TGF-BETA ACTIVITY AND EXPRESSION OF ITS RECEPTORS IN B-CELL CHRONIC LYMPHOCYTIC-LEUKEMIA

B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemi a in Western countries and results from the accumulation of B-lymphocy tes which are functionally abnormal and predominantly non-cycling in v ivo. Consequently, it is important to understand why B-CLL cells accum ulate in G0 phase. Since TGF-beta is an important negative regulator o f the immune system, a loss of responsiveness to this factor might pro vide a selective advantage to B-CLL cells. Here we review data on the role of TGF-beta in B-CLL. We show that the B-CLL cell response to TGF -beta signals is abnormal in vitro (inhibition of proliferation and in duction of apoptosis). This lack of response of B-CLL cells to TGF-bet a inhibition appears to be accompanied by a decrease or a loss of TGF- beta receptor expression.