Department of Biotechnology, College of Basic Medical Sciences, Dalian Medical University, Dalian, 116044, China.
Department of Biotechnology, College of Basic Medical Sciences, Dalian Medical University, Dalian, 116044, China.
Biomed Pharmacother. 2017 Oct;94:165-168. doi: 10.1016/j.biopha.2017.07.090. Epub 2017 Jul 29.
PTEN is a tumor suppressor gene well characterized as a phosphatase. However, more evidences demonstrate PTEN functions in DNA repair independent of its phosphatase activity, which affects the efficacy of DNA damage anti-tumoral drugs in treating cancer cells with PTEN variations. Using BT549 breast cancer cells, we studied the roles of PTEN in DNA repair and in sensitization of breast cancer cells to olaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor. Comet assay showed PTEN promoted DNA repair. PTEN-deficient BT549 cells are sensitive to olaparib, which shows the synthetic lethality between PTEN and PARP1. We expressed PTEN in BT549 cells and found PTEN-proficient BT549 cells resist to olaparib. Western blot showed that PTEN up-regulated Rad51 expression, suggesting PTEN promotes DNA repair through Rad51-dependnent homologous recombination. We used 5μM olaparib or 5μM RI-1, a Rad51 inhibitor, to treat PTEN-proficient BT549 cells respectively. The immunofluorescent analysis showed the combination of olaparib and RI-1 induced more than 4-fold of γH2AX foci than either of them. MTT assay showed 5μM RI-1 did not change the survival of PTEN-proficient BT549 cells, however, this dose of RI-1 sensitized PTEN-proficient BT549 cells to olaparib. Consequently, these results demonstrate that inhibition of Rad51 can sensitize BT549 cells with wild type PTEN to olaparib, which would contribute to using PARP inhibitors in individual treatment of breast cancer patients with PTEN variations.
PTEN 是一种肿瘤抑制基因，作为一种磷酸酶得到了很好的表征。然而，越来越多的证据表明，PTEN 在 DNA 修复中发挥作用，而不依赖其磷酸酶活性，这影响了具有 PTEN 变异的癌细胞中 DNA 损伤抗肿瘤药物的疗效。我们使用 BT549 乳腺癌细胞研究了 PTEN 在 DNA 修复中和对奥拉帕利（一种聚（ADP-核糖）聚合酶（PARP）抑制剂）增敏中的作用。彗星试验显示 PTEN 促进了 DNA 修复。PTEN 缺陷的 BT549 细胞对奥拉帕利敏感，表明 PTEN 和 PARP1 之间存在合成致死性。我们在 BT549 细胞中表达了 PTEN，发现 PTEN 阳性的 BT549 细胞对奥拉帕利耐药。Western blot 显示 PTEN 上调了 Rad51 的表达，表明 PTEN 通过 Rad51 依赖性同源重组促进 DNA 修复。我们分别用 5μM 奥拉帕利或 5μM RI-1（一种 Rad51 抑制剂）处理 PTEN 阳性的 BT549 细胞。免疫荧光分析显示，奥拉帕利和 RI-1 的联合使用诱导的 γH2AX 焦点比单独使用任何一种药物都多 4 倍以上。MTT 分析显示，5μM RI-1 不会改变 PTEN 阳性的 BT549 细胞的存活率，但该剂量的 RI-1 使 PTEN 阳性的 BT549 细胞对奥拉帕利敏感。因此，这些结果表明，抑制 Rad51 可以使具有野生型 PTEN 的 BT549 细胞对奥拉帕利增敏，这将有助于在个体治疗中使用 PARP 抑制剂治疗具有 PTEN 变异的乳腺癌患者。
