Kuhn Deborah J, Smith David M, Pross Seth, Whiteside Theresa L, Dou Q Ping
Drug Discovery Program, H. Lee Moffitt Cancer Center and Research Institute, College of Medicine, University of South Florida, Tampa, Florida 33612-9497, USA.
J Cell Biochem. 2003 Jul 1;89(4):824-36. doi: 10.1002/jcb.10557.
It has been previously demonstrated that human carcinomas express interleukin-2 receptor (IL-2R) alpha, beta, and gamma chains. The beta and gamma chains of IL-2R have intermediate binding affinity for IL-2 and are responsible for the intracellular signaling cascades after IL-2 stimulation. IL-2Ralpha lacks the cytoplasmic domain, but is essential for increasing the IL-2-binding affinity of other receptors. Overexpression of IL-2Ralpha in tumor cells is associated with tumor progression and a poor patient prognosis. To define molecular mechanisms responsible for the effects associated with IL-2Ralpha expression, ex vivo experiments were performed with the squamous cell carcinoma head-and-neck cancer line, PCI-13, which was genetically engineered to overexpress the IL-2Ralpha chain. While IL-2Ralpha-overexpressing PCI-13 cells were capable of forming colonies in soft agar, PCI-13 cells transfected with the control vector or those expressing IL-2Rgamma did not. Consistently, IL-2Ralpha-expressing tumor cells proliferated more rapidly than the control or IL-2Rgamma+ cells, associated with increased levels of cyclins A and D1 and cyclin-dependent kinase (cdk(s)) 2 and 4 proteins. In addition, IL-2Ralpha-expressing cells were significantly more resistant to apoptosis induction by a tripeptidyl proteasome inhibitor (ALLN) and two chemotherapeutic drugs (VP-16 and taxol) than the control or IL-2Rgamma+ cells. Accompanying the drug resistance, high levels of anti-apoptotic Bcl-X(L) and Bcl-2 proteins were found in the mitochondria-containing fraction of IL-2Ralpha-expressing tumor cells. Treatment of IL-2Ralpha-expressing cells with a specific Janus kinase 3 (Jak3) inhibitor decreased expression of cyclin A, cyclin D1, Bcl-X(L), and Bcl-2 proteins. Finally, high levels of ubiquitinated proteins were detected in the proliferating IL-2Ralpha-expressing cells. Our data suggest that increased proliferation rates and decreased drug sensitivity of IL-2Ralpha-expressing tumor cells are responsible for the enhanced tumor aggressiveness and poor clinical prognosis of patients whose tumors express IL-2Ralpha.
先前已有研究表明，人类癌细胞表达白细胞介素-2受体（IL-2R）的α、β和γ链。IL-2R的β链和γ链对IL-2具有中等结合亲和力，并负责IL-2刺激后的细胞内信号级联反应。IL-2Rα缺乏胞质结构域，但对增加其他受体的IL-2结合亲和力至关重要。肿瘤细胞中IL-2Rα的过表达与肿瘤进展及患者预后不良相关。为了确定与IL-2Rα表达相关效应的分子机制，我们使用头颈部鳞状细胞癌系PCI-13进行了体外实验，该细胞系经过基因工程改造以过表达IL-2Rα链。虽然过表达IL-2Rα的PCI-13细胞能够在软琼脂中形成集落，但转染了对照载体的PCI-13细胞或表达IL-2Rγ的细胞则不能。一致地，表达IL-2Rα的肿瘤细胞比对照细胞或IL-2Rγ +细胞增殖更快，这与细胞周期蛋白A和D1以及细胞周期蛋白依赖性激酶（cdk）2和4蛋白水平的增加有关。此外，表达IL-2Rα的细胞对三肽基蛋白酶体抑制剂（ALLN）和两种化疗药物（VP-16和紫杉醇）诱导的凋亡明显比对照细胞或IL-2Rγ +细胞更具抗性。伴随着耐药性，在表达IL-2Rα的肿瘤细胞含线粒体部分中发现了高水平的抗凋亡Bcl-X(L)和Bcl-2蛋白。用特异性Janus激酶3（Jak3）抑制剂处理表达IL-2Rα的细胞可降低细胞周期蛋白A、细胞周期蛋白D1、Bcl-X(L)和Bcl-2蛋白的表达。最后，在增殖的表达IL-2Rα的细胞中检测到高水平的泛素化蛋白。我们的数据表明，表达IL-2Rα的肿瘤细胞增殖率增加和药物敏感性降低是肿瘤侵袭性增强以及肿瘤表达IL-2Rα的患者临床预后不良的原因。
