Blood serum concentrations of gonadotropins and α-subunit in patients with gonadotropinomas in relation to the immunoreactivity of pituitary adenoma.

INTRODUCTION: Although active gonadotropin-secreting pituitary adenomas are considered very rare, the vast majority of pituitary tumours diagnosed as "non-functioning" express gonadotropins or their free ß or α subunits. However, systemic investigations comparing the serum concentrations of follitropin (FSH), lutropin (LH), and α-subunit (αSU) before surgery with the immunoreactivity of the respective substances in the excised tumours are still lacking. MATERIAL AND METHODS: Immunostaining of FSH, LH, and αSU was compared in 43 surgically removed gonadotropin - expressing pitu-itary adenomas with serum concentrations of the above-mentioned substances before surgery in the same patients. RESULTS: The serum concentrations of FSH were elevated (> 11.6 mU/mL) in 8/12 (66.7%) cases of FSH-positive adenomas. By contrast, in FSH-negative tumours the elevation of FSH is absent. Moreover, only 1/25 (4%) patients with LH-positive adenoma had the elevated serum concentration of LH (51.5 mU/mL). The overproduction of LH was not observed in adenomas expressing free ß LH or in LH-negative tumours. In patients with αSU-positive adenomas elevated serum levels of αSU were observed in 3/15 (20%) cases. No αSU elevations were observed in patients with αSU-negative adenomas. The mean serum FSH, LH, and αSU concentrations were higher in patients with FSH, LH, and/or αSU immunopositive tumours in comparison with immunonegative. However, the differences are not statistically significant. CONCLUSIONS: Although "silent" gonadotropinomas constitute a frequent subtype of pituitary adenomas, the "active" subtype (i.e. manifesting by gonadotropin excess) are rare (approx. 4% of all pituitary adenomas). Gonadotropinomas are difficult to diagnose before surgery. The measurement of gonadotropins including αSU is needed but often not sufficient for presurgical diagnosis.

"Silent" thyrotropin (TSH) expression in acromegaly and clinically non-functioning pituitary adenomas.

INTRODUCTION: The pituitary adenomas secreting thyrotropin (TSH) are considered the rarest type of hormonally active pituitary tumour. In spite of that, many cases are described in the literature. On the other hand, the observations of the co-expression of TSH with other pituitary hormones (mostly with growth hormone [GH]) and "silent" expression of TSH in clinically non-functioning pituitary adenomas (CNFPA) are rather scarce. MATERIAL AND METHODS: Among 93 examined pituitary adenomas, 22 of them were diagnosed as active acromegaly and 71 as clinically non-functioning pituitary adenomas (CNFPA). All of them were immunostained with antibodies against pituitary hormones, including the anti-TSH antibody. TSH-immunopositive adenomas are immunostained also to detect somatostatin receptor subtypes (SSTR 1-5). RESULTS: TSH immunopositivity was found in 4.2% of CNFPA (3/71 tumours) and in 13.6% (3/22) cases of somatotropinomas manifesting as active acromegaly. All of the examined TSH-immunopositive adenomas expressed SSTR subtypes except SSTR4. The symptoms of hyperthyroidism were not observed in any of the acromegalic patients co-expressing TSH with GH. CONCLUSIONS: Our data confirm the relative rarity of TSH expression or co-expression of TSH in pituitary tumours. In most cases TSH is co-expressed with GH in patients with acromegaly and is not accompanied by hyperthyroidism. The "silent" expression of TSH may occur also, although rarely in CNFPA. The strong expression of SSTR in TSH-immunopositive CNFPA ("silent thyrotropinoma") indicates the possibility of the treatment of these tumours with somatostatin analogues. (Endokrynol Pol 2016; 67 (5): 515-518).

An evaluation of the effects of somatostatin analogue therapy in non-functioning pituitary adenomas in comparison to acromegaly.

INTRODUCTION: Non-functioning pituitary adenomas (NFPA) are often diagnosed late as invasive macroadenomas. The surgical resection is usually incomplete and about 50% of patients require additional surgery. Recent data suggest that somatostatin analogues (SSA), so important in the pharmacotherapy of acromegaly, can also be effective in the management of NFPA. MATERIAL AND METHODS: We analysed data of patients who had been treated up to 10 years previously with SSA: 40 with acromegaly (23 - primary, 17 - recurrent tumours) and 22 with NFPA (4 - primary, 18 - recurrent tumours). Hormonal profile, dynamics of tumour size change, ophthalmic syndromes, somatostatin receptor (SSTR) scintigraphy, and immunohistochemistry of SSTR subtypes of operated tumours as well as side effects were investigated. RESULTS: Biochemical cure of acromegaly was achieved in 57.5% of patients, while reduction of tumour size was observed in 37% of patients and it was more frequent in not-operated cases. Regarding NFPA, stabilisation of tumour size was noticed in 68% of patients. Tumour shrinkage was reported in 9% of cases, but in 23% of the study group the adenoma size increased with indication for reoperation. CONCLUSIONS: The efficacy of SSA in NFPA is much lower in comparison to their well-established effects in the treatment of acromegaly. Stabilisation of tumour size, which is observed in the majority of NFPA, is significantly more frequent in comparison to the natural history of untreated NFPA and our previous studies as well. Analysis of SSTR subtypes is an argument in favour of introduction of novel broad-spectrum SSA that may be more effective in the treatment of NFPA. Referring to acromegaly, adenoma size decrease was reported more frequently in primary therapy. Considering recurrent tumours better outcomes were achieved in patients who were pre-treated with SSA before planned surgery. (Endokrynol Pol 2016; 67 (3): 292-298).

Overexpression of prothymosin alpha is related to pituitary adenoma recurrence but not to adenoma invasiveness and proliferation.

INTRODUCTION: Prothymosin alpha (ProTα) is a peptide initially considered as a thymic hormone, but further studies have shown its wide distribution in different tissues and organs. It has a prevalent nuclear localisation and is thought to be involved in the control of proliferation and apoptosis. In earlier studies, the overexpression of ProTα was found in several human tumours, including pituitary adenomas. The present study deals with the relations of ProTα to the pituitary adenoma hormonal phenotype, proliferation, recurrence and invasiveness. MATERIAL AND METHODS: Sixty two pituitary adenomas were included in the study. The invasiveness of the tumours was estimated before surgery by means of magnetic resonance imaging. The paraffin sections of the tumours were immunostained with an antibody against the C-terminal fragment (101-109) of ProTα and with anti-Ki-67 antibody. The hormonal phenotype of the investigated pituitary adenomas had been established previously by means of immunostaining with antibodies to pituitary hormones (GH, PRL, FSH, LH, TSH, ACTH and α-subunit). RESULTS: Strong immunostaining with anti-ProTα antibody occurred in the subpopulation of cell nuclei and the walls of intratumoural blood vessels. ProTα index is higher in clinically non-functioning pituitary adenomas (CNFPA) compared to any type of functioning adenomas. There was no difference in the percentage of ProTα- positive cell nuclei in non-invasive vs. invasive adenomas, but it was significantly more frequent in recurrent than in primary tumours. Moreover, the decrease of ProTα index was found in somatotroph tumours treated with somatostatin analogues vs. untreated ones. The percentage of ProTα nuclei did not correlate with Ki-67 index. CONCLUSIONS: The overexpression of nuclear ProTα in pituitary adenomas is related to tumour recurrence, but not to proliferation or invasiveness.

Preoperative long-acting octreotide treatment for invasive thyrotropin-secreting pituitary macroadenoma after previous radioiodine thyroid ablation.

We report a 33-year-old woman with invasive thyrotropin-secreting pituitary adenoma after previous thyroid ablation with radioiodine who was successfully treated with transsphenoidal surgery after pre-treatment with octreotide-LAR for 10 months. Since invasive and aggressive thyrotropin-secreting macroadenomas are more frequently observed in patients who have undergone thyroid ablation, we suggest preoperative treatment with somatostatin analogs should be considered in these patients to reduce serum thyrotropin and stabilize or reduce tumor size.

Expression of follicle stimulating hormone receptors in pituitary adenomas - a marker of tumour aggressiveness?

INTRODUCTION: In our earlier study, we found that pituitary adenomas, like other human tumours, express ectopically follicle stimulating hormone receptors (FSHR) in intratumoural blood vessels endothelia and/or tumoural cells. The aim of the present paper was to provide more detailed data on FSHR expression in different subtypes of pituitary adenomas and to evaluate its possible role as a prognostic and/ or predictive biomarker in these tumours. MATERIAL AND METHODS: Forty two pituitary adenomas, surgically removed, were immunostained with antibodies against the pituitary hormones, antigen Ki-67 and 1-190 fragment of FSHR. RESULTS: The positive FSHR immunostaining was found in blood vessels endothelia of 88% of adenomas and in tumoural cells of 40% adenomas. In tumoural cells, the incidence of at least moderate FSHR immunostaining is significantly higher in invasive tumours (68%) compared to non-invasive (12%) ones, and higher (albeit not statistically significantly) in invasive-proliferating adenomas (Ki-67 > 3%, grade 2b) compared to invasive but non-proliferating (Ki-67 < 3%, grade 2a) ones. CONCLUSIONS: The present study confirms that pituitary adenomas ectopically express FSHR in intratumoural blood vessels endothelia and tumoural cells. Moreover, the expression in tumoural cells is prevalent in invasive and proliferating adenomas vs. non-invasive and non-proliferating tumours.

Angiotensins inhibit cell growth in GH3 lactosomatotroph pituitary tumor cell culture: a possible involvement of the p44/42 and p38 MAPK pathways.

The local renin-angiotensin system is present in the pituitary. We investigated the effects of angiotensins on GH3 lactosomatotroph cells proliferation in vitro and the involvement of p44/42 and p38 MAPK inhibitors in the growth-regulatory effects of angiotensins. Materials and Methods. Cell viability using the Mosmann method and proliferation by the measurement of BrdU incorporation during DNA synthesis were estimated. Results. Ang II and ang IV decreased the viability and proliferation of GH3 cells. Inhibitor of p44/42 MAPK attenuated the effects of ang II on cell viability and proliferation but did not affect the ang 5-8-dependent actions. Inhibitor of p38 MAPK prevented the decrease in the number of GH3 cells in ang-II- and ang-IV-treated groups. Conclusions. The growth-inhibitory effect of ang II is possibly mediated by the p44/42 MAPK. The p38 MAPK appears to mediate the inhibitory effects of both ang II and ang 5-8 upon cell survival.

The involvement of angiotensin type 1 and type 2 receptors in estrogen-induced cell proliferation and vascular endothelial growth factor expression in the rat anterior pituitary.

The aim of our study was to examine the involvement of renin-angiotensin system (RAS) in estrogen-induced lactotropes proliferation and vascular endothelial growth factor (VEGF) expression in rat pituitary. The study was performed on Fisher 344 rats underwent 8-day treatment with diethylstilboestrol (DES). The proliferation index (PCNA) and VEGF expression in pituitary sections were estimated using immunohistochemical methods. Treatment with DES increased the number of PCNA-positive cells, VEGF-positive cells, and VEGF-positive blood vessels in pituitary. Stimulatory effect of estrogen on cell proliferation and VEGF expression in blood vessels was attenuated by losartan, PD123319, and captopril. VEGF immunoreactivity in pituitary cells of DES-treated rats was decreased by AT1 antagonist and not changed by AT2 blocker and ACE inhibitor. Our findings suggest the involvement of RAS in DES-induced cell proliferation and VEGF expression in pituitary. Both the AT1 and AT2 receptors appear to mediate the estrogen-dependent mitogenic and proangiogenic effects in rat pituitary.

The effects of angiotensin peptides and angiotensin receptor antagonists on the cell growth and angiogenic activity of GH3 lactosomatotroph cells in vitro.

The local renin-angiotensin system (RAS) is present in the pituitary gland, and inhibitory effects of angiotensins on the lactosomatotroph (GH3) cell growth have been revealed. The aim of this study was to examine the influence of various angiotensin peptides and angiotensin AT1, AT2, and AT4 receptors antagonists on the cell proliferation, viability, and VEGF secretion in pituitary lactosomatotroph GH3 cell culture in order to identify receptors involved in antiproliferative effects of angiotensins on GH3 tumor cells. Cell viability and proliferation using Mosmann method and BrdU incorporation during DNA synthesis, and VEGF secretion using ELISA assay were estimated. The inhibitory effects of ang II, ang IV, and ang 5-8 on the cell viability and BrdU incorporation in GH3 culture were not abolished by AT1, AT2, and AT4 receptors antagonists. Ang II, as well as ang III and ang IV at lower concentrations stimulated the secretion of VEGF in GH3 cell culture. The secretion of VEGF was inhibited by ang III and ang IV at higher concentrations. AT1 and AT2 receptors antagonists prevented the proangiogenic effects of ang II. Ang II, ang IV, and ang 5-8 decrease the cell number and proliferation in GH3 cell culture independently of the AT1, AT2, and AT4 receptors. These peptides affect also secretion of VEGF in culture examined. Both the AT1 and AT2 receptors appear to mediate the proangiogenic effects of ang II.

Expression of somatostatin receptor subtypes in primary and recurrent gonadotropinomas: are somatostatin receptors involved in pituitary adenoma recurrence?

OBJECTIVE: Surgical treatment of pituitary macroadenomas often fails because of tumor recurrence after the operation. The causes of tumor recurrence are complex, but one of them may be the high growth potential of the adenoma. As somatostatin receptors mediate antiproliferative, anti-angiogenic and pro-apoptotic actions, it seemed reasonable to investigate their expression in dependence on the adenoma recurrence. METHODS: Samples of primary and recurrent gonadotropinomas excised surgically from patients were examined. This type of pituitary adenomas was chosen because of its relatively high recurrence rate. The adenoma phenotype and expression of somatostatin receptor subtypes 1-5 (SSTR 1-5) were investigated by immunohistochemistry, and the level of SSTR expression was semiquantitatively scored. RESULTS: It was found that the adenomas undergoing the early recurrence have lower expression of SSTR 2A and 3 in comparison to those which did not recur during 5 years lasting observation. On the other hand, the recurrent tumors show higher expression of SSTR 1, 2A, 3 and 5 subtypes than their primary counterparts. CONCLUSIONS: It is hypothesized that SSTR may, at least in part, counteract adenoma recurrence. On the other hand, it can be also presumed that the recurrent gonadotropinomas may be more sensitive to somatostatin analog treatment than primary ones. These hypotheses need to be confirmed in further studies.

SSTR1 and SSTR5 subtypes are the dominant forms of somatostatin receptor in neuroendocrine tumors.

The effectiveness of the long acting somatostatin analogues like octreotide and lanreotide depends on the expression of specific somatostatin receptors on the target cells. The immunohistochemical method performed on surgically removed tumors searches the expression of receptors at the level of receptor protein and gives us insight into receptor's cellular localization. The aim of study was to assess the presence of all the 5 subtypes of SSTR 1-5 (including 2A and 2B SSTR isoforms) in surgically treated human neuroendocrine tumors (NETs) to establish which receptor subtype is the dominant form of somatostatin receptor in particular tumor and thus to be able to predict which somatostatin analog will be effective in NETs treatment. 18 samples of neuroendocrine tumors (surgically excised tumors or biopsies) were immunostained with specific antibodies. Expression of SSTR was scored semiquantitatively. Only strong or moderate immunostaining was considered as positive reaction. The summarized expression pattern of SSTR in the investigated neuroendocrine tumors in our material was: SSTR 1> SSTR 5> SSTR 3> SSTR 2A> SSTR 2B. The receptors were distributed mainly in the area of cells cytoplasm with a few specimens showing only membranous or mixed: membranous--cytoplasmic localization. The observed pattern suggests that apart from octreotide and lanreotide, newly synthesized multiligand analogs such as SOM 230, KE 108 or SSTR 1 and SSTR 5 selective analogs could be effective in NETs treatment.

Does the response of GH-secreting pituitary adenomas to octreotide depend on the cellular localization of the somatostatin receptor subtypes SSTR2 and SSTR5?

INTRODUCTION: The immunohistochemical examination of somatostatin receptor (SSTR) subtypes expression in different endocrine tumours, including pituitary adenomas, revealed membranous or cytoplasmic distribution of SSTR1-5. Currently used long-acting somatostatin analogue octreotide prefers SSTR2 and SSTR5 subtypes. In an earlier study a positive correlation between the summarized score of SSTR2A + SSTR2B expressions and growth hormone (GH) response to octreotide administration was found, independently of receptor distribution within the cell. In this study we searched for the relationship between the GH inhibitory response to acute octreotide administration and SSTR2A, SSTR2B, and SSTR5 cellular localization. MATERIAL AND METHODS: Thirteen acromegalic patients underwent a test of acute administration of octreotide before surgery. The drop in GH was defined as the percentage of the basal value. The pituitary adenomas from these patients were immunostained to determine the hormonal phenotype and expression of SSTR subtypes. The subcellular distribution pattern of SSTR subtypes - membranous or cytoplasmic - was determined. RESULTS: In the majority of specimens, cytoplasmic localization of receptor subtypes was observed, although membrane or mixed cytoplasmicmembranous localized immunopositivity also occurred. The drop in GH after octreotide administration varied between 57.1-96.7% (mean 82.1%). Among the patients with the cytoplasmic localization of SSTR5, the decrease in GH was significantly higher (92.0 +/- 7.0%). A tendency towards the higher response in patients with cytoplasmic localization of SSTR2A and 2B was also observed (86.8% and 87.0%, respectively). CONCLUSIONS: It seems that cytoplasmic localization of SSTR5, SSTR2A, and SSTR2B is connected with enhanced GH inhibition after octreotide administration. It is possible that this somatostatin analogue alters the localization of subtypes SSTR2A and SSTR2B through the receptor internalization. As a consequence, the SSTR-immunopositivity in cell cytoplasm is increased. The cytoplasmic but not the membranous localization is connected with the higher responsiveness to the octreotide in somatotropinomas.

Plurihormonality of pituitary adenomas in light of immunohistochemical studies.

INTRODUCTION: Plurihormonality of pituitary adenomas can be defined as the ability of an adenoma to express more than one pituitary hormone. The application of immunohistochemistry to diagnose surgically removed pituitary tumours revealed that a great number of pituitary adenomas are in fact plurihormonal. However, data on the incidence and the clinical relevance of the pituitary adenoma plurihormonality are still scarce and controversial. MATERIAL AND METHODS: Hundred fifty-five pituitary adenomas, surgically removed, were studied immunohistochemically with the antibodies against pituitary hormones or their subunits. Additionally, 40 adenomas were immunostained with Ki-67 antibody to evaluate the proliferative potential. RESULTS: According to the World Health Organization (WHO) recommendations, we did not consider tumours expressing both FSH and LH (gonadotropinomas) or somatoprolactinomas expressing both GH and prolactin as plurihormonal. Even with this limitation, plurihormonality was found to be a frequent finding in both hormonally active and clinically non-functioning pituitary adenomas. It was shown that over one-third (36.1%) of the investigated adenomas expressed more than one hormone. Plurihormonality, especially that which is connected with co-expression of ACTH, seems to be more frequent in the recurrent tumours. Plurihormonal adenomas also possess higher Ki-67 indices, as compared to monohormonal tumours. CONCLUSIONS: Plurihormonality is a frequent phenomenon in both hormonally active and clinically non-functioning pituitary adenomas. It also seems to predict a higher risk of tumour recurrence. (Pol J Endocrinol 2010; 61 (1): 63-66).

Expression of somatostatin receptor subtypes in human pituitary adenomas -- immunohistochemical studies.

BACKGROUND: The highly variable expression of SSTR subtypes in pituitary adenomas (PA) may partially explain why the subgroup of somatotropinomas or other adenomas do not respond to the therapeutic action of currently used long-acting somatostatin analogues like octreotide or lanreotide. MATERIAL AND METHODS: Our study summarizes the data on expression of all somatostatin receptor subtypes (SSTR 1-5), extended for 2A and 2B SSTR isoforms, revealed by means of immunohistochemistry in dependence to different hormonal phenotype of the tumour. RESULTS: The pattern of SSTR immunostaining (estimated according to the percentage frequency of appearance) was in acromegaly: SSTR 5 > SSTR 1 > SSTR 2A = SSTR 3 > SSTR 2B, in prolactinomas: SSTR 2B = SSTR 3 = SSTR 5 > SSTR 1 = SSTR 2A, in gonadotropinomas: SSTR 3 > SSTR 2B > SSTR 1 = SSTR 2A > SSTR 5, in corticotropinomas: SSTR 2A > SSTR 1 = SSTR 3 > SSTR 5 > SSTR 2B. In PA immunonegative for pituitary hormones, we noticed only a weak staining of all receptor subtypes including SSTR 4. In plurihormonal adenomas with positive GH phenotype the staining pattern was: SSTR 5 > SSTR 1 = SSTR 2B and in plurihormonal PA with negative GH phenotype: SSTR 1 = SSTR 5 > SSTR 2A = SSTR 2B = SSTR 3. In plurihormonal adenoma with ACTH immunopositivity, the staining pattern was: SSTR = SSTR 2A = SSTR 3 = SSTR 5. SSTR 1 and SSTR 5 were the most frequent subtypes of somatostatin receptor in plurihormonal adenomas without ACTH expression. CONCLUSIONS: Human PA represents a group of tumours with a much more differentiated appearance of somatostatin receptor subtypes. It is very important to determine the SSTR profile individually for each tumour to make an appropriate decision as to therapeutic strategy choice. Apart from applying SSTR 2 and SSTR 5-preferring octreotide and lanreotide - newly synthesized multiligand analogues, such as SOM 230, KE 108, or other SST selective analogues, may represent a further useful approach for the treatment, especially in cases other than somatotropinoma or thyrotropinoma.

Effects of rosiglitazone--peroxisome proliferators-activated receptor gamma (PPARgamma) agonist on cell viability of human pituitary adenomas in vitro.

OBJECTIVES: Rosiglitazone (RGZ) belongs to thiazolidinediones - new class of antidiabetic drugs which are PPARgamma agonists. It was shown that tumoral tissue, including the pituitary adenomas, posses PPARgamma receptors. The activation of PPARgamma receptors inhibits tumour growth in rodents and induces the oncostatic effect on human cancer cell lines. The aim of the present study was to examine the anti-tumour effect of RGZ on human pituitary adenomas in vitro. MATERIALS AND METHODS: Cells of eight pituitary adenomas removed neurosurgically were used to our experiment. Before the operation, the hormonal secretion of the tumour was estimated. After the surgery, the histological diagnosis and immunohistochemical detection of pituitary hormones and PPARgamma receptors were performed. The cells of pituitary tumours were exposed in the primary culture to RGZ at the concentrations of 10(-9)-10(-4) M for 24 hours. To measure the cell growth the modified colorimetric Mossman method detecting the cells viability was applied. RESULTS: On the basis of the pre-operative diagnosis the 6 clinically non-functioning adenomas (CNFPA), one case of acromegaly and one case of Cushing's disease were recognized. In 5 out of 6 CNFPA the immunopositive reaction for different pituitary hormones such as: LH, HGH, PRL, FSH and alpha-subunit was detected. Expression of PPARgamma was found in all examined tumours. Rosiglitazone decreased the cell viability of all CNFPA and corticotropinoma for 20% or more. In somatotropinoma inhibition of the cell growth was about 13%. There is no correlation between PPARgamma expression and efficacy of rosiglitazone. THE MAIN FINDING: The obtained results indicate that RZG exerts a suppressive effect on the cell viability in non-functioning pituitary adenomas. The lack of correlation between PPARgamma expression and anti-tumoral effect of RZG suggests that the above-mentioned action of this compound is independent on PPARgamma expression. CONCLUSION: Our data suggest that rosiglitazone may be useful in the treatment of non-functioning pituitary adenomas, but its efficacy in Cushing's disease and acromegaly requires further study.

Somatostatin receptors in GH-secreting pituitary adenomas--their relationship to the response to octreotide.

Twenty pituitary adenomas, surgically removed from patients suffering from acromegaly, were studied. The tumours were immunostained with anti-GH and anti-PRL antibodies and with antibodies raised against particular subtypes of somatostatin receptors (rsst1-5). Expression of rsst immunoreactivity was scored using the following scale: 0--negative reaction, 1--weak reaction, 2--moderate reaction, 3--strong reaction. In 15 patients in whom the GH response to the acute administration of 200 ug octreotide was tested the correlation between the expression of rsst and the percentage of GH drop was estimated. All the tumours were GH-immunopositive and in the majority (14/20) co-expression of PRL was also found. All the adenomas examined expressed rsst2A (20/20) and rsst5 (12/12) receptor proteins. Receptors sst2B and rsst3 were found in all but one of the tumours examined (19/20 and 11/12, respectively). None of tumours investigated presented rsst4 immunopositivity. The mixed (GH/PRL) adenomas showed a tendency to a higher expression of rsst2A + + rsst2B and a greater response to octreotide administration. A significant positive correlation was found between rsst2A + rsst2B expressions and a drop in GH after octreotide. To conclude, the GH-inhibiting effect of octreotide depends on the intensity of expression of both rsst2A and rsst2B. Both isoforms of rsst2 mediate the same biological response (inhibition of GH secretion) in GH-secreting and GH/PRL-secreting adenomas.

"Silent"corticotropinoma.

OBJECTIVES: The aim of the study was to evaluate the ACTH-immunopositive pituitary adenomas, especially those without manifestation of Cushing's disease MATERIAL AND METHODS: 148 pituitary adenomas removed surgically in years 1994--2007 were studied. The paraffin sections were immunostained with antibodies against the pituitary hormones. In 79 adenomas the immunostaining with anti-ACTH antibody was performed Additionally, 23 tumors were also immunostained with anti-Ki-67 (MIB-1) antibody. Visualization of reactions was done by means of streptavidin-biotin-peroxidase technique with use of 3,3'-diaminobenzidine as chromogen. RESULTS: ACTH immunopositivity was found in 34 cases (23%). Fourteen ACTH-immunopositive tumors manifested themselves as Cushing's disease (including 1 case of Nelson's syndrome). In the remaining 20 cases in spite of the positive immunostaining for ACTH of the tumor cells, no features of hypercortisolism were observed (in several cases even hypocortisolism was found). Thus, those tumors represented so-called "silent" corticotropinomas. Over one third (37%) of "clinically" nonfunctioning pituitary adenomas, when immunostained with anti-ACTH antibody, showed ACTH immunopositivity. Three adenomas in patients with Cushing's disease (21.4%) and 7 "silent" corticotropinomas (35%) were recurrent tumors. In contrast, the recurrence rate in the group of ACTH-immunonegative clinically nonfunctioning pituitary adenomas was 14.7%. The "silent" corticotropinomas exhibited a tendency towards the higher expression of a proliferation marker, Ki-67 antigen as compared to the "active" corticotropinomas. CONCLUSIONS: (i) "Silent" corticotropinomas are rather frequent. (ii) This adenoma type should be considered as aggressive. (iii) It is hypothetized that--like in Nelson's syndrome--the lack of hypercortisolism or even presence of hypocortisolism favorizes the exaggerated growth of tumoral corticotrophs.

Effects of somatostatin on vascular endothelial growth factor (VEGF) secretion from non-functioning pituitary tumoral cells incubated in vitro.

OBJECTIVES: The aim of the study was to examine the effect of somatostatin (SST) on vascular endothelial growth factor (VEGF) secretion from clinically non-functioning pituitary tumors incubated in vitro. MATERIAL AND METHODS: Eight pituitary tumors surgically removed were investigated. All of the tumors were diagnosed before surgery as non-functioning. Seven of them were diagnosed after surgery as pituitary adenomas and expressed either gonadotropins or their subunits as detected by immunohistochemistry. Two tumors additionally expressed prolactin and growth hormone. One tumor was immunonegative for pituitary hormones and was diagnosed as haemangiopericytoma. All tumors but one were investigated immunohistochemically to detect the somatostatin receptors and expressed at least 3 of 5 subtypes of somatostatin receptors. The cells isolated from the examined tumors were exposed in vitro to native SST-14. The concentration of VEGF in the culture media was performed by means of ELISA method. RESULTS: It was found that the exposure on SST-14 resulted in the divergent changes (increase in 4 cases and decrease in 3 cases) in VEGF concentrations in the medium. It seems that the inhibition of VEGF secretion is related to the expression of somatostatin receptor subtypes sst1 and sst2. CONCLUSIONS: The response of VEGF secretion from pituitary tumoral cells to SST seems to depend on the spectrum of expressed somatostatin receptor subtypes. However, this presumption needs further studies on the larger material.

Angiotensin peptides regulate angiogenic activity in rat anterior pituitary tumour cell cultures.

INTRODUCTION: Angiogenesis has been shown to be necessary for the development and progression of solid tumours. VEGF is one of the crucial pro-angiogenic cytokines produced by the cells of many of the tumours examined, including various types of anterior pituitary adenomas. Angiotensin II (Ang II) is known to regulate the expression of VEGF in a variety of tissues both in the physiological and pathological conditions. Moreover, an association of the renin-angiotensin system (RAS) with oestrogen-induced vascular changes during the development of rat pituitary PRL-secreting adenoma has already been demonstrated. The aim of the study was to determine the in vitro effects of angiotensin peptides (Ang II, Ang III and Ang IV) on the secretion of VEGF in two anterior pituitary adenoma cell cultures: the culture of the rat pituitary lactosomatotrope tumour cell line (GH3) and the primary culture of rat PRL-secreting tumour induced by diethylstilbestrol (DES). MATERIAL AND METHODS: GH3 and prolactinoma cells were cultured in an F10 and an F-12 medium respectively and then placed into 24 multiwell plates (10(5) of GH3 cells/well and 10(6) of rat prolactinoma cells/well). After 12 hours of preincubation the cells underwent 24-hour treatment with Ang II, Ang III or Ang IV at final concentrations of 10(-12), 10(-10), 10(-8) or 10(-6)M and, in the case of the GH3 cells, combined treatment with Ang II (10(-10)M) and specific AT1 or AT2 receptor antagonist (losartan or PD123319 respectively at a concentration of 10(-8) or 10(-7) M). The concentration of VEGF in the supernatant collected was determined using specific ELISA assay kits. Statistical evaluation was performed using Student's test and analysis of variance (ANOVA). Differences were considered significant if p < 0.05. RESULTS: The incubation of both GH3 cells and rat adenoma cells with Ang II, Ang III or Ang IV at concentrations of 10(-12) -10(-8)M resulted in a significant increase in VEGF concentration in the culture medium. Exposure of GH3 cells to Ang III or Ang IV at concentrations of 10(-6)M led to a significant inhibition of cytokine release, and Pearson's correlation curve showed a tendency for Ang II at concentrations of more than 10(-6)M to inhibit VEGF secretion in primary prolactinoma cell culture. The stimulatory influence of Ang II on VEGF secretion in GH3 cell culture was negated by losartan or by PD123319 in both concentrations tested. CONCLUSIONS: Ang II, Ang III and Ang IV affect the secretion of VEGF in cultures of the rat lactosomatotrope GH3 cell line and primary rat prolactinoma cells. Both AT1 and AT2 receptors mediate the stimulatory action of Ang II on the cytokine release in GH3 cell culture. The mechanism of the observed anti-angiogenic effects of angiotensin peptides remains unexplained.