γ射线诱发的小鼠急性淋巴细胞白血病中MDM_2的表达研究

Expression of MDM_2 in an acute lymphocytic leukemia mice model induced by γ-radiation

目的 观察MDM2 在γ射线诱发的小鼠淋巴细胞白血病组织细胞中的表达变化 ,探讨MDM2 在辐射致癌中的作用及可能的分子机理。方法 用γ射线照射BALB c小鼠诱发白血病发生 ,建立辐射致癌动物模型 ;分别应用Westernblot和原位杂交技术 ,从蛋白水平和mRNA水平检测小鼠胸腺和骨髓组织中MDM2 的表达情况 ;运用免疫沉淀技术 (IP)检测MDM2 蛋白的磷酸化水平 ;PCR SSCP及银染技术用于检测基因突变。结果 癌变组和辐射未癌变组胸腺细胞 骨髓细胞MDM2蛋白表达水平都高于对照组 (P <0 0 5 ) ;而癌变组和辐射未癌变组之间MDM2 蛋白水平差异无显著性 (P >0 0 5 )。γ射线照射后早期辐射组骨髓MDM2 蛋白表达水平也明显高于对照组。原位杂交结果显示 :癌变组织中MDM2 阳性反应和阳性率均明显高于对照组。在癌变组组织中发现有MDM2 磷酸化比其他组都明显升高 (P <0 0 5 )。辐射组和对照组均未检测到基因突变。结论 MDM2 可能参与γ射线诱发的小鼠淋巴细胞白血病的发生和发展过程 ,作用机理可能与过表达及高磷酸化所致活性增强有关。MDM2 的基因突变在辐射致小鼠白血病发生不起主要作用。

Objective To investigate the role of the MDM_2 in the process of carcinogenesis induced by γ-rays and its molecular mechanisms. Methods Animal model of radiation-induced leukemia was established by γ-irradiation.According to the histological and morphological results,mice tissues were divided into three groups:cancerization group,incancerization group and control group.Expression of MDM_2 protein and mRNA in thymus/bone marrow was detected with Western blot and in situ hybridization (ISH),respectively.We also examined the protein phosphorylation level of MDM_2 protein by immunoprecipitation (IP).PCR-SSCP was performed to detect gene mutation. Results A mice leukemia model was successfully established as verified by pathological findings and confirmed by transplantation test in nude mice.The protein expression in thymus/bone marrow in irradiation groups was significantly higher than that in controls ( P <0.05).But the expression level was not statistically different between the cancerization group and the incancerization group.The MDM_2 was found to be hyperphosphorylated in the cancerization group as compared with other groups.No gene mutation was detected by SSCP/silver-staining assay in the tumor samples. Conclusion MDM_2 may be involved in the development and progression of leukemia induced by γ-irradiation.The over-expression but not gene mutation may be responsible for malignant transformation induced by radiation.Phosphorylation is at least partly attributed to activation of MDM_2. ;