Radiosensitization of human tumor cells by the phosphatidylinositol3-kinase inhibitors wortmannin and LY294002 correlates with inhibition of DNA-dependent protein kinase and prolonged G2-M delay.
Radiosensitization of human tumor cells by the phosphatidylinositol3-kinase inhibitors wortmannin and LY294002 correlates with inhibition of DNA-dependent protein kinase and prolonged G2-M delay.
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发表时间：
1997-07
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通讯作者：
Kenneth;-E.;Rosenzweig;Matthew;-B.;Youmell;Sanjewani;-T.;Palayoor;Brendan;-D.;Price
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作者：
Kenneth;-E.;Rosenzweig;Matthew;-B.;Youmell;Sanjewani;-T.;Palayoor;Brendan;-D.;Price
磷脂酰肌醇（PI）3-激酶基因家族的成员，包括共济失调毛细血管扩张基因和DNA依赖性蛋白激酶（DNA-PK），参与调节细胞的放射敏感性。我们研究了两种结构无关的PI 3-激酶抑制剂渥曼青霉素和LY 294002，以确定它们是否抑制DNA-PK并增加细胞的放射敏感性。PI 3-激酶抑制剂渥曼青霉素和LY 294002是人肿瘤细胞的有效放射增敏剂，在SW 480细胞中，增敏比（10%存活率）分别为2.8和1.9。Wortmannin和LY 294002抑制纯化的DNA-PK的激酶活性，并使细胞DNA-PK激酶活性失活。细胞DNA-PK活性的抑制发生在引起放射增敏的相同浓度的渥曼青霉素下，并且在一系列肿瘤细胞系中发现了这种相关性。然而，无论是DNA-PK（scid细胞）或共济失调毛细血管扩张蛋白缺陷的细胞，也部分敏化辐射渥曼青霉素，表明一个以上的蛋白激酶参与渥曼青霉素的作用机制。Wortmannin也影响了G2-M检查点。SW 480细胞在照射后20 h出现可逆的G2-M期延迟。然而，wortmannin处理的SW 480细胞有一个延长的G2-M延迟，超过75%的细胞被逮捕在G2在50 h postradiation。这表明在PI 3-激酶家族成员的抑制后显著的未修复的DNA损伤的积累。因此，PI 3-激酶抑制剂可能代表一类新的抑制DNA损伤修复的放射增敏剂。
Members of the phosphatidylinositol (PI) 3-kinase gene family, including the ataxia telangiectasia gene and the DNA-dependent protein kinase (DNA-PK), are involved in regulating cellular radiosensitivity. We have investigated two structurally unrelated PI 3-kinase inhibitors, wortmannin and LY294002, to determine whether they inhibit DNA-PK and increase cellular radiosensitivity. The PI 3-kinase inhibitors wortmannin and LY294002 were effective radiosensitizers of human tumor cells, with sensitizer enhancement ratios (at 10% survival) of 2.8 and 1.9, respectively, in SW480 cells. Wortmannin and LY294002 inhibited the kinase activity of purified DNA-PK and inactivated cellular DNA-PK kinase activity. Inhibition of cellular DNA-PK activity occurred at the same concentrations of wortmannin that caused radiosensitization, and this correlation was found in a range of tumor cell lines. However, cells deficient in either DNA-PK (scid cells) or the ataxia telangiectasia protein were also partly sensitized to radiation by wortmannin, indicating the involvement of more than one protein kinase in the mechanism of action of wortmannin. Wortmannin also affected the G2-M checkpoint. SW480 cells had a reversible G2-M delay of 20 h following irradiation. However, wortmannin-treated SW480 cells had a prolonged G2-M delay; more than 75% of cells were arrested in G2 at 50 h postirradiation. This suggests the accumulation of significant unrepaired DNA damage following inhibition of PI 3-kinase family members. Therefore, PI 3-kinase inhibitors may represent a new class of radiosensitizers that inhibit the repair of DNA damage.