DIFFERENTIATING AGENTS DO NOT INDUCE A TRUE HAIRY-CELL PHENOTYPE IN B-CLL CELLS IN-VITRO

B-Chronic lymphocytic leukemia (B-CLL) and hairy cell leukemia (HCL) a re both differentiated B-cell lymphoproliferative disorders. Prior stu dies have suggested that phorbol esters and the macrocyclic lactone Br yostatin-1, which are both protein kinase-C activators, can induce the differentiation of B-CLL cells into HCL cells in vitro, as evidenced by morphology, phenotype and TRAP activity. The differentiating effect of all-trans retinoic acid on B-CLL cells has been less extensively s tudied. We studied the effects of incubating adherence purified B-CLL cells with phorbol myristic acetate (PMA), all-trans retinoic acid (AT RA), and Bryostatin-1. None of these agents induced a true HCL phenoty pe (CD5-, CD11c/CD25 coexpression) under the conditions studied.