Subcellular localization of Shp2 in leukemia cells during cell cycle. (A) Cells at interphase. (B) Cells at mitosis. Double immunofluorescence labeling of Shp2 with Ki-67 antigen was performed in quiescent and proliferating cells. Cells were fixed, permeabilized, and stained with anti-Shp2 (green) and anti–Ki-67 antigen (red) antibodies. The scale bar represents 10 μm. Similar results were also found in lymphoblastic leukemic cells and normal hematopoietic progenitor cells (data not shown). Images were viewed at 400 ×/0.75 numerical aperture (NA), with a Zeiss Axioskop II microscope, Images were captured with a SPOT 1.3.0 CCD camera (Diagnostic Instruments, Detroit, MI) and transferred to Adobe Photoshop 6.0 (Adobe, San Jose, CA).