精准靶向AML分子标志物CD33蛋白C2-结构域的适配体偶联药物跨膜转运机制的研究

急性髓系白血病(AML)的治疗存在瓶颈，靶向治疗是突破瓶颈的重要手段。CD33分子是AML的重要靶标。靶向CD33的单抗GO是AML治疗的重大突破，但该药在安全性上存在缺陷，这与靶向结合效率低有关。核酸适配体是一种新型的靶向治疗武器。我们在前期研究中首次成功制备了精准靶向并杀伤CD33+AML细胞的适配体制剂S30-T1-Dox，但其跨膜传递机制尚不清楚。我们发现S30的结合位点为普遍表达的C2-set结构域，区别GO的V-set结构域，这是S30在结合效率上优于GO的原因，也说明它的跨膜机制与GO不同。结合前期的研究发现我们提出S30结合C2-set后使CD33分子膜内的ITIM基序的特殊位点磷酸化进而激活下游的含SH2的磷酸酶然后激活特异的内吞途径的假设，试图阐明S30-T-Dox的跨膜传递机制，为了解该适配体的治疗价值和安全性提供依据，从而为研发一种新的靶向治疗AML的药物奠定基础。

The treatment of acute myeloid leukemia (AML) remains bottleneck, target therapy is a pivotal way to break through it. CD33 molecule is an important therapy target for AML. The monoclonal antibody of CD33 Gemtuzumab Ozogamicin （GO）is a milestone for AML therapy, but it has high incidence of side effects in AML patients. Nucleic acid aptamers are a new weapon for targeted therapy. We have successfully developed an aptamer agent S30-T1-Dox that can precisely recognize and kill CD33 positive AML cells, but the mechanism of its transmembrane delivery into the cell is unknown. Our previous studies found that S30 only binds to the C2-set segment at the outer-membrane part of CD33 which is universal expressed, this is different with GO which binds to V-set. This finding can explain why S30 has higher binding efficiency than GO, on the other hand indicates the transmembrane delivery mechanism of S30 is different with GO. Based on the research findings in our previous study, we assume that S30 binds to C2-set and phosphorylates a special site of the ITIM motif of the inner-membrane part of CD33 molecular, thereby activating the downstream SH2-containing phosphatase and then activating the specific endocytosis pathway so that to elucidate S30-T-Dox's transmembrane delivery mechanism, which provides a basis for understanding the therapeutic value and safety of this aptamer agent, thereby laying the foundation for the development of a new target drug for the treatment of AML.