A soft agar colony assay for Lewis lung tumour and B16 melanoma taken directly from the mouse.

A soft agar colony assay has been developed for the B16 mouse melanoma and the Lewis lung tumour. The special features of the technique are the use of a gas phase with 5% O2 instead of air and the addition of rat red blood cells. Single cell suspensions are prepared by trypsinization from the solid tumour and the cells are plated out in 0-3% agar over a layer of 0-5% agar in 30-mm Petri dishes. After 8 to 15 days' incubation in 5% O2, colonies of more than 50 cells are produced. Plating efficiencies of between 30 and 50% are usually obtained. The addition of up to 10(4) heavily irradiated tumour cells gives some further improvement in plating efficiency for the B16 melanoma but not for the Lewis lung tumour. Applications of the technique to measure cell survival in the two tumours after treatment with cytotoxic drugs and radiation are reported. The scatter of experimental points is relatively small, and in comparative experiments good agreement has been obtained with results using in vivo assay techniques.