Correlation Between Interferon Alpha Receptor Protein Expression and Sensitivity to Interferon Alpha Subtypes in Human Renal Carcinoma Cell Lines

Background: We have previously characterized the antitumor activities and immunological properties of interferon-alpha (IFN-·) subtypes on renal cell carcinoma (RCC). However, the mechanism responsible for the different biologic activities among the IFN-· subtypes is still unclear. To explain the different cellular sensitivities to IFN-· subtypes, detailed expression of the interferon-alpha receptor (IFNAR)- 1 and IFNAR-2 subunits on different RCC cell lines was examined and compared with sensitivity of the cell lines to the IFN-· subtypes. Materials and Methods: We investigated the antiproliferative effects of natural IFN-· subtypes (IFN-·2 and IFN-·8) using eight RCC cell lines. IFNAR-1 and IFNAR-2 expression were determined by RT-PCR and Western blotting. To determine a possible relationship between IFN activity and IFNAR expression, the correlation between the 50% effective IFN dose (ED50) for growth inhibition and the level of IFNAR expression was statistically examined. Results: We report here that IFN-·8 more potently induced growth inhibition than IFN-·2 in the majority of the RCC cell lines examined, this being in accordance with our previous results. The ED50 value of IFN-·8 was lower than 1000 (IU/ml) in six of the eight cell lines, whereas that of IFN-·2 was lower than 1000 (IU/ml) in three of the eight cell lines. The results of experiments using Western blotting analysis revealed that IFN-· subtype sensitivities were closely correlated with the expression level of IFNAR-2(c), a long form of the IFNAR-2 protein, in seven of the eight cell lines. Conclusion: These results suggest that the intensity of IFNAR-2(c) protein expression could be an important prognostic marker for clinical application of particular IFN-· subtypes in RCC.