Patterns of gene expression during plasmacytoid differentiation of chronic lymphocytic leukaemia cells.

Chronic lymphocytic leukaemia (CLL) cells may be induced to undergo plasmacytoid differentiation in vitro in response to 12-O-tetradecanoyl phorbol acetate (TPA). We show here that plasmacytoid differentiation and the accompanying accumulation of Cmu immunoglobulin mRNA are preceded by a rapid transient increase in the expression of the proto-oncogenes, c-myc and c-fos. In terminally differentiated cells the level of c-fos mRNA returned to the original basal level whilst c-myc expression remained appreciably higher than in undifferentiated CLL cells. These data support a possible role for c-fos and c-myc in the programmed chain of events that occur during terminal differentiation of B-lymphocytes.