title: Smad2/3-Regulated Expression of DLX2 Is Associated with Radiation-Induced Epithelial-Mesenchymal Transition and Radioresistance of A549 and MDA-MB-231 Human Cancer Cell Lines.
abstract: 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.
authors.affiliation: Radiation Biotechnology Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute (KAERI), Jeongeup, Republic of Korea.
authors.forename: Yeo-Jin
authors.initials: YJ
authors.lastname: Choi
authors.affiliation: Radiation Biotechnology Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute (KAERI), Jeongeup, Republic of Korea.
authors.forename: Ga-Young
authors.initials: GY
authors.lastname: Baek
authors.affiliation: 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.
authors.forename: Hae-Ran
authors.initials: HR
authors.lastname: Park
authors.affiliation: 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.
authors.forename: Sung-Kee
authors.initials: SK
authors.lastname: Jo
authors.affiliation: 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.
authors.forename: Uhee
authors.initials: U
authors.lastname: Jung
mesh_terms: D045744:Cell Line, Tumor; D002465:Cell Movement / Q000528:radiation effects; D002470:Cell Survival / Q000235:genetics / Q000528:radiation effects; D058750:Epithelial-Mesenchymal Transition / Q000528:radiation effects*; D018398:Homeodomain Proteins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D018960:Hyaluronan Receptors / Q000096:biosynthesis; D009361:Neoplasm Invasiveness / Q000473:pathology; D009369:Neoplasms / Q000473:pathology* / Q000532:radiotherapy; D014411:Neoplastic Stem Cells / Q000473:pathology; D010766:Phosphorylation; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D011836:Radiation Tolerance / Q000235:genetics*; D015398:Signal Transduction; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism*; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D053773:Transforming Growth Factor beta1 / Q000378:metabolism
chemical_list: C088334:Distal-less homeobox proteins; D018398:Homeodomain Proteins; D018960:Hyaluronan Receptors; D034741:RNA, Small Interfering; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1