Ramp U, Caliskan E, Mahotka C, Krieg A, Heikaus S, Gabbert H E, Gerharz C D
Institute of Pathology, Heinrich Heine University, Moorenstr. 5, D-40225 Duesseldorf, Germany.
Br J Cancer. 2003 Jun 2;88(11):1800-7. doi: 10.1038/sj.bjc.6600984.
TNF-related apoptosis-inducing ligand (TRAIL APO-2L) is a member of the TNF family and induces apoptosis in cancer cells without affecting most non-neoplastic cells. The present investigation is focused on apoptosis induction by combined exposure to TRAIL and ionising radiation (IR) in human renal cell carcinoma (RCC) cell lines. Here, we demonstrate that all RCC cell lines coexpress TRAIL and the death-inducing receptors, TRAIL-R1 and TRAIL-R2. Exposure to TRAIL alone induced marked apoptosis in three out of eight RCC cell lines. Combined exposure to TRAIL and IR resulted in a sensitisation to TRAIL-induced apoptosis in one RCC cell line only. Enhanced apoptosis induction by TRAIL in combination with IR was paralleled by an increase in PARP cleavage and activation of executioner caspase-3, whereas caspases-6 and -7 were not involved. Moreover, exposure to TRAIL and/or IR resulted in a marked activation of initiator caspase-8, possibly augmented by the observed reduction of inhibitory c-FLIP expression. In contrast to other tumour types, activation of initiator caspase-9 was not detectable in our RCC model system after exposure to TRAIL and/or IR. This lack of caspase-9 activation might be related to an impaired 'crosstalk' with the caspase-8 pathway as suggested by the missing Bid cleavage and to the appearance of an XIAP cleavage product known to inhibit caspase-9 activation. Deficient activation of caspase-9, therefore, might contribute to the clinically known resistance of human RCC against IR and also argues against an effective combination therapy with TRAIL and IR in this tumour type.
肿瘤坏死因子相关凋亡诱导配体（TRAIL，又称APO-2L）是肿瘤坏死因子家族的一员，可诱导癌细胞凋亡，而对大多数非肿瘤细胞无影响。本研究聚焦于联合使用TRAIL和电离辐射（IR）诱导人肾细胞癌（RCC）细胞系凋亡。在此，我们证明所有RCC细胞系均共表达TRAIL以及死亡诱导受体TRAIL-R1和TRAIL-R2。单独使用TRAIL处理可诱导8个RCC细胞系中的3个出现明显凋亡。联合使用TRAIL和IR仅使1个RCC细胞系对TRAIL诱导的凋亡敏感。TRAIL与IR联合使用增强凋亡诱导作用的同时，PARP裂解增加且执行蛋白半胱天冬酶-3激活，而半胱天冬酶-6和-7未参与其中。此外，使用TRAIL和/或IR处理导致起始半胱天冬酶-8明显激活，观察到的抑制性c-FLIP表达降低可能增强了这种激活。与其他肿瘤类型不同，在我们的RCC模型系统中，使用TRAIL和/或IR处理后未检测到起始半胱天冬酶-9激活。半胱天冬酶-9缺乏激活可能与Bid裂解缺失所提示的与半胱天冬酶-8途径的“串扰”受损以及已知可抑制半胱天冬酶-9激活的XIAP裂解产物的出现有关。因此，半胱天冬酶-9激活不足可能导致临床上已知的人RCC对IR的耐药性，也表明在这种肿瘤类型中TRAIL与IR联合治疗无效。
