Malathi Krishnamurthy, Paranjape Jayashree M, Ganapathi Ram, Silverman Robert H
Department of Cancer Biology, Lerner Research Institute, and Experimental Therapeutics Program, Taussig Cancer Center, The Cleveland Clinic Foundation, Cleveland, Ohio, USA.
Cancer Res. 2004 Dec 15;64(24):9144-51. doi: 10.1158/0008-5472.CAN-04-2226.
The hereditary prostate cancer 1 (HPC1) allele maps to the RNASEL gene encoding a protein (RNase L) implicated in the antiviral activity of interferons. To investigate the possible role of RNase L in apoptosis of prostate cancer cells, we decreased levels of RNase L by severalfold in the DU145 human prostate cancer cell line through the stable expression of a small interfering RNA (siRNA). Control cells expressed siRNA with three mismatched nucleotides to the RNase L sequence. Cells deficient in RNase L, but not the control cells, were highly resistant to apoptosis by the RNase L activator, 2',5'-oligoadenylate (2-5A). Surprisingly, the RNase L-deficient cells were also highly resistant to apoptosis by combination treatments with a topoisomerase (Topo) I inhibitor (camptothecin, topotecan, or SN-38) and tumor necrosis factor-related apoptosis-inducing ligand [TRAIL (Apo2L)]. In contrast, cells expressing siRNA to the RNase L inhibitor RLI (HP68) showed enhanced apoptosis in response to Topo I inhibitor alone or in combination with TRAIL. An inhibitor of c-Jun NH(2)-terminal kinases reduced apoptosis induced by treatment with either 2-5A or the combination of camptothecin and TRAIL, thus implicating c-Jun NH(2)-terminal kinase in the apoptotic signaling pathway. Furthermore, prostate cancer cells were sensitive to apoptosis from the combination of 2-5A with either TRAIL or Topo I inhibitor, whereas normal prostate epithelial cells were partially resistant to apoptosis. These findings indicate that RNase L integrates and amplifies apoptotic signals generated during treatment of prostate cancer cells with 2-5A, Topo I inhibitors, and TRAIL.
遗传性前列腺癌1（HPC1）等位基因定位于RNASEL基因，该基因编码一种与干扰素抗病毒活性相关的蛋白质（核糖核酸酶L，RNase L）。为了研究RNase L在前列腺癌细胞凋亡中的可能作用，我们通过稳定表达小干扰RNA（siRNA），使DU145人前列腺癌细胞系中的RNase L水平降低了数倍。对照细胞表达的siRNA与RNase L序列有三个错配核苷酸。缺乏RNase L的细胞对RNase L激活剂2',5'-寡腺苷酸（2-5A）诱导的凋亡具有高度抗性，而对照细胞则不然。令人惊讶的是，缺乏RNase L的细胞对拓扑异构酶（Topo）I抑制剂（喜树碱、拓扑替康或SN-38）与肿瘤坏死因子相关凋亡诱导配体[TRAIL（Apo2L）]联合治疗诱导的凋亡也具有高度抗性。相反，表达针对RNase L抑制剂RLI（HP68）的siRNA的细胞对单独或与TRAIL联合使用的Topo I抑制剂诱导的凋亡反应增强。c-Jun氨基末端激酶抑制剂可降低2-5A或喜树碱与TRAIL联合治疗诱导的凋亡，从而表明c-Jun氨基末端激酶参与凋亡信号通路。此外，前列腺癌细胞对2-5A与TRAIL或Topo I抑制剂联合诱导的凋亡敏感，而正常前列腺上皮细胞对凋亡部分抗性。这些发现表明，RNase L整合并放大了在用2-5A、Topo I抑制剂和TRAIL治疗前列腺癌细胞过程中产生的凋亡信号。
