Isopycnic density-gradient centrifugation: a separation parameter which improves flow cytometric measurements on heterogeneous tumors.

The analytic and prognostic value of flow cytometric measurements can generally be improved by preseparation of cells. The present data demonstrate clearly the distinct character of bands obtained in density-gradient separation. Density-gradient centrifugation in Percoll after extensive Ca2+ + Mg2+ elimination helps to resolve more detail in flow cytometric measurements (e.g., additional DNA stem lines in human tumors) and can be used in studies of tumor heterogeneity. The significance of investigations of tumor heterogeneity is demonstrated by the different reactivity of subpopulations of the experimental murine tumor S 180 to vincristine.