TBLR1-RARα induces ATRA-mediated cell differentiation of U937 cells. U937 cells were infected with lentivirus, which resulted in expression of TBLR1-RARα, or control lentivirus, respectively. The transduced cells were sorted for GFP-positive cell populations for further study. (A-D) Flow cytometry analysis of cell surface expression of CD11b for GFP-positive U937 cells and NB4 cells (positive control) incubated in different dosages of ATRA or ethanol solvent after 3, 6, 9, and 12 days, respectively. Because few live NB4 cells could be detected after 12 days, the data of NB4 cells in (D) were not shown. The expression levels of CD11b of the TBLR1-RARα-expressed group were increased significantly compared with the control group in a dose- and time-dependent manner in the presence of ATRA. In flow cytometry analysis, the results represented mean values ± SD corresponding to at least 3 independent experiments executed in triplicate. Statistical significance was determined with the Student t test. *P < .05;**P < .01; and ***P < .001 were accepted as statistically significant. (E) Morphologic changes of U937 and NB4 cells treated with different concentrations of ATRA or ethanol solvent for 12 and 9 days. The TBLR1-RARα-expressed group presented morphologic changes of differentiation in the presence of ATRA (Wright-Giemsa stain, original magnification ×1000).