Bmi is a double-edged sword

Hematopoietic stem cells (HSCs) are permanently renewed in order for hematopoiesis to persist during the lifetime of an animal. In pathologic conditions, self-renewal of a leukemic stem cell population leads to constantly regenerating tumor cells such as those from acute myeloid leukemia. But, the molecular mechanisms that control the self-renewal of either hematopoietic or leukemic stem cells have been unclear. Two papers in the April 20 Nature show that the Polycomb group (PcG) gene Bmi-1 has an essential role in regulating the proliferative activity of both normal and leukemic stem cells.

Julie Lessard and colleagues at the Clinical Research Institute of Montreal used fetal liver derived hematopoietic cells and leukemic stem cells obtained through oncogenic transfer. They observed that the stem cells lacking Bmi-1 did not proliferate and showed signs of differentiation and apoptosis. In addition, they showed that the leukemic stem cells lacking Bmi-1 behaved similarly and could...