骨肉瘤是儿童和青少年最常见的高度恶性骨肿瘤，肺转移是患者死亡的主要原因，是目前临床上限制生存率进一步提高的“瓶颈”。肺转移是一个多步骤连续的过程，细胞在血液循环存活及在肺部成功定植是肺转移灶形成的关键，然而目前机制仍不明确。申请者在国际上最先证实了癌基因COPS3高表达促进骨肉瘤肺转移。在配对临床标本中肺转移灶COPS3表达显著高于原发灶，体外敲减COPS3可以显著抑制细胞集落形成及悬浮状态形成肉瘤细胞球的能力，体内敲减COPS3可以显著抑制裸鼠肺内成瘤率，提示其对肺转移灶的形成也起到了重要作用。本课题是延伸性研究，通过体外和体内实验进一步确定COPS3高表达维持骨肉瘤干细胞特征及抵抗失巢凋亡利于细胞在血液循环中存活的机制；转移微环境中细胞与肺基质相互作用介导侵袭性伪足形成、金属蛋白酶产生及影响自噬水平促进肺转移灶形成的机制,机制的阐明对发现新的治疗靶点具有重要意义。

Osteosarcoma (OS), the most common high-grade malignant tumor of the bone in early adolescence, tends to metastasize to lung. Pulmonary metastasis is the main cause of death, and remains the “bottleneck” to further improve the survival of patients with OS. Pulmonary metastasis is a multi-step and consecutive process. The survival of cells in the blood circulation and successful colonization in the lung are the key to form lung metastases. However, the mechanism is still unclear. The grand applicant has confirmed that overexpression of novel oncogene COPS3 was closely related to lung metastasis. The expression of COPS3 protein in lung was significantly higher than that of primary tumor in paired clinical specimens. The knockdown of COPS3 can inhibit colony formation and the ability to grow as anchorage-independent spheroid in serum free condition. And knockdown of COPS3 can significantly inhibit the number of lung tumors in nude mice, suggesting it also plays an important role in the formation of lung metastases. Based on our previous research achievements, this grant aims to reveal the mechanism of lung“colonization”. Further research will focus on the maintenance of stem-like characteristics of cells by COPS3，the resistance to anoikis in the blood circulation via in vitro and in vivo experiments. COPS3 is poised to facilitate the interaction of osteosarcoma cell with the matrix in metastatic microenvironment. The formation of invadopodia and the production of metalloproteinases modulated by COPS3 will be determined. In addition, the autophagy also play a role in colonization, which will investigated in paired samples and in vivo study. Therefore, this grant will contribute to the clarity of interaction network in metastatic microenvironment and the identification of possible therapeutic targets to break the “bottleneck”that limits the survival of lung metastasis patients.