EKLF (KLF1): A Potential Tumor Suppressor?

描述（申请人提供）：肿瘤抑制因子的功能失活在恶性肿瘤中起重要作用。许多肿瘤抑制因子通常与细胞周期机制相结合，并构成其精细控制机制的一部分。失去这些控制可导致无限制的增殖和分化受损，这两者都是急性髓性白血病的特征。EKLF（红系Kr¿pel Like Factor； KLF1）是一种锌指造血转录因子，对红系谱系至关重要。我们最近的研究也揭示了EKLF作为巨核生成抑制剂的意想不到的作用，这表明该转录因子在造血过程中的谱系承诺中具有新的功能。EKLF抑制细胞增殖并诱导内源性细胞周期抑制剂p21的表达。因此，我们假设人类EKLF可能在造血恶性肿瘤中发挥与肿瘤抑制因子一致的作用，本探索性提案将从两个方面评估这一想法。首先，我们将使用一种识别人类EKLF蛋白的抗体来分析人类正常和白血病组织和细胞样本中EKLF蛋白的存在/缺失，并确定其表达是否与特定的恶性亚型相关。第二步，比较正常骨髓与一些人类白血病细胞系和恶性原代细胞之间完整的人EKLF转录单元序列，看看EKLF是否在这些细胞系中发生了突变。发现的任何变体EKLF蛋白的功能测试将遵循这两个目标，也将为超出本探索性资助时间线的未来实验提供基础。成功实现本提案的目标将确定突变的EKLF/KLF1是否在白血病中发挥作用，从而提供一种新的生物标志物，并将指导未来对最临床相关样本的适用性。

DESCRIPTION (provided by applicant): Functional inactivation of tumor suppressors plays an important role in malignancy. Many tumor suppressors normally interface with the cell cycle machinery and form part of its exquisite control mechanism. Loss of these controls can lead to unrestricted proliferation and impaired differentiation, both of which are characteristic of acute myeloid leukemia. EKLF (Erythroid Kr¿ppel Like Factor; KLF1) is a zinc finger hematopoietic transcription factor that is absolutely critical for the erythroid lineage. Our recent studies have also revealed an unexpected role of EKLF as an inhibitor of megakaryopoiesis, suggesting a novel function of this transcription factor in lineage commitment during hematopoiesis. EKLF inhibits cellular proliferation and induces endogenous expression of the cell cycle inhibitor p21. As a result, we hypothesize that human EKLF may play a role in hematopoietic malignancy consistent with that of a tumor suppressor, and this exploratory proposal will evaluate this idea by two aims. In the first, we will use an antibody that recognizes human EKLF protein to analyze human normal and leukemic tissue and cell samples for the presence/absence of EKLF protein, and determine whether its expression correlates with a specific malignant subtype. In the second, the sequence of the complete human EKLF transcription unit will be compared between normal bone marrow and a number of human leukemic cell lines and malignant primary cells to see if EKLF is mutated in any of these lines. Functional tests of any variant EKLF proteins that are discovered will follow both of these aims and will also provide a basis for future experiments that extend beyond the timeline of this exploratory grant. Successful attainment of the aims in this proposal will determine whether mutated EKLF/KLF1 plays a role in leukemia, thus providing a novel biomarker, and will direct future applicability towards the most clinically relevant samples. PUBLIC HEALTH RELEVANCE: Tumor suppressors play an important role in preventing malignancy. EKLF, a critical zinc finger hematopoietic transcription factor, has antiproliferative properties consistent with that of a tumor suppressor. As a result, our test hypothesis is that EKLF is playing an unappreciated role as a tumor suppressor, and that its dysregulation can contribute or lead to human leukemia.