Measurement of Antitumour Activity of Actinomycin D

SEVERAL antibiotics are being used as antitumour agents because of their cytotoxic activity against both proliferating and non-proliferating cells 1 but the doses of the substances given to patients are largely judged by empirical observations. Clearly it would be more satisfactory if the antitumour activity could be measured in the laboratory. It has already been reported 2 that HeLa cells, normally unable to grow in the mouse, will develop into a rapidly growing tumour if the immune mechanism of the mouse has been suppressed by antilymphocyte serum (ALS). Such an animal may be most useful for measuring the antitumour activity of drugs and the purpose of this report is to describe our early findings.