抑癌基因SATB2及其启动子甲基化调控骨肉瘤MICs肺转移及机制研究

Osteosarcoma is the most common primary malignant bone tumor with poor prognosis.It is regarded as a differentiation disease caused by disruption of osteoblast differentiation from mesenchymal stem cells(bMSC).Pulmonary metastasis is the bottleneck to improve the survival rate of osteosarcoma and the study of metastatic mechanism of osteosarcoma is the key point to improve the general prognosis.In the preliminary NSFC project, we have established two novel syngeneic human osteosarcoma cell lines with different metastatic potential-ZOS and ZOSM. Joint methylation microarray and expression microarray were used to identify the differential genes of these two cell lines both in vitro and in vivo. We found that the highly metastatic ZOSM and tumor with lung metastasis had lower expression of SATB2, and the low expression of SATB2 is closely related to the high promoter methylation.Further research shows that SATB2 can inhibit the invasion and metastasis of osteosarcoma in vivo and in vitro. Studies have shown that SATB2 plays an important role in the osteoblast differentiation, and it is a novel marker of osteoblastic differentiation in bone and soft tissue tumours. So whether SATB2 and its promoter methylation play an important role in osteosarcoma metastasis through regulating metastasis-initiation cells(MICs)? Further research shows the demethylation drugs can increase the expression of SATB2 and promote the differentiation of osteosarcoma metastasis-initiation cells. In the meantime,SATB2 can regulate TGF-β signaling pathway negatively.The present study aims to clarify function and mechanism of SATB2 and its promoter methylation in the differentiation of osteosarcoma MICs at the level of molecular, tissue and animal model, which could provide a whole new strategy for osteosarcoma targeting therapy.

骨肉瘤是成骨细胞分化缺陷性疾病，研究肺转移机制是改善其预后的关键。在国科基项目中，我们建立了不同转移特性同源骨肉瘤细胞系ZOS和ZOSM，联合甲基化和表达谱芯片研究发现SATB2在高转移的ZOSM中低表达，且与启动子高甲基化密切相关；并且证实SATB2在骨肉瘤转移中发挥抑癌作用。研究表明SATB2在成骨细胞分化中发挥重要作用，它是预测骨软肿瘤分化程度的标记。那么SATB2及其启动子甲基化是否通过调控骨肉瘤转移起始细胞(MICs)而发挥其抑制转移作用？进一步实验显示去甲基化药物能增加SATB2的表达量并且促进骨肉瘤起始细胞分化；同时，SATB2可负向调控TGF-β信号通路。本项目拟在前期基础上，进一步深入研究SATB2及其甲基化通过TGF-β信号通路调控骨肉瘤转移性起始细胞分化的关键性作用，在细胞株、小鼠、组织及血液标本多层面验证，旨在为突破骨肉瘤肺转移的临床瓶颈，提高其整体预后带来新的启示

骨肉瘤是来源于成骨细胞的难治性恶性肿瘤，其治疗失败多归因于没能杀灭骨肉瘤肿瘤干细胞。在本项研究当中，我们发现 SATB2在骨肉瘤干细胞中高表达。SATB2的高表达与骨肉瘤不良预后相关。敲低 SATB2表达水平可降低骨肉瘤瘤球形成，肿瘤生长以及干细胞标志物的表达，还能降低小鼠体内的肿瘤生长以及化疗耐药性。N-cadherin是 SATB2下游的关键靶基因，它调控了肿瘤干细胞的特性。SATB2或者 N-cadherin 的减少均可以抑制 NF-κB 信号通路的激活，进而减少了骨肉瘤瘤球的形成以及肿瘤的增殖。利用二甲双胍抑制 N-cadherin 可以降低骨肉瘤的化疗耐药性。因此，本研究发现 SATB2在调控骨肉瘤肿瘤干细胞特性过程中的重要地位。联合运用二甲双胍与传统化疗药物治疗骨肉瘤可能是一种更好的治疗策略。