Choi Yeo-Jin, Baek Ga-Young, Park Hae-Ran, Jo Sung-Kee, Jung Uhee
Radiation Biotechnology Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute (KAERI), Jeongeup, Republic of Korea.
Department of Radiation Biotechnology and Applied Radioisotope, University of Science and Technology (UST), Daejeon, Republic of Korea.
PLoS One. 2016 Jan 22;11(1):e0147343. doi: 10.1371/journal.pone.0147343. eCollection 2016.
The control of radioresistance and metastatic potential of surviving cancer cells is important for improving cancer eradication by radiotheraphy. The distal-less homeobox2 (DLX2) gene encodes for a homeobox transcription factor involved in morphogenesis and its deregulation was found in human solid tumors and hematologic malignancies. Here we investigated the role of DLX2 in association with radiation-induced epithelial to mesenchymal transition (EMT) and stem cell-like properties and its regulation by Smad2/3 signaling in irradiated A549 and MDA-MB-231 human cancer cell lines. In irradiated A549 and MDA-MB-231 cells, EMT was induced as demonstrated by EMT marker expression, phosphorylation of Smad2/3, and migratory and invasive ability. Also, irradiated A549 and MDA-MB-231 cells showed increased cancer stem cells (CSCs) marker. Interestingly, DLX2 was overexpressed upon irradiation. Therefore, we examined the role of DLX2 in radiation-induced EMT and radioresistance. The overexpression of DLX2 alone induced EMT, migration and invasion, and CSC marker expression. The reduced colony-forming ability in irradiated cells was partially restored by DLX2 overexpression. On the other hand, the depletion of DLX2 using si-RNA abolished radiation-induced EMT, CSC marker expression, and phosphorylation of Smad2/3 in irradiated A549 and MDA-MB-231 cells. Also, depletion of DLX2 increased the radiation sensitivity in both cell lines. Moreover, knockdown of Smad2/3, a key activator of TGF-β1 pathway, abrogated the radiation-induced DLX2 expression, indicating that radiation-induced DLX2 expression is dependent on Smad2/3 signaling. These results demonstrated that DLX2 plays a crucial role in radioresistance, radiation-induced EMT and CSC marker expression, and the expression of DLX2 is regulated by Smad2/3 signaling in A549 and MDA-MB-231 cell lines.
控制存活癌细胞的抗辐射性和转移潜能对于通过放射疗法提高癌症根除率至关重要。远端缺失同源盒2（DLX2）基因编码一种参与形态发生的同源盒转录因子，在人类实体瘤和血液系统恶性肿瘤中发现其失调。在此，我们研究了DLX2在辐射诱导的上皮-间质转化（EMT）和干细胞样特性中的作用，以及其在照射的A549和MDA-MB-231人癌细胞系中受Smad2/3信号通路的调控。在照射的A549和MDA-MB-231细胞中，如EMT标志物表达、Smad2/3磷酸化以及迁移和侵袭能力所示，诱导了EMT。此外，照射的A549和MDA-MB-231细胞显示癌症干细胞（CSC）标志物增加。有趣的是，照射后DLX2过表达。因此，我们研究了DLX2在辐射诱导的EMT和抗辐射性中的作用。单独过表达DLX2可诱导EMT、迁移和侵袭以及CSC标志物表达。照射细胞中降低的集落形成能力通过DLX2过表达部分恢复。另一方面，使用小干扰RNA（si-RNA）耗尽DLX2消除了照射的A549和MDA-MB-231细胞中辐射诱导的EMT、CSC标志物表达以及Smad2/3磷酸化。此外，耗尽DLX2增加了两种细胞系的辐射敏感性。此外，敲低TGF-β1通路的关键激活剂Smad2/3消除了辐射诱导的DLX2表达，表明辐射诱导的DLX2表达依赖于Smad2/3信号通路。这些结果表明，DLX2在抗辐射性、辐射诱导的EMT和CSC标志物表达中起关键作用，并且在A549和MDA-MB-231细胞系中DLX2的表达受Smad2/3信号通路调控。
