Insulin-like growth factor-binding protein-1 (IGFBP-1) regulates human schwannoma proliferation, adhesion and survival.

Merlin is a tumour suppressor involved in the development of a variety of tumours including mesotheliomas. Neurofibromatosis type 2 (NF2), a dominantly inherited tumour disease, is also caused by loss of merlin. NF2 patients suffer from multiple genetically well-defined tumours, schwannomas are most frequent among those. Using our in vitro model for human schwannoma, we found that schwannoma cells display enhanced proliferation because of the overexpression/activation of platelet-derived growth factor receptor and ErbB2/3, increased cell-matrix adhesion because of the overexpression of integrins, and decreased apoptosis. Mechanisms underlying schwannomas basal proliferation and cell-matrix adhesion are not understood. Here, we investigated insulin-like growth factor-binding protein-1 (IGFBP-1), which is expressed and released from central nervous system tumours and strongly overexpressed in schwannoma at the mRNA level. IGFBP-1 acts via ß1-integrin and focal-adhesion-kinase (FAK), which are strongly overexpressed and basally activated in schwannoma. Using short hairpin RNA knockdown, small inhibitors and recombinant IGFBP-1, we demonstrate that schwannoma cells, in contrast to Schwann cells, release IGFBP-1 that activates the Src/FAK pathway, via integrin ß1, potentiating schwannoma's proliferation and cell-matrix adhesion. We show that FAK localizes to the nucleus and Src triggers IGFBP-1 production. Further, we observed downregulation of the tumour-suppressor phosphatase and tensin homolog in schwannoma cells leading to increased activity of anti-apoptotic AKT. Thus, IGFBP-1/integrin ß1/Src/FAK pathway has a crucial role in merlin-related tumourigenesis and therefore represents an important therapeutic target in the treatment of merlin-deficient tumours.

Somatostatin 14 affects the pituitary-ovarian axis in infant rats.

The effects of multiple somatostatin (SRIH-14) treatment on the pituitary-ovarian axis were examined in infant rats. Female Wistar rats received subcutaneously two daily 20 µg/100g b.w. doses for five consecutive days (from 11 to 15 days of age). Changes in cell volume, volume density and number per unit area (mm²) of follicle-stimulating (FSH), luteinizing (LH) and somatotropic (GH) immunolabeled cells were evaluated by stereology and morphometry. Serum FSH and LH concentrations were determined by RIA. Ovaries were analyzed by simple point counting of follicles. SRIH-14 treatment significantly reduced FSH and LH cell volume, while their volume density and number per unit area were unaltered. Serum concentrations of FSH and LH were significantly reduced. Volume and volume density of GH cells was significantly decreased after SRIH-14 treatment, while their number per unit area was unaltered. In the ovary, SRIH-14 induced a significant increase in the percentage of primordial follicles followed by a significant decrease in percentage of primary follicles. The number of healthy and atretic preantral follicles was unchanged. It can be concluded that SRIH-14 treatment during the infantile period markedly inhibits pituitary FSH, LH and GH cells. In the ovary, SRIH-14 acts by inhibiting initial folliculogenesis without affecting atretic processes.

Maternal dexamethasone treatment reduces ovarian follicle number in neonatal rat offspring.

Elevated glucocorticoid levels in the gravid female circulation affect a number of endocrine functions in the fetuses and neonates. The aim of this study was to examine the effects of maternal dexamethasone (Dx) administration during late pregnancy on the ovaries of neonatal offspring. On the 16th day of pregnancy, experimental dams received subcutaneously 1.0 mg Dx/kg b.w., followed by 0.5 mg Dx/kg b.w./day on the 17th and 18th days of gestation. The control gravid females received the same volume of saline vehicle. Left ovaries from 5-day-old female pups were stereologically analyzed. The ovary volumes were estimated using Cavalieri's principle. The number of healthy and atretic primordial and primary follicles was estimated using a fractionator-physical dissector method. The number of secondary follicles was determined by exact counts of every fourth section encompassing whole cross-sections of the ovary. The ovary volume was significantly decreased (by 44.4%; P < 0.05) in the group of female pups from Dx-treated mothers comparing to the controls. The numbers of healthy primordial and atretic follicles were 38.8% (P < 0.05) and 50.9% (P < 0.05), respectively, reduced in the ovaries of pups from the Dx-treated mothers, when compared with the control values. There were 53.4% (P < 0.05) fewer healthy primary and 41.8% (P < 0.05) fewer healthy secondary follicles as well. The numbers of atretic primary and secondary follicles were reduced by 60.0% (P < 0.05) and 61.7% (P < 0.05), respectively. It can be concluded that fetal exposure to glucocorticoids decreased the pool of non-growing follicles in the neonatal ovary, whereas the processes of folliculogenesis and atresia remained unaffected.

The effects of chronic SRIH-14 and octreotide administration on the pituitary-adrenal axis in adult male rats.

The effects of chronic treatments with SRIH-14 and octreotide on pituitary corticotropes (ACTH cells) and on the adrenal cortex of male Wistar rats were examined. Adult males received two daily s.c. injections of 20 microg/100 g of body weight of either SRIH-14 or octreotide for 28 consecutive days. ACTH cells were studied using a peroxidase-antiperoxidase immunocytochemical procedure. Morpho-metry was used to evaluate the changes in cell and nuclear volumes (microm3) and volume densities (%) of ACTH-immunoreactive cells. The adrenal cortex was analyzed by histological and morphometric methods. A significant (p<0.05) decrease in body weight and in the absolute weights of the pituitary and adrenal glands was observed in both treated groups. Morphometric parameters of ACTH cells in both treated groups were not significantly (p>0.05) different than in control rats. The absolute volumes of the adrenal gland and adrenal cortex were significantly (p<0.05) decreased in both treated groups. The absolute and relative volumes of the zona glomerulosa (ZG), as well as the cellular and nuclear volumes of the ZG were significantly (p<0.05) decreased in the both treated groups. In rats treated with SRIH-14 and octreotide, the absolute and relative volumes of the zona fasciculata (ZF) and zona reticularis (ZR), as well as their stereological parameters, did not change significantly (p>0.05). The aldosterone levels in the SRIH-14 and ocreotide-treated groups were significantly (p<0.05) decreased - by 13% and 19%, respectively. The concentration of ACTH and corticosterone did not change significantly. Together, these findings show that SRIH-14 and octreotide administration affected the morphological characteristics of the adrenal ZG in a similar manner, and brought about a decrease in plasma aldosterone concentration. These treatments did not affect pituitary ACTH cells or adrenal ZF and ZR functioning.