抄録
A 25-kilodaltons (kDa) protein was isolated from the parasporal inclusion produced from Bacillus thuringiensis subsp.israelensis.This 25-kDa protein inhibited the growth of cultured L1210 murine leukemia cells;IC50of the purified 25-kDa protein was 0.9 μg/ml.This toxic protein interacted with membrane constituent lipids.When the 25-kDa protein was used in combination with anti-cancer drugs, their cytotoxicities against cultured L1210 cells were enhanced.Among the anti-cancer drugs tested, the greatest potentiating effect was found in the case of bleomycin.At a non-toxic dose (0.7μg/ml), the 25-kDa protein potentiated the bleomycin cytotoxicity 6.4 fold. Under the conditions used, the order of potentiation among the anti-cancer drugs tested was as follows: bleomycin (6.4fold), tegafur (4.6), vincristine (4.1), 5-fluorouracil (3.7), vinblastine (3.3), methotrexate (2.5), doxorubicin (2.3), triethylene thiophosphoramide (2.2), neocarzinostatin (2.2) and 1-(4-amino-2 methylpyridine-5-yl) methy1-3-(2-chloroethyl)-3-nitrosourea (1.3).In the case of mitomycin C, the 25-kDa protein was not effective.
