Attenuated LKB1-SIK1 signaling promotes epithelial-mesenchymal transition and radioresistance of non-small cell lung cancer cells.
BACKGROUND
Radiotherapy is one of the main therapeutic approaches for non-small cell lung cancer (NSCLC). However, radioresistant cancer cells can eventually cause tumor relapse and even fatal metastasis. It is thought that radioresistance and metastasis could be potentially linked by epithelial-mesenchymal transition (EMT). In this study, we established radioresistant NSCLC cells to investigate the potential relationship among radioresistance, EMT, and enhanced metastatic potential and the underlying mechanism involving liver kinase B1 (LKB1)-Salt-inducible kinase 1 (SIK1) signaling.


METHODS
The radioresistant cell lines A549R and H1299R were generated by dose-gradient irradiation of the parental A549 and H1299 cells. The radioresistance/sensitivity was evaluated by Cell Counting Kit-8 assay, apoptosis analysis, and/or clonogenic cell survival assay. The EMT phenotype and the signaling change were assessed by Western blotting. The abilities of invasion and migration were evaluated by transwell assays and wound healing assays.


RESULTS
The radioresistant cell lines A549R and H1299R displayed mesenchymal features with enhanced invasion and migration. Mechanistically, A549R and H1299R cells had attenuated LKB1-SIK1 signaling, which leaded to the up-regulation of Zinc-finger E-box-binding homeobox factor 1 (ZEB1)--a transcription factor that drives EMT. Re-expression of LKB1 in A549R cells reversed the EMT phenotype, whereas knockdown of LKB1 in H1299R cells further promoted the EMT phenotype. Moreover, re-expression of LKB1 in A549 cells increased the radiosensitivity, whereas knockdown of LKB1 in H1299 cells decreased the radiosensitivity.


CONCLUSIONS
Our findings suggest that attenuated LKB1-SIK1 signaling promotes EMT and radioresistance of NSCLC cells, which subsequently contributes to the enhanced metastatic potential. Targeting the LKB1-SIK1-ZEB1 pathway to suppress EMT might provide therapeutic benefits.
Shandong University School of Medicine, Jinan, 250012, Shandong, P. R. China.|Department of Radiation Oncology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, 221002, Jiangsu, P. R. China.
Yuan-Hu
YH
Yao
Leibniz Institute on Aging-Fritz Lipmann Institute, Jena, 07745, Germany.
Yan
Y
Cui
Department of Radiation Oncology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, 221002, Jiangsu, P. R. China.|Department of Radiation Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing, 210002, Jiangsu, P. R. China.
Xiang-Nan
XN
Qiu
Department of Radiation Oncology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, 221002, Jiangsu, P. R. China.
Long-Zhen
LZ
Zhang
Department of Radiation Oncology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, 221002, Jiangsu, P. R. China.|Jiangsu Key Laboratory of Biological Therapies for Tumors, Xuzhou Medical University, Xuzhou, 221002, Jiangsu, P. R. China.
Wei
W
Zhang
Department of Radiation Oncology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, 221002, Jiangsu, P. R. China.|Jiangsu Key Laboratory of Biological Therapies for Tumors, Xuzhou Medical University, Xuzhou, 221002, Jiangsu, P. R. China.
Hao
H
Li
Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong University, Jinan, 250117, Shandong, P. R. China. yujinmingsdjn@126.com.
Jin-Ming
JM
Yu
D000091162:AMP-Activated Protein Kinase Kinases; D017209:Apoptosis; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D058750:Epithelial-Mesenchymal Transition; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011836:Radiation Tolerance; D015398:Signal Transduction
D017346:Protein Serine-Threonine Kinases; C509080:SIK1 protein, human; C109790:STK11 protein, human; D000091162:AMP-Activated Protein Kinase Kinases
Epithelial-mesenchymal transition; LKB1; Lung cancer; Metastasis; Radioresistance; SIK1