Precision Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
Department of Geriatrics, Hematology & Oncology Ward, Guangzhou First People's Hospital, School of Medicine, South China University of Technology, Guangzhou, GuangDong, 510180, People's Republic of China.
Cell Death Dis. 2020 Feb 5;11(2):94. doi: 10.1038/s41419-020-2294-6.
Adult T-cell leukemia/lymphoma (ATLL) is a malignancy of mature T cells associated with chronic infection by human T-cell lymphotropic virus type-1 (HTLV-1). ATLL patients with aggressive subtypes have dismal outcomes. We demonstrate that ATLL cells co-opt an early checkpoint within the tumor necrosis factor receptor 1 (TNFR1) pathway, resulting in survival advantage. This early checkpoint revolves around an interaction between the deubiquitinase CYLD and its target RIPK1. The status of RIPK1 K63-ubiquitination determines cell fate by creating either a prosurvival signal (ubiquitinated RIPK1) or a death signal (deubiquitinated RIPK1). In primary ATLL samples and in cell line models, an increased baseline level of CYLD phosphorylation was observed. We therefore tested the hypothesis that this modification of CYLD, which has been reported to inhibit its deubiquitinating function, leads to increased RIPK1 ubiquitination and thus provides a prosurvival signal to ATLL cells. CYLD phosphorylation can be pharmacologically reversed by IKK inhibitors, specifically by TBK1/IKKε and IKKβ inhibitors (MRT67307 and TPCA). Both of the IKK sub-families can phosphorylate CYLD, and the combination of MRT67307 and TPCA have a marked effect in reducing CYLD phosphorylation and triggering cell death. ATLL cells overexpressing a kinase-inactive TBK1 (TBK1-K38A) demonstrate lower CYLD phosphorylation and subsequently reduced proliferation. IKK blockade reactivates CYLD, as evidenced by the reduction in RIPK1 ubiquitination, which leads to the association of RIPK1 with the death-inducing signaling complex (DISC) to trigger cell death. In the absence of CYLD, RIPK1 ubiquitination remains elevated following IKK blockade and it does not associate with the DISC. SMAC mimetics can similarly disrupt CYLD phosphorylation and lead to ATLL cell death through reduction of RIPK1 ubiquitination, which is CYLD dependent. These results identify CYLD as a crucial regulator of ATLL survival and point to its role as a potential novel target for pharmacologic modification in this disease.
成人 T 细胞白血病/淋巴瘤（ATLL）是一种与人类 T 细胞嗜淋巴细胞病毒 1（HTLV-1）慢性感染相关的成熟 T 细胞恶性肿瘤。具有侵袭性亚型的 ATLL 患者预后不良。我们证明，ATLL 细胞利用肿瘤坏死因子受体 1（TNFR1）途径中的早期检查点，从而获得生存优势。这个早期检查点围绕着去泛素化酶 CYLD 与其靶标 RIPK1 之间的相互作用。RIPK1 K63-泛素化的状态通过创建生存信号（泛素化的 RIPK1）或死亡信号（去泛素化的 RIPK1）来决定细胞命运。在原发性 ATLL 样本和细胞系模型中，观察到 CYLD 磷酸化的基线水平增加。因此，我们假设这种 CYLD 的修饰（据报道会抑制其去泛素化功能）导致 RIPK1 泛素化增加，从而为 ATLL 细胞提供生存信号。通过 IKK 抑制剂，特别是通过 TBK1/IKKε 和 IKKβ 抑制剂（MRT67307 和 TPCA）可以逆转 CYLD 的磷酸化。两个 IKK 亚家族都可以磷酸化 CYLD，MRT67307 和 TPCA 的组合在降低 CYLD 磷酸化和触发细胞死亡方面具有显著效果。过表达激酶失活 TBK1（TBK1-K38A）的 ATLL 细胞表现出较低的 CYLD 磷酸化，随后增殖减少。IKK 阻断可重新激活 CYLD，如 RIPK1 泛素化减少所证明的那样，这导致 RIPK1 与诱导死亡信号复合物（DISC）结合，从而触发细胞死亡。在没有 CYLD 的情况下，IKK 阻断后 RIPK1 泛素化仍然升高，并且它不与 DISC 结合。SMAC 模拟物也可以通过减少 RIPK1 泛素化类似地破坏 CYLD 磷酸化并导致 ATLL 细胞死亡，这是 CYLD 依赖性的。这些结果表明 CYLD 是 ATLL 存活的关键调节剂，并指出其作为该疾病药物修饰的潜在新靶标。
