Differentiation of the
megakaryocytic leukemia cells, CMK, was induced by long-term (12 day) treatment with the combination of
IL-3 and the
nucleoside analogue
ribavirin (RV), which reduces cellular
GTP levels. In a previous report we demonstrated the induction of early messages and
antigens, as well as the formation of giant
polyploid cells in the cultures (Majumdar et al., 1994, J. Cell. Physiol., 160:29-39). Here we show high level induction of messages for the late markers,
Platelet Factor 4, GMP140 (
P-Selectin),
thrombospondin, and
beta thromboglobulin. The induced cells are also positive for these
antigens by immunocytochemical analysis. The high level message induction resulted from synergy between the inducers. Pretreatment of the cells with
IL-3 could accelerate the rise in message seen with the inducer combination. The increase in
differentiation markers was accompanied by a reduction of the proliferative capacity of the cells. Riboguanosine, which has anti differentiation activity, blocked the induction of early and late
antigens by the inducer combination, and also by
IL-3 acting alone, but did not block the reduction in proliferative competence. In this model of megakaryocytic differentiation
IL-3 treatment yields an initial stimulation of growth followed by growth suppression, and is the principal driver of the differentiation process. RV functions primarily as a stimulator of message and
protein expression in synergy with
IL-3.