The Combination of IFN- α 2 and IFN- α 8 Exhibits Synergistic Antiproliferative Activity on Renal Cell Carcinoma (RCC) Cell Lines Through Increased Binding Affinity for IFNAR-2

Abstract

Although there are at least 13 interferon-α (IFN-α) subtypes in humans, interactions between the subtypes remain unknown. To understand IFN-α interactions, we examined the antiproliferative activities and the receptor binding affinities of different combinations of IFN-α2 and IFN-α8 using six renal cell carcinoma (RCC) cell lines. Although IFN-α8 was the more potent subtype, synergistic and antagonistic antiproliferative effects were also observed in certain combinations of IFN-α2 and IFN-α8. To analyze the interactions between IFN-α2 and IFN-α8, the receptor-binding kinetics of different combinations of IFN-α2 and IFN- α8 to the IFN-α receptors, IFNAR-1 or IFNAR-2, were measured using a surface plasmon resonance-based biosensor. Unexpectedly, the receptor binding kinetics to IFNAR-2 but not to IFNAR-1 were mutually related to antiproliferative activity and increase in the binding speed (K _a ) for IFNAR-2. Moreover, we observed the increased fluorescence intensity (FI) of biotin-labeled IFN-α8 to IFNAR-2 by receptor binding inhibition assay with unlabeled IFN-α2 but not the other combinations. These findings indicate that the binding manner of IFN-α8 for IFNAR-2 is different from that of IFN-α2, suggesting that binding of IFN-α8 rather than binding of IFN-α2 to IFNAR-2 leads to activation and subsequent antiproliferative activity despite the same antiviral activity in RCC.