[Effects of transfected SOCS3 gene on proliferation of human lung adenocarcinoma cell line A549].

BACKGROUND & 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). CONCLUSION: SOCS3 protein might inhibit proliferation of A549 cells by lowering the tyrosine-phosphorylated level of STAT3 protein.