Increased myeloid-associated enzymes in Epstein-Barr virus nuclear antigen--positive human cell lines exposed to butyric acid in vitro.

Continuous tissue culture lines derived from the bone marrow or peripheral blood of normal humans or patients with leukemia frequently show Epstein-Barr virus nuclear antigen (EBNA) and surface immunoglobulins (SIg), characteristics of transformed B lymphocytes. A survey of myeloid cell-associated enzymes produced by 18 EBNA-positive lines revealed leukocyte alkaline phosphatase (LAP), myeloidesterase (AS-D-chloroacetate substrate specific), or Iysozyme in 14. Several lines showed increasing absolute numbers of LAP and esterase-positive cells with a direct dose-response relationship following exposure in vitro to butyric acid. Multiple clonal sublines gave similar results, arguing that a subpopulation was not being selected by the drug. The LAP substrate specificity of several lines was consistent with a mixture of both myeloid LAP and N-APase (an enzyme hitherto found only in Iymphoid cells) but was entirely myeloid LAP in one. While LAP was also increased by hydrocortisone, exposure to dimethylsulfoxide, dibutryl-cyclic-AMP, or other hormones failed to stimulate enzyme activity. Transfer of tissue culture cells to diffusion chambers intraperitoneally implanted into 750-rad whole-body-irradiated rats also resulted in increased absolute numbers of LAPand esterase-positive cells. Four rat acute myelogenous leukemia lines gave similar results. These studies suggest that some EBNA-positive human cell lines can express gene products associated with myeloid cells following biochemical or humoral stimulation.