β₂-adrenergic antagonists suppress pancreatic cancer cell invasion by inhibiting CREB, NF-κB and AP-1

Smoking and chronic stress are well-documented risk factors that are associated with β-adrenoceptors in the development of pancreatic cancer. Stimulation of β-adrenoceptors can activate cyclic adenosine monophosphate (cAMP)/ protein kinase A (PKA) and mitogen-activated protein kinase (MAPK) pathways in pancreatic cancer cells. Many recent studies have focused on the function of β-adrenoceptors in cancer invasion. Thus, we hypothesized that β-adrenoceptors may play a role in pancreatic cancer invasion, and β-blockers may suppress the pancreatic cancer invasion and proliferation. MIA PaCa-2 and BxPC-3 cell lines express mRNA and protein of both β1 and β2-adrenoceptors. β2-adrenergic antagonist ICI118,551 and β1/2-adrenergic antagonist propranolol significantly suppressed cell invasion and proliferation in comparison to β1-adrenergic antagonist metoprolol and control in a Matrigel invasion assay and subrenal capsular assay. Treatment with β2-adrenoceptor antagonists inhibited activation of transcription factors nuclear factor κB (NF-κB), activator protein 1 (AP-1) and cAMP response element binding protein (CREB) as demonstrated by electrophoretic mobility shift assays and Western blotting. β2-adrenoceptor antagonists also significantly altered vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2), matrix metalloproteinase 2 (MMP-2) and MMP-9 expression. The β2-adrenergic antagonists suppressed invasion and proliferation by inhibiting both cAMP/PKA and Ras, which regulate activation of the MAPK pathway and transcription factors, such as NF-κB, AP-1 and CREB, as well as expression of its target genes, MMP-9, MMP-2 and VEGF. However, β1-adrenergic antagonists suppressed invasion by inhibiting only the cAMP/PKA pathway, suggesting that they may be useful as novel preventive and therapeutic strategies for pancreatic cancer.