First Department of Medicine, Johannes Gutenberg University, Mainz, Germany.
Int J Oncol. 2011 Jan;38(1):121-31.
The cylindromatosis gene (CYLD) was identified as a tumor suppressor gene, which is mutated in familial cylindromatosis (Brooke-Spiegler syndrome), an autosomal-dominant predisposition to multiple tumors of the skin appendages. CYLD is a deubiquitinating enzyme acting as a negative regulator of the nuclear factor κB (NF-κB) signaling pathway by removing lysine-63-linked polyubiquitin chains from NF-κB activating proteins. In order to investigate the role of CYLD in apoptotic signaling in human hepatocellular carcinoma (HCC) cells, we first studied the expression levels of CYLD in HCC tissues. CYLD expression was lower in HCC both at protein and mRNA levels compared to the surrounding non-malignant tissue. In order to further study the role of CYLD in the apoptotic sensitivity of HCC cells, CYLD was specifically down-regulated in HCC cell lines via RNA interference. The specific down-regulation of CYLD resulted in increased resistance towards treatment with doxorubicin, 5-fluorouracil and cisplatin. In addition, the down-regulation of CYLD in HCC cells decreased the sensitivity towards tumor necrosis factor-α-induced apoptosis. The CYLD knockdown also led to the degradation of the NF-κB inhibitor, IκB-α, resulting in enhanced NF-κB activity in HCC cells. Finally, we found that CYLD expression was triggered by the multikinase inhibitor, sorafenib, by the inhibition of Raf-1, as well as by the blockage of the pro-survival kinases, MEK (U0126) and the epidermal growth factor receptor (AG1478). In summary, we show that CYLD is down-regulated in human HCC and is involved in the apoptotic resistance of HCC cells. Our data identify the reconstitution of CYLD expression as an attractive approach for overcoming resistance to treatment in HCC.
圆柱瘤病基因（CYLD）被鉴定为抑癌基因，其在家族性圆柱瘤病（Brooke-Spiegler 综合征）中发生突变，这是一种多发性皮肤附属器肿瘤的常染色体显性遗传倾向。CYLD 是一种去泛素化酶，通过从 NF-κB 激活蛋白上去除赖氨酸 63 连接的多泛素链，作为核因子 κB（NF-κB）信号通路的负调节剂。为了研究 CYLD 在人肝细胞癌（HCC）细胞凋亡信号中的作用，我们首先研究了 HCC 组织中 CYLD 的表达水平。与周围非恶性组织相比，CYLD 在 HCC 中的蛋白和 mRNA 水平均较低。为了进一步研究 CYLD 在 HCC 细胞凋亡敏感性中的作用，我们通过 RNA 干扰特异性下调 HCC 细胞系中的 CYLD。CYLD 的特异性下调导致多柔比星、5-氟尿嘧啶和顺铂治疗的耐药性增加。此外，HCC 细胞中 CYLD 的下调降低了肿瘤坏死因子-α诱导的细胞凋亡的敏感性。CYLD 敲低也导致 NF-κB 抑制剂 IκB-α的降解，从而增强 HCC 细胞中的 NF-κB 活性。最后，我们发现多激酶抑制剂索拉非尼通过抑制 Raf-1 以及阻断生存激酶 MEK（U0126）和表皮生长因子受体（AG1478）触发了 CYLD 的表达。总之，我们表明 CYLD 在人 HCC 中下调，并参与 HCC 细胞的凋亡抵抗。我们的数据确定了重建 CYLD 表达作为克服 HCC 治疗耐药性的一种有吸引力的方法。
