Granulocyte differentiation by Friend leukemia cells.

Friend leukemia cells growing in suspension culture are thought to represent a population of primitive erythroid cells which have undergone malignant transformation. We have found that when growing in vivo or in plasma clots in vitro, these suspension culture cells can exhibit morphologic and enzymatic properties which are characteristic of primitive granulocytic cells. The microenvironment in which the tumor cells grow plays a major role in determining the direction of differentiation of these leukemia cells. Hence it appears likely that the Friend cell is in fact a neoplastic pluripotent hematopoietic stem cell.