Expression of activated Notch1 in different stages of osteosarcoma. The panels show representative images of Notch intracellular domain (NICD; red) expression in stages IB, IIA and IIB osteosarcoma tissues. Specific NICD staining was controlled by using isotype-specific control (control immunoglobulin G (IgG)) antibody. The lower graph shows the statistical analysis of the density of NICD+ cells in osteosarcoma tissues at different stages. Scale bar, 80 μm.