Role of Ki-67 in acromegalic patients with hyperprolactinemia: retrospective analysis in 61 Chinese Patients

To evaluate the specific characteristics in acromegalic patients with hyperprolactinemia by analyzing the differences between patients with different Ki-67 values. Between 2002 and 2010, a set of data on 61 patients undergoing transsphenoidal surgery was available at the Department of Neurosurgery, Provincial Hospital Affiliated to Shandong University. Patients were divided into Ki-67 >3% group and <3% group. A retrospective analysis of clinical, hormonal, immunohistochemical, and imaging was observed in all patients. There were no significant differences in age, gender, tumor size and apoplexy between the two groups. Time interval in Ki-67 ≥3% group was longer than <3% group (P=0.037). Patients in Ki-67 >3% group had a higher rate of invasiveness (P=0.048), higher incidences of diabetes mellitus (P=0.036), coarse facial features (P=0.048), large hands and feet (P=0.003), higher GH levels (P<0.05), higher diabetes insipidus rate (P<0.001), and more frequent recurrence (P=0.011) than Ki-67 <3% group. Patients with higher Ki-67 value harbored longer time interval, more aggressive tumors, more acromegaly manifestations, higher GH level, and higher recurrence than patients with lower Ki-67 value.

Prolactinoma with extensive amyloid deposits: a case report

Prolactinomas are common benign pituitary neoplasms. Amyloid deposits are rare findings that have been reported in pituitary neoplasms. We report a case of a 48-year old man with a diagnosis of prolactinoma with extensive amyloid deposition. To our knowledge, this is the first case of amyloid in a pituitary neoplasm at our institution.

Molecular pathogenesis of human prolactinomas identified by gene expression profiling, RT-qPCR, and proteomic analyses

The molecular pathogenesis of prolactinomas has resisted elucidation; with the exception of a RAS mutation in a single aggressive prolactinoma, no mutational changes have been identified. In prolactinomas, a further obstacle has been the paucity of surgical specimens suitable for molecular analysis since prolactionomas are infrequently removed due to the availability and effectiveness of medical therapy. In the absence of mutational events, gene expression changes have been sought and detected. Using high-throughput analysis from a large bank of human pituitary adenomas, we examined these tumors according to their molecular profiles rather than traditional immunohistochemistry. We examined six prolactinomas and eight normal pituitary glands using oligonucleotide GeneChip microarrays, reverse transcription-real time quantitative polymerase chain reaction using 10 prolactinomas, and proteomic analysis to examine protein expression in four prolactinomas. Microarray analyses identified 726 unique genes that were statistically significantly different between prolactinomas and normal glands, whereas proteomic analysis identified four differently up-regulated and 19 down-regulated proteins. Several components of the Notch pathway were altered in prolactinomas, and there was an increased expression of the Pit-1 transcription factor, and the survival factor BAG1 but decreased E-cadherin and N-cadherin expression. Taken together, expression profiling and proteomic analyses have identified molecular features unique to prolactinomas that may contribute to their pathogenesis. In the current era of molecular medicine, these findings greatly enhance our understanding and supercede immunohistochemical diagnosis.

A mutation and expression analysis of the oncogene BRAF in pituitary adenomas

OBJECTIVE

BRAF is an oncogene that is commonly mutated in both melanomas and papillary thyroid carcinomas, usually at position V600E that leads to constitutive activity in the Ras-mitogen-activated protein kinase (MAPK) pathway. We speculated that this same gene may be either mutated at this site, or overexpressed, in pituitary adenomas.

DESIGN AND MEASUREMENTS

We sequenced 37 pituitary adenomas for a mutation at the V600E position. In addition, we investigated B-Raf mRNA expression in normal pituitary (n = 5) and nonfunctioning pituitary adenomas (NFPA) (n = 6) by semiquantitative PCR, and in a further 27 pituitary adenomas of various types and 10 normal pituitaries using real-time quantitative PCR. Finally, we explored B-Raf protein expression in 10 normal pituitaries and 12 NFPAs.

RESULTS

No sequence mutations for the substitution V600E were identified. B-Raf mRNA was overexpressed in pituitary adenomas compared to normal pituitary, and this was entirely due to overexpression in NFPAs. NFPAs also showed very variable expression of B-Raf protein, but those tumours showing highest levels of B-Raf mRNA expressed the most B-Raf protein.

CONCLUSIONS

Mutations previously seen in the majority of melanomas and a substantial minority of papillary thyroid carcinomas are not a frequent finding in pituitary adenomas. However, overexpression of B-Raf mRNA and protein may be a feature of NFPAs, highlighting overactivity of the Ras-B-Raf-MAP kinase pathway in these tumours.

Do the limits of serum prolactin in disconnection hyperprolactinaemia need re-definition? A study of 226 patients with histologically verified non-functioning pituitary macroadenoma

BACKGROUND

The differentiation of a pituitary non-functioning macroadenoma from a macroprolactinoma is important for planning appropriate therapy. Serum PRL levels have been suggested as a useful diagnostic indicator. However, values between 2500 and 8000 mU/l are a grey area and are currently associated with diagnostic uncertainty.

OBJECTIVE

We wished therefore, to investigate the serum PRL values in a large series of patients presenting with apparently non-functioning pituitary macroadenomas.

PATIENTS AND METHODS

All patients presenting to the Department of Endocrinology in Oxford with clinically non-functioning pituitary macroadenomas (later histologically verified) between 1990 and 2005 were studied. Information documented in the notes on the medications and on the presence of conditions capable of affecting the serum PRL levels at the time of blood sampling was also collected.

RESULTS

Two hundred and twenty-six patients were identified (median age at diagnosis 55 years, range 18-88 years; 146 males/80 females; 143 gonadotroph, 46 null cell, 25 plurihormonal and 12 silent ACTH adenomas). All tumours had suprasellar extension. At the time of blood sampling 41 subjects were taking medications capable of increasing serum PRL. Hyperprolactinaemia was found in 38.5% (87/226) of the patients. The median serum PRL values in the total group were 386 mU/l (range 16-3257) (males: median 299 mU/l, range 16-1560; females: median 572 mU/l, range 20-3257) and in those not taking drugs capable of increasing serum PRL 363 mU/l (range 16-2565) (males: median 299 mU/l, range 16-1560; females: median 572 mU/l, range 20-2565). Serum PRL < 2000 mU/l was found in 98.7% (223/226) of the total group and in 99.5% (184/185) of those not taking drugs. Among the three subjects with serum PRL > 2000 mU/l, two were taking oestrogen preparations.

CONCLUSIONS

Based on a large series of histologically confirmed cases, serum PRL > 2000 mU/l is almost never encountered in nonfunctioning pituitary macroadenomas. Values above this limit in the presence of a macroadenoma should not be surrounded by diagnostic uncertainty (after acromegaly or Cushing's disease have been excluded); a prolactinoma is the most likely diagnosis and a dopamine agonist should be considered as the treatment of choice.

Mapping of somatostatin receptor types in GH or/and PRL producing pituitary adenomas

BACKGROUND

Somatostatin is a tetradecapeptide exerting inhibitory action on endocrine and exocrine cell secretion and proliferation. Somatostatin receptors (SST) are widely expressed in various neoplasms including endocrine tumours. Using immunohistochemistry, the expression of SST(1), SST(2A), SST(2B), SST(3), SST(4), and SST(5) was studied in tissue microarrays (TMAs), using a series of 90 human pituitary adenomas producing growth hormone and/or prolactin, including 30 of each somatotroph, lactotroph, and mixed somatotroph/lactotroph adenoma type.

METHODS

For immunohistochemistry, the standard avidin biotin complex method enhanced by tyramide was used, using polyclonal antisera for all SST types. A four point scoring system was used to assess the membranous immunopositivity.

RESULTS

All SST types were positive in all tumour types, showing varying immunoreactivity scores. SST(5) and SST(2A) were the predominant receptors, showing strong expression in high frequency in all three adenoma types. Strong expression of SST(1) was higher in lactotroph adenomas than in other tumour types.

CONCLUSIONS

The immunohistochemical results of SST expression are in agreement with most findings of previous molecular studies. The fact that SST(2A) expression is predominant suggests that pharmaceutical octapeptide somatostatin analogues may act through this receptor, while the role of SST(2B) may be merely synergistic.

Mechanism of adrenomedullin-induced prolactin release from human prolactin-releasing adenoma cells

The mechanism of adrenomedullin-induced prolactin release was investigated in prolactin-secreting human pituitary adenoma cells by intracellular calcium measurement and static incubation study. Adrenomedullin stimulated prolactin release in a concentration-dependent manner. The stimulation was dependent on extracellular sodium and voltage-gated calcium channels. PKA inhibitor attenuated adrenomedullin-induced prolactin release. The mechanism of adrenomedullin action was studied by fura 2-based intracellular calcium measurement. Adrenomedullin increased intracellular calcium concentration in these cells. The increase was dependent on extracellular sodium and voltage-gated calcium channels. PKA inhibitor attenuated the calcium response. These data indicate that adrenomedullin stimulates prolactin release by modulating calcium influx through voltage-gated calcium channels dependently on extracellular sodium. Mechanisms involving sodium-influx mediated depolarization may play a role in the stimulatory action.

Pharmacologic resistance in prolactinoma patients

Pharmacologic resistance to dopamine agonists is defined here as failure to normalize PRL levels and failure to decrease macroprolactinoma size by >or=50%. Failure to normalize PRL levels is found in about one-quarter of patients treated with bromocriptine and 10-15% of those treated with pergolide or cabergoline. Failure to achieve at least a 50% reduction in tumor size occurs in about one-third of those treated with bromocriptine and 10-15% of those treated with pergolide or cabergoline. The cause of dopamine resistance is primarily a decrease in D(2) receptors but the receptors have normal affinity for dopamine. Treatment approaches for patients resistant to dopamine agonists include changing to another dopamine agonist and increasing the dose of the drug as long as there is continued response to the dose increases and no adverse effects with higher doses. Transsphenoidal surgery is also an option. Clomiphene, gonadotropins, and GnRH can be used if fertility is desired. For those not desiring fertility, estrogen replacement may be used unless there is a macroadenoma, in which case control of tumor growth is also an issue and dopamine agonists are generally necessary. In many patients modest or even no reduction in tumor size may be acceptable as long as there is not tumor growth. Hormone replacement (estrogen or testosterone) may cause a decrease in efficacy of the dopamine agonist so that it must be carried out cautiously. Reduction of endogenous estrogen, use of selective estrogen receptor modulators, and aromatase inhibitors are potential experimental approaches.

Squash smear findings of spherical amyloid in pituitary prolactinoma. A case report

BACKGROUND

Pituitary prolactinoma containing spherical amyloid is rare. Squash smear findings of spherical amyloid in pituitary prolactinoma are characteristic.

CASE

A 25-year-old woman presented with a pituitary tumor. The intraoperative squash smear showed abundant, homogeneous, eosinophilic material with multiple prominent striations. The scattered atypical cells in the periphery contained an irregular, bizarre nucleus; coarse chromatin; occasional prominent nucleoli; rare cytoplasm; and prolactin immunoreactivity.

CONCLUSION

The characteristic squash smear findings should be helpful in the diagnosis of this rare tumor.

Reduced expression of the growth hormone and type 1 insulin-like growth factor receptors in human somatotroph tumours and an analysis of possible mutations of the growth hormone receptor

OBJECTIVE

Clinical acromegaly is characterized by elevated GH secretion in the presence of high circulating IGF-I levels. We hypothesized that the physiological IGF-I/GH negative feedback loop may be reset in somatotroph adenomas, specifically in terms of the level of expression of these receptors or mutations of the GH receptor (GH-R) in such tumours.

METHODS

We therefore investigated the full coding sequence of the GH-R in a series of somatotroph and other pituitary adenomas. We also investigated the mRNA expression of these putative feedback receptors in a series of pituitary adenomas and normal pituitary tissue, and their protein expression by immunostaining. Real-time RT-PCR assay was used for the quantification of the type 1 IGF receptor (IGF-R) and GH receptor (GH-R) mRNA, and sequence analysis was performed on the coding region of the GH-R gene.

RESULTS

No somatic mutations of the GH-R mRNA were detected in 18 GH-secreting tumours or two nonfunctioning pituitary adenomas (NFPAs). However, the levels of GH-R mRNA were significantly lower in both somatotroph tumours and NFPAs compared to the normal pituitary (P < 0.05 for both). Immunostaining for GH-R also showed significantly less GH-R expression in somatotroph adenomas compared to normal pituitary tissue (P < 0.0001). IGF-R mRNA levels were significantly lower in somatotroph tumours compared to normal pituitary (P = 0.005), and trended lower in corticotroph tumours (P = 0.07), while the other tumour types showed no significant difference from normal pituitary. Immunostaining for IGF-R also showed less IGF-R protein in the somatotroph adenomas compared to the normal pituitary tissue (P < 0.01).

CONCLUSIONS

Our findings suggest that decreased feedback inhibition of GH because of somatic mutations of the coding region of the GH-R are unlikely to be a common factor in the pathogenesis of these tumours. Nevertheless, decreased expression of the GH-R and of IGF-R in somatotroph tumours (both at the mRNA and protein level) may, at least in part, help explain the continuous secretion of GH from the tumour despite the high circulating levels of IGF-I and GH.

Clinicopathologic study of 123 cases of prolactin-secreting pituitary adenomas with special reference to multihormone production and clonality of the adenomas

BACKGROUND

Prolactinoma is the most invasive type of pituitary adenoma and is generally believed to be well-differentiated adenoma and to produce only prolactin (PRL). The factors related to the various biologic behaviors occurring in patients of different ages and sexes await clarification. Since different immunophenotypes of adenoma may show different biologic behaviors and responses to medical agents, the authors examined hormone production and tried to clarify the clonality of plurihormonal prolactinoma.

METHODS

Clinicopathologic factors were studied in 123 patients with prolactinomas (40 males and 83 females). The specimens were fixed in either 10% neutral buffered formalin or 70% alcohol and used for light microscopy. Alcohol-fixed tissue was used to extract DNA from 26 samples obtained from female patients for human androgen receptor gene (HUMARA) assay.

RESULTS

Sixty one cases (50%) were pure prolactinoma and 62 cases (50%) were plurihormonal prolactinoma. Spearman rank correlation analysis revealed a significant relationship between age and serum PRL level (P = 0.0002), age and tumor volume (P < 0.0001), and tumor volume and serum PRL level (P < 0.0001). Multiple regression analysis showed a significant correlation only between tumor volume and serum PRL level. The Mann-Whitney U test revealed that prolactinomas associated with higher PRL levels, larger adenomas, and higher ages were significantly more invasive to the cavernous sinus and that male patients had significantly higher PRL levels and larger adenomas. The HUMARA assay disclosed that 11 of 13 plurihormonal prolactinomas (85%) were compatible with monoclonal origin.

CONCLUSIONS

The current results suggest that not only can various hormones other than PRL be secreted by prolactinoma, but also that most multihormone-producing prolactinomas are monoclonal in origin.

Double pituitary adenomas: a series of three patients

Multiple pituitary adenomas may occur in up to 1.6-3.3% of patients with Cushing's syndrome. We report three patients with double pituitary adenomas detected at surgery. Two patients had Cushing's disease, but trans-sphenoidal exploration revealed a small prolactinoma in each. One prolactinoma also contained small numbers of basophils. Re-operation in both patients because of persistent Cushing's syndrome showed an ACTH-secreting micro-adenoma. The third patient with acromegaly had two macro-adenomas discovered in different parts of the gland at surgery: one plurihormonal and one null cell tumour. Careful evaluation of pre-operative MRI may not always detect more than one pituitary adenoma.

The release of leptin and its effect on hormone release from human pituitary adenomas

BACKGROUND

Leptin is the protein product of the obese gene, known to play an important role in body energy balance. The leptin receptor exists in numerous isoforms, the long isoform being the major form involved in signal transduction. Leptin expression has recently been demonstrated in the human pituitary, both in normal tissue and in pituitary adenomas. The long isoform of the leptin receptor has also been shown to be present in pituitary adenomas; however, contrasting results have been obtained regarding its expression in the normal human pituitary.

AIM

The aim of this study was (i) to investigate the presence and pattern of distribution of leptin mRNA and the long isoform of its receptor mRNA in the normal pituitary and in different types of pituitary adenomas with RT-PCR; (ii) to study leptin secretion from human pituitary tumours in culture and (iii) to assess in vitro pituitary hormone release following stimulation with human leptin.

RESULTS

Leptin receptor long isoform expression was detected in 2/4 GH-secreting adenomas, 12/17 non-functioning adenomas, 5/9 ACTH-secreting adenomas, 1/2 prolactinomas, 2/2 FSH-secreting adenomas and 5/5 normal pituitaries. The receptor long isoform did not segregate with any particular tumour type, and varying levels of expression were detected between the tissues studied. Leptin mRNA was detected at a low level of expression in 2/7 GH-secreting adenomas, 9/14 non-functioning adenomas, 2/3 ACTH-secreting adenomas, 1/3 prolactinomas and 1/3 FSH-secreting adenomas. We were unable to detect leptin mRNA in any of the five normal pituitaries removed at autopsy; however, immunostaining of a non-tumorous pituitary adjacent to an adenoma removed at transsphenoidal surgery showed scattered leptin positive cells. Culture of pituitary adenomas showed that 16/47 released leptin into the incubation media. Leptin release did not correlate with tumour type or with any of the other pituitary hormones released. In vitro leptin stimulation of pituitary tumours caused stimulation of FSH and alpha-subunit secretion from a non-functioning adenoma and TSH secretion from a somatotroph adenoma.

CONCLUSION

We conclude that not only is leptin stored within the pituitary, but it may also be released from pituitary cells and modulate other pituitary hormone secretion. Pituitary leptin may therefore be a novel paracrine regulator of pituitary function.

Expression of somatostatin receptors on human pituitary adenomas in vivo and ex vivo

The distribution and biologic activity of somatostatin receptor subtypes (SSTR) in pituitary adenomas is not clarified, especially regarding clinically non-functioning adenomas (NFPA). We therefore characterized SSTR in human pituitary adenomas by combining molecular biology and in vivo scintigraphy. Co-expression of gonadotropin-releasing hormone receptor (GnRH-R) mRNA was also assessed to see whether this feature was associated with adenoma subtype and SSTR status. Pituitary tumor biopsies were obtained during transsphenoidal adenomectomy from 21 patients (11 NFPA, 7 acromegalics, 2 prolactinomas, 1 Cushing's disease). Expression of mRNA encoding the 5 known SSTR subtypes and the GnRH-R was determined by RT-PCR. Twelve patients also underwent a pre-operative somatostatin receptor scintigraphy. Most adenomas (no.=18) expressed mRNA for more than one SSTR. SSTR2 mRNA was expressed in 18 cases, whereas SSTR4 was absent in all but one. SSTR3 was frequently expressed in NFPAs. Somatostatin receptor scintigraphy was positive in most cases, and with a significantly higher uptake index in GH-producing adenomas all of which expressed SSTR2 mRNA. The uptake index appeared to be related to receptor density rather than tumor volume. Expression of GnRH-R mRNA was found in both NFPAs and GH-producing adenomas and was not significantly associated with a particular SSTR subtype population.

IN CONCLUSION

1) the distribution of SSTR is not significantly different between NFPA and GH-producing adenomas; and 2) somatostatin receptor scintigraphy reveals a higher uptake in GH-producing adenomas which is not significantly related to either SSTR distribution or tumor volume.

Comparative immunohistochemical analysis of estrogen receptor and chromogranin-A reactivity in plurihormonal human prolactinomas

The aim of the study was to compare the immunoreactivity of estrogen receptors (ER) and chromogranin-A (CHR-A) in human prolactinomas with verified plurihormonality. Eleven cases of prolactinomas, nine found in women aged from 15-32 and two found in two men both aged 54 years, were analyzed for possible colocalization of other hormones produced by adenohypophysis, i.e. growth hormone (GH), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH) and adrenocorticotropic hormone (ACTH). All evaluated cases of prolactinomas were clinically manifested by elevated values of prolactin (PRL) in patient serum, while the values of other assayed hormones were within the normal range. Although biopsy material is not routinely submitted to immunohistochemical analysis for plurihormonality, these eleven cases of operated prolactinomas were randomly examined to the presence of plurihormonality. In six cases of prolactin-producing adenomas, the coexistence of growth hormone was detected. Colocalization of follicle-stimulating hormone and weak expression of adrenocorticotropic hormone were found in two cases each. Thus, bihormonal activity (PRL + GH) was found in six, and trihormonal activity (PRL + GH + FSH and PRL/GH + ACTH) in three cases of prolactinoma. In addition, the presence of prolactin and growth hormone was demonstrated in morphologically different cells. Eight of these eleven pituitary adenomas were tested for estrogen receptors (ER), which play an important role as growth stimulating factors and secretory factors for prolactin-producing cells. We tried to determine if there was a difference in the intensity of expression of estrogen receptors and chromogranin-A between pure prolactinomas and mixed, plurihormonal prolactinomas. By use of monoclonal antibodies, chromogranin-A found to be reactive in seven of eleven prolactinomas, i.e. in plurihormonal prolactinomas. Estrogen receptors were markedly expressed in all the eight prolactinomas analyzed, which may prove significant in the treatment of these hypophyseal tumors.

Effect of vasoactive intestinal polypeptide (VIP) on growth hormone (GH) and prolactin (PRL) release and cell morphology in human pituitary adenoma cell cultures

Six GH adenomas and three prolactinomas were investigated by light- and electron-microscopic morphological and immunocytochemical methods and the effect of vasoactive intestinal polypeptide (VIP) on growth hormone (GH) and prolactin (PRL) secretion was tested in vitro. The tumour cells of the acromegalic patients revealed both GH and PRL immunoreactivity while prolactinomas showed only PRL activity. All the adenomas stained immunocytochemically also for VIP. By electron microscopy, the tumours included two densely and two sparsely granulated GH, two mixed GH/PRL, and three sparsely granulated PRL adenomas. The dissociated cells were explanted, and cultured in vitro. The cultures in micro test plates were treated with VIP at different concentrations between 10(-5)-10(-12) M. GH and PRL contents in the culture media were measured by radioimmunoassay. GH release was significantly stimulated by VIP in a dose-dependent manner over the whole concentration range, while VIP was effective on the PRL release only at 10(-6)-10(-7) M concentration. The cells of a mixed adenoma were grown in Petri dishes and used for ultrastructural and immunocytochemical studies. The cytoplasmic structure of the cells treated with VIP corresponded to that of active hormone-secreting cells with large ergastoplasmic fields and Golgi zones containing secretory granules. Massive exocytotic events were encountered mainly in the GH-type cells. GH and PRL double immunocytochemistry showed the predominance of GH cells, many of them containing low amounts of PRL as well. Cells predominantly containing PRL were spread among them, they also might contain GH as well. Some of the cells contained only a single immunoreactive hormone. The intensity of gold labelling of the secretory granules appeared higher in the VIP-treated cells than in the untreated control ones which showed a cytoplasmic structure characteristic of glandular cells with low secretory activity. As all the adenoma cells both contained and reacted to VIP, our results are in agreement with an autocrine or paracrine effect of this peptide. The fine structure of the cells in the cultures treated with VIP supply an additional argument to the assumption that VIP may serve as a growth factor for these cell types.

Immunohistochemical analysis of p27 (Kip1) in human pituitary glands and in various types of pituitary adenomas

p27 (Kip1) plays regulatory roles in the cell cycle by inhibiting the activity of cyclin dependent kinases (CDKs). This immunohistochemical study is aimed at elucidating the expression of p27 in human pituitary and in various types of pituitary adenomas in order to clarify its role in the regulation of proliferation. Sixteen normal pituitary glands and 179 human pituitary adenomas were used for immunohistochemical studies. The tissues were fixed in 10% formalin and embedded in paraffin. Indirect peroxidase method was performed after heat-induced antigen retrieval using a monoclonal antibody against p27 protein. p27 protein was expressed in the nuclei of all 16 normal human pituitary glands. p27 protein was also expressed in 128 of 179 cases of pituitary adenomas (71.5%). A marked decrease of p27 expression was noted in ACTH-secreting adenomas, 8/20 (40.0%), compared with other types of pituitary adenomas--GH-secreting adenomas, 35/46 (76.1%); PRL-secreting adenomas, 22/33 (66.7%); TSH-secreting adenomas, 8/11 (72.7%); and nonfunctioning adenomas, 55/69 (79.7%). These results suggest that p27 may play some role in the regulation of proliferation in all types of pituitary adenomas. The lower levels of p27 in ACTH-secreting adenoma is of particular interest with respect to the intermediate lobe-derived pituitary tumor developed in p27 knockout mice.

ACTH silent adenoma shrinking under cabergoline

OBJECTIVES

The authors present a case report that proposes the use of cabergoline treatment in silent ACTH adenoma, an unusual member of the heterogeneous group of the so-called clinically non-functioning pituitary adenomas.

DESIGN

Following the clinical and radiological improvement of a recurrent silent ACTH adenoma in a 77-year-old patient treated with cabergoline (0.5 mg every 2 days for 2 years), in vitro studies of the original tumor were performed.

METHODS

The original tumor from the patient was studied by in situ hybridization and dopamine D2 receptor autoradiography. It was compared with four macroprolactinomas and two macroadenomas from patients with Cushing's disease.

RESULTS

The D2 receptor mRNA signal of the reported case was intense and of the same order of magnitude as that observed in control prolactinomas. Dopamine D2 receptor autoradiography was twice that of control corticotroph adenomas and was close to that observed in prolactinomas.

CONCLUSIONS

This is the first description of an in vivo shrinkage of an ACTH silent adenoma under cabergoline. We demonstrate in vitro, the presence of D2 receptors in the primitive tumor in concentrations similar to those found in control prolactinomas. These results suggest that therapeutic trials with cabergoline might be undertaken in recurring cases of ACTH silent tumors and more generally, non-functioning pituitary adenomas.

Expression analysis of cyclins in pituitary adenomas and the normal pituitary gland

OBJECTIVES

The molecular events involved in pituitary tumour development are still poorly understood. The cyclins play an important role in the control of the cell cycle during cell proliferation and over-expression of the cyclins has been shown in many different tumour types. The aim of this study was to investigate whether, in comparison to the normal gland, ectopic expression of cyclins occurs in pituitary tumours, and whether differences in cyclin expression are seen with different pituitary tumour types or in association with different tumour behaviour. In contrast to work on cyclin D there are no published data on cyclin B, A and E in human pituitary tumours.

METHODS

Sixty-seven surgically removed pituitary tumours and 10 specimens of normal human anterior gland were studied using immunohistochemistry to detect the nuclear expression of cyclin A, B, D and E. The microvascular density (as a measure of angiogenesis), Ki-67 labelling index (to assess cell proliferation) and bcl-2 expression had previously been investigated in this cohort.

RESULTS

All tumours studied contained cells that immunostained positively for cyclin A, B, D and E. However the proportion of positive cells in each tumour type was different. In contrast, there were no cyclin D positive cells in the normal anterior pituitary gland studied, and labelling indices (LI) for cyclins A, B and E were significantly lower in the normal gland than in pituitary adenomas. The cyclin LIs for A, B, D and E were significantly higher in macroadenomas when compared to microadenomas. Non-functioning pituitary tumours (NFA) generally showed the highest cyclin LI. In particular, both recurrent and nonrecurrent NFA showed significantly higher cyclin D LI than other tumours. The ratio of cells expressing cyclin B compared to those expressing cyclin A was significantly higher in functionless tumours that regrew when compared to NFAs that did not (P<0.05). Cyclin D LI and the overall Ki-67 LI as a measure of cell proliferation were related (R2 = 11.4, P = 0.0033) and bcl-2 positive tumours had significantly higher cyclin D LI compared with bcl-2 negative tumours. There was a weak relationship between angiogenesis and the relative proportion of cells expressing D when compared to those in S phase (D/A ratio) (r2 = 10.5, P = 0.02).

CONCLUSIONS

We have demonstrated that ectopic expression of cyclin D and over-expression of cyclins A, B and E, regulating different stages of the cell cycle is common in pituitary adenomas. In addition, cyclin expression was related to size and to pituitary tumour regrowth. The differences between functionless tumours that regrow and those that do not, may be due to reduced bcl-2 expression, increased cell proliferation, more cells at the G2/M stage (B/A ratio) and reduced cell differentiation with more aggressive subsequent tumour behaviour. Cyclin D expression and cell proliferation were related indicating that the cells entering the cycle become 'committed' to cell cycle progression. There was no relative over-expression of individual cyclins, and therefore no evidence of relative increase in cell cycle phase, indicating that the increased cyclin expression is more likely to be due to constant mitogenic stimulation rather than cell cycle regulatory failure. Although nuclear cyclin expression is a good marker of tumour growth and aggressive behaviour, the growth signal that leads to cyclin expression remains to be identified.

Cyclin D and cyclin E expression in normal and adenomatous pituitary

OBJECTIVES

Cyclins play an important role in the regulation of cell progression through the cell cycle. Over-expression of the cyclins has been shown in many different tumour types. Pituitary adenomas are a common form of endocrine neoplasia in the human, but have been little studied in terms of the expression of the principal cyclins regulating checkpoint exit, cyclin D1 and cyclin E.

METHODS

We therefore investigated the expression of cyclin D1 and cyclin E in a range of benign and metastatic pituitary tumours. We studied a total of 95 pituitaries, including normal pituitary (n=20), Cushing's disease (n=19), somatotroph tumours (n=19), non-functioning adenomas (n=18), prolactinomas (n=7), aggressive tumours (n=9) and pituitary carcinoma (n=3). All tumours and normal tissue were immunostained for cyclin D1 and cyclin E using a standard technique, and were then subjected to blinded analysis by a single observer and the extent of staining quantified on the basis of 500 cell counts per tissue. The distribution of positive staining between different tissues was analysed by non-parametric test procedures.

RESULTS

There was no cytoplasmic staining for cyclin D1 in any tissue. Nuclear staining was generally sparse, but was statistically more frequent in non-functioning and aggressive tumours compared with other tumour types or normal pituitary. Cyclin E was also sparsely expressed, but was specifically increased in corticotroph tumours from patients with Cushing's disease.

CONCLUSIONS

We report cyclin D1 over-expression in aggressive and non-functioning pituitary tumours, and that cyclin E expression is more frequently seen in Cushing's disease. The high level of cyclin E expression in Cushing's disease may relate to the low level of p27 protein expression previously reported in corticotroph tumours.

Postoperative radiation therapy for pituitary adenoma

BACKGROUND

We evaluated the efficacy of postoperative radiation therapy (RT), prognostic factors for local control probability, dose response relationship and treatment sequelae in 75 patients with pituitary adenoma.

MATERIALS AND METHODS

A total dose of 48-60 Gy (median: 50 Gy) was delivered with a conventional fractionation schedule after surgery. Of 75 patients, 55 (73%) were followed for more than 5 years and 27 (36%) were followed for more than 10 years with a median of 95 months.

RESULTS

Five- and 10-year local control probabilities were 87.1% and 85.0%, respectively. Univariate analysis revealed that age (p = 0.007), tumor volume smaller than 30 cm3 (p = 0.018) and the absence of prolactin secretion (p = 0.003) were significantly favorable prognostic factors for local control probability. After multivariate analysis combining these 3 factors, tumor volume smaller than 30 cm3 (p = 0.017) and age (p = 0.039) were statistically significant. Patients with prolactinoma greater than 30 cm3 showed particularly poor local control rates. No significant improvement of the local control rate was detected with increasing total irradiation doses between 48 and 60 Gy (p = 0.29). The most common side effect was hypopituitarism, and there were no severe sequelae such as optic neuropathy or brain necrosis.

CONCLUSION

Except with prolactinoma, the dose of postoperative RT for pituitary adenoma should not exceed 50 Gy. Large prolactinoma, however, was very difficult to control with the irradiation doses between 50 and 60 Gy, and would be good candidates for stereotactic radiosurgery or stereotactic radiation therapy.

Expression of prolactin-releasing peptide and its receptor messenger ribonucleic acid in normal human pituitary and pituitary adenomas

The recently identified PRL-releasing peptide (PrRP) is the first hypothalamic peptide hormone that specifically stimulates PRL production from the pituitary gland. Similar to other hypothalamic regulatory hormones, it acts through its specific seven-transmembrane domain, G protein-coupled receptor. Using RT-PCR, we examined messenger ribonucleic acid (mRNA) expression of PrRP and its receptor in normal human pituitary tissue and in pituitary tumors. PrRP mRNA was expressed in all five normal pituitary glands examined. In contrast, PrRP mRNA was detected in only 5 of 11 of the human prolactinomas. All 5 prolactinomas expressing PrRP were responsive to dopamine agonist treatment, whereas PrRP-negative prolactinomas were non- or partially responsive. PrRP mRNA was also detected in 6 of 13 GH-secreting tumors and 5 of 10 clinically nonfunctioning tumors investigated. PrRP receptor mRNA was found in all the normal and neoplastic human pituitary samples studied. The production of PrRP and its receptor by normal and neoplastic pituitary tissue raises the question of whether it may regulate PRL production in an autocrine/paracrine manner in pituitary tissue. Further investigation of PrRP and its receptor expression and function will be needed to clarify its potential role in regulating PRL secretion in normal human lactotrophs and pituitary tumors.

Bioactivity and glycosylation of circulating prolactin in various physiological and pathological conditions

Multiple posttranslational processes modify native PRL and result in the secretion of several PRL isoforms with different bioactivity. Since we observed that serum samples contain non-lactogenic substances able to interfere in Nb2 cell bioassay, in this study we extracted PRL molecules from sera of pregnant and non-pregnant normal adults, fetuses and patients with prolactinoma and evaluated the ability of partially purified PRL to stimulate Nb2 cell proliferation. The preliminary immunopurification of PRL samples, conferred good sensitivity and specificity to PRL biological assay. Whenever possible, bioactivity values were correlated with glycosylated-PRL levels (G-PRL), the major posttranslational modification known to reduce PRL bioactivity. The ratio of bioactive (B-) vs immunoreactive PRL (I-PRL) (B/I) in normal subjects was 0.9 +/- 0.1 (mean +/- SD), and not affected by TRH and sulpiride administration. PRL B/I ratio did not change during pregnancy, both in maternal (0.8 +/- 0.1) and fetal circulation (1.0 +/- 0.01). In patients with prolactinoma PRL B/I ratios (0.8 +/- 0.18) were in the normal range. However, in 2 women with microprolactinoma, with a clear discrepancy between high I-PRL levels and mild clinical features, a significantly reduced PRL B/I ratio was observed (0.51 +/- 0.08 and 0.52 +/- 0.1 respectively). Conversely, a woman with clear clinical features of hyperprolactinemia, but border-line elevated I-PRL levels had a PRL B/I ratio in the upper limit of normal range. No variation in G-PRL vs NG-PRL percentages was observed in all the cases studied. In conclusion, our data show that physiological and pathological conditions of hyperprolactinemia, including fetal life, are associated in the majority of cases, with the secretion of PRL molecules with unchanged mitogenic activity on Nb2 cells. Nb2 PRL bioassay may be an useful tool to explain the discrepancies between clinical features and immunoreactive PRL levels in some particular cases.

Presence of growth hormone secretagogue receptor messenger ribonucleic acid in human pituitary tumors and rat GH3 cells

A novel G11-protein-coupled receptor specific for synthetic GH-releasing peptides (GHRPs) has recently been cloned and sequenced. Two forms exist, types 1a and 1b, the latter of which is biologically inactive. Using RT-PCR, we looked for the presence in tumorous pituitary cells of messenger ribonucleic acid (mRNA) for this novel GH secretagogue receptor (GHS-R). Both subtypes of GHS-R mRNA were detected in all six human pituitary somatotropinomas removed from patients with acromegaly. In culture, four of the tumors exhibited strong responses to GHRP-2 in terms of both phosphatidylinositol (PI) hydrolysis and GH secretion, but two were resistant. There was no apparent difference in the type 1a and type 1b expression pattern, as judged by RT-PCR, between responsive and nonresponsive tumors. Similarly, the rat pituitary tumor cell line, GH3, was found to express GHS-R mRNA, although these cells also did not respond to GHRPs. RT-PCR failed to detect GHS-R mRNA in eight functionless human pituitary tumors. In contrast, prolactinomas were found to express the receptor and, in culture, significant stimulation of PRL secretion and PI hydrolysis occurred in two of three tumors tested. These results demonstrate that tumorous somatotrophs express the GHS-R gene and that the occasionally observed nonresponsiveness of somatotropinomas to GHRPs is not due to the absence of the biologically active type 1a receptor. Additionally, human pituitary prolactinomas also express GHS-R and are able to respond to GHRPs in terms of PI hydrolysis and PRL secretion. In contrast, GHS-R gene expression does not appear to be associated with human functionless pituitary tumors.

Prolactinomas express human heparin-binding secretory transforming gene (hst) protein product: marker of tumour invasiveness

BACKGROUND AND OBJECTIVE

We have shown previously that heparin-binding secretory transforming gene (hst) overexpression in rat pituitary cells mediates lactotroph tumour growth and stimulates PRL transcription, and that transforming sequences of the gene, which encode fibroblast growth factor-4 (FGF-4), are expressed in human prolactinomas. To further determine the role of hst in human PRL-secreting adenoma pathogenesis we studied the presence of hst protein in these tumours and other types of human pituitary adenoma.

PATIENTS AND DESIGN

Pituitary adenoma tissue samples were obtained at surgery from 14 patients with PRL-secreting adenomas, 5 patients with GH-secreting tumours, 3 with ACTH-secreting, and 13 patients with nonfunctioning tumours. Two normal pituitary tissue specimens were also studied. Clinical data, including tumour invasiveness assessed by preoperative MRI studies, were available. For hst protein immunolocalization, tumour frozen sections were immunostained with antihuman FGF-4 antibody. Immunoperoxidase staining for the proliferation-related nuclear antigen Ki-67 was performed using MIB-1 monoclonal antibody.

RESULTS

Normal anterior pituitary cells did not contain immunoreactive hst protein. Lactotrophs in five of 14 prolactinomas (36%) stained strongly for hst compared with immunoreactive pituicytes in only one of 21 nonfunctioning, GH-, and ACTH-secreting adenomas (P = 0.05). Immunoreactive hst in adenoma cells was detected in 3 of 5 invasive prolactinomas, and in 2 of 9 noninvasive PRL-cell adenomas. Immunostaining for the proliferation-related antigen Ki-67 showed a higher proliferation index in hst-positive adenomas (3.94 + 0.85%) as compared with those immunonegative for hst (1.98 + 0.7%; P = 0.05).

CONCLUSIONS

hst protein may be directly involved in prolactinoma development or progression, particularly in invasive tumours, probably due to the growth promoting effects of FGF-4.

Identification of proliferating human anterior pituitary adenoma cells in vitro

A method to determine whether dispersed human anterior pituitary adenoma cells proliferate in mixed culture was developed. Fifteen pituitary adenomas were dispersed enzymatically to single cells, following which twelve were double immunostained after eight days. Proliferating cells were identified immunologically following one hour of bromo-deoxyuridine incorporation. Adenoma cells were subsequently identified with an anti-neuron-specific enolase antibody system. A time course of bromo-deoxyuridine labelling was performed on three nonfunctional adenomas over a four day period, with bromo-deoxyuridine being added to cultures at one hour, 24 hours and four days prior to immunostaining. Double immunolabelled cells were unambiguously identified by a dark brown nucleus surrounded by red cytoplasm. Eight out of 12 pituitary adenomas (two prolactinomas, three nonfunctional, three growth hormone secreting) showed an increased bromo-deoxyuridine labelling index (range 0.1%-1.4%). Bromo-deoxyuridine incorporation over four days showed an increase in bromo-deoxyuridine from 0.02%, 0.03% and 3.3% at one hour to 10.1%, 1.3% and 5.0% at four days, respectively, but evidence of mitosis was scant. This study shows that pituitary adenomas may proliferate in vitro and that this double immunostaining method may be used as an in vitro proliferation assay in a mixed cell population.

Characterization of spherical amyloid protein from a prolactin-producing pituitary adenoma

Prolactin (PRL)-producing pituitary adenomas are in some cases associated with deposition of abundant spherical amyloid; however, the origin of the amyloid has not been established. In this report, a PRL-producing pituitary adenoma composed almost entirely of spherical amyloid was analyzed biochemically. The tumor was removed surgically from a 56-year-old man. Immunohistochemical analysis revealed that residual tumor cells were strongly positive for PRL, while the spherical amyloid was not. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a band of approximately 4 kDa associated with the amyloid, which was not present in a nonamyloid producing prolactinoma. The 4-kDa band is similar in size to other known amyloidogenic peptides. Immunoblot analysis of the tumor material using polyclonal anti-human PRL antibodies revealed a small amount of normal-sized PRL; however, the abundant 4-kDa band was nonimmunoreactive. Amino acid sequencing showed that this peptide represents the first 34 amino acids of the intact PRL protein with a predicted size of 4313 Da. The presence of a small amount of normal-sized PRL in this tumor, as well as elevated circulating levels of PRL implies that intact PRL is being abnormally processed in the formation of spherical amyloid.

Cellular receptors for sex steroids in human pituitary adenomas

Cellular receptors for sex steroids (SSRs) were studied in an unselected series of 55 human pituitary tumors. Cytosolic receptors for estrogen (ERcs) and progesterone (PgRcs) were determined in all cases and cytosolic androgen receptors (ARcs) in 47 cases. Nuclear receptors (ERns, PgRns, ARns) were also studied in 33 cases. ERs and PgRs were determined by an ELISA and ARs by [3H]methyltrienolone binding. Where both cytosolic and nuclear receptors were studied (n = 33), ERs, PgRs and ARs were found in at least one subcellular fraction in 66.7, 60.6 and 81.8% of cases respectively, ERs and ARs being mainly recovered from the cytosol and PgRs from the nucleus. No linear correlation was found between pre-operative plasma steroid hormones and their specific cellular receptors. Nonetheless, the differential expression of SSRs according to sex and gonadal status at the time of surgery strongly supports their regulation by the steroid environment in vivo: PgRcs were more frequent in tumors found in women (41.4 vs 15.4%, P < 0.05), whereas a high expression of ERcs and ARcs (> 15 fmol/mg protein) was more common in tumors found in men (34.5 vs 10.3%, P < 0.05 and 54.5 vs 24.0% respectively). PgRs were positively correlated with ERns, indicating the possibility of estrogen priming of their expression, and negatively correlated with ARs in nuclear fractions. SSRs appeared to be widely distributed among pituitary tumors, although, compared with other hormone-secreting groups, prolactinomas displayed a higher ERc expression (34.8 +/- 11.3 vs 4.8 +/- 5.1 fmol/mg protein, P = 0.007) and gonadotroph cell adenomas lower ARc values (1.3 +/- 0.8 vs 38.2 +/- 10.6 fmol/mg protein, P = 0.048). Microadenomas were characterized by a higher PgR expression than macroadenomas, whereas hemorrhagic (macro)adenomas were characterized by a high ER expression (> 90%). The present results indicate that most pituitary tumors are targets for sex steroids, SSR expression being partially triggered by the steroid environment itself. Possible physiopathological and therapeutic implications of these findings are discussed.

Demonstration of activin in normal pituitary and in various human pituitary adenomas by immunohistochemistry

Inhibins and activins have been known to modify the secretion of various pituitary hormones. To study whether inhibins and activins are present in human pituitary tissues, immunohistochemical studies with antisera to activin A and inhibin alpha subunit were performed on 9 human pituitary adenoma tissue specimens and one sample of normal pituitary tissue adjacent to one adenoma. Activin immunoreactivities were demonstrated in the cytoplasms of one GH and one PRL and two non-functioning adenomas and one normal pituitary tissue, but they were negative in one PRL, one ACTH, one FSH and two non-functioning adenomas. Thus, the presence and absence of activin in the same type of adenoma in regard to hormone production, suggested that the difference in immunostaining simply reflected the difference in the activin concentration. In contrast to this, inhibin alpha subunit immunoreactivity was not found in any of the tissues studied. These data suggested a local synthesis of activin in the normal pituitary as well as various kinds of pituitary adenoma tissues and its local role in the human pituitary gland.

Heparin-binding secretory transforming gene (hst) facilitates rat lactotrope cell tumorigenesis and induces prolactin gene transcription

We have shown previously that human prolactinomas express transforming sequences of the heparin-binding secretory transforming gene (hst) which encodes fibroblast growth factor-4 (FGF-4). To elucidate the role of hst in pituitary tumorigenesis we treated primary rat pituitary and pituitary tumor cell cultures with recombinant FGF-4 and also stably transfected pituitary cell lines with full-length human hst cDNA. Transfectants were screened for hst mRNA expression and FGF-4 production. FGF-4 (0.1-50 ng/ml) caused a dose-dependent 2.5-fold increase of prolactin (PRL) secretion (P < 0.001) in GH4 cells and up to 60% (P < 0.05) in primary cultures, while decreasing growth hormone release (P < 0.001). GH4 hst transfectants displayed markedly enhanced basal PRL secretion (threefold, P < 0.001) and also proliferated faster (P < 0.001). FGF-4 treatment of wild-type GH4 cells, transiently transfected with an expression construct (rPRL.luc) containing a luciferase reporter driven by the rPRL promoter, resulted in a dose-dependent increase of up to 3.3-fold in PRL transcriptional activity. Tumors derived from in vivo subcutaneous injection of GH4 hst-transfected cells strongly expressing FGF-4 grew more aggressively as assessed by histologic invasiveness and proliferating cell nuclear antigen staining (P < 0.01). The results indicate that hst overexpression mediates lactotrope tumor growth and potently stimulates PRL synthesis. Thus, hst may directly facilitate prolactinoma development via paracrine or autocrine action of its secreted protein, FGF-4.

Human TRH receptor messenger ribonucleic acid levels in normal and adenomatous pituitary: analysis by the competitive reverse transcription polymerase chain reaction method

OBJECTIVE

Little is known about the mechanism of diversity in in-vivo hormonal responsiveness to TRH in patients with functional pituitary adenomas. In order to clarify the relation between the responsiveness to TRH and TRH receptor messenger ribonucleic acid (mRNA) expression, we attempted to measure TRH receptor mRNA levels in human pituitary adenoma tissues by competitive reverse transcription polymerase chain reaction (RT-PCR) method.

PATIENTS

Pituitary tissue samples were obtained at autopsy from 5 patients without pituitary disease. Pituitary adenoma tissue samples were obtained at surgery from 18 patients with pituitary adenoma (4 non-functioning, 8 prolactinoma, 4 acromegaly, 1 Cushing's disease and 1 FSH producing adenoma).

METHODS

Partial TRH receptor cDNA from a human GH producing adenoma cDNA library was amplified by PCR under low stringency conditions using primers encoding the transmembrane domains III and VI of pituitary TRH receptor cDNA. The partial sequence of the amplified cDNA determined by a dideoxy-chain termination method was identical to the corresponding sequence of human TRH receptor cDNA. A competitor was generated by deleting the inner 111 bp from the amplified TRH receptor cDNA and subcloning. RNA extracted from human pituitary was reverse transcribed and co-amplified with competitor by PCR under higher stringency conditions. The TRH receptor mRNA levels, expressed as the relative intensity against the amplified levels of competitor, were compared among various pituitary tissues.

RESULTS

The relative TRH receptor mRNA levels of pituitary tissues in patients without pituitary disease were detectable and variable (M +/- SD) (0.370 +/- 0.231, n = 5), and slightly but not significantly lower than those in patients with pituitary tumours (0.598 +/- 0.265, n = 18). In patients with prolactinoma, the relative levels of TRH receptor mRNA were quite variable (0.02-1.170, 0.604 +/- 0.358, n = 8) and not correlated with PRL responsiveness to TRH (responder 0.457; non-responder 0.340-0.950). In patients with acromegaly, TRH receptor mRNA was detectable not only in the paradoxical GH responder to TRH (0.718) but also in the non-responder (0.758 and 0.765). In one patient with Cushing's disease, a relatively low level of TRH receptor mRNA could be detected (0.415). In the patient with a FSH producing tumour whose plasma FSH did not respond to TRH, a small amount of TRH receptor mRNA was detectable (0.447).

CONCLUSIONS

In patients with functioning pituitary adenomas, hormonal responsiveness to TRH in vivo might not be assessable by TRH receptor mRNA levels in the adenoma cells.

Neural cell adhesion molecule expression in human pituitary adenomas

Neural cell adhesion molecule (NCAM) is a cell surface glycoprotein whose expression may be important in metastatic or local growth of neoplasms. Expression of NCAM in human pituitary adenomas was assessed on snap-frozen and Bouin's and/or formalin-fixed, paraffin-embedded archival tissue using a sensitive alkaline phosphatase-antialkaline phosphatase method of immunostaining with the monoclonal antibody, NKH-1. The 20 pituitary adenoma patients consisted of 13 males and 7 females, ages 19-78 years, with null cell macroadenomas (3), plurihormonal macroadenomas (4), weak gonadotropic macroadenomas (5), growth hormone-prolactin adenomas (2), and prolactinomas (6). Eight of the adenomas were clinically invasive. The snap-frozen material from 14 pituitary tumors showed immunostaining for NCAM in either a cytoplasmic, peripheral membranous, or mixed pattern; 2 of 3 prolactinomas showed patchy immunostaining. The Bouin's and/or formalin-fixed pituitary adenoma specimens from 6 clinically invasive cases showed less distinct NCAM localization but 4 out of 6 showed diffusely positive NCAM immunostaining, with greatest intensity appreciated on the Bouin's-fixed tissue. There was no correlation between NCAM staining pattern and invasive characteristics of the tumors. These results suggest that NCAM expressivity is not a useful marker for assessing pituitary adenoma tumor invasiveness.

Prolactinoma in a sheep

This report describes the incidental finding of an acidophilic adenoma of the pituitary gland in an adult ewe with clinical signs of a nervous disorder. Immunohistochemical examination demonstrated prolactin in the tumour cells, justifying the use of the term "prolactinoma" for the first time in veterinary medicine. This tumour should be considered in the differential diagnosis of nervous diseases of sheep.

Heterogeneous expression of two somatostatin receptor subtypes in pituitary tumors

The expression of two somatostatin receptor subtypes, SSTR1 and SSTR2, was studied in 27 pituitary tumors and 1 chronic lymphocytic leukemia pituitary infiltrate. Solution hybridization techniques were used for RNA analysis. SSTR1 and SSTR2 were, respectively, expressed in 3 of 7 and 9 of 10 GH-secreting tumors, 1 of 9 and 5 of 9 nonfunctioning tumors, 4 of 5 and 0 of 5 of prolactinomas, and 1 of 3 and 0 of 3 ACTH-secreting tumors. The chronic lymphocytic leukemia infiltrate expressed the SSTR2 subtype. No correlation was detected among tumor size, level of hormonal hypersecretion, and somatostatin receptor expression status. Two acromegalic patients who responded to octreotide therapy exclusively expressed the SSTR2 subtype in their tumors. The results indicate that two SSTR subtypes are heterogeneously expressed in different pituitary adenoma cell types.

An investigation of tumor 1H nuclear magnetic resonance spectra by the application of chemometric techniques

1H nuclear magnetic resonance (NMR) spectra of tumors and normal tissue include signals from all hydrogen-containing metabolites and can therefore be considered multicomponent multivariate mixtures. We have obtained 1H spectra from perchloric acid extracts of three normal tissues (liver, kidney, and spleen) and five rat tumors (GH3 prolactinoma, Morris hepatomas 7777 and 9618a, LBDS1 fibrosarcoma, and Walker 256 carcinosarcoma). We have applied several different chemometric methods to analyze the data. First, we used principal component analysis, cluster analysis, and an optimized artificial neural network to develop a classification rule from a training set of samples of known origin or class. The classification rule was then assessed using a set of unknown samples. We were able to successfully determine the class of each unknown sample. Second, we used the chemometric techniques of factor analysis followed by target testing to investigate the underlying biochemical differences that are detected between the classes of samples.

The presence, characterisation and synthesis of neuromedin B in the human pituitary gland

Neuromedin B is a 10-amino-acid mammalian peptide of the bombesin family. We have used a specific radioimmunoassay and Northern blot hybridisation to investigate the possible synthesis of neuromedin-B-like immunoreactivity in the human pituitary gland. The concentration of immunoreactive neuromedin B in whole human pituitary was 15.2 +/- 4.2 pmol/g wet weight in males and 12.8 +/- 2.7 pmol/g wet weight in females (mean +/- SEM, n = 10). In pituitary tumour extracts, neuromedin B immunoreactivity was 9.1 +/- 1.7 pmol/g wet weight (mean +/- SEM, n = 14) in inactive tumours, 18.4 +/- 6.9 pmol/g wet weight (mean +/- SEM, n = 4) in somatotrophs and 10.4 +/- 2.7 pmol/g wet weight (mean +/- SEM, n = 2) in prolactinomas, with no apparent significant difference between the groups. Gel permeation chromatography of pituitary extracts revealed two immunoreactive peaks, the major one of which corresponded in position to that of neuromedin B-32 and a later minor peak to the position of the neuromedin B-10 standard. On fast protein liquid chromatography, neuromedin-B-like immunoreactivity again eluted in two peaks, a minor peak corresponding to the synthetic neuromedin B standard, and a major more hydrophobic peak which was the big neuromedin B form. Northern blot analysis of poly(A)+RNA from human pituitaries revealed the presence of a hybridising band of between 750 and 850 base pairs. These results suggest that neuromedin B is synthesised in the human pituitary gland where it may be of importance in the regulation of pituitary function. Furthermore, the adenomatous condition is not associated with abnormal levels of this peptide.

Interleukin-6, a growth promoting cytokine, is present in human pituitary adenomas: an immunocytochemical study

OBJECTIVE

The aim of this study was to investigate the presence of interleukin-6 (IL-6) in human pituitary adenomas.

DESIGN

Immunocytochemistry was performed in 15 cases of pituitary adenomas obtained at transsphenoidal surgery.

PATIENTS

Fifteen cases of pituitary adenomas were examined; these included five GH-secreting adenomas, four prolactinomas, four ACTH-secreting adenomas and two null-cell ('functionless') adenomas.

MEASUREMENTS

Each tumour was stained for the presence of IL-6 by means of the avidin-biotin-peroxidase complex (ABC) technique, and was also stained for GH, prolactin, ACTH and alpha-subunit by conventional immunocytochemistry.

RESULTS

Fourteen of the 15 tumours examined, excepting one GH-secreting tumour, demonstrated clusters of IL-6 positively stained cells; the specificity of the staining was established by a significant decrease in staining in parallel sections of all tumours studied when the anti IL-6 antibody was preabsorbed with recombinant human IL-6.

CONCLUSIONS

It is concluded that IL-6 immunoreactivity is present in human pituitary tumours, and is independent of the specific secretory cell product. The role of this cytokine in the pathogenesis of such tumours requires further investigation.

Concanavalin-A-bound and -unbound prolactin in normal and hyperprolactinaemic rats

Concanavalin-A (Con-A)-bound and -unbound forms of prolactin were studied in female Wistar-Furth rats, both normal and with hyperprolactinaemia induced by treatment with oestrogen or a prolactinoma graft. In normal rats, Con-A-bound prolactin was the major circulating form (more than 50%) and a minor pituitary component (less than 10%), essentially as 25 kDa prolactin. In oestrogen-treated rats, plasma prolactin levels were 100-fold higher and pituitary weight was fivefold higher than in the controls, but total pituitary prolactin content was unmodified. Under oestrogen, Con-A-bound prolactin represented about one-third of the total hormone levels in the plasma and less than 10% in the pituitary. In the pituitary, bound prolactin was found essentially as 25 kDa and unbound prolactin as 22, 30 and 40-45 kDa. A similar increase in plasma prolactin levels was induced 6 months after the graft of a prolactinoma. Pituitary weights and total pituitary prolactin contents were slightly decreased. Plasma and pituitary Con-A-bound prolactin levels were similar to those observed in oestrogen-treated rats. On the other hand, unbound prolactin was only present as a 22 kDa monomer. In the tumour, Con-A-bound prolactin (essentially as 25 kDa prolactin) represented one-third of the total hormone level and unbound prolactin was composed of the 22 and 45 kDa forms, this latter form being partially transformed into 22 kDa by heating.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue kallikrein is associated with prolactin-secreting cells within human growth hormone-secreting adenomas

Tissue kallikrein is a serine protease which may be involved in the intracellular processing of prolactin in the anterior pituitary gland. The expression of tissue kallikrein, in the rat, is promoted by oestrogen and inhibited by dopamine. Human and rat prolactinomas contain markedly increased amounts of tissue kallikrein; this is comparatively reduced if patients are pretreated with the dopamine agonist, bromocriptine, before surgery. Some GH-secreting adenomas are mixed and also contain prolactin-secreting cells. We therefore investigated 27 GH-immunostaining human pituitary adenomas for the presence of immunoreactive tissue kallikrein. Sixteen of the adenomas had positive immunostaining for prolactin; eight of these patients had associated clinical hyperprolactinaemia before the tumour was removed. Tissue kallikrein immunoreactivity was found in ten adenomas, all of which also had prolactin immunopositivity. There was a close relationship between the percentage of cells staining for prolactin and tissue kallikrein but not for GH. A further eight adenomas had patchy positivity, i.e. less than 1% of cells immunostained for tissue kallikrein and six of these also had some prolactin-staining cells. Nine out of eleven purely GH-staining adenomas had no tissue kallikrein immunopositivity, the remaining two showing patchy staining. A review of bromocriptine responsiveness, as assessed by mean GH hormone levels during oral glucose tolerance tests before and after therapy was commenced, indicated that patients with adenomas which stained for prolactin and tissue kallikrein were more likely to respond to bromocriptine than those which failed to do so.

Ras mutations in human pituitary tumors

The cellular basis for pituitary neoplasia is poorly understood. Mutations that activate the ras protooncogenes have been identified in a number of different types of human cancers and potentially represent one of the genetic alterations that occur in pituitary tumors. In this study we examined 19 pituitary tumors for the occurrence of ras mutations. The tumor types included 11 nonfunctioning adenomas, 6 somatotroph adenomas, and 2 prolactinomas. Each of the three ras genes (K-ras, N-ras, and H-ras) was amplified from pituitary tumor DNA using the polymerase chain reaction. Oligonucleotide-specific hybridization was used to screen for mutations that inhibit GTPase activity and cause activation of the ras oncogene. No ras mutations were observed in 18 of the pituitary adenomas. However, a mutation was identified in codon 12 of the H-ras gene (Gly to Val) in a recurrent prolactinoma that was highly invasive and ultimately proved to be fatal. We conclude that ras mutations are uncommon in pituitary adenomas, but may provide a marker for highly invasive tumors.

A null cell adenoma of the pituitary detected seven years after removal of a prolactinoma. Recurrence or de novo tumourigenesis?

We report an extremely unusual case of prolactinoma which emerged at recurrence as a null cell adenoma. A 53-year-old woman sought medical attention for progressive visual loss and headache. A pituitary tumour was detected by a computed tomographic scan, and hyperprolactinemia was noted. The tumour, removed by a transfrontal surgery, was a chromophobe adenoma, and immunohistochemically the adenoma cells were selectively positive for PRL, which indicated a prolactinoma. Postoperatively, her plasma PRL level was normalized. Seven years later, she noted blurred vision and again sought medical attention. A CT scan demonstrated recurrence of a pituitary tumour. On this occasion, however, she was not hyperprolactinemic. She underwent again a transfrontal resection of the pituitary tumour. Its histology was again a chromophobe adenoma, but the adenoma cells showed no positive immunostaining for any anterior pituitary hormone including PRL, which indicated a null cell adenoma. We have no clear explanation of the pathogenesis underlying her very unusual course. However, null cells (assuming that the original tumour was a mixed adenoma) left behind at the first surgery, or unidentified hypothalamic and/or pituitary derangements might possibly have been responsible for the recurrence. We learned from this patient that recurrent pituitary adenomas may not necessarily have the same endocrine features as did the original tumours. This information appears to make a valid clinical point, because if hormone levels alone are followed after pituitary surgery, recurrent pituitary tumours may be overlooked.

G proteins in normal rat pituitaries and in prolactin-secreting rat pituitary tumors

It is still undetermined which GTP-binding (G) protein is involved in the regulation of prolactin (PRL) release and through which effector. This study shows that, when compared to normal pituitary tissue, the levels of alpha o protein were very low in dopamine (DA)-resistant, PRL-secreting pituitary tumors 7315a and MtTW15, while alpha o mRNA was present in the two tumors. In the MtTW15 tumor alpha i1, alpha i2 and alpha i3 levels were decreased while those of alpha s42 and alpha s47 were increased, and in the 7315a tumor alpha i2, alpha i3 and beta levels were decreased and those of alpha s47 increased. In an estrone-induced, DA-sensitive prolactinoma the levels of alpha i3 were greatly reduced. DA was unable to inhibit basal PRL release by 7315a and MtTW15 and basal cAMP accumulation by adenomatous and MtTW15 cells. Vasoactive intestinal peptide (VIP) increased both cAMP accumulation and PRL release by all cell preparations which could be suppressed by DA with adenomatous and 7315a but not with MtTW15 cells. These and previously published results provide circumstantial evidence that alpha o, alpha i1 and alpha i3 are all involved in the transduction of the DA inhibitory message while alpha s47 transduces cAMP activating messages and alpha s42 is responsible for the constitutive activation of L-type Ca2+ channels, adenylate cyclase and baseline PRL release.