Differentiation of isotope-labeled myeloid leukemia cells free in the peritoneal cavity of syngeneic mice.

Ml cells were labeled in vitro with [3H]thymidine and injected into the peritoneal cavity of syngeneic mice. After several days the peritoneal cells were harvested and [3H]labeled cells were determined by autoradiography. The inoculated isotope-labeled Ml cells differentiated in the peritoneal cavity and lipopolysaccharide, an inducer of cell differentiation, significantly stimulated differentiation. These results provide direct evidence that Ml cells can be induced to differentiate in vivo under conditions in which leukemia can develop.