Relationship between basic fibroblast growth factor and transforming growth factor-beta 2 in breast cyst fluid

Women with "apocrine" breast cysts (usually having intracystic Na/K < 3) may have a higher risk of developing breast cancer than women with breast cysts lined by flattened epithelium (usually having intracystic Na/K > 3). In this study the concentrations of basic fibroblast growth factor (bFGF), a potent mitogen, and transforming growth factor-beta 2 (TGF-beta 2), which exerts a growth inhibitory effect on epithelial cell types, were measured in breast cyst fluid and their relationship studied. Both growth factors were measured by "sandwich" enzyme immunometric assays. The concentrations of both bFGF and TGF-beta 2 were significantly higher (P < 0.001) in the Na/K > 3 group (median 444 fmol/L, range: < 56 fmol/L-7,890 fmol/L, n = 23 and median 1,776 pmol/L, range: 20.4 pmol/L-5,000 pmol/L, n = 19 respectively) than in the Na/K < 3 group (median < 56 fmol/L, range: < 56 fmol/L-2,722 fmol/L, n = 21 and median 176 pmol/L, range: 12 pmol/L-1,940 pmol/L, n = 23 respectively). Significantly positive correlations were found between bFGF and TGF-beta 2 (rS = 0.496, n = 37, P = 0.002), bFGF and Na/K (rS = 0.599, n = 44, P < 0.001) and TGF-beta 2 and Na/K (rS = 0.521, n = 42, P < 0.001). The significantly higher concentrations of the growth inhibitory TGF-beta 2 in the Na/K > 3 cyst group may provide an explanation for the lower risk of breast cancer which has been observed in this group of women. The role of bFGF in mammary carcinogenesis is unclear as lower levels of this growth factor are present in breast cancer tissue and breast cancer cell lines than in normal breast tissue and cell lines. The positive correlation between bFGF and TGF-beta 2 may indicate regulation by a common factor or that one of these growth factors may regulate the production of the other. This is the subject of further study.