Han Edward Kyu-Ho, Mcgonigal Thomas, Butler Chris, Giranda Vincent L, Luo Yan
Abbott Laboratories, Department of R47S, Cancer Research, Global Pharmaceutical Research Division, Abbott Park, IL 60064, USA.
Anticancer Res. 2008 Mar-Apr;28(2A):957-63.
Akt (PKB) is a serine/threonine protein kinase that plays an important role in the transduction of signals affecting apoptosis, cell proliferation and survival. The Akt gene is frequently hyperactivated in tumors and has been shown to be amplified in a number of types of human cancers. Furthermore, Akt activity is elevated in cell lines with the mutated PTEN tumor suppressor gene. These studies establish Akt as an attractive target for cancer therapy. To determine the roles of Akt1, Akt2 and Akt3 in signal transduction, constitutively active Akt1, Akt2 and Akt3 was ectopically overexpressed in human pancreatic MiaPaCa-2 cells. The three Akt stable clones were characterized to determine their effects on transformation and proliferation. Compared to a vector control, the three Akt clones were able to drive cellular proliferation even in reduced serum conditions. Furthermore, in soft-agar assays, the Akt clones showed an 25-38% increase in colony formation in 2% serum. Our results indicate that all three forms of Akt may have protective effects within the cell depending on the type of apoptotic stimuli. Using 2D-PAGE comparisons between parental and Akt overexpressing cells, we attempted to determine novel targets of Akt phosphorylation. In this study, we identified prohibitin as a substrate for Akt both in vitro and in vivo. These studies suggest that Akt may regulate the cellular function of prohibitin via its phosphorylation.
Akt（蛋白激酶B）是一种丝氨酸/苏氨酸蛋白激酶，在影响细胞凋亡、增殖和存活的信号转导中起重要作用。Akt基因在肿瘤中经常过度激活，并且在多种人类癌症中已被证明存在扩增。此外，在具有突变型PTEN肿瘤抑制基因的细胞系中，Akt活性升高。这些研究表明Akt是癌症治疗的一个有吸引力的靶点。为了确定Akt1、Akt2和Akt3在信号转导中的作用，在人胰腺MiaPaCa-2细胞中异位过表达组成型活性Akt1、Akt2和Akt3。对这三个Akt稳定克隆进行表征，以确定它们对转化和增殖的影响。与载体对照相比，即使在血清减少的条件下，这三个Akt克隆也能够驱动细胞增殖。此外，在软琼脂试验中，Akt克隆在2%血清中集落形成增加了25 - 38%。我们的结果表明，根据凋亡刺激的类型，所有三种形式的Akt在细胞内可能都具有保护作用。通过对亲本细胞和过表达Akt的细胞进行二维凝胶电泳比较，我们试图确定Akt磷酸化的新靶点。在这项研究中，我们在体外和体内都鉴定出抑制素是Akt的底物。这些研究表明，Akt可能通过其磷酸化作用来调节抑制素的细胞功能。
