Activation of antitumor agent gilvocarcins by visible light.

Gilvocarcins that are antitumor agents are activated by low doses of visible light to induce bacteriophage lambda in Escherichia coli. This result is dependent on interaction with DNA. Gilvocarcin M, an analog without antitumor activity, failed to induce the prophage after light exposure, thus demonstrating a correlation between photosensitizing and antitumor activities. These results raise several possibilities regarding the mode of action of gilvocarcins as antitumor agents in vivo, involving light or enzymatic activating systems, which could be exploited in human cancer therapy.