FGF2/FGFR1 pathway inhibition modulates the proliferation of secreting pituitary tumor cells

Abstract

Pituitary neuroendocrine tumors (PitNET) progress and behavior is associated with the participation of numerous molecules, which could be proposed as therapeutic targets. A frequent alteration is the Fibroblast Growth Factor (FGF2) and its receptor type 1 (FGFR1), whose deregulation was observed in different neoplasms and could be involved in the regulation of cell proliferation. The objective was to determine the effect of FGFR1 inhibition on the proliferation of somatolactotroph tumor cells.

Somatolactotroph tumor cell line (GH3) cultures were stimulated with FGF2 (10 ng/mL) alone or co-incubated with FGFR1 inhibitor: AZD4547 (AZD; 0.1-1-5-10 µM) for 24 h, by triplicate in independent experiments. Cell viability was determined by MTT assay, proliferative response by BrdU incorporation, cell cycle phases from flow cytometry by Propidium Iodide staining, and apoptosis by DAPI staining. The expression of FGFR1, ERK1/2 and STAT3 total and phosphorylated was evaluated after incubation with FGF2 alone or co-incubated with AZD (5-10 µM) for 30 min by western blot. Statistics: ANOVA-Post test: Tukey.

GH3 cells showed a high expression of FGFR1. FGF2 incubation induced an increase of cell viability and BrdU incorporation, effect that was reversed by dose-dependent of AZD (p<0.05). The stimulation of proliferation induced by FGF2 was associated with an increase of phosphorylated ERK1/2 and STAT3 expression and S and G2/M phases, compared to control cells. In addition, co-incubation with AZD induced inhibition of ERK1/2 and STAT3 phosphorylation, with increased G1 phase and decreased S and G2/M phases vs. FGF2. Furthermore, a significant increase in apoptotic cells was observed when cells were co-incubated with AZD (5-10µM; p<0.05).

These findings show that FGF2/FGFR1/ERK1/2-STAT3 pathway is key in the modulation of proliferation in somalactotroph pituitary tumor cells, where by FGFR1 inhibitor use in secreting PitNETs, ​​with high expression of the receptor, could be complement in the current therapies.