Summary
Polyinosinic-polycytidylic acid administered intraperitoneally inhibits the formation of chemically induced tumors by methylcholanthrene in mice. The experiments show that poly (I∶C) is an effective suppressor of tumor formation when given simultaneously with the cancerogenic compound, or soon thereafter (before 4 weeks). Once the tumorigenesis was started (after 8 weeks), poly (I∶C) treatment becomes ineffective.
The mechanism of inhibition of tumor formation by poly (I∶C) was studied by measuring the immune response of treated mice. Mice treated with methylcholanthrene alone exhibit a 50% inhibition of the immune response towards sheep red blood cells. Animals injected with poly (I∶C) after the methylcholanthrene treatment did not show any significant change. However, a pretreatment with poly (I∶C) causes a complete reversal of immunosuppression caused by methylcholanthrene.
Zusammenfassung
Polyinosin-Polycytidylsäure (Poly I∶C), intraperitoneal verabreicht, hemmt die Bildung von chemisch induzierten Tumoren durch Methylcholanthren in Mäusen. Die Versuche zeigen, daß Poly (I∶C) ein wirksamer Hemmstoff der Tumorbildung ist, wenn es gleichzeitig mit Methylcholanthren oder bald danach (vor Ablauf von 4 Wochen) gegeben wird. Wenn die Tumorgenese einmal begonnen hat (nach 8 Wochen), wird die Poly (I∶C)-Behandlung unwirksam.
Der Hemmungsmechanismus der Tumorbildung durch Poly (I∶C) wurde durch Messung der Immunantwort von behandelten Mäusen untersucht. Nur mit Methylcholanthren behandelte Mäuse zeigen eine 50%ige Hemmung der Immunantwort in Gegenwart von Schaferythrocyten. Behandelt man die Tiere zuerst mit Methylcholanthren und anschließend mit Poly (I∶C), so bleibt die Immunantwort unbeeinflußt. Ändert man diese Reihenfolge, indem das Poly (I∶C) vor Methylcholanthren eingespritzt wird, so wird die immunsuppressive Wirkung des Methylcholanthrens vollkommen aufgehoben.
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P. S. After the submission of our paper we came to know the recent communication of Kreiblich, et al. (G. Kreibich, R. Süss, V. Kinzel and E. Hecker.) Z. Krebsforsch. 74, 383 (1970), reporting a decrease in tumor yields by poly (I∶C) administered during initiation of skin by an intragastric dose of 7,12-Dimethyl-benz[a]anthracene.
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Chandra, P., Gericke, D. & Wacker, A. Effect of polyinosinic-polycytidylic acid on chemically induced tumorigenesis by methylcholanthrene in mice. Z. Krebsforsch. 76, 40–44 (1971). https://doi.org/10.1007/BF00304285
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DOI: https://doi.org/10.1007/BF00304285