Application of the interferon minipellet to human renal cell carcinoma in nude mice

Background: The interferon (IFN) minipellet is a sustained-release formulation of human lymphoblastoid IFN, with atelocollagen used as the carrier material. We evaluated the antitumor effect of the IFN minipellet on an established human renal cell carcinoma cell line (KU-2) transplanted in nude mice. Methods: The treatment was started when tumor nodules had grown to 6 to 8 mm in diameter. The IFN minipellet, or an aqueous solution of IFN, was given by subcutaneous injection, or peritumor injection, on days 1 and 10. Antitumor effects were evaluated according to tumor weights calculated as (long diameter) x (short diameter)²/2 in 7 groups consisting of 6 mice each. Results: IFN levels remained detectable in both tumor tissue and serum up to in days after peritumor injection of the IFN minipellet. Administered by the peritumor route, the IFN minipellet inhibited growth of the tumor significantly as compared with tumor growth in the untreated mice. The IFN minipellet showed greater inhibition of tumor growth by peritumor injection compared to subcutaneous injection. The aqueous solution of IFN was not effective either by subcutaneous or by peritumoral injection. Conclusion: Results indicate that the IFN minipellet is useful in the treatment of renal cell carcinoma.