SIK2激活Wnt/β-catenin信号通路的机制及其在胰腺肿瘤干细胞中的功能研究

CK1 (Casein kinase 1) plays a very important role in Wnt/beta-catenin signaling pathway. However, the mechanisms for its regulation were poorly understood. In the screening of the regulator for Wnt/β-catenin signaling using the siRNA library, we found that inhibition of expression of SIK2 (Salt-induced kinase 2) down-regulated the activity of the reporter for Wnt/β-catenin signaling, the protein level of β-catenin and expression of its target genes. SIK2 was also found to directly interact with CK1α. Knocking down expression of SIK2 impaired the sphere formation and the tumorigenicity of pancreatic cancer cells. Based on these observations, we propose that SIK2 activates Wnt/β-catenin signaling and maintains the stemness of pancreatic cancer stem cells by regulating the activity of CK1α. In this project, we will apply clinical specimens, molecular biology techniques and animal models to study the regulatory role and mechanism of SIK2 on CK1α, and explore the functions of SIK2 in the maintenance of stemness for pancreatic cancer stem cells and the potential therapeutic significance of its inhibitors for pancreatic cancer.

CK1 (Casein kinase 1) 在Wnt/β-catenin 信号转导中具有非常重要功能，但其本身的调控机制不明。在siRNA文库筛选中我们发现SIK2（Salt-induced kinase 2）表达抑制降低Wnt/β-catenin 信号报告基因的活性，并伴随β-catenin蛋白水平及下游靶基因的表达下降；SIK2与CK1α相互作用；在胰腺癌细胞中干扰SIK2的表达抑制Sphere的形成和成瘤能力。籍此，我们提出：SIK2通过调控CK1α的活性激活Wnt/β-catenin 信号通路，从而维持胰腺肿瘤干细胞特性。本项目应用临床标本、分子生物学技术和动物模型，研究SIK2对CK1α的调控作用及机制，探索SIK2在胰腺肿瘤干细胞干性维持中的功能及其抑制剂对胰腺癌的潜在治疗意义。本项目的实施将揭示CK1α活性调控新机制，为Wnt/β-catenin通路抑制剂开发提供新思路。

Wnt/β-catenin 信号通路在胰腺癌的进展中发挥着重要功能，但是目前尚没有靶向该信号通路的抑制剂应用于临床。为了鉴定Wnt/β-catenin 信号通路的治疗靶点，我们从激酶文库出发，利用靶向人类720个激酶的siRNA文库进行筛选。在筛选过程中，我们发现，敲减SIK2（Salt-induced kinase 2）的表达抑制Wnt/β-catenin 信号报告基因的活性，并伴随β-catenin蛋白水平及下游靶基因的表达下降；SIK2与CK1α相互作用；在胰腺癌细胞中干扰SIK2的表达抑制Sphere的形成和成瘤能力，敲减SIK2的表达抑制胰腺癌细胞侵袭能力。SIK2在胰腺癌发生早期的ADM（Acinar cell to Ductal cell Metaplasia）阶段表达上调，与CK1α形成复合物以后共同磷酸化LRP6。SIK2对Wnt/β-catenin信号通路的调控依赖其激酶活性。在下游的生物学事件fenxi 中，我们发现SIK2通过激活Wnt/β-catenin信号通路促进IDH1的表达。本项目揭示了SIK2在胰腺肿瘤中的功能及其抑制剂对胰腺癌的潜在治疗意义，为Wnt/β-catenin通路抑制剂开发提供新思路。