Analysis of Molecular Mechanism of Blastic Crisis in Chronic Myelocytic Leukemia

Evi-1是一种转化基因，最初在小鼠白血病逆转录病毒的共同整合位点发现，并在人类染色体3q26中定位。它在逆转录病毒诱导的小鼠髓性白血病以及3q26异常的人类髓性白血病中过表达，因此被认为是人类和小鼠白血病发生的原因。本研究通过northern blot检测Evi-1基因在慢性髓细胞白血病（chronic myelocytic leukemia， CML）成母细胞转化过程中的可能参与，并比较其在日本和美国患者中的表达频率。在48%的日本患者和40%的美国患者中检测到Evi-1基因的表达。我们的研究结果表明，即使没有3q26异常，Evi-1基因的表达增加可能在人类白血病的发展中发挥重要作用，特别是在慢性粒细胞白血病从慢性期发展到母细胞危象的过程中。现在很明显，细胞周期机制具有多种负向调节细胞周期进程的元素。然而，在这些细胞周期控制的负调节因子中，只有4种被证明作为肿瘤抑制因子持续参与人类癌症的发展：Rb（视网膜母细胞瘤易感性蛋白），p53，以及最近发现的两种周期蛋白依赖性激酶抑制剂p16INK4A/MTS1和p15INK4B/MTS2。由于在细胞周期机制中这些负调节因子之间存在功能上的相互关系，因此研究这些肿瘤抑制因子在CML成母转化中的多重失活是特别有趣的。为了解决这一问题，我们通过Southern blot和PCR-SSCP分析检测了这四个基因在CML胚性危象患者中的失活情况。western blot分析Rb蛋白表达。p16INK4A基因在日本和美国的纯合缺失率分别为9%和15%。日本和美国分别有27%和20%的患者p53基因突变，18%和14%的患者RB蛋白失活。这些结果表明，这些肿瘤抑制因子在CML成细胞转化过程中的失活频率没有显著差异。少

Evi-1 is a transforming gene originally identified in a common integration site of murine leukemia retrovirus and mapped in human chromosome 3q26. It is overexpressed in retrovirus induced murine myeloid leukemias as well as human myeloid leukemias with 3q26 abnormalities, and thus thought to be responsible for both human and murine leukemogenesis. In this study, a possible involvement of the Evi-1 gene in blastic transformation of chronic myelocytic leukemia (CML) was examined by northern blot analysis, and the frequencies of its expression were compared between Japanese patients and American ones. Expression of the Evi-1 gene was detected in 48% of Japanese patients and 40% of American ones. Our results suggest that increased expression of the Evi-1 gene may play an important role in development of human leukemias, especially in progression from chronic phase to blastic crisis of CML even without 3q26 abnormalities.It is now evident that the cell cycle machinery has a variety of elem … More ents negatively regulating cell cycle progression. Among these negative regulators in cell cycle control, however, only 4 have been shown to be consistently involved in development of human cancers as tumor suppressors : Rb (Retinoblastoma susceptibility protein), p53, and recently identified two cyclin-dependent kinase inhibitors, p16INK4A/MTS1 and p15INK4B/MTS2. Because there are functional interrelations among these negative regulators in the cell cycle machinery, it is particularly interesting to investigate the multiplicity of inactivations of these tumor suppressors in blastic transformation of CML.In order to address this point, we examined inactivations of these four genes in patients with blastic crisis of CML by Southern blot and PCR-SSCP analyzes. We also analyzed Rb protein expression by western blot analysis. The p16INK4A was homozygously deleted in 9% and 15% in Japanese patients and American ones. The p53 gene was mutated in 27% and 20%, and the RB protein was inactivated in 18% and 14% in Japanese patients and American ones, respectively. These results suggest that there are no significant differences in inactivation frequences of these tumor suppressors in blastic transformation of CML. Less