Purification, Bacterial Expression, and Biological Activities of the Human Interferons

The structural and functional complexity of the human interferon system has become increasingly evident. More than eight different alpha (leukocyte) interferons are expressed in induced human cells in culture. Many of these have been purified by a combination of methods, including high-performance liquid chromatography. Moreover, at least 12 different human leukocyte interferons have been cloned, and several have been efficiently expressed in Escherichia coli and other organisms. The availability of purified species of leukocyte interferon, both natural and recombinant, has allowed structural work to be done, including amino acid sequence determinations, chemical modification studies, and the crystallization of one species. The purified material has also been used for the production of monoclonal antibodies with various specificities that are proving invaluable in rapid assays and purification techniques. Testing of the purified species for their relative potency in antiviral, antiproliferative, and immunomodulatory assays has begun to demonstrate the functional uniqueness and diversity of the purified alpha interferons. Hybrid interferon genes have been synthesized by splicing together parts of various cloned interferon genes. The resulting hybrid proteins have been valuable in establishing structure/function relationships. In several cases, the functional properties of the hybrid protein were novel and unpredicted from the properties of the parental molecules

Interferon-β Signaling Contributes to Ras Transformation

Increasing evidence has pointed to activated type I interferon signaling in tumors. However, the molecular basis for such activation and its role in tumorigenesis remain unclear. In the current studies, we report that activation of type I interferon (IFN) signaling in tumor cells is primarily due to elevated secretion of the type I interferon, IFN-β. Studies in oncogene-transformed cells suggest that oncogenes such as Ras and Src can activate IFN-β signaling. Significantly, elevated IFN-β signaling in Ras-transformed mammary epithelial MCF-10A cells was shown to contribute to Ras transformation as evidenced by morphological changes, anchorage-independent growth, and migratory properties. Our results demonstrate for the first time that the type I IFN, IFN-β, contributes to Ras transformation and support the notion that oncogene-induced cytokines play important roles in oncogene transformation