Direct synchronization of cells from solid tumors by centrifugal elutriation

Cells from 9L/Ro, KHT, and EMT6/Ro solid tumors were separated into relatively homogeneous sized populations by centrifugal elutriation using a modified long collection procedure. This modification substantially improved the volume distributions of cells isolated from these solid tumors. More than 90% of the host cells were removed before the tumor cells were separated according to their sedimentation velocities into subpopulations at different stages of the cell cycle. Analysis of the DNA content of these subpopulations by flow cytometry indicated that the degree of synchrony after elutriation could be as high as ⩾92% for G1 cells, 70–75% for S cells, and ⩾70% for G2 cells for some of these tumors. Similar results were obtained by autoradiography. Nevertheless, the recovery in these fractions was often low, varying from 0.3 to 10% of the total number of cells elutriated. The colony-forming efficiency of cells from different phases of the cell cycle remained constant and was always higher than that of unseparated tumor cells, because there were few host cells in the separated populations.