Antitumor Effects of an Interferon-Loaded Silicone Formulation in Human Renal Cell Carcinoma in Nude Mice

Abstract

Conventional therapy for renal cell carcinoma using interferon (IFN) has shown limited antitumor action. The IFN-loaded silicone formulation (IFN-SF) is a sustained-release formulation of human lymphoblastoid IFN, with a medical grade silicone elastomer used as the carrier material. We evaluated the antitumor effect of IFN-SF on human renal cell carcinoma cell line (KU-2) transplanted to nude mice. The treatment was started when the tumor nodules had grown 6 to 8 mm in diameter. IFN-SF, or an aqueous solution of IFN, was given by subcutaneous or peritumoral injection. Antitumor effects were evaluated according to tumor weights calculated as (long diameter)×(short diameter)²/2 in 7 groups consisting of 6 mice each. Serum IFN levels remained detectable up to 30 days after subcutaneous injection of IFN-SF. IFN-SF administered by the subcutaneous and peritumor route significantly inhibited growth of the tumor when compared with tumor growth in the untreated mice and mice treated with aqueous IFN solution. IFN-SF had equivalent inhibitory effects on tumor growth by peritumor and subcutaneous injection. Results indicated that the use of IFN-SF could reduce the frequency of injections and provide better treatment of patients with renal cell carcinoma because of its long-acting effect when it is used systemically.