MMQ Cells Research Articles

The Wnt/β-catenin signaling pathway is involved in the antitumor effect of fulvestrant on rat prolactinoma MMQ cells

Although an antiestrogen treatment for estrogen-dependent diseases, such as breast cancers, has been reported, the effect of this endocrine therapy on prolactinomas and its possible mechanism are unclear. This study investigates the antitumor effect of fulvestrant, which is a new estrogen receptor antagonist, on rat prolactinoma MMQ cells and the possible roles of the Wnt/β-catenin signaling pathway that is involved in this antitumor effect. To investigate the antitumor effect of fulvestrant, the effects of exposure to gradient doses of fulvestrant (0, 0.04, 1, 25, and 625 nM) on the proliferation of cells and the secretion of prolactin (PRL) were studied. Then, the expression levels of the Wnt/β-catenin signaling pathway-related proteins β-catenin and Wnt inhibitory factor-1 (WIF-1) were measured to investigate their possible roles in the antitumor effect of fulvestrant. The cells were also treated with decitabine (10 μM) to investigate the epigenetic mechanism of WIF-1 expression. The proliferation of MMQ cells and the secretion of PRL were suppressed by fulvestrant in a dose-dependent manner (up to 57.0 ± 3.9 % and 51.2 ± 4.9 %, respectively). β-Catenin expression was downregulated and was positively correlated with ER-α expression (P<0.01). As a tumor suppressor, WIF-1 expression was upregulated and was negatively correlated with ER-α expression (P<0.01). Furthermore, WIF-1 expression was upregulated via the hypomethylation of the promoter by decitabine, and cellular proliferation was correspondingly suppressed (37.8 ± 4.3 %). Antitumor effect of fulvestrant was partially disrupted by SB 216763 via activation of the Wnt/β-catenin pathway. In conclusion, through the Wnt/β-catenin signaling pathway, fulvestrant can suppress the proliferation of MMQ cells and the secretion of PRL.

MicroRNA-200c Inhibits Apoptosis in Pituitary Adenoma Cells by Targeting the PTEN/Akt Signaling Pathway

MicroRNAs (miRNAs) are important regulators that are involved in the development of different types of tumors. MicroRNA-200c (miR-200c) has been characterized as a tumor suppressor or oncogene in different cancers. However, the role of miR-200c in pituitary tumorigenesis remains unknown. We observed that miR-200c was overexpressed in pituitary adenoma cell lines. We transfected a miR-200c inhibitor into pituitary adenoma cells (MMQ cell line) to inhibit miR-200c expression and found that the percentage of apoptotic MMQ cells increased. Using bioinformatics analyses, we predicted that the tumor suppressor gene PTEN was targeted by miR-200c, and we confirmed the presence of a functional miR-200c binding site in the 3'-UTR of PTEN using luciferase reporter assays. We determined that the inhibition of miR-200c expression can upregulate PTEN expression and decrease the expression of phosphorylated Akt (p-Akt). Furthermore, the siRNA-mediated knockdown of PTEN abrogated the effect of inhibiting miR-200c expression. Taken together, these findings suggest that miR-200c regulates pituitary tumor formation through the PTEN/Akt signaling pathway. Therefore, we propose that the inhibition of miR-200c could have therapeutic potential in pituitary adenoma.

Water Extract of Fructus Hordei Germinatus Shows Antihyperprolactinemia Activity via Dopamine D2 Receptor.

Objective. Fructus Hordei Germinatus is widely used in treating hyperprolactinemia (hyperPRL) as a kind of Chinese traditional herb in China. In this study, we investigated the anti-hyperPRL activity of water extract of Fructus Hordei Germinatus (WEFHG) and mechanism of action. Methods. Effect of WEFHG on serum prolactin (PRL), estradiol (E2), progesterone (P), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and hypothalamus protein kinase A (PKA) and cyclic adenosine monophosphate (cAMP) levels of hyperPRL rats were investigated. And effect of WEFHG on PRL secretion, D2 receptors, and dopamine transporters (DAT) was studied in MMQ, GH3, and PC12 cells, respectively. Results. WEFHG reduced the secretion of PRL in hyperPRL rats effectively. In MMQ cell, treatment with WEFHG at 1–5 mg/mL significantly suppressed PRL secretion and synthesis. Consistent with a D2-action, WEFHG did not affect PRL in rat pituitary lactotropic tumor-derived GH3 cells that lack the D2 receptor expression but significantly increased the expression of D2 receptors and DAT in PC12 cells. In addition, WEFHG reduced the cAMP and PKA levels of hypothalamus in hyperPRL rats significantly. Conclusions. WEFHG showed anti-hyperPRL activity via dopamine D2 receptor, which was related to the second messenger cAMP and PKA.

GAL3 Protein Expression is Related to Clinical Features of Prolactin-Secreting Pituitary Microadenoma and Predicts its Recurrence after Surgical Treatment

Background: Previous in vitro study showed that Galectin-3 (Gal-3) protein plays an important role in pituitary tumorigenesis, however, the association of Gal-3 expression with the clinical feature and prognosis of pituitary tumor in a clinical setting remains unknown. Methods: We enrolled 220 patients with prolactin-secreting pituitary adenomas (PA) who previously had transsphenoidal pituitary surgery. The Gal-3 expression was detected in the patients' PA samples using immunohistochemistry and those patients were followed up. A prolactin-secreting PA cell line, the MMQ cell line, was used to study the in vitro effect of Gal-3 on proliferation, migration and invasion of PA cells using small interfering RNA (siRNA) transfecton technique. The in vivo tumorgenesis in nude mice was also studied. Results: We found that Gal-3 expression was not related to age and sex, but positively associated with tumor invasion (P<0.001), tumor sizes (P<0.001) and pre-operative prolactin levels (P<0.001). The multivariate Cox analysis showed that the Gal-3 expression was closely associated with the recurrence of PA after the surgical treatment (HR =3.15, P=0.002). The in vitro studies showed that Gal-3 knock-down by the siRNA technique significantly inhibited the proliferation, migration and invasion ability of the MMQ cells, whereas Gal-3 siRNA transfection induced apoptosis of the MMQ cells. The in vivo tumorgenesis assay showed that Gal-3 siRNA transfection significantly inhibited the tumor volume in vivo compared to transfection of the control siRNA (P<0.001). Conclusion: Gal-3 regulates proliferation, apoptosis, migration and invasion of the MMQ cells. Gal-3 may be used as a tissue marker to evaluate the clinical feature and prognosis of PA patients.

Liquiritigenin exhibits antitumour action in pituitary adenoma cells via Ras/ERKs and ROS-dependent mitochondrial signalling pathways

The purpose of this study was to investigate antitumour effects of liquiritigenin (LQ) on pituitary adenoma in in-vitro and in-vivo models. The effects of LQ on cell viability, apoptosis rate, mitochondrial membrane potential (MMP), intracellular reactive oxygen species (ROS) level and various apoptosis-related mediators were examined in MMQ and GH3 cells that are derived from rat pituitary adenoma. Antitumour effect of LQ was also examined in the mouse model of GH3-xenografted tumour. LQ inhibited cell viability, caused G1 phase arrest and initiated apoptosis in both MMQ and GH3 cells. LQ dissipated MMP, increased intracellular ROS level and cytosol cytochrome C, and reduced the expression of Ras, B-cell lymphoma 2 and B-cell lymphoma-extra large. LQ also inhibited the activation of extracellular signalling-regulated kinases (ERKs) and the translocation of from cytoplasm to nucleus. LQ markedly reduced tumour size without affecting bodyweight in mice with GH3 cells xenograft. LQ effectively inhibits pituitary adenoma tumour growth and induces cell apoptotic death mainly via Ras/ERKs and ROS-dependent mitochondrial pathways, suggesting that LQ is a potential suppressor of pituitary adenoma.

18beta-Glycyrrhetinic acid induces apoptosis in pituitary adenoma cells via ROS/MAPKs-mediated pathway

The purpose of the present study was to evaluate the anti-tumor effects of 18beta-glycyrrhetinic acid (GA), a natural compound extracted from liquorice, against pituitary adenoma and its underlying mechanisms in cultured cells and mouse model of xenografted tumor. GA induced cellular damage in rat pituitary adenoma-derived MMQ and GH3 cells, manifested as reduced cell viability, increased lactate dehydrogenase release, elevated intracellular reactive oxygen species (ROS) and Ca(2+) concentration. GA also caused G0/G1 phase arrest, increased apoptosis rate and increased mitochondrial membrane permeabilization by suppressing the mitochondrial membrane potential and down-regulating a ratio of B cell lymphoma 2 (Bcl-2) and Bax. GA activated calcium/calmodulin-dependent protein kinase II (CaMKII), c-Jun N-terminal kinase (JNK) and P38; but these activating effects were attenuated by pretreatment with N-acetyl-L-cysteine, a ROS inhibitor. Pretreatment with KN93, a CaMKII inhibitor, also abolished the GA activation of JNK and P38. GA remarkably inhibited growth of pituitary adenoma grafted on nude mice. These results suggest that the anti-pituitary adenoma effect of GA is associated with its apoptotic actions by activating mitochondria-mediated ROS/mitogen-activated protein kinase pathways in particular CaMKII that may serve a linkage between ROS accumulation and the activation of JNK and P38. This study provides experimental evidence in the support of further developing GA as a chemotherapeutic agent for pituitary adenoma.

Inhibitory effects of fulvestrant on the growth of estrogen-induced prolactinoma in Fischer 344 rats and its possible mechanism

Background: Prolactinoma is an estrogen-related tumor, and some anti-estrogen agents have suppressive effects on prolactinoma. Previous studies have suggested that fulvestrant, a selective estrogen receptor antagonist, has /INS;inhibitory effects on the proliferation and prolactin secretion of MMQ and GH3 cells in vitro. However, there is still limited evidence of the inhibitory effects of fulvestrant on prolactinoma in vivo.

A Novel Marine Drug, SZ-685C, Induces Apoptosis of MMQ Pituitary Tumor Cells by Downregulating miR-200c

We found a novel marine drug, SZ-685C, that was isolated from the secondary metabolites of a mangrove endophytic fungus (No. 1403) collected from the South China Sea, which has been reported to inhibit the proliferation of certain tumor cells. However, its anticancer mechanism remains unknown. The aims of this study were to observe the effectiveness of SZ-685C on pituitary adenoma cells and determine the underlying mechanisms of action. A rat prolactinoma cell line, MMQ, was used in this study. A dose escalation of SZ-685C was performed on this cell line, and cell viability was assessed using an MTT assay. Hoechst 33342, Annexin V-FITC/PI, TUNEL staining and flow cytometry were used to evaluate the extent of apoptosis at each concentration of SZ-685C. The effect of SZ-685C on prolactin expression was also evaluated using RT-PCR and immunoblotting. Quantitative RT-PCR was used to detect the expression of miR-200c in SZ-685C-stimulated MMQ cells and pituitary adenoma tissues. This miRNA was then overexpressed in MMQ cells via transfection of a miR-200c mimic to identify the mechanism underling the anti-tumor effect of SZ-685C. SZ-685C inhibited MMQ cell growth in a dose-dependent manner but showed little toxicity toward rat pituitary cells (RPCs). The IC50s of SZ-685C in MMQ cells and RPCs were 13.2 ± 1.3 mM and 49.1 ± 11.5 mM, respectively, which was statistically significant. Increasing numbers of apoptotic cells were observed in response to escalating concentrations of SZ-685C, and the expression level of prolactin (PRL) was inhibited. Nevertheless, the level of PRL mRNA was unchanged. Additionally, miR-200c was upregulated in MMQ cells compared with RPCs, and downregulation of miR- 200c was observed in SZ-685C-treated MMQ cells. Furthermore, the overexpression of miR-200c weakened the effect of SZ-685C-induced apoptosis of MMQ cells. Our results suggest that SZ-685C induces MMQ cell apoptosis in a miR-200c-dependent manner. Therefore, SZ-685C might be a useful alternative treatment for pituitary adenoma.

Suppression of MMQ cells by fulvestrant: possible mechanism of action and potential application for bromocriptine-resistant prolactinomas

Bromocriptine is an effective treatment for most prolactinomas. Estrogen receptor (ER) antagonists are an alternative for treating patients with bromocriptine-resistant prolactinomas (BCRP). Previously, we reported that fulvestrant, a selective ER antagonist, significantly inhibited the proliferation of, and prolactin secretion by, MMQ cells, a prolactin-secreting rat pituitary cell line, an exemplary model for prolactinoma. In this study, we used fulvestrant to block ERα expression by MMQ cells and analyzed the expression of β-catenin and Wnt inhibitory factor-1 (WIF1) to investigate the effects of fulvestrant on the Wnt signaling pathway. In addition, we examined the gene expression of ERα, β-catenin and WIF1 in clinical BCRP specimens to explore the correlation between gender and clinical features. There was no significant difference in β-catenin expression between fulvestrant-treated cells and untreated cells, whereas WIF1 expression was higher in the treated cells. In clinical BCRP specimens, ERα expression was higher (especially in male patients), whereas β-catenin expression was similar to normal pituitaries. In addition, WIF1 expression was significantly lower in BCRP specimens than in normal pituitaries. The tumor volume was larger in male patients than in female patients. Prolactin concentration was positively correlated with tumor volume, and a positive linear correlation was observed between ERα expression and tumor volume. In conclusion, the anti-tumor activity of fulvestrant on MMQ cells seems to be associated with ERα and the non-canonical Wnt pathway, and higher ERα levels in male patients with BCRP may contribute to the larger tumor volumes observed. Fulvestrant holds promise as a therapeutic agent for BCRP.

Not only dopamine D2 receptors involved in Peony-Glycyrrhiza Decoction, an herbal preparation against antipsychotic-associated hyperprolactinemia

Clinical studies have demonstrated the effectiveness of an herbal preparation called Peony-Glycyrrhiza Decoction (PGD) in alleviating antipsychotic-induced hyperprolactinemia (hyperPRL). In the present study, we further examined the pharmacological action of PGD on prolactin (PRL) secretion using in vitro and in vivo models, with specific attention to the role of dopaminergic mediators and other sex hormones. Treatment with PGD at 1-5mg/ml significantly suppressed PRL secretion and synthesis in MMQ cells, a model of hyperPRL derived from pituitary adenoma cells. The suppressive effects were completely abolished by pretreatment with 10μM haloperidol, a dopamine D(2) receptor antagonist. Consistent with a D(2)-action, PGD did not affect PRL in rat pituitary lactotropic tumor-derived GH3 cells that lack the D(2) receptor expression but significantly increased the expression of D(2) receptors and dopamine transporters (DAT) in PC12 cells. In a rat model of hyperPRL, produced by repeated injection of the dopamine blocker metoclopramide (MCP), chronic PGD (2.5-10g/kg daily) significantly reduced elevated serum PRL. The reduction in magnitude was similar to that elicited by bromocriptine (BMT), a dopamine D(2) receptor agonist currently used for treatment of hyperPRL. Neither PGD nor BMT altered serum estradiol, but PGD reversed decreased serum progesterone to control level, whereas BMT did not. These results indicate that the anti-hyperPRL effects of PGD are associated not only with D(2) receptor and DAT modulation, but also with a normalization of other sex hormone dysfunction. This experimental evidence supports clinical use of PGD as an effective treatment of antipsychotic-induced hyperPRL.

Filamin-A Is Essential for Dopamine D2 Receptor Expression and Signaling in Tumorous Lactotrophs

Dopamine agonists (DA) are the first choice treatment of prolactinomas. However, a subset of patients is resistant to DA, due to undefined dopamine D2 receptor (D2R) alterations. Recently, D2R was found to associate with filamin-A (FLNA), a widely expressed cytoskeleton protein with scaffolding properties, in melanoma and neuronal cells. The aim of the study was to investigate the role of FLNA in D2R expression and signaling in human tumorous lactotrophs and rat MMQ and GH3 cells. We analyzed FLNA expression in a series of prolactinomas by immunohistochemistry and Western blotting. We performed FLNA silencing or transfection experiments in cultured cells from DA-sensitive or -resistant prolactinomas and in MMQ and GH3 cells, followed by analysis of D2R expression and signaling. We demonstrated reduced FLNA and D2R expression in DA-resistant tumors. The crucial role of FLNA on D2R was demonstrated by experiments showing that: 1) FLNA silencing in DA-sensitive prolactinomas resulted in 60% reduction of D2R expression and abrogation of DA-induced inhibition of prolactin release and antiproliferative signals, these results being replicated in MMQ cells that endogenously express FLNA and D2R; and 2) FLNA overexpression in DA-resistant prolactinomas restored D2R expression and prolactin responsiveness to DA, whereas this manipulation was ineffective in GH3 cells that express FLNA but not D2R. No alteration in FLNA promoter methylation was detected, ruling out the occurrence of epigenetic FLNA silencing in DA-resistant prolactinomas. These data indicate that FLNA is crucial for D2R expression and signaling in lactotrophs, suggesting that the impaired response to DA may be related to the reduction of FLNA expression in DA-resistant prolactinomas.

Erythropoietin promotes the growth of pituitary adenomas by enhancing angiogenesis

rhEPO is frequently used in clinical practice to treat anemia. However, recently rhEPO has been reported to accelerate tumor growth, progression and metastasis. Many pituitary adenoma patients, particularly those with macroprolactinomas, tend to have anemia and may need rhEPO therapy. To date, whether rhEPO has deleterious effects on pituitary adenomas has not been defined. Here we demonstrated for the first time that human pituitary adenomas are EPOR negative tumors and rhEPO accelerated the tumor growth of MMQ pituitary adenoma xenografts via enhancement of angiogenesis in vivo, whereas rhEPO displayed no direct effect on MMQ cells in vitro. Our mechanistic study showed that rhEPO administration increased phosphorylation of JAK2, STAT3 and VEGF expression in human umbilical vein endothelial cells (HUVECs) in vitro and in MMQ cell xenografts in vivo. Furthermore, VEGF inhibitor attenuated rhEPO induced angiogenesis and delayed tumor growth in MMQ pituitary adenoma xenografts in vivo. JAK2 inhibitor AG490 attenuated EPO induced HUVECs proliferation, phosphorylation of JAK2, STAT3 and VEGF upregulation in vitro and inhibited EPO induced vessel formation in Chicken chorioallantoic membrane (CAM) angiogenesis model in vivo. These results suggest that rhEPO administration may promote the growth of pituitary adenomas by enhancing angiogenesis through EPO-JAK2-STAT3-VEGF signaling pathway. rhEPO should be used with caution in anemia patients bearing pituitary adenoma due to its potential deleterious effects.

Effects of an estrogen receptor antagonist on proliferation, prolactin secretion and growth factor expression in the MMQ pituitary prolactinoma cell line

The aim of this study was to investigate the functional role of estrogen receptor α (ERα) in MMQ pituitary prolactinoma cells in the absence of estrogen with respect to proliferation, prolactin (PRL) secretion, and expression of growth factors. MMQ cells were treated with the ERα antagonist fulvestrant, then proliferation and PRL secretion were measured using MTS and enzyme-linked immunosorbent assays. Levels of ERα, vascular endothelial growth factor (VEGF), matrix metalloproteinase-9 (MMP-9) and B cell leukemia/lymphoma-2 (BCL-2) were measured using quantitative polymerase chain reaction and western blot analysis. Fulvestrant acted as a potent inhibitor of ERα expression, and significantly inhibited cell proliferation (by up to 57.6 ± 2.2%) and PRL secretion (by up to 81.0%). Fulvestrant also significantly altered the expression levels of VEGF, MMP-9 and BCL-2. We conclude that ERα plays an important functional role in pituitary prolactinomas and is also involved in the expression of particular growth factors, even in the absence of estrogen. Fulvestrant treatment may be an effective therapy for such tumors.

Hypoxia induces hemorrhagic transformation in pituitary adenomas via the HIF-1α signaling pathway

The hypoxia inducible factor 1 α (HIF-1α) activity has been associated with various hemorrhagic events. The biological role of HIF-1α in the hemorrhagic transformation of pituitary adenomas remains unknown. We hypothesized that fast growing tumor cells tend to predispose themselves to sublethal hypoxia and activate the HIF-1α signaling pathway, leading to hemorrhagic transformation in pituitary adenomas. Here, we used apoplectic and non-apoplectic pituitary adenomas to determine the involvement of HIF-1α signaling in intratumoral hemorrhage. We employed HIF-1α overexpression/knockdown strategies to examine the association between HIF-1α signaling and hemorrhagic presentation invitro and invivo. In support of our hypothesis, compared with non-hemorrhagic pituitary adenomas, higher cellular proliferation was observed in hemorrhagic ones and it correlated with increased HIF-1α signaling. HIF-1α overexpression activated its downstream genes, vascular endothelial growth factor and the proapoptotic BNIP3, in MMQ pituitary adenoma cells and this up-regulation was attenuated by HIF-1 siRNA. Invivo studies using MMQ cell xenografts in nude mice showed that HIF-1α overexpression significantly promoted hemorrhagic transformation. Our study indicates that tumor hypoxia, following rapid tumor growth, may promote hemorrhagic transformation in pituitary adenomas via the HIF-1α signaling pathway.

Regulatory Roles of Heterogeneous Nuclear Ribonucleoprotein M and Nova-1 Protein in Alternative Splicing of Dopamine D2 Receptor Pre-mRNA

The dopamine D2 receptor (D2R) plays a crucial role in the regulation of diverse key physiological functions, including motor control, reward, learning, and memory. This receptor is present in vivo in two isoforms, D2L and D2S, generated from the same gene by alternative pre-mRNA splicing. Each isoform has a specific role in vivo, underlining the importance of a strict control of its synthesis, yet the molecular mechanism modulating alternative D2R pre-mRNA splicing has not been completely elucidated. Here, we identify heterogeneous nuclear ribonucleoprotein M (hnRNP M) as a key molecule controlling D2R splicing. We show that binding of hnRNP M to exon 6 inhibited the inclusion of this exon in the mRNA. Importantly, the splicing factor Nova-1 counteracted hnRNP M effects on D2R pre-mRNA splicing. Indeed, mutations of the putative Nova-1-binding site on exon 6 disrupted Nova-1 RNA assembly and diminished the inhibitory effect of Nova-1 on hnRNP M-dependent exon 6 exclusion. These results identify Nova-1 and hnRNP M as D2R pre-mRNA-binding proteins and show their antagonistic role in the alternative splicing of D2R pre-mRNA.

MTOR inhibition reduces cellular proliferation and sensitizes pituitary adenoma cells to ionizing radiation

Background:Pituitary adenomas are the most frequent brain tumor in adults. Although histologically benign, pituitary tumors cause significant morbidity and mortality. Neurosurgery and medical therapeutics may lessen the morbidity and mortality associated with pituitary tumors; however, these treatments are associated with significant adverse side effects. Thus, an improved understanding of pituitary adenomas at the molecular and cellular level is needed to design novel therapeutic compounds.Methods:To assess the effect of mammalian target of rapamycin (mTOR) inhibition on pituitary adenoma cells, rat GH3 or MMQ cells were treated with the clinically useful mTOR inhibitors, rapamycin or RAD001. Cellular proliferation and growth following exposure to mTOR inhibitors or radiation were assessed using biochemical methods.Results:In the present study, we observed basal activation of mTOR, downstream of constitutive Akt signaling, in rat GH3 adenoma cells. Functionally, the mTOR inhibitors, rapamycin and RAD001 (500 pM–5 nM), induced G1 growth arrest within 24 hours, an effect associated with reduced cellular proliferation. Both rapamycin and RAD001 decreased the phosphorylation of mTOR at the serine 2448, a key determinant of mTOR activity. Inhibition of mTOR also radiosensitized GH3 cells such that 2.5 Gy in combination with 500 pM rapamycin or RAD001 reduced cellular viability more effectively than 2.5 or 10 Gy alone.Conclusions:These data may support a possible therapeutic role for mTOR inhibitors in limiting the cellular proliferation and radioresistance of pituitary adenoma cells.

Reversal of Endogenous Dopamine Receptor Silencing in Pituitary Cells Augments Receptor-Mediated Apoptosis

Dopamine (DA)-agonist targeting of the DA D(2) receptor (D2R) in prolactinomas is the first-line treatment choice for suppression of prolactin and induction of tumor shrinkage. Resistance to DA agonists seems to be related to receptor number. Using the MMQ and GH3 pituitary cell lines, that either do or do not express D2R, respectively, we explored the epigenetic profile associated with the presence or absence of D2R in these cells lines. These studies led us to explore pharmacological strategies designed to restore receptor expression and thereby potentially augment DA agonist-mediated apoptosis. We show in GH3 cells that the D2R harbors increased CpG island-associated methylation and enrichment for histone H3K27me3. Conversely, MMQ cells and normal pituitaries show enrichment for H3K9Ac and barely detectable H3K27me3. Coculture of GH3 cells with the demethylating agent zebularine and the histone deacetylase inhibitor trichostatin A was responsible for a decrease in CpG island methylation and enrichment for the histone H3K9Ac mark. In addition, challenge of GH3 cells with zebularine alone or coculture with both agents led to expression of endogenous D2R in these cells. Induced expression D2R in GH3 cells was associated with a significant increase in apoptosis indices to challenge with either DA or bromocriptine. Specificity of a receptor-mediated response was established in coincubations with specific D2R antagonist and siRNA approaches in GH3 cell and D2R expressing MMQ cell lines. These studies point to the potential efficacy of combined treatment with epigenetic drugs and DA agonists for the medical management of different pituitary tumor subtypes, resistant to conventional therapies.

Isolation and Antimicrobial Activity of Lectin from Schinus terebinthifolius Leaves

Prolactinomas are the most common functional pituitary adenomas. While dopamine agonists are a primary method of therapeutic treatment, the rate of resistance to these drugs continues to increase each year. During previous long-term clinical investigations, we found that partial resistant prolactinomas exhibited significantly more fibrosis than did sensitive adenomas, suggesting a role of fibrosis in their drug resistance. Furthermore, resistant adenomas with extensive fibrosis mainly express type I and type III collagens. Since TGF-β1 is the key factor in the initiation and development of tissue fibrosis, including in the pituitary, in this study, we aimed to determine whether TGF-β1 mediated fibrosis in prolactinomas and whether fibrosis was related to prolactinoma drug resistance. Using immunochemistry and western blotting, we found that the TGF-β1/Smad3 signaling pathway-related proteins were elevated in resistant prolactinoma specimens with high degrees of fibrosis compared to levels in sensitive samples, suggesting that this pathway may play a role in prolactinoma fibrosis. In vitro, TGF-β1 stimulation promoted collagen expression in normal HS27 fibroblasts. Furthermore, the sensitivity of rat prolactinoma MMQ cells to bromocriptine decreased when they were co-cultured with HS27 cells treated with TGF-β1. The TGF-β1/Smad3 signaling-specific inhibitor SB431542 counteracted these effects, indicating that TGF-β1/Smad3-mediated fibrosis was involved in the drug-resistant mechanisms of prolactinomas. These results indicate that SB431542 may serve as a promising novel treatment for preventing fibrosis and further improving the drug resistance of prolactinomas.

Effects of estrogen receptor antagonist on biological behavior and expression of growth factors in the prolactinoma MMQ cell line

The relationship between estrogen and pituitary prolactinoma is well documented. The biological effects of estrogen are mainly mediated by estrogen receptorα (ERα). Several lines of evidence demonstrate that growth factors such as pituitary tumor transforming gene (PTTG), basic fibroblast growth factor (bFGF), transforming growth factorβ1 (TGFβ1), transforming growth factorβ3 (TGFβ3), and transforming growth factorβ receptor typeII (TGFβRII) play an important role in prolactinoma pathogenesis induced by estrogen, but the relationship between ERα and such growth factors is still unclear. The aims of this study are to investigate the functional role of ERα in proliferation, prolactin (PRL) secretion, and expression of the above-mentioned growth factors in MMQ cells in the absence of estrogen and to discuss the feasibility of using an estrogen receptor antagonist to treat prolactinoma. Fulvestrant, a "pure" antiestrogen without any estrogen-like activity, was used to block expression of ERα in the MMQ cell line. Proliferation and PRL secretion of MMQ cells were measured using CellTiter 96(®) AQueous One Solution Cell Proliferation Assay (MTS) and the enzyme-linked immunosorbent assay (ELISA) method. Levels of ERα, PTTG, bFGF, TGFβ1, TGFβ3, and TGFβRII were analyzed by real-time polymerase chain reaction (PCR) and Western blot. Fulvestrant significantly inhibited cell proliferation (up to 60.80%) and PRL secretion (up to 77.95%), and changed expression of TGFβ3 and TGFβRII in the absence of estrogen. In conclusion, ERα plays an important functional role in proliferation and PRL secretion of pituitary prolactinomas and also can change expression of some growth factors even under the condition of no estrogen. Fulvestrant could potentially be an effective therapy for treating such tumors.

Temozolomide-induced inhibition of pituitary adenoma cells

Aggressive pituitary adenomas frequently require multimodality treatment including pituitary-suppressive medications, microsurgery, and radiation therapy or radiosurgery. The effectiveness of temozolomide in terms of growth suppression and decreased hormonal production is evaluated. Three pituitary adenoma cell lines--MMQ, GH3, and AtT20--were used. A dose escalation of temozolomide was performed for each cell line, and inhibition of cell proliferation was assessed using an MTT assay. Concentrations of temozolomide that produced statistically significant inhibition of cell proliferation for each cell type were identified. Extent of apoptosis for each selected temozolomide concentration was studied using TUNEL staining. The effect of temozolomide on prolactin secretion in MMQ and GH3 cells was also measured via ELISA. Significant inhibition of cell proliferation was noted for MMQ and GH3 cells at a concentration of 250 μM temozolomide. The AtT20 cells demonstrated statistically significant cell inhibition at a concentration of only 50 μM temozolomide (p < 0.05). Apoptosis significantly increased in all cell lines in as little as 24 hours of incubation at the respective temozolomide concentrations (p < 0.05). Prolactin secretion in the prolactin secreting MMQ and GH3 cell lines was inhibited by 250 μM temozolomide. Temozolomide inhibits cell proliferation and induces apoptotic cell death in aggressive pituitary adenoma cells. A reduction in hormonal secretion in prolactinoma cells was also afforded by temozolomide. Temozolomide may prove useful in the multimodality management of aggressive pituitary adenomas.