Effect of Polyinosinic-Polycytidylic Acid on Induction of Primary or Transplanted Tumors by Chemical Carcinogen or Irradiation

Summary

Prolonged treatment with polyinosinlc-polycytidylic acid (poly I:C), begun 12 hours before administration of carcinogen, increased thymic lymphomas induced by a single neonatal injection of 7,12-dimethylbenz[a]anthracene (DMBA). By 150 days all mice treated with DMBA and poly I : C had died with tumors, whereas at 350 days there was a 50% survival of the mice given injections of DMBA only. However, an identical course of poly I : C treatment significantly reduced the incidence of thymic lymphomas induced by a single neonatal whole-body exposure to 400 rads. Poly I:C treatment reduced the tumor incidence from 94–40%. The effect of prolonged treatment with poly I : C, begun 12 hours before transplantation, on transplanted thymic lymphomas induced by chemical carcinogen varied considerably. Whether an antitumor effect of poly l:C was obtained depended very much on the experimental conditions. The anti-tumor activity of poly I:C treatment was most pronounced when both tumor cells and poly I:C were given intraperitoneally (a 100% survival for 1 year), whereas all control animals had died of progressively growing tumors by 60 days. When poly I:C and tumor cells were given by different routes of injection, life was only slightly prolonged, or in some situations treatment with poly I:C appeared to have a slightly enhancing effect on the number of animals dying with transplanted tumors.