Bowman-Birk proteinase inhibitor (BBI) modulates radiosensitivity and radiation-induced differentiation of human fibroblasts in culture.

The radiosensitivity and differentiation pattern of cultured normal human fibroblasts was analysed as a function of treatment of the cells with the Bowman-Birk proteinase inhibitor (BBI). Upon irradiation with doses from 0 to 8 Gy normal human fibroblasts are induced to a premature terminal differentiation within 14-21 days of postirradiation incubation. Treatment of the cells with 10 microM BBI for 2 h prior to the irradiation procedure resulted in a significant shift of the radiation survival curve, increased SF2 values 0.63 vs. 0.84 and the cell type composition of the test fibroblast cultures. Upon pretreatment with BBI the radiation-induced premature terminal differentiation of progenitor fibroblasts to postmitotic fibrocytes could significantly be inhibited. Based on this data, it can be postulated that BBI may serve as a radioprotector of normal fibroblasts which are involved in radiation-induced tissue injuries like radiation fibrosis.