Expression & function of p21Cip1 in chronic leukemia

慢性粒细胞白血病起源于造血干细胞，融合蛋白p210 bcr/abl。作为一种组成性激活的酪氨酸激酶，BCR/ABL干扰许多细胞事件，包括细胞增殖和存活。在目前的建议，实验设计将解决可能的作用，细胞周期蛋白依赖性激酶抑制剂，p21 Cip 1在促进异常细胞周期和生存的BCR/ABL造血细胞。先前的研究发现p21在细胞增殖中的正性和负性作用。此外，p21还可以作为一种 抗凋亡蛋白，并已显示使转化细胞对抗癌药物具有抗性。CML特别感兴趣的是，与正常细胞相比，在BCR/ABL阳性细胞中检测到更高水平的p21蛋白。尽管p21蛋白高度不稳定，但其通过AKT介导的磷酸化而稳定，AKT是CML中激活的抗凋亡蛋白。基于这些研究，测试p21 Cip 1是否可能有助于在CML中观察到的增强的细胞增殖和存活是有趣的。RNA和蛋白质的研究将探讨p21 Cip 1在正常和BCR/ABL造血细胞中的调节机制。用STI 571治疗将描述BCR/ABL酪氨酸激酶活性在p21调节中的贡献作用。逆转录病毒导入BCR/ABL到来自p21野生型、半合子和缺失型小鼠的造血祖细胞中将决定p21在BCR/ABL转化中的作用。这些细胞的同基因移植将评估不同p21水平对体内CML发作和进展的影响。

Chronic myeloid leukemia originates from hematopoietic stem cells harboring the fusion protein, p210bcr/abl. As a constitutively active tyrosine kinase, BCR/ABL disrupts numerous cellular events including cell proliferation and survival. In the current proposal, experimental designs will address the possible role of a cyclin-dependent kinase inhibitor, p21Cip1 in contributing to the aberrant cell cycle and survival of BCR/ABL-hematopoietic cells. Previous findings identified positive and negative role of p21 in cell proliferation. In addition, p21 can function as an anti-apoptotic protein and has been shown to render transformed cells resistant to anti-cancer drugs. Of particular interest to CML, p21 protein is detected at higher levels in BCR/ABL-positive cells, compared to normal cells. Although highly labile, p21 protein is stabilized by phosphorylation mediated by AKT, an anti-apoptotic protein activated in CML. Based on these studies, it is intriguing to test whether p21Cip1 might contribute to the enhanced cell proliferation and survival observed in CML. RNA and protein studies will investigate the mechanism by which p21Cip1 is regulated in normal and BCR/ABL hematopoietic cells. Treatment with STI571 will delineate the contributing role of BCR/ABL tyrosine kinase activity in p21 regulation. Retroviral introduction of BCR/ABL into hematopoietic progenitors from p21-wildtype, -hemizygous, and -null mice will determine the contributing role of p21 in BCR/ABL-transformation. Syngeneic transplantations of these cells will assess the impact of the varying p21 levels on the onset and progression of CML in vivo.