Kim K, Fisher M J, Xu S Q, el-Deiry W S
Howard Hughes Medical Institute, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
Clin Cancer Res. 2000 Feb;6(2):335-46.
The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL or Apo2L) is a potent inducer of death of cancer but not normal cells, which suggests its potential use as a tumor-specific antineoplastic agent. TRAIL binds to the proapoptotic death receptors DR4 and the p53-regulated proapoptotic KILLER/DR5 as well as to the decoy receptors TRID and TRUNDD. In the present studies, we identified a subgroup of TRAIL-resistant cancer cell lines characterized by low or absent basal DR4 or high expression of the caspase activation inhibitor FLIP. Four of five TRAIL-sensitive cell lines expressed high levels of DR4 mRNA and protein, whereas six of six TRAIL-resistant cell lines expressed low or undetectable levels of DR4 (chi 2; P < 0.01). FLIP expression appeared elevated in five of six (83%) TRAIL-resistant cell lines and only one of five (20%) TRAIL-sensitive cells (chi 2; P < 0.05). Two TRAIL-resistant lines that expressed DR4 contained an A-to-G alteration in the death domain encoding arginine instead of lysine at codon 441. The K441R polymorphism is present in 20% of the normal population and can inhibit DR4-mediated cell killing in a dominant-negative fashion. The expression level of KILLER/DR5, TRID, TRUNDD or TRID, and TRUNDD did not correlate with TRAIL sensitivity (P > 0.05). These results suggest that the major determinants for TRAIL sensitivity may be the expression level of DR4 and FLIP. TRAIL-resistant cells became susceptible to TRAIL-mediated apoptosis in the presence of doxorubicin. In TRAIL-sensitive cells, caspases 8, 9, and 3 were activated after TRAIL treatment, but in TRAIL-resistant cells, they were activated only by the combination of TRAIL and doxorubicin. Our results suggest: (a) evaluation of tumor DR4 and FLIP expression and host DR4 codon 441 status could be potentially useful predictors of TRAIL sensitivity, and (b) doxorubicin, in combination with TRAIL, may effectively promote caspase activation in TRAIL-resistant tumors.
肿瘤坏死因子相关凋亡诱导配体（TRAIL 或 Apo2L）是一种强效的癌症细胞而非正常细胞的死亡诱导剂，这表明其作为肿瘤特异性抗肿瘤药物的潜在用途。TRAIL 与促凋亡死亡受体 DR4 和 p53 调节的促凋亡 KILLER/DR5 以及诱饵受体 TRID 和 TRUNDD 结合。在本研究中，我们鉴定出一组对 TRAIL 耐药的癌细胞系，其特征为基础 DR4 水平低或缺失，或半胱天冬酶激活抑制剂 FLIP 高表达。五个 TRAIL 敏感细胞系中有四个表达高水平的 DR4 mRNA 和蛋白，而六个 TRAIL 耐药细胞系中有六个表达低水平或无法检测到的 DR4（卡方检验；P < 0.01）。FLIP 表达在六个 TRAIL 耐药细胞系中的五个（83%）中升高，而在五个 TRAIL 敏感细胞系中仅一个（20%）中升高（卡方检验；P < 0.05）。两个表达 DR4 的 TRAIL 耐药细胞系在死亡结构域编码精氨酸而非赖氨酸的第 441 密码子处存在 A 到 G 的改变。K441R 多态性存在于 20%的正常人群中，并且可以以显性负性方式抑制 DR4 介导的细胞杀伤。KILLER/DR5、TRID、TRUNDD 或 TRID 和 TRUNDD 的表达水平与 TRAIL 敏感性无关（P > 0.05）。这些结果表明，TRAIL 敏感性的主要决定因素可能是 DR4 和 FLIP 的表达水平。在存在阿霉素的情况下，TRAIL 耐药细胞对 TRAIL 介导的凋亡变得敏感。在 TRAIL 敏感细胞中，TRAIL 处理后半胱天冬酶 8、9 和 3 被激活，但在 TRAIL 耐药细胞中，它们仅在 TRAIL 和阿霉素联合作用下被激活。我们的结果表明：（a）评估肿瘤 DR4 和 FLIP 表达以及宿主 DR4 第 441 密码子状态可能是 TRAIL 敏感性的潜在有用预测指标，并且（b）阿霉素与 TRAIL 联合使用可能有效地促进 TRAIL 耐药肿瘤中的半胱天冬酶激活。
