RESUMO
OBJECTIVE: gp130 cytokines are placed as auto-paracrine regulators of pituitary function, since they, as well as their receptors, have been shown to be expressed in and to act in normal and tumoral anterior pituitary cells. The objective of this work was to study their involvement in a model that shows the interaction between different cellular types that participate in a tumorigenic process. DESIGN: The dependence of a pituitary somatotrophic cell line (MtT/S) on a gp130 cytokine-producing folliculostellate (FS) cell line (TtT/GF) for tumorigenesis in vivo has been described. In order to study the participation of gp130 cytokines in the auto-paracrine stimulation of MtT/S growth, we generated MtT/S gp130 sense (gp130-S) and gp130 antisense (gp130-AS) clones stably transfected with pcDNA3/gp130 sense and pcDNA3/gp130 antisense vectors respectively. METHODS AND RESULTS: Functional characterization studies revealed that gp130-AS clones have an inhibited gp130 signalling, and proliferation studies showed that they have an impaired response to gp130 cytokines but respond normally to other independent stimuli. When injected into nude mice, MtT/S clones respond differently depending on cell number; at high concentrations MtT/S clones alone generated tumours equivalent in size to tumours derived from MtT/S plus TtT/GF cells. At low concentrations, MtT/S sense and control clones generated tumours of smaller size than tumours derived from these same clones plus TtT/GF cells, showing a dependence on FS cells. In both cases MtT/S gp130-AS clones had impaired tumour development. Furthermore, vessel density was significantly lower in tumours derived from gp130-AS plus TtT/GF cells. CONCLUSIONS: This study underlines the importance of gp130 cytokines in proliferation and establishes its role in auto-paracrine pituitary growth regulation.
Assuntos
Antígenos CD/metabolismo , Hormônio do Crescimento/metabolismo , Glicoproteínas de Membrana/metabolismo , Adeno-Hipófise/metabolismo , Neoplasias Hipofisárias/etiologia , Animais , Vasos Sanguíneos/patologia , Divisão Celular , Linhagem Celular , Receptor gp130 de Citocina , Camundongos , Camundongos Nus , Transplante de Neoplasias , Comunicação Parácrina , Neoplasias Hipofisárias/irrigação sanguínea , Neoplasias Hipofisárias/patologia , Neoplasias Hipofisárias/fisiopatologia , Ratos , TransfecçãoRESUMO
Two of the most potent cytokines that regulate anterior pituitary cell function are leukemia inhibitory factor and IL-6. These and others like IL-11 and ciliary neurotrophic factor are referred to as the gp130 cytokines because they share the gp130 glycoprotein as a common receptor initial signal transducer. We and others have shown that gp130 cytokines and their receptors are expressed and functional in normal and tumoral anterior pituitary cells. To study the role of gp130 cytokines in tumorigenic process, we generated gp130 cDNA gp130 sense and gp130 antisense (gp130-AS) transfected stable clones derived from lactosomatotroph GH3 cells. We examined hormone secretion and cell proliferation of these clones as well as their tumorigenic properties in athymic nude mice. Although gp130-AS clones, which have low gp130 levels and impaired signal transducer and activator of transcription 3 activity and suppressor of cytokine signaling-3 expression, showed reduced proliferation and hormone secretion (GH and prolactin) in response to gp130 cytokines, they had a normal response to gp130-independent stimuli. Moreover, gp130-AS clones showed a severely impaired in vivo tumor development. In contrast, the overexpressing gp130 clones (gp130 sense) showed no differences, compared with cells transfected with control vector. Thus, the present study provides new evidence supporting a link between gp130 and pituitary abnormal growth.