NLK的表达调控在Smad4介导非小细胞肺癌转移中的作用

Epithelial-mesenchymal transition (EMT), mediated by a variety of oncogenic signaling pathways, such as TGF-β/Smads signaling, was regarded as a key molecular mechanism underlying non-small cell lung cancer(NSCLC) metastasis. In the present study, we found that Nemo-like kinase(NLK)-mediated Smad4 phosphorylation could promote the nuclear export of Smad4 and prevent the hypo-activation of TGF-β signaling. Besides, the expression of NLK was negtively correlated with lymph node metastasis, whereas microRNA-221 (miR-221) could repress the level of cellular NLK. Based on these findings, we aim to analyze the precise mechanism of miR-221-mediated down-regulation of NLK. Furthermore, the role of miR-221-induced down-regulation of NLK in the regulation of Smad4 activity and TGF-β-induced EMT will be evaluated. Finally, we will investigate the association between the expression of miR-221 and NLK with the formation of EMT in nude mouse model. We aim to determine the influence of downregulated NLK by miR-221 in NSCLC on the expression of TGF-β targeting genes and TGF-β-mediated EMT progress. Our investigation might help clarify the molecular mechanism of NSCLC metastasis, and provide potential opportunity into NSCLC therapy.

TGF-β/Smads通路介导的上皮间质转化(EMT)被认为是引发非小细胞肺癌（NSCLC）转移的主要分子机制。本课题组前期研究首次发现Nemo样激酶（NLK）对Smad4的磷酸化可促进其出核并抑制TGF-β通路的活化，并且NSCLC组织中NLK低表达与淋巴结转移相关，而microRNA-221（miR-221）可以靶向抑制NLK的表达。在此基础上，课题组拟分析miR-221诱导NLK表达下调的明确机制，进而分析这一机制对Smad4的活性和TGF-β诱导的EMT促进作用。最后，拟在NSCLC裸鼠动物模型中研究miRNA-221、NLK的表达和EMT及转移的关联性。本研究将探讨miR-221调节的NLK表达下调，对促进TGF-β/Smad4介导的下游靶基因的转录和EMT形成的影响，研究有助于阐明NSCLC转移的分子机制，并为NSCLC的治疗提供新的途径。

肺癌是世界范围内最常见的恶性肿瘤，在癌症相关死亡原因中站第一位，大多数非小细胞肺癌（Non-small cell lung cancer，NSCLC）患者在确诊时已有淋巴结转移或远处转移，从而失去手术机会，即使早中期已手术切除的患者也易出现复发及转移，因此阐明NSCLC的转移的机制对于患者的治疗及预后有着关键的意义。对于肿瘤临界转移和上皮-间质转化（epithelial-mesenchymal transition，EMT）途径仍知之甚少。EMT在NSCLC的发生发展中起重要作用。在本研究中，我们发现NLK表达与NSCLC患者的肿瘤进展和预后不良有关。基于RNA测序的研究表明，NLK可能通过EMT调节细胞转移。NLK在NSCLC细胞系中的下调显著降低了NSCLC细胞系的转移特性，而过表达NLK则增强了NSCLC细胞系的转移潜能。Smad4通过直接结合NLK启动子区促进NLK的转录。同时，Smad4能显著增加NSCLC细胞的转移和EMT形成。值得注意的是，NLK的过度表达可以逆转Smad4对EMT形成的下调。临床研究还表明，Smad4和NLK在NSCLC组织中的表达水平呈正相关。因此，Smad4通过上调NLK促进细胞转移，提示smad4/NLK轴可作为患者预后的指标。本研究能拓展对NSCLC的侵袭及转移分子机制的认识，为患者术后复发及转移提供新的理论依据和实验基础，为个体化治疗高侵袭性NSCLC提供新的思路。