CXCR4/miRNA在高危MDS/AML骨髓微环境介导的细胞生长和耐药中的作用及机制研究

High-risk myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) are diseases with fatal outcome. The majorities of patients are older, and succumb to the emergence of chemoresistance. As such, novel non-cross resistant therapeutic modalities capable of increasing the initial response rate and, more importantly, able of maintaining these responses are greatly needed. Mounting evidence suggests that dynamic interactions between the leukemia cell and its microenvironment bone marrow play a critical role in MDS/AML development and response to therapy. We propose that the bone marrow stromal cells protect leukemia cells from drug-induced cell death and promote MDS/AML aggressive progression through CXCR4/SDF-1/miRNA Axis-mediated genetic and epigenetic modulation. In support of our proposal, we capitalized on our previous experience to elucidate the genetic and epigenetic coordinated mechanisms of microenvironment-mediated drug resistance and progression in MDS/AML. (1) We demonstrated significant higher CXCR4 expression, associated higher anti-apoptotic feature, higher VEGF and angiogenesis in high risk MDS and AML.(2) We revealed significant activation of STAT3 and associated higher anti-apoptosis in high risk MDS and AML.(3) We recently found that stroma-mediated activation of c-Myc, c-Myc-regulated miRNA, which are associated with SDF-1/CXCR4 up-regulation and STAT3 activation in MDS/AML microenvironment and is implicated in cell proliferation, and stromal mediated drug resistance and survival. (This part of work was supported by a previous NSFC grant). Taken together, our studies provide the rationale to pursue an in-depth evaluation of the role of CXCR4/miRNA axis in the pathogenesis of high-risk MDS/AML. The following specific aims are therefore proposed: Aim 1 ：to determine the contribution of CXCR4 in stroma-mediated drug resistance and c-Myc and STAT3 activation. Aim 2 ：To investigate the contribution of c-Myc and STAT3 in stroma-mediated drug resistance and leukemia cell growth. Aim 3: To define the functional mechanism of miRNAs in CXCR4 and stroma-mediated c-Myc and STAT3 activation. The proposal builds on the following existing strengths: (a) enough MDS/AML cases, and a large repository of well-preserved bone marrow samples, (b) an established co-culture model, cell lines and a strong team background for microenvironment study and miRNA regulation and function, and (c) an already established and ongoing collaboration and publications with Dr. Jianguo Tao's Laboratory, Moffitt Cancer Center, USA and finally (d) due to the previously NSFC-supported related grant, we have done enormous work and published more than ten peer reviewed papers. Through capitalization of these advantages and close multi-disciplinary collaboration, we ultimately will enhance our understanding about molecular determinants in MDS/AML and improve therapy of MDS/AML.

高危骨髓增生异常综合征（MDS)/急性髓细胞白血病(AML)是严重威胁人类健康的恶性疾病，预后差，对化疗不敏感。白血病细胞和骨髓微环境之间的相互作用对该病的耐药起关键作用。受上一项国家自然基金资助，我们发现在高危MDS/AML中CXCR4 (CXCR4被证实介导肿瘤细胞和骨髓微环境之间的相互作用)显著高表达，与增高的抗凋亡活性，STAT3的活化程度呈正相关；白血病细胞和骨髓基质细胞的粘附可诱导CXCR4表达的上调，活化STAT3和重要的癌基因c-Myc及一系列miRNA的异常表达。基于此，我们将深入探索CXCR4/miRNA在MDS/AML发病中的作用，明确CXCR4, STAT3，c-Myc活化及前期发现的异常表达的miRNA对耐药和细胞生长的影响。鉴于前期工作和业已开展的国际合作等优势，本立项会以创新性的思路和方法深入探索MDS/AML的发病机制并提出新的治疗策略。

骨髓增生异常综合征( myelodysplastic syndromes, MDS)是一组起源于造血干细胞的恶性克隆性疾病，近年来在我国发病率呈持续增长趋势，尤其是在50岁以上的人群，部分MDS，特别是高危MDS最终转化为急性髓细胞白血病(Acute Myeloid Leukemia，AML)。本课题就CXCR4/miRNA在高危MDS/AML骨髓微环境介导的细胞生长和耐药中的作用及机制进行了研究, 通过流式细胞术检测CXCR4膜蛋白的表达,发现高危组MDS患者CD34+细胞CXCR4的表达及对骨髓基质细胞的迁移率均明显高于低危组，且迁移率随CXCR4表达量的增加而升高，SDF-1及其受体CXCR4在MDS发病中发挥作用； AML与骨髓基质细胞粘附后，CXCR4的表达显著增高，阻断CXCR4可提高AML细胞对米托蒽醌诱导的凋亡，从而克服耐药；AML细胞与骨髓基质细胞共培养可导致c-Myc蛋白表达的上调，干扰c-Myc表达后可诱导AML细胞的凋亡；AML细胞与骨髓基质细胞共培养后，与CXCR4，c-Myc调控相关的miRNA的表达也发生改变;miR-494通过下调AML细胞原癌基因c-Myc在MSC对AML的保护中发挥着重要作用，miR-494可作为潜在的治疗目标。本课题从肿瘤微环境和表观遗传调控等新的研究视角探索MDS/AML的分子机制，提出新的治疗思路.

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