The
antibiotic protein auromomycin (AUR) is composed of a chromophore and an
apoprotein. The in vitro cytotoxic activity of AUR is associated with the chromophore, whereas the
apoprotein is not cytotoxic. Exposure to AUR blocks cell cycle traverse in G2-M phase. Both AUR and the chromophore exhibit antitumor activity against murine
L1210 leukemia, both in vitro and in vivo. Similarly,
neocarzinostatin and its chromophore also show antitumor activity against L1210
tumor cells in vitro and in vivo. AUR and
neocarzinostatin apoproteins have no antitumor activity. The pharmacokinetics of 125I-labeled AUR in L1210
tumor-bearing mice shows a triexponential
drug decay and initial rapid clearance of
drug from the blood. The distribution of AUR-associated radioactivity into various tissues is rapid, and at the end of 24 hr, there is little
drug accumulation in the tissues. During the first hr, greater than 50% of the administered
drug is eliminated in the urine. As the chromophores alone possess antitumor activity, the effect of these antitumor
proteins in
cancer chemotherapy might be significantly increased by the administration of
protein preparations containing biologically active and stable chromophores.