Insertional mutagenesis combined with acquired somatic mutations causes leukemogenesis following gene therapy of SCID-X1 patients

X-linked SCID (SCID-X1) is amenable to correction by gene therapy using conventional gammaretroviral vectors. Here, we describe the occurrence of clonal T cell acute lymphoblastic leukemia (T-ALL) promoted by insertional mutagenesis in a completed gene therapy trial of 10 SCID-X1 patients. Integration of the vector in an antisense orientation 35 kb upstream of the protooncogene LIM domain only 2 (LMO2) caused overexpression of LMO2 in the leukemic clone. However, leukemogenesis was likely precipitated by the acquisition of other genetic abnormalities unrelated to vector insertion, including a gain-of-function mutation in NOTCH1, deletion of the tumor suppressor gene locus cyclin-dependent kinase 2A (CDKN2A), and translocation of the TCR-β region to the STIL-TAL1 locus. These findings highlight a general toxicity of endogenous gammaretroviral enhancer elements and also identify a combinatorial process during leukemic evolution that will be important for risk stratification and for future protocol design.     

血管内皮生长因子对梗阻性肾病中肾小管周围毛细血管的调节作用

目的:观察刚断乳雄性SD大鼠单侧输尿管完全梗阻模型中血管内皮生长因子对肾小管周围毛细血管形态学变化的调节作用,探讨血管内皮生长因子在肾病进展中的生物活性作用。方法:实验于2005-03/2006-05在苏州大学儿科研究所完成。①实验材料:30只清洁级刚断乳雄性SD大鼠,体质量50～70g。②实验过程:结扎SD大鼠左侧输尿管建立单侧输尿管完全梗阻模型。于术后0,1,7,14,28d,分别随机选择6只模型大鼠,收获肾脏标本。③实验评估:采用苏木精-伊红染色观察肾积水的严重程度;Masson染色观察肾小管间质纤维化程度;PAS染色观察肾小管萎缩程度;免疫组织化学方法检测肾小管周围毛细血管的密度和血管内皮生长因子的表达水平;原位末端标记法对肾小管周围毛细血管和肾小管上皮细胞进行原位凋亡测定;透射电镜显示超微结构变化;血管内皮生长因子蛋白的表达强度和间质纤维化程度采用Leica图像分析系统检测。结果:①梗阻第1周,肾小管上皮细胞胞浆里的血管内皮生长因子染色在局部有增强,胎肝激酶1阳性肾小管周围毛细血管数量变化不显著,肾小管上皮细胞凋亡很少见,间质纤维化轻。第2,4周,血管内皮生长因子表达逐渐下降,直至在一些肾小管内完全消失。与此同时,胎肝激酶1阳性的肾小管周围毛细血管数量减少,肾小管扩张或萎缩明显,间质纤维化严重。②电镜显示肾小管上皮细胞、肾小管周围毛细血管内皮细胞的死亡形式主要为凋亡。③原位末端标记法显示肾小管上皮细胞凋亡在第14天达到高峰,然后迅速下降。④在梗阻第2周时,原位末端标记法阳性的肾小管周围毛细血管内皮细胞数与血管内皮生长因子表达面积百分比负相关(r=-0.668,P<0.05);肾小管周围毛细血管密度与血管内皮生长因子表达面积百分比正相关(r=0.707,P<0.05),而与肾小管上皮细胞凋亡负相关(r=-0.863,P<0.01)。结论:肾小管周围毛细血管减少与肾小管上皮细胞内血管内皮生长因子的表达不足相关,并与肾小管上皮细胞凋亡相关。