Selective uptake and retention of anticancer agents by sensitive cells.

Considerable evidence has been accumulated to demonstrate that sensitive tumor cells in experimental animals take up and retain at least some effective anticancer drugs to a greater extent than normal tissues, thus providing a greater degree of exposure and accounting for the selective effect of the drugs. In sensitive cells, DNA synthesis is inhibited for prolonged periods, whereas in cells less sensitive the time of inhibition is shorter. In those cases examined where a metabolite, formed intracellularly, is the active form of the agent, the metabolite is produced and is retained to a greater extent than in normal tissues.