Griffith T S, Chin W A, Jackson G C, Lynch D H, Kubin M Z
Department of Immunobiology, Immunex Corp., Seattle, WA 98101, USA.
J Immunol. 1998 Sep 15;161(6):2833-40.
The observation that TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF cytokine family, induces apoptosis in a number of different tumor cell types led us to compare the tumoricidal effects of TRAIL to those of other TNF family molecules on human melanoma cells. We found that a high proportion of the melanoma cell lines tested were killed by TRAIL, whereas all the melanoma lines were resistant to the other TNF family cytokines tested. TRAIL-induced death was characterized by caspase activation and cellular protein cleavage within minutes of TRAIL addition, and death could be completely inhibited by the caspase inhibitors Ile-Glu-Thr-Asp (IETD) and Val-Ala-Asp (VAD), indicating the presence of a TRAIL receptor signaling pathway similar to that identified for Fas and TNF receptors. Specific TRAIL receptor expression was determined by RT-PCR, and the presence of mRNA encoding the "protective" TRAIL receptors did not correspond to resistance or sensitivity to TRAIL-induced apoptosis. Addition of protein synthesis inhibitors to TRAIL-resistant melanomas rendered them sensitive to TRAIL, indicating that the presence or the absence of intracellular apoptosis inhibitors may mediate resistance or sensitivity to TRAIL-mediated apoptosis. Expression of one such inhibitor, FLICE-inhibitory protein (FLIP), was highest in the TRAIL-resistant melanomas, while being low or undetectable in the TRAIL-sensitive melanomas. Furthermore, addition of actinomycin D to TRAIL-resistant melanomas resulted in decreased intracellular concentrations of FLIP, which correlated with their acquisition of TRAIL sensitivity. Collectively, our results indicate that TRAIL-induced apoptosis occurs through a caspase signaling cascade and that resistance is controlled by intracellular regulators of apoptosis.
肿瘤坏死因子（TNF）相关凋亡诱导配体（TRAIL）是TNF细胞因子家族的一员，可在多种不同肿瘤细胞类型中诱导凋亡，这一发现促使我们比较TRAIL与其他TNF家族分子对人黑色素瘤细胞的杀瘤效果。我们发现，所检测的黑色素瘤细胞系中很大一部分会被TRAIL杀死，而所有黑色素瘤系对所检测的其他TNF家族细胞因子均具有抗性。TRAIL诱导的死亡表现为在加入TRAIL后数分钟内半胱天冬酶激活和细胞蛋白裂解，并且死亡可被半胱天冬酶抑制剂异亮氨酸-谷氨酸-苏氨酸-天冬氨酸（IETD）和缬氨酸-丙氨酸-天冬氨酸（VAD）完全抑制，这表明存在一条与Fas和TNF受体所确定的类似的TRAIL受体信号通路。通过逆转录聚合酶链反应（RT-PCR）确定了特异性TRAIL受体的表达，编码“保护性”TRAIL受体的mRNA的存在与对TRAIL诱导凋亡的抗性或敏感性并不对应。向对TRAIL耐药的黑色素瘤中添加蛋白质合成抑制剂使其对TRAIL敏感，这表明细胞内凋亡抑制剂的存在与否可能介导对TRAIL介导凋亡的抗性或敏感性。一种这样的抑制剂，FLICE抑制蛋白（FLIP），在对TRAIL耐药的黑色素瘤中表达最高，而在对TRAIL敏感的黑色素瘤中表达低或无法检测到。此外，向对TRAIL耐药的黑色素瘤中添加放线菌素D导致细胞内FLIP浓度降低，这与它们获得TRAIL敏感性相关。总体而言，我们的结果表明TRAIL诱导的凋亡通过半胱天冬酶信号级联发生，并且抗性由细胞内凋亡调节因子控制。
