Nakayama H, Ishimaru F, Avitahl N, Sezaki N, Fujii N, Nakase K, Ninomiya Y, Harashima A, Minowada J, Tsuchiyama J, Imajoh K, Tsubota T, Fukuda S, Sezaki T, Kojima K, Hara M, Takimoto H, Yorimitsu S, Takahashi I, Miyata A, Taniguchi S, Tokunaga Y, Gondo H, Niho Y, Harada M
Department of Medicine, University of Okayama, Japan.
Cancer Res. 1999 Aug 15;59(16):3931-4.
Gene targeting studies in mice have shown that the lack of Ikaros activity leads to T-cell hyperproliferation and T-cell neoplasia, establishing the Ikaros gene as a tumor suppressor gene in mice. This prompted us to investigate whether mutations in Ikaros play a role in human hematological malignancies. Reverse transcription-PCR was used to determine the relative expression levels of Ikaros isoforms in a panel of human leukemia/lymphoma cell lines and human bone marrow samples from patients with hematological malignancies. Among the cell lines examined, only BV-173, which was derived from a chronic myelogenous leukemia (CML) patient in lymphoid blast crisis, overexpressed the dominant-negative isoform, Ik-6. In 9 of 17 samples of patients in blast crisis of CML, Ikaros activity had been reduced either by drastically reducing mRNA expression (4 of 17) or by overexpressing the dominant-negative isoform Ik-6 (5 of 17). Significantly, expression of Ikaros isoforms seemed normal in chronic phase CML patients and patients with other hematological malignancies. In some cases, overexpression of the dominant-negative Ik-6 protein was confirmed by Western blot analysis, and Southern blot analysis indicated that decreases in Ikaros activity correlated with a mutation in the Ikaros locus. In summary, these findings suggest that a reduction of Ikaros activity may be an important step in the development of blast crisis in CML and provide further evidence that mutations that alter Ikaros expression may contribute to human hematological malignancies.
对小鼠的基因靶向研究表明，缺乏Ikaros活性会导致T细胞过度增殖和T细胞肿瘤形成，从而确立了Ikaros基因为小鼠中的肿瘤抑制基因。这促使我们研究Ikaros突变是否在人类血液系统恶性肿瘤中起作用。采用逆转录聚合酶链反应（RT-PCR）来测定一组人类白血病/淋巴瘤细胞系以及血液系统恶性肿瘤患者的人类骨髓样本中Ikaros亚型的相对表达水平。在所检测的细胞系中，只有源自一名处于淋巴细胞母细胞危象的慢性粒细胞白血病（CML）患者的BV-173细胞系过表达显性负性亚型Ik-6。在17例CML母细胞危象患者的样本中，有9例Ikaros活性降低，要么是通过大幅降低mRNA表达（17例中的4例），要么是通过过表达显性负性亚型Ik-6（17例中的5例）。值得注意的是，Ikaros亚型的表达在慢性期CML患者和其他血液系统恶性肿瘤患者中似乎正常。在某些情况下，通过蛋白质印迹分析证实了显性负性Ik-6蛋白的过表达，而Southern印迹分析表明Ikaros活性的降低与Ikaros基因座的突变相关。总之，这些发现提示Ikaros活性的降低可能是CML母细胞危象发生发展中的一个重要步骤，并进一步证明改变Ikaros表达的突变可能与人类血液系统恶性肿瘤有关。
