Regulation of pituitary tumors proliferation induced for the FGF2/FGFR1 pathway

Abstract

Abstract:

Dysregulation of the growth factors and their receptors could lead to abnormal growth and progression of pituitary tumors. Previously, we demonstrated an increase in the expression of Fibroblast Growth Factor 2 (FGF2) in the experimental prolactinomas development, suggesting its participation in tumor development but the molecular mechanisms that generate this effect still now unknown. The aim was to determine the role of FGF2, receptor 1 (FGFR1) and the MEK-ERK1/2 pathway on the proliferation of pituitary tumor cells.

Somatolactotroph (GH3) and corticotroph (ATt20) pituitary tumor cell lines stimulated with FGF2 (10 and 100 ng / mL) were used. The expression of FGFR1 was evaluated by western blot. Cell viability was determined by MTT assay after stimulation with FGF2 for 24-48h on medium with or without 10% serum. The proliferative response was analyzed by incorporation of BrdU for 24h and the MEK-ERK1/2 participation by ERK1/2 phosphorylation by western blot, after FGF2 stimulus for 30min. Additionally, the MEK inhibitor PD 98059 (50uM) was used. Statistics: ANOVA-Post test: Tukey.

The expression of FGFR1 was higher in GH3 than in ATt20. FGF2 induced a significant increase in cell viability on GH3at 24 and 48h to both doses, while an increase (p> 0.05) was only observed in ATt20 after stimulation with FGF2 100ng/mL for 48h. Considering that FGF2 effect in GH3 was major, we continue working on this cell line. The expression levels of ERK1/2 phosphorylated increased after FGF2 (10 and 100ng / mL) stimulus for 30min (p˂0.05 vs Control). Cell viability and BrdU incorporation was significantly higher in the cultures treated with both doses to FGF2 in presence of serum, effect that was reversed by PD 98059.

These findings show that FGF2/FGFR1/ERK1/2 pathway participates in the increase of proliferation in GH3 lactosomatotroph tumor cells, which present greater expression of FGFR1, effect that was enhanced in serum medium which would be represent part tumor microenvironment in the tissue.