The Wilms tumor suppressor WT1 directs stage-specific quiescence and differentiation of human hematopoietic progenitor cells

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Abstract
WT1, a transcription factor implicated in both normal kidney differentiation and tumorigenesis, is also expressed in differentiating hematopoietic progenitors. Most human acute leukemias contain high levels of the wild‐type transcript, while a minority have point mutations, raising the possibility that this tumor suppressor might have a paradoxical oncogenic effect in some hematopoietic cells. Using high titer retroviral infection, we demonstrate that WT1 triggers rapid growth arrest and lineage‐specific differentiation in primary hematopoietic progenitors and differentiation‐competent leukemia cell lines, while it induces cellular quiescence in a primitive subset of primary precursors. Growth arrest by WT1 is associated with induction of p21CIP1, but expression of this cyclin‐dependent kinase inhibitor alone is insufficient for either cellular differentiation or primitive cell preservation. The effects of WT1 are enhanced by co‐expression of its naturally occurring isoforms, and are correlated with the physiological expression pattern of WT1 in vivo. Our observations suggest a role for WT1 in the differentiation of human hematopoietic cells, and provide a functional model that supports its capacity as a tumor suppressor in human acute leukemia.