Apoptosis in nontumorous and neoplastic human pituitaries: expression of the Bcl-2 family of proteins

The hallmarks of cancer… in pituitary tumors?

Over 20 years ago, Hanahan and Weinberg published a seminal review that addressed the biological processes that underly malignant transformation. This classical review, along with two revisions published in 2011 and 2022, has remain a classic of the oncology literature. Since many of the addressed biological processes may apply to non-malignant tumorigenesis, we evaluated to what extent these hallmarks pertain to the development of pituitary adenomas.Some of the biological processes analyzed in this review include genome instability generated by somatic USP8 and GNAS mutations in Cushing's diseases and acromegaly respectively; non-mutational epigenetic reprograming through changes in methylation; induction of angiogenesis through alterations of VEGF gene expression; promotion of proliferative signals mediated by EGFR; evasion of growth suppression by disrupting cyclin dependent kinase inhibitors; avoidance of immune destruction; and the promotion of inflammation mediated by alteration of gene expression of immune check points. We also elaborate further on the existence of oncogene induced senescence in pituitary tumors. We conclude that a better understanding of these processes can help us dilucidated why pituitary tumors are so resistant to malignant transformation and can potentially contribute to the development of novel anticancer treatments.

Architects of Pituitary Tumour Growth

The pituitary is a master gland responsible for the modulation of critical endocrine functions. Pituitary neuroendocrine tumours (PitNETs) display a considerable prevalence of 1/1106, frequently observed as benign solid tumours. PitNETs still represent a cause of important morbidity, due to hormonal systemic deregulation, with surgical, radiological or chronic treatment required for illness management. The apparent scarceness, uncommon behaviour and molecular features of PitNETs have resulted in a relatively slow progress in depicting their pathogenesis. An appropriate interpretation of different phenotypes or cellular outcomes during tumour growth is desirable, since histopathological characterization still remains the main option for prognosis elucidation. Improved knowledge obtained in recent decades about pituitary tumorigenesis has revealed that this process involves several cellular routes in addition to proliferation and death, with its modulation depending on many signalling pathways rather than being the result of abnormalities of a unique proliferation pathway, as sometimes presented. PitNETs can display intrinsic heterogeneity and cell subpopulations with diverse biological, genetic and epigenetic particularities, including tumorigenic potential. Hence, to obtain a better understanding of PitNET growth new approaches are required and the systematization of the available data, with the role of cell death programs, autophagy, stem cells, cellular senescence, mitochondrial function, metabolic reprogramming still being emerging fields in pituitary research. We envisage that through the combination of molecular, genetic and epigenetic data, together with the improved morphological, biochemical, physiological and metabolically knowledge on pituitary neoplastic potential accumulated in recent decades, tumour classification schemes will become more accurate regarding tumour origin, behaviour and plausible clinical results.

The effect of somatostatin analogues on Ki-67 levels in GH-secreting adenomas

PURPOSE

Somatostatin analogues (SSAs) can slow down the growth of neuroendocrine tumors. However, the mechanism remains unclear. Recent studies on patients with acromegaly suggest that SSAs may induce apoptosis, increase autophagy, and decrease cell proliferation of pituitary adenoma. Ki-67-labeling index is a marker of cellular proliferation; therefore, decreased levels are associated with inhibition of proliferation. The aim of this study was to evaluate and compare the Ki-67-labeling index of GH-secreting pituitary adenoma tissues in patients who had undergone pituitary surgery twice due to residual or recurrent tumors and had received SSA treatment between the two surgeries.

METHOD

Thirty acromegaly patients who met the above criteria were identified and evaluated for the demographic, clinical and radiological features retrospectively. Surgical pathology samples of each operation were stained for Ki-67 and evaluated blindly by a staff pathologist specialized in pituitary diseases.

RESULTS

Among patients who received SSA treatment between the first and second operations, the Ki-67 index of the adenoma at the second operation was significantly lower than the Ki-67 index at the first operation. There were no differences in clinical and radiological prognostic markers between the groups with decreased and unchanged Ki-67 index.

CONCLUSION

We concluded that SSA treatment appears to decrease Ki-67 proliferation index independent of tumor features, SSA type, dose and treatment duration. This result suggests that SSA treatment may decrease cellular proliferation, supporting the previous studies.

Expression of BCL-2, BAX and P53 Proteins in Pituitary Adenomas an Immunohistochemical Study

Aims and Background

Although pituitary adenomas are usually benign lesions, their growth rate is highly variable and unpredictable. Apoptosis appears to be an important process in neoplastic lesions. The purpose of this study was to investigate the expression of apoptosis-related proteins including Bcl-2, bax and p53 in pituitary adenomas and its correlation with hormone function, tumor size, local control, and proliferative activity.

Study Design

The expression of Bcl-2, Bax and p53 proteins and hormonal function were determined in formalin-fixed, paraffin-embedded tissue from 41 untreated pituitary adenomas using immunohistochemistry. The patients were followed for a median of 60 months (range, 12 to 95). Patient charts were reviewed to record tumor recurrence and size. Tumor proliferative activity was assessed by immunohistochemistry using Ki-67 antibody.

Results

Of 41 pituitary adenomas, 26 (63%) were hormone-secreting and 15 (37%) non-functioning, 34 (83%) were macroadenoma and 7 (17%) microadenoma, and 15 (37%) showed local relapse. Six (14%) adenomas were of low proliferative activity, whereas the others (86%) were non-proliferative. Immunohistochemically, 31 adenomas (75%) showed bcl-2 positivity, 37 (90%) bax positivity, and 7 (17%) p53 positivity. Statistical analysis revealed that Bcl-2 protein expression significantly diminished in prolactin-secreting and non-functioning adenomas (P = 0.005 and P = 0.006, respectively), and increased in growth hormone-secreting adenomas (P = 0.003). In addition, expression of bax protein significantly decreased in recurrent tumors, in contrast to p53 protein, which showed a significant increase (P = 0.03 and P = 0.002, respectively).

Conclusions

We think that apoptosis-related proteins such as Bcl-2, Bax and p53 may be significantly related to hormone function and local control in pituitary adenomas.

AT-101 acts as anti-proliferative and hormone suppressive agent in mouse pituitary corticotroph tumor cells

PURPOSE

Gossypol, a naturally occurring compound in cottonseeds, has anticancer effects against several tumor cell lines. It has been extensively studied in clinical trials and is well tolerated with a favorable safety profile. AT-101, a derivative of R (-)-gossypol, binds to Bcl-2 family proteins and induces apoptosis in vitro. Although transsphenoidal surgical excision of the pituitary corticotroph adenoma is the gold standard of care, it is not successful all the time. Medical therapy for Cushing's disease still remains a challenge for the clinicians. We aimed to investigate the cytotoxic and apoptotic effects of AT-101 in mouse pituitary corticotroph tumor AtT20 cells.

METHODS

Cytotoxic effect of AT-101 was assessed by XTT cell viability assay. Apoptosis was shown by measuring DNA fragmentation and Caspase-3/7 activity. Changes in mRNA expressions of apoptosis-related genes were investigated by qPCR array after treatment with AT-101. ACTH was measured by ACTH-EIA Kit.

RESULTS

AT-101 induced cytotoxicity and apoptosis in AtT20 cells. mRNA levels of pro-apoptotic genes such as TNFR-SF-10B, Bid, PYCARD, Caspase-8, Caspase-3, and Caspase-7 were induced by 2.0-, 1.5-, 1.7-, 1.5-, 1.6-, and 2-fold, respectively, in AtT20 cells by AT-101 treatment. Moreover, some of the anti-apoptotic genes such as BCL2L10, NAIP1, and PAK-7 were reduced by 2.1-, 2.3-, 4.0-fold, respectively, in AtT20 cells. AT-101 also decreased ACTH secretion significantly.

CONCLUSION

AT-101 induces apoptosis in mouse pituitary corticotroph tumor cells.

Stem/progenitor cells in pituitary organ homeostasis and tumourigenesis

Evidence for the presence of pituitary gland stem cells has been provided over the last decade using a combination of approaches including in vitro clonogenicity assays, flow cytometric side population analysis, immunohistochemical analysis and genetic approaches. These cells have been demonstrated to be able to self-renew and undergo multipotent differentiation to give rise to all hormonal lineages of the anterior pituitary. Furthermore, evidence exists for their contribution to regeneration of the organ and plastic responses to changing physiological demand. Recently, stem-like cells have been isolated from pituitary neoplasms raising the possibility that a cytological hierarchy exists, in keeping with the cancer stem cell paradigm. In this manuscript, we review the evidence for the existence of pituitary stem cells, their role in maintaining organ homeostasis and the regulation of their differentiation. Furthermore, we explore the emerging concept of stem cells in pituitary tumours and their potential roles in these diseases.

Case report: ACTH-secreting pituitary carcinoma metastatic to the liver in a patient with a history of atypical pituitary adenoma and Cushing's disease

Background

Pituitary carcinoma is a rare entity requiring the presence of metastasis to confirm its malignant potential. We report a case of pituitary carcinoma and discuss the diagnosis and management of this lesion in relation to the existing literature.

Case presentation

The patient is a 51-year-old woman with Cushing’s disease and intact adrenal glands who was diagnosed with metastatic pituitary carcinoma to the liver, 29 months after initial resection of an ACTH-secreting primary atypical pituitary adenoma (APA). Prior to detection of this metastasis the patient underwent repeat resection and radiotherapy for residual cavernous sinus disease. The metastatic lesion was detected by interval surveillance of serum ACTH and 24-hour urine cortisol, which despite stable pituitary MRI, were significantly elevated. These abnormalities prompted a PET scan that demonstrated hypermetabolic liver parenchyma, which was suspicious for metastasis on abdominal MRI. An ultrasound-guided liver biopsy demonstrated nests of moderately-differentiated cells with intermediate-sized, monotonous nuclei, distinct nucleoli, and abundant basophilic cytoplasm, confirmed by immunohistochemistry to represent metastatic pituitary carcinoma. The liver lesion was subsequently successfully removed by wedge resection. One year later, the patient’s residual cavernous sinus disease grew markedly, and she was placed on dual-agent chemotherapy consisting of oral temozolomide and capecitabine, with stabilization of her intracranial disease to present, although liver metastases recurred.

Conclusions

Pituitary carcinoma is a rare entity impossible to recognize as a primary tumor because its diagnosis by definition requires the presence of metastasis. Maintaining awareness of the entity and its precursor lesion APA is essential for its accurate pathologic diagnosis and appropriate management.

Genetic aspects of pituitary carcinoma: A systematic review

BACKGROUND

Pituitary carcinoma (PC) is a rare type of malignant intracranial neoplasm defined as distant metastasis of pituitary adenoma (PA). Although PC incidence is low because only 0.1% to 0.2% of PAs ultimately develop into PCs, the prognosis is poor and 66% of patients die within the first year. Existing therapeutic measures, including surgical removal, chemotherapy, and radiotherapy, have limited effectiveness. The lack of efficacy of current treatments is largely caused by the limited understanding of the molecular pathogenesis of PA and the malignant transformation to PC. Therefore, the aim of this systematic review was to summarize published research regarding gene and protein expression in PC to clarify the molecular mechanisms underlying PC genesis and development and identify new candidate diagnostic biomarkers and therapeutic targets for potential use in personalized treatment of PC.

METHODS

We followed the PRISMA guidelines to plan and conduct this systematic review. PubMed, Embase, and Web of Science databases were searched for relevant studies conducted before December 16, 2015 describing the association of PC with gene expression at the mRNA and protein levels. MeSH terms combined with free terms were used to retrieve the references.

RESULTS

In total, 207 records were obtained by primary search, and 32 were included in the systematic review. Compared with normal pituitary gland and/or PA, 30 and 18 genes were found to have higher or lower expression, respectively, in PCs using different analytical methods. Among them, we selected 9 upregulated and 7 downregulated genes for further analysis based on their identification as candidate treatment targets in other cancers, potential clinical application, or further research value.

CONCLUSION

Previous studies demonstrated that many genes promote PC malignant transformation, angiogenesis, invasion, metastasis, and recurrence. Although most of these genes and proteins have not been fully analyzed with regard to their downstream mechanisms or potential diagnostic and therapeutic application, they have the potential to become candidate PC biomarkers and/or molecular targets for guiding personalized treatment. Modern advanced technologies should be utilized in future research to identify more candidate genes for PC pathogenesis, as precisely targeted gene therapies against PC are urgently required.

Diagnostic criteria in invasive pituitary adenomas

Pituitary adenomas are benign pituitary primary tumors, the most frequent type of tumor in the pituitary fossa. An important part, around 1/3 of the pituitary adenomas manifests an aggressive behavior, growing faster and invading into parasellar areas (cavernous sinus, neural tissues and bones). Objectives: the first aim of this paper is to review the last findings about invasiveness diagnostic criteria, imagistic and biomarkers, which can be used in the classification of pituitary tumors and also to predict the probability of invasiveness, tumor recurrence and suspicion of malignancy. The second aim is to highlight the morphological and clinic types of invasive pituitary adenomas. Materials and methods: we performed a systematic review and analysis of the published articles, searching PubMed between January 1985 and December 2015. There were selected articles published in English, reviews and abstracts. During the advanced search type in PubMed, combinations of the following keywords were used: “pituitary adenoma”, “invasive”, “aggressive”, “biomarkers”, “classification”, “histological subtypes”, ‘”immunohistochemical markers”. Results: 215 articles were selected, regarding diagnostic, prognostic and therapeutic aspects. There were some histological subtypes of pituitary adenomas known as having an aggressive clinical behavior. Several biomarkers were identified as being associated with the invasive feature: proliferation markers (Ki-67 index, number of mitoses, p53 & p27 expression, microvascularization density, telomerase, topoisomerase 2 Alpha), matrix metalloproteinases, protein kinase C, cyclooxygenase-2, E-cadherin, transcription Factors, genetic alterations (PTTG gene, Galectin-3 protein/ LGALS3 gene), apoptosis markers. Based on their invasion and proliferation characteristics, pituitary tumors are proposed to be classified into five grades (1a, 1b, 2a, 2b, 3), the grade 2b tumor with high risk of recurrence being considered as tumor suspected of malignancy. Conclusions: Using a set of specific biological markers for invasive process, there is hope to establish an early diagnosis and prevention of invasive pituitary adenomas. Due to the fact that aggressive pituitary tumors are generally difficult to manage, unresponsive to therapy, quickly recurrent and associated with poor prognosis, the early diagnosis and the search for new therapeutic approaches is becoming mandatory. Instead of using “invasive” or “aggressive” adenoma, the term “tumor suspected of malignancy” would be used for more accuracy

Biomarkers of pituitary carcinomas

Pituitary carcinoma is a rare tumor originating from adenohypophyseal cells. Currently, diverse pathogenetic mechanisms, i.e. de novo versus malignant transformation from pituitary adenoma, remain obscure and require further investigation. During the last two decades, scientific research added new horizons not only in regards to general tumor concepts but also in next generation biomarker armamentarium that sheds light on alternate pathways in carcinogenesis. Areas covered: In this review, the impact of apoptotic and proliferative markers, angiogenesis, telomerase activity, H-ras, HIF-1, HER-2/neu, Rb gene, and microRNAs in pathogenetic mechanisms of pituitary carcinomas were revised. Expert commentary: It is becoming increasingly important for the need of standardization of new biomarkers but also for better comprehension of the diverse pathways in tumorigenesis. This can only be accomplished by tapping into the continuously expanding spectrum of new biomarkers.

Pituitary Cell Turnover: From Adult Stem Cell Recruitment through Differentiation to Death

The recent demonstration using genetic tracing that in the adult pituitary stem cells are normally recruited from the niche in the marginal zone and differentiate into secretory cells in the adenopituitary has elegantly confirmed the proposal made when the pituitary stem cell niche was first discovered 5 years ago. Some of the early controversies have also been resolved. However, many questions remain, such as which are the markers that make a pituitary stem cell truly unique and the exact mechanisms that trigger recruitment from the niche. Little is known about the processes of commitment and differentiation once a stem cell has left the niche. Moreover, the acceptance that pituitary cells are renewed by stem cells implies the existence of regulated mechanisms of cell death in differentiated cells which must themselves be explained. The demonstration of an apoptotic pathway mediated by RET/caspase 3/Pit-1/Arf/p53 in normal somatotrophs is therefore an important step towards understanding how pituitary cell number is regulated. Further work will elucidate how the rates of the three processes of cell renewal, differentiation and apoptosis are balanced in tissue homeostasis after birth, but altered in pituitary hyperplasia in response to physiological stimuli such as puberty and lactation. Thus, we can aim to understand the mechanisms underlying human disease due to insufficient (hypopituitarism) or excess (pituitary tumor) cell numbers.

Apoptosis: its role in pituitary development and neoplastic pituitary tissue

Apoptosis, also known as programmed cell death, is a phenomenon in which different stimuli trigger cellular mechanisms that culminate in death, in the absence of inflammatory cell response. Two different activation pathways are known, the intrinsic pathway (or mitochondrial) and extrinsic (or death-receptor pathway), both pathways trigger enzymatic reactions that lead cells to break up and be phagocytized by neighboring cells. This process is a common occurrence in physiological and pathological states, participating in the control of cell proliferation, differentiation and remodeling of organs. In the early steps of pituitary gland formation, numerous apoptotic cells are detected in the separation of Rathke's pouch from the roof of oral ectoderm. In the distal part of the gland, which will form the adenohypophysis, the ratio of apoptosis was significantly lower. However, there is evidence that neoplastic pituitary cells undergo unbalance in genes that control apoptosis leading to uncontrolled cell growth. No direct evidence of apoptosis was found in the drugs used for tumors producing prolactin and growth hormone. In conclusion, an unbalancing in the apoptosis process is the boundary between development and tumor growth.

MicroRNAs in Human Pituitary Adenomas

MicroRNAs (miRNAs) are a class of recently identified noncoding RNAs that regulate gene expression at posttranscriptional level. Due to the large number of genes regulated by miRNAs, miRNAs play important roles in many cellular processes. Emerging evidence indicates that miRNAs are dysregulated in pituitary adenomas, a class of intracranial neoplasms which account for 10-15% of diagnosed brain tumors. Deregulated miRNAs and their targets contribute to pituitary adenomas progression and are associated with cell cycle control, apoptosis, invasion, and pharmacological treatment of pituitary adenomas. To provide an overview of miRNAs dysregulation and functions of these miRNAs in pituitary adenoma progression, we summarize the deregulated miRNAs and their targets to shed more light on their potential as therapeutic targets and novel biomarkers.

Growth hormone is a cellular senescence target in pituitary and nonpituitary cells

Premature proliferative arrest in benign or early-stage tumors induced by oncoproteins, chromosomal instability, or DNA damage is associated with p53/p21 activation, culminating in either senescence or apoptosis, depending on cell context. Growth hormone (GH) elicits direct peripheral metabolic actions as well as growth effects mediated by insulin-like growth factor 1 (IGF1). Locally produced peripheral tissue GH, in contrast to circulating pituitary-derived endocrine GH, has been proposed to be both proapoptotic and prooncogenic. Pituitary adenomas expressing and secreting GH are invariably benign and exhibit DNA damage and a senescent phenotype. We therefore tested effects of nutlin-induced p53-mediated senescence in rat and human pituitary cells. We show that DNA damage senescence induced by nutlin triggers the p53/p21 senescent pathway, with subsequent marked induction of intracellular pituitary GH in vitro. In contrast, GH is not induced in cells devoid of p53. Furthermore we show that p53 binds specific GH promoter motifs and enhances GH transcription and secretion in senescent pituitary adenoma cells and also in nonpituitary (human breast and colon) cells. In vivo, treatment with nutlin results in up-regulation of both p53 and GH in the pituitary gland, as well as increased GH expression in nonpituitary tissues (lung and liver). Intracrine GH acts in pituitary cells as an apoptosis switch for p53-mediated senescence, likely protecting the pituitary adenoma from progression to malignancy. Unlike in the pituitary, in nonpituitary cells GH exerts antiapoptotic properties. Thus, the results show that GH is a direct p53 transcriptional target and fulfills criteria as a p53 target gene. Induced GH is a readily measurable cell marker for p53-mediated cellular senescence.

Loss of 15-hydroxyprostaglandin dehydrogenase indicates a tumor suppressor role in pituitary adenomas

15-hydroxyprostaglandin dehydrogenase (15-PGDH) may function as a tumor suppressor that antagonizes the action of the cyclooxygenase-2 (COX-2) oncogene in several types of tumors. However, it is unknown if it has a role in the pituitary. Recently, our group found that 15-PGDH expression was low in prolactin (PRL) secreting adenomas (prolactinomas) and growth hormone (GH) secreting adenomas (GHomas) using fiber-optic BeadArray technology. In this study, we examined the relative expression of 15-PGDH and COX-2 mRNA in clinical specimens and examined the effects of 15-PGDH on GH3 rat pituitary tumor cell proliferation, apoptosis and hormone secretion. 15-PGDH expression was lower and COX-2 expression was higher in prolactinomas and GHomas compared with normal controls. Overexpressed 15-PGDH inhibited tumor cell proliferation and induced apoptosis. It had a significant suppressive effect on mRNA levels and on the secretion of PRL and GH in GH3 cells. The inhibition of cell proliferation was accompanied by the decreased expression of cox-2, matrix metalloproteinase-9 (MMP-9) and B cell leukemia/lymphoma-2 (Bcl-2). These data are suggestive of a previously unrecognized pathway in pituitary tumorigenesis, and this novel observation may shed light on therapeutic strategies for pituitary tumors.

Cell proliferation parameters and apoptosis indices in pituitary macroadenomas

BACKGROUND

Pituitary adenomas are usually well-differentiated tumors but may show locally aggressive behavior.

AIM

To investigate the relationship between proliferation and apoptosis parameters and tumor recurrence in a series of 20 radically resected pituitary macroadenomas (11 functioning, 9 non-functioning).

MATERIALS AND METHODS

Proliferative activity and DNA ploidy were analyzed by flow cytometry (FCM) on fresh surgical specimens. Immunohistochemistry for Ki-67/MIB-1 and for the anti-apoptotic protein Bcl-2 was performed on paraffin-embedded specimens from the same tumors. Tumor regrowth was evaluated by magnetic resonance imaging (MRI).

RESULTS

Six adenomas recurred after surgery, regardless of hormonal hypersecretion. Pre-surgical tumor size was significantly higher in recurrent than in non-recurrent adenomas (p=0.003). Pre-surgical MRI demonstrated cavernous sinus (CS) invasiveness in all recurrent tumors, while none of the non-invasive adenomas recurred (p=0.042, by Fisher's exact test). The DNA content was aneuploid in 5/20 adenomas, one of which recurred. Cell percentages in the S (%SPF) and G2+M (%G2-M) phases and proliferative index (PI) (PI=%SPF+%G2-M) were significantly higher in aneuploid than in diploid adenomas (p<0.05), but no significant differences concerning all FCM parameters were observed between recurrent and non-recurrent adenomas. Similarly, MIB-1 did not show a significant difference of expression between recurrent and non-recurrent adenomas (p=0.33). Bcl-2 immunoreactivity was detected in 12/15 pituitary adenomas, involving 63±35% of tumor cells, regardless of tumor recurrence.

CONCLUSIONS

In this group of radically resected pituitary macroadenomas, neuroradiological finding of CS invasiveness--but not FCM parameters nor MIB-1 and Bcl-2 expression--is useful for predicting tumor recurrence.

Osteocyte apoptosis and absence of bone remodeling in human auditory ossicles and scleral ossicles of lower vertebrates: a mere coincidence or linked processes?

Considering the pivotal role as bone mechanosensors ascribed to osteocytes in bone adaptation to mechanical strains, the present study analyzed whether a correlation exists between osteocyte apoptosis and bone remodeling in peculiar bones, such as human auditory ossicles and scleral ossicles of lower vertebrates, which have been shown to undergo substantial osteocyte death and trivial or no bone turnover after cessation of growth. The investigation was performed with a morphological approach under LM (by means of an in situ end-labeling technique) and TEM. The results show that a large amount of osteocyte apoptosis takes place in both auditory and scleral ossicles after they reach their final size. Additionally, no morphological signs of bone remodeling were observed. These facts suggest that (1) bone remodeling is not necessarily triggered by osteocyte death, at least in these ossicles, and (2) bone remodeling does not need to mechanically adapt auditory and scleral ossicles since they appear to be continuously submitted to stereotyped stresses and strains; on the contrary, during the resorption phase, bone remodeling might severely impair the mechanical resistance of extremely small bony segments. Thus, osteocyte apoptosis could represent a programmed process devoted to make stable, when needed, bone structure and mechanical resistance.

CtBP1 interacts with Ikaros and modulates pituitary tumor cell survival and response to hypoxia

C-terminal binding protein (CtBP) is a transcriptional corepressor that plays an important role in mammalian development and tumorigenesis. We demonstrate that CtBP is expressed in adenohypophyseal cells and is expressed at high levels in human corticotroph, somatotroph, and lactotroph pituitary adenomas. CtBP interacts with Ikaros isoforms in GH4 and AtT20 pituitary tumor cells. Ikaros and CtBP1 expression is coordinately induced by hypoxia, and this response is abrogated by CtBP1 deficiency. Forced reduction of CtBP1 leads to reduced cell growth, up-regulation of Sprouty 2, and down-regulation of ectonucleotide pyrophosphatase phosphodiesterase 2 (Enpp2). Consistent with diminished Enpp2 activity, CtBP1-deficient pituitary cells are more susceptible to hypoxia-induced apoptosis, which is rescued by Enpp2-derived lysophosphatidic acid treatment. These results identify putative oncogenic properties of CtBP1 and provide new insights into the overlapping functions of two members of the chromatin remodeling network in the response to hypoxic pituitary tumor cell drive.

MicroRNA profile indicates downregulation of the TGFβ pathway in sporadic non-functioning pituitary adenomas

MicroRNAs (miRs) are small, 16-29 nucleotide long, non-coding RNA molecules which regulate the stability or translational efficiency of targeted mRNAs via RNA interference. MiRs participate in the control of cell proliferation, cell differentiation, signal transduction, cell death, and they play a role in carcinogenesis. The aims of our study were to analyse the expression profile of miRs in sporadic clinically non-functioning pituitary adenomas (NFPA) and in normal pituitary tissues, and to identify biological pathways altered in these pituitary tumors. MiR expression profiles of 12 pituitary tissue specimens (8 NFPA and 4 normal pituitary tissues) were determined using miR array based on quantitative real-time PCR with 678 different primers. Five overexpressed miRs and mRNA expression of Smads (Smad1-9), MEG and DLK1 genes were evaluated with individual Taqman assays in 10 NFPA and 10 normal pituitary tissues. Pathway analysis was performed by the DIANA-mirPath tool. Complex bioinformatical analysis by multiple algorithms and association studies between miRs, Smad3 and tumor size was performed. Of the 457 miRs expressed in both NFPA and normal tissues, 162 were significantly under- or overexpressed in NFPA compared to normal pituitary tissues Expression of Smad3, Smad6, Smad9, MEG and DLK1 was significantly lower in NFPA than in normal tissues. Pathway analysis together with in silico target prediction analysis indicated possible downregulation of the TGFβ signaling pathway in NFPA by a specific subset of miRs. Five miRs predicted to target Smad3 (miR-135a, miR-140-5p, miR-582-3p, miR-582-5p and miR-938) were overexpressed. Correlation was observed between the expression of seven overexpressed miRs and tumor size. Downregulation of the TGFβ signaling through Smad3 via miRs may have a possible role in the complex regulation of signaling pathways involved in the tumorigenesis process of NFPA.

Biomarkers of pituitary neoplasms: a review (Part II)

Several new markers have shown a capacity to predict the clinicopathological behavior of pituitary neoplasms; these markers have shown potential to correlate with tumor subtype and size and patient age and sex. These various markers are involved in a host of cellular functions, including cell-cycle progression, cell proliferation, apoptosis, cell adhesion, and tumor vascularity. In this companion article to our first review of Ki-67 as a marker of pituitary adenomas, we present and analyze the literature regarding matrix metalloproteinases and their inhibitors (tissue inhibitor metalloproteinases), vascular endothelial growth factor, fibroblast growth factor and its receptor, apoptotic markers and p53, as well as cyclooxygenase-2, galectin-3, and pituitary tumor transforming gene. Some of these markers, such as fibroblast growth factor and fibroblast growth factor receptor and matrix metalloproteinases, show particular promise in their ability to identify pituitary tumors that behave in an aggressive manner. We suggest the need for uniform design and application of methods and standardized criteria for the interpretation of results. A uniform approach will establish clinicopathological utility of emerging markers.

Pituicytoma: characterization of a unique neoplasm by histology, immunohistochemistry, ultrastructure, and array-based comparative genomic hybridization

The pituicytoma is a rare neoplasm whose histogenesis is debated partly because of the diversity of tissue types present in the sellar region. In this article we illustrate the characteristic histologic, immunohistologic, and ultrastructural features of this unique neoplasm. Furthermore, we use array-based comparative genomic hybridization to demonstrate a unique pattern of genomic copy number aberrations in pituicytomas. Tumors were composed of bipolar, spindle cells that were immunopositive for S100, vimentin, and Bcl-2 and immunonegative for synaptophysin, chromogranin, and glial fibrillary acidic protein. Ultrastructural analysis was remarkable for absence of secretory granules. Array comparative genomic hybridization demonstrated genomic copy number imbalances, including losses on chromosome arms 1p, 14q, and 22q and gains on 5p. This pattern of genetic changes only partially overlaps with the genomic alterations reported in pituitary adenomas. In summary, our data suggest that pituicytomas are a unique subset of tumors of the sellar region.

Pituicytoma: characterization of a unique neoplasm by histology, immunohistochemistry, ultrastructure, and array-based comparative genomic hybridization

The pituicytoma is a rare neoplasm whose histogenesis is debated partly because of the diversity of tissue types present in the sellar region. In this article we illustrate the characteristic histologic, immunohistologic, and ultrastructural features of this unique neoplasm. Furthermore, we use array-based comparative genomic hybridization to demonstrate a unique pattern of genomic copy number aberrations in pituicytomas. Tumors were composed of bipolar, spindle cells that were immunopositive for S100, vimentin, and Bcl-2 and immunonegative for synaptophysin, chromogranin, and glial fibrillary acidic protein. Ultrastructural analysis was remarkable for absence of secretory granules. Array comparative genomic hybridization demonstrated genomic copy number imbalances, including losses on chromosome arms 1p, 14q, and 22q and gains on 5p. This pattern of genetic changes only partially overlaps with the genomic alterations reported in pituitary adenomas. In summary, our data suggest that pituicytomas are a unique subset of tumors of the sellar region.

Determination of cell proliferation using Mcm2 antigen and evaluation of apoptosis and TGF-beta1 expression in GH-secreting or clinically nonfunctioning pituitary adenomas

Pituitary adenomas (PA) occasionally show aggressive behavior, with invasion of the surrounding tissues. The identification of markers able to recognize aggressive PA in early stages remains a challenge. We aimed to determine the expression of a new cell proliferation marker, Mcm2, and the presence of apoptosis in PA, and to evaluate the association of clinicopathological features with the apoptotic and proliferative indices. Additionally, the TGF-beta1 expression, an inducer of apoptosis, was determined. The proliferative index was determined in GH-secreting or clinically nonfunctioning PA using immunohistochemical (IH) methods for Mcm2 and Ki-67 antigens. The apoptosis was assessed by the TUNEL method and the TGF-beta1 expression by IH. A significant positive correlation was found between log Mcm2 index and log Ki-67 index (p < 0.001). Mcm2 and Ki-67 detected a similar number of proliferating cells. Mcm2 index showed a significant association with tumor extension (p = 0.02), but not with tumor invasion. Apoptosis was detected in 17% of the adenomas, with a maximum apoptotic index of 0.77%. Immunoreactivity to TGF-beta1 was observed in 77% of the adenomas, showing an association with tumor extension. We concluded that, in this sample, Mcm2 was similar to Ki-67 in the identification of the proliferating cells and that apoptosis was rare.

Effects of TGFbeta1 on gene expression in the HP75 human pituitary tumor cell line identified by gene expression profiling

The pathogenesis of pituitary adenomas and many of the genes influencing growth of these tumors are unknown. TGFbeta is known to inhibit proliferation of cultured anterior pituitary cells and anterior pituitary tumors, but the signal transduction pathways involved in the inhibition of growth are unclear. We treated the human HP75 pituitary cell line with 10(-9) M TGFbeta1 for 4, 24, and 96 h and performed global gene expression profiling by Affymetrix GeneChip microarray analysis. Quantitative PCR validation of specific genes involved in the TGFbeta1-induced regulation of pituitary cell growth was also done. Of the 15,000 genes queried, there were 37 genes up-regulated and 48 genes down-regulated twofold or more after 4 h of TGFbeta1 treatment. There were 121 genes up-regulated and 109 genes down-regulated twofold or more after 24 h of TGFbeta1 treatment and 112 genes up-regulated and 43 genes down-regulated twofold or more after 96 h of TGFbeta1 treatment. Galectin-3 (Gal-3) protein was decreased by TGFbeta1 treatment and several genes which interacted with Gal-3 including RUNX1 and WNT5B were up-regulated after TGFbeta1 treatment. SOX4 was also up-regulated by TGFbeta1 treatment. SMAD3, which is directly involved in the TGFbeta signal transduction pathway, was down-regulated by TGFbeta1 treatment. These findings highlight the diverse gene networks and pathways through which TGFbeta operates in its effects on pituitary tumor cells.

Morphologic changes of prolactin-producing pituitary adenomas after short treatment with dopamine agonists

Treatment of patients with prolactin (PRL)-producing pituitary adenomas with dopamine agonists has proved successful for most cases. Dopamine agonists inhibit PRL secretion, suppress cell proliferation, and may induce apoptosis to adenoma cells. Dopamine agonists induce striking morphologic changes in the majority of treated PRL-producing adenomas. To date, these morphologic effects have been primarily described only after long-term treatment. To the best of our knowledge, no similar studies have investigated apoptotic alterations induced after short-term therapy. The purpose of this report is to describe the morphologic changes seen in PRL-producing adenomas after short-term dopamine agonist treatment. We present two cases of PRL-producing macroadenomas, both from male patients who received treatment with dopamine agonists, the first for 5 and the second for 8 days. In contrast to long-term treatment, no striking reduction of PRL immunoreactivity was noted. Slight stromal fibrosis was noted in case 1, which contained several cells all in late phase of apoptosis. In addition to typical apoptotic cells, numerous "dark" cells representing another common form of cell death were also noted. These novel findings represent characteristic features of short-term dopamine agonist treatment, which are not seen in long-term treatment.

Immunocytochemical detection of 14-3-3 in primary nervous system tumors

14-3-3 proteins have attracted much recent interest in the etiopathogenesis of human cancers owing to their involvement in the prevention of apoptosis. However, the expression of 14-3-3 in primary nervous system tumors has not been previously characterized. In this paper, Immunohistochemistry using a specific anti-14-3-3 antibody was performed on formalin-fixed, paraffin embedded archival tissue from 124 primary human nervous system tumors and 10 normal brain tissues. In the normal control brains, 14-3-3 immunoreactivity was localized mainly in the neuronal somata and processes, and some glial cells showed only weak immunoreactivity. However, 14-3-3 immunoreactivity was seen in the majority of astrocytomas [grade I (9/11), II (16/21), III (13/17), IV (17/21)]. There was no difference between the positive expression rates of 14-3-3 in different grades of astrocytomas (P = 0.968). But the intensity and degree of 14-3-3 immunoreactivity in diffuse astrocytomas, anaplastic astrocytoma, and glioblastoma multiformes showed trends with tumor grade, with glioblastomas having the highest positivity (P = 0.048). The 14-3-3 immunoreactivity was also seen in the majority of other gliomas [oligodendroglioma (2/3), anaplastic oligodendroglioma (4/4), ependymoma (1/2), anaplastic ependymoma (2/2), choroid plexus papilloma (3/3), pineocytoma (2/2), medulloblastoma (5/8)]. All meningiomas [syncytical (3), fibrous/fibroblastic (4), angiomatous (4), transitional/mixed (3)] were intensely and diffusely positive. All schwannomas (4), neurofibromas (2), pituitary adenomas (6) and craniopharyngiomas(4) also showed intense positive staining. These results showed that 14-3-3 is expressed in the majority of the primary human nervous system tumors. The up-regulated expression of 14-3-3 may be a common mechanism for evading apoptosis in most primary human nervous system tumors, and targeting 14-3-3 may be a novel promising strategy for the treatment of these tumors, especially for malignant tumors.

Pituitary tumors: prognostic indicators

Many factors influence the proliferation of pituitary adenomas: angiogenesis, apoptosis, growth factors, oncogenes, tumor suppressor genes, and hormone receptors. These elements can be demonstrated by immunohistochemistry and/or molecular pathology but no single factor can be used for determination of biological behavior resp. prognosis. Pituitary adenomas can be enclosed or invasive and may be very large or may be microadenomas, but the most important point for prognosis is the total resection in the first or second surgery or the reaction on treatments by drugs. Especially for residual tumor tissue proliferation, markers are important because they may indicate the growth rate and the aggressiveness of the tumor. Radiation therapy is indicated in many of these recurrent tumors and can improve the prognosis.

Prognostic indicators in pituitary tumors

Recent advances in molecular pathology have shed light not only on the cellular composition and derivation of various tumors, but also on their growth potential, likelihood of recurrence, and prognosis. The development of reliable and prognostically informative methods of assessing tumor behavior is particularly important in pituitary tumors, where no precise correlation exists between morphology and clinical aggressiveness. Among the numerous morphologic techniques that have been introduced in the last three decades, some have gained popularity due to their reliability and ease of performance, whereas others have fallen from favor due to their inconsistency and insensitivity in distinguishing indolent from aggressive pituitary tumors. Yet others, due to cost and complexity, never came into general use. We predict that the immunohistochemical methods now in use for assessment of tumor behavior will be complemented and partly replaced by molecular genetic procedures in the future.

Chromogranin A transcription and gene expression in Folliculostellate (TtT/GF) cells inhibit cell growth

Folliculostellate (FS) cells are present in the anterior pituitary and have important regulatory functions including controlling hormone release from other anterior pituitary cells. FS cells do not usually express neuroendocrine genes such as chromogranin A (CgA). We analyzed transcriptional regulation and gene expression in the TtT/GF FS cell line to better understand the role of FS cells in anterior pituitary function. After transient transfection with a human (h) CgA promoter sequence linked to a luciferase reporter, there was basal level of transcriptional activity, which was two- to fourfold less than that observed in the anterior pituitary neuroendocrine cell lines HP75 and GH3. The transcriptional activity was decreased in all cell lines when a mutant hCgA promoter cyclic AMP response element (CRE) was used for transfection. Sodium butyrate treatment increased the transcriptional activity in all cell lines, but remained two- to fourfold higher in the HP75 and GH3 cell lines than in the TtT/GF cells. Stable transfection of a plasmid expressing bovine (b) CgA in the TtT/GF cells led to inhibition of cell growth as measured by 3H-thymidine incorporation, Ki-67 labeling index, and growth curve analysis. CgA protein and mRNA could be readily demonstrated in the cloned cells but not in the parental cell line or vector control cells. When the CgA expressing cloned cells were injected into SCID mice, there was a decrease in the rate of tumor growth compared to the vector control in vivo. These results indicate that the TtT/GF FS cells are fibroblast-like compared to the neuroendocrine anterior pituitary secretory cells when analyzed by transcriptional activity with a transiently transfected CgA promoter. In TtT/GF cells with a stably transfected bCgA plasmid, CgA has a direct regulatory effect on tumor cell proliferation.

Pituicytoma: Report of Two Cases and Clues Regarding Histogenesis

OBJECTIVE AND IMPORTANCE

The pituicytoma is a rare primary tumor of the neurohypophysis. Although histologically benign, the location and vascular nature of these tumors can make surgical resection difficult. We present a report of two patients with pituicytomas and review the literature regarding treatment and prognosis for this unusual lesion. Possible histogenetic relationships of this tumor with other pituitary neoplasms are presented.

CLINICAL PRESENTATION

Patient 1 was a 45-year-old man who presented with a 5-year history of decreased libido. He was found to have a 2-cm suprasellar mass on a magnetic resonance imaging scan. Patient 2 was a 48-year-old man who presented with multiple endocrine complaints. He was found to have an intrasellar mass on magnetic resonance imaging.

INTERVENTION

Patient 1 underwent a right frontal craniotomy, with a subtotal resection of the suprasellar mass through the lamina terminalis. The residual tumor was treated with fractionated stereotactic radiotherapy. The intrasellar mass in Patient 2 was resected via a transsphenoidal approach. On surveillance magnetic resonance imaging, the tumor was found to have recurred and expanded into the suprasellar space. The patient underwent a right frontal craniotomy for decompression and a subtotal resection of the tumor. The patient experienced a second recurrence 7 years after the initial procedure and was subsequently treated with fractionated stereotactic radiotherapy.

CONCLUSION

Pituicytomas are a distinct form of pituitary gland neoplasia that may recur if subtotally resected. These neurohypophysial tumors may contain a small subpopulation of previously unrecognized bcl-2-immunoreactive cells, whose role in the histogenesis of pituicytoma deserves further study.

Apoptosis during intramembranous ossification

This paper concerns the role of apoptosis during the onset of bone histogenesis. Previous investigations by us performed on intramembranous ossification revealed the existence of two types of osteogenesis: static (SBF) and dynamic bone formation (DBF). During SBF, the first to occur, stationary osteoblasts transform into osteocytes in the same location where they differentiated, forming the primary spongiosa. DBF takes place later, when movable osteoblastic laminae differentiate along the surface of the primary trabeculae. The main distinctive feature between SBF and DBF is that the latter involves the invasion of pre-existing adjacent tissue, whereas the former does not. To ascertain whether programmed cell death during the invasive DBF process determines the fate of surrounding pre-existing mesenchyme differently from that occurring during the non-invasive SBF process, we studied apoptosis in ossification centres of tibial diaphysis in chick embryos and newborn rabbits with TUNEL and TEM. It emerged that, in both SBF and DBF, apoptosis affects mesenchymal cells located between the forming trabeculae and capillaries. However, apoptotic cells were observed more frequently during DBF than during SBF. This suggests that, during bone histogenesis, apoptosis, which is mostly associated with the invasive process of DBF, is probably dedicated to making space for advancing bone growth.

The influence of treatment with somatostatin analogues on morphology, proliferative and apoptotic activity in GH-secreting pituitary adenomas

With the aim to investigate histopathological changes and proliferative and apoptotic activity in GH-secreting adenomas we compared 14 cases pre-treated with somatostatin analogues before surgery with a reference group of 17 un-pretreated ones. Besides routine histology, immunocytochemical detection of all pituitary hormones, caspase-3, cytokeratin-18, and "M30 antigen", its apoptosis-specific fragment was performed. Proliferation activity of the tumour was determined by the Ki-67 antigen expression. In treated adenomas more prominent regressive changes were found accompanied by compensatory increase in perivascular fibrosis. The Ki-67 labelling index was lower in treated group (mean 2.5, median 1.6 per mille) than in untreated patients (mean 9.4, median 5.0 per mille). The difference was statistically significant (p=0.049 using Mann-Whitney Rank Sum Test). Apoptosis was detected in only 2 of the 14 pre-treated adenomas, and it was more frequent (9/17) and more prominent in the untreated group.

Apoptosis is involved in the cardiac damage induced by sinoaortic denervation in rats

1. The arterial baroreflex plays an important role in the maintenance of the stability of blood pressure. Sinoaortic denervation (SAD) produces severe organ damage in rats. The present study was designed to investigate whether apoptosis, which is a ubiquitous physiological mode of cell death distinct from cell mortality induced by injury and necrosis, is involved in SAD-induced cardiac damage. 2. Male Sprague-Dawley rats (10 weeks old) were used. Rats underwent SAD (n = 9) or sham operation (n = 10). Sixteen weeks after operation, the heart tissues were taken for investigations including electron microscopy, immunohistochemistry, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labelling (TUNEL) and reverse transcription-polymerase chain reaction (RT-PCR). 3. Cardiac hypertrophy and fibrosis was found in SAD rats. The number apoptotic cardiomyocytes was increased in SAD rats compared with sham-operated rats. 4. The expression of Bcl-2mRNA and protein (an inhibitory factor of apoptosis) in cardiomyocytes was decreased in SAD rats. In contrast, the expression of Bax, Fas and Fas ligand mRNA and proteins (promoters of apoptosis) in cardiomyocytes was significantly increased in SAD rats. 5. In conclusion, the present study reveals a high level of apoptosis in cardiomyocytes in SAD rats. It is proposed that apoptosis is involved in SAD-induced cardiac damage.

Urinary outflow obstruction increases apoptosis and deregulates Bcl-2 and Bax expression in the fetal ovine bladder

During organogenesis, net growth of tissues is determined by a balance between proliferation, hypertrophy, and apoptotic death. Human fetal bladder outflow obstruction is a major cause of end-stage renal failure in children and is associated with complex pathology in the kidney and lower urinary tract. Experimental manipulation of the fetal sheep urinary tract has proved informative in understanding the pathobiology of congenital obstructive uropathy. In this study we used an ovine model of fetal bladder outflow obstruction to examine effects on apoptotic cell death in the developing urinary bladder. While 30 days of obstruction in utero between 75 and 105 days gestation resulted in overall growth of the fetal bladder as assessed by weight, protein, and DNA measurements, we found that apoptosis, as assessed by in situ end-labeling, was up-regulated in fetal bladder detrusor muscle and lamina propria cells and that this was accompanied by a down-regulation of the anti-death protein Bcl-2 and an up-regulation of the pro-death protein Bax. Moreover, activated caspase-3, an effector of apoptotic death, was increased in obstructed bladders. This is the first study to define altered death in an experimental fetal model of bladder dysmorphogenesis. We speculate that enhanced apoptosis in detrusor smooth muscle cells is part of a remodeling response during compensatory hyperplasia and hypertrophy. Conversely, in the lamina propria, an imbalance between death and proliferation leads to a relative depletion of cells.

Microvascular structural entropy: a novel approach to assess angiogenesis in pituitary tumors

Entropy, a measure of the degree of disorder in a system, has recently been used in different morphologic studies to quantify regularity. Our aims were (a) to study the structural organization of the microvascular bed in prolactin (PRL)-producing adenomas and carcinomas, the most vascularized of pituitary tumors, by assessing microvascular structural entropy (MSE), and (b) to determine whether the degree of disorder of the capillary bed correlates with tumor cell proliferation as estimated by MIB-1 labeling, microvessel density (MVD), the most widely used method of quantifying blood vessel formation, and various clinicopathologic parameters (gender, age, tumor size and invasiveness). The morphometric study demonstrated statistically significant differences in MIB-1 labeling, MVD, and MSE between PRL-producing adenomas and carcinomas. Unlike MIB-1 labeling index (PRL-producing adenomas 1.5 +/- 0.27; carcinomas 15.0 +/- 4.04) and MVD (PRL-producing adenomas 2.7 +/- 0.34; carcinomas 4.2 +/- 0.72), the MSE values were significantly higher in adenomas (171.5 +/- 25.37) than in carcinomas (67.9 +/- 17.45). These results indicate that PRL-producing carcinomas have a less chaotic distribution of vessels than benign adenomas. In contrast to a lack of correlation between microvessel density and other morphometric parameters, a strong negative correlation was found between MSE and MIB-1 labeling index (r = 0.511, p = 0.003). It thus appears that regular, less chaotic microvascular geometry contributes to increased proliferative activity in PRL cell tumors. Analysis of MSE may provide an independent parameter of tumor behavior, and contributes to a better understanding of the role of microvasculature in pituitary tumor progression.

Correlation of bcl-2 and bax with apoptosis in human pituitary adenomas

Bcl-2 oncogene and Bax gene play an important role in regulating apoptosis. In the present study, the expression of bcl-2 and bax was investigated and correlated with apoptosis in a series of 81 pituitary adenomas. Bcl-2 and bax proteins were localized by immunohistochemistry and the histoscore (HSC) was assessed by multiplying the immunohistostaining grade (1 to 4) by the staining intensity grade (1 to 3). According to bcl-2/bax HSC the tumors were separated in group A when > or = 1 and group B when < 1. The apoptotic labeling index (ALI) was accessed by the in situ end-labeling (ISEL) technique. Bcl-2 protein was equally detected in functioning and nonfunctioning adenomas with statistically significant higher HSC in nonfunctioning tumors (P < 0.03). Bax protein was immunopositive in the substantial majority of adenomas with significantly higher HSC in functioning as compared to nonfunctioning adenomas (P < 0.0009). The ALI was significantly higher in functioning adenomas as compared to nonfunctioning adenomas (P < 0.04). In addition, ALI was significantly higher in group B than in group A (P < 0.004) and it was correlated with bax HSC (P < 0.004). Finally, the group B of bcl-2/bax significantly predominated in nonfunctioning tumors (P < 0.0009) and in microadenomas (P = 0.05), as compared with functioning adenomas and macroadenomas respectively. In conclusion, our findings suggest that bcl-2 and bax molecules play a role in the regulation of apoptotic mechanisms in pituitary adenomas.

Effects of octreotide treatment on the proliferation and apoptotic index of GH-secreting pituitary adenomas

To investigate the effects of octreotide administration on the growth rate of GH-secreting pituitary adenomas, we measured both the Ki-67 labeling index (LI) and the apoptotic index in tumor specimens from octreotide-treated or matched untreated acromegalic patients. Thirty-nine patients who received octreotide until the day of or the day before surgery and 39 untreated patients matched for sex, age, tumor size, extension, and invasiveness were studied. Immunocytochemical analysis was performed on paraffin-embedded material using a monoclonal antibody (MIB-1) directed against a proliferation-associated nuclear antigen, Ki-67, to measure the growth fraction. Apoptosis was assessed by the terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick endlabeling method, using a monoclonal antibody recognizing areas of DNA fragmentation. The Ki-67 LI and apoptosis were counted on separate slides in at least 1000 evaluable cells. Octreotide-treated patients showed a lower Ki-67 LI (1.8 +/- 0.3%) than untreated controls (3.8 +/- 0.7%; P < 0.02). Overall, the mean Ki-67 LI of treated patients was 53% lower than that in untreated patients. The antiproliferative effect of octreotide occurred independently of tumor extension and invasiveness. Octreotide-treated and untreated patients showed similar apoptotic indexes (0.6 +/- 0.2% and 0.8 +/- 0.3%, respectively). There was a positive correlation between the Ki-67 LI and the apoptotic index (r = 0.29; P < 0.03). Our study demonstrates that acromegalic patients receiving chronic octreotide treatment have a lower value of the proliferation marker Ki-67, but no significant difference in the apoptotic index compared with matched untreated patients. The antiproliferative effect of octreotide on GH-secreting adenomas should imply a lower risk of tumor growth during long-term chronic treatment with the drug.

Genesis of pituitary adenomas: state of the art

In recent years, remarkable progress has been made in the understanding of the pathogenesis of pituitary tumors. Pituitary tumors originate from the uncontrolled proliferation of a single transformed cell in which an initiating event has caused a gain of proliferative function. After the initiation, promoting factors cooperate in the clonal expansion. Common oncogenes, such as ras, are only exceptionally involved. The only activating mutations identified so far are gsp mutations causing the constitutive activation of cAMP pathway. However, gsp-positive adenomas are not associated to a more aggressive tumoral phenotype. The oncogenic potential of gsp mutations is limited by a more rapid degradation of the mutant Gs(alpha) with respect to the wild-type protein, and by a faster removal of cAMP due to increased phosphodiesterase activity. Estrogen-inducible gene sequences with transforming properties (pituitary tumor-transforming gene (PTTG)) have been identified in human pituitary tumors. Human pituitary tumor-transforming gene (hPTTG) is involved both in early pituitary tumorigenesis, as it causes in vitro and in vivo transformation acting as a transcription activator, and in tumor progression, as it regulates the production of basic fibroblast growth factor (bFGF), a potent activator of angiogenesis and mitogenesis. Moreover, a role of cyclin D1 in pituitary tumorigenesis is emerging. The allelic loss of loci for unknown oncosuppressor genes are currently under investigation, while an exceedingly limited role for menin gene and RB1 has been demonstrated for sporadic pituitary tumors. Abnormal methylation that predisposing toward genetic instability may favor the allelic loss or the reduced expression of oncosuppressor genes, is also an emerging field of investigation. Several promoting factors, including the excessive action of physiological stimulators, the defective action of inhibitors, the susceptibility to respond to inappropriate stimuli and the locally produced growth factors, help in tumor progression. The study of homeobox genes that intervene in pituitary cell differentiation may help in expanding our knowledge in pituitary tumor cell genealogy.

Poorly differentiated synovial sarcoma: a case report

Poorly differentiated synovial sarcoma is a rare soft tissue tumor. We studied a case arising in the pleural cavity of a young subject, characterised by the presence of spindle cell, small cell, and large epithelioid cell areas. We performed stains for mucosubstances and analysed the expression of cytokeratins 5/6, 7, 8, 18, 19, CEA, CD34, Ber-Ep4 and calretinin to characterize the phenotype of this neoplasm. We furthermore assessed immunohistochemically the presence of p53, Bcl-2, Bax and caspase 3, four apoptotic markers, to evaluate a relationship between apoptotic activity and the behaviour of this tumor. Our findings showed a strong presence of calretinin, p53 and Bcl-2 in all three areas. The possibility that poorly differentiated synovial sarcoma could be calretinin-positive was a new data, to our knowledge, and it could be of some importance in diagnostic pathology. Moreover, the negligible positivity for Bax and caspase 3 suggested that the minor role of programmed cell death could be one of the causes of the aggressive behaviour of this tumor. These data also suggest that the reduction of apoptotic phenomena in poorly differentiated synovial sarcoma could be considered one of the major mechanisms of tumoral growth.

Leptin signal transduction in the HP75 human pituitary cell line

Leptin is an adipocyte-derived cytokine with many functions including signaling the status of body energy stores through activation of the leptin receptor (OBR). Activation of the long form of OB-R (OB-Rb) results in JAK2 phosphorylation, activation of STATs, and subsequent gene expression. Activated STAT3 induces SOCS-3 expression in some cell types, which in turn down-regulates the JAK/STAT pathway. Although both leptin and OB-R are expressed in pituitary cells, the mechanism of signal transduction and its regulation in this organ has not been studied extensively. In these experiments we show that leptin reduces proliferation in a human pituitary cell line (HP75) and also increased apoptosis in these cells. Leptin also increased SOCS-3 mRNA and protein expression and tyrosine-phosphorylation in the HP75 human pituitary cell line. These findings suggest that SOCS-3 plays an important role in the inhibition of proximal leptin signal transduction in the anterior pituitary.

Bcl-2 Gene Family in Endocrine Pathology: A Review

BcI-2 is a member of a large multigene family, which includes genes that can inhibit or promote apoptosis. The regulation of apoptosis is achieved by homo- or heterodimerization of their proteins through four highly conserved domains. Bcl-2 protein is a strong cell death suppressor in a wide range of cell types and under a variety of stimuli. Bcl-2 and the other members of this family are differentially expressed in the endocrine glands and disregulation of their expression seems to contribute to the neoplastic transformation in these organs. The significance of bcl-2 and the related proteins for endocrine pathology at the experimental and clinical level is reviewed in this article.

Effect of Dopamine Agonists on Lactotroph Adenomas of the Human Pituitary

Dopamine (DA) agonists cause reduction of blood prolactin level and tumor shrinkage in most patients with lactotroph adenoma. Our aim was to investigate the cellular mechanism of tumor shrinkage by determining mitotic, MIB-1, p27, and apoptotic indices, as well as microvessel density (MVD), surface microvessel density (SMD). ploidy, and other nuclear parameters. Surgically removed lactotroph adenomas were selected from 29 patients, of whom 19 were treated with oral bromocriptine (BEC), long-acting injectable BEC (BEC-LAR), or quinagolide and 10 were untreated. In treated adenomas mitotic and MIB-1 indices were lower, whereas the apoptotic indices were not significantly higher compared to untreated adenomas. The decrease in MIB-1 labeling reached significance in adenomas exposed to quinagolide (p<0.05). Aside from the BEC-LAR treated group, wherein p27 expression was significantly reduced (p<0.05), p27 expression did not differ significantly between the treated and untreated groups. MVD density was significantly lower in the treated adenomas, whereas the decrease in SMD did not attain significance. The DNA ploidy and most other nuclear parameters did not differ significantly in the two groups. In conclusion, reduction of mitotic and MIB-1 indices indicates that suppression of cell proliferation contributes to tumor shrinkage, whereas p27 protein expression and apoptosis play no major role in the adenoma involution. Further studies are required to explain the effect of DA agonists on MVD and SMD.