Tunicamycin, an antibiotic which specifically inhibits the dolichol-mediated synthesis of glycoproteins, significantly decreased the incorporation of tritiated d-mannose and d-glucosamine into L1210 ascites leukemia cell glycoproteins at concentrations which affected the biosynthesis of proteins minimally. Mice receiving inoculations of L1210 cells pretreated with 10 µm tunicamycin in vitro survived nearly twice as long as did mice receiving implants of untreated tumor cells. A nonlethal dose of X-irradiation (350 rads) to mice 24 hr prior to receiving their inoculation of tunicamycin-treated L1210 cells prevented this increase in life span. Thirty-eight % of the long-term surviving mice which received 1 × 105 L1210 cells pretreated with 10 µm tunicamycin in vitro were then resistant to a subsequent challenge with 106 untreated L1210 ascites cells. Direct i.p. administration of tunicamycin to mice resulted in potent liver toxicity (50% lethal dose, 2.0 mg/kg) which obviated any therapeutic efficacy when administered to L1210 ascites tumor-bearing mice. The administration of nontoxic levels of d-mannose prior to the administration of tunicamycin decreased the toxicity of the antibiotic in vivo and, when combined with d-mannose in vitro, exhibited cytotoxic additivity in terms of the inhibition of L1210 leukemic cell growth. A therapeutic regimen incorporating a 24-hr infusion of the sugar prior to multiple administrations of tunicamycin gave evidence of a small therapeutic response in terms of the survival of tumor-bearing mice. These results suggest that tunicamycin, an inhibitor of glycoprotein biosynthesis, might be able to alter tumor cell growth and immunogenicity provided that host liver toxicity is diminished.

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Supported in part by Grant CA 13038 from the National Cancer Institute, NIH, and Institutional Grant IN54U8 from the American Cancer Society.

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