MINIREVIEW
Gonadotropin-releasing hormone and ovarian cancer: a
functional and mechanistic overview
Wai-Kin So, Jung-Chien Cheng, Song-Ling Poon and Peter C. K. Leung
Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, Canada
Gonadotropin theory of ovarian cancer
Ovarian cancer is the most lethal gynecological malig-
nancy. Although epithelial ovarian carcinomas account
for approximately 90% of all human ovarian cancers,
the etiology of this disease is poorly understood. Fat-
halla proposed the ‘incessant ovulation theory’ in 1971,
suggesting that continuous ovulation, associated with
successive rounds of surface rupture and repair,
increases the chance of accumulating genetic aberra-
tions and therefore malignant transformation [1]. The
hypothesis is supported by substantive epidemiological
data. For example, one case–control study of 150 ovar-
ian cancer patients under the age of 50 years demon-
strated that the risk of ovarian cancer decreased with
increasing numbers of live births, increasing numbers
Keywords
apoptosis; G protein; GnRH; gonadotropin-
releasing hormone; growth factor; invasion;
MAPK; migration; ovarian cancer;
proliferation
Correspondence
P. C. K. Leung, Department of Obstetrics
and Gynecology, University of British
Columbia, 2H30, 4490 Oak Street,
Vancouver, BC, Canada V6H 3V5
Fax: +1 604 875 2717

ovarian cancer cell migration ⁄ invasion have started to emerge. In this mini-
review, we summarize the current understanding of the antiproliferative
actions of GnRH analogs, as well as the recent observations of GnRH
effects on ovarian cancer cell apoptosis and motogenesis. The molecular
mechanisms that mediate GnRH actions and the clinical applications of
GnRH analogs in ovarian cancer patients are also discussed.
Abbreviations
AP-1, activator protein-1; EGF, epidermal growth factor; EGFR, epidermal growth factor receptor; ERK, extracellular signal-regulated kinase;
GnRH, gonadotropin-releasing hormone; GPCR, G-protein-coupled receptor; IGF-I, insulin-like growth factor-I; JNK, c-Jun N-terminal kinase;
MAPK, mitogen-activated protein kinase; MEK, mitogen-activated protein kinase kinase; MMP, matrix metalloproteinase; NF-jB, nuclear
factor kappa B; OSE, ovarian surface epithelium; PKC, protein kinase C; PLC, phospholipase C; PP2A, protein phosphatase 2A; PTP,
phosphotyrosine phosphatase; PTX, pertussis toxin; TIMP, tissue inhibitor of metalloproteinases.
5496 FEBS Journal 275 (2008) 5496–5511 ª 2008 The Authors Journal compilation ª 2008 FEBS
of incomplete pregnancies, and the use of oral contra-
ceptives [2]. Another prevailing hypothesis addressing
the development of ovarian cancer was proposed by
Cramer and Welch in 1983. Their ‘gonadotropin the-
ory’ proposed that excessive gonadotropin stimulation
contributes to ovarian carcinogenesis [3]. The risk of
ovarian cancer increases during the perimenopausal
period, when serum gonadotropin levels peak and
thereafter remain elevated [4,5]. Moreover, only 10–
15% of tumors appear in premenopausal women [6].
Likewise, polycystic ovary syndrome patients (with
high luteinizing hormone levels) are more prone to
ovarian cancer [7]. Epidemiologic evidence supports the
idea that pregnancies, breast feeding, and oral contra-
ceptive use, which suppress pituitary gonadotropin
secretion, reduce the risk of ovarian cancer [8–11].
Experimentally, expression of gonadotropin receptors

presence of GnRH receptors in various established
ovarian cancer cell lines, including BG-1, OVCAR-3,
SKOV-3, EFO-21 and EFO-27 (Table 1) [20,26–31].
The level of GnRH receptor expression in the ovarian
cancer cell lines was about 10-fold lower than that in
pituitary aT3 cells [20].
The extremely short half-life of hypothalamic GnRH
makes it an unlikely candidate to act on the ovary via
the systemic circulation and suggests the existence of a
local source of GnRH in ovarian cancer cells. Indeed,
our group and others have detected GnRH-I mRNA
in normal OSE and immortalized OSE cells, as well as
in primary cultures of ovarian tumors and ovarian car-
cinoma cell lines such as EFO-21, EFO-27, CaOV-3,
OVACR-3 and SKOV-3 [32,33]. Similarly, GnRH-II
mRNA has been detected in normal and neoplastic
OSE cell lines and primary cultures of ovarian carcino-
mas [28]. GnRH-like immunoreactivity was detected in
conditioned media [34] and cell lysates [21] from ovar-
ian cancer cell lines. The latter possessed bioactivity
comparable to that of authentic GnRH, as it stimu-
lated luteinizing hormone release from rat pituitary
[21]. Incubation of ES-2 ovarian cancer cells in vitro
with a GnRH-I antibody inhibited cell proliferation in
a time- and dose-dependent manner [34], whereas
Emons reported a significant increase in EFO-21 and
EFO-27 ovarian cancer cell proliferation after GnRH-I
antiserum treatment [35]. Despite this discrepancy,
these studies provide direct evidence for the endo-
genous secretion of bioactive GnRH as an autocrine

+, positive; ), negative. Expression of GnRH receptors is based on reports published by individual groups.
Reference GnRH analogs Dose Cell line R-I R-II Action
[31] GnRH-I antagonist cetrorelix 10
)8
–10
)5
M OV-1063 + ND Antiproliferation
GnRH-I agonist triptorelin 10
)8
–10
)5
M
[44] GnRH-I agonist triptorelin 10
)7
–10
)5
M OVCAR-3 + ND Antiproliferation and cell cycle
arrest
SKOV-3 + ND
[30] GnRH-I agonist triptorelin 10
)5
M EFO-21 + + Antiproliferation
GnRH-I antagonist cetrorelix, Hoe-013 10
)11
–10
)5
M EFO-27 + ) Antiproliferation for EFO-21 but not
EFO-27
[32] GnRH-I agonist [
D-Ala6]GnRH 10

)
[28] GnRH-I agonist [
D-Ala6]GnRH 10
)9
–10
)7
M IOSE29, IOSE28-EC + ND Antiproliferation
[46] GnRH-I antagonist cetrorelix 10
)9
–10
)5
M HTOA + ND Antiproliferation and cell cycle
arrest (10
)9
,10
)5
M), apoptosis
(10
)5
M)
[43] GnRH-I agonist triptorelin 10
)9
–10
)7
M EFO-21 + + Antiproliferation and cell
cycle arrest
EFO-27 + )
[37] GnRH-I agonist triptorelin 10
)5
M EFO-21 + + Triptorelin: antiproliferation for

[127] GnRH-I agonist triptorelin 10
)11
–10
)5
M EFO-21 + + Suppression of
17b-estradiol-induced EFO-21 and
OVCAR-3 cell proliferation, but no
effect on SKOV-3
OVCAR-3 + +
SKOV-3 ) +
[57] GnRH-II agonist
D-Arg(6)-Azagly(10)-NH
2
10
)7
M OVCAR-3 + ND Antiproliferation and apoptosis
[54] GnRH-I agonist leuprolide 10
)6
M CaOV-3 + ND Protection against DOX-induced
apoptosis
SKOV-3 + ND
[50] GnRH-I antagonist cetrorelix 10
)8
–10
)6
M CaOV-3 + ND Apoptosis
SKOV-3 + ND
[42] GnRH-II agonist
D-Arg(6)-Azagly(10)-NH
2

[64] GnRH-I agonist triptorelin 10
)10
–10
)7
M OVCAR-3 + ND Induction of OVCAR-3 invasion
(10
)10
–10
)8
M), suppression of
SKOV-3 invasion at 10
)8
and
10
)7
M
GnRH-II agonist D-Arg(6)-Azagly(10)-NH
2
SKOV-3 + ND
W K. So et al. GnRH and ovarian cancer
FEBS Journal 275 (2008) 5496–5511 ª 2008 The Authors Journal compilation ª 2008 FEBS 5499
cell line OVCAR-3. Significant inhibition was detected
as early as 2 days after treatment [36]. Interestingly,
GnRH-I antagonists consistently act like agonists and
inhibit cell proliferation in various cell lines (Table 2).
GnRH-I antagonists were reported to be more potent
than equimolar concentrations of agonists in inhibiting
ovarian cancer cell growth [29,37]. This phenomenon
was also observed in endometrial [38], prostate [39]
and breast cancers [40], suggesting that the dichotomy

tate cancer apoptosis [48]. In ovarian cancer cells, a
high concentration (10
)5
m) of GnRH agonist has
been reported to induce tumor necrosis factor-a secre-
tion, interchromosomal DNA fragmentation, and a
marginal apoptotic effect [49]. An equimolar concen-
tration of the GnRH-I antagonist cetrorelix induced
apoptosis by upregulating p53 and p21 protein levels,
whereas concentrations as low as 10
)9
m resulted in
antiproliferative effects [46]. Recently, apoptosis was
shown to be induced by a low concentration of cetror-
elix in ovarian cancers [50]. We also observed DNA
fragmentation after prolonged (6 days) low-dose
GnRH-I agonist treatment [36]. In most studies, how-
ever, apoptosis was induced only when ovarian cancer
cells were treated with GnRH-I analogs at relatively
high concentrations or for a prolonged time. Although
Fas and FasL were detected in the majority of ovarian
carcinomas and ovarian cancer cell lines [51,52], and
GnRH agonists such as buserelin dose-dependently
induced FasL expression in ovarian cancer cells [52], a
causative linkage between Fas ⁄ FasL and the antipro-
liferative action of GnRH has not been established.
Indeed, there is no consensus about the proapoptotic
role of GnRH. The antiproliferative effect of GnRH
has been mainly attributed to the cytostatic action of
GnRH rather than induction of apoptosis. GnRH-I

Reference Drug Patients CR PR SD
[107] Leuprolide acetate 18 0 4 2
[108] Leuprolide acetate 5 1 3 1
[109] Leuprolide acetate 25 0 1 15
[110] Leuprolide acetate 32 0 4 5
[111] Leuprolide acetate 32 1 2 4
[112] Leuprolide acetate 37 0 0 4
[113] Leuprolide acetate 12 0 1 3
[114] Triptorelin 41 0 6 5
[115] Triptorelin 19 0 11 0
[116] Triptorelin 20 0 0 14
[117] Triptorelin 40 0 0 1
[118] Triptorelin 14 0 0 8
[106] Triptorelin 68 0 0 11
[119] Goserelin 23 0 4 7
[120] Goserelin 30 0 2 5
GnRH and ovarian cancer W K. So et al.
5500 FEBS Journal 275 (2008) 5496–5511 ª 2008 The Authors Journal compilation ª 2008 FEBS
demonstrated in nude mice bearing ovarian cancer cell
xenografts [58].
In contrast to the relatively large number of studies
on GnRH actions such as antiproliferative and apop-
totic ⁄ antiapoptotic effects, reports of GnRH influences
on other parameters of ovarian cancer progression,
such as tumorigenic or metastatic processes, are lim-
ited. Spread of ovarian cancer beyond the ovaries to
the peritoneal cavity leads to later staging of the dis-
ease and poor prognosis. The fact that a high propor-
tion of advanced-stage (stages III and IV) ovarian
carcinomas express GnRH receptor mRNA and

GnRH-I agonists and antagonists have been reported
to inhibit the migration and invasion of prostate
cancer, breast cancer and epidermoid carcinoma cells
[65–67]. Also, breast cancer cell invasiveness was sup-
pressed in vitro by both GnRH-I and GnRH-II [67].
Signaling and mechanism of GnRH
action in ovarian cancer cells
As a member of the serpentine receptor family, the
GnRH receptor transmits its signals mainly through
heterotrimeric G-proteins (GTP-binding proteins).
GnRH-I agonist/
antagonist
PTP
GnRH-I
receptor
β
β
γ
γ
EGFR
Expression
JNK
G α
α
i
Apoptosis
NF κ
κ
B
NF κ

Cell cycle
A
D C
B
E
F
G
Shc
Fig. 1. GnRH-I signaling in ovarian cancer
cells. (A) Through G
ai
, GnRH-I analogs acti-
vate PTP to dephosphorylate EGFR and
abolish EGF-induced ERK activation, c-fos
expression and proliferation. (B) G
bc
subunit
activates ERK and mediates GnRH-I-induced
growth inhibition. (C) GnRH-I activates ERK
through a PKC-dependent or PKC-indepen-
dent pathway to inhibit proliferation. (D)
GnRH-I activates JNK, which increases AP-1
activity and JunD–DNA binding to extend
the cell cycle. (E) GnRH-I suppresses apop-
tosis through activation of PP2A. (F) GnRH-I
stimulates NF-jB activity and nuclear trans-
location to protect ovarian cancer cells from
apoptosis. (G) GnRH-I acts through Gaito
counteract forskolin (FK)-induced cAMP. The
presence of a functional GnRH-II receptor

activates
membrane-associated phospholipase C (PLC), which
hydrolyzes phosphoinositides to generate the second
messengers inositol 1,4,5-triphosphate and diacylglyc-
erol, resulting in intracellular Ca
2+
mobilization and
protein kinase C (PKC) activation. Moreover, G
aq
-
activated PKC can activate MAPKs, including JNK,
ERK and p38 MAPK [68,69]. It is well established
that the GnRH receptor interacts with multiple G-pro-
teins, and that specificity is cell context dependent [68].
In hypothalamic neurons, the GnRH receptor interacts
with G
aq
,G
as
and G
ai
[70]. In pituitary gonadotropes,
GnRH preferentially or exclusively stimulates G
aq
[71].
However, G
ai
has been shown to mediate GnRH
receptor signaling in tumor cells such as ovarian
cancer [50,72,73], endometrial cancer [72,73] and pros-

ai
is selectively recognized and activated by
GnRH-II in order to regulate cell proliferation and
apoptosis. This kind of conformational preference may
be a result of cell context, including cell type and prior
exposure to other hormones [75]. Concrete evidence
for this specificity has been generated for the Xenopus
GnRH receptor: activation of PKC, which phosphory-
lates the C-terminus of the receptor, led to a marked
increase in GnRH-II binding to the Xenopus GnRH-I
receptor, but had no effect on GnRH-I binding [75].
This theory could resolve questions regarding the
Proliferation
Elk-1
p38
Apoptosis
Migration/
invasion
GnRHII
GnRH-I receptor
G α
α
i
PKC
EGFR
P
ERK1/2
MEK
c-fos expression
EGF

observed in tumor cells than in pituitary gonadotropes
[75], why GnRH antagonists act like agonists in cancer
cells (Table 2), and why GnRH-II is observed to be
more potent than GnRH-I in inhibiting cancer cell
proliferation through G
ai
, but less potent in stimulat-
ing G
aq
-mediated gonadotropin secretion in pituitary
gonadotropes [37,77].
At present, the identity of the GnRH receptor(s)
that mediate the antiproliferative actions of GnRH in
tumor cells and the agonistic effects of GnRH antago-
nists in cancer cells is still controversial. Grundker and
co-workers have compared the GnRH responsiveness
of SKOV-3 and EFO-27 ovarian cancer cells, and pro-
posed that their responsiveness correlates with the
expression of GnRH receptors. Accordingly, EFO-27
cells expressing GnRH-I receptor but not GnRH-II
receptor responded to the GnRH-I agonist triptorelin
but not to antagonists, even at high concentrations
(10
)5
m) [27,30,78]. By contrast, in SKOV-3 cells,
which are reportedly GnRH-I receptor-negative but
GnRH-II receptor-positive, both the GnRH-I antago-
nist cetrorelix and GnRH-II, but not triptorelin, inhib-
ited cell growth [27,37] or EGF-induced c-fos
expression [78]. Cell lines expressing both GnRH-I

ai
and ⁄ or G
aq
have been detected in GnRH-I
receptor-expressing ovarian cancer cell lines and surgi-
cally removed ovarian carcinomas [72,73]. GnRH-I
receptor has been shown, by disuccinimidyl suberate
cross-linking experiments, to interact physically with
G
ai
and G
aq
[72]. Functionally, it has been suggested
that GnRH-I receptor couples with G
ai
, which is com-
mon in tumor cells [50,72–74]. G
ai
is pertussis toxin
(PTX)-sensitive and is not affected by cholera toxin.
PTX induced ADP-ribosylation of the a-subunit in the
GnRH-I receptor-positive tumor cell membrane
[50,72–74] and thus impaired GnRH-I receptor-linked
cellular events, including GnRH-induced phosphatase
activity [50,72,73], apoptosis [50], and antiproliferative
actions [72,74]. Conversely, incubation with GnRH
agonists substantially antagonized the PTX-catalyzed
ADP-ribosylation of G
ai
[72–74]. Furthermore, G

deplete PKC) or by depletion of Ca
2+
, whereas the
GnRH-I agonist activated MAPK via a PKC-indepen-
dent mechanism to inhibit growth of CaOV-3 ovarian
cancer cells [81]. However, evidence supporting PKC
involvement in GnRH actions in tumor cells or
extrapituitary tissues is available. Cetrorelix stimulated
PKC activity in DU-145 prostate cancer cells, resulting
in an increase in phosphorylation of the PKC substrate
MARCKS [82]. By activating PKC, GnRH analogs
inhibited the EGF receptor (EGFR) signal and the
growth of prostate cancer xenografts in athymic mice
[83] and cell invasion in vitro [82]. Essentially, prostate
W K. So et al. GnRH and ovarian cancer
FEBS Journal 275 (2008) 5496–5511 ª 2008 The Authors Journal compilation ª 2008 FEBS 5503
cancer cells carrying a mutated EGFR that lacks the
target site for PKC are resistant to GnRH-induced
in vivo and in vitro growth inhibition [82,83]. Our labo-
ratory has recently demonstrated that 12-O-tetradeca-
noyl phorbol-13-acetate (a PKC-activating phorbol
ester) can mimic the effects of GnRH-I and GnRH-II
in stimulating ERK1 ⁄ 2 phosphorylation and antipro-
liferation in ovarian cancer cells. Furthermore, the
effects of GnRH were abolished by pretreatment with
the PKC inhibitor GF109203X [41] (Figs 1C and 2B).
By analogy, the PKC inhibitor calphostin C and the
activator 12-O-tetradecanoyl phorbol-13-acetate can
block and mimic, respectively, the antiproliferative
action of the GnRH agonist buserelin on surgically

to mediate the antiproliferative action of GnRH and
such growth inhibition could be reversed by the mito-
gen-activated protein kinase kinase (MEK) inhibitor
PD98059 [81]. The dual roles of ERK in mediating
mitogenic effects (by growth factors) and antiprolifera-
tive effects (by GnRH) seem contradictory. Paradoxical
actions of ERK have also been reported in PC-12 cells:
transient activation induced by EGF led to prolifera-
tion, and nerve growth factor-induced prolonged ERK
activation caused differentiation and cessation of prolif-
eration [90]. It has been suggested that the duration of
ERK activation is important in determining its actions
and thus the resultant cell fate [90].
In addition to ERK, JNK was activated by triptore-
lin through induction of c-jun mRNA expression and
protein phosphorylation [91], in a manner that was
independent of PLC and PKC [92]. The same group
further demonstrated that triptorelin treatment
increased activator protein-1 (AP-1) activity and
JunD–DNA binding, and extended the cell cycle [43]
(Fig. 1D). As JNK and c-jun are implicated in cell
cycle regulation [93], it is logical to hypothesize that
the JNK–c-jun–AP-1 pathway mediates the GnRH-
induced antiproliferative effect. This pathway may act
in concert with NF-jB, as it was shown to protect
tumor cells from doxorubicin-induced apoptosis in the
same system. JunD is proposed to act as a modulator
of cell proliferation and to cooperate with the anti-
apoptotic and antiproliferative functions of GnRH.
However, further investigation is necessary to resolve

GnRH agonists [50,54,72,97–100], suggesting that
GnRH-I increased the turnover rate of protein phos-
phorylation ⁄ dephosphorylation and that EGFR is a
target of the dephosphorylation activity [72,96]. As a
result, EGFR phosphorylation [72] and the down-
stream signaling and mitogenic effects of EGF were
abrogated, including EGF-induced MAPK activation
[94], immediate early gene c-fos expression [78] and
GnRH and ovarian cancer W K. So et al.
5504 FEBS Journal 275 (2008) 5496–5511 ª 2008 The Authors Journal compilation ª 2008 FEBS
proliferation [92]. Downregulation of receptors for
EGF and ⁄ or insulin-like growth factor-I (IGF-I) by
GnRH antagonist [101] and in ovarian cancer-xeno-
grafted nude mice have been reported [31,102]. Inter-
ference of growth factor signaling by GnRH analogs
has also been demonstrated in prostate cancer cells.
GnRH-I analogs abrogated the mitogenic effects of
EGF and IGF-I and inhibited prostate cancer growth
[103,104] by reducing expression of their receptors
[103–105], as well as by inhibiting EGF- and IGF-I-
induced receptor phosphorylation [103,104] and c-fos
expression. GnRH-II agonist was reported to act in a
similar fashion, i.e. enhancing PTP activity and thus
reducing EGF-induced EGFR phosphorylation,
MAPK activation and c-fos expression [79] (Fig. 2A).
Moreover, GnRH-activated phosphatase activity has
also been implicated in its antiapoptotic function.
Doxorubicin decreased the activity of a crucial
phosphatase in apoptosis control (PP2A), and induced
ovarian cancer cell apoptosis. Cotreatment with the

involved only a limited number of patients.
Three trials have been completed that compared the
use of platinum-based chemotherapy alone or in com-
bination with a GnRH agonist as first-line therapy for
ovarian cancer [121–123]. A prospective randomized
double-blind trial enrolled 135 patients with stage III
or IV epithelial ovarian carcinoma, and showed that
suppression of endogenous gonadotropins by conven-
tional doses of the GnRH agonist triptoreli n produces
no relevant beneficial effects in patients with advanced
ovarian carcinoma who receive standard surgical cyto-
reduction and standard platinum-based chemotherapy
[121]. In the other two studies, patients received carbo-
platin-containing polychemotherapy and cisplatin alone
or chemotherapy plus triptorelin, but no significant dif-
ferences were seen in terms of response, survival and
time to progression [122,123]. The ineffectiveness of the
GnRH agonist in combination with chemotherapy is
postulated to be due to the neutralization of its direct
antiproliferative effects by its antiapoptotic activity, as
demonstrated by the in vitro data [53,54,124].
In vitro data demonstrated that antagonists provided
a greater inhibitory effect on ovarian cancer prolifera-
tion than agonists [29]. Clinically, as GnRH-I antago-
nists do not possess intrinsic gonadotropic activity, the
initial ‘flare-up’ phenomenon, which is common in
agonist treatment, can be avoided. This makes antago-
nists better tolerated and capable of blocking gonado-
tropin secretion within a short time frame [125]. A
clinical trial of the GnRH antagonist cetrorelix was

ing therapeutic approach for ovarian cancer. Elucida-
tion of the efficacy and modes of actions of GnRH-I
and GnRH-II, as well as their interactions with growth
factors that are known to be important in ovarian
cancer progression, is undoubtedly warranted.
Acknowledgements
P.C.K.L. is the recipient of a Child & Family Research
Institute Distinguished Scholar Award. W.K.S., J.C.C.
and S.L.P. were recipients of graduate studentship
awards from The Interdisciplinary Women’s Repro-
ductive Health Research Training Program.
References
1 Fathalla MF (1971) Incessant ovulation – a factor in
ovarian neoplasia? Lancet 2, 163.
2 Casagrande JT, Louie EW, Pike MC, Roy S, Ross RK
& Henderson BE (1979) ‘Incessant ovulation’ and
ovarian cancer. Lancet 2, 170–173.
3 Cramer DW & Welch WR (1983) Determinants of
ovarian cancer risk. II. Inferences regarding pathogene-
sis. J Natl Cancer Inst 71, 717–721.
4 Chakravarti S, Collins WP, Forecast JD, Newton JR,
Oram DH & Studd JW (1976) Hormonal profiles after
the menopause. Br Med J 2, 784–787.
5 Scaglia H, Medina M, Pinto-Ferreira AL, Vazques G,
Gual C & Perez-Palacios G (1976) Pituitary LH and
FSH secretion and responsiveness in women of old
age. Acta Endocrinol (Copenh) 81, 673–679.
6 Sell A, Bertelsen K, Andersen JE, Stroyer I & Panduro
J (1990) Randomized study of whole-abdomen irradia-
tion versus pelvic irradiation plus cyclophosphamide in

14 Choi KC, Kang SK, Tai CJ, Auersperg N & Leung
PC (2002) Follicle-stimulating hormone activates mito-
gen-activated protein kinase in preneoplastic and neo-
plastic ovarian surface epithelial cells. J Clin Endocrinol
Metab 87, 2245–2253.
15 Choi JH, Choi KC, Auersperg N & Leung PC (2005)
Gonadotropins upregulate the epidermal growth factor
receptor through activation of mitogen-activated pro-
tein kinases and phosphatidyl-inositol-3-kinase in
human ovarian surface epithelial cells. Endocr Relat
Cancer 12, 407–421.
16 Choi JH, Choi KC, Auersperg N & Leung PC (2004)
Overexpression of follicle-stimulating hormone receptor
activates oncogenic pathways in preneoplastic ovarian
surface epithelial cells. J Clin Endocrinol Metab 89,
5508–5516.
17 Choi JH, Choi KC, Auersperg N & Leung PC (2006)
Gonadotropins activate proteolysis and increase inva-
sion through protein kinase A and phosphatidylinositol
3-kinase pathways in human epithelial ovarian cancer
cells. Cancer Res 66, 3912–3920.
18 Limonta P, Moretti RM, Marelli MM & Motta M
(2003) The biology of gonadotropin hormone-releasing
hormone: role in the control of tumor growth and
progression in humans. Front Neuroendocrinol 24
,
279–295.
19 Peterson CM, Jolles CJ, Carrell DT, Straight RC,
Jones KP, Poulson AM Jr & Hatasaka HH (1994)
GnRH agonist therapy in human ovarian epithelial

T (1994) Gonadotropin-releasing hormone receptor in
gynecologic tumors. Frequent expression in adenocarci-
noma histologic types. Cancer 74, 2555–2561.
26 Yin H, Cheng KW, Hwa HL, Peng C, Auersperg N &
Leung PC (1998) Expression of the messenger RNA
for gonadotropin-releasing hormone and its receptor in
human cancer cell lines. Life Sci 62, 2015–2023.
27 Grundker C, Schlotawa L, Viereck V, Eicke N,
Horst A, Kairies B & Emons G (2004) Antiprolifera-
tive effects of the GnRH antagonist cetrorelix and of
GnRH-II on human endometrial and ovarian cancer
cells are not mediated through the GnRH type I recep-
tor. Eur J Endocrinol 151, 141–149.
28 Choi KC, Auersperg N & Leung PC (2001) Expression
and antiproliferative effect of a second form of gona-
dotropin-releasing hormone in normal and neoplastic
ovarian surface epithelial cells. J Clin Endocrinol Metab
86, 5075–5078.
29 Yano T, Pinski J, Radulovic S & Schally AV (1994)
Inhibition of human epithelial ovarian cancer cell
growth in vitro by agonistic and antagonistic analogues
of luteinizing hormone-releasing hormone. Proc Natl
Acad Sci USA 91, 1701–1705.
30 Emons G, Ortmann O, Becker M, Irmer G, Springer
B, Laun R, Holzel F, Schulz KD & Schally AV (1993)
High affinity binding and direct antiproliferative effects
of LHRH analogues in human ovarian cancer cell
lines. Cancer Res 53, 5439–5446.
31 Yano T, Pinski J, Halmos G, Szepeshazi K, Groot K
& Schally AV (1994) Inhibition of growth of OV-1063

tumor cell proliferation. J Clin Endocrinol Metab 87,
1427–1430.
38 Emons G, Schroder B, Ortmann O, Westphalen S,
Schulz KD & Schally AV (1993) High affinity binding
and direct antiproliferative effects of luteinizing hor-
mone-releasing hormone analogs in human endometrial
cancer cell lines. J Clin Endocrinol Metab 77, 1458–
1464.
39 Castellon E, Clementi M, Hitschfeld C, Sanchez C,
Benitez D, Saenz L, Contreras H & Huidobro C (2006)
Effect of leuprolide and cetrorelix on cell growth,
apoptosis, and GnRH receptor expression in primary
cell cultures from human prostate carcinoma. Cancer
Invest 24, 261–268.
40 Yano T, Korkut E, Pinski J, Szepeshazi K, Milovano-
vic S, Groot K, Clarke R, Comaru-Schally AM & Sch-
ally AV (1992) Inhibition of growth of MCF-7 MIII
human breast carcinoma in nude mice by treatment
with agonists or antagonists of LH-RH. Breast Cancer
Res Treat 21, 35–45.
41 Kim KY, Choi KC, Auersperg N & Leung PC (2006)
Mechanism of gonadotropin-releasing hormone
(GnRH)-I and -II-induced cell growth inhibition in
ovarian cancer cells: role of the GnRH-I receptor and
protein kinase C pathway. Endocr Relat Cancer 13,
211–220.
42 Kim KY, Choi KC, Park SH, Auersperg N & Leung
PC (2005) Extracellular signal-regulated protein kinase,
but not c-Jun N-terminal kinase, is activated by type II
gonadotropin-releasing hormone involved in the inhibi-

kinase, protein kinase B, and extracellular signal-regu-
lated kinase pathways. Cancer Res 64, 5736–5744.
49 Motomura S (1998) Induction of apoptosis in ovarian
carcinoma cell line by gonadotropin-releasing hormone
agonist. Kurume Med J 45, 27–32.
50 Imai A, Sugiyama M, Furui T & Tamaya T (2006) Gi
protein-mediated translocation of serine ⁄ threonine
phosphatase to the plasma membrane and apoptosis of
ovarian cancer cell in response to gonadotropin-releas-
ing hormone antagonist cetrorelix. J Obstet Gynaecol
26, 37–41.
51 Imai A, Horibe S, Takagi A, Ohno T & Tamaya T
(1997) Frequent expression of Fas in gonadotropin-
releasing hormone receptor-bearing tumors. Eur J
Obstet Gynecol Reprod Biol 74, 73–78.
52 Imai A, Takagi A, Horibe S, Takagi H & Tamaya T
(1998) Evidence for tight coupling of gonadotropin-
releasing hormone receptor to stimulated Fas ligand
expression in reproductive tract tumors: possible mech-
anism for hormonal control of apoptotic cell death.
J Clin Endocrinol Metab 83, 427–431.
53 Grundker C, Schulz K, Gunthert AR & Emons G (2000)
Luteinizing hormone-releasing hormone induces nuclear
factor kappaB-activation and inhibits apoptosis in ovar-
ian cancer cells. J Clin Endocrinol Metab 85, 3815–3820.
54 Sugiyama M, Imai A, Furui T & Tamaya T (2005)
Gonadotropin-releasing hormone retards doxorubicin-
induced apoptosis and serine ⁄ threonine phosphatase
inhibition in ovarian cancer cells. Oncol Rep 13, 813–
817.

stromal cells in vitro. J Clin Endocrinol Metab 88,
3806–3815.
61 Chou CS, Zhu H, MacCalman CD & Leung PC (2003)
Regulatory effects of gonadotropin-releasing hormone
(GnRH) I and GnRH II on the levels of matrix metal-
loproteinase (MMP)-2, MMP-9, and tissue inhibitor of
metalloproteinases-1 in primary cultures of human
extravillous cytotrophoblasts. J Clin Endocrinol Metab
88, 4781–4790.
62 Chou CS, Zhu H, Shalev E, MacCalman CD & Leung
PC (2002) The effects of gonadotropin-releasing hor-
mone (GnRH) I and GnRH II on the urokinase-type
plasminogen activator ⁄ plasminogen activator inhibitor
system in human extravillous cytotrophoblasts in vitro.
J Clin Endocrinol Metab 87, 5594–5603.
63 Cheung LW, Leung PC & Wong AS (2006) Gonado-
tropin-releasing hormone promotes ovarian cancer cell
invasiveness through c-Jun NH2-terminal kinase-medi-
ated activation of matrix metalloproteinase (MMP)-2
and MMP-9. Cancer Res 66, 10902–10910.
64 Chen CL, Cheung LW, Lau MT, Choi JH, Auersperg
N, Wang HS, Wong AS & Leung PC (2007) Differen-
tial role of gonadotropin-releasing hormone on human
GnRH and ovarian cancer W K. So et al.
5508 FEBS Journal 275 (2008) 5496–5511 ª 2008 The Authors Journal compilation ª 2008 FEBS
ovarian epithelial cancer cell invasion. Endocrine 31,
311–320.
65 Dondi D, Festuccia C, Piccolella M, Bologna M &
Motta M (2006) GnRH agonists and antagonists
decrease the metastatic progression of human prostate

72 Grundker C, Volker P & Emons G (2001) Antiprolifera-
tive signaling of luteinizing hormone-releasing hormone
in human endometrial and ovarian cancer cells through
G protein alpha(I)-mediated activation of phosphotyro-
sine phosphatase. Endocrinology 142, 2369–2380.
73 Imai A, Takagi H, Horibe S, Fuseya T & Tamaya T
(1996) Coupling of gonadotropin-releasing hormone
receptor to Gi protein in human reproductive tract
tumors. J Clin Endocrinol Metab 81, 3249–3253.
74 Limonta P, Moretti RM, Marelli MM, Dondi D,
Parenti M & Motta M (1999) The luteinizing
hormone-releasing hormone receptor in human
prostate cancer cells: messenger ribonucleic acid
expression, molecular size, and signal transduction
pathway. Endocrinology 140, 5250–5256.
75 Millar RP & Pawson AJ (2004) Outside-in and inside-
out signaling: the new concept that selectivity of ligand
binding at the gonadotropin-releasing hormone recep-
tor is modulated by the intracellular environment.
Endocrinology 145, 3590–3593.
76 Ghanouni P, Gryczynski Z, Steenhuis JJ, Lee TW,
Farrens DL, Lakowicz JR & Kobilka BK (2001)
Functionally different agonists induce distinct
conformations in the G protein coupling domain of the
beta 2 adrenergic receptor. J Biol Chem 276, 24433–
24436.
77 Millar RP, Pawson AJ, Morgan K, Rissman EF &
Lu ZL (2008) Diversity of actions of GnRHs mediated
by ligand-induced selective signaling. Front Neuroendo-
crinol 29, 17–35.

attenuating epidermal growth factor receptor signaling.
Clin Cancer Res 8, 1251–1257.
84 Yamamoto H, Sato H, Shibata S, Murata M, Fukuda
J & Tanaka T (2001) Involvement of annexin V in the
antiproliferative effect of GnRH agonist on cultured
human uterine leiomyoma cells. Mol Hum Reprod 7,
169–173.
85 Kang SK, Tai CJ, Nathwani PS, Choi KC & Leung
PC (2001) Stimulation of mitogen-activated protein
kinase by gonadotropin-releasing hormone in human
granulosa-luteal cells. Endocrinology 142, 671–679.
86 Weck J, Fallest PC, Pitt LK & Shupnik MA (1998)
Differential gonadotropin-releasing hormone stimula-
tion of rat luteinizing hormone subunit gene transcrip-
tion by calcium influx and mitogen-activated protein
W K. So et al. GnRH and ovarian cancer
FEBS Journal 275 (2008) 5496–5511 ª 2008 The Authors Journal compilation ª 2008 FEBS 5509
kinase-signaling pathways. Mol Endocrinol 12, 451–
457.
87 Yokoi T, Ohmichi M, Tasaka K, Kimura A, Kanda Y,
Hayakawa J, Tahara M, Hisamoto K, Kurachi H &
Murata Y (2000) Activation of the luteinizing hormone
beta promoter by gonadotropin-releasing hormone
requires c-Jun NH2-terminal protein kinase. J Biol
Chem 275, 21639–21647.
88 Bonfil D, Chuderland D, Kraus S, Shahbazian D,
Friedberg I, Seger R & Naor Z (2004) Extracellular
signal-regulated kinase, Jun N-terminal kinase, p38,
and c-Src are involved in gonadotropin-releasing hor-
mone-stimulated activity of the glycoprotein hormone

96 Lee MT, Liebow C, Kamer AR & Schally AV (1991)
Effects of epidermal growth factor and analogues of
luteinizing hormone-releasing hormone and somato-
statin on phosphorylation and dephosphorylation of
tyrosine residues of specific protein substrates in vari-
ous tumors. Proc Natl Acad Sci USA 88, 1656–1660.
97 Imai A, Furui T, Tamaya T & Mills GB (2000) A gon-
adotropin-releasing hormone-responsive phosphatase
hydrolyses lysophosphatidic acid within the plasma
membrane of ovarian cancer cells. J Clin Endocrinol
Metab 85, 3370–3375.
98 Imai A, Horibe S, Takagi A & Tamaya T (1997) Gi pro-
tein activation of gonadotropin-releasing hormone-med-
iated protein dephosphorylation in human endometrial
carcinoma. Am J Obstet Gynecol 176, 371–376.
99 Imai A, Takagi H, Furui T, Horibe S, Fuseya T &
Tamaya T (1996) Evidence for coupling of phosphoty-
rosine phosphatase to gonadotropin-releasing hormone
receptor in ovarian carcinoma membrane. Cancer 77,
132–137.
100 Sugiyama M, Imai A, Furui T & Tamaya T (2003)
Independent action of serine ⁄ threonine protein phos-
phatase in ovarian cancer plasma membrane and cyto-
sol during gonadotropin-releasing hormone
stimulation. Oncol Rep 10, 1885–1889.
101 Shirahige Y, Cook C, Pinski J, Halmos G, Nair R &
Schally AV (1994) Treatment with luteinizing hor-
mone-releasing hormone antagonist SB-75 decreases
levels of epidermal growth factor receptor and its
mRNA in OV-1063 human epithelial ovarian cancer

162.
107 Kavanagh JJ, Roberts W, Townsend P & Hewitt S
(1989) Leuprolide acetate in the treatment of refractory
or persistent epithelial ovarian cancer. J Clin Oncol 7,
115–118.
GnRH and ovarian cancer W K. So et al.
5510 FEBS Journal 275 (2008) 5496–5511 ª 2008 The Authors Journal compilation ª 2008 FEBS
108 Bruckner HW & Motwani BT (1989) Treatment of
advanced refractory ovarian carcinoma with a gonado-
tropin-releasing hormone analogue. Am J Obstet Gyne-
col 161, 1216–1218.
109 Miller DS, Brady MF & Barrett RJ (1992) A phase II
trial of leuprolide acetate in patients with advanced
epithelial ovarian carcinoma. A Gynecologic Oncology
Group study. Am J Clin Oncol 15, 125–128.
110 Marinaccio M, D’Addario V, Serrati A, Pinto V &
Cagnazzo G (1996) Leuprolide acetate as a salvage-
therapy in relapsed epithelial ovarian cancer. Eur J
Gynaecol Oncol 17, 286–288.
111 Paskeviciute L, Roed H & Engelholm S (2002) No
rules without exception: long-term complete remission
observed in a study using a LH-RH agonist in plati-
num-refractory ovarian cancer. Gynecol Oncol 86, 297–
301.
112 du BA, Meier W, Luck HJ, Emon G, Moebus V, Sch-
roeder W, Costa S, Bauknecht T, Olbricht S, Jackisch
C et al. (2002) Chemotherapy versus hormonal treat-
ment in platinum- and paclitaxel-refractory ovarian
cancer: a randomised trial of the German Arbeitsgeme-
inschaft Gynaekologische Onkologie (AGO) Study

Proctor M, Simmons D, Carmichael J & Harris AL
(1992) A phase II trial of goserelin (Zoladex) in
relapsed epithelial ovarian cancer. Br J Cancer 65,
621–623.
121 Emons G, Ortmann O, Teichert HM, Fassl H, Lohrs
U, Kullander S, Kauppila A, Ayalon D, Schally A &
Oberheuser F (1996) Luteinizing hormone-releasing
hormone agonist triptorelin in combination with cyto-
toxic chemotherapy in patients with advanced ovarian
carcinoma. A prospective double blind randomized
trial. Decapeptyl Ovarian Cancer Study Group. Cancer
78, 1452–1460.
122 Medl M, Peters-Engel C, Fuchs G & Leodolter S
(1993) Triptorelin (D-Trp-6-LHRH) in combination
with carboplatin-containing polychemotherapy for
advanced ovarian cancer: a pilot study. Anticancer Res
13, 2373–2376.
123 Falkson CI, Falkson HC & Falkson G (1996) Cisplatin
versus cisplatin plus D-Trp-6-LHRH in the treatment
of ovarian cancer: a pilot trial to investigate the effect
of the addition of a GnRH analogue to cisplatin.
Oncology 53, 313–317.
124 Emons G, Grundker C, Gunthert AR, Westphalen S,
Kavanagh J & Verschraegen C (2003) GnRH
antagonists in the treatment of gynecological and
breast cancers. Endocr Relat Cancer 10, 291–
299.
125 Felberbaum RE, Ludwig M & Diedrich K (2000) Clini-
cal application of GnRH-antagonists. Mol Cell Endo-
crinol