Antitumor effects of interferon-omega: In vivo therapy of human tumor xenografts in nude mice

The antitumor effect of the type I IFN, IFN-omega, was evaluated in both in vitro and in vivo studies of human cancer. For these studies, the cDNA for human IFN-omega was cloned into a eukaryotic expression plasmid DNA (pDNA) driven by the cytomegalovirus promoter. Supernatants from UM449 cells tran sfected in vitro with IFN-omega pDNA had antiproliferative effects on 11 of 13 human tumor cell lines. For in vivo studies, nude mice mere implanted s .c. with one of the following human tumors: NIH: OVCAR-3 ovarian carcinoma, A375 melanoma, or A431 epidermoid carcinoma. Direct intratumoral injection of 100 mu g of a IFN-omega pDNA DMRIE/DOPE complex (1:1 DNA:DMRIE mass rat io) for 6 consecutive days resulted in a significant reduction in the tumor volume of NIH: OVCAR-3 ovarian carcinoma or A375 melanoma (P = 0.02). IFN- omega pDNA delivered by i.m. injection also had an antitumor effect. Nude m ice bearing s.c. A431 epidermoid carcinoma and injected i.m. with 100 mu g of IFN-omega pDNA, twice per week for 3 weeks, had a significant reduction in tumor volume (P = 0.009). These results demonstrate for the first time t hat IFN-omega can have in vivo antitumor effects in several models of human cancer.