Relationship between the localization of fibroblast growth factor 9 in prostate cancer cells and postoperative recurrence

BACKGROUND: Fibroblast growth factor 9 (FGF9) enhances cell proliferation and invasiveness in several malignant diseases. The aim of the present study is to investigate the role of FGF9 in postoperative recurrence after radical prostatectomy. METHODS: Cell viability and invasion of LNCaP cells were assessed using MTT assay and Matrigel invasion assay, respectively, in the presence or absence of treatment with recombinant FGF9. Tissues obtained during a radical prostatectomy in 133 male patients were immunohistochemically stained using anti-FGF9 antibody. RESULTS: Cell viability and invasion of LNCaP was significantly enhanced by treatment with recombinant FGF9. Immunohistochemical staining detected FGF9-positive cells in 20 samples. The prevalence of FGF9-positive cells in cases with a Gleason score of 8 or higher was 34.2%, which was significantly higher than that in those with Gleason scores of 7 or lower (7.3%, P = 0.0003), respectively. The 3-year biochemical relapse-free survival rate was 17.5% in cases with FGF9-positive cells, which was significantly lower than that in cases in which FGF9-positive cells were not detectable (75.5%, P < 0.0001). CONCLUSIONS: These results indicate that FGF9 can stimulate proliferation and invasion in prostate cancer cells, thus FGF9 could be a candidate of a predictive factor for recurrence after radical prostatectomy.