Loss of receptor activity for mouse erythrocytes precedes tumour promoter-induced maturation of chronic lymphocytic leukaemia cells.

The tumour promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) induced differentiation in lymphocytes from patients with chronic lymphocytic leukaemia (CLL). The differentiation was detected by the appearance of cytoplasmic immunoglobulin (CIg) and a plasmacytoid morphology, and was accompanied by the loss of the ability of the CLL cells to rosette with mouse erythrocytes (M). Loss of M rosetting occurred rapidly (within 10 min), was not prevented by cycloheximide or actinomycin D and was elicited by low concentrations of TPA (ED50 8 X 10(-10) M). Inhibition of rosette formation was induced by other phorbol diester promoters, but not non-promoting derivatives. Loss of the capacity to form M rosettes occurs before events which are evidently related to genome activation.