Expression of the apolipoprotein C-II gene during myelomonocytic differentiation of human leukemic cells

Apolipoprotein C-II (apoC-II), which is known to activate lipoprotein lipas e (LPL), was identified by ordered differential display (ODD)polymerase cha in reaction (PCR) as a cDNA fragment exhibiting a distinct increase in expr ession during 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced differenti ation of promonocytic U937 cells into monocytes and macrophages. The amount of apoC-II mRNA expression detectable in U937 cells significantly increase d and reached a maximum 24-48 h after treatment with 32 nM TPA, apoC-II mRN A was also detected in monocytic THP-1 cells but was not detected in promye locytic HL-60 cells. In healthy human tissues, the most significant express ion of apoC-II mRNA was in the liver. Although apoC-II mRNA expression was markedly up-regulated during the induced differentiation of HL-60 cells int o monocytes and macrophages with 32 nM TPA, such expression was not induced during the differentiation of HL-60 cells into granulocytes with 1.25% dim ethyl sulfoxide, These results suggest that human apoC-II expression is ind uced at the transcription level during myelomonocytic differentiation and m ay confer an important role to macrophages involved in normal lipid metabol ism and atherosclerosis.