C/EBPs induce partial morphologic differentiation of murine APL cells.

Freshly harvested bone marrow and spleen cells from leukemic mice were transduced on 2 consecutive days with the retroviral constructs. GFP⁺ cells were sorted 5 days after the first transduction. Cytospins of sorted cells were stained with Wright Giemsa, and differential counts were performed (100-300 cells). (A) RA-responsive leukemia no. 1111. Results of 3 independent experiments expressed as means ± SDs are shown. Compared with MIG-infected control, C/EBPα-infected cells showed significantly fewer immature forms or blasts (P = .03) and significantly more segmented forms (P = .01). C/EBPε-infected cells showed significantly more intermediate-stage cells without segmentation (P = .04), with the changes in immature forms or blasts and segmented forms nearing statistical significance (P = .06). (B) RA-resistant leukemia no. 4048.2. Results of 2 independent experiments expressed as means ± SDs are shown. Decreases in immature forms or blasts and increases in intermediate forms and segmented forms are apparent. Because some variation occurred between the 2 experiments, only the increase in segmented forms induced by C/EBPε reached statistical significance (P = .05). Myeloid cells with atypical nuclear segmentation and basophilic cytoplasm were enumerated separately from intermediate forms and from neutrophils of normal appearance.