Program in Molecular Biology and Genetics, Karmanos Cancer Institute, Departments of Oncology and Pathology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
J Biol Chem. 2011 Jun 24;286(25):22384-92. doi: 10.1074/jbc.M111.239566. Epub 2011 May 11.
Cisplatin is the first-line chemotherapy for the treatment of several cancers. However, the development of cisplatin resistance represents a major clinical problem, and the mechanisms of acquired resistance are not fully understood. Here we show that degradation of the Bcl-2 homology 3-only proapoptotic protein Bim plays an important role in cisplatin resistance in ovarian cancer. Specifically, we show that treatment of ovarian cancer cells with cisplatin caused Bim phosphorylation and subsequent degradation and that its degradation is associated with cisplatin resistance. We also show that cisplatin treatment caused the activation of ERK, which correlated with Bim phosphorylation and degradation. By inhibiting ERK phosphorylation with the MEK inhibitor and knocking down ERK expression with siRNA, we show that Bim phosphorylation and degradation were blocked, which suggests that Bim is phosphorylated by ERK and that such phosphorylation is responsible for cisplatin-induced Bim degradation. We show that ERK was activated in cisplatin-resistant OV433 cells as compared with their counterpart parental OV433 cells. We also show that Bim was phosphorylated and degraded in cisplatin-resistant OV433 cells but not in the parental OV433 cells. Importantly, we show that inhibition of Bim degradation by the proteasome inhibitor MG132 sensitized resistant OV433 cells to cisplatin-induced death. Taken together, our data indicate that degradation of Bim via ERK-mediated phosphorylation can lead to cisplatin resistance. Therefore, these findings suggest that cisplatin resistance can be overcome by the combination of cisplatin and the proteasome inhibitors in ovarian cancer cells.
顺铂是治疗多种癌症的一线化疗药物。然而，顺铂耐药的发展是一个主要的临床问题，其获得性耐药机制尚不完全清楚。在这里，我们表明，Bcl-2 同源结构域 3 仅促凋亡蛋白 Bim 的降解在卵巢癌的顺铂耐药中起着重要作用。具体来说，我们表明，顺铂处理卵巢癌细胞导致 Bim 磷酸化和随后的降解，其降解与顺铂耐药相关。我们还表明，顺铂处理导致 ERK 的激活，这与 Bim 的磷酸化和降解相关。通过用 MEK 抑制剂抑制 ERK 磷酸化并用 siRNA 敲低 ERK 表达，我们表明 Bim 的磷酸化和降解被阻断，这表明 Bim 被 ERK 磷酸化，并且这种磷酸化负责顺铂诱导的 Bim 降解。我们表明，与亲本 OV433 细胞相比，顺铂耐药的 OV433 细胞中 ERK 被激活。我们还表明，在顺铂耐药的 OV433 细胞中 Bim 被磷酸化和降解，但在亲本 OV433 细胞中则没有。重要的是，我们表明，通过蛋白酶体抑制剂 MG132 抑制 Bim 降解可使耐药的 OV433 细胞对顺铂诱导的死亡敏感。总之，我们的数据表明，通过 ERK 介导的磷酸化降解 Bim 可导致顺铂耐药。因此，这些发现表明，在卵巢癌细胞中，顺铂和蛋白酶体抑制剂的联合应用可以克服顺铂耐药。
