Overexpression of STAT3 potentiates growth, survival, and radioresistance of non-small-cell lung cancer (NSCLC) cells.
OBJECTIVE
Activation of signal transducer and activator of transcription 3 (STAT3) play important roles in tumorigenesis and tumor progression. The overexpression of STAT3 has been found in various malignancies including non-small-cell lung carcinoma (NSCLC). The purpose of this study was to explore the correlation between overexpression of STAT3 gene and growth, survival, and radiosensitivity of NSCLC cells.


METHODS
Subclones using vector-based short hairpin RNA (shRNA) were established. RT-PCR and Western blot assays were performed to detect the expression of STAT3 mRNA and protein in untransfected or stably transfected NSCLC cells. Then, MTT and soft agar colony assays were performed to determine the effect of STAT3 inhibition on in vitro growth of NSCLC cells. Hoechst staining assay was performed to analyze the effect of STAT3 inhibition on apoptosis of NSCLC cells. Additionally, clonogenic survival assays were performed to detect the effect of STAT3 inhibition on in vitro radiosensitivity of NSCLC cells. Finally, to examine the effect of pSUPER-shSTAT3 on proliferation and radiosensitivity in vivo, a subcutaneous (s.c.) tumor formation assay in nude mice was performed.


RESULTS
We successfully established two stable transfected cell lines (A549/shSTAT3 and SK-MES-1/shSTAT3) in which the expression of STAT3 mRNA and protein was down-regulated. Those two stable subclones showed a significantly dramatic reduction in colony-forming ability and proliferation not only in vitro but also in vivo. The apoptotic rates of A549/shSTAT3 and SK-MES-1/shSTAT3 cells increased to 19.2% and 16.4%, respectively. Moreover, shRNA-mediated STAT3 inhibition could also significantly enhance radiosensitivity of NSCLC cells both in vitro and in vivo.


CONCLUSIONS
Together, the overexpression of STAT3 is correlated with growth, survival, and radioresistance of NSCLC cells, and STAT3 might be a molecular therapeutic target for gene therapy or radiosensitization of NSCLC.
Yin
Zhen-Jie
ZJ
Department of Respiratory Medicine, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, China. yinzhenjie_td@yahoo.com.cn
Jin
Fa-Guang
FG
Liu
Tong-Gang
TG
Fu
En-Qing
EQ
Xie
Yong-Hong
YH
Sun
Rui-Lin
RL
D000230:Adenocarcinoma / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D000818:Animals; D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D002455:Cell Division / Q000502:physiology / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000502:physiology / Q000528:radiation effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D034622:RNA Interference; D011836:Radiation Tolerance / Q000235:genetics; D050796:STAT3 Transcription Factor / Q000235:genetics*; D023041:Xenograft Model Antitumor Assays
D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human