X-radiation induces non-small-cell lung cancer apoptosis by upregulation of Axin expression.
OBJECTIVE
Axis inhibition (Axin) is an important negative regulator of the Wnt pathway. This study investigated the relationship between Axin expression and sensitivity to X-rays in non-small-cell lung cancer (NSCLC) to find a useful indicator of radiosensitivity.


METHODS
Tissue from NSCLC patients, A549 cells, and BE1 cells expressing Axin were exposed to 1-Gy of X-radiation. Axin and p53 expression levels were detected by immunohistochemistry and reverse transcription-PCR. Apoptosis was determined by TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) assay and FACS (fluorescence-activate cell sorter) analysis. Caspase-3 activity was determined by Western blotting. Phospho-JNK expression was determined by immunofluorescence.


RESULTS
The expression of Axin was significantly lower in NSCLC tissues than in normal lung tissues (p < 0.05). Axin expression correlates with differentiation, TNM staging, and lymph node metastasis of NSCLC (p < 0.05). Its expression negatively correlates with the expression of p53(mt) (p=0.000) and positively correlates with apoptosis (p=0.002). The prognosis of patients with high expression of Axin was better than those with low expression. X-radiation increases Axin expression in NSCLC tissue, and caspase-3 is significantly higher in samples in which Axin is increased (p < 0.05). Both X-radiation and Axin induce apoptosis of A549 and BE1 cells; however, the combination of the two enhances the apoptotic effect (p < 0.05). In A549 cells, inhibition of p53 blocks Axin-induced apoptosis, whereas in BE1 cells, the JNK pathway is required.


CONCLUSIONS
Axin induces the p53 apoptotic pathway in cells where this pathway is intact; however, in cells expressing p53(mt), Axin induces apoptosis via the JNK pathway. Elevated Axin expression following X-ray exposure is a reliable indicator for determining the radiosensitivity of NSCLC.
Han
Yang
Y
Department of Pathology, College of Basic Medical Sciences and First Affiliated Hospital of China Medical University, Shenyang, PR China.
Wang
Yan
Y
Xu
Hong-Tao
HT
Yang
Lian-He
LH
Wei
Qiang
Q
Liu
Yang
Y
Zhang
Yong
Y
Zhao
Yue
Y
Dai
Shun-Dong
SD
Miao
Yuan
Y
Yu
Juan-Han
JH
Zhang
Jun-Yi
JY
Li
Guang
G
Yuan
Xi-Ming
XM
Wang
En-Hua
EH
D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy; D000328:Adult; D000368:Aged; D017209:Apoptosis / Q000502:physiology*; D060466:Axin Protein; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D020287:In Situ Nick-End Labeling; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011836:Radiation Tolerance / Q000502:physiology*; D012097:Repressor Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D016159:Tumor Suppressor Protein p53 / Q000032:analysis / Q000378:metabolism; D015854:Up-Regulation
D060466:Axin Protein; D014408:Biomarkers, Tumor; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; D048670:MAP Kinase Kinase 4; D053148:Caspase 3