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Published on: July 27, 2022
Selective radioprotection of normal tissues by Bowman-birk proteinase inhibitor (BBI) in mice
Klaus Dittmann1, Mahmoud Toulany, Johannes Classen
1Division of Radiobiology and Environmental Research, Department of Radiation Oncology, University of Tuebingen, Germany. klaus.dittmann@uni-tuebingen.de
Background And Purpose:
The efficacy of radiotherapy is limited by the response of normal tissues within the radiation field. The application of normal-tissue-specific radioprotectors may improve the therapeutic benefit of radiotherapy. The purpose of the present study was to explore the in vivo normal-tissue radioprotective potential of Bowman-Birk proteinase inhibitor (BBI), which acts as a normal-cell-specific radioprotector in vitro.
Material And Methods:
The leg contracture assay in mice, a model system assessing radiation-induced fibrotic processes, was used. To determine whether BBI acts also as a radioprotector of tumors (i. e., FSA and FSAII), the tumor growth delay assay was used.
Results:
Radiation induced leg contracture in mice with a maximum of about 8 mm at day 150 after irradiation. Treatment of mice with 100 mg/kg BBI before irradiation reduced leg contracture by > 4 mm, by about 50% (p < 0.05, t-test). Doses < 100 mg/kg were ineffective, and doses > 100 mg/kg did not further increase the degree of radioprotection. By contrast, BBI did not induce radioprotection of either TP53-mutated FSA or TP53-normal FSAII tumor xenografts in mice, which argues for normal-tissue-specific effect.
Conclusion:
BBI acts as a potent selective normal-tissue radioprotector in vitro and in vivo, apparently without protecting tumors, and thus has the potential to improve clinical radiotherapy.
