Epinephrine Stimulates Cell Proliferation and Induces Chemoresistance in Myeloma Cells through the β-Adrenoreceptor in vitro

To explore the effect of the β-adrenoreceptor signaling pathway on myeloma cells.The myeloma U266 cell line was treated with epinephrine and propranolol. Cell proliferation was analyzed by MTS assay. Apoptosis was detected by flow cytometry. The β-receptor subtype and the key enzyme of epinephrine were identified by reverse transcription polymerase chain reaction (RT-PCR).Epinephrine (5-50 μM) promoted U266 cell growth in a dose-dependent manner and neutralized the inhibition effect of bortezomib (25 and 50 ng/mL) in vitro. Cell proliferation was inhibited by a β-receptor antagonist, propranolol, at a concentration of 50-200 μM. The proportions of early and late apoptotic cells were enhanced after treatment with propranolol. The expression of caspase 3/7, 8, and 9 was elevated in propranolol-treated myeloma cells. Both β1- and β2-adrenoceptor mRNAs were expressed in the U266 cell line. Key enzymes dopamine hydroxylase and tyrosinehydroxylase were identified in myeloma cells.Our results reveal that epinephrine stimulates myeloma cell growth in vitro while the β-blocker propranolol has an antiproliferative effect, indicating that stress hormones may trigger the progression of myeloma.