Phorbol ester-induced hairy cell features on chronic lymphocytic leukemia cells in vitro

Leukemic cells from eight patients with chronic lymphocytic leukemia were isolated and cultured in the continuous presence of 12-O-tetradecanoylphorbol 13-acetate (TPA) at a concentration of 1.6 x 10(-9) M for 4-10 days. Aliquots of cells were then analyzed at intervals of 24-72 hr for changes in morphology, acid phosphatase staining (AP), and expression of two hairy cell-associated surface antigens, HCL1 (CD22, Leu 14) and HCL3 (CD11c, Leu M5). All cases studied showed typical B-CLL phenotype, and only a small proportion of cells expressed CD22 and CD11c (mean 7% and 4.9%, respectively). TPA treatment induced the coexpression of CD22 (mean 49%) and CD11c (mean 48%) and tartrate-resistant acid phosphatase in seven of eight cases. Morphologically, cells in TPA cultures expressed hairy cell features that were evident in light and electron microscopic studies. Collectively these changes indicate that TPA can induce hairy cell features on CLL cells in vitro, suggesting the later maturational stage of HCL compared with CLL.