Application of radioactive precursors for the evaluation of sensitivity of cancer cells to anticancer drugs.

An in vitro drug sensitivity test was developed to estimate the lethal effects of drugs on cancer cells. Cancer cells were incubated in the presence of radioactive precursors and anticancer drugs. The drug effects were estimated from the changes in rates of incorporation of precursors into DNA, RNA, and protein. A microtiter plate and a multiple automatic cell harvester made feasible handling of a large number of samples. Incorporation of radioactive precursors was well correlated with drug-induced cell lethality. The results of this test were also correlated with in vivo regression of tumors of mice. This test appeared to be more reliable than other similar tests of cell lethality in vitro. For utilization in clinical studies, a test plate was simplified and 25 human cancers were tested. The in vitro results demonstrated a positive correlation with clinical results in 80% of the observations.