Previously, we have shown that CLL B cells exhibit aberrant activation of the canonical Wnt signaling pathway as detected using the TCF/LEF dual luciferase reporter assay, while healthy donor B cells lack activation of this pathway.[5] Because LEF-1 is a central mediator of the Wnt pathway and because differentiation of CLL B cells into ISC resulted in decreased expression of LEF-1, we next evaluated the level of Wnt pathway activation in these cells. The gene discussed is LEF1; the disease is B-cell chronic lymphocytic leukemia.