LLL12 Inhibits Endogenous and Exogenous Interleukin-6-induced STAT3 Phosphorylation in Human Pancreatic Cancer Cells

Pancreatic cancer is one of the most serious types of cancer, with a five-year survival rate at only 6%. There is a critical need to develop more effective treatments for pancreatic cancer. Growing evidence shows that chronic inflammation plays a crucial role in tumor initiation and progression. Here we demonstrated that the endogenous expression of the inflammatory cytokine interleukin-6 (IL-6) correlates with signal transducer and activator of transcription 3 (STAT3) phosphorylation in human pancreatic cancer cells. Inhibition of the endogenous IL-6/STAT3 pathway reduces cell viability. Exogenous IL-6 induces STAT3 phosphorylation, but differently induces phosphorylation of STAT3 upstream kinases, Janus kinase 1(JAK1), JAK2, and tyrosine kinase 2 (TYK2). Interestingly, LLL12, a nonpeptide, cell-permeable small molecule, selectively blocked exogenous IL-6-induced STAT3 phosphorylation and nuclear translocation in both PANC-1 and ASPC-I pancreatic cancer cell lines independently of the phosphorylation of JAK1, JAK2, and TYK2. These results suggest that the inhibition of endogenous and exogenous IL-6-mediated STAT3 signaling may be a potential therapeutic approach for pancreatic cancer.