Expression and regulation of the evi-1 gene in the human factor-dependent leukemia cell line, UCSD/AML1

The human factor-dependent leukemia cell line UCSD/AML1 contains the t(3;3) (q21;q26) characteristic of the syndrome of acute leukemia with high platelets. The human homologue of the murine leukemia oncogene evi-1 was recently localized to chromosome 3q24-3q28 and transcription of evi-1 is a frequent event in mouse-retrovirus-induced leukemias (17). To determine whether translocations near human 3q24 might induce similar genetic changes, we examined and compared evi-1 and c-myc expression and regulation in UCSD/AML1 cells. Steady-state evi-1 transcripts were detected in UCSD/AML1 and murine leukemia M1 cells, but were not present in HL60 or Namalwa human leukemia cells. Transcription assays showed the evi-1 gene was actively transcribed in UCSD/AML1, but not HL60 nuclei. Evi-1 transcript sizes and half-life were similar in UCSD/AML1 and human HEC-1B carcinoma cells which express evi-1 transcripts, but do not have abnormalities involving chromosome 3. An alternative splice site detected by polymerase chain reaction was present in transcripts from both cell lines. Regulation of evi-1 RNA in UCSD/AML1 cells was similar to that of actin transcripts in response to cycloheximide or phorbol-ester-induced macrophage differentiation. After withdrawal of granulocyte/macrophage colony-stimulating factor (GM-CSF), evi-1, actin, and histone H3 transcripts declined in concert with exit from the cell cycle. Minor differences in rates of recovery were noted for these three genes after GM-CSF restimulation. In contrast, c-myc was expressed at high levels in UCSD/AML1 cells and showed evidence for specific regulation in response to cycloheximide, phorbol ester, and GM-CSF withdrawal and restimulation. These studies suggest the 3q translocation in UCSD/AML1 cells is associated with evi-1 transcription and expression of a potential transforming gene. In contrast to c-myc, evi-1 expression is minimally altered by biologically active chemicals or growth factor stimulation.