The estimation of self-renewal in the clonogenic cells of human solid tumours: a comparison of secondary plating efficiency and colony size.

The in vitro clonogenicity of 25 human tumours was compared in two simple two layer culture systems, agar/agar and liquid medium/agar. There was a strong correlation between the values for clonogenicity obtained in each system. A linear relationship between cells plated and colonies formed was found in both systems. Radiation survival in the liquid culture system was essentially log linear with a small initial shoulder confirming that we were not simply counting clumps. We present a simple method of assessing the self-renewal capability of the clonogenic cells of human solid tumours, based on the liquid/agar two-layer system, which we have used to compare secondary plating efficiency and colony size analysis as measures of self renewal in human transitional cell carcinoma of the bladder.