Hippo/YAP信号通路在骨肉瘤耐药过程中的功能和机制的研究

Drug resistance and metastasis are the two most important mechanisms responsible for the failure of current therapeutic treatments in osteosarcoma. We and others had reported that Hippo/YAP signaling pathway is over-expressed and activated in a serial of different type tumors and it has been also shown highly related with drug resistance in several kinds of tumors (Oncogene, 2013). However, it remains largely unknown whether the activation of Hippo/YAP signaling pathway contributes to the drug resistance of osteosarcoma. Our primary data indicated that YAP is over-expressed in the clinic drug-resistant osteosarcoma specimens. Both overexpression and knockdown of YAP interfere with the apoptosis of osteosarcoma cells induced by Cisplatin (CDDP) treatment. Based on these observations, we plan to further determine the function of Hippo/YAP signaling pathway in drug resistance of osteosarcoma both in cell lines and clinical specimens, to identify the key target genes involved in Hippo/YAP signaling pathway underlying the drug resistance of osteosarcoma. Finally, we also aim to elucidate the function and molecular mechanisms of Hippo/YAP signaling in drug resistance of osteosarcoma both in vitro and in vivo. In summary, we plan to explore the molecular mechanism underlying drug resistance of osteosarcoma with the implication of a noval theraputic avenue for osteosarcoma treatment.

骨肉瘤是骨科最主要的恶性肿瘤，致死致畸率极高，化疗耐药是骨肉瘤治疗效果不佳的主要原因。我们和其他已报道Hippo/YAP信号通路在很多肿瘤上发现存在过表达和激活，且参与多种肿瘤的耐药（Oncogene，2013），但其在骨肉瘤耐药过程中的功能和机制尚不明确。我们前期的工作基础表明Hippo/YAP信号通路的核心蛋白YAP在耐药型骨肉瘤标本上呈现过表达，细胞上过表达或敲低明显影响抗肿瘤药物顺铂诱导骨肉瘤细胞的凋亡。基于此，我们拟采用细胞生物学技术和信号转导研究的手段，结合细胞和动物模型以及临床骨肉瘤标本，对Hippo/YAP信号通路在骨肉瘤耐药发生中的作用进行深入的研究,鉴定和筛选Hippo/YAP通路在骨肉瘤耐药发生过程中调控的关键下游基因，并对其功能和机理在体内和体外的进行验证，旨在阐明Hippo/YAP信号通路在骨肉瘤耐药产生中的作用和分子机制,为临床骨肉瘤的药物治疗提供理论依据。

骨肉瘤是儿童和青少年中最常见的骨恶性肿瘤，甲氨蝶呤和多柔比星是治疗骨肉瘤最常用的药物，而对此类药物的化疗抵抗是骨肉瘤患者存活率较低的主要原因，目前对于化疗耐药的关键机制尚无定论。我们的项目研究发现在两种骨肉瘤细胞系MG63和U20S细胞中，化疗药甲氨蝶呤和多柔比显著诱导Hippo通路关键蛋白MST1的降解，并进而抑制Hippo通路关键蛋白LATS1/2的蛋白水平降低。在甲氨蝶呤和多柔比的作用下，降低的MST1和LATS1/2蛋白水平促进了Hippo通路下游核心组分蛋白YAP的活化，其具体表现为降低的YAP S127位点磷酸化水平和增加的细胞核定位。 在功能上，YAP蛋白的过表达则表现出显著的促进骨肉瘤细胞的增殖，以及在MG63细胞中抵抗甲氨蝶呤和多柔比星诱导的细胞凋亡；反之，YAP蛋白的敲低则表现出显著的抑制骨肉瘤细胞的增殖，以及在MG63细胞中促进甲氨蝶呤和多柔比星诱导的细胞凋亡。以上实验说明Hippo通路核心蛋白，尤其是YAP，在骨肉瘤细胞化疗抵抗中的重要作用，为临床上骨肉瘤的化疗抵抗病理诊断以及干预提供靶点。