Glaucocalyxin A regulates STAT3 signaling pathway through influencing IL-6 expression in HCCLM3 cells
Objective 
To investigate the effects of glaucocalyxin A (GLA) on the expression of signal transduction and activator of transcription 3 (STAT3) signaling pathway in HCCLM3 cells for better understanding the role of GLA in tumor metastasis. 
 
 
Methods 
HCCLM3 cells were stimulated by different concentrations (0.1 ng/ml, 1 ng/ml, 10 ng/ml, 100 ng/ml and 1 000 ng/ml) of GLA for 48 h. Expression of IL-6, STAT3/pSTAT3Tyr705 and MMP9 at mRNA and protein levels were detected by qRT-PCR and Western blot, respectively. Transwell invasion and migration assays were performed to analyze cell invasion and migration. ELISA was used to measure the concentrations of IL-6 in culture media. 
 
 
Results 
Expression of IL-6 at mRNA and protein levels, STAT3Tyr705 phosphorylation, and the migration and invasion of HCCLM3 cells were significantly enhanced after stimulation of HCCLM3 cells with 0.1 ng/ml of GLA, but inhibited by GLA at the concentration of 1 000 ng/ml. Moreover, more IL-6 was secreted out of the HCCLM3 cells treated with 0.1 ng/ml of GLA. 
 
 
Conclusions 
GLA might affect the metastasis of HCCLM3 cells through regulating the expression of IL-6 and the phosphorylation of STAT3Tyr705. These regulatory effects were closely related to the concentration of GLA. 
 
 
Key words: 
Glaucocalyxin A; Interleukin-6; Signal transduction and activator of transcription 3; Hepatocarcinoma