The Role Of NGF And Its Receptor In Dopamine Agonist-resistant Prolactin-secreting Pituitary Adenoma

Part I Study of correlativity between the NGFR expression and thebiological characters in prolactin-secreting pituitary adenomaObjective To explore the relationship between the expression of two receptors of nerve growth factor(NGF) , proliferation nuclear antigen (PCNA) and the biological characters of Prolactinomas. Methods The tumor specimens of 38 patients with prolactinoma was obtained by transsphenoid approach from 2003 to 2005.The expression of two receptors of nerve growth factor(NGF), Proliferation nuclear antigen (PCNA) was detected by immunohistochemistry methods. The patients were classified according to the invasion of surrounding structures or not, the volume of tumor, sex, the level of Prolactin secretion and the sensitivity to the dopamine agonist therapy. Results The expression of P75-NGFR was lower in invasive Prolactinomas , the tumor with high level of prolactin , macroadenomas , dopamine agonist -resistance adenomas than non-invasive Prolactinomas, the tumor with low level of prolactin , microadenomas, dopamine agonist-responsive adenomas respectively(p<0.05). The expression of was PCNA relatively higher, but the expression of another receptor of NGF (TrkA) is no differences between the each group. The PCNA in male prolactinomas was higher than that in female prolactinomas (p<0.05) and the two receptors of NGF were no difference between the male and female groups. Conclusions The expression of P75-NGFR could indirectly reflect the proliferation activity and the sensitivity to dopamine agonist therapy of the tumor. P75NGFR could be a novel tumor suppression gene of certain adenomas.Part II The effect of proliferation activity and cell cycle inGH3 cell treated by NGFObjective To explore the mechanism of differentiation induced of by NGF administration in GH3 cell by observing the changes of proliferation, cell-cycle and the expression of its receptor. Methods The GH3 cell was treated by NGF with different concentrations, MTT was detected the proliferation of GH3 by NGF, and Flow cytometry was used for evaluating the cell cycle and the expression of two NGF receptors was detected by immunohistochemistry and western blot after NGF administration. Results The proliferating ability of GH3 cell was decreased by NGF, The GH3 cell showed the reduction of proportion of S phase and cell was arrested at G0/G1 phase. The expression of P75NGFR was up-regulated after NGF treatment. Comparing with the control group, All the effect at other groups were significantly different. The maximal inhibition effect of proliferation and the expression value of P75NGFR were achieved at 50ng/ml NGF. Conclusions NGF could induce the differentiation of GH3 cell into the more benign phenotype, the mechanism of reduction of proliferation and proportion of S phase after NGF treatment were probably due to the up-regulation the P75NGFR. Part III The effect of secretion activity of prolactin and expression of dopamine receptor-2 in GH3 cell treated by NGFObjective To further investigate the mechanism treated by NGF through observing the changes of PRL secretion activity and the expression of dopamine receptor-2. Methods ELISA was measured for PRL basal secreting level and changes of its secreting level after administration the NGF and bromocriptine alone and combination, in GH3 cell. RT-PCR methods was detected the dopamine receptor-2 mRNA before and after administration the NGF. Results The inhibition effect of NGF on PRL secretion was little, and combination with bromocriptine could decrease the PRL secreting level obviously. Comparing with the other groups, the difference was statistically significant (p<0.05). The reexpression of dopamine receptor-2 mRNA was observed in GH3 cell treated by NGF and this effect was blocked by anti-NGF antibody. Conclusions NGF could enhance the inhibition effect of bromocriptine on PRL secretion, this action may be related to induction of the reexpression of dopamine receptor-2.