Proto-oncogene expression during early myeloid differentiation of normal peripheral blood progenitor cells.

Peripheral blood mononuclear cells cultured in liquid medium with fetal calf serum undergo differentiation to myeloblasts (7 days) and then mature granulocytes (14-21 days). This culture system was used to study proto-oncogene expression during pre-myeloblast myeloid differentiation. c-myc mRNA was present in the peripheral blood mononuclear cells placed into culture, fell during the first 2-4 days of culture and then rose between days 2-4 and day 7 of culture, prior to and coincident with the appearance of myeloblasts. Histone H3 mRNA was absent or present at very low levels at initiation of cultures, and then rose throughout the first 7 days of culture. c-fms mRNA was absent at initiation of cultures, and appeared on days 2-5 of culture, prior to the appearance of myeloblasts. c-fos mRNA was not detected during differentiation of peripheral blood mononuclear cells to myeloblasts. Elucidation of patterns of proto-oncogene expression during normal myeloid differentiation is a prerequisite for interpretation of proto-oncogene expression in myeloid leukemia cells.