Contrasting effects of 17 beta-estradiol on the growth of human ovarian carcinoma cells in vitro and in vivo

Paradigm Shift: A Comprehensive Review of Ovarian Cancer Management in an Era of Advancements

Ovarian cancer (OC) is the female genital malignancy with the highest lethality. Patients present a poor prognosis mainly due to the late clinical presentation allied with the common acquisition of chemoresistance and a high rate of tumour recurrence. Effective screening, accurate diagnosis, and personalised multidisciplinary treatments are crucial for improving patients' survival and quality of life. This comprehensive narrative review aims to describe the current knowledge on the aetiology, prevention, diagnosis, and treatment of OC, highlighting the latest significant advancements and future directions. Traditionally, OC treatment involves the combination of cytoreductive surgery and platinum-based chemotherapy. Although more therapeutical approaches have been developed, the lack of established predictive biomarkers to guide disease management has led to only marginal improvements in progression-free survival (PFS) while patients face an increasing level of toxicity. Fortunately, because of a better overall understanding of ovarian tumourigenesis and advancements in the disease's (epi)genetic and molecular profiling, a paradigm shift has emerged with the identification of new disease biomarkers and the proposal of targeted therapeutic approaches to postpone disease recurrence and decrease side effects, while increasing patients' survival. Despite this progress, several challenges in disease management, including disease heterogeneity and drug resistance, still need to be overcome.

Tamoxifen use in recurrent ovarian cancer in a Chinese population: A 15 -year clinical experience in a tertiary referral center

Aim

To review the clinical use and the effectiveness of tamoxifen in patients with advanced or recurrent ovarian cancer.

Methods

A retrospective review of clinical records was conducted in patients who received tamoxifen for the treatment of ovarian cancer between 2002 and 2016. We reviewed the clinical setting that it was given, duration of use, patients' tolerability, clinical benefit and progression‐free survival. We also attempted to identify predictive markers for response.

Results

A total of 92 patients received tamoxifen during this 15‐year period. The patients received a median of 2.5 lines of chemotherapy before switching to tamoxifen, and they remained on tamoxifen for a median of 5.6 months (range 0–85 months), with 24 patients receiving it for more than 12 months. Seventy‐six patients continued on tamoxifen for more than 2 months. In this group, 75 patients had an evaluable response, either by CA 125 or clinically and clinical benefit rate (defined as complete, partial response and static disease) was seen in 42 patients (56%), with majority of patients having static disease. The median progression‐free survival was 5.3 months (95% confidence interval, 2.6–8.1). Tamoxifen was well tolerated. Hormone receptor status was not demonstrated to predict response.

Conclusion

Patients with advanced ovarian cancer who have failed previous lines of chemotherapy may achieve static disease with tamoxifen with minimal side effects. Tamoxifen may still have a role in the era of molecular target therapy.

Estrogen Signaling and Its Potential as a Target for Therapy in Ovarian Cancer

The estrogen receptor (ER) has functionality in selected ovarian cancer subtypes and represents a potential target for therapy. The majority (>80%) of high grade serous, low grade serous and endometrioid carcinomas and many granulosa cell tumors express ER-alpha (ERα), and these tumor types have demonstrated responses to endocrine therapy (tamoxifen and aromatase inhibitors) in multiple clinical studies. Biomarkers of responses to these drugs are actively being sought to help identify responsive cancers. Evidence for both pro-proliferative and pro-migratory roles for ERα has been obtained in model systems. ER-beta (ERβ) is generally considered to have a tumor suppressor role in ovarian cancer cells, being associated with the repression of cell growth and invasion. The differential expression of the specific ERβ isoforms may determine functionality within ovarian cancer cells. The more recently identified G protein-coupled receptor (GPER1; GPR30) has been shown to mediate both tumor-suppressive and tumor-promoting action in ovarian cancer cells, suggesting a more complex role. This review will summarize recent findings in this field.

Whole flaxseed diet alters estrogen metabolism to promote 2-methoxtestradiol-induced apoptosis in hen ovarian cancer

The study reported here demonstrates that a flaxseed-supplemented diet causes ovarian tumors in the laying hen to undergo apoptosis, resulting in a reduction of tumor burden, reducing the frequency and severity of ovarian cancer. We have previously shown in normal ovaries that flaxseed and its components down-regulate ERalpha and alter the expression of enzymes that metabolize estrogen. In this study, we analyzed the effects of the two main components of whole flaxseed, ligan and omega 3 fatty acids on estrogen metabolism and the estrogen receptor in ovarian tumors. ER alpha expression was up-regulated in the ovarian tumors and was not affected by diet. Liver CYP1A1 expression was significantly increased by the whole flaxseed diet with a corresponding increase in 2-methoxyestradiol plasma levels. We also observed increased p38 and ERK 1/2 MAPK activation in the ovary as well as an increase in apoptosis in the tumor epithelium. SMAD 7, a factor involved in the 2-methoxyestradiol-mediated apoptosis pathway was also up-regulated in tumors from the whole flaxseed diet group. 2-methoxyestradiol-induced antitumor effects were further validated by in human ovarian cancer cells. This study details the effect of flaxseed diet on estrogen metabolism and demonstrates the antiovarian cancer effects of 2-methoxyestradiol.

Expression of steroid receptor coactivator 3 in ovarian epithelial cancer is a poor prognostic factor and a marker for platinum resistance

BACKGROUND

Steroid receptor coactivator 3 (SRC3) is an important coactivator of a number of transcription factors and is associated with a poor outcome in numerous tumours. Steroid receptor coactivator 3 is amplified in 25% of epithelial ovarian cancers (EOCs) and its expression is higher in EOCs compared with non-malignant tissue. No data is currently available with regard to the expression of SRC-3 in EOC and its influence on outcome or the efficacy of treatment.

METHODS

Immunohistochemistry was performed for SRC3, oestrogen receptor-α, HER2, PAX2 and PAR6, and protein expression was quantified using automated quantitative immunofluorescence (AQUA) in 471 EOCs treated between 1991 and 2006 with cytoreductive surgery followed by first-line treatment platinum-based therapy, with or without a taxane.

RESULTS

Steroid receptor coactivator 3 expression was significantly associated with advanced stage and was an independent prognostic marker. High expression of SRC3 identified patients who have a significantly poorer survival with single-agent carboplatin chemotherapy, while with carboplatin/paclitaxel treatment such a difference was not seen.

CONCLUSION

Steroid receptor coactivator 3 is a poor prognostic factor in EOCs and appears to identify a population of patients who would benefit from the addition of taxanes to their chemotherapy regimen, due to intrinsic resistance to platinum therapy.

Exploiting MEK inhibitor-mediated activation of ERα for therapeutic intervention in ER-positive ovarian carcinoma

While the clinical benefit of MEK inhibitor (MEKi)-based therapy is well established in Raf mutant malignancies, its utility as a suppressor of hyperactive MAPK signaling in the absence of mutated Raf or Ras, is an area of ongoing research. MAPK activation is associated with loss of ERα expression and hormonal resistance in numerous malignancies. Herein, we demonstrate that MEKi induces a feedback response that results in ERα overexpression, phosphorylation and transcriptional activation of ER-regulated genes. Mechanistically, MEKi-mediated ERα overexpression is largely independent of erbB2 and AKT feedback activation, but is ERK-dependent. We subsequently exploit this phenomenon therapeutically by combining the ER-antagonist, fulvestrant with MEKi. This results in synergistic suppression of tumor growth, in vitro and potentiation of single agent activity in vivo in nude mice bearing xenografts. Thus, we demonstrate that exploiting adaptive feedback after MEKi can be used to sensitize ERα-positive tumors to hormonal therapy, and propose that this strategy may have broader clinical utility in ERα-positive ovarian carcinoma.

Tissue-specific pathways for estrogen regulation of ovarian cancer growth and metastasis

Menopausal estrogen (E2) replacement therapy increases the risk of estrogen receptor (ER)-positive epithelial ovarian cancers (EOC). Whether E2 is tumorigenic or promotes expansion of undiagnosed preexisting disease is unknown. To determine E2 effects on tumor promotion, we developed an intraperitoneal mouse xenograft model using ZsGreen fluorescent ER(-) 2008 and ER(+) PEO4 human EOC cells. Tumor growth was quantified by in vivo fluorescent imaging. In ER(+) tumors, E2 significantly increased size, induced progesterone receptors, and promoted lymph node metastasis, confirming that ERs are functional and foster aggressiveness. Laser-captured human EOC cells from ER(-) and ER(+) xenografted tumors were profiled for expression of E2-regulated genes. Three classes of E2-regulated EOC genes were defined, but <10% were shared with E2-regulated breast cancer genes. Because breast cancer selective ER modulators (SERM) are therapeutically ineffective in EOC, we suggest that our EOC-specific E2-regulated genes can assist pharmacologic discovery of ovarian-targeted SERM.

Aromatase expression in women's cancers

Estrogen has been positively linked to the pathogenesis and growth of three common women's cancers (breast, endometrium and ovary). A single gene encodes the key enzyme for estrogen biosynthesis named aromatase, inhibition of which effectively eliminates estrogen production in the entire body. Aromatase inhibitors successfully treat breast cancer, whereas their roles in endometrial and ovarian cancers are less dear. Ovary, testis, adipose tissue, skin, hypothalamus and placenta express aromatase normally, whereas breast, endometrial and ovarian cancers overexpress aromatase and produce local estrogen exerting paracrine and intracrine effects. Tissue specific promoters distributed over a 93 kilobase regulatory region upstream of a common coding region alternatively control aromatase expression. A distinct set of transcription factors regulates each promoter in a signaling pathway- and tissue-specific manner. In cancers ofbreast, endometrium and ovary, aromatase expression is primarly regulated by increased activity of the proximally located promoter 1.3/II region. Promoters I.3 and II lie 215 bp from each other and are coordinately stimulated by PGE2 via a cAMP-PKA-dependent pathway. In breast adipose fibroblasts exposed to PGE2 secreted by malignant epithelial cells, activation of PKC potentiates cAMP-PKA-dependent induction ofaromatase. Thus, inflammatory substances such as PGE2 may play important roles in inducing local production of estrogen that promotes tumor growth.

Antiestrogen therapy is active in selected ovarian cancer cases: the use of letrozole in estrogen receptor-positive patients

PURPOSE

To evaluate the efficacy of the aromatase inhibitor letrozole in preselected estrogen receptor (ER)-positive relapsed epithelial ovarian cancer patients and to identify markers that predict endocrine-sensitive disease.

EXPERIMENTAL DESIGN

This was a phase II study of letrozole 2.5 mg daily until clinical or marker evidence of disease progression in previously treated ER-positive ovarian cancer patients with a rising CA125 that had progressed according to Rustin's criteria. The primary end point was response according to CA125 and response evaluation criteria in solid tumors (RECIST) criteria. Marker expression was measured by semiquantitative immunohistochemistry in sections from the primary tumor.

RESULTS

Of 42 patients evaluable for CA125 response, 7 (17%) had a response (decrease of >50%), and 11 (26%) patients had not progressed (doubling of CA125) following 6 months on treatment. The median time taken to achieve the CA125 nadir was 13 weeks (range 10-36). Of 33 patients evaluable for radiological response, 3 (9%) had a partial remission, and 14 (42%) had stable disease at 12 weeks. Eleven patients (26%) had a PFS of >6 months. Subgroup analysis according to ER revealed CA125 response rates of 0% (immunoscore, 150-199), 12% (200-249), and 33% (250-300); P = 0.028, chi(2) for trend. Expression levels of HER2, insulin-like growth factor binding protein 5, trefoil factor 1, and vimentin were associated with CA125 changes on treatment.

CONCLUSIONS

This is the first study of a hormonal agent in a preselected group of ER-positive ovarian cancer patients. A signature of predictive markers, including low HER2 expression, predicts response.

Aromatase excess in cancers of breast, endometrium and ovary

Pathogenesis and growth of three common women's cancers (breast, endometrium and ovary) are linked to estrogen. A single gene encodes the key enzyme for estrogen biosynthesis named aromatase, inhibition of which effectively eliminates estrogen production in the entire body. Aromatase inhibitors successfully treat breast cancer, whereas their roles in endometrial and ovarian cancers are less clear. Ovary, testis, adipose tissue, skin, hypothalamus and placenta express aromatase normally, whereas breast, endometrial and ovarian cancers overexpress aromatase and produce local estrogen exerting paracrine and intracrine effects. Tissue-specific promoters distributed over a 93-kb regulatory region upstream of a common coding region alternatively control aromatase expression. A distinct set of transcription factors regulates each promoter in a signaling pathway- and tissue-specific manner. In cancers of breast, endometrium and ovary, aromatase expression is primarly regulated by increased activity of the proximally located promoter I.3/II region. Promoters I.3 and II lie 215 bp from each other and are coordinately stimulated by PGE(2) via a cAMP-PKA-dependent pathway. In breast adipose fibroblasts exposed to PGE(2) secreted by malignant epithelial cells, PKC is also activated, and this potentiates cAMP-PKA-dependent induction of aromatase. Thus, inflammatory substances such as PGE(2) may play important roles in inducing local production of estrogen that promotes tumor growth.

Hormonal treatments and epithelial ovarian cancer risk

Exogenous sex hormones are widely used by women either for pregnancy prevention, as part of infertility treatment, or for treatment of menopausal symptoms. The role of these hormones in the development of ovarian cancer has been vastly explored. The protective effect of combined oral contraceptive pill is confirmed in multiple studies, but it is not clear whether this protection also covers women with a genetic predisposition to ovarian cancer. There is no conclusive evidence of infertility treatments increasing ovarian cancer risk, but infertility as such is a risk factor. Currently available data suggest that long-term users of hormone replacement therapy may have a slightly increased risk for ovarian cancer compared to women who have never used estrogen. The risk might particularly involve the endometrioid type of ovarian cancer. Most data on ovarian cancer and estrogen comes from epidemiological studies, since the normally high concentrations of estrogens in ovarian tissue and follicular fluid make direct biologic studies on the effects of exogenous estrogens on the ovarian cell difficult. This review discusses the risk of ovarian cancer associated with the use of sex steroid hormones, with special emphasis on the possible risk associated with estrogens.

Profiling estrogen-regulated gene expression changes in normal and malignant human ovarian surface epithelial cells

Estrogens regulate normal ovarian surface epithelium (OSE) cell functions but also affect epithelial ovarian cancer (OCa) development. Little is known about how estrogens play such opposing roles. Transcriptional profiling using a cDNA microarray containing 2400 named genes identified 155 genes whose expression was altered by estradiol-17beta (E2) in three immortalized normal human ovarian surface epithelial (HOSE) cell lines and 315 genes whose expression was affected by the hormone in three established OCa (OVCA) cell lines. All but 19 of the genes in these two sets were different. Among the 19 overlapping genes, five were found to show discordant responses between HOSE and OVCA cell lines. The five genes are those that encode clone 5.1 RNA-binding protein (RNPS1), erythrocyte adducin alpha subunit (ADD1), plexin A3 (PLXNA3 or the SEX gene), nuclear protein SkiP (SKIIP), and Rap-2 (rap-2). RNPS1, ADD1, rap-2, and SKIIP were upregulated by E2 in HOSE cells but downregulated by estrogen in OVCA cells, whereas PLXNA3 showed the reverse pattern of regulation. The estrogen effects was observed within 6-18 h of treatment. In silicon analyses revealed presence of estrogen response elements in the proximal promoters of all five genes. RNPS1, ADD1, and PLXNA3 were underexpressed in OVCA cell lines compared to HOSE cell lines, while the opposite was true for rap-2 and SKIIP. Functional studies showed that RNPS1 and ADD1 exerted multiple antitumor actions in OVCA cells, while PLXNA3 only inhibited cell invasiveness. In contrast, rap-2 was found to cause significant oncogenic effects in OVCA cells, while SKIIP promotes only anchorage-independent growth. In sum, gene profiling data reveal that (1) E2 exerts different actions on HOSE cells than on OVCA cells by affecting two distinct transcriptomes with few overlapping genes and (2) among the overlapping genes, a set of putative oncogenes/tumor suppressors have been identified due to their differential responses to E2 between the two cell types. These findings may explain the paradoxical roles of estrogens in regulating normal and malignant OSE cell functions.

Aromatase expression in ovarian epithelial cancers

Our study focused on aromatase cytochrome P450 (CYP19) expression in ovarian epithelial normal and cancer cells and tissues. Aromatase mRNA expression was analyzed by real-time PCR in ovarian epithelial cancer cell lines, in human ovarian surface epithelial (HOSE) cell primary cultures, and in ovarian tissue specimens (n=94), including normal ovaries, ovarian cysts and cancers. Aromatase mRNA was found to be expressed in HOSE cells, in BG1, PEO4 and PEO14, but not in SKOV3 and NIH:OVCAR-3 ovarian cancer cell lines. Correlation analysis of aromatase expression was performed according to clinical, histological and biological parameters. Aromatase expression in ovarian tissue specimens was higher in normal ovaries and cysts than in cancers (P<0.0001). Using laser capture microdissection in normal postmenopausal ovaries, aromatase was found to be predominantly expressed in epithelial cells as compared to stromal component. Using immunohistochemistry (IHC), aromatase was also detected in the epithelium component. There was an inverse correlation between aromatase and ERalpha expression in ovarian tissues (P<0.001, r=-0.34). In the cancer group, no significant differences in aromatase expression were observed according to tumor histotype, grade, stage and survival. Aromatase activity was evaluated in ovarian epithelial cancer (OEC) cell lines by the tritiated water assay and the effects of third-generation aromatase inhibitors (AIs) on aromatase activity and growth were studied. Letrozole and exemestane were able to completely inhibit aromatase activity in BG1 and PEO14 cell lines. Interestingly, both AI showed an antiproliferative effect on the estrogen responsive BG1 cell line co-expressing aromatase and ERalpha. Aromatase expression was found in ovarian epithelial normal tissues and in some ovarian epithelial cancer cells and tissues. This finding raises the possibility that some tumors may respond to estrogen and provides a basis for ascertaining an antimitogenic effect of AI in a subgroup of ovarian epithelial cancers.

Expression of adrenomedullin in human ovaries, ovarian cysts and cancers. Correlation with estrogens receptor status

OBJECTIVE

To investigate the expression of adrenomedullin (AM) in benign and malignant ovarian tissues and its correlation with estrogen receptors (ERs) mRNA status.

STUDY DESIGN

Ovarian carcinoma cell lines, normal ovaries, serous cysts and cancers were analyzed using real-time polymerase chain reaction (PCR) in order to quantify adrenomedullin and ERs mRNAs expression. Some ovarian samples were submitted to laser-capture microdissection to determine the differential expression of target genes in epithelium and stroma.

RESULTS

Ovarian cancer cells express adrenomedullin mRNA for both the ligand and receptor and produce the peptide. In tumors, the ER alpha/beta ratio was higher than in other tissues. Correlations were found between ER alpha and ER beta mRNA and adrenomedullin mRNA expression in tumors.

CONCLUSION

Adrenomedullin may be involved in both normal and malignant tissue growth through both vascular and growth factor effects. Because of the correlations with ERs status, there is emerging evidence that ovarian cancer is endocrine-related.

Estrogen induction and overexpression of fibulin-1C mRNA in ovarian cancer cells

Fibulin-1 is an extracellular matrix protein induced by estradiol in estrogen receptor (ER) positive ovarian cancer cell lines. Alternative splicing of fibulin-1 mRNA results in four different variants named A, B, C and D that may have distinct biological functions. We studied the relative expression of fibulin-1 mRNA variants and their estrogen regulation in human ovarian cancer cells. In ovarian tissues and cancer cell lines, fibulin-1C and -1D are the predominant forms, whereas fibulin-1A and -1B are weakly expressed. We developed a competitive PCR assay based on coamplification of fibulin-1C and -1D to study the relative expression of these fibulin-1 variants in human ovarian samples. In ovarian cancer cell lines and ovarian cancer samples, there was a marked increase in the fibulin-1C:1D and fibulin-1C:HPRT mRNA ratios as compared to normal ovaries. In the BG1 estrogen receptor positive ovarian cancer cell line, fibulin-1C mRNA was induced by estradiol in a dose- and time-dependent manner. Since others and we have previously shown an increased expression of ERalpha as compared to ERbeta in ovarian cancer cells, we investigated whether ERalpha or ERbeta is involved in this induction. For this aim, MDA-MB-231 breast cancer cell line, which expresses both low basal levels of ERs and fibulin-1, was infected with recombinant ERalpha or ERbeta encoding adenovirus and treated with estradiol. Fibulin-1C was induced by estradiol in ERalpha- but not ERbeta-infected cells, suggesting that fibulin-1C induction is mediated through ERalpha. In ovarian tumors, a trend towards a correlation between fibulin-1C and ERalpha expression levels was noted. In conclusion, this study showed an increased fibulin-1C:-1D mRNA ratio in ovarian cancer cells as compared to normal ovaries. This finding suggests that the C variant may be involved in ovarian carcinogenesis. Fibulin-1C overexpression may thus be a clue for the understanding of a putative role of estrogens in ERalpha promoted ovarian tumor progression.

High levels of oestrogen receptor-alpha in tumorigenesis: inhibition of cell growth and angiogenic factors

We previously found that the stable overexpression of oestrogen receptor-alpha in the human endothelial cell line ECV304* inhibits its growth in vitro, and that this inhibition is possibly mediated through a down-regulation of the vasoactive agents endothelin-1 and vascular endothelial growth factor. Here we show an in vivo growth-inhibitory effect of oestrogen receptor-alpha overexpression in tumours initiated in nude mice from the same clone of ECV304. In addition, we show that this growth inhibition is accompanied by an alphavbeta3-mediated inhibition of cell migration in vitro, and a down-regulation of the integrin alphavbeta3, vascular endothelial growth factor and vascularization in vivo. The levels of vascular endothelial growth factor and integrin alphavbeta3, through their effect on cell growth and migration, contribute to the process of angiogenesis and to the pathogenesis of atherosclerosis and cancer. The results shown here demonstrate that a higher level of oestrogen receptor-alpha in the cell, through its effect on certain angiogenic factors, may play a role in the control of angiogenesis.

Production of steroids by human ovarian surface epithelial cells in culture: possible role of progesterone as growth inhibitor

OBJECTIVE

The purpose was to investigate whether normal ovarian surface epithelial cells, harvested from premenopausal and postmenopausal women, are capable of steroid production, and to evaluate effects of estradiol and progesterone on growth regulation of such cells.

METHODS

Ovarian surface epithelial cells were obtained by brushing of the ovarian surface of 9 premenopausal and 10 postmenopausal women undergoing surgery for benign gynecological diseases. The conditioned media after culture, with and without addition of FSH and LH, were analyzed for estradiol and progesterone. The proliferative effects of the steroids were analyzed using two different culture models, nonconfluent cells and confluent cells, and two different detection methods, [(3)H]thymidine incorporation and a colorimetric method assaying cell number.

RESULTS

The normal ovarian surface epithelial cells were found to secrete both estradiol and progesterone, a production that was not regulated by FSH or LH. Addition of steroids to the cultured cells did not induce any overall significant growth effects. However, progesterone significantly inhibited the growth of ovarian surface epithelial cells from three of the patients. Enhanced thymidine incorporation was observed in the presence of the progesterone receptor antagonist Org 31710 in the nonconfluent cultures of cells from postmenopausal women, but no effect of an estrogen receptor antagonist was observed.

CONCLUSIONS

The normal ovarian surface epithelium is capable of steroid production, which is also often observed in tissue from ovarian epithelial tumors. Progesterone appeared to be a negative regulator of ovarian surface epithelial growth, while estradiol had no effect.

Antisense oligonucleotide to insulin-like growth factor II induces apoptosis in human ovarian cancer AO cell line

The effects of antisense oligonucleotide to insulin-like growth factor II (IGFII) to induce apoptosis in human ovarian cancer cells were evaluated. antiproliferation effects of antisense to IGFII in ovarian cancer AO cells were determined by 3H-thymidine incorporation. Apoptosis of the IGFII antisense-treated cells was quantitated by both nuclear condensation and flow cytometry after cells were stained with propidium iodide. IGFII antisense (4.5 microM) treatment of 48 h maximally inhibited proliferation of AO cells. More than 25% of IGFII antisense-treated cells (4.5 microM for 24 h) had undergone apoptosis, whereas less than 3% of the cells were apoptotic in either IGFII sense-treated cells or untreated cells. Antisense oligonucleotide to IGFII significantly inhibited cell proliferation and induced apoptosis in human ovarian cancer AO cell. These data suggest that IGFII may be a potential target in treatment of ovarian cancer and antisense oligonucleotide to IGFII may serve as a therapeutic approach.

Estrogen regulation of transforming growth factor-alpha in ovarian cancer

Transforming growth factor alpha (TGFalpha) may be induced by estrogen in estrogen responsive systems and can contribute to the growth-modulatory effects of this hormone. To test whether TGFalpha contributes to estrogen-regulated growth in ovarian cancers, we have compared the effects of 17beta-estradiol (E2) and TGFalpha in a range of ovarian carcinoma cell lines. Addition of E2 to the estrogen receptor (ER)-positive cell lines (PE01, PE04 and PE01CDDP) produced a 2-4 fold increase in TGFalpha protein concentrations in media conditioned by the cells. Both E2 and TGFalpha stimulated the growth of the PE01 and PE04 lines and inhibited the growth of the PE01CDDP line. Furthermore, the E2-mediated growth effects could be reversed by an epidermal growth factor (EGF) receptor-targeted antibody. E2 also down-regulated EGF receptor expression in ER-positive cell lines. In a series of primary ovarian tumors, higher concentrations of ER were associated with an increased percentage of tumors expressing TGFalpha mRNA and a decreased percentage expressing EGF receptor protein. All these data are consistent with E2 increasing production of TGFalpha in ER-positive ovarian cancer and this in turn acting through the EGF receptor to modulate growth in an autocrine manner.

Progesterone induces apoptosis and up-regulation of p53 expression in human ovarian carcinoma cell lines

BACKGROUND

Progesterone (PROG) has been shown to reduce the risk of developing ovarian carcinoma in postmenopausal women who have undergone estrogen and progestogen replacement therapy, and it has been clinically used to treat some types of ovarian tumors. It is not yet clear whether or not the antitumor activity of progestogen is due to its ability to induce apoptosis in precarcinomatous and carcinomatous ovarian cells. The apoptosis-related genes p53, bcl-2, and c-myc have important roles in the regulation of programmed cell death, and thus may be involved in the process of the suspected PROG-induced apoptosis.

METHODS

Antiproliferation effects of PROG on 3AO and AO ovarian carcinoma cells were determined by 3H-thymidine incorporation. Apoptosis of the PROG-treated cells was determined by DNA laddering analysis and was quantitated by both nuclear condensation and flow cytometry after cells were stained with propidium iodide. Cell cycle analysis was also performed by flow cytometry. The expression of p53, bcl-2, and c-myc after 72 hours of PROG treatment was detected by Northern blot analysis.

RESULTS

In both 3AO and AO cell lines, cells proliferation was maximally inhibited by PROG after 72 hours of treatment at 10 microM concentration. Under the same conditions, more than 50% of PROG-treated cells had undergone apoptosis, whereas less than 3% of the cells were apoptotic in untreated cell cultures. After exposure to PROG for 72 hours, cells were arrested in the G1 phase of the cell cycle, and the levels of p53 mRNA were remarkably increased in both cell lines. No changes in expression of bcl-2 or c-myc were detected.

CONCLUSIONS

PROG significantly inhibited cell proliferation and induced apoptosis in both of the ovarian carcinoma cell lines tested in this study. PROG treatment markedly up-regulated p53 expression in these cells, indicating involvement of p53 in PROG-induced apoptosis.

Estrogen action in human ovarian cancer

Evidence is accumulating for a facilitative role for estrogen in ovarian cancer. Although response to antiestrogen therapy has been poor, there is a distinct subset of patients that respond. Strategies for treatment of ovarian cancer would be improved by identification of patients likely to respond to hormonal therapy. Cell culture models that are responsive or resistant to estrogen and antiestrogen may be of value in finding markers that predict responsiveness to hormonal therapy. Several model cell lines have been generated that express ER and proliferate in response to estrogen in vitro. Further studies are needed to better characterize the response of these ER positive cells lines to estrogen in vivo in mouse xenograft models. Expression of many of the same genes are regulated by estrogen in breast and in ovarian cancer cell lines. One exception may be the HER-2/neu oncogene product, which is down-regulated by estrogen in responsive breast carcinoma cells but not in two ovarian carcinoma cell lines. Initial analyses of several estrogen responsive and one resistant cell model suggests the potential value of progesterone receptor presence and low levels of HER-2/neu expression for predicting responsiveness to hormonal therapy. Additional cell models need to be investigated to determine the frequency with which these markers are associated with antiestrogen resistance.

Effect of Matrigel on the tumorigenicity of human breast and ovarian carcinoma cell lines

The effect of Matrigel, a solubilised tissue basement membrane extract, has been investigated on the tumorigenicity of 3 breast (MCF-7, T47D and MDA.MB.231) and 5 ovarian [PEO1, PEO1 cDDPr, PEO4, PEO14 and OV(hyg)CAR3] carcinoma cell lines. In the absence of Matrigel, the PEO14 and MDA.MB.231 cell lines produced take rates of 30% and 50%, respectively, while the other cell lines either did not develop or only occasionally developed as tumours. With Matrigel, 100% take rates were achieved for 7 of the 8 cell lines (MCF-7, T47D, MDA.MB.231, PEO1, PEO1 cDDPr, PEO4 and PEO14); in the remaining cell line [OV(hyg)CAR3] 2/6 (33%) tumours grew. Xenografts established with Matrigel could be transferred into recipient animals and grown in the absence of Matrigel, suggesting that Matrigel is necessary only for initial establishment of tumours. Furthermore, cells which had been re-established from a T47D xenograft and then inoculated into mice without Matrigel showed a take rate greater than that of the original cell line but less than that of the xenograft. In conclusion, Matrigel has proven to be extremely useful in establishing a variety of cell lines as xenografts.

SR8--the establishment and characterisation of a new ovarian carcinoma cell line and xenograft model

A new cell line, SR8, and xenograft model of ovarian carcinoma has been established in this laboratory over the past 20 months from a patient with advanced ovarian cancer. Electron microscopic examination of SR8 cells demonstrated the presence of desmosomes and tonofilaments; SR8 cells expressed epithelial membrane antigen (EMA) and glandular associated cytokeratin, all of these confirmed the epithelial origin of this cell line. In addition, SR8 cells expressed CA125, as did the original ovarian tumour. EGF-R and TP53 expression was identified by immunocytochemistry (ICC) in this line. Nearly all the SR8 cells (93%) expressed HLA-class I antigen while 13.5% expressed HLA-DR. SR8 cells showed near-diploid and -triploid chromosome populations with several clonal and non-clonal rearrangements. Subcutaneous and intraperitoneal xenografting of SR8 cells resulted in invasive tumour production at both sites in 3/4 and 4/4 female nude mice, respectively. These xenografts exhibited similar morphology as that of original tumour and were found to express EMA, cytokeratin, CA125 and TP53. The potential research applications of this cell line are discussed.

The regulation of growth and protein expression by estrogen in vitro: a study of 8 human ovarian carcinoma cell lines

The effects of 17 beta-estradiol (E2) on the growth and the levels of estrogen receptor (ER), progesterone receptor (PR) and pS2 protein were examined in a range of 8 ovarian carcinoma cell lines. E2 stimulated growth of the 3 cell lines with an ER content of 80-220 fmol/mg protein but not the 5 cell lines with ER concentrations less than 20 fmol/mg protein. After exposure to E2, ER concentration in 2 of the 3 responsive cell lines was decreased relative to untreated cells and in 2 lines, progesterone receptors were increased. No change in steroid receptor levels was observed in cell lines with low or negligible levels of receptors. The pS2 protein was not induced by E2 in the 5 ovarian carcinoma cell lines examined. These results indicate that E2 can stimulate the growth of some ER-positive ovarian carcinoma cells and that these effects may be associated with changes in the cellular levels of steroid hormone receptors.

Growth inhibition of oestrogen receptor-positive human ovarian carcinoma by anti-oestrogens in vitro and in a xenograft model

This paper presents results of the in vitro and in vivo effects of anti-oestrogens on the growth of human ovarian cancer cells. Tamoxifen and the "pure" anti-oestrogens, ICI 164,384 and ICI 182,780, inhibited the oestrogen-stimulated growth of the oestrogen receptor (ER)-positive PE04 and PE01 cell lines grown in culture, the latter two compounds being more potent than tamoxifen. In the absence of 17 beta-oestradiol (E2), tamoxifen, but not the pure anti-oestrogens, produced a small degree of growth stimulation in the PE01 and PE04 lines at concentrations between 10((7) and 10(-9) M. In contrast, growth of the ER-negative PE014 line was unaffected by E2 and all three anti-oestrogens. The effects of tamoxifen and ICI 182,780 on PE04 cells grown as xenografts in nude mice were also studied. Both anti-oestrogens produce significant growth inhibitory effects. These results indicate that ovarian carcinoma cells may be sensitive to anti-oestrogens in vitro and in vivo, and support the view that anti-oestrogens merit further clinical studies in patients with ER-positive tumours.