PLEKHA8基因在T细胞急性淋巴细胞白血病中的功能和机制研究

T-cell acute lymphoblastic lymphoma/leukemia (T-ALL) is a very aggressive malignancy. Targetable molecules/pathways of T-ALL are limited because of an insufficient understanding of its genetics and biology. Because of the limitation of specific target treatment, only about 40% T-cell acute lymphoblastic lymphoma/leukemia is a very aggressive malignancy. Targetable molecules/pathways of T-ALL are limited because of an insufficient understanding of its genetics and biology. Because of the limitation of specific target treatment, only about 40% T-ALL patients reach the goal of long time survival. In our previous studies, we found PLEKHA8 is high expression in Pten conditional knockout mouse T-ALL and overexpression in T-ALL cell lines. The oncomine database also showed PLEKHA8 gene high expression in T-ALL patients, and we confirmed the expression level by RQ-PCR in T-ALL patients’ bone marrow leukemia cells. T-ALL cells dead vigorously (promote cells apoptosis) after knockdown this gene by shRNA or CRISPER system. In addition, we found PLEKHA8 may combined with transcriptional protein which is associated with leukemia tumorigenesis by yeast two hybrid system. For now, there is no research or study focus on this protein in leukemia field. Our project is detected PLEKHA8 gene function and mechanism in T-ALL, which is essential for leukemia cell death. These studies will likely provide insight into critical genes in the pathogenesis of T-ALL, and provide a platform for effective targeted therapies of T-ALL.

T细胞急性淋巴细胞白血病是高度恶性的血液肿瘤，目前对该病分子机制和生物学基础认识有限，尚无针对T-ALL的特异性有效药物，患者长期生存率只有40%左右。本课题对前期建立的Pten基因条件敲除T-ALL小鼠模型研究发现了新的潜在癌基因PLEKHA8。该基因在人和小鼠T-ALL细胞系中均高表达，同时检索oncomine数据库发现PLEKHA8基因在T-ALL患者中也存在高表达，并进一步在初诊的T-ALL患者原代白血病细胞中对其表达水平进行了验证。前期功能实验发现在T-ALL细胞系中应用shRNA或CRISPER系统干扰或敲除该基因，有促进凋亡作用。前期酵母双杂交实验显示，该基因可能与调控白血病相关基因转录蛋白结合。目前在白血病领域尚无针对PLEKHA8的任何研究，本课题旨在研究PLEKHA8基因在T-ALL中的功能和机制，探索其在T-ALL诊断分层和相关靶向药物开发的可能性。

急性T淋巴细胞白血病(T-ALL)是未成熟T细胞在骨髓和(或)淋巴组织中恶性增殖,导致的一种血液系统恶性肿瘤。目前,对T-ALL的治疗手段相对有限,仍然是以高强度化疗为基础的药物治疗和造血干细胞移植(HSCT)为主。随着细胞遗传学及分子生物学的发展,针对T-ALL的分型、分子生物学标志物及靶向治疗取得了一系列新进展，但是目前由于靶向治疗选择有限，大多数T-ALL患者接受大剂量多药化疗。为了进一步研究其发病机制并建立新的治疗靶点，我们研究了FAPP2（一种在T-ALL中高度表达的高尔基蛋白）在T-ALL生长和功能中的作用。我们发现，在使用shRNA系统敲除FAPP2基因后，T-ALL细胞的增殖和亚G1期积累减少。相反，FAPP2下调促进了细胞自噬。FAPP2敲除T-ALL细胞后，自噬标记物LC3Ⅱ/Ⅰ、Beclin 1和ATG5水平显著升高，而P62水平降低。荧光显微镜显示，FAPP2敲除导致LC3在T-ALL细胞的细胞质中积累。此外，FAPP2基因敲除细胞中PI（4）P和PI（3,4,5）P水平降低，P-AKT和P-mTOR的磷酸化下调。总之，我们的结果表明，FAPP2表达的降低抑制了细胞增殖，导致T-ALL细胞亚G1期积累，并增强了T-ALL细胞的自噬，这可能是由PI（4）P、PI（3,4,5）P和PI3K/AKT/mTOR途径介导的。我们的结果为T-ALL的发病机制和潜在靶向治疗的发展提供了新的见解。

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