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and Epidermal Growth Factor Receptor Gene Expression in Isolated Prostatic Epithelial and Stromal Cells1
Center for Reproductive Biology, Department of Genetics and Cell Biology, Washington State University, Pullman, Washington 99164-4231
Address all correspondence and requests for reprints to: Michael K. Skinner, Ph.D., Center for Reproductive Biology, Department of Genetics and Cell Biology, Washington State University, Pullman, Washington 99164-4231. E-mail: skinner{at}mail.wsu.edu
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Abstract |
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(TGF-) is one of
the growth factors that can stimulate prostatic growth. The expression
of TGF- is thought to be regulated by androgen. The expression of
epidermal growth factor receptor (EGFR), which is the receptor of
TGF- and EGF, also may be regulated by androgen. The hormonal and
developmental regulation of TGF- and EGFR messenger RNA (mRNA)
levels in isolated epithelial and stromal cells from rat ventral
prostate was investigated. The expression of mRNA for TGF- and EGFR
was analyzed by a quantitative RT-PCR (QRT-PCR) procedure developed.
Observations from this assay demonstrated that both epithelial and
stromal cells expressed the mRNA for TGF- and EGFR. TGF- mRNA
expression was constant during postnatal, pubertal, and adult
development of the prostate. EGFR mRNA expression was elevated at the
midpubertal period and decreased with age. After castration of
60-day-old adult rats, both TGF- and EGFR mRNA were significantly
enhanced. TGF- mRNA expression was stimulated by EGF in stromal
cells (4.5-fold increase) but was not changed by any treatment in
epithelial cells. EGFR mRNA levels were stimulated by EGF and
keratinocyte growth factor treatment and inhibited by testosterone
treatment in epithelial cells. Stromal cell EGFR mRNA levels were not
affected by any treatment. Both testosterone and EGF stimulated
incorporation of 3H-thymidine into prostatic stromal and
epithelial cells. Anti-TGF- antibody significantly inhibited
testosterone-stimulated 3H-thymidine incorporation into
stromal cells and epithelial cells. Immunocytochemical localization of
TGF- and EGFR demonstrated expression on the luminal surface of
epithelial cells within prostatic ducts, and minimal expression was
observed in stromal cells.
Results indicate that testosterone does not directly regulate TGF-
mRNA levels but does inhibit EGFR mRNA levels. Interestingly, anti
TGF- antibody suppressed the effect of testosterone on
3H-thymidine incorporation into prostatic stromal and
epithelial cells. This finding suggests that testosterone may act
indirectly on prostatic cells to influence TGF- actions. TGF-
mRNA levels were influenced by EGF in stromal cells only, and EGFR mRNA
levels were influenced by testosterone, EGF, and keratinocyte growth
factor in epithelial cells. These observations suggest that regulation
of TGF- and EGFR is distinct between the cell types. In conclusion,
a network of hormonally controlled growth factor-mediated
stromal-epithelial interactions is needed to maintain prostate
development and function.
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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(TGF-), epidermal growth factor (EGF), basic
fibroblast growth factor, keratinocyte growth factor (KGF), and
insulin-like growth factors stimulate growth of prostatic epithelial
cells (6, 8, 9). Transforming growth factor-ß (TGF-ß) has an
inhibitory effect on prostatic cell growth (10, 11, 12). Because androgen
is essential to maintain growth, development, and function of the
prostate, the regulation of these growth factors by androgen has been
studied (7, 10, 13, 14).
TGF- and EGF are mitogenic polypeptides that consist of 50 and 53
amino acids, respectively, and act on cells by binding the EGF receptor
(EGFR) (15). TGF- is structurally and biologically similar to EGF.
High concentrations of EGF were determined in rat prostate
(16, 17). EGFR expression was observed in rat epithelial cells (18).
After castration, both EGF and EGFR expression increase, and expression
is decreased with subsequent androgen treatment (13, 19, 20), although
some investigators have found that EGF expression may fall
after castration (for review, see Ref.8). These observations suggest
that EGF/TGF may have a crucial role in the prostate and that EGF
and EGFR seem to be negatively regulated by androgen. TGF-
expression has been demonstrated in normal rat ventral
prostate (18). TGF- is thought to have a role also in prostate
cancer. TGF- expression has been observed in prostatic carcinoma and
prostatic carcinoma cell lines such as LNCaP, PC-3, and DU-145
(21, 22, 23). It has not been reported whether TGF- expression is
directly regulated by androgen. Regulation of growth factor
expression is complex and influenced not only by androgens but also by
a network of locally produced factors within the prostate. We have
recently reported that TGF-ß expression is regulated by EGF and KGF
but not testosterone (24), whereas TGF-ß1 is negatively regulated by
androgen in vivo.
The aim of the current study was to investigate the hormonal and
developmental regulation of TGF- and EGFR messenger RNA (mRNA)
expression in rat ventral prostate. A quantitative reverse
transcription PCR (QRT-PCR), to quantitate mRNA levels, was
established. The expression of TGF- and EGFR mRNA were analyzed in
fresh ventral prostate from neonate to older ages and in isolated
prostatic stromal and epithelial cells derived from 20-day-old rat
ventral prostate.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Culture of ventral prostate cells
Twenty-day-old SD rats were killed, and ventral prostates were
removed. Tissue was incubated with HBSS (Gibco BRL, Gaithersburg, MD)
containing 675 U collagenase activity/ml of Type II collagenase (Sigma,
St. Louis, MO) and 0.04% deoxyribonuclease I (Sigma) at 37 C for
4 h. After incubation, tissue was separated by centrifugation. The
mixture was spun at 30 x g for 4 min to pellet the
epithelial cells. The remaining supernatant was centrifuged at 190
x g for 6 min to pellet the stromal cells. To ensure highly
pure populations of cell types, both pellets were resuspended and spun
at 30 x g for 4 min. The supernatant from stromal
cells was removed and repelleted at 190 x g for 6 min.
These isolated cell populations were then subsequently placed in 10%
bovine calf serum F12 media. After 24 h, the cells were washed in
serum-free F12 media for 24 h. The following day, the media was
changed with F12, with or without the following treatments:
10-7 M testosterone (Sigma), 100 ng/ml EGF
(Gibco BRL), 25 ng/ml KGF (Gibco BRL), 10 ng/ml human recombinant
TGF-ß1 (Gibco BRL), 10% bovine calf serum (Hyclone, Logan, UT),
combination of TGF-ß1 and testosterone 10-7
M, EGF or 10% bovine calf serum. The treatments were for a
period of 72 h. On the sixth day of culture, cells were harvested
for RNA extraction. Cell purity has been studied in previous reports
(24) and was analyzed using immunohistochemistry of both cell
populations.
RNA preparation
Total RNA was obtained using TRI REAGENT (Sigma). Briefly,
tissue or cells were lysed in TRI REAGENT (1 ml per 50–100 mg of
tissue, 1 ml per 10 cm2 of culture plate). After adding 0.2
ml chloroform per ml of TRI REAGENT, the mixture was centrifuged at
12,000 x g for 15 min at 4 C. Colorless upper aqueous
phase was transferred to a fresh tube, and 0.5 ml isopropanol per ml of
TRI REAGENT was added to pellet RNA. The mixture was centrifuged at
12,000 x g for 10 min at 4 C. The RNA pellet was
washed with 75% ethanol and resuspended in diethylpyrocarbonate (DEPC)
H2O. RNA was stored at -80 C until analysis.
RT
Complementary DNA (cDNA) was synthesized in a total vol of 20
µl containing 1 µg total RNA, 0.05 µM of specific
3'-primers (TGF-: 5'-CAG AGT GGC AGC AGG CAG TC-3', EGFR: 5'-GAG TGG
TGG GCA GGT GTC TT-3', cyclophilin: 5'-ATT TGC CAT GGA CAA GAT GCC-3'),
4 µl of 5x first standard buffer (Life Technologies, Gaithersburg,
MD), 10 mM dithiothreitol (Life Technologies), 0.125
mM deoxynucleotide triphosphates, 100 U murine leukemia
virus transcriptase (Life Technologies), 20 U inhibitor (Promega,
Madison, WI), and DEPC-H2O. Initially, RNA was denaturated
and annealed in the presence of each primer and DEPC-H2O at
65 C for 15 min. The tube was placed on ice for 5 min. The other
reagents were added to the tube and incubated at 42 C for 2 h. To
decrease high background signal, a higher RT reaction temperature (42
C) was used (25). The mixture was incubated at 95 C for 5 min to
inactivate murine leukemia virus transcriptase. The mixture was diluted
by UV-treated H2O containing Bluescript plasmid
(Stratagene, La Jolla, CA) as carrier DNA. Final concentrations of cDNA
and Bluescript plasmid were 1 ng/µl and 10 ng/µl, respectively.
This concentration of Bluescript plasmid was included in all samples
and standards.
Quantitative PCR
As a standard, PCR products of TGF-, EGFR, and cyclophilin
(amplified by each specific primer) were subcloned into Bluescript
plasmid (Stratagene). Each subclone was sequenced in both directions
and confirmed to be rat TGF-, EGFR, and cyclophilin. The size of the
PCR product generated was as follows; 138 bp (TGF-), 208 bp (EGFR),
105 bp (cyclophilin). Plasmid DNA containing TGF-, EGFR, or
cyclophilin subclones were used to generate standard curves ranging
from 0.1 fg/µl to 1.0 pg/µl (cyclophilin: 10 fg/µl to 100
pg/µl). PCR was performed on a Perkin-Elmer GeneAmp PCR System 9600
and carried out in a total 25-µl reaction vol containing 5 µl of
the plasmid DNA or RT reaction, 0.4 µM of 3' primer as
shown above, 0.4 µM of 5' primer (TGF-: 5'-TGG CTG TCC
TCA TTA TCA CC-3', EGFR: 5'-CTG CTG GGG AAG AGG AGA GGA GAA C-3',
cyclophilin: 5'-ACA CGC CAT AAT GGC ACT GG-3'), 2.5 µl of x10
GeneAmp PCR buffer (containing 1.5 mM MgCl2,
Perkin-Elmer, Branchburg, NJ), 25 µM deoxynucleotide
triphosphates, 0.5 U of Taq DNA polymerase (Perkin-Elmer), 1
µCi of [ -32P] deoxycycidine triphosphate
(Amersham Life Science, Inc. Arlington Heights, IL).
The reaction cycle sequence comprised 5 min at 95 C followed by 25
cycles comprising 1 min at 95 C, 2 min at 55 C, 3 min at 72 C for
TGF- (EGFR: 30 cycles); and 25 cycles comprising 1 min at 95 C, 1
min at 60 C, 2 min at 72 C for cyclophilin.
After PCR, the PCR products were separated by electrophoresis on 6%
acrylamide gel. After running the gel, it was dried and analyzed by a
Phosphoimager (Molecular Dynamics, Sunnyvale, CA). Each gene was
assayed in separate PCR reactions from the same RT samples. Equivalent
steady-state mRNA levels for each gene were determined by comparing
each sample with the appropriate standard curve. TGF- and EGFR were
normalized for cyclophilin. All samples were simultaneously measured in
duplicate with an intraassay variability of 5.3% (TGF-), 12.2%
(EGFR), and 9.2% (cyclophilin).
3H -Thymidine incorporation assay
Cell growth was analyzed by quantitating
3H-thymidine incorporation into newly synthesized DNA.
Stromal and epithelial cells were placed at subconfluent densities
(less than 1 million cells/cm2) in 0.5 ml DMEM containing
0.1% calf serum. Cells were plated for 24 or 48 h then treated
for an additional 24 h. After treatment, 0.5 ml DMEM containing 2
µCi 3H-thymidine was added to each well, and cells were
incubated for 4 h at 37 C, followed by sonication. The quantity of
3H-thymidine incorporated into DNA was determined as
previously described (26). Data were normalized to total DNA per well
using an ethidium bromide procedure, described previously (27). Under
these subconfluent culture conditions, approximately 0.5–1.5 µg DNA
was detected per well. Values of 3H-thymidine incorporation
were generally greater than 2 x 103 cpm/µg DNA.
Immunocytochemistry
Ventral prostate sections were obtained from 20-day-old
Sprague-Dawley rats. Tissue specimens were immediately fixed in
Bouin’s solution for 3–6 h. Tissue was sectioned at 5-µm thick,
deparaffinized, rehydrated, and treated with an aqueous solution of
3.0% H2O2 to quench endogenous peroxidase.
After several washes in Tris-buffered saline (TBS) buffer, sections
were then incubated in TBS containing 1% BSA for 2 h at 37 C to
reduce nonspecific staining. After rinsing three times in TBS, a sheep
antirat TGF- antibody (East Acres Biological, South Bridge, MA) or a
monoclonal EGFR antibody (Sigma) was added at a 1:500 and 1:100
dilution, respectively, and incubated overnight at 37 C, followed by
2 h at 4 C. After three rinses in TBS, the primary antibody was
detected with antisheep or antimouse biotinylated secondary antibody,
and the biotin was detected with an avidin-biotin peroxidase kit
(ABC-Elite, Vector Laboratories, Burlingame, CA). Diaminobenzidine
tetrachloride was used as a chromagen, and serial sections were lightly
counterstained with hematoxylin.
Statistical analysis
All data were analyzed by a JMP 3.1 statistical analysis program
(SAS Institute Inc., Cary, NC). All values are expressed as mean
± SEM Statistical analysis was performed using one-way
ANOVA. Significant differences were determined using the Dunnett’s
test for comparison with control and using the Tukey-Kramer HSD
(honestly significant difference) test for multiple comparisons.
Statistical difference was confirmed at P < 0.05.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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and EGFR increased at 21 cycles and
reached a plateau at 30 cycles. This suggested that 25 cycles was an
appropriate cycle number for QRT-PCR (Fig. 1
). For EGFR the PCR, product continued
to amplify at 39 cycles. Thirty cycles was midpoint on the linear
amplification of the PCR product and was judged appropriate for
analysis (Fig. 1). In regard to cyclophilin, we have previously
reported that 25 cycles is appropriate (24). Products of both standard
plasmid DNA, which contained a subcloned PCR product containing rat
cDNA and cDNA produced from an unknown sample, were analyzed. PCR
products of diluted plasmid DNA and diluted unknown cDNA were compared.
These two curves were parallel and indicated that the QRT-PCR is
reliable for quantitative analysis (Fig. 2, A and B). The coefficient of variation
for the intraassay and interassay variability was found to be between 5
and 10%.
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The QRT-PCR was used to quantitate mRNA expression of TGF- and EGFR
in both stromal and epithelial cells of rat ventral prostate.
Differences in expression between freshly isolated cells and cultured
cells were examined. In fresh samples (20-day-old rat prostate),
TGF- expression normalized by cyclophilin ranged from
0.001–0.004 x 10-3. These values were lower than
EGFR, which ranged from 0.006–0.028 x 10-3 (Fig. 3). EGFR and TGF expression was
significantly higher (P < 0.01) in cultured epithelial
cells, compared with freshly isolated cells. Cultured and freshly
isolated stromal cells showed comparable levels of expression with no
statistically significant difference.
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and EGFR and EGFR mRNA levels during
rat prostate development from a neonatal period (1-day-old) to an older
age (100-day-old), ventral prostates were removed from rats aged 1, 20,
60, and 100 days of age, and the mRNA levels were measured by QRT-PCR.
The effects of androgen depletion on TGF- and EGFR expression were
analyzed by castration of 60-day-old rats. All the expression data for
TGF- and EGFR were normalized by cyclophilin expression. Relative
mRNA levels, compared with 20-day-old mRNA levels set as 1.0, are
presented for comparative purposes. TGF- expression did not vary
during development (Fig. 4). After
castration of 60-day-old rats, TGF- mRNA levels significantly
increased to 4.7-fold that of 60-day-old rats. EGFR expression was
increased in a midpubertal stage and tended to decrease with age. After
castration, EGFR expression elevated to 3.7-fold that of 60-day-old
rats; however, not significantly different from 20-day-old levels of
expression (Fig. 4). Except for the castration data, the error
associated with individual developmental points was relatively low, and
it represents the mean ± SEM from 3–5 different
experiments.
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and EGFR and EGFR expression (i.e. mRNA levels), both stromal
and epithelial cells from ventral prostate of 20-day-old rats were
cultured and treated. EGF and KGF were used as stimulatory growth
factors, and human recombinant TGF-ß1 was used as an inhibitory
growth factor. TGF-ß1 was combined with testosterone or EGF to study
potential suppressive effect. All values were normalized by cyclophilin
and expressed as relative expression, compared with control nontreated
cells.
EGF significantly stimulated (4.2-fold) TGF- expression in stromal
cells, and the EGF effect was not inhibited by TGF-ß1 (Fig. 5A). Combination of EGF and TGF-ß1
stimulated TGF- expression 2.8-fold but was not significant.
Testosterone (10-7 M) had no effect on the
expression of TGF-. Similar observations were made with
10-6 M and 10-8 M
concentrations of testosterone (data not shown). KGF and TGF-ß1 alone
also showed no effect on TGF- mRNA levels. TGF-ß1 did not
influence the effect of testosterone on TGF- expression.
Interestingly, in epithelial cells, no treatment was found to alter the
expression of TGF- (Fig. 5A).
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). In epithelial cells, both KGF and EGF significantly stimulated
EGFR expression. This stimulation by EGF was suppressed by TGF-ß1.
TGF-ß1 alone did not affect EGFR expression (i.e. mRNA
levels). Testosterone (10-7 M) significantly
inhibited EGFR expression. A combination of testosterone and TGF-ß1
had the same suppression as testosterone alone. Therefore, the only
effect of TGF-ß1 was an inhibition of EGF on EGFR mRNA expression in
epithelial cells.
Cell growth assays
Cultured 20-day-old rat ventral prostate cells were used to
examine the effects of testosterone, EGF, KGF, and TGF-ß1 on cell
growth. A 3H-thymidine incorporation assay was performed. A
10% bovine calf serum positive control treatment significantly
stimulated (about 4- to 5-fold) DNA synthesis in both stromal and
epithelial cells. Testosterone and EGF stimulated (2.5- to 3-fold) DNA
synthesis in both stromal and epithelial cells (Fig. 6). Anti-TGF- antibody alone showed no
effect on DNA incorporation in either stromal or epithelial cells.
However, anti-TGF- antibody significantly suppressed the effect of
testosterone in both stromal cells and epithelial cells. Therefore, the
effects of testosterone on tritiated thymidine incorporation are, in
part, mediated by TGF-. The TGF- antibody has previously been
shown not to cross-react with EGF, basic fibroblast growth factor,
heregulin, or TGF-ß (data not shown). Although the effects of the
TGF antibody completely inhibited androgen action, multiple factors
are likely needed to regulate prostate cell growth and androgen
actions.
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). Sections
were incubated with a TGF- or EGFR antibody (Fig. 7). Controls with
nonspecific IgG also are shown. Staining of both TGF- and EGFR was
localized to the luminal side of selected epithelial cells of the
prostate ducts. The expression pattern was similar in different regions
of the ventral prostate [Fig. 7, A and B vs. (C and D)].
Minimal staining was detected in the stromal cells. Results suggest
that the prostate epithelial cells express higher levels of TGF- and
EGFR protein than stromal cells.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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is structurally and biochemically similar to EGF.
The role of TGF- in the rat ventral prostate remains to be
elucidated. In the current study, TGF- and EGFR mRNA levels during
development of prostate and in isolated epithelial and stromal cells
were investigated. TGF- and its receptor protein were previously
shown in rat ventral and lateral prostate by an immunohistochemical
study (18). Protein for TGF- was only detected in the epithelial
cells after 28 days of age in the rat (18). In the current study, both
proteins were localized in epithelial cells in 20-day-old rat prostate.
Moreover, TGF- and EGFR mRNA were found to be expressed in both
epithelium and stromal cells using fresh and cultured samples. The
results of localization of mRNA and protein does not directly
correspond. The sensitivity of the detection procedure for protein,
compared with mRNA detection, is likely a factor to be considered. In
addition, the stromal-derived TGF may act on epithelial cells that
results in localization of protein but not mRNA.
A stimulatory effect of TGF-/EGF on the prostate was suggested,
because EGF stimulated DNA synthesis in epithelial and stromal cells
(31, 32, 33). Interestingly, anti-TGF- antibody inhibited the effect of
testosterone on tritiated thymidine incorporation into prostatic cells.
These observations suggest that the effects of testosterone on
prostatic cells are mediated, in part, by TGF-. Although the TGF-
antibody completely blocked androgen stimulated growth, the actions of
androgen likely involved multiple factors. Interestingly, testosterone
did not show any effect on TGF- expression (i.e. mRNA
levels) in vitro. Whether the in vitro conditions
inhibited androgen actions or that multiple factors are needed to
mediate androgen action remains to be elucidated. After castration of
60-day-old rats, TGF- and EGFR mRNA expression was elevated about
4-fold. Both binding capacity of ligand to EGFR and EGFR mRNA in rat
ventral prostate were confirmed to be increased after castration by
ligand binding study and Northern blot analysis, respectively (7, 19).
The current study showed the same increase in EGFR mRNA. From these
observations, TGF- and EGFR expression seems to be regulated by
testosterone in vivo; however, its actions may not be
direct, and they may be mediated by other factor(s).
During rat prostatic development, TGF- mRNA expression was not
changed, whereas EGFR mRNA expression was increased at midpuberty and
decreased with age. Thomson et al. (34) reported changes in
TGF- and EGFR mRNA in rat ventral prostate during development (from
2-day-old to adult) by ribonuclease protection assay. Results were
similar to those of the current study. They also reported that the
expression of an epithelial marker remained constant during development
(34). This observation suggests that the stroma/epithelium ratio
remains constant during development of the prostate. It is also
suggested that the changes in growth factor expressed were not caused
by changes in the stroma/epithelium ratio. Using immunocytochemistry,
Taylor et al. (18) showed that protein for TGF- was
expressed in the apical region of rat ventral prostatic epithelial
cells after 28-days. They concluded that TGF- may promote
differentiation rather than proliferation of the epithelial cells of
rat ventral prostate. On the other hand, normal human prostatic
epithelial cells expressed EGFR but were unreactive for TGF-,
whereas stromal cells expressed TGF- but not EGFR protein (35).
Other reports suggested an autocrine loop of TGF-/EGFR, because
TGF- transcription was detected in prostatic carcinoma but not in
benign prostatic hyperplasia (36, 37, 38). Results presented in the current
study indicate an apical/luminal localization in selected epithelial
cells but minimal expression in stromal cells (Fig. 7). The
significance of the TGF-, EGF, and EGFR system still remains to be
elucidated in the prostate. The differences among species, age, and
disease state may change expression of mRNA and protein of these growth
factors and receptor. Further study is required to elucidate the growth
factor network in the prostate.
In cultured epithelial cells, the expression of EGFR (i.e.
mRNA levels) was suppressed by testosterone. This observation suggests
that testosterone down-regulates EGFR expression. In normal rat ventral
prostate, androgens down-regulate EGF binding capacity by 6-fold (19).
In contrast, in a prostatic carcinoma cell line, androgens up-regulate
EGFR expression (39). At the midpubertal stage, EGFR was found to be
elevated. The prostate is rapidly growing at this stage, and it is
likely that an increase of EGFR is required for cell proliferation and
differentiation. However, once prostate growth is complete, EGFR is
suppressed. The cultured cells used in the current study were derived
from 20-day-old rats to correlate to the growth period of the prostate.
Although the relationship between androgen and the expression of
TGF- and EGFR mRNA was not obvious in rat prostatic development, the
expression of TGF- and EGFR was increased in 60-day-old rats after
castration. After castration, many growth factors are elevated (7, 10, 24). It is speculated that elevation of TGF- and EGFR, after
castration, is induced by dramatic changes in local growth factors. The
altered expression of these growth factors after castration will have a
role in inducing prostate cell death and decreasing prostate weight.
The cultured cells used in the current study contain low levels of
contaminating cell populations, which needs to be considered in any
data interpretation involving the cultured cells.
In regard to the relationships between growth factors, TGF-
mRNA expression was stimulated by EGF in stromal cells, whereas EGFR
mRNA was regulated by testosterone, EGF, and KGF in epithelial cells.
These observations are interesting, and they suggest potential
stromal-epithelial interactions. The expression of TGF- and EGFR
were confirmed in both stromal and epithelial cells; however, the
regulation of TGF- and EGFR is distinct in stroma and epithelium. In
carcinoma and benign prostate hyperplasia, the EGF/TGF- and EGFR
generate an autocrine loop (35, 36, 37, 38, 39). EGF has a stimulatory effect on
the expression of TGF- and EGFR. EGF up-regulation suggests
potential autocrine and paracrine interactions. This is the first
report of a role of KGF in the expression of TGF- and EGFR in the
rat prostate gland. KGF stimulated EGFR mRNA expression. This
observation suggests that KGF has a stimulatory effect on the
EGF/TGF--EGFR system. However, EGF and KGF also stimulated TGF-ß
expression, which is one of the inhibitory factors of prostatic growth
(24). The fact that EGF and KGF both have stimulatory and inhibitory
effects suggests that there is a network of growth factors to maintain
homeostasis of cell proliferation and death of prostatic cells.
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Acknowledgments |
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Footnotes |
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Received August 18, 1997.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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and its receptor are expressed in the epithelium of the rat
prostate gland. Endocrinology 133:1306–1311[Abstract]
(TGF- ) and epidermal growth factor
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and EGF on cell proliferation and cell death in rat
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and the epidermal growth factor receptor in human prostate tissues.
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in human hyperplastic prostate tissue: expression and
cellular localization. J Clin Endocrinol Metab 81:4148–4154This article has been cited by other articles:
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