DKK1/eIF2α/ATF4信号轴促进肺癌恶病质肌肉萎缩的作用及机制

Lung cancer is threatening human health in China. Lung cancer-induced muscle atrophy (LCMA) occurs in approximate 50% of patients with lung cancer. LCMA is an important cause of worsen medical conditions and causes death of patients directly. However, the pathogenesis of LCMA remains unknown. No useful approach for treating LCMA could be used in clinical work up to now. The preliminary research in this subject first indicated that the content of Dickkopf1 (DKK1) was significantly increased in the sera of the patients suffering LCMA (compared with the patients suffering lung cancer, but not LCMA). The atrophy of in vitro muscle cell could be induced by lung cancer cell cultured supernatants. Meanwhile, the eIF2α-ATF4 pathway would be activated. Inhibition of DKK1 could inactivate the eIF2α-ATF4 pathway and effectively alleviate the atrophy of muscle cell. Based on the former published data obtained by our research group, we speculate that DKK1 is highly expressed in lung cancer cell and secreted into sera. DKK1 binds to the LRP6 on the surface of muscle cell, activates eIF2α, and induces the expression of ATF4. ATF4 enhances C/EBPβ and Gadd45α gene expression and eventually leads to LCMA. We will build in vitro and vivo models, respectively. And then the recombinant expression plasmids, siRNA, inhibitors and gene knock-out mice which targeting specific molecules will be used to validate the related molecular mechanisms involved in LCMA. Our results will explore the effect and mechanism of DKK1 in LCMA. Our study will provide new drug targets for LCMA treatment and lay the theoretical foundation.

肺癌严重危害我国居民健康，约半数患者形成肺癌恶病质肌肉萎缩（LCMA）,导致患者病情恶化甚至死亡。但其发生机制不明，缺乏有效临床对策。本课题前期研究首次发现，在肺癌患者中，恶病质者血清DKK1含量明显高于非恶病质者；肺癌细胞培养上清可诱导体外肌肉细胞萎缩，激活eIF2α-ATF4通路；抑制DKK1可抑制eIF2α-ATF4通路，并有效缓解体外肌肉细胞萎缩。结合本课题组已发表数据，我们推测，肺癌细胞表达并分泌DKK1，与肌肉细胞表面的LRP6结合，激活肌肉细胞内的eIF2α，从而诱导肌肉细胞表达ATF4，进而上调ATF4的靶基因C/EBPβ和Gadd45α表达，最终导致肌肉萎缩。本课题将分别在体内和体外建立LCMA研究模型，通过使用相应表达质粒、siRNA、抑制剂和基因敲除鼠，对相关的分子机制进行探讨，阐明DDK1在LCMA中的作用，为临床治疗LCMA提供作用靶点并奠定理论基础。

本课题在研究过程中，发现Dickkopf1（简称DKK1）具有抑制肌肉细胞分化的功能，对于已经分化后的肌管细胞，DKK1能够诱导其发生萎缩。同时，本课题还对其中的相关分子机制进行探讨。文献报道，胰腺癌细胞能够分泌大量的DKK1。同时，在临床肿瘤患者中，胰腺癌患者发生的癌症恶病质所致的肌肉萎缩的概率最大。因此，本课题对胰腺癌细胞分泌的DKK1与肌肉萎缩的相关性进行探讨。结果显示，胰腺癌细胞的分泌物具有抑制肌肉细胞活性的作用。本课题已构建了过表达的DKK1的胰腺癌细胞系，将在后续实验中对相关的分子机制展开深入探讨，为临床治疗癌症恶病质所致的肌肉萎缩奠定理论基础。与此同时，本课题对对胰腺癌相关的治疗措施开展了相关研究。本课题研究发现，Riluzole，ORY1001和Furagin等药物，能显著抑制胰腺癌细胞的增殖与迁移。相关的分子机制研究显示，这些药物通过促进或抑制相关分子的表达，阻断细胞周期，促进胰腺癌细胞凋亡。相关的rescue实验也进一步证实了相应的结论。虽然这些研究为胰腺癌的治疗提供一定线索，但是相应的研究结果还需要在体内实验中进行验证。此外，本课题还对胰腺癌相关的分子病理机制展开了研究。结果发现TIGD1基因在胰腺癌组织和细胞中表达上调，并且具有促进胰腺癌细胞增殖的作用。本课题对其相关的分子机制进行的深入研究让人们对胰腺癌的致病机制有了更全面的认识。最后，本课题还对胰腺癌患者体内的胆汁酸及其亚型的变化进行了研究，发现这些变化，可能也是促进胰腺癌形成的因素，相关的机制需要进一步研究。