Tumor response to interferon inducer and radiation effect of serum interferon levels

The effect of interferon inducing complex of polyriboinosinic, polyribocytidylic acid with poly-L-lysine and carboxymethylcellulose - Poly (ICLC) - on the response of Lewis lung carcinoma in C57B1 mice to radiation treatments was studied. Improved tumor response was obtained in mice receiving 1.5 mg/m2 or higher of Poly (ICLC). Such doses have induced more than 1000 mu/ml of serum interferon. The same doses of Poly (ICLC) potentiated the epilation effect of radiation. The injection of 0.15 mg/m2 of Poly (ICLC) led to protection of the tumor and the stimulation of it's growth. It also did not potentiate the epilation effect. In this study, one weekly administration of Poly (ICLC) was as effective as three times per week treatment. The cellular mechanism of the increased radiosensitivity caused by Poly (ICLC) was reflected in the reduction of the width of the shoulder on the cell survival curve, which was dependent on the dose of the drug. In cell cultures, doses of 100 micrograms/ml synchronized the cell division, thus contributing to the increase in radiosensitivity.