An appraisal of in vivo assays of excised tumours.

Three in vivo assays of excised tumours are compared, the endpoint dilution assay, the tumour latency assay and the lung colony assay. The assay procedures are discussed in 2 phases; the preparation of the required cell suspension and the injection and growth of the tumour cells in recipients. Factors reviewed include those affecting recovery of cells during the suspension procedure, the variability of tumour response, the importance of the site of injection, the effect of heavily irradiated cells and non-lethal effects of radiation. Specific aspects of the lung colony assays are also described. Results of an experiment to compare the 3 assay procedures with that of an in vitro agar colony assay are presented and indicate reasonable agreement for the KHT sarcoma except perhaps for the latency assay at low levels of survival. A list of recommendations of ways to minimize some of the potential problems and a comparison of assay procedures is presented.