Commitment to differentiation of human promyelocytic leukemia cells (HL60): an all-or-none event preceded by reversible losses of self-renewal potential.

A method for clonal analysis has been developed which allows the characterization of the number and type of progeny cells produced by each single cell arising during clonal evolution. The method is based on a symmetry of self-renewal exhibited by sister cells of the human promyelocytic leukemia cell line -HL60-. This permits the use of one of the sister cells to measure the potential for self renewal of the other. Using a system of sequential daughter cell transfers in semisolid medium, we have analysed self-renewal and differentiation in individual clones exposed to all-trans retinoic acid or dimethylsulfoxide (DMSO). We find that in clones exposed to chemical inducers of differentiation commitment occurs as an all-or-none event which is preceded by coordinated but reversible losses of self-renewal potential. It is concluded that the differentiation pathway of HL60 cells has two distinct portions. These are, first, a predeterministic portion, reflected by coordinated but reversible losses of self-renewal potential, and second, a deterministic portion, reflected by irreversible phenotypic differentiation.