ATO/ATRA induce NPM1 wild-type protein relocalization in the nucleus in NPM1-mutated OCI/AML3 cells. (A-B) Immunofluorescence staining for NPM1 wild-type protein using a specific mouse monoclonal antibody (NPMwt) (secondary goat anti-mouse Alexa-Fluor 488, green) of cytospin preparations from NPM1-mutated AML cell line OCI/AML3, untreated vs treated with ATO 3 μM, ATRA 1 μM, or ATO/ATRA combination for 24 hours. Nuclei are stained with DAPI (blue). Images were collected at fluorescence microscope (Olympus, Shinjuku, Tokyo, Japan) using a ×100/1.3 NA oil objective and processed with CellSens Digital Imaging Software (Olympus) and Adobe Photoshop 7.0. White arrows in panel A point to representative NPM1 wild-type cytoplasmic positivity. White asterisk(s) in panel A indicate representative cells reproduced in panel B for details. Number of nucleoli/cell (means ± SD on 50 cells) is shown in the inset in panel A. Black asterisks indicate statistical significance.