Purified B-cells from normal tonsils and from the peripheral blood of eight patients with B-chronic lymphocytic leukemia (B-CLL) were treated in vitro with the protein kinase C (PKC) activators TPA, Bryostatin 1 (Bryo), mezerein, with the calcium ionophore A23187, and with the cytokines interleukin-1/2, interferon-alpha/gamma, tumor necrosis factor. The induction of the lysosomal enzyme tartrate-resistant acid phosphatase (TRAP) was examined at the RNA (by Northern blotting analysis) and the protein level (by isoelectric focusing). TRAP mRNA and protein were induced by treatment with PKC activators while the combination of PKC stimulator and calcium ionophore was not effective, TRAP mRNA was detected as early as 2 hours after initiation of the culture. This induction of positivity for TRAP which is the enzymatic hallmark of hairy cell leukemia (HCL) by TPA or Bryo is consistent with the previously reported acquisition of HCL-type cellular features in TPA-driven CLL cells; CLL cells exposed to the double stimulus of TPA or Bryo + A23187 have previously been described to differentiate to plasmacytoid cells which is in accord with their remaining TRAP negative. The present data provide evidence that 1) B-CLL cells can be induced by direct stimulation of PKC to convert to HCL-type cells; 2) TPA/Bryo-exposed B-CLL cells display phenotypes different from those of cells treated with combinations containing calcium ionophore; 3) the phosphoinositol signal transduction pathway distal to PKC can be activated effectively in B-CLL cells; 4) Bryo, a new natural PKC activator, induces responses in CLL similar to those caused by TPA; 5) TRAP is an inducible indicator of cellular activation. These observations provide support for the idea that HCL and HCL-like cells might differentiate along a separate branch of B-cell lineage and might represent mature "activation end stage" cells.
Keywords: B-CLL; Isoenzyme; TRAP; induced differentiation.