Department of Medical Oncology, University Medical Center Groningen, University of Groningen, the Netherlands.
Cell Oncol (Dordr). 2011 Jun;34(3):245-59. doi: 10.1007/s13402-011-0033-9. Epub 2011 Apr 30.
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) initiates apoptosis in tumor cells upon binding to its cognate agonistic receptors, death receptors 4 and 5 (DR4 and DR5). The activity of the insulin-like growth factor 1 (IGF-1) survival pathway is often increased in cancer, influencing both cell proliferation and apoptosis. We hypothesized that inhibiting the IGF-1 receptor (IGF-1R) using NVP-AEW541, a small molecular weight tyrosine kinase inhibitor of the IGF-1R, could increase death receptor (DR)-mediated apoptosis in colon cancer cells.
The analyses were performed by caspase assay, flow cytometry, Western blotting, immunoprecipitation and fluorescent microscopy.
Preincubation with NVP-AEW541 surprisingly decreased apoptosis induced by recombinant human TRAIL (rhTRAIL) or an agonistic DR4 antibody while sensitivity to an agonistic DR5 antibody was increased. NVP-AEW541 could inhibit IGF-1-induced activation of the phosphatidylinositol 3-kinase (PI3K) pathway. The effects of the PI3K inhibitor LY294002 on TRAIL-induced apoptosis were similar to those of NVP-AEW541, further supporting a role for IGF-1R-mediated activation of PI3K. We show that PI3K inhibition enhances DR5-mediated caspase 8 processing but also lowers DR4 membrane expression and DR4-mediated caspase 8 processing. Inhibition of PI3K reduced rhTRAIL sensitivity independently of the cell line preference for either DR4- or DR5-mediated apoptosis signaling.
Our study indicates that individual effects on DR4 and DR5 apoptosis signaling should be taken into consideration when combining DR-ligands with PI3K inhibition.
肿瘤坏死因子相关凋亡诱导配体（TRAIL）与肿瘤细胞上的同源激动型受体（死亡受体 4 和 5，DR4 和 DR5）结合后，可诱导其发生凋亡。胰岛素样生长因子 1（IGF-1）生存途径的活性在癌症中经常增加，影响细胞增殖和凋亡。我们假设使用小分子 IGF-1 受体（IGF-1R）酪氨酸激酶抑制剂 NVP-AEW541 抑制 IGF-1R 可以增加结肠癌细胞中死亡受体（DR）介导的细胞凋亡。
通过半胱天冬酶测定、流式细胞术、Western 印迹、免疫沉淀和荧光显微镜进行分析。
出乎意料的是，用 NVP-AEW541 预处理可降低重组人 TRAIL（rhTRAIL）或激动型 DR4 抗体诱导的细胞凋亡，而对激动型 DR5 抗体的敏感性增加。NVP-AEW541 可以抑制 IGF-1 诱导的磷脂酰肌醇 3-激酶（PI3K）途径的激活。PI3K 抑制剂 LY294002 对 TRAIL 诱导的细胞凋亡的作用与 NVP-AEW541 的作用相似，进一步支持了 IGF-1R 介导的 PI3K 激活的作用。我们表明，PI3K 抑制增强了 DR5 介导的半胱天冬酶 8 的加工，但也降低了 DR4 的膜表达和 DR4 介导的半胱天冬酶 8 的加工。PI3K 抑制可降低 rhTRAIL 的敏感性，而与细胞系对 DR4 或 DR5 介导的凋亡信号传导的偏好无关。
我们的研究表明，在将 DR 配体与 PI3K 抑制联合使用时，应考虑对 DR4 和 DR5 凋亡信号传导的单独影响。
