Therapeutic response to pazopanib: case report and literature review on molecular abnormalities of aggressive prolactinomas

Introduction

Aggressive prolactinomas (APRLs) pose a significant clinical challenge due to their high rate of regrowth and potentially life-threatening complications. In this study, we present a case of a patient with an APRL who had a trial of multiple therapeutic modalities with the aim to provide a review of molecular abnormalities and management of APRLs by corroborating our experience with previous literature.

Methods

A total of 268 articles were reviewed and 46 were included. Case reports and series, and studies that investigated the molecular and/or genetic analysis of APRLs were included. Special care was taken to include studies describing prolactinomas that would fall under the APRL subtype according to the European Society of Endocrinology guidelines; however, the author did not label the tumor as "aggressive" or "atypical". Addiontionally, we present a case report of a 56-year-old man presented with an invasive APRL that was resistant to multiple treatment modalities.

Results

Literature review revealed multiple molecular abnormalities of APRLs including mutations in and/or deregulation of ADAMTS6, MMP-9, PITX1, VEGF, POU6F2, CDKN2A, and Rb genes. Mismatch repair genes, downregulation of microRNAs, and hypermethylation of specific genes including RASSF1A, p27, and MGMT were found to be directly associated with the aggressiveness of prolactinomas. APRL receptor analysis showed that low levels of estrogen receptor (ER) and an increase in somatostatin receptors (SSTR5) and epidermal growth factor receptors (EGFR) were associated with increased invasiveness and higher proliferation activity. Our patient had positive immunohistochemistry staining for PD-L1, MSH2, and MSH6, while microarray analysis revealed mutations in the CDKN2A and POU6F2 genes. Despite undergoing two surgical resections, radiotherapy, and taking dopamine agonists, the tumor continued to progress. The patient was administered pazopanib, which resulted in a positive response and the patient remained progression-free for six months. However, subsequent observations revealed tumor progression. The patient was started on PD-L1 inhibitor pembrolizumab, yet the tumor continued to progress.

Conclusion

APRLs are complex tumors that require a multidisciplinary management approach. Knowledge of the molecular underpinnings of these tumors is critical for understanding their pathogenesis and identifying potential targets for precision medical therapy.

Sprouting Angiogenesis in Human Pituitary Adenomas

Introduction

Angiogenesis in pituitary tumors is not fully understood, and a better understanding could help inform new pharmacologic therapies, particularly for aggressive pituitary tumors.

Materials and Methods

219 human pituitary tumors and 12 normal pituitary glands were studied. Angiogenic genes were quantified by an angiogenesis qPCR array and a TaqMan probe-based absolute qPCR. Angiogenesis inhibition in pituitary tumors was evaluated in vitro with the endothelial tube formation assay and in vivo in RbΔ19 mice.

Results

71 angiogenic genes, 40 of which are known to be involved in sprouting angiogenesis, were differentially expressed in pituitary tumors. Expression of endothelial markers CD31, CD34, and ENG was significantly higher in pituitary tumors, by 5.6, 22.3, and 8.2-fold, respectively, compared to in normal pituitary tissue. There was no significant difference in levels of the lymphatic endothelial marker LYVE1 in pituitary tumors compared with normal pituitary gland tissue. Pituitary tumors also expressed significantly higher levels of angiogenesis growth factors, including VEGFA (4.2-fold), VEGFB (2.2), VEGFC (19.3), PGF (13.4), ANGPT2 (9.2), PDGFA (2.7), PDGFB (10.5) and TGFB1 (3.8) compared to normal pituitary tissue. Expression of VEGFC and PGF was highly correlated with the expression of endothelial markers in tumor samples, including CD31, CD34, and ENG (endoglin, a co-receptor for TGFβ). Furthermore, VEGFR inhibitors inhibited angiogenesis induced by human pituitary tumors and prolonged survival of RbΔ19 mice.

Conclusion

Human pituitary tumors are characterized by more active angiogenesis than normal pituitary gland tissue in a manner consistent with sprouting angiogenesis. Angiogenesis in pituitary tumors is regulated mainly by PGF and VEGFC, not VEGFA and VEGFB. Angiogenesis inhibitors, such as the VEGFR2 inhibitor cabozantinib, may merit further investigation as therapies for aggressive human pituitary tumors.

Anti-VEGF Therapy in Refractory Pituitary Adenomas and Pituitary Carcinomas: A Review

Most pituitary tumors are considered benign adenomas, and only 0.1%–0.2% of them present metastasis and are defined as pituitary carcinomas (PCs). Refractory pituitary adenomas (PAs) lie between benign adenomas and true malignant PCs and are defined as aggressive-invasive PAs, characterized by a high Ki-67 index, rapid growth, frequent recurrence, and resistance to conventional treatments. Refractory PAs and PCs are notoriously difficult to manage because of limited therapeutic options. Vascular endothelial growth factor (VEGF) plays a crucial role in angiogenesis not only during development but also during pathological processes in pituitary tumors. Recently, increasing numbers of preclinical studies and clinical research have demonstrated that anti-VEGF therapy plays an important role in pituitary tumors. The purpose of this review is to report the role of VEGF in the development and pathology of pituitary tumors and the progress of anti-VEGF therapy in pituitary tumors, including refractory PAs and PCs. Previous preclinical studies indicated that cyclin-dependent kinase 5 (CDK5)-mediated VEGF expression might play a crucial role in the development of PAs. Vascular endothelial growth inhibitors have been reported as independent predictors of invasion in human PAs and have been indicated as markers for poor outcome. Furthermore, several studies have reported that angiogenesis decreases tumor sizes in experimental animal models of pituitary tumors. The expression of VEGF is relatively high in PAs; therefore, anti-VEGF therapy has been used in some refractory PAs and PCs. To date, anti-VEGF has been reported as monotherapy, in combination with temozolomide (TMZ), TMZ and radiotherapy, and with pasireotide, which might be a promising alternative therapy for refractory PAs and PCs resistant to conventional treatments. However, the role of anti-VEGF therapy in pituitary tumors is still controversial due to a lack of large-scale clinical trials. In summary, the results from preclinical studies and clinical trials indicated that anti-VEGF therapy monotherapy or in combination with other treatments may be a promising alternative therapy for refractory PAs and PCs resistant to conventional treatments. More preclinical studies and clinical trials are needed to further evaluate the exact efficacy of anti-VEGF in refractory PAs and PCs.

A single- center experience of prolactin-producing pituitary adenomas without hyperprolactinemia: Its incidence and clinical management

OBJECTIVE

This study clarifies the incidence of prolactin-producing pituitary adenomas without hyperprolactinemia and determines the appropriate treatment strategy for these tumors.

PATIENTS AND METHODS

This retrospective analysis focused on prolactin-producing adenomas without hyperprolactinemia, which were initially treated by surgery as nonfunctioning pituitary adenomas. Among 942 patients with histologically confirmed pituitary adenoma, 114 (12.1 %) patients, consisting of 68 men and 46 women, who had prolactin-producing adenomas without hyperprolactinemia were identified between April 2005 and March 2019.

RESULTS

Of the 114 patients identified, 13 (11.4 %) had prolactin mono-expressions, 18 (15.8 %) had pit-1 lineage hormonal expressions, and 83 (72.8 %) had paradoxical immunoexpression out of the pituitary differentiation lineage, including prolactin. During the follow-up period, 19 patients suffered tumor progression, and 14 required salvage treatment. Of the 19 patients, 11 underwent gamma knife radiosurgery, and none of them experienced further tumor progression. Cabergoline was administered of them to six patients, and one achieved tumor shrinkage. However, the remaining five patients who were treated with cabergoline suffered further tumor progression and required another salvage treatment. Among the patients in the prolactin mono-expression group, one experienced tumor regrowth and underwent gamma knife radiosurgery. In the pit-1 lineage group, two patients experienced tumor regrowth. One had further tumor progression after treatment with cabergoline and underwent gamma knife radiosurgery. Among the patients in the paradoxical immunoexpression group, 16 suffered tumor progression. Four patients underwent further surgery, seven patients were treated with gamma knife radiosurgery, and one patient received fractionated irradiation. None of the eight patients who were treated with gamma knife radiosurgery and fractionated irradiation showed further tumor progression. Four patients in this group were treated with cabergoline, but they all suffered further tumor progression and underwent additional salvage treatments.

CONCLUSIONS

Out of the pituitary differentiation lineage, paradoxical hormonal expression occurred in three-quarters of the patients identified. Further surgery or gamma knife radiosurgery should be given priority in times of tumor progression because most patients were resistant to dopamine agonists.

Exploring the Role of Novel Medical Therapies for Aggressive Pituitary Tumors: A Review of the Literature-"Are We There Yet?"

Aggressive pituitary tumors account for up to 10% of pituitary tumors and are characterized by resistance to medical treatment and multiple recurrences despite standard therapies, including surgery, radiotherapy, and chemotherapy. They are associated with increased morbidity and mortality, particularly pituitary carcinomas, which have mortality rates of up to 66% at 1 year after diagnosis. Novel targeted therapies under investigation include mammalian target of rapamycin (mTOR), tyrosine kinase, and vascular endothelial growth factor (VEGF) inhibitors. More recently, immune checkpoint inhibitors have been proposed as a potential treatment option for pituitary tumors. An increased understanding of the molecular pathogenesis of aggressive pituitary tumors is required to identify potential biomarkers and therapeutic targets. This review discusses novel approaches to the management of aggressive pituitary tumors and the role of molecular profiling.

Emerging and Novel Treatments for Pituitary Tumors

A subset of pituitary neuroendocrine tumors (PitNETs) have an aggressive behavior, showing resistance to treatment and/or multiple recurrences in spite of the optimal use of standard therapies (surgery, conventional medical treatments, and radiotherapy). To date, for aggressive PitNETs, temozolomide (TMZ) has been the most used therapeutic option, and has resulted in an improvement in the five-year survival rate in responders. However, given the fact that roughly only one third of patients showed a partial or complete radiological response on the first course of TMZ, and even fewer patients responded to a second course of TMZ, other treatment options are urgently needed. Emerging therapies consist predominantly of peptide receptor radionuclide therapy (20 cases), vascular endothelial growth factor receptor-targeted therapy (12 cases), tyrosine kinase inhibitors (10 cases), mammalian target of rapamycin (mTOR) inhibitors (six cases), and more recently, immune checkpoint inhibitors (one case). Here, we present the available clinical cases published in the literature for each of these treatments. The therapies that currently show the most promise (based on the achievement of partial radiological response in a certain number of cases) are immune checkpoint inhibitors, peptide receptor radionuclide therapy, and vascular endothelial growth factor receptor-targeted therapy. In the future, further improvement of these therapies and the development of other novel therapies, their use in personalized medicine, and a better understanding of combination therapies, will hopefully result in better outcomes for patients bearing aggressive PitNETs.

Apatinib (YN968D1) and temozolomide in recurrent invasive pituitary adenoma: case report and literature review

BACKGROUND

Invasive pituitary adenomas often recurred after postoperative radiotherapy and are difficult to treat. Temozolomide (TMZ) is an alkylating cytostaticum and has been reported to reduce pituitary tumor size and hormone hypersecretion, However, this is far from enough. Pituitary adenomas have relatively high expression of vascular endothelial growth factor. Therefore, antiangiogenic agent has been used in a small number of aggressive or malignant pituitary tumors after recurrence. Apatinib (YN968D1) is a small-molecule antiangiogenic agent that selectively inhibits VEGFR-2 and also mildly inhibits c-Kit and c-Src tyrosine kinases, abundant in invasive pituitary adenomas.

CASE PRESENTATION

present a 41-year-old female with a growth hormone (GH)-secreting invasive pituitary adenoma causing menstrual disorder and headache symptoms. Over three years, she underwent four surgeries and a stereotactic radiosurgery, but the results were poor. Two months after the fourth operation, she started treatment with temozolomide (200mg/m², d1-5, 28d, orally) and apatinib (0.425g, daily, orally). Her GH level dropped to normal with a >90% decrease in tumor size, after 1-year treatment. There was no evidence of recurrence by imaging or by serum GH levels over 31.5 months of follow-up.

CONCLUSION

we successfully treated this patient with recurrent invasive pituitary adenoma with temozolomide and apatinib for 31.5 months without recurrence. Angiogenesis is an active process in the cases of invasive pituitary adenomas that cannot be controlled by conventional therapy.

Molecular Network Basis of Invasive Pituitary Adenoma: A Review

Cases with pituitary adenoma comprise 10-25% of intracranial neoplasm, being the third most common intracranial tumor, most of the adenomas are considered to be benign. About 35% of pituitary adenomas are invasive. This review summarized the known molecular basis of the invasiveness of pituitary adenomas. The study pointed out that hypoxia-inducible factor-1α, pituitary tumor transforming gene, vascular endothelial growth factor, fibroblast growth factor-2, and matrix metalloproteinases (MMPs, mainly MMP-2, and MMP-9) are core molecules responsible for the invasiveness of pituitary adenomas. The reason is that these molecules have the ability to directly or indirectly induce cell proliferation, epithelial-to-mesenchymal transition, angiogenesis, degradation, and remodeling of extracellular matrix. HIF-1α induced by hypoxia or apoplexy inside the adenoma might be the initiating factor of invasive transformation, followed with angiogenesis for overexpressed VEGF, EMT for overexpressed PTTG, degradation of ECM for overexpressed MMPs, creating a suitable microenvironment within the tumor. Together, they form a complex interactive network. More investigations are required to further elucidate the mechanisms underlying the invasiveness of pituitary adenomas.

Inhibition of Notch signaling attenuates pituitary adenoma growth in Nude mice

Preclinical and clinical studies support that Notch signaling may play an important oncogenic role in cancer, but there is scarce information for pituitary tumors. We therefore undertook a functional study to evaluate Notch participation in pituitary adenoma growth. Tumors generated in Nude mice by subcutaneous GH3 somatolactotrope cell injection were treated in vivo with DAPT, a γ-secretase inhibitor, thus inactivating Notch signaling. This treatment led to pituitary tumor reduction, lower prolactin and GH tumor content and a decrease in angiogenesis. Furthermore, in silico transcriptomic and epigenomic analyses uncovered several tumor suppressor genes related to Notch signaling in pituitary tissue, namely Btg2, Nr4a1, Men1, Zfp36 and Cnot1. Gene evaluation suggested that Btg2, Nr4a1 and Cnot1 may be possible players in GH3 xenograft growth. Btg2 mRNA expression was lower in GH3 tumors compared to the parental line, and DAPT increased its expression levels in the tumor in parallel with the inhibition of its volume. Cnot1 mRNA levels were also increased in the pituitary xenografts by DAPT treatment. And the Nr4a1 gene was lower in tumors compared to the parental line, though not modified by DAPT. Finally, because DAPT in vivo may also be acting on tumor microenvironment, we determined the direct effect of DAPT on GH3 cells in vitro. We found that DAPT decreases the proliferative, secretory and migration potential of GH3 cells. These results position selective interruption of Notch signaling as a potential therapeutic tool in adjuvant treatments for aggressive or resistant pituitary tumors.

Phosphorylation of kinase insert domain receptor by cyclin-dependent kinase 5 at serine 229 is associated with invasive behavior and poor prognosis in prolactin pituitary adenomas

Pituitary adenomas constitute 15-20% of intracranial neoplasms. Previously we reported that cyclin-dependent kinase 5 (CDK5) is upregulated in pituitary tumors associated with activating protein p35, and plays an essential role in pituitary adenomas progression. Here we explored the mechanisms of CDK5 signaling in prolactin pituitary adenomas. Our data indicate that p35 expression and CDK5 activity are both significantly increased in human invasive prolactin pituitary adenomas as compared to noninvasive forms of pituitary adenomas. Inhibition of CDK5 activity suppressed cell migration and invasive ability in GH3 rat pituitary cells. We identified that CDK5 phosphorylates serine 229 residue (Ser-229) of kinase insert domain receptor (KDR), also known as VEGFR-2, in prolactin pituitary adenomas. Phosphorylation of Ser-229 is required for proper KDR surface localization. Phosphorylated Ser-229 in KDR (pSer-229) levels are significantly higher in noninvasive and invasive prolactin pituitary adenomas compared to normal pituitary tissues. In addition, our data indicated that higher KDR pSer-229 correlates with worse prognosis in patients with prolactin pituitary adenomas. In summary, our results illustrated that CDK5-mediated KDR phosphorylation controls prolactin pituitary adenoma progression and KDR pSer-229 serves as a potential prognostic biomarker for both noninvasive and invasive pituitary adenomas.

Landscape of Molecular Events in Pituitary Apoplexy

Apoplectic pituitary adenomas cause significant morbidity and even mortality. The pituitary apoplexy denotes a pituitary adenoma presenting with hemorrhage and/or infarction, implementation in remedial effects of various of drugs in pituitary apoplexy is a promising pharmacogenomic field in the near future adenoma treatment. Indisputably, this is an important horizon for complicated pituitary adenomas. In a pituitary adenoma, the interplay between genetic, cytokine, and growth factors promotes the pathogenic transformation into an apoplectic formation. However, till date, little is known about how all these factors together lead to the pathogenesis of apoplectic pituitary. The vascular endothelial growth factor, tumor necrosis factor-α (TNF-α), pituitary tumor-transforming gene (PTTG), matrix metalloproteinase-2/9 (MMP-2/9), proliferating marker (Ki-67), as well as hypoxia-inducing factor are the major contributing factors involved in pituitary apoplexy. The molecular mechanism involved in pituitary apoplexy has never been described so far. In this review, we discuss the various proteins/cytokines/growth factors and signaling molecules which are involved in the pathogenesis of pituitary apoplexy and their potential role as biomarkers or as therapeutic targets.

Notch system is differentially expressed and activated in pituitary adenomas of distinct histotype, tumor cell lines and normal pituitaries

Pituitary adenomas are among the most frequent intracranial neoplasms and treatment depends on tumor subtype and clinical features. Unfortunately, non responder cases occur, then new molecular targets are needed.

Notch system component expression and activation data are scarce in pituitary tumorigenesis, we therefore aimed to characterize Notch system in pituitary tumors of different histotype. In human pituitary adenomas we showed NOTCH1-4 receptors, JAGGED1 ligand and HES1 target gene expression with positive correlations between NOTCH1,2,4 and HES1, and NOTCH3 and JAGGED1 denoting Notch system activation in a subset of tumors. Importantly, NOTCH3 positive cells were higher in corticotropinomas and somatotropinomas compared to non functioning adenomas. In accordance, Notch activation was evidenced in AtT20 tumor corticotropes, with higher levels of NOTCH1-3 active domains, Jagged1 and Hes1 compared to normal pituitary.

In the prolactinoma cell lines GH3 and MMQ, in vivo GH3 tumors and normal glands, Notch system activation was lower than in corticotropes. In MMQ cells only the NOTCH2 active domain was increased, whereas NOTCH1 active domain was higher in GH3 tumors. High levels of Jagged1 and Dll1 were found solely in GH3 cells, and Hes1, Hey1 and Hey2 were expressed in a model dependent pattern.

Prolactinomas harbored by lacDrd2KO mice expressed high levels of NOTCH1 active domain and reduced Hes1.

We show a differential expression of Notch system components in tumoral and normal pituitaries and specific Notch system involvement depending on adenoma histotype, with higher activation in corticotropinomas. These data suggest that targeting Notch pathway may benefit non responder pituitary adenomas.

Successful treatment of pituitary carcinoma with concurrent radiation, temozolomide, and bevacizumab after resection

The optimal treatment of pituitary carcinomas (PC) is unknown. Treatment includes surgical resection, radiation, and more recently, temozolomide (TMZ). Pituitary adenomas have relatively high expression of vascular endothelial growth factor; therefore, bevacizumab, an antiangiogenic agent, has been used in a small number of aggressive or malignant pituitary tumors after recurrence. However, it has not been administered concurrently with other chemotherapeutic agents or combined with radiation therapy in PC. We present a 63-year-old man with an adrenocorticotropic hormone (ACTH)-secreting PC, causing visual loss. It was resected transsphenoidally. There were several notable factors placing the patient at high risk for recurrence including distant metastasis in the form of a pulmonary nodule. Morphologically, his tumor was a pituitary neoplasm with malignant histopathologic features. It had abundant mitotic figures and zones of necrosis. Six weeks post-surgery, the patient started concurrent chemoradiation, using combination therapy with TMZ and bevacizumab. TMZ was continued for 12 cycles in the adjuvant setting. The ACTH was effective as a serum-based tumor marker and normalized during treatment. The patient is alive, five years after diagnosis, with no recurrence to date. This is the first case of pituitary carcinoma treated successfully with concurrent chemoradiation therapy that combined TMZ and bevacizumab with a long-term follow up.

Global expression profile of tumor stem-like cells isolated from MMQ rat prolactinoma cell

BACKGROUND

Cancer stem cells (CSCs), which have been isolated from various malignancies, were closely correlated with the occurrence, progression, metastasis and recurrence of the malignant cancer. Little is known about the tumor stem-like cells (TSLCs) isolated from benign tumors. Here we want to explore the global expression profile of RNA of tumor stem-like cells isolated from MMQ rat prolactinoma cells.

METHODS

In this study, total RNA was extracted from MMQ cells and MMQ tumor stem-like cells. RNA expression profiles were determined by Agilent Rat 8 × 60 K Microarray. Then we used the qRT-PCR to test the result of Microarray, and found VEGFA had a distinct pattern of expression in MMQ tumor stem-like cells. Then WB and ELISA were used to confirm the VEGFA protein level of tumor sphere cultured from both MMQ cell and human prolactinoma cell. Finally, CCK-8 was used to evaluate the reaction of MMQ tumor stem-like cells to small interfering RNAs intervention and bevacizumab treatment.

RESULT

The results of Microarray showed that 566 known RNA were over-expressed and 532 known RNA were low-expressed in the MMQ tumor stem-like cells. These genes were mainly involved in 15 different signaling pathways. In pathway in cancer and cell cycle, Bcl2, VEGFA, PTEN, Jun, Fos, APC2 were up-regulated and Ccna2, Cdc25a, Mcm3, Mcm6, Ccnb2, Mcm5, Cdk1, Gadd45a, Myc were down-regulated in the MMQ tumor stem-like cells. The expression of VEGFA were high in tumor spheres cultured from both MMQ cell and human prolactinomas. Down-regulation of VEGFA by small interfering RNAs partially decreased cell viability of MMQ tumor stem-like cells in vitro. Bevacizumab partially suppressed the proliferation of MMQ tumor stem-like cells.

CONCLUSIONS

Our findings characterize the pattern of RNA expression of tumor stem-like cells isolated from MMQ cells. VEGFA may act as a potential therapeutic target for tumor stem-like cells of prolactinomas.

Chronic hyperprolactinemia evoked by disruption of lactotrope dopamine D2 receptors impacts on liver and adipocyte genes related to glucose and insulin balance

We studied the impact of high prolactin titers on liver and adipocyte gene expression related to glucose and insulin homeostasis in correlation with obesity onset. To that end we used mutant female mice that selectively lack dopamine type 2 receptors (D2Rs) from pituitary lactotropes (lacDrd2KO), which have chronic high prolactin levels associated with increased body weight, marked increments in fat depots, adipocyte size, and serum lipids, and a metabolic phenotype that intensifies with age. LacDrd2KO mice of two developmental ages, 5 and 10 mo, were used. In the first time point, obesity and increased body weight are marginal, although mice are hyperprolactinemic, whereas at 10 mo there is marked adiposity with a 136% increase in gonadal fat and a 36% increase in liver weight due to lipid accumulation. LacDrd2KO mice had glucose intolerance, hyperinsulinemia, and impaired insulin response to glucose already in the early stages of obesity, but changes in liver and adipose tissue transcription factors were time and tissue dependent. In chronic hyperprolactinemic mice liver Prlr were upregulated, there was liver steatosis, altered expression of the lipogenic transcription factor Chrebp, and blunted response of Srebp-1c to refeeding at 5 mo of age, whereas no effect was observed in the glycogenesis pathway. On the other hand, in adipose tissue a marked decrease in lipogenic transcription factor expression was observed when morbid obesity was already settled. These adaptive changes underscore the role of prolactin signaling in different tissues to promote energy storage.

Prolactinomas: evolution after menopause

OBJETIVE

The aim was to assess the evolution of tumor size and prolactin (PRL) levels in patients with micro and macroprolactinomas diagnosed and treated with dopamine agonists during fertile age, and the effects of suspension of drugs after menopause.

SUBJECTS AND METHODS

Retrospective study, 29 patients with prolactinomas, 22 microadenomas and 7 macroadenomas, diagnosed during their fertile age were studied in their menopause; treatment was stopped in this period. Age at menopause was 49 ± 3.6 years. The average time of treatment was 135 ± 79 months. The time of follow-up after treatment suspension was 4 to 192 months. Results: Pre-treatment PRL levels in micro and macroadenomas were 119 ± 57 ng/mL and 258 ± 225 ng/mL, respectively. During menopause after treatment suspension, and at the latest follow-up: in microadenomas PRL levels were 23 ± 13 ng/mL and 16 ± 5.7 ng/mL, respectively; in macroadenomas, PRL levels were 20 ± 6.6 ng/mL 5t5and 25 ± 18 ng/mL, respectively. In menopause after treatment suspension, the microadenomas had disappeared in 9/22 and had decreased in 13/22. In the group of patients whose tumor had decreased, in the latest follow-up, tumors disappeared in 7/13 and remained unchanged in 6/13. In macroadenomas, after treatment suspension 3/7 had disappeared, 3/7 decreased and 1/7 remained unchanged. In the latest control in the 3 patients whose tumor decreased, disappeared in 1/3, decreased in 1/3 and there was no change in the remaining.

CONCLUSIONS

Normal PRL levels and sustained reduction or disappearance of adenomas were achieved in most of patients, probably due to the decrease of estrogen levels. Dopamine agonists might be stopped after menopause in patients with prolactinomas.

Molecular genetic advances in pituitary tumor development

Pituitary adenomas are a heterogeneous group of tumors that may occur as part of a complex syndrome or as an isolated endocrinopathy and both forms can be familial or non-familial. Studies of syndromic and non-syndromic pituitary adenomas have yielded important insights about the molecular mechanisms underlying tumorigenesis. Thus, syndromic forms, including multiple endocrine neoplasia type 1 (MEN1), MEN4, Carney Complex and McCune Albright syndrome, have been shown to be due to mutations of the tumor-suppressor protein menin, a cyclin-dependent kinase inhibitor (p27Kip1), the protein kinase A regulatory subunit 1-α, and the G-protein α-stimulatory subunit (Gsα), respectively. Non-syndromic forms, which include familial isolated pituitary adenoma (FIPA) and sporadic tumors, have been shown to be due to abnormalities of: the aryl hydrocarbon receptor-interacting protein; Gsα; signal transducers; cell cycle regulators; transcriptional modulators and miRNAs. The roles of these molecular abnormalities and epigenetic mechanisms in pituitary tumorigenesis, and their therapeutic implications are reviewed.

Genetically engineered mouse models of pituitary tumors

Animal models constitute valuable tools for investigating the pathogenesis of cancer as well as for preclinical testing of novel therapeutics approaches. However, the pathogenic mechanisms of pituitary-tumor formation remain poorly understood, particularly in sporadic adenomas, thus, making it a challenge to model pituitary tumors in mice. Nevertheless, genetically engineered mouse models (GEMMs) of pituitary tumors have provided important insight into pituitary tumor biology. In this paper, we review various GEMMs of pituitary tumors, highlighting their contributions and limitations, and discuss opportunities for research in the field.

Cellular proliferation rate and insulin-like growth factor binding protein (IGFBP)-2 and IGFBP-3 and estradiol receptor alpha expression in the mammary gland of dairy heifers naturally infected with gastrointestinal nematodes during development

Mammary ductal morphogenesis during prepuberty occurs mainly in response to insulin-like growth factor-1 (IGF-1) and estradiol stimulation. Dairy heifers infected with gastrointestinal nematodes have reduced IGF-1 levels, accompanied by reduced growth rate, delayed puberty onset, and lower parenchyma-stroma relationship in their mammary glands. Immunohistochemical studies were undertaken to determine variations in cell division rate, IGF-1 system components, and estradiol receptors (ESR) during peripubertal development in the mammary glands of antiparasitic-treated and untreated Holstein heifers naturally infected with gastrointestinal nematodes. Mammary biopsies were taken at 20, 30, 40, and 70 wk of age. Proliferating cell nuclear antigen immunolabeling, evident in nuclei, tended to be higher in the parenchyma of the glands from treated heifers than in those from untreated. Insulin-like growth factor binding proteins (IGFBP) type 2 and type 3 immunolabeling was cytoplasmic and was evident in stroma and parenchyma. The IGFBP2-labeled area was lower in treated than in untreated heifers. In the treated group, a maximal expression of this protein was seen at 40 wk of age, whereas in the untreated group the labeling remained constant. No differences were observed for IGFBP3 between treatment groups or during development. Immunolabeling for α ESR (ESR1) was evident in parenchymal nuclei and was higher in treated than in untreated heifers. In the treated group, ESR1 peaked at 30 wk of age and then decreased. These results demonstrate that the parasite burden in young heifers negatively influence mammary gland development, affecting cell division rate and parameters related to estradiol and IGF-1 signaling in the gland.

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.

Angiogenic markers: molecular targets for personalized medicine in pituitary adenoma

AIM

Pituitary adenomas are typically slow-growing and histologically benign tumors that can occasionally behave in a malignant-like manner, invading adjacent structures or recurring after treatment. Using protein analysis methods and multiplex xMAP assays, we aimed to find out if these particular types of tumors express angiogenic markers VEGF and basic FGF (bFGF), which are associated with tumor growth and invasiveness, and quantify them in order to establish their usefulness as biomarkers.

MATERIALS & METHODS

We have analysed the expression of angiogenic markers VEGF and bFGF in serum and tissue specimens from 66 pituitary adenomas (43 invasive and 23 noninvasive). For serum analysis, we used xMAP and ELISA, and for tissue analysis, we performed histopathology and immunohistochemistry.

RESULTS & CONCLUSION

We measured the serum angiogenic factors in pituitary adenomas. The quantification methods revealed significant differences between pituitary adenoma patients and controls, for both VEGF (212.4 vs 112.5 pg/ml in controls) and bFGF (mean value of 12.6 vs 10.8 pg/ml in controls), and also differentiated between invasive and noninvasive adenomas (p < 0.05). The tissue expression of VEGF and bFGF strongly correlated with their serum level increase. Our findings can be further developed into methods for selection of patients suitable for personalized, antiangiogenic therapy.

Novel, low cost, highly effective, handmade steroid pellets for experimental studies

The basic component of Silastic® glue (Dow Corning) used to prepare Silastic® pellets is polydimethylsiloxane. This compound is also present in other commercial adhesives such as FASTIX® (Akapol SA) that are available in any store for that category. In the present study we developed low cost, easy to prepare handmade steroid pellets (HMSP) by mixing 17β-estradiol, progesterone or other synthetic steroids with FASTIX® adhesive. We assessed serum levels of 17β-estradiol, progesterone, prolactin and luteinizing hormone in ovariectomized mice treated for 24 and 48 h or 7, 14 and 28 days with 20 µg or 5 mg of 17β-estradiol or 5 mg progesterone HMSP. We found a time dependent and significant increase in the levels of both natural hormones, and a downregulation of serum luteinizing hormone levels, while both 17β-estradiol doses increased serum prolactin. Uterine weights at sacrifice and histological examination of the uteri and the mammary glands correlated with estrogen or progestin action. Finally, we evaluated the biological effects of HMSP compared to commercial pellets or daily injections in the stimulation or inhibition of hormone dependent mammary tumor growth, and found that HMSP were as effective as the other methods of hormone administration. These data show that HMSP represent a useful, low cost, easily accessible method for administering steroids to mice.

Management of large aggressive nonfunctional pituitary tumors: experimental medical options when surgery and radiation fail

Pituitary adenomas are generally considered benign tumors; however, a subset of these tumors displays aggressive behavior and are not easily cured. The protocol for nonsurgical treatment of aggressive pituitary lesions is less standardized than that of other central nervous system tumors. Aggressive surgical treatment, radiation, dopamine agonists, antiangiogenic drugs, and other chemotherapeutics all have roles in the treatment of aggressive pituitary tumors. More studies are needed to improve outcomes for patients with aggressive pituitary tumors.

[Clinical guidelines for diagnosis and treatment of prolactinoma and hyperprolactinemia]

OBJECTIVE

To provide practical and up to date recommendations for evaluation, differential diagnosis, and treatment of prolactinoma and hyperprolactinemia in various clinical settings.

PARTICIPANTS

Members of the Neuroendocrinology Working Group of the Spanish Society of Endocrinology.

METHODS

Recommendations were formulated according to the Grading of Recommendations, Assessment, Development, and Evaluation system (GRADE) to describe both the strength of recommendations and the quality of evidence. A systematic search was made in Medline (Pubmed) for each subject, and authors' considerations were added in areas where the literature provided scarce evidence. Finally, recommendations were jointly discussed by the Working Group.

CONCLUSIONS

The document provides evidence-based practical and updated recommendations for diagnosis and management of hyperprolactinemia and prolactinoma, including drug-induced hyperprolactinemia, treatment options for prolactinoma (drugs, surgery, and radiotherapy), prolactinoma in pregnancy, adverse effects of dopaminergic agents, and drug-resistant and malignant prolactinomas.

Cabergoline reduces cell viability in non functioning pituitary adenomas by inhibiting vascular endothelial growth factor secretion

Dopamine (DA) therapy of non-functioning pituitary adenomas (NFA) can result in tumor stabilization and shrinkage. However, the mechanism of action is still unknown. Previous evidence showed that DA can inhibit pituitary vascular endothelial growth factor expression (VEGF), that may be involved in pituitary tumor growth. The aim of our study was to clarify whether VEGF secretion modulation might mediate the effects of DA agonists on cell proliferation in human NFA. We assessed DA receptor subtype 2 (DR2) expression in 20 NFA primary cultures, where we also investigated the effects of a selective DR2 agonist, cabergoline (Cab), on VEGF secretion and on cell viability. All NFA samples expressed α-subunit and DR2 was expressed in 11 samples. In DR2 expressing tumors, Cab significantly reduced cell viability (-25%; P < 0.05) and VEGF secretion (-20%; P < 0.05). These effects were counteracted by treatment with the DA antagonist sulpiride. Cab antiproliferative effects were blocked by VEGF. Our data demonstrate that Cab, via DR2, inhibits cell viability also by reducing VEGF secretion in a selected group of NFA, supporting that DA agonists can be useful in the medical therapy of DR2 expressing NFA.

Thrombospondin-1 (TSP-1) analogs ABT-510 and ABT-898 inhibit prolactinoma growth and recover active pituitary transforming growth factor-β1 (TGF-β1)

Prolactinomas are the most prevalent type of secreting pituitary tumors in humans and generally respond well to a medical therapy with dopamine agonists. However, for patients exhibiting resistance to dopaminergic drugs, alternative treatments are desired. Antiangiogenic strategies might represent a potential therapy for these tumors. Thrombospondin 1 (TSP-1) is a large multifunctional glycoprotein involved in multiple biological processes including angiogenesis, apoptosis, and activation of TGF-β1. Because tumors that overexpress TSP-1 grow more slowly, have fewer metastases, and have decreased angiogenesis, TSP-1 provides a novel target for cancer treatment. ABT-510 and ABT-898 are TSP-1 synthetic analogs that mimic its antiangiogenic action. In the present study, we explored the potential effect of ABT-510 and ABT-898 on experimental prolactinomas induced by chronic diethylstilbestrol (DES) treatment in female rats. We demonstrated that a 2-wk treatment with ABT-510 and ABT-898 counteracted the increase in pituitary size and serum prolactin levels as well as the pituitary proliferation rate induced by DES. These inhibitory effects on tumor growth could be mediated by the antiangiogenic properties of the drugs. We also demonstrated that ABT-510 and ABT-898, in addition to their described antiangiogenic effects, increased active TGF-β1 level in the tumors. We postulate that the recovery of the local cytokine activation participates in the inhibition of lactotrope function. These results place these synthetic TSP-1 analogs as potential alternative or complementary treatments in dopamine agonist-resistant prolactinomas.

New targeted therapies in pituitary carcinoma resistant to temozolomide

To evaluate the antitumoral efficacy of everolimus in pituitary carcinoma resistant to temozolomide, the correlation with mammalian target of rapamycin (mTOR) signaling in the tumor and to present recent advances and future treatments of pituitary carcinomas. Pituitary carcinomas are rare and largely unresponsive to current treatment options. Recent reports on the antitumoral efficacy of temozolomide in some such patients are encouraging, yet most patients appear to show resistance to its actions. As a potential alternative, the mTOR inhibitor, everolimus, has been shown to potently inhibit pituitary cell proliferation highlighting mTOR inhibition as a promising therapeutic approach for pituitary carcinomas. We described the tumoral effects of a combination therapy with everolimus (5 mg/day) and octreotide (30 mg/month) and the mTOR signalling expression in a patient with pituitary ACTH carcinoma, compared to 17 other ACTH adenomas. Clinical and biochemical evaluation were performed every month, and imaging after 3 month of treatment. mTOR signaling was assessed by microarray expression analysis of each of the 18 adenoma tissues. Combined therapy failed to control pituitary tumor growth and ACTH secretion. Slight activation of mTOR signaling was found in all ACTH tumors alongside important variations between tumors. Low antitumor efficacy shown by everolimus might be explained by the weak activation of mTOR pathway in ACTH tumors. Everolimus treatment was inefficient at controlling secretion and tumor growth of one ACTH pituitary carcinoma. More clinical cases, with mTOR signalling expression analysis of the tumor, must be published before any conclusions can be drawn.

Hypoxia-induced VEGF production 'RSUMEs' in pituitary adenomas

Angiogenic markers in pituitary adenomas remain enigmatic in terms of their function in tumorigenesis, despite being upregulated by the normal physiological trigger of hypoxia. In this issue of Endocrine-Related Cancer, Shan et al. report that the novel RWD domain containing protein, RWD-containing sumoylation enhancer, is expressed in human pituitary adenomas and plays a pivotal role in regulating the hypoxia-inducible factor 1α-vascular endothelial growth factor response to hypoxia.