跨膜型TNF-α诱导白血病细胞NF-κB组成性活化的分子机制及其在耐药中的作用

Our previous study demonstrated that transmembrane TNF-α（ tmTNF-α）expressed in leukemia cells constitutively activates both canonical and noncanonical NF-κB pathways, and thus induces chemoresistance. We used a home-made monoclonal antibody against tmTNF-α to do immunoprecipitation and found that tmTNF-α recruited by itself TRAF1 and NIK containing noncanonical NF-κB signal molecules to form a signal complex. However, how does the tmTNF-α signalsome activate canonical and noncanonical NF-κB pathways is not clear. The present project aims to clarify tmTNF-α mediated signal transduction to activate canonical and noncanonical NF-κB pathways, and to explore the molecule mechanisms underlying chemoresistance of leukemia cells induced by tmTNF-α-mediated activation of canonical and noncanonical NF-κB pathways. In addition, whether targeting tmTNF-α signaling could increase sensitivity of leukemia cells to chemotherapy in vitro and in vivo will be also studied. The results of this study would not only uncover a novel mechanism by which NF-κB can be constitutively activated in leukemia cells and elucidate tmTNF-α mediated signal transduction to activate NF-κB, but also provide a novel target for and a new clue to blocking constitutive activation of NF-κB for anti-leukemia therapy.

我们前期研究证实白血病细胞高表达tmTNF-α可组成性活化NF-κB经典和非经典途径，导致耐药。我们用自己制备的单克隆抗体首次发现tmTNF-α本身可与TRAF1和NIK等NF-κB非经典途径的信号分子形成复合物。然而，tmTNF-α信号复合物如何激活NF-κB经典与非经典途径尚不清楚。本项目拟研究并阐明 ① tmTNF-α导致白血病细胞组成性活化NF-κB经典途与非经典途径的信号通路；② tmTNF-α激活这2条NF-κB的信号通路分别导致耐药的分子机制；③ 干扰tmTNF-α信号通路，能否提高白血病细胞对化疗的敏感性。本研究不但揭示了白血病细胞NF-κB持续性活化的新机制，阐明tmTNF-α活化NF-κB经典与非经典途径的信号转导与通路，而且还为阻断白血病细胞NF-κB组成性活化提供新的治疗靶点与线索。

我们前期工作证实白血病细胞高表达tmTNF-α可组成性活化NF-κB经典和非经典途径，导致耐药。本研究进一步阐明tmTNF-α反向信号激活NF-κB非经典途径的信号转导通路，即tmTNF-α胞浆段脱磷酸化后，结合TRAF1的锌指结构域，TRAF1通过其TRAF结构域C端与NIK结合，N端与IKKα结合，促进p100被剪切成p52入核，导致靶基因表达。此外，还证实tmTNF-α反向信号通过NIK/IKKα依赖性途径以及Akt途径激活NF-κB经典途径。tmTNF-α反向信号通过组成性激活NF-κB信号通路抑制白血病细胞对sTNF-α以及阿霉素诱导凋亡的敏感性。抑制tmTNF-α脱磷酸化，阻断其反向信号可促进白血病细胞对凋亡的敏感性。根据上述结果，我们将TRAF1结合tmTNF-α的结构域做成TRAF1结合肽，可竞争性抑制tmTNF-α募集完整TRAF1，阻断tmTNF-α反向信号，抑制NF-κB，进而提高白血病细胞对DOX的敏感性。本研究结果不但阐明tmTNF-α反向信号转导通路，且为临床精准治疗白血病提供了新的靶点和线索。