[Effects of transfected SOCS3 gene on proliferation of human lung adenocarcinoma cell line A549].
OBJECTIVE
Previous studies showed that signal transducers and activators of transcription 3(STAT3) could be constantly activated in many kinds of tumor cells; constantly activated STAT3 could make cell malignant transformation, and enhance the malignant proliferation of tumor cells. The suppressors of cytokine signaling (SOCS) proteins, a recently identified family, could suppress the tyrosine-phosphorylated process of STAT protein to negatively regulate STAT-mediated cytokine signaling, which is closely related to cell survival, proliferation, and apoptosis. Among the SOCS protein family, SOCS3 is the most potent inhibitors of cytokine-induced signaling. This experiment was to investigate the effect of SOCS3 on proliferation of human lung adenocarcinoma cell line A549.


METHODS
A549 cells were co-transfected with pEFSOCS3 and pSV2neo by liposome, expression of SOCS3 mRNA and protein was determined by reverse transcriptase-polymerase chain reaction (RT-PCR), and immunocytochemistry. Tyrosine-phosphorylated STAT3 level was measured by Western blot analysis. MTT assay and (3)-TdR incorporation were used to measure the cell proliferation in pEFSOCS3-transfected group, and control group (non-transfected, and pEF-transfected A549).


RESULTS
Compared with control group, tyrosine-phosphorylated STAT3 level suppressed greatly in pEFSOCS3-transfected A549 cells (P< 0.01). The inhibitory rate of cell growth in pEFSOCS3-transfected group was 40.58%, and in control group was 32.23%. (3)-TdR incorporation (48 056+/-1 331) in pEFSOCS3-transfected group was significantly lower than that of control group (81,481+/-2,584, and 75,590+/-2,678, P< 0.01).


CONCLUSIONS
SOCS3 protein might inhibit proliferation of A549 cells by lowering the tyrosine-phosphorylated level of STAT3 protein.
Yu
Zu-Bin
ZB
Department of Thoracic Surgery, Xinqiao Hospital, The Third Military Medical University, Chongqing, 400037, PR China. ybll@21cn.com
Min
Jia-Xin
JX
Bai
Li
L
Yao
Ke
K
Zhang
Guo-Qiang
GQ
D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012097:Repressor Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D050796:STAT3 Transcription Factor; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D014162:Transfection
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C106644:SOCS3 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D014157:Transcription Factors