miR-183抑制骨肉瘤细胞自噬并增强其化疗敏感性的机制研究

Chemotherapy resistance has become a serious obstacle in therapeutic effect and prognosis.of osteosarcoma patients. Our previous study showed that increased expression level of miR-183 was observed in Osteosarcoma with neoadjuvant chemotherapy compared with that in paired biopsy without neoadjuvant chemotherapy. It is likely that chemotherapy could upregulate the expression level of miR-183 in Osteosarcoma, which could boost the sensitivity to preoperative chemotherapy in Osteosarcoma patients. However, further studies are necessary to elucidate the underlying mechanisms. Our preliminary experiments showed that miR-183 expression was significantly decreased in specimens from Osteosarcoma patients that showed a poor chemoresponse compared to those that responded well to chemotherapy. We also found that upregulation of miR-183 enhances chemosensitivity of Osteosarcoma cells in vitro and overexpression of miR 183 blocks anticancer drug induced autophagy in Osteosarcoma cells. Further studies showed that miR-183 downregulates ATG5-induced autophagy in osteosarcoma cells. The study on osteosarcoma models of nude mice showed that inhibition of autophagy could increase Osteosarcoma cells death, which suggest that inhibition of autophagy maybe enhance chemosensitivity of Osteosarcoma cells. Thus, we proposed new mechanism of miR-183 enhancing chemosensitivity of Osteosarcoma cells, that is: blocked ATG5-mediated autophagy by miR-183 enhances Osteosarcoma cell chemosensitivity. This project aims to further obtain reliable evidences of miR-183 inhibits autophagy via targeting ATG5 and enhance the chemosensitivity of in vitro and in orthotopic osteosarcoma nude mice model. And the correlation between miR-183 expression and autophagy will be verified in human clinical Osteosarcoma tissues. This project will be expected to elucidate the regulation and mechanism of miR-183 enhance chemosensitivity of Osteosarcoma cells, in order to provide more sufficient scientific basis for miR-183 as a new target in chemotherapy resistance of clinical Osteosarcoma patients.

化疗耐药已成为严重影响骨肉瘤患者治疗效果和预后的瓶颈。申请人以往研究表明：新辅助化疗后骨肉瘤组织中miR-183的表达明显增高，提示miR-183可能与骨肉瘤化疗有关，但其作用机制尚不明确。预实验表明：新辅助化疗后，对化疗反应好的组织miR-183表达明显高于化疗反应差者；裸鼠皮下骨肉瘤中的研究提示：抑制自噬能增强骨肉瘤的化疗敏感性；miR-183能够抑制骨肉瘤细胞自噬且增强其化疗敏感性，并证实miR-183的靶基因ATG5。由此，申请人提出miR-183增强骨肉瘤化疗敏感性的新机制，即miR-183靶向ATG5抑制自噬，进而增强骨肉瘤的化疗敏感性。本项目拟进一步在体外及裸鼠原位骨肉瘤模型中获得miR-183靶向ATG5抑制骨肉瘤自噬并增强化疗敏感性的可靠证据。本项目将阐明miR-183增强骨肉瘤化疗敏感性的作用及机制，为miR-183作为临床骨肉瘤化疗耐药的新靶点提供充分的科学依据。

（一）骨肉瘤是好发于青少年最常见的骨恶性肿瘤。化疗耐药是骨肉瘤患者治疗效果差的原因之一。本项目证实骨肉瘤组织及细胞中miR-183的表达与骨肉瘤细胞对化疗反应呈正相关：化疗反应好的组织miR-183表达明显高于化疗反应差者。miR183能够抑制骨肉瘤细胞的自噬，并能够抑制ATG5增强骨肉瘤细胞对化疗药物的敏感性。在临床骨肉瘤标本中证实了miR-183表达与骨肉瘤组织自噬的相关性。已取得了阶段性的可喜成果。目前，正在构建裸鼠骨肉瘤原位移植瘤模型，尝试在动物体内验证miR-183通过阻止化疗诱导的细胞自噬从而增强骨肉瘤细胞的化疗敏感性。以期为miR-183在临床骨肉瘤化疗中开发相应的治疗策略提供理论依据。.（二）在课题执行期间，我们发现了一例罕见的良性骨肿瘤，即：骨软骨脂肪瘤。该肿瘤于2006年首次报道，迄今仅有约10例报道。我们对该肿瘤的临床表现，影像学，肉眼所见及镜下所见进行了详细阐述，并对已发表文献进行了简单的综述。该成果已经发表在SCI收录期刊International Journal of Clinical Pathology，为病理学家提供诊断及鉴别诊断的依据。.（三）该项目经费对BAG-3通过上调β-Catenin的表达进而促进软骨肉瘤的进展的小部分研究进行了资助，该研究成果已经发表在SCI收录期刊Molecular Medicine Reports。