Identification of multiple proliferative growth factors in breast cyst fluid.

Gross cystic disease is a common benign breast disease that is associated with a twofold to fourfold increase in breast cancer risk. Both diseases are hormonally induced and may share a common biochemical environment conducive to abnormal proliferative responses. A large collection of breast cyst fluid samples was analyzed for growth factors associated with cell proliferation: epidermal growth factor (EGF), insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II), platelet-derived growth factor (PDGF), transforming growth factor-alpha (TGF-alpha), and transforming growth factor-beta (TGF-beta). The data demonstrate that significant amounts of proliferative growth factors are present in breast cyst fluid of all cyst subtypes. The presence of IGF-II, PDGF, and TGF-beta in breast cyst fluid was confirmed for the first time. EGF, PDGF, and TGF-beta concentrations in breast cyst fluid were several times greater than reported for serum; IGF-I and IGF-II concentrations were several times lower. In the first 100 samples tested, no TGF-alpha was detected. Only EGF and IGF-II levels demonstrated a consistent correlation with apocrine type 1 cysts. These results demonstrated that effective concentrations of proliferative growth factors are in breast cyst fluid and suggest that adjacent breast tissue may be a probable source of synthesis. Growth factor profiles of breast cyst fluid may indicate the presence in breast tissue of a hormonal and proliferative environment permissive to subsequent cancer growth.