Heterogeneity of tumor cell populations.

Ascites tumor cell populations proved to be heterogeneous with respect to density. Subpopulations separated by isopycnic centrifugation differed from each other in several respects including cell cycle time, chromosome number and distribution and chemotherapeutic sensitivity. The results indicate that density separation is a useful technique to study the behavior of subpopulations within tumor and offers new possibilities in comparative experimental chemotherapy.