Xia G, Kumar S R, Stein J P, Singh J, Krasnoperov V, Zhu S, Hassanieh L, Smith D L, Buscarini M, Broek D, Quinn D I, Weaver F A, Gill P S
Department of Medicine, University of Southern California Keck School of Medicine, Los Angeles, CA 90033, USA.
Oncogene. 2006 Feb 2;25(5):769-80. doi: 10.1038/sj.onc.1209108.
We sought to evaluate the biological function of the receptor tyrosine kinase EphB4 in bladder cancer. All of the nine bladder cancer cell lines examined express EphB4 and the receptor could be phosphorylated following stimulation with its cognate ligand, EphrinB2. Out of the 15 fresh bladder cancer specimens examined, 14 expressed EphB4 with a mean sevenfold higher level of expression compared to adjacent normal urothelium. EphB4 expression was regulated by several mechanisms: EPHB4 gene locus was amplified in 27% tumor specimens and 33% cell lines studied; inhibition of EGFR signaling downregulated EphB4 levels; and forced expression of wild-type p53 reduced EphB4 expression. EphB4 knockdown using specific siRNA and antisense oligodeoxynucleotides molecules led to a profound inhibition in cell viability associated with apoptosis via activation of caspase-8 pathway and downregulation of antiapoptotic factor, bcl-xl. Furthermore, EphB4 knockdown significantly inhibited tumor cell migration and invasion. EphB4 knockdown in an in vivo murine tumor xenograft model led to a nearly 80% reduction in tumor volume associated with reduced tumor proliferation, increased apoptosis and reduced tumor microvasculature. EphB4 is thus a potential candidate as a predictor of disease outcome in bladder cancer and as target for novel therapy.
我们试图评估受体酪氨酸激酶EphB4在膀胱癌中的生物学功能。所检测的9种膀胱癌细胞系均表达EphB4，且该受体在其同源配体EphrinB2刺激后可发生磷酸化。在所检测的15份新鲜膀胱癌标本中，14份表达EphB4，其表达水平平均比相邻正常尿路上皮高7倍。EphB4的表达受多种机制调控：在27%的肿瘤标本和33%的所研究细胞系中，EPHB4基因位点发生扩增；抑制表皮生长因子受体（EGFR）信号可下调EphB4水平；野生型p53的强制表达可降低EphB4表达。使用特异性小干扰RNA（siRNA）和反义寡脱氧核苷酸分子敲低EphB4，可通过激活半胱天冬酶-8途径和下调抗凋亡因子bcl-xl，导致与细胞凋亡相关的细胞活力受到显著抑制。此外，敲低EphB4可显著抑制肿瘤细胞的迁移和侵袭。在体内小鼠肿瘤异种移植模型中敲低EphB4，可使肿瘤体积减少近80%，这与肿瘤增殖减少、细胞凋亡增加和肿瘤微血管减少有关。因此，EphB4可能是膀胱癌疾病预后的预测指标和新型治疗的靶点。
