In the present study, β2-AR level was found to be up-regulated in MCF-7 cells overexpressing Her2 (MCF-7/Her2).Correlation of β2-AR level with Her2 status was demonstrated in breast cancer tissue samples.Constitutive phosphorylation of ERK, mRNA expression up-regulation of catecholamine-synthesis enzymes and increased epinephrine release were detected in MCF-7/Her2 cells.β2-AR expression induced by epinephrine and involvement of ERK signaling were validated.The data indicate that Her2 overexpression and excessive phosphorylation of ERK cause epinephrine autocrine release from breast cancer cells, resulting in up-regulation of β2-AR expression.