Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
Strahlenther Onkol. 2014 Nov;190(12):1154-62. doi: 10.1007/s00066-014-0708-z. Epub 2014 Jul 3.
The present study was undertaken to investigate whether radiation induces the expression of vascular endothelial growth factor C (VEGF-C) through activation of the PI3K/Akt/mTOR pathway,subsequently affecting endothelial cells.
Radiotherapy-induced tumor micro-lymphatic vessel density (MLVD) was determined in a lung cancer xenograft model established in SCID mice. The protein expression and phosphorylation of members of the PI3K/Akt/mTOR pathway and VEGF-C secretion and mRNA expression in irradiated lung cancer cells were assessed by Western blot analysis, enzyme-linked immunosorbent assays (ELISAs), and reverse transcriptase-polymerase chain reaction (RT-PCR). Moreover, specific chemical inhibitors were used to evaluate the role of the PI3K/Akt/mTOR signaling pathway. Conditioned medium (CM) from irradiated control-siRNA or VEGF-C-siRNA-expressing A549 cells was used to evaluate the proliferation of endothelial cells by the MTT assay.
Radiation increased VEGF-C expression in a dose-dependent manner over time at the protein but not at the mRNA level. Radiation also up-regulated the phosphorylation of Akt, mTOR, 4EBP, and eIF4E, but not of p70S6K. Radiation-induced VEGF-C expression was down-regulated by LY294002 and rapamycin (both p < 0.05). Furthermore, CM from irradiated A549 cells enhanced human umbilical vein endothelial cell (HUVEC) and lymphatic endothelial cell (LEC) proliferation, which was not observed with CM from irradiated VEGF-C-siRNA-expressing A549 cells.
Radiation-induced activation of the PI3K/Akt/mTOR signaling pathway increases VEGF-C expression in lung cancer cells, thereby promoting endothelial cell proliferation.
本研究旨在探讨辐射是否通过激活 PI3K/Akt/mTOR 通路诱导血管内皮生长因子 C（VEGF-C）的表达，进而影响内皮细胞。
在 SCID 小鼠建立的肺癌异种移植模型中，测定放疗诱导的肿瘤微淋巴管密度（MLVD）。通过 Western blot 分析、酶联免疫吸附测定（ELISA）和逆转录-聚合酶链反应（RT-PCR）评估辐射诱导的肺癌细胞中 PI3K/Akt/mTOR 通路成员的蛋白表达和磷酸化以及 VEGF-C 的分泌和 mRNA 表达。此外，还使用特异性化学抑制剂来评估 PI3K/Akt/mTOR 信号通路的作用。用照射对照-siRNA 或 VEGF-C-siRNA 表达 A549 细胞的条件培养基（CM）通过 MTT 法评估内皮细胞的增殖。
辐射以时间和剂量依赖的方式增加 VEGF-C 的蛋白表达，但不增加其 mRNA 表达。辐射还上调 Akt、mTOR、4EBP 和 eIF4E 的磷酸化，但不增加 p70S6K 的磷酸化。LY294002 和雷帕霉素（均 p<0.05）下调辐射诱导的 VEGF-C 表达。此外，照射 A549 细胞的 CM 增强人脐静脉内皮细胞（HUVEC）和淋巴管内皮细胞（LEC）的增殖，但照射 VEGF-C-siRNA 表达 A549 细胞的 CM 则无此作用。
辐射诱导的 PI3K/Akt/mTOR 信号通路的激活增加肺癌细胞中 VEGF-C 的表达，从而促进内皮细胞增殖。
