Fig. 1.

Initial studies in leukemia provided the paradigm for the general CSC model. As shown on the left side of the figure, a hematopoietic stem cell (HSC) gives rise to normal progenitors and mature blood cells. The original model suggests that the HSC undergoes mutation(s) that give rise to its malignant counterpart, the leukemia stem cell (LSC). The LSC retains some degree of developmental potential, generating the leukemia progenitor and leukemic blast cells, which differ in their biological properties from the parent LSC. As in normal hematopoiesis, the stem cell maintains the ability to undergo self-renewal and thereby perpetuate the leukemia population.