Cells of a human monocytic leukemia cell line (THP-1) synthesize and secrete apolipoprotein E and lipoprotein lipase

A human cell line established from a patient of an acute monocytic leukemia (THP-1) retained an ability to synthesize and secrete plasma apolipoprotein E like protein. The protein was identified with monospecific antibody raised against human plasma apolipoprotein E. The cells also secreted lipoprotein lipase (EC 3.1.1.34). The enzyme was characterized as lipoprotein lipase on the basis of the requirement of apolipoprotein C-II as an activator and the inhibition of its activity by sodium chloride. The secretion of both apolipoprotein E and lipoprotein lipase was markedly enhanced in the process of differentiation into macrophage-like cells by the addition of 4β-phorbol 12β-myristate 13α-acetate.