Effect of a phosphatidylinositol 3-kinase inhibitor wortmannin on radiation and bleomycin sensitivities.

ATM和DNA依赖的蛋白激酶催化亚单位(DNA-PKcs)具有与哺乳动物磷脂酰肌醇3-激酶(PI3-Kinase)催化结构域同源的序列。为了确定ATM和DNA-PKcs在PI3-激酶抑制剂存在下增加细胞对DNA损伤剂敏感性的作用，我们观察了PI3-激酶抑制剂Wortmannin对白霉素(BLM)、丝裂霉素C(MMC)、X射线照射和紫外线(UV9)照射的细胞对白霉素(BLM)、丝裂霉素C(MMC)、X-射线和紫外线(UV9)敏感性的影响。方法：采用2株人肿瘤细胞株(T98G和A172)、1株人成纤维细胞株(LM2 17)、1株共济失调(AT)细胞株(AT3BISV)、1株SCID小鼠细胞株(SCF)和对照小鼠细胞株(CBF)。Wortmannin对所有细胞，包括AT3BISV和SCF，对BLM和X-射线都有增敏作用，但对MMC和UV-射线不敏感。AT和SCID小鼠对BLM和X-射线过敏，对MMC和UV-射线正常敏感是其特征表型。除未检测到DNA-PK活性的SCF外，其余细胞的DNA-PK活性均被Wortmannin抑制至对照的45-65%。Wortmannin还能诱导T98G和SCF细胞的抗辐射DNA合成，但不改变AT3BISV的DNA合成速率。我们的数据表明，Wortmannin降低了ATM蛋白和DNA-PK的活性，表明它可能作为放、化疗的增敏剂。

ATM and DNA-dependent protein kinase catalytic subunit (DNA-PKcs) have been shown to have sequences homologous to the catalytic domains of mammalian phosphatidylinositol 3-kinase (PI3-kinase). In order to determine the contribution of ATM and DNA-PKcs to the increased sensitivity of cells to DNA-damaging agents observed in the presence of PI3-kinase inhibitors, we examined the effects of a PI3-kinase inhibitor, wortmannin, on cellular sensitivity to belomycin (BLM), mitomycin C (MMC), X-irradiation and ultraviolet (UV9-irradiation using2 human tumor cell lines (T98G and A172), a human fibroblast cell line (LM2 17), an ataxia telangiectasia (AT) cell line (AT3BISV), a scid murine cell line (SCF) and control murine cell line (CBF). Wortmannin sensitized all of the cells, including AT3BISV and SCF, to BLM and X-irradiation, but not to MMC or UV-irradiation. Hypersensitivity to BLM and X-irradiation and normal sensitivity to MMC and UV-irradiation are characteristic phenotypes of both AT and scid mice. DNA-dependent protein kinase (DNA-PK) activity was suppressed by wortmannin to 45-65% of the control values in all of the cells except SCF, in which DNA-PK activity was not detected. Wortmannin also induced radioresistant DNA synthesis, which is a cellular phenotype of AT, in T98Gand SCF cells, but did not change the DNA synthesis rates after X-irradiation in AT3BISV.Our data Suggest that wortmannin decreases the activities of both the ATM protein and DNA-PK, indicating that it might be of use as a sensitizing agent for radiotherapy and chemotherapy.