Fibroblast growth factor-2 in hyperplastic pituitaries of D2R knockout female mice

Regulation of FGF2-induced proliferation by inhibitory GPCR in normal pituitary cells

Introduction

Intracellular communication is essential for the maintenance of the anterior pituitary gland plasticity. The aim of this study was to evaluate whether GPCR-Gαi modulates basic fibroblast growth factor (FGF2)-induced proliferative activity in normal pituitary cell populations.

Methods

Anterior pituitary primary cell cultures from Wistar female rats were treated with FGF2 (10ng/mL) or somatostatin analog (SSTa, 100nM) alone or co-incubated with or without the inhibitors of GPCR-Gαi, pertussis toxin (PTX, 500nM), MEK inhibitor (U0126, 100µM) or PI3K inhibitor (LY 294002, 10 μM).

Results

FGF2 increased and SSTa decreased the lactotroph and somatotroph BrdU uptak2e (p<0.05) whereas the FGF2-induced S-phase entry was prevented by SSTa co-incubation in both cell types, with these effects being reverted by PTX, U0126 or LY294002 pre-incubation. The inhibition of lactotroph and somatotroph mitosis was associated with a downregulation of c-Jun expression, a decrease of phosphorylated (p) ERK and pAKT. Furthermore, SSTa was observed to inhibit the S-phase entry induced by FGF2, resulting in a further increase in the number of cells in the G1 phase and a concomitant reduction in the number of cells in the S phases (p< 0.05), effects related to a decrease of cyclin D1 expression and an increase in the expression of the cell cycle inhibitors p27 and p21.

Discussion

In summary, the GPCR-Gαi activated by SSTa blocked the pro-proliferative effect of FGF2 in normal pituitary cells via a MEK-dependent mechanism, which acts as a mediator of both anti and pro-mitogenic signals, that may regulate the principal effectors of the G1 to S-phase transition.

Tumor suppressor miR-145-5p sensitizes prolactinoma to bromocriptine by downregulating TPT1

PURPOSE

Prolactinoma is the most commonly seen secretory tumor of pituitary glands, which accounts for approximately up to 40% of total pituitary adenomas. Due to its high drug resistance, dopamine agonist, such as bromocriptine, has limited effect on the treatment of patients with prolactinoma. Recent discoveries have revealed that multiple miRNAs were involved in regulating drug resistance. In this research, we explored the relationship between miR-145-5p expression as well as bromocriptine sensitivity both in vitro and in vivo.

METHODS

To study the role of miR-145-5p in drug resistance of prolactinoma, the expression levels of miR-145-5p in bromocriptine-resistant prolactinoma cell line MMQ/BRC and its parental cell line MMQ cells, 24 bromocriptine-resistant as well as eight sensitive clinical samples were measured by qRT-PCR. Moreover, CCK8, flow cytometry and immunofluorescence were performed to identify the biological characteristics of MMQ/BRC and MMQ. TPT1 was predicted as a direct target gene of miR-145-5p by bioinformatic methods. In addition, qRT-PCR, western blot and immunohistochemistry were used to detect the expression level of TPT1 in clinical specimens and cell lines. Xenograft mouse model was constructed to analyze whether miR-145-5p could reverse bromocriptine resistance in prolactinoma in vivo.

RESULTS

In our study, bromocriptine-resistant prolactinoma clinical samples and cell line had decreased miR-145-5p levels and expressed high levels of TPT1 compared with their sensitive counterparts. Bioinformatic methods and our preliminary dual luciferase reporter assay were utilized to elucidate that TPT1 was a direct target gene of miR-145-5p. Furthermore, introducing miR-145-5p mimic into MMQ cells led to a decrease of IC50 along with upregulation of TPT1; nevertheless, transfecting the corresponding inhibitor into MMQ cells resulted in an upregulation of IC50 as well as reduction of TPT1.

CONCLUSIONS

Collectively, our findings elucidated the role of miR-145-5p as an important regulator of drug resistance in prolactinoma by controlling TPT1, and implicated the potential application of miR-145-5p in cancer therapy as well.

The pituitary TGFβ1 system as a novel target for the treatment of resistant prolactinomas

Prolactinomas are the most frequently observed pituitary adenomas and most of them respond well to conventional treatment with dopamine agonists (DAs). However, a subset of prolactinomas fails to respond to such therapies and is considered as DA-resistant prolactinomas (DARPs). New therapeutic approaches are necessary for these tumors. Transforming growth factor β1 (TGFβ1) is a known inhibitor of lactotroph cell proliferation and prolactin secretion, and it partly mediates dopamine inhibitory action. TGFβ1 is secreted to the extracellular matrix as an inactive latent complex, and its bioavailability is tightly regulated by different components of the TGFβ1 system including latent binding proteins, local activators (thrombospondin-1, matrix metalloproteases, integrins, among others), and TGFβ receptors. Pituitary TGFβ1 activity and the expression of different components of the TGFβ1 system are regulated by dopamine and estradiol. Prolactinomas (animal models and humans) present reduced TGFβ1 activity as well as reduced expression of several components of the TGFβ1 system. Therefore, restoration of TGFβ1 inhibitory activity represents a novel therapeutic approach to bypass dopamine action in DARPs. The aim of this review is to summarize the large literature supporting TGFβ1 important role as a local modulator of pituitary lactotroph function and to provide recent evidence of the restoration of TGFβ1 activity as an effective treatment in experimental prolactinomas.

FGFR3 Down-Regulation is Involved in bacillus Calmette-Guérin Induced Bladder Tumor Growth Inhibition

PURPOSE

Bacillus Calmette-Guérin is the standard treatment for patients with nonmuscle invasive high histological grade bladder cancer. Previously we found that bacillus Calmette-Guérin induces murine bladder cancer MB49 cell death in vitro and in vivo, generating tissue remodeling, which involves the release of fibroblast growth factor (FGF)-2.

MATERIALS AND METHODS

We studied the effect of bacillus Calmette-Guérin treatment on FGF-2 and FGF receptor (FGFR) expression in bladder cancer.

RESULTS

In vitro FGF-2 increased MB49 cell proliferation but did not reverse bacillus Calmette-Guérin induced cell death. Increased FGF-2 expression was detected after bacillus Calmette-Guérin treatment. Moreover MB49 cells expressed high FGFR3 levels, which decreased after treatment. Similar results were observed in human T24 bladder cancer cells. In vivo MB49 tumors expressed higher FGFR3 levels than normal urothelium. Tumor FGFR3 decreased after treatment and correlated with tumor growth inhibition in response to bacillus Calmette-Guérin. In a pilot bioassay using 11 human bladder tumors treated ex vivo with bacillus Calmette-Guérin we found a subgroup of 41% of patients in whom FGFR3 was decreased after treatment.

CONCLUSIONS

Based on bladder cancer murine model results we infer that down-regulation of FGFR3 is a predictive marker of a good response to bacillus Calmette-Guérin therapy. The decrease in FGFR3 in response to bacillus Calmette-Guérin occurred not only in a murine model but also in a human bladder cancer cell line and in some patient samples. More patients and increased followup are needed to establish the predictive role of FGFR3 as a marker in human bladder cancer.

Angiogenesis in pituitary adenomas: human studies and new mutant mouse models

The role of angiogenesis in pituitary tumor development has been questioned, as pituitary tumors have been usually found to be less vascularized than the normal pituitary tissue. Nevertheless, a significantly higher degree of vasculature has been shown in invasive or macropituitary prolactinomas when compared to noninvasive and microprolactinomas. Many growth factors and their receptors are involved in pituitary tumor development. For example, VEGF, FGF-2, FGFR1, and PTTG, which give a particular vascular phenotype, are modified in human and experimental pituitary adenomas of different histotypes. In particular, vascular endothelial growth factor, VEGF, the central mediator of angiogenesis in endocrine glands, was encountered in experimental and human pituitary tumors at different levels of expression and, in particular, was higher in dopamine agonist resistant prolactinomas. Furthermore, several anti-VEGF techniques lowered tumor burden in human and experimental pituitary adenomas. Therefore, even though the role of angiogenesis in pituitary adenomas is contentious, VEGF, making permeable pituitary endothelia, might contribute to adequate temporal vascular supply and mechanisms other than endothelial cell proliferation. The study of angiogenic factor expression in aggressive prolactinomas with resistance to dopamine agonists will yield important data in the search of therapeutical alternatives.

Enhanced nestin expression and small blood vessels in human pituitary adenomas

The role of angiogenesis in human pituitary tumor progression is questioned. Our aim was to characterize the morphologic changes that occur in the vasculature of pituitary adenomas, in correlation with the expression of nestin, a protein found in endothelial cells of newly formed vessels of developing organs. We also evaluated the relation of angiogenic markers and nestin with Ki-67 index. Immunohistochemical studies were performed on paraffin embedded samples of 47 pituitary adenomas and six normal pituitaries. We determined microvessel density (number of CD31+ or CD34+ vessels per square millimetre), vascular area (cumulative area occupied by vessels), average vessel size, and further classified vessels as small (< 100 μm2) or large (> 100 μm2). We correlated the above parameters with nestin expression and Ki-67 index. Lower vascular area compared to normal tissue was found in adenomas (p < 0.05). Interestingly, pituitary adenomas had significantly more small vessels than control pituitaries (p < 0.04 for CD31 and CD34). In tumors many capillaries were positive for nestin, while scarce staining was detected in controls, so that nestin positive area was significantly higher in tumors. Furthermore, nestin area correlated positively with the % of small vessels. Ki-67 correlated neither with vascular area nor with nestin expression. In human pituitary tumors there was a predominance of small capillaries in correlation with increased expression of the progenitor marker nestin. We suggest that angiogenesis is an active process in these tumors, in spite of their low total vascular area when compared to normal pituitaries.

Cooperative effect of E₂ and FGF2 on lactotroph proliferation triggered by signaling initiated at the plasma membrane

In the present work, we investigated the effect of 17β-estradiol (E₂) and basic fibroblast growth factor 2 (FGF2) on the lactotroph cell-proliferative response and the related membrane-initiated signaling pathway. Anterior pituitary mixed-cell cultures of random, cycling 3-mo-old female rats were treated with 10 nM E₂, E₂ membrane-impermeable conjugated BSA (E₂-BSA), PPT (ERα agonist), and DPN (ERβ agonist) alone or combined with FGF2 (10 ng/ml) for 30 min or 4 h. Although our results showed that the uptake of BrdU into the nucleus of lactotrophs was not modified by E₂ or FGF2 alone, a significant increase in the lactotroph uptake of BrdU was observed after E₂/FGF2 coincubation, with this effect being mimicked by PPT/FGF2. These proliferative effects were blocked by ICI 182,780 or PD-98059. The involvement of membrane ER in the proliferative response of prolactin cells induced by the steroid and FGF2 coincubation was confirmed using E₂-BSA, and the association between ERα and FGF receptor was observed after E₂/FGF2 treatment by immunoprecipitation. A significant increase in the ERK1/2 expression was noted after E₂, E₂-BSA, PPT, and FGF2 alone, which was more noticeable after E₂-BSA/FGF2, E₂/FGF2, or PPT/FGF2 treatments. This study provides evidence that E₂ and FGF2 exert a cooperative effect on the lactotroph proliferation principally by signaling initiated at the plasma membrane triggering a genomic effect mediated by MEK/ERK1/2, a common signaling pathway, that finally regulates the lactotroph population, thus contributing to pituitary plasticity.

Cellular and molecular specificity of pituitary gland physiology

The anterior pituitary gland has the ability to respond to complex signals derived from central and peripheral systems. Perception of these signals and their integration are mediated by cell interactions and cross-talk of multiple signaling transduction pathways and transcriptional regulatory networks that cooperate for hormone secretion, cell plasticity, and ultimately specific pituitary responses that are essential for an appropriate physiological response. We discuss the physiopathological and molecular mechanisms related to this integrative regulatory system of the anterior pituitary gland and how it contributes to modulate the gland functions and impacts on body homeostasis.

Bacillus Calmette Guerin induces fibroblast activation both directly and through macrophages in a mouse bladder cancer model

BACKGROUND

Bacillus Calmette-Guerin (BCG) is the most effective treatment for non-muscle invasive bladder cancer. However, a failure in the initial response or relapse within the first five years of treatment has been observed in 20% of patients. We have previously observed that in vivo administration of an inhibitor of nitric oxide improved the response to BCG of bladder tumor bearing mice. It was described that this effect was due to a replacement of tumor tissue by collagen depots. The aim of the present work was to clarify the mechanism involved in this process.

METHODOLOGY/PRINCIPAL FINDINGS

We demonstrated that BCG induces NIH-3T3 fibroblast proliferation by activating the MAPK and PI3K signaling pathways and also differentiation determined by alpha-smooth muscle actin (alpha-SMA) expression. In vivo, intratumoral inoculation of BCG also increased alpha-SMA and collagen expression. Oral administration of L-NAME enhanced the pro-fibrotic effect of BCG. Peritoneal macrophages obtained from MB49 tumor-bearing mice treated in vivo with combined treatment of BCG with L-NAME also enhanced fibroblast proliferation. We observed that FGF-2 is one of the factors released by BCG-activated macrophages that is able to induce fibroblast proliferation. The involvement of FGF-2 was evidenced using an anti-FGF2 antibody. At the same time, this macrophage population improved wound healing rate in normal mice and FGF-2 expression was also increased in these wounds.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest that fibroblasts are targeted by BCG both directly and through activated macrophages in an immunotherapy context of a bladder murine model. We also described, for the first time, that FGF-2 is involved in a dialog between fibroblasts and macrophages induced after BCG treatment. The fact that L-NAME administration improves the BCG effect on fibroblasts, NO inhibition, might represent a new approach to add to the conventional BCG therapy.

Hypothalamic orexin, OX1, alphaMSH, NPY and MCRs expression in dopaminergic D2R knockout mice

In 5-month-old male and female dopamine receptor 2 (D2R) knockout mice food intake per animal was unaltered while food per g BW was increased. We wished to evaluate the effect of D2R disruption on different components of energy balance and food intake regulation. We determined hypothalamic orexin precursor (PPO) expression, its receptor OX1, serum leptin levels, hypothalamic leptin receptor (OBR), circulating and pituitary alpha MSH levels, as well as central MC3 and MC4 receptors and NPY mRNA in wildtype and D2R knockout mice (KO). Loss of D2R caused a marked increase in serum prolactin levels, to higher levels in females compared to male KO mice. On the other hand, it produced a female-specific increase in circulating alphaMSH, and hypothalamic alphaMSH content, while neurointermediate alphaMSH content was decreased in both sexes. No differences were found in hypothalamic NPY, MC3R or MC4R concentration. Hypothalamic PPO mRNA expression was significantly decreased only in female KOs, while OX1 mRNA was not different between genotypes. Serum leptin levels were also similar in both genotypes. Our results show that in female and not in male mice disruption of the D2R produces two potentially anorexigenic events: an increase in serum and hypothalamic alphaMSH, and a decrease in hypothalamic orexin expression. Very high prolactin levels, which are orexigenic, probably counterbalance these effects, so that food intake is slightly altered. In males, on the other hand, hypothalamic PPO, and serum or hypothalamic alphaMSH are not modified, and increased prolactin levels may account for increased food intake per g BW. These results suggest a sexually dimorphic participation of the D2R in food intake regulation.

Discovery of transcriptional regulators and signaling pathways in the developing pituitary gland by bioinformatic and genomic approaches

We report a catalog of the mouse embryonic pituitary gland transcriptome consisting of five cDNA libraries including wild type tissue from E12.5 and E14.5, Prop1(df/df) mutant at E14.5, and two cDNA subtractions: E14.5 WT-E14.5 Prop1(df/df) and E14.5 WT-E12.5 WT. DNA sequence information is assembled into a searchable database with gene ontology terms representing 12,009 expressed genes. We validated coverage of the libraries by detecting most known homeobox gene transcription factor cDNAs. A total of 45 homeobox genes were detected as part of the pituitary transcriptome, representing most expected ones, which validated library coverage, and many novel ones, underscoring the utility of this resource as a discovery tool. We took a similar approach for signaling-pathway members with novel pituitary expression and found 157 genes related to the BMP, FGF, WNT, SHH and NOTCH pathways. These genes are exciting candidates for regulators of pituitary development and function.

Invasive giant prolactinoma with loss of therapeutic response to cabergoline: expression of angiogenic markers

The present study reports the case of a 70-year-old Caucasian man who was referred to the Military Hospital of Buenos Aires for evaluation of a giant sellar-extrasellar mass with extension in the right temporal lobe and compression of the third ventricle. Patient was initially responsive to cabergoline with reduction of prolactin levels and shrinkage of tumor burden for at least 36 months. Thereafter, prolactin levels and tumor size increased even though cabergoline dosage was increased. Transcraneal surgery was performed at 56 months of treatment. Prolactin levels and tumor proliferation did not subside and the patient died 14 months later. High GH and IGF-I levels were observed in the late stages of tumor development, with no evidence of acromegalic features. Immunohistochemistry of the excised tumor revealed strong immunoreactivity for VEGF and FGF-2, two potent angiogenic factors, and CD31 (an endothelial marker) indicating high vascularization of the adenoma.