Single-cell transcriptomics reveal distinct immune-infiltrating phenotypes and macrophage-tumor interaction axes among different lineages of pituitary neuroendocrine tumors

BACKGROUND

Pituitary neuroendocrine tumors (PitNETs) are common gland neoplasms demonstrating distinctive transcription factors. Although the role of immune cells in PitNETs has been widely recognized, the precise immunological environment and its control over tumor cells are poorly understood.

METHODS

The heterogeneity, spatial distribution, and clinical significance of macrophages in PitNETs were analyzed using single-cell RNA sequencing (scRNA-seq), bulk RNA-seq, spatial transcriptomics, immunohistochemistry, and multiplexed quantitative immunofluorescence (QIF). Cell viability, cell apoptosis assays, and in vivo subcutaneous xenograft experiments have confirmed that INHBA-ACVR1B influences the process of tumor cell apoptosis.

RESULTS

The present study evaluated scRNA-seq data from 23 PitNET samples categorized into 3 primary lineages. The objective was to explore the diversity of tumors and the composition of immune cells across these lineages. Analyzed data from scRNA-seq and 365 bulk RNA sequencing samples conducted in-house revealed the presence of three unique subtypes of tumor immune microenvironment (TIME) in PitNETs. These subtypes were characterized by varying levels of immune infiltration, ranging from low to intermediate to high. In addition, the NR5A1 lineage is primarily associated with the subtype characterized by limited infiltration of immune cells. Tumor-associated macrophages (TAMs) expressing CX3CR1+, C1Q+, and GPNMB+ showed enhanced contact with tumor cells expressing NR5A1 + , TBX19+, and POU1F1+, respectively. This emphasizes the distinct interaction axes between TAMs and tumor cells based on their lineage. Moreover, the connection between CX3CR1+ macrophages and tumor cells via INHBA-ACVR1B regulates tumor cell apoptosis.

CONCLUSIONS

In summary, the different subtypes of TIME and the interaction between TAM and tumor cells offer valuable insights into the control of TIME that affects the development of PitNET. These findings can be utilized as prospective targets for therapeutic interventions.

Immune Checkpoints: Therapeutic Targets for Pituitary Tumors

Pituitary tumors are the third most common intracranial tumors in adults. Treatment of refractory pituitary tumors is known to be difficult due to limited treatment options. As a promising therapeutic method, tumor immunotherapy has been applied in the treatment of many tumors, including pituitary tumors. Immune checkpoint blocking is one of the effective strategies to activate antitumor immunity. Immune checkpoints prevent tissue damage by regulating the immune response of peripheral tissues and participate in the maintenance of a normal immune environment. In the presence of a tumor, inhibition of T cell activity by tumor cells binding to immune checkpoints and their ligands is an important mechanism for tumor cells to escape immune injury. In this review, we summarize the latest findings of immune checkpoints and their potential as immunotherapeutic targets for pituitary tumors.

The Upregulation of Molecules Related to Tumor Immune Escape in Human Pituitary Adenomas

Human pituitary adenomas are one of the most common intracranial neoplasms. Although most of these tumors are benign and can be treated medically or by transsphenoidal surgery, a subset of these tumors are fast-growing, aggressive, recur, and remain a therapeutic dilemma. Because antibodies against immune checkpoint receptors PD-1 and CLTA-4 are now routinely used for cancer treatment, we quantified the expression of mRNA coding for PD-1, CLTA-4, and their ligands, PD-L1, PD-L2, CD80, and CD86 in human pituitary adenomas and normal pituitary glands, with the ultimate goal of exploiting immune checkpoint therapy in aggressive pituitary adenomas. Aggressive pituitary adenomas demonstrated an increased expression of PD-L2, CD80, and CD86 in compared to that of normal human pituitary glands. Furthermore, aggressive pituitary tumors demonstrated significantly higher levels of CD80 and CD86 compared to non-aggressive tumors. Our results establish a rationale for studying a potential role for immune checkpoint inhibition therapy in the treatment of pituitary adenomas.

Tumor-Associated Macrophages: New Horizons for Pituitary Adenoma Researches

Macrophages are one of the most common infiltrating immune cells and an essential component of tumor microenvironment. Macrophages and the soluble cytokines and chemokines produced play an important role in tumorigenesis, progression, invasion and metastasis in solid tumors. Despite the multiple studies in other solid tumors, there is little known about macrophages in pituitary adenomas. Recently, studies about pituitary adenoma-infiltrated macrophages have been emerging, including the immunohistochemical and immunophenotypic analysis of the pituitary adenomas and further studies into the mechanism of the crosstalk between macrophages and tumor cells in vivo and in vitro. These studies have offered us new insights into the polarization of macrophages and its role in tumorigenesis, progression and invasion of pituitary adenomas. This review describes the advances in the field of pituitary adenoma-infiltrated macrophages and the prospect of targeting macrophages as cancer therapy in pituitary adenoma.

Immune Landscape of Pituitary Tumors Reveals Association Between Macrophages and Gonadotroph Tumor Invasion

PURPOSE

Pituitary neuroendocrine tumors (PitNETs) are frequent intracranial neoplasms that present heterogenic characteristics. Little is known about the immune cell network that exists in PitNETs and its contribution to their aggressive behavior.

METHODS

Here we combined flow cytometry, t-SNE analysis, and histological approaches to define the immune landscape of surgically resected PitNETs. Xenografts of rodent pituitary tumor cells and resected PitNETs were performed in Rag2KO mice, in combination with in vitro analysis aimed at dissecting the role of pituitary tumor-cells in monocyte recruitment.

RESULTS

We report that gonadotroph PitNETs present an increased CD68+ macrophage signature compared to somatotroph, lactotroph, and corticotroph PitNETs. Transcriptomic and histological characterizations confirmed gonadotroph infiltrating macrophages expressed CD163, MRC-1, ARG1, and CSF1R M2 macrophage markers. Use of growth hormone (GH)3/GH4 somatotroph and LβT2/αT3.1 gonadotroph cells drove THP1 macrophage migration through respective expression of CCL5 or CSF1. Although both LβT2 and GH3 cells recruited F4/80 macrophages following their engraftment in mice, only LβT2 gonadotroph cells showed a capacity for M2-like polarization. Similar observations were performed on patient-derived xenografts from somatotroph and gonadotroph tumors. Analysis of clinical data further demonstrated a significant correlation between the percentage of CD68+ and CD163+ infiltrating macrophages and the invasive character of gonadotroph tumors.

CONCLUSIONS

Gonadotroph tumor drive the recruitment of macrophages and their subsequent polarization to an M2-like phenotype. More importantly, the association between infiltrating CD68+/CD163+ macrophages and the invasiveness of gonadotroph tumors points to macrophage-targeted immunotherapies being a potent strategy to limit the progression of gonadotroph PitNETs.

The Immune Profile of Pituitary Adenomas and a Novel Immune Classification for Predicting Immunotherapy Responsiveness

CONTEXT

The tumor immune microenvironment is associated with clinical outcomes and immunotherapy responsiveness.

OBJECTIVE

To investigate the intratumoral immune profile of pituitary adenomas (PAs) and its clinical relevance and to explore a novel immune classification for predicting immunotherapy responsiveness.

DESIGN, PATIENTS, AND METHODS

The transcriptomic data from 259 PAs and 20 normal pituitaries were included for analysis. The ImmuCellAI algorithm was used to estimate the abundance of 24 types of tumor-infiltrating immune cells (TIICs) and the expression of immune checkpoint molecules (ICMs).

RESULTS

The distributions of TIICs differed between PAs and normal pituitaries and varied among PA subtypes. T cells dominated the immune microenvironment across all subtypes of PAs. The tumor size and patient age were correlated with the TIIC abundance, and the ubiquitin-specific protease 8 (USP8) mutation in corticotroph adenomas influenced the intratumoral TIIC distributions. Three immune clusters were identified across PAs based on the TIIC distributions. Each cluster of PAs showed unique features of ICM expression that were correlated with distinct pathways related to tumor development and progression. CTLA4/CD86 expression was upregulated in cluster 1, whereas programmed cell death protein 1/programmed cell death 1 ligand 2 (PD1/PD-L2) expression was upregulated in cluster 2. Clusters 1 and 2 exhibited a "hot" immune microenvironment and were predicted to exhibit higher immunotherapy responsiveness than cluster 3, which exhibited an overall "cold" immune microenvironment.

CONCLUSIONS

We summarized the immune profile of PAs and identified 3 novel immune clusters. These findings establish a foundation for further immune studies on PAs and provide new insights into immunotherapy strategies for PAs.

Antibodies Against Hypothalamus and Pituitary Gland in Childhood-Onset Brain Tumors and Pituitary Dysfunction

Purpose: To detect the presence of antipituitary (APA) and antihypothalamus antibodies (AHA) in subjects treated for brain cancers, and to evaluate their potential association with pituitary dysfunction. Methods: We evaluated 63 patients with craniopharyngioma, glioma, and germinoma treated with surgery and/or radiotherapy and/or chemotherapy at a median age of 13 years. Forty-one had multiple pituitary hormone deficiencies (MPHD), six had a single pituitary defect. GH was the most common defect (65.1%), followed by AVP (61.9%), TSH (57.1%), ACTH (49.2%), and gonadotropin (38.1%). APA and AHA were evaluated by simple indirect immunofluorescence method indirect immunofluorescence in patients and in 50 healthy controls. Results: Circulating APA and/or AHA were found in 31 subjects (49.2%) and in none of the healthy controls. In particular, 25 subjects out of 31 were APA (80.6%), 26 were AHA (83.90%), and 20 were both APA and AHA (64.5%). Nine patients APA and/or AHA have craniopharyngioma (29%), seven (22.6%) have glioma, and 15 (48.4%) have germinoma. Patients with craniopharyngioma were positive for at least one antibody in 39.1% compared to 33.3% of patients with glioma and to 78.9% of those with germinoma with an analogous distribution for APA and AHA between the three tumors. The presence of APA or AHA and of both APA and AHA was significantly increased in patients with germinoma. The presence of APA (P = 0.001) and their titers (P = 0.001) was significantly associated with the type of tumor in the following order: germinomas, craniopharyngiomas, and gliomas; an analogous distribution was observed for the presence of AHA (P = 0.002) and their titers (P = 0.012). In addition, we found a significant association between radiotherapy and APA (P = 0.03). Conclusions: Brain tumors especially germinoma are associated with the development of hypothalamic-pituitary antibodies and pituitary defects. The correct interpretation of APA/AHA antibodies is essential to avoid a misdiagnosis of an autoimmune infundibulo-neurohypophysitis or pituitary hypophysitis in patients with germinoma.

Primary Pituitary Lymphoma in Immunocompetent Patients: A Report on Two Case Studies and the Review of Literature

Primary pituitary lymphoma (PPL) represents an extremely rare entity. Here, we have reported two recently identified cases of immunocompetent PPL having diffuse large B-cell lymphoma by surgical biopsy. Both patients had hypopituitarism, with one patient developing right ptosis. In both patients, MRI and FDG-PET/CT depicted sellar mass that extended into the cavernous sinus with the right sphenoid also present in one of the patients. No systemic disease was found in these two patients. Surprisingly, we found that both patients had infiltrative lesions in sphenoid sinus mucosa pathologically, but the sphenoid bones that composed the sellar base were visually intact during the biopsy procedure. Chemotherapy was administered to both patients, where one patient achieved remission at the recent follow-up, whereas the other one did not respond to the treatment. The diagnosis of PPL is usually difficult if solely dependent on history, clinical presentation, biochemical indexes, and radiographic findings. We have also updated and reviewed the epidemiologic features, clinical presentations, pathological characteristics, potential mechanisms, therapeutic orientation, and prognostic advances of PPL. A total of 40 cases (including ours and four pediatric patients), histologically diagnosed, were analyzed in terms of clinical presentation, endocrine abnormality, radiological features, pathology, treatment, and follow-up. Hypopituitarism and headache were the most common presentation of PPL, while diabetes insipidus was reported in 13 patients (43.3%). B cell lymphoma was the most common type of pathology, followed by T-cell and NK/T cell. PPL was more invasive in nature at the suprasellar region (72.5%), cavernous sinus (52.5%), and sphenoidal sinus (27.5%) in 29, 21, and 11 patients, respectively. Pediatric patients with PPL seem to be different compared to their adult counterparts in terms of pathogenesis, clinical presentation, and radiological features. The management of PPL usually follows the treatment protocols for PCNSL but has a poor prognosis compared to the pituitary involvement of systemic lymphoma.

Transcriptome Analysis Identifies an Attenuated Local Immune Response in Invasive Nonfunctioning Pituitary Adenomas

BACKGROUND

Invasive nonfunctioning pituitary adenomas (NFPAs) remain challenging due to their high complication rate and poor prognosis. We aimed to identify the distinctive molecular signatures of invasive NFPAs, compared with noninvasive NFPAs, using gene expression profiling by RNA sequencing.

METHODS

We obtained frozen fresh tissue samples from 14 patients with NFPAs who underwent primary transsphenoidal surgery. Three non-invasive and 11 invasive NFPAs were used for RNA sequencing. The bioinformatics analysis included differential gene expression, gene ontology analysis, and pathway analysis.

RESULTS

A total of 700 genes were differentially expressed (59 up-regulated and 641 down-regulated genes) between invasive and non-invasive NFPAs (false discovery rate <0.1, and |fold change| ≥2). Using the down-regulated genes in invasive NFPAs, gene ontology enrichment analyses and pathway analyses demonstrated that the local immune response was attenuated and that transforming growth factor-β (TGF-β) RII-initiated TGF-β signaling was down-regulated in invasive NFPAs. The overexpression of claudin-9 (CLDN9) and the down-regulation of insulin-like growth factor-binding protein 5 (IGFBP5), death-associated protein kinase 1 (DAPK1), and tissue inhibitor of metalloproteinase-3 (TIMP3) may be related with invasiveness in NFPAs.

CONCLUSION

Invasive NFPAs harbor different gene expression profiles relative to noninvasive NFPAs. In particular, local suppression of the immune response and TGF-β signaling can make PAs prone to invasiveness.

[Anti-estreptavidin antibodies. Diagnostic confusion by biochemical interference]

We present the case of a patient who, during studies for fertility and subsequent pregnancy, showed an altered thyroid profile with elevated levels of free T4 and normal TSH. After ruling out a thyrotropic adenoma and in the absence of clinical symptoms of hyperthyroidism, the possibility of analytical interference in the immunoassays used to measure hormones was investigated. Interferences caused by heterophile antibodies, macro TSH, anti-thyroid antibodies, biotin, and to a lesser extent anti-streptavidin and anti-ruthenium antibodies have been described. The analysis of the patient was carried out in a self-analyzer whose platform uses the streptavidin-biotin system that is very susceptible to several interferents. A proposed algorithm includes a series of simple tests to perform and interpret that allow detecting or ruling out the presence of interferents. Accordingly, a comparison was made with a different analytical platform (which does not use the streptavidin-biotin system), serial dilutions, precipitation with polyethylene glycol 6000 and treatment with microparticles coated with streptavidin. Results obtained confirmed the presence of anti-streptavidin antibodies in the patient's serum. In the case of disagreements between clinical manifestations and laboratory results, the possibility of methodological interferences should be investigated in order to avoid the potential iatrogenic risk involved in an erroneous biochemical interpretation.

Mononuclear Cell Infiltrate and Hla-Dr Expression in 28 Pituitary Adenomas

Frozen sections from 28 pituitary adenomas were reacted with a panel of monoclonal antibodies to macrophages, lymphocytes and HLA-Dr invariant chain. A low number of macrophages were demonstrated in all tumors, mainly perivascular. CD8 and CD4 lymphocytes were detected in even smaller numbers in 80% and 14% of tumors respectively. B lymphocytes were present in only 1 case. An occasional NK cell was present in 1/13 cases studied. HLA-Dr antigen was expressed by macrophages in all cases and by tumor cells in 2 growth hormone-producing adenomas/19 adenomas. These findings may represent evidence for a low degree of cellular immune response to pituitary adenomas.

Adrenocorticotropic Hormone Secreting Pituitary Adenomas: Analysis of Growth Fraction Using the MIB-1 Antibody

AIMS AND BACKGROUND

Pituitary adenomas are usually considered well differentiated tumors, even if in about one third of cases they invade surrounding tissues, with the possibility of postoperative relapse after complete surgical removal. Adrenocorticotropic hormone (ACTH) secreting adenomas seem to be the most infiltrating subtype, with a higher incidence of recurrence. Ki-67 is a nuclear antigen which is easily detectable by means of the MIB-1 monoclonal antibody, and the labeling index (LI) obtained can be considered a marker of tumor proliferation.

METHODS

In order to identify the growth fraction of these tumors we used the MIB-1 antibody to evaluate the expression of Ki-67 antibody in 11 ACTH secreting pituitary adenomas and to compare it with the LI obtained in 98 other hormone secreting or non-functioning pituitary adenomas consecutively operated on during a 40-month period.

RESULTS

In relation to surgically verified infiltration of the sellar floor dura and bone, we identified eight non-invasive and three invasive ACTH secreting pituitary adenomas. All invasive tumors infiltrated the wall of the cavernous sinus (CS). The mean Ki-67 LI was 5.88 +/- 9.13% versus 2.33 +/- 2.40% in non-ACTH secreting adenomas (P = 0.0025). It was 13.27 +/- 15.42% in invasive and 3.11 +/- 4.37% in non-invasive ACTH adenomas, and 18.40 +/- 17.82% in patients over 50 years versus 3.10 +/- 4.09% in younger subjects (P = 0.02).

CONCLUSIONS

Ki-67 LI is a useful marker in the determination of proliferative activity and invasiveness of anterior pituitary adenomas. Our data seem to confirm that ACTH secreting adenomas have a higher growth fraction than other pituitary adenomas and this observation presumably explains the higher incidence of relapse of these tumors even after macroscopically total removal.

MGMT and MSH6 immunoexpression for functioning pituitary macroadenomas

PURPOSE

Knowledge of biological behavior is crucial for clinical management of functioning pituitary macroadenomas. For recurrent cases unresponsive to standard treatment, temozolomide (TMZ) has been used as a therapeutic alternative. MGMT (O6-methyl-guanine-DNA methyltransferase) and MSH6 (mutS homolog 6) immunoexpression have been linked to the response to TMZ treatment and MGMT immunoexpression has been additionally linked to early recurrence of non-functioning pituitary adenomas. The aim of this study was to assess the prognostic value of MGMT and MSH6 immunoexpression for aggressive functioning pituitary adenomas.

METHODS

The study cohort comprised a single center series of 76 patients who underwent an operation for functioning pituitary macroadenoma. We retrospectively compared 38 patients with postoperative persistent or recurrent disease with another set of 38 patients who were in endocrine remission.

RESULTS

Low-to-moderate MGMT immunoexpression (<50%) was significantly more frequent in the group with persistent/recurrent disease than in cases of endocrine remission (66 vs. 21%, p < 0.001). Furthermore, adenomas with low-to-moderate MGMT immunoexpression were significantly more often recurrent (76 vs. 30%, p < 0.001) and invasive (64 vs. 28%, p = 0.002).

CONCLUSION

In our series, low-to-moderate MGMT immunoexpression was the only marker that significantly correlated with surgical invasiveness and recurrence in functioning pituitary macroadenomas. Therefore, in the future, MGMT status may be considered an additional marker for understanding the biological behavior of pituitary adenomas.

Autoimmune hypothyroidism is three times more frequent in female prolactinoma patients compared to healthy women: data from a cross-sectional case-control study

BACKGROUND

The potent immunomodulatory action of prolactin has been demonstrated in many experimental in vitro studies. In accordance with these data, our retrospective analyses revealed higher prevalence of autoimmune thyroid diseases in prolactinoma patients compared to general population.

PURPOSE

A cross-sectional case-control study was carried out in a single tertiary referral centre. The main aim was to assess the frequency of newly diagnosed autoimmune thyroid diseases in female patients with prolactinomas.

METHODS

The study population consisted of 260 females (154 patients and 106 sex-matched, ethnicity-matched, and age-matched healthy controls) enroled in a prospective manner. Physical exam, thyroid ultrasound, and laboratory testing (measurement of antibodies to thyroglobulin, thyroid peroxidase, TSH-receptor, serum TSH and FT4 levels) were performed in all study participants.

RESULTS

Autoimmune thyroid diseases were diagnosed in 29.9% of the patients and 10.4% of the healthy subjects (p  = 0.0002). Subclinical hypothyroidism was found in 9.7% of the patients versus 2.8% of the controls (p  = 0.044). Autoimmune hyperthyroidism was observed in 1.3% of all patients.

CONCLUSIONS

The prevalence of newly diagnosed autoimmune thyroid diseases, and especially the subclinical hypothyroidism, was significantly higher in our female prolactinoma patients in comparison to age-matched healthy women. Based on our results, we suggest routine screening for autoimmune thyroid diseases (thyroid function, immunology and ultrasound examination) in all female patients with prolactinoma at the time of diagnosis. We also recommend a close follow-up of thyroid function in these women in case of pregnancy and after delivery.

Immunoprofiling of glial tumours of the neurohypophysis suggests a common pituicytic origin of neoplastic cells

PURPOSE

To analyse the antigen expression profiles of 27 cases of pituicytoma, spindle cell oncocytoma, and granular cell tumour of the sellar region concerning a common pituicytic origin of neoplastic cells.

METHODS

Material from 12 female and 15 male patients (13 granular cell tumours of the sellar region, 10 pituicytomas, four spindle cell oncocytomas) collected in the German Registry of Pituitary Tumours between 1993 and 2015 was re-evaluated according to the current WHO classification of tumours of the central nervous system and supplementary immunohistochemistry including S100-protein, CD56, CD68, thyroid transcription factor-1 (TTF-1), and Ki-67 was performed.

RESULTS

S100-protein was detected in all 27 tumours and TTF-1 in all 16 tumours that were assessed. Vimentin was expressed in all 13 cases investigated whereas broad spectrum cytokeratin was not detected in any of 14 evaluated cases. GFAP was observed in nine out of 21 cases. 15 out of 17 investigated lesions showed some CD68 expression and five out of 14 cases were labelled with CD56 antibodies. Proliferative activity did not differ significantly between the three tumour subgroups although one primary and one recurrent pituicytoma showed exceptionally high Ki-67-proliferation indices of 15.3 and 12.7 %, respectively (means: granular cell tumour of the sellar region 2.0 %, pituicytoma 2.8 %, spindle cell oncocytoma 2.7 %).

CONCLUSIONS

The study confirms and expands earlier data and is in line with the notion that the three tumour types are variants of pituicytoma.

Immune Cell Infiltrates in Pituitary Adenomas: More Macrophages in Larger Adenomas and More T Cells in Growth Hormone Adenomas

Tumor immune microenvironment has been gradually recognized as a key contributor to tumor development, progression, and control. Immune cell infiltrates in brain tumors have been increasingly studied, but few have published on immune cell infiltrates in pituitary adenomas. We quantitatively assessed the infiltration of macrophages and lymphocytes in 35 pituitary adenomas, including 9 densely granulated growth hormone (DG-GH), 9 sparsely granulated growth hormone (SG-GH), 9 null cell (NC), and 8 adrenocorticotropic hormone (ACTH) adenomas. All the adenomas showed varying degrees of CD68+ macrophage infiltration. While SG-GH adenomas were significantly larger in size than DG-GH and ACTH adenomas, the infiltration of CD68+ macrophages was significantly greater in SG-GH than in DG-GH and ACTH adenomas. Similarly, NC adenomas that were significantly larger than DG-GH and ACTH adenomas had significantly greater infiltration of CD68+ macrophages than DG-GH and ACTH adenomas. The numbers of CD68+ macrophages were positively correlated with the tumor sizes and Knosp classification grades for tumor invasiveness. The infiltration of CD4+ and CD8+ T cells was relatively scant in these adenomas, but GH adenomas exhibited significantly more CD4+ and CD8+ T cells than non-GH adenomas. Both DG-GH and SG-GH adenomas had significantly more CD4+ cells than ACTH adenomas and significantly more CD8+ cells than NC adenomas. These results suggest an association of CD68+ macrophage infiltration with an increase in the pituitary adenoma size and invasiveness. Our observation contributes to understanding the growth environment of pituitary adenomas, for which adjuvant immunotherapy may help to constrain the tumor enlargement and invasiveness.

Concomitant myasthenia gravis and macroprolactinoma: the immunomodulatory role of prolactin and its potential therapeutic use

Considerable evidence attests to the role of the hypothalamic-pituitary endocrine axis (HPA) in the maintenance of normal immunocompetence. The immune and neuroendocrine systems are integrally linked and coordinated with bidirectional communication maintaining immune balance. Any disturbance of the normal function of the HPA may significantly alter native immunocompetence and therefore be associated with the development of disorders which have a clearly established autoimmune basis. Molecular and functional evidence shows prolactin, produced by the anterior pituitary, to be a cytokine, exerting its effect via both paracrine and endocrine mechanisms [1]. Its involvement in the activation of multiple immune responses may adversely upregulate certain autoimmune diseases. Myasthenia gravis (MG) has long been recognized as an autoimmune disorder. In this mini review, we present the coterminous presentation of MG and prolactin-secreting macroadenoma. We review published cases in the world literature, discuss pathological mechanism, and consider future targeted therapies.

Prevalence of antipituitary antibodies in acromegaly

Acromegaly is a rare disorder due to an excessive production of growth hormone (GH), typically caused by a GH-secreting pituitary adenoma. Anti-pituitary antibodies (APAs) are often seen in patients with different kinds of pituitary pathologies. Because GH has been proposed as a possible antigen recognized by such antibodies, the prevalence of APAs may be higher in conditions characterized by excessive GH secretion. The primary aim of this study was to compare the prevalence of APAs in patients with acromegaly and in controls with other types of pituitary tumors and healthy subjects. Secondary aim was to characterize the pituitary cells targeted by the APAs. Thirty eight acromegaly patients and 215 controls, including 38 patients with prolactinomas, 64 with non-functioning pituitary adenomas (NFPA), and 113 healthy subjects were enrolled in the study. All subjects were tested for APAs using indirect immunofluorescence. Target cells recognized by APAs were identified by double staining immunofluorescence. APAs were significantly more prevalent in acromegaly cases than in healthy controls (10.5% vs. 1.8%, P < 0.05). This prevalence was similar to that found in patients with prolactinomas (7.9%) and NFPA (12.5%). Among APAs-positive subjects, antibodies recognizing somatotrope cells were more common in acromegaly cases than in healthy controls (3/4 vs. 0/113, P < 0.0001), but had similar frequencies in NFPA (2/8) and prolactinomas (1/3). APAs are more frequently found in patients with pituitary adenomas than healthy subjects, with no significant difference among the tumor types studied. GH-secreting cells could represent a target of the autoimmune response.

Pituitary and systemic autoimmunity in a case of intrasellar germinoma

Germinomas arising in the sella turcica are difficult to differentiate from autoimmune hypophysitis because of similar clinical and pathological features. This differentiation, nevertheless, is critical for patient care due to different treatments of the two diseases. We report the case of an 11-year-old girl who presented with diabetes insipidus and growth retardation, and was found to have an intra- and supra-sellar mass. Initial examination of the pituitary biopsy showed diffuse lymphocytic infiltration of the adenohypophysis and absent placental alkaline phosphatase expression, leading to a diagnosis of hypophysitis and glucocorticoid treatment. Because of the lack of clinical and radiological response, the pituitary specimen was re-examined, revealing this time the presence of scattered c-kit and Oct4 positive germinoma cells. The revised diagnosis prompted the initiation of radiotherapy, which induced disappearance of the pituitary mass. Immunological studies showed that the patient's serum recognized antigens expressed by the patient's own germinoma cells, as well as pituitary antigens like growth hormone and systemic antigens like the Sjögren syndrome antigen B and alpha-enolase. The study first reports the presence of pituitary and systemic antibodies in a patient with intrasellar germinoma, and reminds us that diffuse lymphocytic infiltration of the pituitary gland and pituitary antibodies does not always indicate a diagnosis of autoimmune hypophysitis.

MGMT immunoexpression in aggressive pituitary adenoma and carcinoma

Recent case reports have documented the efficacy of temozolomide therapy in some aggressive pituitary adenomas and pituitary carcinomas resistant to multimodality therapy. Evidence suggests that low O6-methylguanine-DNA methyltransferase (MGMT) immunoexpression correlates with response to temozolomide chemotherapy. Herein, we aimed to study MGMT immunoexpression in a spectrum of pituitary tumors, indolent, aggressive and malignant. A literature review of the use of temozolomide in pituitary tumors was also performed. Immunohistochemistry for MGMT was performed on 60 pituitary tumors identified in the Mayo Clinic Tissue Registry and the consultation files of one of us (BWS). The group included 30 pituitary carcinomas (15 ACTH, 10 PRL, 1 FSH/LH, 1 TSH, 1 silent subtype 3 and 2 null cell). Tissue from recurrences was available in 17 cases. In addition, 30 functionally different pituitary adenomas were studied, including 15 invasive and 15 non-invasive adenomas. Overall, 32 cases of pituitary tumors (54%) demonstrated low MGMT immunoexpression. This included 17 of 30 (57%) carcinomas, 9 of 15 (60%) invasive adenomas, and 6 of 15 cases (40%) of non-invasive pituitary adenomas. There was no significant change in MGMT immunoexpression between primary and recurrent tumors. Prolactin-producing carcinomas had the highest proportion of tumors (80%) with low expression. A significant proportion of pituitary adenomas and carcinomas demonstrate low MGMT immunoexpression. In an effort to anticipate the likelihood of a temozolomide response, all cases of aggressive pituitary tumors should be assessed for MGMT expression.

Tumor infiltrating lymphocytes but not serum pituitary antibodies are associated with poor clinical outcome after surgery in patients with pituitary adenoma

CONTEXT

Serum pituitary antibodies (Pit Abs) and tumor-infiltrating lymphocytes (TILs) have been described in pituitary adenomas, but their clinical significance remains unknown.

OBJECTIVE

The objective of the study was to assess Pit Abs and TILs prevalence in pituitary adenomas and their influence on clinical outcome.

DESIGN

This was a prevalence case-control study.

PATIENTS AND SETTING

Two hundred ninety-one pituitary adenoma cases (110 non-secreting, 30 ACTH-69 GH-71 prolactin- and 13 TSH-secreting adenoma; 177 operated and 114 untreated), 409 healthy controls, and 14 autoimmune hypophysitis were enrolled in a tertiary referral center.

INTERVENTION

Pit Abs were measured using immunofluorescence in all cases and controls (n = 714). The presence of TILs was evaluated using CD45 staining in a subset of adenomas surgically treated (n = 72).

MAIN OUTCOME MEASURE

Clinical response of pituitary adenoma after surgery was evaluated.

RESULTS

Pit Abs prevalence was higher in adenomas (5.1%) than healthy subjects (0.7%, P < 0.0001) and lower than in autoimmune hypophysitis patients (57%, P < 0.0001). Similarly, TILs prevalence was higher in adenomas than normal pituitary (P = 0.01) and lower than in autoimmune hypophysitis (P < 0.0001). No correlation between Pit Abs and TILs was found (P = 0.78). A poor clinical outcome was more common in adenoma patients with TILs (11 of 18, 61%) than in those without (17 of 54, 31%, P = 0.026). Multivariate regression analysis identified the presence of TILs as independent prognostic factor for persistence/recurrence of pituitary adenoma.

CONCLUSIONS

TILs and Pit Abs are present in a significant number of pituitary adenoma patients. Cell-mediated immunity appears to be predictive of a less favorable clinical outcome.

A case of thyrotropin-producing pituitary adenoma, accompanied by an increase in anti-thyrotropin receptor antibody after tumor resection

We describe a rare, but interesting, case of TSH-producing adenoma (TSHoma), accompanied by increases in both anti-TSH receptor antibody (TRAb) and thyroid-stimulating antibody (TSAb) after tumor resection. A 21-yr-old woman was referred to our department for further evaluation of pituitary tumor. In a nearby hospital, she had been diagnosed as having pituitary tumor. Her serum free T4, free T3, and TSH levels were all elevated concomitantly. On the basis of a diagnosis of pituitary adenoma with TSH production, transsphenoidal resection of the pituitary adenoma was performed. Two weeks after the operation, the blood concentrations of TSH were undetectable, whereas both TRAb and TSAb levels were elevated. TSAb levels gradually increased further from 2 weeks to 3 months after the operation, accompanied by an increase in TSH and free T4 levels. TSH is an important hormone in maintaining physiology and regulating immunomodulators in thyrocytes, as it can influence a variety of immune-regulating cytokine-like activities and inhibit expressions of Fas antigen, intracellular adhesion molecule-1, and class II trans-activator. Changes in TSH would modulate the immune circumstances in the thyroid, and then induce TRAb and TSAb. Autoimmune parameters with thyroid function should be observed carefully when managing patients with TSHoma.

A study of the correlation between morphological findings and biological activities in clinically nonfunctioning pituitary adenomas

OBJECTIVE

The aims of this study are to review the histology of the clinically nonfunctioning pituitary adenomas (CNFPAs) we have observed and to determine whether or not the frequency of cavernous sinus invasion is different among each type of morphology.

METHODS

In addition, several proliferative markers, including Ki67, p53, E-cadherin, matrix metallo-proteinase 9 and pituitary tumor derived fibroblast growth factor receptor 4 (ptd-FGFR4), were also investigated in invasive and non-invasive tumors.

RESULTS

Our consequent 213 CNFPAs were diagnosed as follows: 64% were silent gonadotroph adenomas, 18% were null cell adenomas, 12% were silent corticotroph adenomas, 4% were silent Subtype 3 adenomas, and 1% were other types of adenomas. Female patients or younger patients showed a significant preponderance in silent corticotroph adenomas and in silent Subtype 3 adenomas, respectively. Cavernous sinus invasion occurs most frequently in silent corticotroph adenomas (85%) followed by Subtype 3 adenomas (67%), null cell adenomas (38%), and silent gonadotroph adenomas (11%). There were no significant differences in the Ki67, p53, E-cadherin, matrix metallo-proteinase 9, and ptd-FGFR4 expression between tumors with and without cavernous sinus invasion.

CONCLUSION

From a clinical standpoint, it is quite important to differentiate morphological type in CNFPAs to aid the clinician in assessing the clinical behavior and prognosis of the tumor. Therefore, we suggest that all CNFPAs be examined not only by conventional light microscopy but also by immunohistochemistry, preferably by electron microscopy, to achieve a correct morphological diagnosis.

Expression and structure of interleukin 4 receptor (IL-4R) complex in human invasive pituitary adenomas

Pituitary adenomas are frequently invasive of surrounding tissues, which adversely affects the surgical outcome and the disease-free survival of patients. In the present study, Interleukin 4 receptor (IL-4R) complex has been investigated to figure out whether the three subunits are overexpressed in human invasive pituitary adenomas. Reverse transcription-polymerase chain reaction (RT-PCR) analysis for interleukin 4 receptor alpha (IL-4Ralpha), interleukin 13 receptor alpha1 (IL-13Ralpha1), interleukin 2 receptor gammac (IL-2Rgammac) were performed on total RNA extracted from 10 non-invasive pituitary adenomas, 30 invasive pituitary adenomas, one glioblastoma multiforme, one normal human pituitary tissue sample and one normal human brain tissue sample. Quantitative real-time PCR and in situ immunofluorescence assay were performed in five invasive functioning pituitary adenoma samples and five invasive nonfunctioning pituitary adenoma samples. RT-PCR analysis for IL-4Ralpha, IL-13Ralpha1 and IL-2Rgammac chains were overexpressed in invasive pituitary adenomas. The transcripts for three subunits were not/weakly expressed in normal pituitary tissue and normal brain tissue. The quantitative real-time PCR and in situ immunofluorescence assay confirmed the results of the RT-PCR analysis. Our results indicate that human invasive pituitary adenomas express type III IL-4R complex. These receptors may serve as a novel target for immunotoxin therapy in patients with invasive pituitary adenomas who are not amenable to total surgical resection or for recurrent cases.

Raised prolactin levels in myasthenia gravis: two case reports and a study of two patient populations

OBJECTIVES

To describe two patients with myasthenia gravis (MG) and prolactinoma and analyze the associations between MG and prolactin (PRL) levels.

DESIGN

Two case reports and a case-control study of PRL levels in 192 patients with MG.

PARTICIPANTS

The Immunological Research Laboratory, Center for Molecular Medicine, Department of Medicine and the Department of Neurology, Karolinska Institutet, Stockholm, Sweden; St Petersburg Medical Academy for Postgraduate Studies, and St Petersburg State Medical Pediatric Academy, Russia.

RESULTS

Two women with MG and thymic hyperplasia accompanied by prolactinomas are described. The levels of plasma PRL were raised in 101 women with MG, but not in 91 men. There was an association between high PRL levels and high levels of autoantibodies against the acetylcholine receptor.

CONCLUSIONS

There is an association of MG with raised levels of PRL in women. PRL has stimulating effects on immune activation and the increased levels might thus be implied in the pathophysiology of MG.

Immunotherapy of prolactinoma with a T helper 1 activator adjuvant and autoantigens: a case report

OBJECTIVE

To date, efforts to reliably manipulate the immune system to promote tumor regression in the brain have been disappointing. We report a unique experience of successful immunotherapy to treat a pituitary macroprolactinoma.

METHODS

A 31-year-old woman with an established history of pituitary macroprolactinoma who had undergone tumor resection followed by radiation was admitted to our clinic. The diagnosis had been made due to the patient's symptoms, a serum prolactin (PRL) level of 29,600 mIU/l, a brain MRI revealing a 23 x 19 x 18 mm pituitary mass and a positive PRL immunohistochemistry of the mass. Six months following surgery, she reexperienced headache, excessive sweating and a serum PRL concentration of 2,960 mIU/l despite receiving 30 mg/day bromocriptine. Brain MRI revealed a pituitary mass (3 x 6 x 8 mm) compatible with a pituitary adenoma. Twenty micrograms per milliliter of G2 (as a T helper 1 activator adjuvant) was inoculated intradermally once per week for 24 consecutive weeks (each injection contained 10 mug of G2). The autoantigens were inoculated at the same time with G2.

RESULTS

After immunotherapy, serum PRL concentration decreased to 82 mIU/l, the patient's symptoms disappeared, skin thickness increased to normal and bromocriptine dosage was tapered to 20 mg per week. A follow-up brain MRI revealed almost complete disappearance of the tumor. The patient does not complain of any problems at 1-year follow-up.

CONCLUSION

Activation of both nonspecific (natural killer cells) and specific (cytotoxic T lymphocytes) immunity in relation to the T helper 1 cytokine network is a promising strategy for the treatment of tumors of the central nervous system in humans, especially pituitary macroprolactinomas.

Modulation of interleukin-1 receptors followed by endotoxin lipopolysaccharide treatment in the mouse AtT-20 pituitary tumor cell line

OBJECTIVE

We have previously reported the characterization and regulation of interleukin-1 (IL-1) receptors utilizing [125I]IL-1 binding assay in male C57BL/6 mice and the mouse AtT-20 pituitary tumor cells. In the present study, we examine IL-1 receptors using an immunoblotting method to further characterize the mechanisms regulating the interactions of IL-1 receptors with endotoxin, lipopolysaccharide (LPS).

METHODS

We established Western blotting for IL-1 receptors using AtT-20 mouse pituitary tumor cells.

RESULTS

Several bands were seen; however, only the 105-kD band was neutralized with a 5-fold excess of IL-1 receptor- blocking peptides, suggesting that this band is specific for IL-1 receptors. Next, we investigated the effect of LPS and IL-1beta on IL-1 receptors. Treatment of AtT-20 cells with 0.01 microg/ml of LPS did not affect IL-1 receptors. In contrast, 1 microg/ml of LPS significantly increased IL-1 receptors in AtT-20 cells compared with the control group. In addition, [125I]IL-1beta binding was markedly increased followed by 1 microg/ml of LPS. In contrast, 1 nM recombinant human IL-1beta significantly decreased IL-1 receptors in AtT-20 cells compared with the control group although treatment of AtT-20 cells with 0.01 nM IL-1beta did not affect IL-1 receptors. LPS (0.1 and 1 microg/ml) did not affect IL-1beta concentrations in the medium of AtT-20 cell culture. IL-1beta concentrations in the homogenates from AtT-20 cells were significantly decreased after 1 microg/ml of LPS treatment but not after 0.01 microg/ml LPS.

CONCLUSIONS

These data demonstrate that LPS and IL-1beta differentially modulate IL-1 receptors in AtT-20 cells and LPS-induced modulation of IL-1 receptors may provide a novel mechanism for the actions of LPS to alter pituitary function during endotoxemia. Additional in vivo studies are necessary to determine the physiological relevance of this in vitro phenomenon.

Enhanced protein kinase B/Akt signalling in pituitary tumours

Pituitary tumours have previously been shown to harbour several abnormalities that cause deregulation of the cell cycle, particularly down-regulation of expression of the cyclin-dependent kinase inhibitor p27. However, it has been unclear whether these are the primary initiating events, or are secondary to other more proximate alterations in signalling pathways. In other cellular systems the Akt signalling pathway has been associated with downstream modulation of cell-cycle control. The aim of the present study was to test the hypothesis that Akt signalling is enhanced in pituitary tumours, and to see if changes in Akt expression are related to previous findings on low expression levels of the nuclear cell-cycle inhibitor p27 in pituitary tumours. We examined normal and adenomatous human pituitary tissue for mRNA and protein expression of Akt1, Akt2 and p27, and the activation of Akt, as well the phosphatase involved in the inactivation of Akt, phosphatase and tensin homologue deleted on chromosome 10 (PTEN). In pituitary adenomas Akt1 and Akt2 mRNA were found to be over-expressed compared with normal pituitary, while PTEN transcripts showed similar levels between the two tissue types. Immunohistochemical expression of phospho-Akt was found to be higher in the tumours than normal pituitaries, while the protein expression of nuclear p27 and PTEN was lower in the adenomas. However, the expression of p27 and Akt were not directly correlated. PTEN sequencing revealed no mutation in the coding region of the gene in pituitary adenomas, and thus we did not locate a cause for the increased phosphorylation of Akt. In summary, we have shown over-expression and activation of the Akt pathway in pituitary tumours, and we speculate that cell-cycle changes observed in such tumours are secondary to these more proximate alterations. Since Akt is a major downstream signalling molecule of growth factor-liganded tyrosine kinase receptors, our data are most compatible with an abnormality at this level as the primary driver of pituitary tumorigenesis.

Bacterial endotoxin (lipopolysaccharide) stimulates interleukin-6 production and inhibits growth of pituitary tumour cells expressing the toll-like receptor 4

Members of the Toll receptor (Tlr) family have a crucial role in the innate immune response following bacterial infection. The effects of Gram-negative bacteria-derived endotoxins (lipopolysaccharide, LPS) are predominantly mediated by Tlr4, and we have recently shown that pituitary folliculostellate cells express functional Tlr4. In the present study, we investigated whether Tlr4 is also present in normal and transformed endocrine epithelial pituitary cell types. By reverse transcriptase-polymerase chain reaction, Tlr4 mRNA expression was found in some pituitary epithelial tumour cell lines (AtT20, HP75), whereas others were negative (GH3, alphaT3-1). Tlr4 protein was detected by immunohistochemistry in a few epithelial cells in normal human anterior pituitaries and in 26 out of 67 human pituitary tumours analysed. LPS had no effect on adrenocorticotropic hormone secretion in Tlr4-positive AtT20 cells, but it suppressed the growth of these cells in a dose-dependent manner. As expected, neither hormone secretion, nor growth of Tlr4-negative GH3 cells was affected by LPS. In cell cultures of Tlr4-positive pituitary adenomas, LPS dose-dependently stimulated the production of interleukin (IL)-6, which is known to induce growth and hormone production in pituitary tumours. The LPS-induced IL-6 production was blocked by the specific p38alphaMAP kinase inhibitor, SB203580, and by the synthetic glucocorticoid, dexamethasone. The data suggest that, during Gram-negative bacteria-induced infections or inflammatory processes, LPS could affect pituitary tumour pathophysiology and progression in the subset of Tlr4-expressing pituitary adenomas.

Measurement of Ki-67 antigen in 159 pituitary adenomas using the MIB-1 monoclonal antibody

Pituitary adenomas sometimes show rapid growth and recurrence, and about one third invade the structures surrounding the sella turcica. In an attempt to determine aggressive behavior at an early stage, we used the MIB-1 antibody to identify the Ki-67 antigen. The present study was designed to evaluate pituitary adenomatous tissue in terms of secretion and proliferation and to correlate the Ki-67 index with hormone phenotype and invasive behavior. Material from 159 patients submitted to one or more resections of pituitary adenomas was evaluated. Forty-two non-secretory adenomas and 43 adenomas immunoreactive for growth hormone, 19 for prolactin, 18 for growth hormone and prolactin, 16 for adrenocorticotropic hormone (ACTH), and 21 cases of plurihormonal/gonadotropin adenomas were detected by immunohistochemistry. The MIB-1 antibody was positive in 139 samples and the Ki-67 index ranged from 0.16 to 15.48% (mean = 1.22 +/- 2.09%), with no significant difference between genders, age groups, or secretory and non-secretory status. The Ki-67 index was higher in ACTH-secreting adenomas. Invasive pituitary adenomas had a significantly higher Ki-67 index (2.01 +/- 3.15%) than macroadenomas with or without supra-sellar extension (1.12 +/- 1.87%; P = 0.02). The index was not significantly different in the subgroup of adenomas with invasion of the cavernous sinus compared to groups with other types of invasion. We conclude that tumoral proliferative activity evaluated by the detection of the Ki-67 antigen is significantly higher in invasive than noninvasive adenomas, information which can be useful in therapeutic postoperative management since index cut-off values associated with aggressive behavior can be established.

Anti-alpha-enolase antibodies in pituitary disease

A previous study reported a high prevalence of autoantibodies to alpha-enolase in lymphocytic hypophysitis and these antibodies efficiently distinguished lymphocytic hypophysitis from pituitary tumors. To confirm this, we examined autoantibodies to alpha-enolase in patients with lymphocytic hypophysitis (n = 17), pituitary non-functioning adenoma (n = 13), other pituitary diseases (n = 17) and other autoimmune diseases (n = 30), and compared to healthy controls (n = 46). Autoantibodies were found in 41.2%, 46.2%, 23.5%, 20.0% and 4.3%, respectively. Our findings indicate that detection of anti-alpha-enolase antibodies is not suitable for specific diagnosis of lymphocytic hypophysitis.

Frequent appearance of autoantibodies against prohormone convertase 1/3 and neuroendocrine protein 7B2 in patients with nonfunctioning pituitary macroadenoma

Among pituitary disorders having mass effect of the pituitary gland, nonfunctioning pituitary macroadenoma and lymphocytic hypophysitis are difficult to differentiate without histological examination. In order to efficiently distinguish lymphocytic hypophysitis and pituitary tumors, we studied the presence of autoantibodies against prohormone-processing enzymes, prohormone convertase (PC) 1/3, PC2, carboxypeptidase E (CPE), and PC2 regulatory protein, 7B2, by radioligand assay using recombinant human 35S-labeled protein in patients with clinically nonfunctioning pituitary macroadenoma, lymphocytic hypophysitis, and other pituitary diseases. The indexes for anti-PC1/3 antibodies (Ab) were significantly higher in patients with nonfunctioning pituitary macroadenoma than in patients with lymphocytic hypophysitis. Patients positive for either anti-PC1/3 or anti-7B2 Ab were significantly frequent among patients with nonfunctioning pituitary macroadenoma than in other pituitary diseases and healthy controls. None of the patients was positive for anti-PC2 Ab or anti-CPE Ab. These results suggest that autoantibodies against PC1/3 and 7B2 are novel tumor-associated autoantibodies and can be helpful in the diagnosis of clinically nonfunctioning pituitary macroadenoma.

Integrating systemic information at the molecular level: cross-talk between steroid receptors and cytokine signaling on different target cells

An essential event in immune activation is the increase of cytokines in both plasma and immune tissues. Steroid hormones influence several adaptive responses in both health and disease. Cytokines and steroids have an intimate cross-communication in many systems, making possible a satisfactory adaptive response to environmental changes. The ultimate level of integration of the cytokine-steroids cross-talk is the molecular level. We have demonstrated this in four types of cross-talk mechanisms on different cells in which steroids have major roles: (1) The tumor necrosis factor (TNF)-glucocorticoid receptor (GR) transcriptional interaction in cellular targets of TNF-induced cytotoxicity. TNF potentiates the transactivation activity of GR and the priming with TNF increases the protective action of GR on TNF-induced cytotoxicity. (2) The GR-T cell receptor (TCR) antagonism in GR-TCR-induced T cell apoptosis and its modulation by cAMP. cAMP inhibits the TCR-induced apoptosis through a PKA-CREB-dependent mechanism and potentiates glucocorticoid-induced apoptosis by means of a CREB-independent mechanism. (3) The GR influence on Th1-Th2 cytokine expression and differentiation. Glucocorticoids inhibit the induction of GATA-3 and T-bet transcription factors. (4) The influence of ER/Smad-4 signaling cross-communication on prolactinoma pathogenesis. Physical and functional interactions between Smad-4 and estrogen receptors take place in prolactinoma cells, providing a molecular explanation to link the tumorigenic action of these two important players of prolactinoma pathogenesis. The molecular cross-talk between steroids and transcription factors is the mechanism that provides the basis for the outcome of adaptive responses integrating the systemic information provided by hormones and cytokines.

[Pituitary tumors: hormonal status and immunohistochemical evaluation]

New imaging modalities and hormonal diagnostic improvement have markedly increased the number of newly recognized pituitary tumours. Introduction of immunohistochemical assays in histopathological diagnostics of pitutary adenomas resulted in better understanding of pathology and clinics of these neoplasms. The aim of the study was to correlate the hormonal status and hematoxylin-eosin staining results with immunohistochemical staining of pituitary tumours. The study included 40 patients aged 43.8 +/- 18.3 years, diagnosed with a pituitary tumour in the Department of Endocrinology Collegium Medicum UJ, who subsequently underwent trans-sphenoidal surgery in the Department of Neurosurgery Collegium Medicum UJ. The serum pituitary hormone levels were assessed by means of radioimmuno-assays. The surgically obtained tumour tissue was evaluated both by hematoxylin-eosin and immunohistochemical staining. Using traditional staining 33 patients were diagnosed with chromophobic adenoma, 1 with basophilic adenoma, and remaining 6 with eosinophilic tumour. Immunohistochemical assays were ACTH-positive in 16, TSH-positive in 7, GH-positive in 14 and PRL-positive in 17 cases. In 15 subjects immunohistochemical staining was positive for at least two pituitary hormones. In 34 of 54 patients with positive immunohistochemical staining results, no increase in corresponding pituitary hormone serum levels was observed. In 5 of 9 patients with negative immunohistochemical staining, no increase in serum hormone level was noted, remaining 4 were characterized by hyperprolactinaemia. Tumour cells were ACTH-positive in 5 of 6 patients with elevated serum ACTH levels and GH- or TSH-positive in all cases of increased levels of these hormones. Only 6 of 15 subjects with hyperprolactinaemia revealed positive PRL immunohistochemical staining.

CONCLUSIONS

Positive immunohistochemical staining often do not correlate with elevated basal serum pituitary hormone levels, which may be related to either impaired synthesis or excretion of the hormones by tumour cells. Increased serum levels of ACTH, TSH or GH are usually connected with positive immunohistochemical staining results. Hyperprolacinaemia in cases of PRL-negative assays arises from PRL secretion defects caused by the tumour presence itself.

Chromogranin a processing in human pituitary adenomas and carcinomas: analysis with region-specific antibodies

The expression of various chromogranin A (CgA) peptide fragments was examined with region-specific antisera in benign and malignant pituitary tumors. Analysis of the proconvertases responsible for proteolytic processing of CgA, prohormone convertase 1/3 (PC1/3), and PC2 was also performed. Adenomas were studied using tissue microarrays, and a larger tissue section of a subset of the prolactin (PRL) adenomas was used to compare to the tissue microarray analysis. Carcinomas were analyzed using larger tissue sections. There were differences in CgA proteolytic products detected between the functional (PRL, adrenocorticotropic hormone [ACTH], and growth hormone tumors and the nonfunctional (gonadotroph and null cell) tumors, with the former group expressing lower levels of many peptides. These differences were most notable in the PRL adenomas and carcinomas in which the region-specific antisera against vasostatin I and vasostatin II detected these fragments in the lowest percentage of tumors and/or had the weakest immunoreactivity. The CgA peptide fragment detected by CgA 176-195 (chromacin) antiserum was expressed by the highest percentage of most functional and nonfunctional benign and malignant pituitary tumors. ACTH carcinomas (n = 3) were more strongly immunoreactive compared to the ACTH adenomas. These results show that there is differential expression of CgA peptide fragments and PC1/3 among different types of pituitary tumors and that ACTH pituitary carcinomas have higher levels of immunoreactive CgA peptide fragments compared to ACTH adenomas. This study also shows the utility of tissue microarrays in the analysis of a large group of tumors with regionspecific antisera.

Hormone markers in pituitary adenomas: changes within last decade resulting from improved method

The significance of polyclonal antibodies for demonstration of hormone expression in pituitary adenomas was compared with the significance of monoclonal antibodies (MAbs). Adenomas were classified by light microscopic structures in paraffin- and epon-embedded sections, by immunostaining for all pituitary hormones, and in part by electron microscopy. In the first series, 166 adenomas were studied with polyclonal antibodies during 1990 and 1991. In the second series, 572 adenomas were immunostained with MAbs during 1999 and 2000. In the first series, a very typical type-specific hormone expression was demonstrable in 63.2% of adenomas in contrast to 91.1% in the second series. Consequently, in the first series 36.7% of adenomas expressed additional or atypical hormones in >10% of adenoma cells, whereas in the second series only 8.9% contained additional hormones. We conclude that MAbs show a clearer cutoff in immunostainings of pituitary hormones and therefore should be preferred for adenoma classification.

Antibodies to pituitary surface antigens during various pituitary disease states

Autoantibodies to cell surface antigens of human somatotropinoma (ASAS), human prolactinoma (ASAP) and rat adenohypophysis (ASARA) were assayed in the serum of patients with pituitary diseases associated with GH deficiency (GHD), such as pituitary dwarfism and primary empty sella syndrome (ESS), and in the serum of patients with hyperprolactinaemia of different etiologies: idiopathic hyperprolactinaemia, prolactinoma and ESS. The investigation was carried out with a cellular variant of an ELISA. Among children with GHD, the highest percentage of antibody-positive patients was found in the group with idiopathic isolated GHD (89% of ASAS(+) patients and 30% of ASARA(+) patients vs 33.3% and 0% respectively in the group with idiopathic combined pituitary hormone deficiency, and 33.3% and 9% in patients with pituitary hypoplasia associated with isolated GHD or combined pituitary hormone deficiency). Among hyperprolactinaemic patients, the highest ASAP and ASARA frequency was observed in patients with idiopathic hyperprolactinaemia (67.7% and 41.9% respectively) where it was twice as high as in the group of patients with prolactinoma. The proportion of ASAS(+) and ASARA(+) did not differ significantly between the groups of patients with ess with or without GHD. Similarly, there was no significant difference between the number of ESS ASAP(+) and ASARA(+) patients with or without hyperprolactinaemia. The data obtained suggested that autoimmune disorders may be primary, and responsible, at least in part, for pituitary dysfunction in the cases of idiopathic isolated GHD and idiopathic hyperprolactinaemia. At the same time, the autoimmune disorders in the patients with prolactinoma or ESS are probably secondary to the organic pituitary lesion and their significance in the development of the pituitary dysfunction is obscure.

Leukaemia inhibitory factor and interleukin 6 inhibit secretion of prolactin and growth hormone by rat pituitary MtT/SM cells

The rat pituitary cell line, MtT/SM, has the characteristics of somatomammotrophs. The cells secrete both prolactin (PRL) and growth hormone (GH). We examined the effects of cytokines such as leukaemia inhibitory factor (LIF), interleukin 6 (IL-6), oncostatin M and interleukin 11 on the secretion of these hormones by the cells. These cytokines stimulate proliferation of the cells and inhibit the secretion of PRL by 70-80% and that of GH by 50%. They induce tyrosine phosphorylation of STAT3 in the cells. The cells containing PRL or GH decreased at 48 h after treatment of the cells with LIF or IL-6. These results suggest that the LIF/IL-6 family of cytokines inhibits the functions of mammotrophs and somatotrophs in the pituitary gland.

The effect of prolactin and bromocriptine on human peripheral immune status

The aim of this study was to determine the influence of elevated serum prolactin (PRL) levels on the peripheral lymphocyte subsets in patients with hyperprolactinemia. For this purpose we studied 20 hyperprolactinemic patient lymphocyte subsets by flow cytometry on their hyperprolactinemic state and after their serum prolactin concentration was normalized with bromocriptine (BC) alone or BC and surgery. We observed decreased absolute numbers and percentage of Natural Killer (p=0.0009 and 0.0001, respectively) and CD3/CD25 lymphocytes (p = 0.009 and 0.002) in hyperprolactinemic patients, compared to 8 sex- and age-matched normal controls. There was no correlation between PRL levels and CD16/56 and CD3/CD25 numbers (p=0.72 and 0.33, respectively). We did not find any significant difference in absolute numbers (p = 0.95) and percentage (p = 0.84) of B-lymphocytes of hyperprolactinemic patients, as compared with normal controls. We did not detect any increase in absolute cell numbers of CD16/CD56 (p = 0.21) and CD3/CD25 (p = 0.61) of BC-treated patients when compared to their hyperprolactinemic state. We demonstrated an increase in CD8-cells (p = 0.0173) and a decrease in CD4/CD8 ratio (p = 0.036) in hyperprolactinemic patients treated with BC. There was also an increase in the number of activated T-cells (CD3/HLA DR) in this group, compared to normal controls and the hyperprolactinemic state of the same patients (p = 0.04). In conclusion, elevated PRL levels do not lead to an "overstimulation" of the B-cells, but deteriorate the cytotoxic function.

Immunocytochemical prognostic markers in pituitary tumors

The value of different immunocytochemical markers in the evaluation of the pituitary tumor aggressiveness is discussed on the basis of the data from the literature and the author's personal experience. The usefulness of the proliferation markers (PCNA, Ki-67), prothymosin-alpha, the endothelial markers revealing the intratumoral vascularization and of the expression or co-expression of glycoprotein hormones in predicting the aggressive behaviour of the tumor is likely, but still needs further studies.

Proliferation index of nonfunctioning pituitary adenomas: correlations with clinical characteristics and long-term follow-up results

OBJECTIVE

The recurrence of nonfunctioning pituitary adenomas (NFPAs) after surgical removal is common. The aim of our study was to investigate and correlate the growth fraction of NFPAs with clinical characteristics and long-term follow-up results.

METHODS

Tumor specimens were obtained from 101 consecutive patients with NFPAs (48 female patients and 53 male patients; mean age, 52.0 +/- 1.5 yr). Specimens were immediately fixed in 10% buffered formalin and then embedded in paraffin. The Ki-67 antigen was assessed by immunocytochemical analysis using the monoclonal antibody MIB-1. The Ki-67 antigen labeling index (LI) was determined by counting a total of at least 1,000 neoplastic nuclei.

RESULTS

The mean Ki-67 LI for the 101 patients was 2.4 +/- 0.3% (range, 0-23.0%). Only age at surgery was inversely correlated with the Ki-67 LI; sex, maximal tumor diameter, and invasiveness into the cavernous sinuses did not significantly affect the Ki-67 LI. The mean follow-up period was 39.7 +/- 2.1 months. During follow-up monitoring, 23 patients experienced tumor recurrence, after a mean period of 28.6 +/- 4.8 months. Invasiveness of the tumor on preoperative magnetic resonance imaging scans was the strongest predictor of late tumor recurrence, followed by previous pituitary surgery, younger age, and lack of postoperative radiotherapy. The Ki-67 LI had no independent prognostic value.

CONCLUSION

Our study suggests that the clinical characteristics of patients with NFPAs, except for age at surgery, are not correlated with the Ki-67 LI. Moreover, the Ki-67 LI does not seem to provide independent information to identify patients at high risk for tumor recurrence.

Expression of members of the interleukin-6 family of cytokines and their receptors in human pituitary and pituitary adenomas

There is increasing evidence for the role of members of the Interleukin (IL)-6 family in pituitary function, particularly in the regulation of the hypothalamo-pituitary-adrenal axis. However, there is only a limited amount of data available on the expression in human normal and tumorous pituitary tissue. In this study we investigated the expression of members of the IL-6 family of cytokines and their receptors in normal human pituitaries as well as pituitary adenomas using the RT-PCR technique. Eighteen pituitary adenoma biopsies removed in transsphenoidal surgery (six corticotrophic adenomas, four nonfunctioning adenomas, four somatotrophinomas, four prolactinomas) and six normal anterior pituitaries were examined for the expression of IL-6 receptor (-R), leukemia inhibitory factor (LIF), LIF-R, IL-11, IL-11-R, oncostatin M (OSM), OSM-R, ciliary neurotrophic factor (CNTF), CNTF-R and cardiotrophin-1 (CT-1). All pituitaries and pituitary adenomas expressed OSM transcripts, whereas no expression of CT-1 was found. The expression of all other cytokines (LIF, IL-11, CNTF) and receptors (IL-6-R, LIF-R, IL-11-R, OSM-R, CNTF-R) was found in different patterns in the adenoma subtypes and normal pituitaries. However, we did not detect expression of LIF-, IL-11-, IL-6-R and CNTF-R in prolactinomas, of CNTF in normal pituitaries and of OSM-R in ACTH-secreting adenomas. In conclusion, our study provides further evidence for a role of the members of the IL-6 family of cytokines in pituitary function.

Secretory granules of pituitary adenomas: quantitative study of hormonal antigenicity

Ultrastructurally, the antigenicity of major pituitary hormones in secretory granules was quantitatively investigated in five growth hormone (GH)-secreting adenomas, five prolactin (PRL)-secreting adenomas and eight clinically non-functioning (CN-F) adenomas. Sparsely granulated cells with a few or several small secretory granules (60-100 nm) exhibiting little or only weak antigenicity of various biochemically unrelated hormones were commonly observed in CN-F adenomas and occasionally in GH- and PRL-secreting adenomas. GH- or PRL-secreting adenomas consisted of many densely granulated cells with medium-sized (200-250 nm) or large (over 250 nm) secretory granules and a few or several sparsely granulated cells with small secretory granules. The densely granulated cells showed intense GH or PRL antigenicity and slight to moderate antigenicity for other hormones in large secretory granules and little or only weak antigenicity for various hormones including GH or PRL in small secretory granules. Their secretory granules larger than 160 nm or 140 nm significantly exhibited intense GH or PRL antigenicity (Fisher's exact test; P < 0.05 and < 0.01, respectively). Two CN-F adenomas showed sparsely and densely granulated cells as well as intermediate cells. The densely granulated cells closely resembled GH-secreting cells. The intermediate cells simultaneously included small and medium-sized or large secretory granules exhibiting little/slight and intense GH-antigenicity, respectively. This study indicates that sparsely granulated cells of different categories showing slight antigenicity for various hormones, antigenically share the same origin, and that their hormonality, single or multiple, may be selectively activated in the developmental course of secretory granules.

Fluorescence automatic cell sorter and immunohistochemical investigation of CD68-positive cells in meningioma

Infiltration of brain neoplasms by mononuclear cells including monocytes/macrophages has attracted little attention since they have marked morphological heterogeneity. Twenty-seven meningiomas were studied by anti-CD68 antibody-gated flow cytometry and by immunohistochemical analysis using the anti-CD68 antibodies. Flow cytometric analysis divided cells contained within tumor tissues into CD68-positive and -negative cells. In addition, eight gliomas, eight metastatic brain tumor, and 12 pituitary adenomas were investigated in the same way to compare meningiomas. The mean contents of CD68-positive cells were 24.0 +/- 3.7% in meningiomas, 4.4 +/- 1.4% in gliomas, 9.5 +/- 3.9% in metastatic brain tumors, and 4.5 +/- 1.8% in pituitary adenomas. Immunohistochemically, CD68-positive cells showed significant heterogeneity and were detected as round, rod-shaped, ameboid and ramified cells in meningiomas. Although the infiltrated mononuclear cells in gliomas have been investigated to some degree and showed that they express cytokines and/or growth factors, these infiltrated cells in meningioma have barely been studied. The CD68-positive cells detected in this study are likely to be monocytes, macrophages and microglias, and are presumed to be in various functional stages and to play important roles in growth regulation in meningioma.

[Detection of pituitary autoantibody in patients with pituitary tumors and hypopituitarism]

In 80 patients, 73 cases of pituitary tumours and 7 cases of hypopituitarism, we performed pituitary autoantibodies assays in serum samples because in our previous studies we had found a high prevalence of pituitary autoantibodies in several autoimmune endocrine disorders. To detect the presence of pituitary autoantibodies we applied 2 methods, radioimmunoassay (RIA) and immunoblotting. The RIA was performed by solid phase technique in human pituitary microsome-coated polyethylene tubes. Following incubation with diluted sera of the patients labelled 125I-protein A was added to the tubes to detect the retained antibodies. In the sera of 33 patients we detected the presence of antibodies; in the other 47 patients no antibodies were found. The majority of the patients with positive antibody results were previously treated by pituitary irradiation. To evaluate the molecular weights of pituitary autoantigens the microsomal proteins were separated on SDS PAGE, then electrophoretically transferred to nitrocellulose membranes and reacted with diluted sera of 30 antibody-positive patients. The nitrocellulose strips were incubated with labelled 125I-protein A and autoradiographed. Using immunoblotting, 13 out of these 30 patients we found autoantibodies reacting with pituitary microsomal antigens of different molecular weights, most frequently reacting with a 68 kDa autoantigen.

CONCLUSIONS

The prevalence of pituitary autoantibodies in patients with pituitary diseases is 41% lower than in autoimmune endocrine diseases. Pituitary autoantibodies usually appear in patients after pituitary irradiation or after neurosurgery followed by irradiation, but occur rarely in untreated patients with pituitary adenomas.

Simian virus 40 T antigen-induced gonadotroph adenomas: a model of human null cell adenomas

The cell of origin of human null cell pituitary adenomas is disputed. Although these tumors, by definition, do not produce any of the anterior pituitary hormones in vivo, they have been shown to express gonadotropin subunit genes, release gonadotropin hormones in vitro, and express the gonadotroph-associated transcription factor steroidogenic factor-1. However, they demonstrate variable responses to releasing hormones in vitro, raising questions about their origin from differentiated gonadotrophs or pluripotent stem cells. In this set of experiments, transgenic mice carrying a temperature-sensitive mutant (TSA58) of simian virus 40 T antigen driven by human FSHbeta regulatory elements were produced. These animals developed slow growing, multifocal pituitary nodules that demonstrated secretion of FSH with serum FSH levels 10-fold higher in male transgenic animals and 5-fold higher in female transgenic animals than those in nontransgenic controls. Anterior pituitary pathology progressed from diffuse gonadotroph hyperplasia to nodular adenomas with persistent, but decreasing, immunoreactivity for FSHbeta and LHbeta. Ultrastructural characteristics of the tumors were identical to those of human null cell adenomas. These results support the hypothesis that human null cell adenomas are derived from gonadotrophs and provide an animal model for further study of this disease.