Reduced signaling by HER2 following prolonged vaccine-induced anti-HER2 antibody treatment. SK-BR-3 cells were stimulated for (A) 24 hours and (B) 72 hours with LacZ-VIA (A, lanes 2 to 4; B, lane 2), HER2-VIA (A, lanes 5 to 7; B, lane 3), and trastuzumab (A, lane 8 and 9; B, lane 4). Protein samples were immunoblotted with indicated antibodies. β-actin in the lower panel serves as a loading control. n = 3. ERK, extracellular signal-regulated protein kinase; IB, immunoblot; NS, non-stimulated.