, Maryland 21231
 |
ABSTRACT |
|---|
 Top ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
|
INTRODUCTION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Aliphatic and aromatic fatty acids such as sodium butyrate, PB, and its metabolite phenylacetate have been reported to induce tumor cell cytostasis, differentiation, and apoptosis in various hematological and solid tumors, including prostate cancer (5, 6, 7) . HDACs, enzymes that affect eukaryotic chromatin structure, have been shown to be a target for inhibitors inducing differentiation in transformed cells (8, 9, 10) . The HDAC enzyme complex is involved in several important regulatory pathways for growth and differentiation, affecting the activity and expression of cell cycle proteins and nuclear receptors (11) . Interestingly, inhibitors of HDAC have been shown to dramatically potentiate retinoid-induced differentiation of RA-sensitive human acute promyelocytic leukemia cell lines and to restore retinoid response of RA-resistant human acute promyelocytic leukemia cell lines (12) . Aliphatic and aromatic fatty acids have been shown to inhibit HDAC activity (13 , 14) and to induce differentiation through G1 cell cycle arrest and p53-independent up-regulation of p21 (15) . PB and its metabolite phenylacetate require relatively high concentrations and influence several metabolic pathways. In preliminary clinical trials, PB has been shown to have a low toxicity profile but limited clinical benefit (16 , 17) .
Retinoids, like the aromatic fatty acids, have been shown to exert their biological activity by promoting cell differentiation, apoptosis, and inhibiting cell proliferation in several human tumor cell lines (prostate, melanoma, neuroblastoma, leukemia, germ cells, and mammary tumor; Ref. 1 ). Retinoid receptors, RAR and RXR, are members of the nuclear hormone receptor superfamily (18, 19, 20) . These receptors bind to the RARE as RXR/RAR heterodimer and modulate RA-dependent gene expression. One of the target genes of retinoid receptors is RAR-ß, which encodes four transcripts. RAR-ß expression is reduced in many malignant tumors, including lung carcinoma, squamous carcinoma of the head and neck, and breast cancer (21 , 22) . A recent report showed that RAR-ß and RXR-ß mRNA are selectively and significantly reduced in prostate cancer as well as in adjacent normal prostate tissue, suggesting an association between loss of specific retinoid receptor subtypes and prostate carcinogenesis (23) . Interestingly, retinoids, such as short-chain fatty acid, inhibit cell proliferation by inducing G1 cycle arrest and up-regulation of p21 (24) .
An extensive series of clinical studies on CRA in patients with advanced established cancers showed no effect (25) . However, in primary prevention studies involving heavy smokers (26) and in secondary prevention trials in patients with a history of squamous cell carcinoma of the head and neck, CRA showed a significant clinical benefit (27 , 28) .
In the past decade, increased interest has been focused on the role of
new blood vessel formation in the pathogenesis of tumors since the
original observation by Folkman (29
, 30)
. New therapeutic
strategies involving angiogenesis inhibitors are actively under
development. Differentiation agents, such as retinoids and vitamin
D3, have been shown to have a direct inhibitory
effect on tumor-induced angiogenesis. Retinoids directly inhibit
endothelial cell migration and angiogenesis in vivo
(31)
. Interestingly, retinoids have been shown to
down-regulate vascular endothelial growth factor production in normal
human keratinocytes (32)
. Combinations of RA with IFN-
or vitamin D3 have a synergistic antitumor effect
by inducing inhibition of both endothelial cell and tumor cell
proliferation and reducing tumor growth in vivo and
angiogenesis (33
, 34)
. Of interest, both sodium butyrate
and retinoids have been shown to up-regulate tissue type plasminogen
activator in endothelial cells, suggesting the possible role of
increased proteolysis in the modulation of angio-inhibitory cytokines
(35
, 36)
.
The rationale for combining PB and CRA stems from their distinct
activity at the nuclear receptor level. Nuclear hormone receptors have
recently gained attention as selective targets for antineoplastic drugs
(37
, 38) . The human PPARs are nuclear receptors that act
as transcriptional factors. PPARs control the expression of several
genes containing PPAR response elements that are involved in the
peroxisomal and mitochondrial pathway of lipid metabolism
(39)
. PB and phenylacetate have been shown to activate
PPAR- (40)
and PPAR-
(41)
.
Interestingly, PPARs must form a heterodimer with the retinoid receptor
RXR- to function as a transcriptional factor. Prostate carcinoma
cells, similar to other solid tumors such as breast and colon
carcinoma, express high levels of PPARs, in particularly the
subtype (42)
. Recent preclinical reports showed that TZD,
a commonly used antidiabetic drug that acts as a PPAR agonist,
induces differentiation in breast carcinoma (43)
and
liposarcoma (44)
and inhibits prostate carcinoma growth
(42)
.
On the basis of the common signal transduction pathways and possible modulation at the nuclear receptor level, we hypothesized that a combination of PB and CRA may have additive or synergistic inhibitory activity on prostate tumors. In this study, we report on the potent and novel additive inhibitory activity of PB and CRA on several PCA cell line proliferation in vitro and the inhibition of tumor growth in vivo. In addition, we demonstrated that this combination has and additive inhibitory activity on endothelial cell proliferation in vitro and angiogenesis in vivo.
|
MATERIALS AND METHODS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Proliferation Assay.
Briefly, tumor cell lines and BAECs were plated in 24-well plates
(5–10 x 103
/well), and after
overnight incubation in complete medium, cells were treated with 2.5
mM PB or 10 µM CRA or a combination in
complete medium containing <0.1% DMSO. These concentrations were
chosen based on preliminary in vitro studies (data not
shown), reports in the literature, and achievable peak blood
concentrations. At different time points, cells were trypsinized, and
each condition was counted in triplicates on a Coulter Z1 cell counter
(Coulter Electronics). Results are expressed as mean cell
counts/well ± SE. The experiments were repeated twice.
Colony Formation Assay.
Colony formation assay was performed as published previously by other
investigators (45)
. Tumor cells and BAECs were harvested
and replated in six-well plates (5 x 102 cell/well) in absence of drugs and in
complete medium. After 48 h, to allow cell attachment, cells were
treated with 2.5 mM PB or/and 10 µM CRA for
72 h as in the proliferation assay. Then, cells were washed, and
drug-free complete medium was added. As the colonies became visible (10
days), cells were fixed with methanol, stained with crystal violet, and
counted at the inverted light microscope (Zeiss). Results are expressed
as a mean of total colonies/well ± SE. The experiments
were repeated twice.
Cell Cycle and Apoptosis Assays.
The FlowTACS Apoptosis Detection kit (R&D Systems), which is designed
specifically for in situ detection of apoptotic cells by
flow cytometry, was used according to the manufacturer’s
recommendations. Briefly, tumor cells or BAECs were plated in T75
flasks and treated with the 2.5 mM PB or/and 10
µM CRA for 72 h. Cells were harvested, and
their membranes were permeabilized with CytoPore reagent. Next,
terminal deoxynucleotidyl transferase (R&D Systems) added biotinylated
nucleotides to the 3'-ends of the DNA fragments.
Streptavidin-conjugated fluorescein (FITC) specifically bound to the
biotinylated DNA fragments and was detected by flow cytometry (FACS).
The cell cycle analysis was performed under the same experimental
conditions as described above. Cells were harvested and resuspended in
citrate buffer and stored at -20oC. Prior to
analysis, cells were incubated for 30 min with staining solution
containing 0.1 mg/ml propidium iodide (Sigma Chemical Co.). The
solution was then passed through a nylon mesh filter and analyzed on a
Becton Dickinson FACScan. In a parallel experiment, BAEC nuclei were
stained with 4',6-diamidino-2-phenylindole (Sigma Chemical Co.) and
analyzed at the fluorescence microscope (Zeiss).
RNA Preparation and RT-PCR.
Prostate tumor cells were plated in T75 flasks, grown until 60–70%
confluent, and then treated with 2.5 mM PB or/and 10
µM CRA for 72 h. Cells were harvested, and
extraction of total RNA was performed by using Trizol (Life
Technologies, Inc.), according to the manufacturer’s instructions.
Total RNA samples also were prepared from human breast carcinoma cell
lines Hs578t (positive expression of RAR-ß) and MDA-MB-231 (negative
expression of RAR-ß) as positive and negative controls, respectively.
The Superscript One-Step RT-PCR System (Life Technologies, Inc.) was
used to amplify 50 ng of DNase-treated total RNA. Samples were
processed in a Perkin-Elmer 9600 GeneAmp thermocycling system under the
following conditions: 30 min at 50oC for the
reverse transcriptase reaction; 2-min denaturation step at
94oC; followed by 35 amplification cycles (15 s
at 94oC for denaturation, 30 s at 55°C for
primer annealing, and 1 min at 72°C for primer extension), and final
extension at 72°C for 10 min. PCR products were analyzed on 1.5%
agarose gels. Amplification of RAR-ß2 promoter
(256 kb) was performed by using published primer sequences: exon 5
(sense strand 5'-GAC TGT ATG GAT GTT CGT TCA G-3') and exon 6
(antisense strand 5'-ATT TGT CCT GGC AGA CGA AGC A-3'; Ref.
46
). RT-PCR with primers encoding for 36B4 (human acidic
ribosomal phosphoprotein, 150 kb; sense strand 5'-GAT TGG CTA CCC AAC
TGT TGC A-3' and antisense strand 5'-CAG GGG CAG CAG CCA CAA AGG C-3';
Ref. 47
) was used as an internal RNA control. Primers were
a generous gift from Drs. Smitha Subramanyan and Nicoletta Sacchi
(48)
, Johns Hopkins Oncology Center.
Tumor Growth in Vivo.
Male athymic nude mice (Taconic), 4–6 weeks of age, were kept in a
temperature-controlled room on a 12/12-h light/dark schedule with food
and water ad libitum. Animals were injected s.c. in the
flank regions bilaterally with 2 x 106 prostate carcinoma cells resuspended in
serum-free medium (Life Technologies, Inc.) and mixed with Matrigel
(1:1; Collaborative Biomedical Products) in a final volume of 0.2 ml.
Twenty animals for each tumor were randomly placed in four groups (five
animals/group): control, PB, CRA, and PB + CRA. Animals in
the control group were treated with daily administration of vehicle
(polyethyleneglycol; Fisher) by 20-gauge gavage needle and with i.p.
injections of PBS. The in vivo doses and schedules of PB and
CRA were chosen based on preliminary studies (data not shown) and
reports in the literature (6
, 7
, 49
, 50)
. PB (600
mg/kg/day) was administered concomitantly by i.p. injections (300
mg/kg/day, 9 a.m. and 5 p.m.) and by 2-week osmotic pumps
(300 mg/kg/day; Alza Corp). The osmotic pumps were replaced once. CRA
was administered by gavage needle (30 mg/kg/day, 9 a.m.). Daily
treatment (6 days/week) with PB or/and CRA was initiated 2–5 days
after implantation. Tumor volume was measured with a caliper twice a
week and calculated according to the formula: length x width x height x 0.5236 and reported as
mean mm3
± SE. The animals were
treated for 
4 weeks and then were euthanized; tumors were harvested
for histological studies. All of the in vivo experiments
were repeated once. Animals treated with CRA and CRA + PB
sometimes showed a transient weight loss during the second week of
treatment with spontaneous recovery.
Immunohistochemistry Study.
Formalin-fixed, paraffin-embedded tissue was generated from G-Tumor
xenotransplants. Sections were pretreated with Pronase for 20 min at
37oC and a rabbit antihuman factor VIII antibody
(Dako, Carpinteria, CA; 1:1000) was used on all sections as a specific
marker for endothelial cells. Then, sections were incubated with a
secondary biotin-conjugated goat antirabbit IgG antibody
(1:100 x 30 min at room temperature. Avidin-biotin
peroxidase complex (Vector Laboratories, Burlingame, CA) was prepared
as per the manufacturer’s instructions and allowed to incubate on the
sections. Next, sections were incubated in diaminobenzidine solution,
washed, and counterstained in methyl green. The Image-Pro analysis
system was used to quantify the area occupied by factor VIII-stained
vessels. The mean area/field from 10 to 20 fields/section/plug
(x200 = x20 objective lens and x10 ocular lens; Zeiss
Axio-skop) was calculated. The same sections were also processed in
a similar fashion and stained with monoclonal antibody anti Ki-67/M1B-5
(Beckam Coulter Immunotech) as proliferation marker and with Terminal
Transferase (terminal deoxynucleotidyltransferase-mediated nick end
labeling technique; Boehringer Mannheim) for apoptotic cell detection.
Each section was also stained with H&E.
Angiogenesis Assay in Vivo.
The effect of PB and CRA on new blood vessel formation was assessed in
the Matrigel assay, performed as described previously
(51)
. Briefly, C57/BL6 mice (The Jackson Laboratory) were
randomly divided in four groups (five animals/group): control, PB, CRA,
and PB + CRA. Animals received injections s.c. with 0.75 ml
of Matrigel supplemented with 150 ng/ml bFGF (R&D Systems). PB and CRA
were administered (same doses and schedules as above) starting 5 days
prior to the Matrigel injection and until the end of the experiment.
Control animals received vehicle only. Mice were sacrificed 10 days
after the Matrigel injection. Then, the gels were recovered by
dissection and fixed in PBS-buffered 10% formalin containing 0.25%
glutaraldehyde, prior to staining the slides with Masson’s Trichrome.
The Image-Pro analysis system was used to quantify the area occupied by
vessels in the histological sections. The mean area/field from 10 to 20
fields/section/plug (x200 = x20 objective lens and
x10 ocular lens; Zeiss Axioskop) was calculated and expressed as mean
percentage area occupied by blood vessels ± SE. The
experiment was repeated twice.
Statistical Analysis.
Differences between means of unpaired samples were evaluated by
Student’s t test using the SigmaPlot program (SPSS, Inc.).
P < 0.05 was taken to indicate statistical
significance.
|
RESULTS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
]. However, when tumor cells were treated with both PB and CRA, an
additive inhibitory effect (76–83% inhibition as compared with
control) was observed (P < 0.014
versus single agents). These proliferation data were
confirmed also by colony formation assay. Treatment of DU-145 cells
with PB + CRA resulted in a 77–80% inhibition of colony
formation as compared with control, whereas single agents produced a
48–50% inhibition (P < 0.002 PB + CRA versus control, PB and CRA alone). Similar
results were obtained with the other cell lines (data not shown).
Treatment of prostate carcinoma cells with PB and PB + CRA
resulted in distinct changes in cell morphology. The cells grew slowly
with enlarged cytoplasm and pyknotic nuclei. Flow cytometry analysis
was performed to identify drug-induced changes in the tumor cell cycle.
Treatment of PC3 cells with PB and PB + CRA for 72 h
resulted in increased G1 arrest (94%) and
10-fold decrease in S-phase (3.1%), as compared with control (54 and
30%, respectively; Fig. 2A
). No significant variation with CRA alone or additive
effect with combined drugs was observed. Similar results were observed
with the other cell lines (data not shown). Next, induction of
apoptosis by PB and CRA was assessed. PCA treated with PB or CRA had an
increased apo-ptotic rate as compared with controls (PB: 7-fold
increment, P < 0.024 versus
control; CRA: 1.5 fold increment; Fig. 2B
). Interestingly,
the combination of PB and CRA had an additive effect on apoptosis as
compared with single agents (P < 0.006),
with 15-fold increments as compared with baseline controls
(P < 0.001).
|
|
, Lanes 3–5, respectively). However, in the presence of CRA,
there was 4–6-fold induction of RAR-ß expression by PB (Fig. 3
,
Lane 6). RAR-ß up-regulation by PB + CRA
persisted at 48 and 72 h (Fig. 3
, Lanes 10 and
14, respectively).
|
. However, the combination of PB and CRA resulted in a
significant additive inhibitory effect (up to 90% growth inhibition,
as compared with controls; P < 0.025
versus single agents). The tumor volume data were confirmed
by tumor weight measurements in separate experiments as shown in Table 1
. The combination of PB + CRA resulted in a 70% inhibition of
G-Tumor and DU-145 tumor weights (P < 0.02
versus single agents).
|
|
. After a 3-week interval, drug treatment was resumed, and tumor growth
slowed and reached a plateau. Histological examination of the tumor
during drug administration showed the presence of small cellular
aggregates in the original Matrigel (Fig. 5B)
as compared
with control (Fig. 5A)
. These data show the primary
cytostatic nature of this treatment and infer the need for continuous
administration to achieve the antitumor effect.
|
. Tumor samples from G-Tumor xenotransplants underwent
histological examination. Imunohistochemistry studies showed a
decreased proliferation signal and evidence of areas with increased
G-Tumor cell apo-ptosis in the PB + CRA-treated animals
(Fig. 6, D and F
, respectively). G-Tumor
xenografts originating from PB + CRA-treated animals revealed
also a 62% reduction in blood vessel area by imaging analysis
quantitation (P < 0.0001 versus
control; Fig. 6H
).
|
). However, the combination of PB and CRA had an additive inhibitory
effect (67% reduction), and endothelial cells underwent morphological
changes, presenting enlarged cellular bodies (Fig. 7B)
as
compared with control (Fig. 7A)
. Similar results were
achieved with human umbilical vein endothelial cells (data not shown).
These proliferation data were confirmed by clonogenic assay. BAECs
treated with PB or CRA showed reduction in colony formation by 46 and
55%, respectively, whereas combined drugs demonstrated a 70%
inhibition (P < 0.001 versus
control, PB and CRA alone). BAECs, similar to tumor cells, also showed
active apoptosis upon treatment with PB + CRA (Fig. 7D)
, as compared with control (Fig. 7C)
.
|
. Quantitative analysis of the MVA showed an inhibitory
effect on bFGF-induced neovascularization upon treatment with either PB
or CRA as single agents (39% inhibition; Fig. 8
B). However,
an additive inhibitory effect was achieved when these drugs were
combined (64% inhibition, P < 0.004 PB + CRA versus PB and CRA).
|
|
DISCUSSION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
On the basis of the common signal transduction pathways shared by PB and CRA, we expected an increased inhibition of cell proliferation and apoptosis in tumor cells treated with combined drugs. However, this combination of differentiation-inducing agents revealed primarily a cytostatic activity, as shown in our in vivo studies. No tumor regression was observed, as expected, and tumors were kept "dormant" as long the drugs were administered, with resumption of normal growth rate upon discontinuation of the treatment.
The additive inhibitory activity of PB and CRA may be explained by the
fact that aromatic fatty acids and retinoids likely act through similar
mechanisms to induce tumor cytostasis. Several molecular mechanisms may
underlie these common biological effects between these two classes of
nuclear receptor activators: (a) the signaling pathways
effected by PB and CRA are likely to converge through the formation of
heterodimers between their respective receptors, PPARs and RXR;
(b) phenylacetate/butyrate up-regulate the expression of
RAR-ß and, thus, may enhance retinoid-specific activity
(52)
; (c) evidence exists that histone
acetylation may modulate RA activity. Trichostatin, a specific
inhibitor of HDAC potentiates RA-induced neuronal differentiation by
enhancing RXR/RAR heterodimer binding to RARE (53)
.
Inhibitors of HDAC potentiate or restore retinoid-induced
differentiation in leukemic cells by removing the corepressor and
allowing the transcription of RAREs (12)
; and
(d) PPAR- and RXR-specific ligands may have an additive
effect in inducing differentiation, such as in liposarcoma cell lines
where the adipogenic activity through activation of the PPAR/RXR
heterodimer is maximal when both receptors are bound by their
respective ligands (44
, 54)
.
The identification of the thiazolidinedione drugs as agonist-ligands
for the PPAR receptor has recently provided an attractive
therapeutic opportunity (55
, 56)
. A recent report
describes the successful induction of differentiation of human
liposarcoma in patients treated with TZD, suggesting the clinical
development of receptor-targeted therapeutic interventions to induce
differentiation as an antitumor strategy (57)
.
In a recent study, the PPAR agonist TZD inhibited human PCA growth
in vitro and in vivo (42)
. The
investigators found that human PCA cell lines and human PCA samples
express PPAR, whereas normal prostate tissue has very low
expression. Dose-response clonogenic assays of PC3 cell line treated
with TZD showed an antiproliferative effect. The authors tested the
hypothesis of whether the combination of PPAR and RXR or RAR
agonists may have additive or synergistic effect when combined
together. The RXR and RAR ligands tested were effective against LNCaP,
PC3, and DU-145, whereas TZD inhibited in vitro
proliferation of PC3 only. Interestingly, minimal additional inhibition
occurred when TZD was combined with a RXR ligand and no additional
effect with an RAR agonist. The in vivo experiments showed a
mild inhibitory effect of TZD on PC3 cell xenograft growth and greater
growth inhibition with all-trans RA, but no evidence of an
additive inhibitory effect with the combination of these two drugs.
When we treated the PCA cells with ciglitizone, a pure PPAR agonist,
in the presence of CRA, we did not achieve any additive inhibitory
effect in vitro (data not shown). These results suggest that
the PPAR activity of PB is not responsible for the additive
biological effect in the presence of CRA.
Recently, reports support the hypothesis that chromatin-remodeling drugs, such as HDAC inhibitors and demethylating agents, might provide a strategy to restore RAR-ß activity, and help to overcome the hurdle of RA resistance in tumor cells (i.e., breast cancer; Ref. 48 ). Our study on RAR-ß expression in TSU cells confirms that a HDAC inhibitor, such as PB, is able to activate specific response elements within 24 h of PB exposure. In our case, PB might derepress the RAREs present in the RAR-ß2 promoter region and induce the expression of this receptor in the presence of the ligand. Thus, it would be reasonable to speculate that the additive effect of PB and CRA on PCA shown in our study may be attributable to the HDAC inhibitor activity of PB, which sensitizes tumor cells to RA.
These data are of particular interest. Not only might it explain the molecular mechanism underlying the additive effect of this combination, but also it would suggest a role of this or similar combination in the chemoprevention of prostate cancer. In fact, a growing body of evidence supports the hypothesis that RAR-ß is a tumor suppression gene, and its expression is "silenced" in breast and prostate cancer (22 , 23) . Additional molecular studies are ongoing in our lab to confirm and expand these data.
Our study also suggests that the combination of PB and CRA have a
direct effect on endothelial cells and inhibits angiogenesis in
vivo. A possible role for PB in inhibiting angiogenesis might be
related to its properties as a PPAR agonist. Tumor-associated
macrophages play a key role in tumor angiogenesis by secreting a
repertoire of angiogenic products (58)
. PPAR nuclear
receptor has been identified in monocytes and a wide range of ligands
including TZD, 15-deoxy-
12,14-prostaglandin
J2, and certain nonsteroidal anti-inflammatory
drugs, strongly inhibited macrophage/monocyte cytokine production and
reduced nitric oxide, as well as the secretion of other
inflammatory products such as gelatinase B (59
, 60)
. A recent report also showed that PPAR activators
induce macrophage apoptosis by negatively interfering with the
antiapoptotic nuclear factor-
B signaling pathway
(61)
.
Recently, two compelling reports showed that endothelial cells express
PPAR receptor, and that the bio-active prostanoid
15-deoxy-12,14-prostaglandin J2, which has
PPAR agonist properties, is able to inhibit endothelial cell
proliferation in vitro and angiogenesis in vivo
(62
, 63)
. Additional molecular studies are in progress in
our laboratory to elucidate the molecular mechanism responsible for the
biological effect of PB and CRA on endothelial cells.
In conclusion, our results suggest that the combination of PB and CRA
may have therapeutic potential in the treatment of PCA. We hypothesize
that PB and CRA likely act through similar signal transduction
pathways. The additive effect of combination of PB and CRA may
attributable to the induction of RAR-ß by PB and thus tumor cell
sensitization to CRA. Additional molecular studies are necessary to
elucidate the mechanisms of this interaction. The completion of these
further mechanistic studies will be important so that combination of
newer and more selective agents (i.e., new synthetic
retinoids, PPAR agonists, and HDAC inhibitors) can be assessed in
preclinical studies and tested in the treatment of prostate cancer.
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
1 This work was supported by NIH Grants
K08-CA69164, R01-CA75525, and CaPCURE (to M. A. C.) and a grant from
Gaetano Fichera Fellowship, Associazione Italiana per la Ricerca sul
Cancro (to R. P.). 
2 To whom requests for reprints should be
addressed, at The Johns Hopkins Oncology Center, The Bunting-Blaustein
Cancer Research Building, 1 M88, 1650 Orleans Street, Baltimore MD
21231.
3 The abbreviations used are: PCA, prostate
carcinoma; PB, phenylbutyrate; CRA, 13-cis retinoic
acid; RA, retinoic acid; RAR, RA receptor; HDAC, histone deacetylase;
RXR, retinoid X receptor; RARE, retinoic acid responsive element; PPAR,
peroxisome proliferator-activated receptor; FBS, fetal bovine serum;
BAEC, bovine aorta endothelial cell; FACS, fluorescence-activated cell
sorter; RT-PCR, reverse transcription-PCR; bFGF, basic fibroblast
growth factor; MVA, microvessel area; TZD, troglitazone.
Received 2/ 3/00. Accepted 12/15/00.
|
REFERENCES |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
.. Mol. Cell, 1: 465-470, 1998.[Medline]
12,14-prostaglandin J2 is a ligand for the adipocyte determination factor PPAR.. Cell, 83: 803-812, 1995.[Medline]
(PPAR).. J. Biol. Chem., 270: 12953-12956, 1995. ligand troglitazone in patients with liposarcoma.. Proc. Natl. Acad. Sci. USA, 96: 3951-3956, 1999. agonists inhibit production of monocyte inflammatory cytokines.. Nature (Lond.), 391: 82-86, 1998.[Medline]
is a negative regulator of macrophage activation.. Nature (Lond.), 391: 79-82, 1998.[Medline]
and induces apoptosis of human monocyte-derived macrophages.. J. Biol. Chem., 273: 25573-25580, 1998.12,14-prostaglandin J2.. J. Biol. Chem., 274: 17042-17048, 1999. ligands are potent inhibitors of angiogenesis in vitro and in vivo.. J. Biol. Chem., 274: 9116-9121, 1999.This article has been cited by other articles:
|
|
 |
|
  J. M. Schenk, E. Riboli, N. Chatterjee, M. F. Leitzmann, J. Ahn, D. Albanes, D. J. Reding, Y. Wang, M. D. Friesen, R. B. Hayes, et al. Serum Retinol and Prostate Cancer Risk: a Nested Case-Control Study in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial Cancer Epidemiol. Biomarkers Prev., April 1, 2009; 18(4): 1227 - 1231. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Kato, B. C. Salumbides, X.-F. Wang, D. Z. Qian, S. Williams, Y. Wei, T. B. Sanni, P. Atadja, and R. Pili Antitumor effect of the histone deacetylase inhibitor LAQ824 in combination with 13-cis-retinoic acid in human malignant melanoma Mol. Cancer Ther., January 1, 2007; 6(1): 70 - 81. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Z. Qian, Y. Kato, S. Shabbeer, Y. Wei, H. M.W. Verheul, B. Salumbides, T. Sanni, P. Atadja, and R. Pili Targeting Tumor Angiogenesis with Histone Deacetylase Inhibitors: the Hydroxamic Acid Derivative LBH589 Clin. Cancer Res., January 15, 2006; 12(2): 634 - 642. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
X.-f. Wang, D. Z. Qian, M. Ren, Y. Kato, Y. Wei, L. Zhang, Z. Fansler, D. Clark, O. Nakanishi, and R. Pili Epigenetic Modulation of Retinoic Acid Receptor {beta}2 by the Histone Deacetylase Inhibitor MS-275 in Human Renal Cell Carcinoma Clin. Cancer Res., May 1, 2005; 11(9): 3535 - 3542. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. E. Touma, J. S. Goldberg, P. Moench, X. Guo, S. K. Tickoo, L. J. Gudas, and D. M. Nanus Retinoic Acid and the Histone Deacetylase Inhibitor Trichostatin A Inhibit the Proliferation of Human Renal Cell Carcinoma in a Xenograft Tumor Model Clin. Cancer Res., May 1, 2005; 11(9): 3558 - 3566. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. N. Prasad Multiple Dietary Antioxidants Enhance the Efficacy of Standard and Experimental Cancer Therapies and Decrease Their Toxicity Integr Cancer Ther, December 1, 2004; 3(4): 310 - 322. [Abstract] [PDF]
|
|
|
|
 |
|
 D. Z. Qian, X. Wang, S. K. Kachhap, Y. Kato, Y. Wei, L. Zhang, P. Atadja, and R. Pili The Histone Deacetylase Inhibitor NVP-LAQ824 Inhibits Angiogenesis and Has a Greater Antitumor Effect in Combination with the Vascular Endothelial Growth Factor Receptor Tyrosine Kinase Inhibitor PTK787/ZK222584 Cancer Res., September 15, 2004; 64(18): 6626 - 6634. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Lotan and Y. Lotan Retinoic Acid Receptor {beta}2 Hypermethylation: Implications for Prostate Cancer Detection, Prevention, and Therapy Clin. Cancer Res., June 15, 2004; 10(12): 3935 - 3936. [Full Text] [PDF]
|
|
|
|
 |
|
 M. Michaelis, U. R. Michaelis, I. Fleming, T. Suhan, J. Cinatl, R. A. Blaheta, K. Hoffmann, R. Kotchetkov, R. Busse, H. Nau, et al. Valproic Acid Inhibits Angiogenesis in Vitro and in Vivo Mol. Pharmacol., March 1, 2004; 65(3): 520 - 527. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Simeoni, P. Magni, C. Cammia, G. De Nicolao, V. Croci, E. Pesenti, M. Germani, I. Poggesi, and M. Rocchetti Predictive Pharmacokinetic-Pharmacodynamic Modeling of Tumor Growth Kinetics in Xenograft Models after Administration of Anticancer Agents Cancer Res., February 1, 2004; 64(3): 1094 - 1101. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Pellizzaro, D. Coradini, and M. G. Daidone Modulation of angiogenesis-related proteins synthesis by sodium butyrate in colon cancer cell line HT29 Carcinogenesis, May 1, 2002; 23(5): 735 - 740. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Vivat-Hannah, D. You, C. Rizzo, J.-P. Daris, P. Lapointe, F. C. Zusi, A. Marinier, M. V. Lorenzi, and M. M. Gottardis Synergistic Cytotoxicity Exhibited by Combination Treatment of Selective Retinoid Ligands with Taxol (Paclitaxel) Cancer Res., December 1, 2001; 61(24): 8703 - 8711. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. A. Carducci, J. Gilbert, M. K. Bowling, D. Noe, M. A. Eisenberger, V. Sinibaldi, Y. Zabelina, T.-l. Chen, L. B. Grochow, and R. C. Donehower A Phase I Clinical and Pharmacological Evaluation of Sodium Phenylbutyrate on an 120-h Infusion Schedule Clin. Cancer Res., October 1, 2001; 7(10): 3047 - 3055. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Cancer Research | Clinical Cancer Research |
| Cancer Epidemiology Biomarkers & Prevention | Molecular Cancer Therapeutics |
| Molecular Cancer Research | Cancer Prevention Research |
| Cancer Prevention Journals Portal | Cancer Reviews Online |
| Annual Meeting Education Book | Meeting Abstracts Online |
