Department of Neurochemistry, Stockholm University, 10691 Stockholm, Sweden.
J Neurooncol. 2012 Sep;109(3):503-12. doi: 10.1007/s11060-012-0932-2. Epub 2012 Jul 15.
Neuroblastoma is the most common solid extracranial cancer form in childhood with an etiology that is mostly unknown. Although tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been proposed as a promising future anticancer drug candidate, highly malignant neuroblastoma has been reported to acquire TRAIL resistance by mechanisms that are poorly understood. Here, we show by western blot analysis, and live cell imaging using anchored FRET sensors, that the resistance to TRAIL-induced apoptosis in human neuroblastoma SK-N-AS cells depends on an incomplete processing of procaspase-3, generating an immature and catalytically inactive 21 kDa fragment. We have previously shown that the naturally occurring compound curcumin can sensitize SK-N-AS cells to TRAIL. In the present study, we show that curcumin also has a similar effect on human neuroblastoma SHEP1 cells. Furthermore, we show that curcumin and TRAIL co-treatment induces complete maturation and activation of caspase-3 in both cell lines. The mechanisms behind this effect seem to be dependent on protein kinase C (PKC), since inhibition of PKC using bisindolylmaleimide XI, could also sensitize these cells to TRAIL through a similar effect on caspase-3 activation. Moreover, TRAIL co-treatment with bisindolylmaleimide XI or curcumin resulted in down-regulation of X-linked inhibitor of apoptosis protein. In conclusion, our study shows that PKC can be involved in TRAIL resistance in human neuroblastoma cells by preventing caspase-3 maturation.
神经母细胞瘤是儿童期最常见的颅外实体癌，其病因大多未知。尽管肿瘤坏死因子相关凋亡诱导配体（TRAIL）已被提议作为一种有前途的未来抗癌药物候选物，但据报道，高度恶性的神经母细胞瘤通过机制获得了对 TRAIL 的耐药性，这些机制尚不清楚。在这里，我们通过 Western blot 分析和使用固定化 FRET 传感器的活细胞成像显示，人神经母细胞瘤 SK-N-AS 细胞对 TRAIL 诱导的细胞凋亡的抗性取决于 procaspase-3 的不完全加工，产生不成熟且催化失活的 21 kDa 片段。我们之前已经表明，天然存在的化合物姜黄素可以使 SK-N-AS 细胞对 TRAIL 敏感。在本研究中，我们表明姜黄素对人神经母细胞瘤 SHEP1 细胞也有类似的作用。此外，我们表明姜黄素和 TRAIL 联合处理可诱导这两种细胞系中 caspase-3 的完全成熟和激活。这种效应的机制似乎依赖于蛋白激酶 C（PKC），因为使用双吲哚马来酰亚胺 XI 抑制 PKC，也可以通过对 caspase-3 激活的类似作用使这些细胞对 TRAIL 敏感。此外，TRAIL 与双吲哚马来酰亚胺 XI 或姜黄素联合处理导致 X 连锁凋亡抑制蛋白的下调。总之，我们的研究表明，PKC 可通过阻止 caspase-3 成熟参与人神经母细胞瘤细胞对 TRAIL 的耐药性。
