Cellular heterogeneity in human ovarian carcinoma studied by density gradient fractionation.

We have utilized equilibrium density gradient sedimentation to document the cellular heterogeneity existing in tumor cell populations obtained from malignant ascites of 5 patients with serous ovarian carcinoma. The cellular properties defined were density, proliferative status (labelling index), clonogenic potential and accumulation of cytoplasmic fat droplets (oil-red O), and cytoplasmic RNA (methylgreen pyronin). Cells of like properties were found to have similar density in different patients. On the basis of density distributions, two broad populations could be identified: first, non-proliferative, non-clonogenic, differentiated cells of high density, and second, a lower density population showing infrequent evidence of differentiation, but containing all cells identified as proliferative by the labelling index and all cells with clonogenic capacity in agar culture. The data are discussed in terms of the support which they give to the view of human ovarian carcinoma as a stem cell system.