Differential expression of acidic and basic fibroblast growth factors in benign prostatic hyperplasia identified by immunohistochemistry

Objectives To detect the expression and to determine the relative cellular locations of the two peptide growth factors, acidic fibroblast growth factor (a-FGF) and basic (b)-FGF in tissues from human benign prostatic hyperplasia (BPH). Materials and methods A series of 50 sequential and unselected cases of human BPH tissues, obtained after transurethral prostatectomy, was examined. Adjacent sections of formalin-fixed and paraffun wax-embedded tissues were stained immunohistochemically for expression of a-FGF and b-FGF using well-characterized and commercially available antibodies. The stained tissue sections were assessed for the cellular distribution of immunohistochemical products and analysed according to the relative intensity of staining as well as the spatial relationships of positively stained cells. Results Acidic-FGF was weakly expressed with a pancytoplasmic distribution within luminal glandular epithelial cells in regions of prostatic intra-epithelial neoplasia (both PIN I and II) but not by non-dysplastic normal or hyperplastic tissues. No expression of a-FGF was detected in basal epithelial cells or in the stromal compartment of any tissue examined. In contrast, b-FGF was strongly expressed within the cytoplasm of all basal epithelial cells, but not by luminal epithelial cells, in morphologically normal regions of all cases examined. Basal expression of b-FGF was diminished, or absent, in regions of mild epithelial dysplasia, particularly those strongly expressing a-FGF. Extensive nuclear and cytoplasmic expression of b-FGF occurred predominantly in smooth muscle-type stromal cells but not in all types of stromal cells. Conclusions This study confirmed both a differential and a reciprocal expression of a-and b-FGF in non-dysplastic prostatic hyperplasia and in mildly dysplastic regions of prostatic tissues. While only small amounts of a-FGF were expressed in BPH, exclusively in the luminal epithelial compartment, its consistent appearance in PIN I and II suggests that it might contribute to the early stages of PIN. Conversely, b-FGF may be an important mediator of stromal-epithelial interaction during the pathogenesis of BPH. These results provide new information about the relative expression of these growth factors, particularly in the architectural relationships between different cell-types within normal and non-malignant prostatic tissues.