Steroid hormone receptors in astrocytic neoplasms

Preclinical Development of Brain Permeable ERβ Agonist for the Treatment of Glioblastoma

Glioblastoma (GBM) is the most prevalent and aggressive type of adult brain tumors with low 5-year overall survival rates. Epidemiologic data suggest that estrogen may decrease brain tumor growth, and estrogen receptor beta (ERβ) has been demonstrated to exert antitumor functions in GBM. The lack of potent, selective, and brain permeable ERβ agonist to promote its antitumor action is limiting the therapeutic promise of ERβ. In this study, we discovered that Indanone and tetralone-keto or hydroxyl oximes are a new class of ERβ agonists. Because of its high activity in ERβ reporter assays, specific binding to ERβ in polar screen assays, and potent growth inhibitory activity in GBM cells, CIDD-0149897 was discovered as a possible hit by screening a library of compounds. CIDD-0149897 is more selective for ERβ than ERα (40-fold). Treatment with CIDD-0149897 markedly reduced GBM cell viability with an IC50 of ∼7 to 15 μmol/L, while having little to no effect on ERβ-KO cells and normal human astrocytes. Further, CIDD-0149897 treatment enhanced expression of known ERβ target genes and promoted apoptosis in established and patient-derived GSC models. Pharmacokinetic studies confirmed that CIDD-0149897 has systemic exposure, and good bioavailability in the brain. Mice tolerated daily intraperitoneal treatment of CIDD-0149897 (50 mg/kg) with a 7-day repeat dosage with no toxicity. In addition, CIDD-0149897 treatment significantly decreased tumor growth in U251 xenograft model and extended the survival of orthotopic GBM tumor-bearing mice. Collectively, these findings pointed to CIDD-0149897 as a new class of ERβ agonist, offering patients with GBM a potential means of improving survival.

Targeting androgen receptor in glioblastoma

Glioblastomas are primary brain tumors that originate from glial stem cells or progenitor cells. There is a large difference in the incidence of glioblastoma between males and females. Studies revealed that the gender differences in the tumor may be attributable to the androgen receptor signaling axis. The incidence rate of glioblastoma in men is higher than that in women. Aberrant activation of the androgen receptor signaling pathway, or interactions between the androgen receptor signaling axis and other signaling axes promote the development of glioblastoma. Therefore, targeting the androgen receptor holds promise as a therapeutic approach for glioblastoma. This review investigates the dynamics of drug research into the treatment of glioblastoma by targeting the androgen receptor. The first finding in line with expectations is that androgen receptor antagonists, represented by enzalutamide, have been studied and shown to have anti-glioblastoma effects. In addition, it was found that the combination of 5-alpha reductase inhibitors and androgen receptor antagonists resulted in better therapeutic outcomes than each of them alone. Similar results were obtained with the combination of an epidermal growth factor receptor inhibitor and an androgen receptor antagonist. In addition, four small molecule compounds have been shown to exert significant anti-glioblastoma effects by directly or indirectly targeting the androgen receptor. Expectantly, one of these small molecules, seviteronel, progressed to the phase II clinical trial stage. These findings suggest that targeting the androgen receptor for glioblastoma may be a promising therapeutic option.

Effect of the Use of Gnrh Analogs in Low-Grade Cerebral Glioma

Low-grade gliomas are the most common brain tumors in children. This tumor type presents a wide range of clinical, histological, and biological behaviors. In recent years, an association between estrogens and progesterone and the development of tumors has been suggested. A case of a 2-year-old girl is described with a low-grade brain tumor treated with chemotherapy and disease stabilization. The treatment with Decapeptyl® was initiated due to precocious puberty, and the tumor showed a decrease in its solid component-more than 50% of the initial size-three years after starting treatment. Several studies have described the influence of estrogen and progesterone on the development of gliomas, decreasing or increasing their expression in those tumors with greater aggressiveness, respectively. Despite the fact that the tumor-hormonal expression relationship in other tumor types has been evaluated, its role in the treatment of brain tumors remains unknown.

Tumors of the central nervous system among women treated with fertility drugs: a population-based cohort study

PURPOSE

To investigate the association between fertility drugs and tumors of the central nervous system (CNS).

METHODS

This cohort study was based on The Danish Infertility Cohort and included 148,016 infertile women living in Denmark (1995-2017). The study cohort was linked to national registers to obtain information on use of specific fertility drugs, cancer diagnoses, covariates, emigration, and vital status. Cox proportional hazard regression models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for all CNS tumors and separately for gliomas, meningiomas and diverse benign tumors of the brain and other parts of the CNS.

RESULTS

During a median 11.3 years of follow-up, 328 women were diagnosed with CNS tumors. No marked associations were observed between use of the fertility drugs clomiphene citrate, gonadotropins, gonadotropin-releasing hormone receptor modulators and progesterone and CNS tumors. However, use of human chorionic gonadotropin was associated with a decreased rate of meningiomas (HR 0.49 95% CI 0.28-0.87). No clear associations with CNS tumors were observed according to time since first use or cumulative dose for any of the fertility drugs.

CONCLUSION

No associations between use of most types of fertility drugs and CNS tumors were observed. However, our findings only apply to premenopausal women and additional studies with longer follow-up time are necessary.

Unexplored Functions of Sex Hormones in Glioblastoma Cancer Stem Cells

Biological sex impacts a wide array of molecular and cellular functions that impact organismal development and can influence disease trajectory in a variety of pathophysiological states. In nonreproductive cancers, epidemiological sex differences have been observed in a series of tumors, and recent work has identified previously unappreciated sex differences in molecular genetics and immune response. However, the extent of these sex differences in terms of drivers of tumor growth and therapeutic response is less clear. In glioblastoma (GBM), the most common primary malignant brain tumor, there is a male bias in incidence and outcome, and key genetic and epigenetic differences, as well as differences in immune response driven by immune-suppressive myeloid populations, have recently been revealed. GBM is a prototypic tumor in which cellular heterogeneity is driven by populations of therapeutically resistant cancer stem cells (CSCs) that underlie tumor growth and recurrence. There is emerging evidence that GBM CSCs may show a sex difference, with male tumor cells showing enhanced self-renewal, but how sex differences impact CSC function is not clear. In this mini-review, we focus on how sex hormones may impact CSCs in GBM and implications for other cancers with a pronounced CSC population. We also explore opportunities to leverage new models to better understand the contribution of sex hormones vs sex chromosomes to CSC function. With the rising interest in sex differences in cancer, there is an immediate need to understand the extent to which sex differences impact tumor growth, including effects on CSC function.

Androgen Receptor, Although Not a Specific Marker For, Is a Novel Target to Suppress Glioma Stem Cells as a Therapeutic Strategy for Glioblastoma

Targeting androgen receptor (AR) has been shown to be promising in treating glioblastoma (GBM) in cell culture and flank implant models but the mechanisms remain unclear. AR antagonists including enzalutamide are available for treating prostate cancer patients in clinic and can pass the blood-brain barrier, thus are potentially good candidates for GBM treatment but have not been tested in GBM orthotopically. Our current studies confirmed that in patients, a majority of GBM tumors overexpress AR in both genders. Enzalutamide inhibited the proliferation of GBM cells both in vitro and in vivo. Although confocal microscopy demonstrated that AR is expressed but not specifically in glioma cancer stem cells (CSCs) (CD133+), enzalutamide treatment significantly decreased CSC population in cultured monolayer cells and spheroids, suppressed tumor sphere-forming capacity of GBM cells, and downregulated CSC gene expression at mRNA and protein levels in a dose- and time-dependent manner. We have, for the first time, demonstrated that enzalutamide treatment decreased the density of CSCs in vivo and improved survival in an orthotopic GBM mouse model. We conclude that AR antagonists potently target glioma CSCs in addition to suppressing the overall proliferation of GBM cells as a mechanism supporting their repurposing for clinical applications treating GBM.

Impact of sex in the prevalence and progression of glioblastomas: the role of gonadal steroid hormones

BACKGROUND

As in other types of cancers, sex is an essential factor in the origin and progression of glioblastomas. Research in the field of endocrinology and cancer suggests that gonadal steroid hormones play an important role in the progression and prevalence of glioblastomas. In the present review, we aim to discuss the actions and mechanism triggered by gonadal steroid hormones in glioblastomas.

MAIN BODY

Glioblastoma is the most common malignant primary brain tumor. According to the epidemiological data, glioblastomas are more frequent in men than in women in a 1.6/1 proportion both in children and adults. This evidence, and the knowledge about sex influence over the prevalence of countless diseases, suggest that male gonadal steroid hormones, such as testosterone, promote glioblastomas growth. In contrast, a protective role of female gonadal steroid hormones (estradiol and progesterone) against glioblastomas has been questioned. Several pieces of evidence demonstrate a variety of effects induced by female and male gonadal steroid hormones in glioblastomas. Several studies indicate that pregnancy, a physiological state with the highest progesterone and estradiol levels, accelerates the progression of low-grade astrocytomas to glioblastomas and increases the symptoms associated with these tumors. In vitro studies have demonstrated that progesterone has a dual role in glioblastoma cells: physiological concentrations promote cell proliferation, migration, and invasion while very high doses (out physiological range) reduce cell proliferation and increases cell death.

CONCLUSION

Gonadal steroid hormones can stimulate the progression of glioblastomas through the increase in proliferation, migration, and invasion. However, the effects mentioned above depend on the concentrations of these hormones and the receptor involved in hormone actions. Estradiol and progesterone can exert promoter or protective effects while the role of testosterone has been always associated to glioblastomas progression.

5alpha-dihydroprogesterone promotes proliferation and migration of human glioblastoma cells

Glioblastomas (GBMs) are the most common and deadliest intracranial tumors. Steroid hormones, such as progesterone (P4), at physiological concentrations, promote proliferation, and migration of human GBM cells in vivo and in vitro. Neuronal and glial cells, but also GBMs, metabolize P4 and synthesize different active metabolites such as 5α-dihydroprogesterone (5α-DHP). However, their contribution to GBM malignancy remains unknown. Here, we determined the 5α-DHP effects on the number of cells, proliferation, and migration of the U87 and U251 human GBM-derived cell lines. Of the tested concentrations (1 nM-1 µM), 5α-DHP 10 nM significantly increased the number of U87 and U251 cells from day 2 of treatment, and proliferation (at day 3) in a similar manner as P4 (10 nM). The treatment with the progesterone receptor (PR) antagonist RU486 (mifepristone), blocked the effects of 5α-DHP on the number of cells and proliferation. Besides, in U251 and LN229 GBM cells, 5α-DHP promoted cell migration (from 12 to 24 h). We also determined that GBM cells expressed the 3α-hydroxysteroid oxidoreductases (3α-HSOR), which reversibly reduce 5α-DHP to allopregnanolone (3α-THP). These data indicate that 5α-DHP induces proliferation and migration of human GBM through the activation of PR.

Estradiol Induces Epithelial to Mesenchymal Transition of Human Glioblastoma Cells

The mesenchymal phenotype of glioblastoma multiforme (GBM), the most frequent and malignant brain tumor, is associated with the worst prognosis. The epithelial–mesenchymal transition (EMT) is a cell plasticity mechanism involved in GBM malignancy. In this study, we determined 17β-estradiol (E2)-induced EMT by changes in cell morphology, expression of EMT markers, and cell migration and invasion assays in human GBM-derived cell lines. E2 (10 nM) modified the shape and size of GBM cells due to a reorganization of actin filaments. We evaluated EMT markers expression by RT-qPCR, Western blot, and immunofluorescence.We found that E2 upregulated the expression of the mesenchymal markers, vimentin, and N-cadherin. Scratch and transwell assays showed that E2 increased migration and invasion of GBM cells. The estrogen receptor-α (ER-α)-selective agonist 4,4’,4’’-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT, 10 nM) affected similarly to E2 in terms of the expression of EMT markers and cell migration, and the treatment with the ER-α antagonist methyl-piperidino-pyrazole (MPP, 1 μM) blocked E2 and PPT effects. ER-β-selective agonist diarylpropionitrile (DNP, 10 nM) and antagonist 4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazole[1,5-a]pyrimidin-3-yl]phenol (PHTPP, 1 μM) showed no effects on EMT marker expression. These data suggest that E2 induces EMT activation through ER-α in human GBM-derived cells.

Progesterone at high doses reduces the growth of U87 and A172 glioblastoma cells: Proteomic changes regarding metabolism and immunity

While pregnancy may accelerate glioblastoma multiforme (GBM) growth, parity and progesterone (P4) containing treatments (ie, hormone replacement therapy) reduce the risk of GBM development. In parallel, low and high doses of P4 exert stimulating and inhibitory actions on GBM growth, respectively. The mechanisms behind the high‐dose P4‐suppression of GBM growth is unknown. In the present study, we assessed the changes in growth and proteomic profiles when high‐dose P4 (100 and 300 µM) was administered in human U87 and A172 GBM cell lines. The xCELLigence system was used to examine cell growth when different concentrations of P4 (20, 50, 100, and 300 µM) was administered. The protein profiles were determined by two‐dimensional gel electrophoresis in both cell lines when 100 and 300 µM P4 were administered. Finally, the pathways enriched by the differentially expressed proteins were assessed using bioinformatic tools. Increasing doses of P4 blocked the growth of both GBM cells. We identified 26 and 51 differentially expressed proteins (fc > 2) in A172 and U87 cell lines treated with P4, respectively. Only the pro‐tumorigenic mitochondrial ornithine aminotransferase and anti‐apoptotic mitochondrial 60 kDa heat shock protein were downregulated in A172 cell line and U87 cell line when treated with P4, respectively. Detoxification of reactive oxygen species, cellular response to stress, glucose metabolism, and immunity‐related proteins were altered in P4‐treated GBM cell lines. The paradox on the effect of low and high doses of P4 on GBM growth is gaining attention. The mechanism related to the high dose of P4 on GBM growth can be explained by the alterations in detoxification mechanisms, stress, and immune response and glucose metabolism. P4 suppresses GBM growth and as it is nontoxic in comparison to classical chemotherapeutics, it can be used as a new strategy in GBM treatment in the future.

Tibolone Effects on Human Glioblastoma Cell Lines

BACKGROUND

Ovarian steroid hormones are involved in modulating the growth of glioblastomas (the most common, aggressive, and lethal brain tumor) through the interaction with their intracellular receptors. Activation of sex hormone receptors is involved in glioblastomas progression. Tibolone (TIB) is a selective tissue estrogenic activity regulator widely prescribed to treat menopausal symptoms and to prevent bone lost. The effects of TIB on the growth of glioblastoma are unknown.

AIM OF THE STUDY

To evaluate the effects of TIB on cell number, migration, and invasion of two derived human glioblastoma cell lines (U251 MG and U87), as well as the role of this steroid in estrogen and progesterone receptors activity and content.

METHODS

U251-MG and U87 human glioblastoma cell lines were grown with different doses of TIB. The number of cells was determined and migration and invasion tests were carried out. Protein expression was performed by Western blot.

RESULTS

We observed that TIB (10 nM) increased the number of cells by inducing proliferation with no effects on cell migration or invasion. The increase in cell proliferation induced by TIB was blocked by estrogen (ERs) or progesterone receptor (PRs) antagonists, ICI 182, 780 and RU 486, suggesting that these receptors mediate proliferating actions of TIB; TIB also modified the content of ERs and PRs by increasing ER-α, ER-β, and PR-B, while decreased PR-A.

CONCLUSION

Our results suggest that TIB increases cell number and proliferation of human glioblastoma cells through the regulation of ERs and PRs actions and content.

Estrogen receptor beta enhances chemotherapy response of GBM cells by down regulating DNA damage response pathways

Glioblastoma (GBM) is the most commonly diagnosed brain tumor that exhibit high mortality rate and chemotherapy resistance is a major clinical problem. Recent studies suggest that estrogen receptor beta (ERβ), may function as a tumor suppressor in GBM. However, the mechanism(s) by which ERβ contributes to GBM suppression and chemotherapy response remains unknown. We examined the role of ERβ in the DNA damage response of GBM cells, and tested whether ERβ sensitizes GBM cells to chemotherapy. Cell viability and survival assays using multiple epitope tagged ERβ expressing established and primary GBM cells demonstrated that ERβ sensitizes GBM cells to DNA damaging agents including temozolomide (TMZ). RNA-seq studies using ERβ overexpression models revealed downregulation of number of genes involved in DNA recombination and repair, ATM signaling and cell cycle check point control. Gene set enrichment analysis (GSEA) suggested that ERβ–modulated genes were correlated negatively with homologous recombination, mismatch repair and G2M checkpoint genes. Further, RT-qPCR analysis revealed that chemotherapy induced activation of cell cycle arrest and apoptosis genes were attenuated in ERβKO cells. Additionally, ERβ overexpressing cells had a higher number of γH2AX foci following TMZ treatment. Mechanistic studies showed that ERβ plays an important role in homologous recombination (HR) mediated repair and ERβ reduced expression and activation of ATM upon DNA damage. More importantly, GBM cells expressing ERβ had increased survival when compared to control GBM cells in orthotopic GBM models. ERβ overexpression further enhanced the survival of mice to TMZ therapy in both TMZ sensitive and TMZ resistant GBM models. Additionally, IHC analysis revealed that ERβ tumors had increased expression of γH2AX and cleaved caspase-3. Using ERβ-overexpression and ERβ-KO GBM model cells, we have provided the evidence that ERβ is required for optimal chemotherapy induced DNA damage response and apoptosis in GBM cells.

From epidemiology and neurodevelopment to antineoplasticity. Medroxyprogesterone reduces human glial tumor growth in vitro and C6 glioma in rat brain in vivo

OBJECTIVE

Glial tumor growth may accelerate during gestation, but epidemiological studies consistently demonstrated that parousity reduces life long risk of glial tumors. Pregnancy may also accelerate growth of medulloblastoma and meningioma, but parousity does not confer protection against these tumors. We were the first to show that medroxyprogesterone acetate (MPA) reduces rat C6 glioma growth in vitro. Now we aimed to determine the effects of MPA on human brain cancers (particularly glioblastoma) in vitro and C6 glioma in vivo.

PATIENTS AND METHODS

We evaluated the effects of MPA on: i) monolayer growth of human U87 and U251 glioblastoma, ii) 3D-spheroid growth and invasion of C6 rat glioma and human U251 glioma, iii) interactions with PI3-Kinase inhibitors and coxsackie-adenovirus receptor (CAR) in modifying 3D-spheroid invasion of glioma.

RESULTS

MPA at low doses (3.25-13 μM) insignificantly stimulated and at high doses (above 52 μM) strongly suppressed the growth of human U87 and U251 cells in vitro. MPA also binds to glucocorticoid receptors similar to dexamethasone (Dex) and unexpectedly, PI3-Kinase inhibitors at low doses suppressed anti-invasive efficacies of MPA and Dex. MPA exerted higher invasion-inhibitory effects on CAR-expressing human glioma cells. Lastly, MPA suppressed growth of C6 glioma implanted into rat brain.

CONCLUSION

Progesterone analogues deserve to be studied in future experimental models of high grade glial brain tumors.

Update on the therapeutic significance of estrogen receptor beta in malignant gliomas

Malignant glioma is the most fatal of the astrocytic lineage tumors despite therapeutic advances. Men have a higher glioma incidence than women, indicating that estrogen level differences between men and women may influence glioma pathogenesis. However, the mechanism underlying the anticancer effects of estrogen has not been fully clarified and is complicated by the presence of several distinct estrogen receptor types and the identification of a growing number of estrogen receptor splice variants. Specifically, it is generally accepted that estrogen receptor alpha (ERα) functions as a tumor promoter, while estrogen receptor beta (ERβ) functions as a tumor suppressor, and the role and therapeutic significance of ERβ signaling in gliomas remains elusive. Thus, a deeper analysis of ERβ could elucidate the role of estrogens in gender-related cancer incidence. ERβ has been found to be involved in complex interactions with malignant gliomas. In addition, the prognostic value of ERβ expression in glioma patients should not be ignored when considering translating experimental findings to clinical practice. More importantly, several potential drugs consisting of selective ERβ agonists have exhibited anti-glioma activities and could further extend the therapeutic potential of ERβ-selective agonists. Here, we review the literature to clarify the anti-glioma effect of ERβ. To clarify ERβ-mediated treatment effects in malignant gliomas, this review focuses on the potential mechanisms mediated by ERβ in the intracellular signaling events in glioma cells, the prognostic value of ERβ expression in glioma patients, and various ERβ agonists that could be potential drugs with anti-glioma activities.

Expression of estrogen and progesterone receptors in astrocytomas: a literature review

Gliomas are the most common type of primary central nervous system neoplasm. Astrocytomas are the most prevalent type of glioma and these tumors may be influenced by sex steroid hormones. A literature review for the presence of estrogen and progesterone receptors in astrocytomas was conducted in the PubMed database using the following MeSH terms: "estrogen receptor beta" OR "estrogen receptor alpha" OR "estrogen receptor antagonists" OR "progesterone receptors" OR "astrocytoma" OR "glioma" OR "glioblastoma". Among the 111 articles identified, 13 studies met our inclusion criteria. The majority of reports showed the presence of estrogen and progesterone receptors in astrocytomas. Overall, higher tumor grades were associated with decreased estrogen receptor expression and increased progesterone receptor expression.

Cancer therapy using natural ligands that target estrogen receptor beta

Estrogen receptor beta (ERβ) is one of the two key receptors (ERα, ERβ) that facilitate biological actions of 17β-estradiol (E2). ERβ is widely expressed in many tissues, and its expression is reduced or lost during progression of many tumors. ERβ facilitates estrogen signaling by both genomic (classical and non-classical) and extra-nuclear signaling. Emerging evidence suggests that ERβ functions as a tissue-specific tumor suppressor with anti-proliferative actions. Recent studies have identified a number of naturally available selective ERβ agonists. Targeting ERβ using its naturally available ligands is an attractive approach for treating and preventing cancers. This review presents the beneficial actions of ERβ signaling and clinical utility of several natural ERβ ligands as potential cancer therapy.

Highly selective salicylketoxime-based estrogen receptor β agonists display antiproliferative activities in a glioma model

Estrogen receptor β (ERβ) selective agonists are considered potential therapeutic agents for a variety of pathological conditions, including several types of cancer. Their development is particularly challenging, since differences in the ligand binding cavities of the two ER subtypes α and β are minimal. We have carried out a rational design of new salicylketoxime derivatives which display unprecedentedly high levels of ERβ selectivity for this class of compounds, both in binding affinity and in cell-based functional assays. An endogenous gene expression assay was used to further characterize the pharmacological action of these compounds. Finally, these ERβ-selective agonists were found to inhibit proliferation of a glioma cell line in vitro. Most importantly, one of these compounds also proved to be active in an in vivo xenograft model of human glioma, thus demonstrating the high potential of this type of compounds against this devastating disease.

Evidence for involvement of steroid receptors and coactivators in neuroepithelial and meningothelial tumors

Steroid receptors such as androgen receptor (AR) and estrogen receptors (ER) ER-α and ER-β, and their receptor coactivators (steroid receptor coactivator, SRC) are widely localized in the brain. Although previous studies have investigated the expression of steroid receptors in brain tumors like astrocytoma, the studies on the expression of steroid receptors and SRCs in other brain tumors are lacking. Here, we investigated the expression of AR, ERs, and SRCs in neuroepithelial (medulloblastoma, ependymoma, oligodendroglioma) and meningothelial meningioma using tissue microarray immunohistochemistry. Compared to normal brain tissue, we found that the expression of SRC-1, SRC-3, and ER-α significantly decreased in meningothelial tumor and neuroepithelial tumor, suggesting that the SRC-1/SRC-3 levels may be regulated by ER-α. Moreover, the levels of AR strongly correlated to the levels of ER-β. Furthermore, correlation was also detected between SRC-3 and AR in neuroepithelial tumor, and between ER-α and ER-β in meningothelial tumor. In addition, the decreased ratio of SRC-1/SRC-3 was associated with an increase of ER-β in neuroepithelial tumor. These results indicate that expressions of different steroid receptors and activators may be tumor type dependent. While AR, ER-α, and ER-β may be involved in the pathogenesis of meningothelial tumor, SRCs/ER-β axis and SRC-3/AR axis may play a role in the pathogenesis of neuroepithelial tumor.

Androgen receptor signaling regulates growth of glioblastoma multiforme in men

Although glioblastoma multiforme (GBM) is the most malignant primary human brain cancer with surprisingly high incidence rate in adult men than in women, the exact mechanism underlying this pronounced epidemiology is unclear. Here, we showed significant upregulated androgen receptor (AR) expression in the GBM tissue compared to the periphery normal brain tissue in patients. An expression of AR was further detected in all eight examined human GBM cell lines. To figure out whether AR signaling may play a role in GBM, we used high AR-expressing U87-MG GBM line for further study. We found that activation of transforming growth factor β (TGFβ) receptor signaling by TGFβ1 in GBM significantly inhibited cell growth and increased apoptosis. Moreover, application of active AR ligand 5α-dihydrotestosterone (DHT) significantly decreased the effect of TGFβ1 on GBM growth and apoptosis, suggesting that AR signaling pathway may contradict the effect of TGFβ receptor signaling in GBM. However, neither total protein nor the phosphorylated protein of SMAD3, a major TGFβ receptor signaling downstream effector in GBM, was affected by DHT, suggesting that AR activation may not affect the SMAD3 protein production or phosphorylation of TGFβ receptor and SMAD3. Finally, immunoprecipitation followed by immunoblot confirmed binding of pAR to pSMAD3, which may prevent the DNA binding of pSMAD3 and subsequently prevent its effect on cell growth in GBM. Taken together, our study suggests that AR signaling may promote tumorigenesis of GBM in adult men by inhibiting TGFβ receptor signaling.

Aromatase and estrogen receptor alpha mRNA expression as prognostic biomarkers in patients with astrocytomas

Estrogens are oncogenic hormones at a high level in breast, prostate, endometrial and lung cancer. Estrogens are synthesized by aromatase which has been used as a biomarker both in breast and lung cancer. Estrogen biological activities are executed by their classic receptors (ERα and ERβ). ERα has been described as a cancer promoter and ERβ, as a possible tumor suppressor. Both receptors are present at low levels in primary multiforme glioblastoma (GBM). The GBM frequency is 50 % higher in men than in women. The GBM patient survival period ranges from 7 to 18 months. The purpose of this pilot study was to evaluate aromatase and estrogen receptor expression, as well as 17ß-estradiol concentration in astrocytoma patients biopsies to obtain a prognosis biomarker for these patients. We analyzed 36 biopsies of astrocytoma patients with a different grade (I-IV) of malignity. Aromatase and estrogen receptor mRNA expression were analyzed by semiquantitative RT-PCR, and the E2 levels, by ELISA. E2 concentration was higher in GBM, compared to grade II or III astrocytomas. The number of cells immunoreactive to aromatase and estrogen receptors decreased as the grade of tumor malignity increased. Aromatase mRNA expression was present in all biopsies, regardless of malignity grade or patient age or gender. The highest expression of aromatase mRNA in GBM patients was associated to the worst survival prognostic (6.28 months). In contrast lowest expression of ERα mRNA in astrocytoma patients had a worst prognosis. In conclusion, aromatase and ERα expression could be used as prognosis biomarkers for astrocytoma patients.

A pooled multisite analysis of the effects of female reproductive hormones on glioma risk

PURPOSE

The association between female reproductive factors and glioma risk is unclear, but most published studies have been limited by small sample size. We conducted a pooled multisite study of pre- and postmenopausal women, investigating the effect of female reproductive factors, including hormonal medications.

METHODS

Unconditional logistic regression was used to calculate odds ratios (ORs) and 95 % confidence intervals (95 % CIs) assessing the effects of female reproductive factors and female hormonal medications in glioma cases and unrelated controls.

RESULTS

Menarche over the age of 15 as compared to under 12 was associated with a statistically significant risk for glioma (OR 2.00, 95 % CI 1.47-2.71). Use of oral contraceptive pills (OCP) was inversely associated with risk of glioma (OR 0.61, 95 % CI 0.50-0.74), and there was an inverse trend with longer duration of OCP use (p for trend <0.0001). Use of hormone replacement therapy (HRT) was also inversely associated with risk of glioma (OR 0.55, 95 % CI 0.44-0.68), and there was an inverse trend with longer duration of use (p for trend <0.0001). Compared to those reporting neither OCP use nor HRT use, those who reported using both were less likely to have a diagnosis of glioma (OR 0.34, 95 % CI 0.24-0.48).

CONCLUSIONS

Female reproductive hormones may decrease the risk for glioma. The association appears to be strongest with greater length of use and use of both HRT and OCP.

Progesterone induces the growth and infiltration of human astrocytoma cells implanted in the cerebral cortex of the rat

Progesterone (P4) promotes cell proliferation in several types of cancer, including brain tumors such as astrocytomas, the most common and aggressive primary intracerebral neoplasm in humans. In this work, we studied the effects of P4 and its intracellular receptor antagonist, RU486, on growth and infiltration of U373 cells derived from a human astrocytoma grade III, implanted in the motor cortex of adult male rats, using two treatment schemes. In the first one, fifteen days after cells implantation, rats were daily subcutaneously treated with vehicle (propylene glycol, 160  μ L), P4 (1 mg), RU486 (5 mg), or P4 + RU486 (1 mg and 5 mg, resp.) for 21 days. In the second one, treatments started 8 weeks after cells implantation and lasted for 14 days. In both schemes we found that P4 significantly increased the tumor area as compared with the rest of the treatments, whereas RU486 blocked P4 effects. All rats treated with P4 showed tumor infiltration, while 28.6% and 42.9% of the animals treated with RU486 and P4 + RU486, respectively, presented it. Our data suggest that P4 promotes growth and migration of human astrocytoma cells implanted in the motor cortex of the rat through the interaction with its intracellular receptor.

Expression of estrogen receptors, androgen receptor and steroid receptor coactivator-3 is negatively correlated to the differentiation of astrocytic tumors

Astrocytic tumors are the most common primary brain tumors. It has been reported that androgen receptor (AR), estrogen receptors alpha (ERα) and beta (ERβ) and their coactivator SRC-1 and SRC-3 are involved in the regulation of the growth and development of many tumors, but their expression profiles and significances in the astrocytic tumors remain largely unknown. In this study, the expression of AR, ERs, and SRCs, and the possible roles of them in astrocytic neoplasm were evaluated and compared to normal brain tissues by nickel-intensified immunohistochemistry with tissue microarrays. The results showed that there were no age- or gender-differences regarding to the levels of these receptors or coactivators in astrocytic or normal brain tissues. In the high-grade astrocytic tissue, the levels of AR, ERs and SRC-3 were significantly decreased when compared to the low-grade astrocytic tissues, but the levels of SRC-1 remain unchanged. Correlation analysis revealed that the levels of AR, ERs and SRC-3 were negatively correlated to tumor differentiation, and the levels of SRC-3 were positively correlated to that of ERα. Furthermore, the decreased levels of SRC-3 were associated with an increase of ERβ in astrocytic tumors when compared to that of normal brain tissues. These above results indicate a combination of decreased expression of ERs, AR and SRC-3 but not SRC-1 may be involved in the tumorigenesis of gliomas, ERα/SRC-3 axis may play central role in the regulation these tumors.

Exogenous and endogenous hormones in relation to glioma in women: a meta-analysis of 11 case-control studies

BACKGROUND AND OBJECTIVE

Previous investigations of glioma risk in women have focused on oral contraceptive (OC), hormone replacement therapy (HRT), and reproductive factors. However, the results of published studies were inconclusive and inconsistent. Thus, a meta-analysis based on published case-control studies was performed to assess the role of exogenous and endogenous hormones factors in glioma risk.

METHODS

The PubMed and EMBASE databases were searched without any restrictions on language or publication year. Reference lists from retrieved articles were also reviewed. We included case-control studies reporting relative risks (RRs) with corresponding 95% confidence intervals (CIs) (or data to calculate them) between oral contraceptive (OC) and hormone replacement therapy (HRT) use, reproductive factors and glioma. Random-effects models were used to calculate the summary risk estimates.

RESULTS

Finally, 11 eligible studies with 4860 cases and 14,740 controls were identified. A lower risk of glioma was observed among women who were ever users of exogenous hormones (OC RR = 0.707, 95% CI = 0.604-0.828; HRT: RR = 0.683, 95% CI = 0.577-0.808) compared with never users. An increased glioma risk was associated with older age at menarche (RR = 1.401, 95% CI = 1.052-1.865). No association was observed for menopause status, parous status, age at menopause, or age at first birth and glioma risk.

CONCLUSION

The results of our study support the hypothesis female sex hormones play a role in the development of glioma in women. Additional studies are warranted to validate the conclusion from this meta-analysis and clarity the underlying mechanisms.

The role of DNA methylation and histone acetylation in the regulation of progesterone receptor isoforms expression in human astrocytoma cell lines

Many progesterone (P4) effects are mediated by its intracellular receptor (PR), which has two isoforms, PR-A and PR-B, each of them with different function and regulation. Differential PR expression in cancer cells has been associated to a PR isoform-specific promoter methylation. In astrocytomas, the most frequent and aggressive brain tumors, PR isoforms expression is directly correlated to the tumor's evolution grade. However, there is no evidence of the role of epigenetic regulation of PR expression in astrocytomas. We evaluated the effect of the demethylating agent 5-aza-2'-deoxycytidine (5AzadC) and the histone deacetylase inhibitor trichostatin A (TSA) on PR expression in human astrocytoma cell lines U373 (grade III) and D54 (grade IV) by RT-PCR and Western blot. Total PR expression increased with 5 μM 5AzadC treatment, whereas PR-B expression increased with 5 and 10 μM 5AzadC treatment in U373 cells, but not in D54 cells. In U373 cells, PR-A protein content augmented with 10 μM 5AzadC treatment, while PR-B content increased with 5 and 10 μM 5AzadC. PR-B expression was not modified by the TSA concentrations that were used, and the combination with 5AzadC did not change the effects of the latter. The study of 5AzadC effects on the number of astrocytoma cells showed that P4 treatment increased the number of U373 cells, whereas 5AzadC and the combined treatment with P4 reduced it. Our results suggest that PR-B expression is regulated by methylation and not by histone acetylation in U373 cells, and that DNA demethylation reduced the number of U373 cells.

Parity, age at first birth, and risk of death from brain cancer: a population-based cohort study in Taiwan

Background

This study was undertaken to examine whether there is an association between parity and age at first birth and risk of death from brain cancer.

Methods

The study cohort consisted of 1,292,462 women who had a first and singleton childbirth between Jan. 1, 1978 and Dec. 31, 1987. We tracked each woman from the time of their first childbirth to December 31, 2009, and their vital status was ascertained by linking records with the computerized mortality database. Cox proportional hazard regression models were used to estimate the hazard ratios (HR) of death from brain cancer associated with parity and age at first birth.

Results

There were 316 brain cancer deaths during 34,980,246 person-years of follow-up. The mortality rate of brain cancer was 0.90 cases per 100,000 person-years. The adjusted HR was 1.35 (95% CI= 0.91-2.01) for women who gave birth between 21 and 25, 1.61 (95% CI=1.05-2.45) for women who gave birth after 25 years of age, respectively, when compared with women who gave birth less than 20 years. A trend of increasing risk of brain cancer was seen with increasing age at first birth. The adjusted HR were 0.73 (95% CI= 0.53-0.99) for women who had 2 children, and 0.60 (95% CI =0.43-0.83) for women with 3 or more births, respectively, when compared with women who had given birth to only 1 child. There was a significant decreasing trend in the HRs of brain cancer with increasing parity.

Conclusions

This study provides evidence that reproductive factors (parity and early age at first birth) may confer a protective effect on the risk of death from brain cancer.

Progesterone receptor and SRC-1 participate in the regulation of VEGF, EGFR and Cyclin D1 expression in human astrocytoma cell lines

Astrocytomas are the most common primary brain tumors in humans. It has been reported that vascular endothelial growth factor (VEGF), epidermal growth factor receptor (EGFR), cyclin D1 and progesterone receptor (PR) expression levels are elevated in patients with high-grade astrocytomas. Progesterone (P) regulates astrocytomas growth through its interaction with PR, which recruits coregulatory proteins such as steroid receptor coactivator-1 (SRC-1) that are required for efficient transcriptional activation. The regulation of VEGF, EGFR and cyclin D1 expression by P in human astrocytoma cells is not known. We studied the role of PR and SRC-1 in the expression of VEGF, EGFR and cyclin D1 mediated by P in human astrocytoma cell lines grade III (U373) and IV (D54). P significantly increased VEGF and EGFR mRNA expression after 12h of treatment in D54 cells that was reflected at protein level 24h after treatment. This effect was blocked by the PR antagonist, RU 486. In U373 cells cyclin D1 mRNA and protein expression was induced by P after 6 and 8h of treatment, respectively, and this effect was blocked with RU 486. Transfection with short hairpin RNA targeting coactivator SRC-1 significantly reduced VEGF expression after 24h of treatment. Collectively, our results indicate that P regulates VEGF and EGFR expression in D54 cells and cyclin D1 expression in U373 through PR, and that SRC-1 participates in the regulation of VEGF expression.

Integration of ERα-PELP1-HER2 signaling by LSD1 (KDM1A/AOF2) offers combinatorial therapeutic opportunities to circumventing hormone resistance in breast cancer

LSD1, an epigenetic modifier, and PELP1, an estrogen receptor co-activator, integrate estrogen receptor ERα and HER2 receptor tyrosine kinase signaling to promote aromatase expression and hormone resistance in a preclinical model of post-menopausal breast cancer. In the previous issue of Breast Cancer Research, Cortez et al. show, for the first time, that knockdown or drug-mediated inhibition of PELP1 or LSD1 suppresses LSD1-mediated transcriptionally activating histone marks at ERα target genes, inhibits aromatase gene expression, and sensitizes hormone refractory breast cancer cells to tamoxifen or letrozole treatments. The relevance of PELP1-LSD1 signaling to other nuclear hormone receptor-dependent cancers and structural considerations for the selective drug targeting of LSD1 are further discussed in this editorial.

Therapeutic significance of estrogen receptor β agonists in gliomas

Gliomas are the most common and devastating central nervous system neoplasms. A gender bias exists in their development: females are at lower risk than males, implicating estrogen-mediated protective effects. Estrogen functions are mediated by two estrogen receptor (ER) subtypes: ERα, which functions as tumor promoter, and ERβ, which functions as tumor suppressor. We examined the potential use of ERβ agonists as a novel therapeutic to curb the growth of gliomas. Western analysis of six glioma model cells showed detectable expression of ERβ with little or no ERα. Treatment of glioma cells with ERβ agonists resulted in significant decrease in proliferation. Immunohistochemical analysis of tumor tissues revealed that ERβ expression is downregulated in high-grade gliomas. We found that ERβ agonists promote both expression and tumor-suppressive functions of ERβ in glioma cells. Liquiritigenin, a plant-derived ERβ agonist significantly reduced in vivo tumor growth in a xenograft model. Compared with control mice, animals treated with liquiritigenin had greater than 50% reduction in tumor volume and size. Immunohistochemical analysis of tumors revealed a significant increase in the nuclear ERβ expression with a concomitant decrease in cell proliferation in the liquiritigenin-treated group. Our results suggest that ERβ signaling has a tumor-suppressive function in gliomas. Because ERβ agonists are currently in clinical trials and are well tolerated with fewer side effects, identification of an ERβ agonist as a therapeutic agent can be readily extended to clinical use with current chemotherapies, providing an additional tool for enhancing survival in glioma patients.

Cell Models for the Study of Sex Steroid Hormone Neurobiology

To date many aspects of neurons and glia biology remain elusive, due in part to the cellular and molecular complexity of the brain. In recent decades, cell models from different brain areas have been established and proven invaluable toward understanding this complexity. In the field of steroid hormone neurobiology, an important question is: what is the profile of steroid hormone receptor expression in these specific cell lines? Currently, a clear summary of such receptor profiling is lacking. For this reason, we summarized in this review the expression of estrogen, progesterone, and androgen receptors in several widely used cell lines (glial and neuronal) derived from the forebrain and midbrain, based on our own data and that from the literature. Such information will aid in the selection of specific cell lines used to test hypotheses related to the biology of estrogens, progestins, and/or androgens.

Prognostic value of novel biomarkers in astrocytic brain tumors: nuclear receptor co-regulators AIB1, TIF2, and PELP1 are associated with high tumor grade and worse patient prognosis

Estrogen receptors alpha (ERα) and beta (ERβ) and their co-regulatory proteins are key components of complex signaling networks that specifically regulate the growth and development of various tissues and tumors. Still, their protein expression profiles and possible role in the pathogenesis of astrocytic tumors remain largely unknown. The purpose of the present study is to evaluate the differential protein expression of ΕRα, ERβ, and their co-activators, AIB1, TIF2, and PELP1 in astrocytic tumors of World Health Organization (WHO) grade II-IV, using immunohistochemistry. Potential correlations with clinicopathological parameters and patient prognosis were also explored. ERα protein expression was undetectable while ERβ levels were significantly decreased with progression of tumor grade (P < 0.001). High expression of ERβ was an independent favorable prognostic factor on multivariate analysis (P = 0.003). Expression of AIB1, TIF2, and PELP1 was not correlated with ERβ expression and followed an opposite trend, with increasing levels in high-grade relative to low-grade tumors (P < 0.001). Univariate survival analysis revealed that high AIB1, TIF2, and PELP1 expression was associated with worse prognosis (P = 0.049, P = 0.033, and P = 0.020, respectively). ERβ and ER co-activators AIB1, TIF2, and PELP1 appear to play an important role in the pathogenesis and progression of astrocytic tumors and might have prognostic significance. The mechanisms underlying their involvement in astrocytic tumorigenesis, as well as their utility for prognostic and therapeutic purposes merit further investigation.

A systematic review of the literature on the effects of dexamethasone on the brain from in vivo human-based studies: implications for physiological brain imaging of patients with intracranial tumors

BACKGROUND

Among glucocorticoids, dexamethasone is most widely used for treatment of cerebral edema because of its long biological half-life and its low mineralocorticoid activity (sodium retaining).

OBJECTIVE

A systematic review of the literature on the effects of dexamethasone on the brain from in vivo studies in humans.

METHODS

A MEDLINE database search (via the PubMed interface) and an EMBASE database search (via the Dialog interface) of the past 35 years was performed. Every article relating to human use reported in English was included. In addition, references of all eligible articles were searched to identify other possible sources.

RESULTS

Twenty-four articles matched the eligibility criteria. There were disparate methodologies and conflicting results, although they tended to indicate a decrease in blood-tumor barrier permeability, decreased tumoral perfusion, decreased tumoral diffusivity, and the possibility of decreased perfusion in contralateral normal-appearing brain tissue.

CONCLUSION

Treatment with dexamethasone may alter imaging parameters from cerebral perfusion studies used in the management of brain tumors. In adequately powered studies, it may be possible to assess the longer term effects of dexamethasone on normal brain tissue to help optimize use with longer term survivors that are emerging as improvements in glioma treatment are made.

Brain tumors and hormonal factors: review of the epidemiological literature

BACKGROUND

To date, the etiology of primary tumors of the central nervous system (mainly gliomas and meningiomas) is poorly understood. The role of sex hormones has been suggested, based on clinical, experimental, biological, and epidemiological data.

OBJECTIVE

To review the epidemiological studies on the relation between hormonal factors and the occurrence of glioma and meningioma, in order to identify new research developments.

METHODS

Articles published until September 2010 were selected by considering exogenous and endogenous exposures and specific brain tumors. Standardized information was collected from 20 articles: 15 concerning gliomas and 13 meningiomas.

RESULTS

An increased glioma risk was observed with later menarche and menopause, while a reduced glioma risk was observed with hormone replacement therapy (HRT) and oral contraceptive use, despite duration of use had no effect on risk. Meningioma risk increased after menopause and with HRT use. No clear association was found with pregnancy and breastfeeding.

CONCLUSION

Results are globally concordant with the biologic hypothesis assuming that female sex hormones are protective against glioma and may increase the risk of meningioma. However, new epidemiological studies should be conducted in order to confirm these associations and to refine the role of hormonal factors in brain etiology.

Reproductive factors and exogenous hormone use and risk of adult glioma in women in the NIH-AARP Diet and Health Study

Experimental evidence suggests that estrogen and other steroid hormones may protect against glioma. Although epidemiologic studies provide only weak support for a role of exogenous or endogenous hormones in gliogenesis, few cohort studies have addressed this question. The authors, therefore, examined the association between menstrual and reproductive factors, exogenous hormone use, and glioma risk among 225,355 women aged 50-71 years who completed the baseline questionnaire in the NIH-AARP Diet and Health Study. During 7.5 years of follow-up, 174 cases of incident, primary glioma were ascertained. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for exposures, taking potential confounders into account. Older age at menarche was positively associated with risk: HR 1.67 (95% CI: 1.03, 2.69). Other reproductive factors, including age at first live birth, parity, age at menopause, type of menopause (natural vs. medical) and exogenous hormone use showed no association with glioma risk. The results were similar when the analysis was restricted to cases with glioblastoma (N = 130). The present study provides only limited support for the hypothesis that menstrual/reproductive factors or exogenous hormone use play a role in gliogenesis.

Progesterone and estradiol effects on SRC-1 and SRC-3 expression in human astrocytoma cell lines

Progesterone (P(4)) and estradiol (E(2)) regulate many cell functions through their interaction with specific intracellular receptors, which require the participation of coactivators such as SRC-1 and SRC-3 for enhancing their transcriptional activity. Coactivator expression is altered in many cancers and in some of them their expression is regulated by P(4) and E(2). In this study, we determined progesterone and estrogen receptor isoform expression in two human astrocytoma cell lines with different evolution grade (U373, grade III; and D54, grade IV) by Western Blot. We studied the role of P(4) and E(2) on SRC-1 and SRC-3 expression in U373 and D54 cell lines by RT-PCR and Western blot. In U373 cells, P(4) did not modify SRC-1 expression, but in D54 cells it increased SRC-1 mRNA expression after 12 h of treatment without significant changes after 24 h. P(4) also increased SRC-1 protein content after 24 h, but reduced it after 48 h. E(2) did not change SRC-1 expression in any cell line. SRC-3 expression was not regulated by either E(2) or P(4). Our data suggest that SRC-1 and SRC-3 expression is differentially regulated by sex steroid hormones in astrocytomas and that P(4) regulates SRC-1 expression depending on the evolution grade of human astrocytoma cells.

Expression of estrogen and progesterone receptors in vestibular schwannomas and their clinical significance

Objective

The objective was to determine the expression of estrogen and progesterone receptors in vestibular schwannomas as well as to determine predictive factors for estrogen and progesterone receptor positivity.

Materials and methods

The study included 100 cases of vestibular schwannomas operated from January 2006 to June 2009. The clinical details were noted from the medical case files. Formaldehyde-fixed parafiin-embedded archival vestibular schwannomas specimens were used for the immunohistochemical assessment of estrogen and progesterone receptors.

Results

Neither estrogen nor progesterone receptors could be detected in any of our cases by means of well known immunohistochemical method using well documented monoclonal antibodies. In the control specimens, a strongly positive reaction could be seen.

Conclusion

No estrogen and progesterone receptor could be found in any of our 100 cases of vestibular schwannomas. Hence our study does not support a causative role of estrogen and progesterone in the growth of vestibular schwannoma as well as hormonal manipulation in the treatment of this tumor.

Expression of corticosteroid-binding globulin in human astrocytoma cell line

Glial tumor cells are known to be sensitive to glucocorticoids (GC) in vivo and in vitro. Here we studied the expression of corticosteroid-binding globulin (CBG) in the low-grade malignant human astrocytoma cell line 1321N1. CBG was observed in cytoplasm of most of these cells with immunocytochemistry. RT-PCR revealed the presence of the respective mRNA. Only scattered cells contained nuclear immunoreactivity for glucocorticoid receptor as visualized by double immunostaining. Immunoreactive CBG could be recovered from the supernatant of cultures that had been exposed to 10(-5) M cortisol. Our observations indicate the endogenous expression of CBG in 1321N1 cells which may occur independently from classical glucocorticoid receptor pathways. Cortisol seems to facilitate liberation of CBG in a paracrine manner, perhaps through membrane action of the steroid. Effects of adrenal steroids on proliferation and apoptosis of certain glial tumors may in part depend on these mechanisms.

Regulation of progesterone receptor isoforms content in human astrocytoma cell lines

Progesterone regulates several functions through the interaction with its intracellular receptor (PR) which expresses two isoforms with different functions and regulation: PR-A and PR-B. Both PR isoforms have been detected in human astrocytomas, the most common and aggressive primary brain tumours, but their regulation and function are unknown. We studied the effects of estradiol, progesterone and their receptor antagonists (ICI 182,780 and RU 486) on PR isoforms content in U373 and D54 human astrocytoma cell lines, respectively derived from grades III and IV astrocytomas, by Western blot analysis. In U373 cells we also evaluated the effects of PR-A overexpression on cell growth. We observed that in U373 cells estradiol increased the content of both PR isoforms whereas in D54 cells it had no effects. Estradiol effects were blocked by ICI 182,780. In both cell lines, PR isoforms content was down-regulated by progesterone after estradiol treatment. This effect was blocked by RU 486. We observed that overexpression of PR-A significantly diminished the increase in U373 cells number produced after progesterone treatment. Our results suggest a differential PR isoforms regulation depending on the evolution grade of human astrocytoma cells, and an inhibitory role of PR-A on progesterone effects on astrocytomas cell growth.

Progesterone effects on cell growth of U373 and D54 human astrocytoma cell lines

Astrocytomas are the most frequent primary brain tumors and constitute a leading cause of cancer-related deaths. We studied the effects of progesterone and its antagonist, RU486, on cell growth of two human astrocytoma cell lines with different evolution grade (U373, grade III; and D54, grade IV). Progesterone receptor expression was determined by Western blot. The effects of different doses of progesterone and RU486 on cell number, cell cycle, and apoptosis were analyzed for five consecutive days. Progesterone (10 nM) significantly increased the number of D54 cells from the second day of culture, and the number of U373 cells on days 3-5. RU486 (10 muM) blocked progesterone effects in both astrocytoma cell lines. Interestingly, RU486 administered without progesterone significantly reduced the number of cells from the second day of culture in both cell lines. Progesterone increased S phase of cell cycle in U373 cells (61%, on day 5). RU486 blocked the effects of progesterone on cell cycle but administered alone did not significantly change cell cycle profile. DNA fragmentation (TUNEL) assay showed that the diminution in the number of astrocytoma cells produced by RU486 was not by apoptosis. Progesterone receptor isoforms were detected in both cell lines. Our data suggest that progesterone induces cell growth of human astrocytoma cell lines through the interaction with its nuclear receptor.