诱导自噬性死亡是治疗耐药MM细胞的重要新策略。项目组前期研究发现miR-221/222在地塞米松耐药和敏感的MM细胞系和临床标本中存在着明显差异表达，其预测靶基因中包含多个参与自噬的关键分子。前期研究还发现miR-221/222下调PI3K/Akt抑制分子PTEN的表达。最新研究证实PI3K/Akt/mTOR信号通路参与调节CSC的多种生物学特性。据此推测异常表达的miR-221/222通过抑制自噬性死亡和调节PTEN/PI3K/Akt/mTOR信号通路促进MMSC形成和扩增的双重机制介导MM耐药。本项目拟采用miRNA表达/拮抗实验结合临床资料的分析对生物信息学预测的靶基因加以验证，进而研究异常表达的miR-221/222对自噬抵抗以及MMSC形成和扩增的影响，然后通过小鼠模型进行体内实验，最终确定此miRNA在MM耐药和复发中的作用，并探讨以此miRNA为靶点联合化疗治愈MM的可行性。

Induction of autophagic cell death is an important new therapeutic strategy for drug-resistant multiple myeloma (MM). Our previous study has shown differential expression of miR-221/222 in dexamethasone-resistant and -sensitive MM cell lines, as well as in MM patient samples. The target genes of miR-221/222 as revealed by bioinformatic analysis, including ULK2, ATG2B, ATG4A and ATG12, are key molecules involved in autophagy. Moreover, our preliminary study has demonstrated that miR-221/222 inhibit the expression of PTEN, a negative regulator of PI3K/Akt signaling. Recent studies have demonstrated the regulation of CSCs (cancer stem cells) characteristics by PI3K/Akt/mTOR signaling pathway. Therefore, our hypothesis is that miR-221/222 mediates drug resistance in multiple myeloma through inhibiting autophagic cell death, as well as promoting formation and amplication of MMSCs (multiple myeloma stem cells) via PTEN/PI3K/Akt/mTOR signaling pathway. In the proposed study, we will use both overexpression and knockdown strategies to verify the target genes of miR-221/222 predicted by bioinformatics assay. Specifically, we will investigate the effect of deregulated expression of miR-221/222 on autophagic cell death, as well as formation and amplication of MMSCs. Next, the in vitro data will be evaluated in vivo using MM mouse models. Our aim is to elucidate the role of miR-221/222 in MM drug resistance and relapse. Ultimately, this proposed study will provide the rationale for the combination of miRNA-targeted treatment strategy with chemotherapy to cure MM.